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NASA Conference Publication 3129

Fourth Symposium on

Chemical Evolution

and the Origin and

Evolution of Life

Edited by

Robert A. Wharton, Jr.

National Aeronautics and Space Administration

Washington, D.C.

Dale T. Andersen

Lockheed Engineering & Sciences Company

Washington, D.C.

Sara E. Bzik

Ames Research Center

Moffett Field, California

John D. Rummel

National Aeronautics and Space Administration

Washington, D.C.

Proceedings of a symposium held at

NASA Ames Research Center

Moffett Field, California

July 24-27, 1990

National Aeronautics and

Space Administration

Office of Management

Scientific and Technical

Information Program

1991

FOURTH SYMPOSIUM ON CHEMICAL EVOLUTION AND THE ORIGIN

AND EVOLUTION OF LIFE

July 24-27, 1990

NASA Ames Research Center, Moffett Field, CA

Sponsored by

National Aeronautics and Space Administration

Life Sciences Division

Symposium Organizer: Robert A. Wharton

NASA Headquarters

Washington, D. C.

Coordinators:

Dale T. Andersen

Lockheed Engineering & Sciences Company

Washington, D. C.

Sara E. Bzik

NASA Ames Research Center

Moffett Field, CA

Exobiology Program Manager: John D. Rummel

NASA Headquarters

Washington, D. C.

Table of Contents

Page

Preface .................................................................................................................... 1

Session Schedule ................................................................................................ 2

Abstracts

Session I:

Session I1:

Session !11:

Session IV:

Session V:

Session VI:

Session VII:

Cosmic Evolution of Biogenic Compounds ................................ 12

Solar System Exploration I .......................................................... 21

Prebiotic Evolution ......................................................................... 32

Early Evolution of Life ................................................................... 56

Evolution of Advanced Life ........................................................... 77

SETI ................................................................................................. 85

Solar System Exploration II........................................................ 93

Poster Session .................................................................................................... 102

Author Index ......................................................................................................... 113

Appendix - List of Attendees ............................................................................. 115

iii

PRECED|NG PAGE BLA?_K t_O"i' FILMED

Preface

This report contains session summaries and abstracts from the Fourth Symposium

on Chemical Evolution and the Origin and Evolution of Life, organized on

behalf of NASA's Exobiology Program and held July 24-27, 1990 at NASA's Ames

Research Center, Moffett Field, California.

The Symposium provided an opportunity for NASA Exobiology principal investigators

to present their most recent research in a scientific meeting forum. In addition, the

symposium helped foster increased communication across disciplinary lines,

formulate a more integrated program approach, review progress in all tasks, and

increase visibility of the Exobiology Program. The goal of NASA's Exobiology

Program is to understand the origin, evolution, and distribution of life in the universe.

The Exobiology Program is therefore quite broad in scope and subject areas covered

during the Symposium included: Cosmic Evolution of the Biogenic Compounds,

Prebiotic Evolution, Early Evolution of Life, Evolution of Advanced Life, Solar System

Exploration, and the Search for Extraterrestrial Intelligence.

The more than 200 participants included Exobiology grantees, NASA Ames Research

Center staff, graduate students and invited guests. Current plans are to continue to

schedule this symposium every three years.

Further information about NASA's Exobiology Program can be found in the annual

"Life Sciences Accomplishments Document," obtainable from the NASA Headquarters

Life Sciences Division.

Robert A. Wharton, Jr.

Life Sciences Division

NASA Headquarters

Fourth Symposium on Chemical Evolution

and the Origin and Evolution of Life

July 24-27, 1990

NASA Ames Research Center, Moffett Field,

N201, Main Auditorium

Session Schedul_

Speakers are indicated with an asterisk.

Tuesday. July 24. 1990

9:00 AM Welcome

9:10 AM

9:15 AM

Session I:

California

Dave Mordson and Dale Compton

Announcements

Robert Wharton

State of Exobiology

John D. Rummel

Cosmic Evolution of Biogenic Compounds

Chairman: Ted E. Bunch

9:40 AM "The Chemistry of Dense Interstellar Clouds"

W.M. Irvine*

10:00 AM "Theoretical Studies of the Extraterrestrial Chemistry

of Biogenic Elements and Compounds"

D.J. DeFrees*

10:20 AM Coffee Break

10:40 AM "Measurement of the Spectral Signature of Small

Carbon Clusters at Near and Far Infrared Wavelengths"

J.Tarter* and R. Saykally

11:00 AM "Laboratory and Observational Study of the Interrelation of

the Carbonaceous Component of Interstellar Dust and

Solar System Materials"

L.J. Allamandola*, S.A. Sanford, W.A. Schutte and A.G.GM.

Tielens

11:20 AM "Quantification of UV Simulated Ice Chemistry: CO and

CO2"

V.G. Anidch °, T. Arakelian and M.S. Hanner

3 PRECEDING PAGE BLA;'_K r_OT F!Lfv'iED
11:40 AM

12:00 noon

12:20 PM

"Volatiles in Interplanetary Dust Particles and Aerogels"

E.K. Gibson, Jr.* and C.P. Harmetz

"Isotopic Composition of Murchison Organic Compounds:

Intramolecular Carbon Isotope Fractionation of Acetic Acid.

Simulation Studies of Cosmochemical Organic Synthesis"

G.U. Yuen*, J.R. Cronin, N.E. Blair, D.J. Des Marals and S.

Chang

Lunch

Chairman:

2:00 PM

2:20 PM

2:40 PM

3:00 PM

3:20 PM

3:40 PM

4:00 PM

4:20 PM

4:40 PM

Session Ih Solar System Exploration I

Rocco L. Mancinelli

"Intact Capture of Cosmic Dust"

P. Tsou*

"Exobiological Implications of Dust Aggregation in

Planetary Atmospheres: An Experiment for the Gas-Grain

Simulation Facility"

J.L Huntington*, J.R. Marshall and D.F. Schwartz

"Stable Carbon Isotope Measurements Using Laser

Spectroscopy"

T.B. Sauke* and J.F. Becker

Coffee Break

"Paleolakes and Life on Early Mars"

M.A. Meyer, R.A. Wharton, Jr.* and C.P. McKay

"Subsurface Microbial Habitats on Mars"

P.J. Boston* and C.P. McKay

"Paleobiomarkers and Defining Exobiology Experiments for

Future Mars Experiments"

R.L. Mancinelli*, L.J. Rothschild and MR. White

"Conceptual Designs for In Situ Analysis of Mars Soil"

C.P. McKay, A.P. Zent* and H. Hartman

"Spectroscopy and Reactivity of Mineral Analogs of the

Martian Soil"

A. Banin, J. Orenberg* and T. Roush

4
5:00 PM "Midinfrared Spectral Investigations of Carbonates:

Analysis of Remotely Sensed Data"

T. Roush°, J.B. Pollack and C.P. McKay

5:20 PM Adjourn

8:00 PM Special Session: The Space Exploration Initiative

Matthew Golombek and John D. Rummel

Wednesday. July 25. 1990

Session II1: Prebiotic Evolution

Co-Chairmen: Sherwood Chang/Robert MacEIroy

8:30 AM "Isotopic Constraints on the Origin of Meteoritic Organic

Matter"

J.F. Kerndge*

8:50 AM "Kinetic Conversion of CO to CH4 in the Solar System"

Y.L. Yung*, M. Allen and J.P. Pinto

9:10 AM "Production of Organic Compounds in Plasmas: A

Comparison Among Electric Sparks, Laser-Induced

Plasmas and UV Light"

T.W. Scattergood*, C.P. McKay, W.J. BoruckJ, L.P. Giver, H. Van

Ghyseghem, J.E. Pards and S.L. Miller

9:30 AM "Organic Synthesis in the Outer Solar System: Recent

Laboratory Simulations for Titan, the Jovian Planets, Triton

and Comets"

c. Sagan*, W.R. Thompson, B.N. Khare and C.F. Chyba

9:50 AM Coffee Break

10:10 AM "Photochemical Reactions of Cyanoacetylene and

Dicyanoacetylene: Possible Processes in Titan's

Atmosphere"

j.P. Ferris* and J.C. Guillemin

10:30 AM "Controlled Evolution of an RNA Enzyme"

G.F. Joyce*

10:50 AM "Sources and Geochemical Evolution of Cyanide and

Formaldehyde"

G. Arrhenius*

5
11:10 AM

11:30 AM

Co-Chairmen:

1:00 PM

1:20 PM

1:40 PM

2:00 PM

2:20 PM

2:40 PM

3:00 PM

3:20 PM

3:40 PM

"Kaolinite-Catalyzed Air Oxidation of Hydrazine:

Considerations of Several Compositional, Structural and

Energetic Factors in Surface Activation"

L.Coyne*, R. Mariner and A. Rice

Lunch

Robert MacEIroy/Sherwood Chang

"Terrestrial Production vs. Extraterrestrial Delivery of

Prebiotic Organics to the Early Earth"

C.F. Chyba*, C. Sagan, P.J. Thomas, L. Brookshaw

"Self Assembly Properties of Primitive Organic

Compounds"

D.W. Deamer*

"Structure and Functions of Water-Membrane Interfaces

and their Role in Proto-Biological Evolution"

A. Pohorille*, M. Wilson and R. MacEIroy

"Macromolecular Recognition: Structural Aspects of the

Origin of the Genetic System"

R. Rein*, D. Barak, N. Luo, T. J. Zielinski and M.Shibata

"Template Polymerization of Nucleotide Analogues"

L.E. Orgel °

"Product and Rate Determinations with Chemically

Activated Nucleotides in the Presence of Various Prebiotic

Materials, Including Other Mono- and Polynucleotides"

A. Kanavarioti*, D.J. Alberas, M.T. Rosenbach, C.F. Bemasconi

and S. Chang

Coffee Break

"Carbohydrates as a Source of Energy and Matter for the

Origin of Ufe"

A.L. Weber*

"On the Origin and Early Evolution of Biological Catalysis

and Other Studies on Chemical Evolution"

J. Oro* and A. Lazcano

6
4:00 PM "Chemistry of Aminoacylation of 5'-Amp and the Origin of

Protein Synthesis"

J.C. Lacey, Jr."

4:20 PM "Catalytic RNA and Synthesis of the Peptide Bond"

D.A. Usher*, M. Kozlowski and X. Zou

4:40 PM "New Evidence for a Dramatic Rise in Atmosphere Oxygen

ca. 1,900 M.Y. Ago"

H.D. Holland* and A.D. Macfarlane

5:00 PM "Biospheric-Atmospheric Coupling on the Early Earth"

J.S. Levine*

5:20 PM "A Window in Time for the First Evolutionary Radiation"

H.J. Morowitz*

5:40 PM Adjourn

6:00 PM Poster Session/Reception

Location: Ames Research Center Cafeteria

Thursday, July 26, 1990

Session IV: Early Evolution of Life

Co-Chairmen: Lawrence I. Hochstein/David J. Des Marais

8:30 AM

8:50 AM

9:10 AM

9:30 AM

9:50 AM

"The Effects of Oxygen on the Evolution of Microbial

Membranes"

L.L. Jahnke*

"On the Chimerical Nature of the Membrane-Bound ATPase

from Halobaqterium $_ccharovorum"

L. I. Hochstein*

"Archaebacterial Rhodopsin Sequences: Implications for

Evolution"

J.K. Lanyi*

"Thioredoxin and Evolution"

B.B. Buchanan*

Coffee Break
r

10:30 AM

10:50 AM

11 "10 AM

11:30 AM

Co-Chairman:

1:00 PM

1:20 PM

1:40 PM

2:00 PM

2:20 PM

2:40 PM

3:00 PM

3:20 PM

3:40 PM

"Exploration of RNA Structure Spaces"

G. Fox*

"Functional Characteristics of the Calcium Modulated

Proteins Seen from an Evolutionary Perspective"

R.H. Kretsinger*, S. Nakayama and N.D. Moncrief

"Photosynthetic Reaction Center Complexes from

Heliobacteria"

J.T. Trost, W.F.J. Vermaas and R.E. Blankenship*

Lunch

David J. Des Marais/Lawrence I. Hochstein

"Molecular Bases for Unity and Diversity in Organic

Evolution"

S.W. Fox*, P. Ruecknagel and G. Braunitzer

"Sedimentary Organic Molecules: Origins and Information

Content"

JM. Hayes* and K.H. Freeman

"Early Archean Stromatolites: Paleoenvironments Setting

and Controls on Formation"

D.R. Lowe*

"Early Archean (~3.4Ga) Prokaryotic Filaments from Cherts

of the Apex Basalt, Western Australia: the Oldest Cellularly

Preserved Microfossils Now Known"

J.W. Schopf*

"The Environmental Distribution of Late Proterozoic Organisms"

A. Knoll*

"The Biogeochemistry of Microbial Mats, Stromatolites, and

the Ancient Biosphere"

D.J. Des MaraJs* and D.E. Canfield

Coffee Break

"Symbiosis and the Origin of Eukaryotic Motility"

L. Margulis" and G. Hinkle

"Is CO2 Capable of Keeping Early Mars Warm?"

J.F. Kasting*

8
4:00

4:20

PM

PM

4:40 PM

"Nonmarine Stromatolites and the Search for Early Life on

Mars"

S.M. Awramik*

"Endolithic Microbial Model for Martian Exobiology:

Road to Extinction"

E.I. Friedmann and R. Ocampo-Fdedmann*

"The NASA Planetary Biology Internship Experience"

5:00 Adjourn

6:30 PM Banquet

Location:

Guest Speaker: Carl Sagan

Friday. July 27, 1990

Chairman:

8:30 AM

G. Hinkle° and L. Margulis

8:50 AM

9:10 AM

9:30 AM

the

9:50 AM Coffee

Garden Alameda Restaurant

"A Small, Blue Dot"

Session V:

John Billingham

Evolution of Advanced Life

"Fine Structure of the Late Eocene Ir Anomaly in Marine

Sediments"

F. Asaro*

"1) Cumulative Frequency Distribution of Past Species

Extinctions

2) Geography of Cretaceous Extinctions: Data Base

Development"

D.M. Raup*

"The Fossil Record of Evolution: Data on Diversification

and Extinction"

J.J. Sepkoski, Jr.*

"Biogeochemical Modeling at Mass Extinction Boundaries"

M.R. Rampino* and K.G. Caldeira

Break

9
Session Vl: SETI

Chairman" Jill Tarter

10:10 AM "The NASA SETI Program"

J. Billingham* and D. H. Brocker

10:30 AM "NASA-SETI Microwave Observing Project - Targeted

Search Element"

LoD. Webster*

10:50 AM "NASA SETI Microwave Observing Project - Sky Survey

Element"

M.J. Klein*

11:10 AM "The SERENDIP II SETI Project: Current Status"

C.S. Bowyer*, D. Wertheimer, C. Donnelly, W. Herrick and M.

Lampton

11:30 AM "Reoptimization of the Ohio State University Radio

Telescope for the NASA SETI Program"

R.S. Dixon*

11:50 AM "A Directed Search for Extraterrestrial Laser"

Signals"

A. Betz

12:10 PM Lunch

Session VII: Solar System Exploration II

Chairman: Glenn C. Carle

1:20 PM "Planetary Protection Issues and Human Exploration of

Mars"

D.L. DeVincenzi*

1:40 PM "Analysis of Images Obtained by the Phobos 2 Spacecraft"

W.M. Irvine*

2:00 PM "Titan Aerosol and Gas Experiment for the Huygens Probe"

G.C. Carle*, A. Bar-Nun, M.J. Cohen, J.P. Ferds, J.M.

Greenberg, D.R. Kojiro, V. Oberbeck, B.J. O'Hara, J.B.

Pollack, T.W. Scattergood and J. Valentin

10
2:20

2:40

3:0O

3:20

3:40

PM

PM

PM

PM

PM

"Analysis of Model Titan Atmospheric Components Using

Ion Mobility Spectrometry"

D.R. Kojiro*, M.J. Cohen, D.E. Humphry, N. Takeuchi, R.F.

Wemlund, and R.M. Stimac

"A Silicone Column for GC Analysis of Polar and Nonpolar

Chemicals"

T.C. Shen*

"Gas Chromatographic Concepts for the Analysis of

Planetary Atmospheres"

J.R. Valentin*, K.W. Hall, R.L. Krekorian, D.K. Cullers and J.B.

Phillips

"The Relative Importance of Prebiotic Synthesis on the

Earth and Input from Comets and Meteorites"

S.L. Miller*

Adjourn

11
Poster Session

Wednesday, July 25, 1990

6:00 PM - 8:00 PM

Ames Research Center Cafeteria

Preserlted Abstracts

"Life On Ice: Antarctica and Mars" (Video Presentation)

D. Andersen, C. McKay, R. Wharton, J. Rummel, C. Sagan, S. Squyres and G. Simmons

"Identification and Characterization of Extraterrestrial Non-Chondritic

Interplanetary Dust"

D. Blake and R. Fleming

"LDEF Post-Retrieval Analysis in Terms of Exobiology Interests"

T. Bunch, F. Radicatl di Brozolo, and R. Fitzgerald

"Recent Spectroscopic Findings Concerning Clay/Water Interactions at Low

Humidity: Possible Applications to Models of Martian Surface Reactivity"

L. Coyne, Jo Bishop, L. Howard and T. Scattergood

"Crystal-Field-Driven Redox Reactions: How Common Minerals Split H20 and

CO 2 into Reduced H 2 and C Plus Oxygen"

F. Freund, F. Battlo, R. LeRoy, S. Lersky, M. Masuda, and S. Chang

"Kinetics of the Template-Directed Oligomerozation of Guanosine 5'-Phosphate

-2-Methylimidazolide: Effect of Temperature on Individual Steps of Reaction"

A. Kanavarioti, C. Bernasconi, and D. Alberas

"Macromolecular Recognition: Structural Aspects of the Origin of the Genetic

System"

R. Rein, A. Sokalski, D. Barak, N. Luo, T. Zielenski, and M. Shibuta

"The 2.5 - 5.0 Micron Spectra of IO: Evidence for H2S and H20 Frozen in Solid

SO2"

Fo Salama, L. Allamandola, F. Witteborn, D. Cruikshank, S.Sanford and J. Bregman

"Laboratory Simulation of the Photoprocessing and Warm-Up of Cometary and

Pre-Cometary Ices: Production of Complex Organic Molecules"

W. Schutte, L. Allamandola and S. Sanford

"Biologically Controlled Minerals as Potential Indicators of Life"

D. Schwartz, R. Mandnelli, and E. Kaneshiro

"Photosynthetic Reaction Center Complexes from Heliobacteria"

J. Trost, W. Verrnaas, and R. Blankenship

12
 F.8_SJ_OJ J

COSMIC EVOLUTION OF

BIOGENIC COMPOUNDS

Chairman - T.E. Bunch

Session ! consisted of seven papers whose subject material spanned the cosmos from

interstellar cloud molecular chemistry to organic compounds found in carbonaceous

chondrites.

W. Irvine opened the session with a study of molecular species and their evolution in

the environment of interstellar clouds, regions that are the formation sites of stars and,

presumably, planetary systems. His recent studies involved the identification of C4Si,

a new carbon chain molecule, astronomically observed in the expelled envelope of an

evolved star. This molecule may have formed from the reaction of Si+ with acetylene

and/or aceylene derivatives. His research of cold, dark interstellar clouds has

revealed the existence of H2S, NO, and formic acid. The H2S abundance may suggest

the importance of grain surface synthesis. The observed ratio of ortho- to parathioformaldehyde, which differs from the theoretical ratio (formed under chemical

equilibrium), may suggest efficient interchange between cold dust grains and the gas

phase.

Recent advances in the theoretical studies of interstellar molecules by computer were

given by D. Defrees. Molecular structure reaction pathways were investigated by

using vibrational frequency, molecular property and reaction energy constraints.

These were applied to determine spectroscopic constants of candidate interstellar

molecules. Accurate predictions of rotational constants and dipole moments of longchain carbon molecules, HC13N, HClSN, and C50, have been made to aid in

determining the size limit of gas-phase interstellar molecules.

R. Saykally and J. Tarter discussed the construction and early results of the new nearto far-IR laser magnetic resonance spectrometer. This instrument was constructed to

produce, detect, and characterize carbon cluster spectra. Carbon clusters may

account for a large percentage of the circumstellar and interstellar carbon molecular

inventory and their relationship to the formation of polycyclic aromatic hydrocarbons

(PAHs) may be significant. The technique involves laser evaporation of a graphite

target. The resulting clusters are cooled and fed into a spectrometer chamber and

resolved at the (near-and) far-IR wavelengths. The technique is a necessary step

before carbon clusters can be correctly interpreted in IR spectra taken of the interstellar

medium (ISM).

L. Allamandola and colleagues, who are largely responsible for recognizing the

importance of and the possible connection of interstellar PAHs to solar system carbon

chemistry, reported the results of their success with direct comparsions of astronomic

IR spectra of icy objects (ISM grains, comets, and outer planets and satellites) to

laboratory analogs. These primordial ices and accompaning complex organics may

be preserved in comets, carbonaceous chondrites, and interplanetary dust particles

(IDPs). Their method can determine the compared abundances of major constituents

13
of the various ices and place constraints on the types of organics that coat icy grains in

the ISM. These materials may have been the basis for solar system biogenic element

and compound inventories. They have shown that ices in dense interstellar clouds

contain H20, CH3OH, CO, NH3, and H2CO as well as nitriles, ketones and esters.

Chemical and spectroscopic studies of photolyzed analogs, including deuterated

species, are ongoing.

V.G. Anicich and colleagues have been investigating radiation processing of ice

surfaces. Radiation causes the formation of radicals in ice which in turn react with

other species in the immediate vicinity. Thus, chemistry within the ice could produce

complex molecular species by ion-molecule reactions, a scenario that could be viable

in comets and other icy bodies. Laboratory results show that when pure ices are

radiated with Lyman alpha, an interconversion of CO to CO2 and CO2 to CO occurs. In

addition, C302 also forms and this compound has previously been suggested to form

in comets by radiation of CO. More complex experiments, together with the study of

kinetic factors, are being pursued.

E. Gibson and C. Harmetz have been studing volatiles associated with IDPs by using a

laser microprobe-mass spectrometer (LMMS). They analyzed IDPs collected in the

stratosphere via U2 aircraft and found a mixture of indigeneous compounds and

contaminates (e.g., silicone oil and "cleaning" solvents) associated with the collection

techniques. A small fraction of these contaminates remain despite careful "cleaning"

attempts, however, spectral-stripping techniques allow for realiable reading of

indigeneous compounds. Measured volatiles are similar to those of CI and CM

carbonaceous chondrites. Aerogel, a low density material proposed as a passive IDP

collection substrate on the Space Station, was also found to contain volatile

contaminates from the manufacturing process and these researchers concluded that

special efforts will be required to produce "clean" aerogel.

G. Yuen and associates have made long term investigations into the organic chemistry

and isotopic composition of the Murchison carbonaceous chondrite. Their present

work involves studing the potential of interstellar cloud input of organic matter into the

early solar system. They reported from their laboratory experiments that after

Murchison acetic acid was decarboxylated and the carbon isotopic composition was

measured from the released methane, the isotopic analyses showed sigificant

differences in the 13C/12C ratios for the methyl and carboxyl carbons of the acetic acid

molecule. This strongly suggests more than one carbon source for Murchison organic

compounds which has prompted creating laboratory model systems that simulate

cosmochemical organic synthesis.

14
N92-1 589

THE CHEMISTRY OF DENSE INTERSTELLAR CLOUDS

W. M. Irvine*

University of Massachusetts

The basic theme of this program is the study of molecular complexity and evolution in

interstellar and circumstellar clouds incorporating the biogenic elements. The dense

interstellar clouds are the formation sites for stars and presumably for planetary

systems. Understanding the molecular composition of these clouds provides probes

of physical conditions and evolution by allowing the measurement of local

temperature, density and motions; and also provides a means for studying the

chemistry in these environments which are so different from those normally

encountered in the terrestrial laboratory. Some ninety interstellar molecular species

have been identified, the majority of which are organic. The processes producing this

chemistry are becoming increasingly well understood, although major questions

remain which are being investigated by the observations undertaken as part of this

grant.

Recent results include the identification of a new astronomical carbon-chain molecule,

C4Si. This species was detected in the envelope expelled from the evolved star

IRC+10216 in observations at the Nobeyama Radio Observatory in Japan. C4Si is the

carrier of six unidentified lines which had previously been observed. This detection

reveals the existence of a new series of carbon-chain molecules, CnSi (n = 1, 2, 4).

Such molecules may well be formed from the reaction of Si + with acetylene and

acetylene derivatives. Other recent research has concentrated on the chemical

composition of the cold, dark interstellar clouds, the nearest dense molecular clouds to

the solar system. Such regions have very low kinetic temperatures, on the order of 10

K, and are known to be formation sites for solar-type stars. We have recently identified

for the first time in such regions the species H2S, NO, HCOOH (formic acid). The H2S

abundance appears to exceed that predicted by gas-phase models of ion-molecule

chemistry, perhaps suggesting the importance of synthesis on grain surfaces.

Additional observations in dark clouds have studied the ratio of ortho- to parathioformaldehyde. Since this ratio is expected to be unaffected by both radiative and

ordinary collisional processes in the cloud, it may well reflect the formation conditions

for this molecule. The ratio is observed to depart from that expected under conditions

of chemical equilibrium at formation, perhaps reflecting efficient interchange between

cold dust grains in the gas phase.

15
 .92-135-9o

THEORETICAL STUDIES OF THE EXTRATERRESTRIAL CHEMISTRY OF

BIOGENIC ELEMENTS AND COMPOUNDS

D. J. DeFrees

Molecular Research Institute

Organic compounds, molecules related to those in living systems, are found in many

different extraterrestrial environments. Including among these is interstellar space

where over 70 molecules have been discovered. The study of organic astrochemistry

is important to exobiology both because it demonstrates the ubiquity of processes

which led to life on Earth and because the dust clouds where molecules are found are

analogs of the solar nebula from which the Earth formed. In the long chain of events

leading from the Big Bang, and a universe composed of atomic hydrogen and helium,

to the emergence of life on Earth, molecular interstellar clouds are an early link, the

most primitive objects which display any significant organic chemistry. One such cloud

was the direct precursor to the solar system and to all objects which it contains.

Theoretical methods are ideally suited to studying interstellar cloud chemistry. They

have been applied to determine spectroscopic constants of candidate interstellar

molecules, mechanisms of ion-molecule reactions, and composition of dust grains.

Accurate predictions of rotational constants and dipole moments of long-chain carbon

molecules HC13N, HClsN, and C50 have been made to aid determining the size limit

of gas-phase interstellar molecules. Models of gas-phase interstellar chemistry use

reaction rate constants measured at room temperature and extrapolated to interstellar

temperatures. The temperature dependence of NH3 + + H2 ---) NHa ÷ + H is anomalous,

however, with a minimum rate at about lOOK, casting doubt on the extrapolation

procedures. The temperature dependence has now been explained.

16
N92"13591

MEASUREMENT OF THE SPECTRAL SIGNATURE OF SMALL CARBON

CLUSTERS AT NEAR AND FAR INFRARED WAVELENGTHS

J.Tarter*

SETI Institute/UC Berkeley Astronomy Department

and

R. Saykally

Chemistry Department, UC Berkeley

A significant percentage of the Carbon inventory of the circumstellar and interstellar

media may be in the form of large refractory molecules (or small grains) referred to as

carbon clusters. At the small end, uneven numbers of carbon atoms seem to be

preferred, whereas above 12 atoms, clusters containing an even number of carbon

atoms appear to be preferred in laboratory chemistry. In the lab, the cluster C6o

appears to be a particularly stable form and has been nicknamed "Bucky Balls"

because of its resemblance to a soccer ball and to geodesic domes designed by

Buckminster Fuller.

In order to investigate the prevalence of these clusters, and their relationship to the

polycyclic aromatic hydrocarbons (PAHs) that have become the newest focus of IR

astronomy, it is necessary to determine the spectroscopic characteristics of these

clusters at near and far infrared wavelengths. This paper describes the construction of

a near to far IR laser magnetic resonance spectrometer that has been built at the

University of California Berkeley in order to detect and characterize these spectra. The

equipment produces carbon clusters by laser evaporation of a graphitic target. The

clusters are then cooled in a supersonic expansion beam in order to simulate

conditions in the ISM. The expansion beam feeds into the spectrometer chamber and

permits concentrations of clusters sufficiently high as to permit ultra-high resolution

spectroscopy at near and far IR wavelengths.

The first successful demonstration of this apparatus occurred last year when the

laboratory studies permitted the observational detection of Cs in the stellar outflow

surrounding IRC+10216 in the near-IR. Current efforts focus on reducing the

temperature of the supersonic expansion beam that transports the C clusters

evaporated from a graphite target into the spectrometer down to temperatures as low

as I°K. If this can be achieved, then the spectral characteristics that are measured in

the spectrometer will correctly reflect the physical conditions in the ISM. The first

results on the far-IR spectra of C3 are encouraging. The signal-to-noise ratio is so high

that it should be possible to measure the spectral characteristics of much heavier

clusters in the near future.

When the lab studies have provided sufficiently precise identifications for these

heavier C clusters, an attempt will be made to detect them in circumstellar and

interstellar regions using spectrometers flown on the Kuiper Airborne Observatory.

The equipment used in these laboratory studies is extremely complicated and difficult

to operate, but its advantage lies in the precision with which the various rotational and

vibrational transition frequencies can be specified. There can be little or no doubt

about subsequent observational identification of astrophysical species.

17
N92- 13592

LABORATORY AND OBSERVATIONAL STUDY OF THE INTERRELATION

OF THE CARBONACEOUS COMPONENT OF INTERSTELLAR DUST AND

SOLAR SYSTEM MATERIALS

L.J. Allamandola*, S.A. Sanford, W.A. Schutte, and A.G.G.M. Tielens

NASA Ames Research Center

Interstellar dust and gas is the primordial material of the Solar System. Since the Sun

and planets formed only some 4.6 billion years ago in a universe thought to be

perhaps 15 billion years old, most of the biogenic elements may have already been

tied up in complex organic molecules by the time they became incorporated into the

planets, asteroids, satellites, and comets. Most interstellar material is concentrated in

large molecular clouds where simple molecules are formed by gas phase and dust

grain surface reactions. Gaseous species (except H2) striking the cold (10 K) dust will

stick, forming an icy grain mantle. This accretion, coupled with energetic particle

bombardment and UV photolysis will produce a complex chemical mixture containing

volatile, non-volatile, and isotopically fractionated species. These primordial ices and

complex organics may well be preserved without major modification in comets,

carbonaceous meteorites, and interplanetary dust particles. By studying the chemical

and isotopic composition of interstellar ice and dust, one gains insight into the

composition and chemical evolution of the solid bodies in the solar nebula and the

nature of the material subsequently brought into the inner part of the solar system by

comets and meteorites.

It is now possible to spectroscopically probe the composition of interstellar ice and

dust in the mid-infrared, the spectral range which is most diagnostic of fundamental

molecular vibrations. We can compare these spectra of various astronomical objects

(including the diffuse and dense interstellar medium, comets, and the icy outer planets

and their satellites) with the spectra of analogs we produce in the laboratory under

conditions which mimic those in these different objects. In this way one can determine

the composition and abundances of the major constituents of the various ices and

place general constraints on the types of organics coating the grains in the diffuse

interstellar medium. In particular we have shown the ices in dense clouds contain

H20, CH3OH, CO, perhaps some NH3 and H2CO, as well as nitriles and ketones or

esters. Furthermore, by studying the photochemistry of these ice analogs in the

laboratory, one gains insight into the chemistry which takes place in interstellar/precometary ices. Chemical and spectroscopic studies of photolyzed analogs (including

deuterated species) are now underway. The results of some of these studies will be

presented and implications for the evolution of the biogenic elements in interstellar

dust and comets will be discussed.

18
QUANTIFICATION OF UV STIMULATED

N92-13593

ICE CHEMISTRY: CO AND 002

V. G. Anicich*, T. Arakelian, and M. S. Hanner

Jet Propulsion Laboratory/CIT

It has been shown by several investigations in the past that the ice surfaces expected

for Oort comets can be processed by various forms of radiation and that new chemical

species are formed by the process. The radiation seems to cause the formation of

radicals within the ice and then these radicals react with the species present at the

boundary of their interstitial sites. Such chemistry within the ice can conceivably

produce complex organic compounds by a series of reactions. The continuous

radiation of the interstellar molecular clouds has been shown to result in measurable

concentrations of complex molecular species by a series of ion-molecule reactions. It

seems time to look at the individual reactions that do occur in pure ices and binary

mixtures of ices in order to quantify the reactions that occur in icy bodies.

Recent laboratory experiments are presented that show that during photolysis of the

,0JE_ ices there is evidence of the interconversion of CO to CO2 and CO2 to CO using

Lyman alpha (1216A) radiation. In addition, there is a substantial amount of another

substance being produced. This substance is evident by its infrared absorption peak

at 2235 cm o1. It is believed that this new peak is due to carbon suboxide, 0302. CO

and CO2 have already been detected in comets, and 0302 has been suggested as a

cometary from radiation of CO [Delitsky and Huntress, BAAS 20, (1988)].

Comparisons are made between our results at 1215A and proton radiation

experiments and radiation at other wavelengths. The suggestion is that the

processing of ices is energy dependent, i.e. dependent on the type of radiation.

Several difficult problems have to be solved before these radiation conversion can be

quantified. The steps that we are taking to quantify the kinetics are discussed.

19
N9 2- 13 594 .],

VOLATILES IN INTERPLANETARY DUST PARTICLES AND AEROGELS

E. K. Gibson, Jr.* and C. P. Harmetz

SN2 Planetary Sciences, NASA Johnson Space Center

Interplanetary dust particles (IDPs) offer a unique opportunity for developing a better

understanding of the cosmic history of the organogenic elements. The study of IDPs

has shown that they are complex, heterogeneous assemblages of both high and low

temperature phases and minor amounts of amorphous components. Some

components in IDPs may have originated as stellar or nebular condensates,

interstellar dust, interstellar or nebular molecules and products of parent body

processes (e.g. on comets or asteroids). The degree of success in distinguishing

between these possible sources rests largely with the ability to carry out compositional

analysis for elemental, isotopic, molecular, and mineralogical characterization. We

have been studying the nature of volatiles associated with IDPs by analyzing the

materials associated with the collection of IDPs (i.e. silicone oil, etc.) along with

analyzing individual IDPs which have been "cleaned of their contaminants." A laser

microprobe-mass spectrometer (LMMS) technique is utilized to vaporize the volatiles

within an individual IDP and detect the components associated with the particle.

Volatiles measured in 25 IDPs are a mixture of both indigenous materials and

contaminants associated with the collection and processing of the IDPs prior to

analysis. Most IDPs have been collected in the stratosphere using a silicone oil/freon

mixture (20:1 ratio) coated on collector plates. Studies have shown that silicone oil,

freon and hexane residues remain with the IDPs, despite attempts to clean the IDPs.

Analysis of the IDPs with the LMMS-technique produces spectra with a mixture of

indigeneous and contaminants components. Contamination signal can be identified

and removed, however the contamination signal may obscure some of the

indigeneous component's signal. Employing spectra stripping techniques, the

indigenous volatile constituents associated with the IDPs can be identified. Volatiles

are similar to those measured in CI or CM carbonaceous chondrites. Collection of

IDPs in low-Earth orbit utilizing a Cosmic Dust Collection Facility attached to Space

Station Freedom has been proposed. The low-density material aerogel has been

proposed as a collection substrate for IDPs. Our studies have concentrated on

identifying volatile contaminants that are associated with aerogel. We have found that

solvents used for the preparation of aerogel remain in aerogel and methods must be

developed for removing the entrapped solvents before aerogels can be used for an

IDP collection substrate.

2o
N92"13595

ISOTOPIC COMPOSITION OF MURCHISON ORGANIC COMPOUNDS:

INTRAMOLECULAR CARBON ISOTOPE FRACTIONATION OF ACETIC

ACID.

SIMULATION STUDIES OF COSMOCHEMICAL ORGANIC SYNTHESES.

G. U. Yuen* and J. R. Cronin

Arizona State University,

N. E. Blair

North Carolina State University,

and

D. J. Des Marais and S. Chang

NASA Ames Research Center

During the last 20 years, the organic compounds of the Murchison meteorite and, to a

lesser extent, other carbonaceous chondrites have been the object of extensive

qualitative and quantitative analyses. These data provide a detailed record of the

formation of organic compounds in the early solar system. Recent stable isotope

analyses, especially deuterium analyses, suggest that the meteorite organics are

closely related to, although not identical to, interstellar organic compounds. The

meteorite organics appear to have been derived from interstellar precursors during

hydrothermal alteration of the meteorite parent body. Meteorites, as well as comets,

may have been essential carriers of organic compounds to planetary bodies in the

habitable (liquid water) zone of the solar system. The organic compounds of

carbonaceous chondrites seem to provide evidence for a relationship between the

massive organic content of interstellar clouds and the organic-rich environment that is

presumably necessary for the origin of life on a planetary body. Further

characterization of the organic components of these meteorites is essential to

understanding organic chemical evolution in the early solar system. Research in

progress is aimed at (i) acquisition of additional qualitative and quantitative data

concerning meteoritic hydrocarbons, amines, amino acids, amino acid precursors, and

carboxylic acids, (ii) determination of the stable isotope content of these compounds,

(iii) comparison of isomeric variation and isotopic content in the meteorite compounds

with that found in the synthetic products from model processes, and (iv) relating

organic compounds to specific mineral phases of the meteorite matrix. These data will

further illuminate the origin of meteorite organic compounds and their relationships to

interstellar organics and other solar organic matter, for example, that of comets and

interplanetary dust particles (IDPs).

Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated

successfully and the carbon isotopic composition was measured for the methane

released by this procedure. These analyses showed significant differences in 13C/12C

ratios for the methyl and carboxyl carbons of acetic acid molecule strongly

suggesting that more than one carbon source may be involved in the synthesis of the

Murchison organic compounds. On the basis of this finding, laboratory model systems

simulating cosmochemical synthesis are being studied, especially those processes

capable of involving two or more starting carbon sources.

21

SOLAR SYSTEM EXPLQRATION (I)

Chairman - R. L. Mancinelli

The primary focus of Session II centered around methods for the search for traces of

an extinct martian biota. A variety of papers were presented ranging from the design

of flight hardware to conduct experiments of interest to exobiology in interstellar space,

to speculation on the presence of life on Mars.

P. Tsou spoke on the intact capture of cosmic dust particles traveling at hypervelocities

using a newly developed, light weight, inorganic silicate dust "catcher" termed aerogel.

In addition to being an efficient collector of small particles, aerogel decreases the

possibility of contamination of samples with extraneous organic material.

J. Huntington presented the concept of the Space Station's gas grain facility and

explained some of the potential applications for exobiology. J. Marshall explained the

use of the Space Shuttle "Glove Box Experiment", conceived and designed by him to

study the physics of particle aggregation in microgravity. This self-contained

experimental facility is scheduled to be flown and tested on the Shuttle during March

of 1992. The glove box microgravity research facility is being built by ESA and, once

fully developed, will be operated on a continuous basis and available to the scientific

community at large.

The concept of using laser spectroscopy to determine the ratio of 13C to 12C in martian

samples during a Mars mission was presented by Todd Sauke. He and co-author J.

Becker concluded that the 2300 cm-1 spectral region is the ideal portion of the spectra

in which to make these measurements. This was based on the fact that the rotational

lines of the two carbon isotopes in this region have approximately equal absorbance

at the isotopic ratios of the two isotopes as they occur on Earth and in the martian

atmosphere. Using sweep integration and signal averaging techniques, they have

measured the stable isotope ratio of CO2 samples to better than 1%, and strive to a

precision better than 0.1%.

J. Orenberg presented a model of the reflectance spectral data in the UV/VIS/NIR 0.3

to 2.5 mm-region and the IR 2.5 to 25 mm-region illustrating that the martian surface

material may be composed of palagonites and 2 to 4% clays. T. Roush presented data

from the recent airborne thermal infrared observation of Mars from the Kuiper Airborne

Observatory which provided evidence for the presence of carbonates, sulfates, and

hydrates in the dust in the atmosphere of Mars.

R.A. Wharton presented data regarding the applicability of perennially frozen lakes as

model systems for studying the possible evolution of life on Mars. In particular, he

discussed the mechanism of supersaturating the water beneath the icecover with N2

and 02 from the atmosphere, and how this may have benefited a possible martian

biota as Mars lost its atmosphere and became colder and drier. He also discussed the

mechanisms by which sediment enters the lakes through cracks in the ice.

23 PRECEDING PAGE BLAi"K NOT F,,..,_ED" "
P.J. Boston presented a summary of the current speculation regarding the possibility of

life existing beneath the surface of Mars. She stated that buried organisms would be

protected from the harsh conditions of the planet's surface, and that such habitats

could receive geothermal heat and so maintain water in a liquid state. In addition,

geothermally or volcanically reduced gases from the planet's interior could provide the

reducing power needed for a closed or semi-closed microbial ecosystem to survive.

R.L. Mancinelli presented data on carbon and nitrogen cycling in simple microbial

communities. Using these data, he showed that one can define experiments and put

limits on the types and kinds of compounds that may be utilized as martian

paleobiomarkers (i.e. traces of an extinct martian biota). In addition, these results

provide a database for ecological data interpretation enabling one to distinguish

abiotic from biotic processes on Mars. In particular, he presented data demonstrating

that Cjvnechococcus E_g.e,JJ.1849 while housed within a mixed gypsum halite crust was

actively dividing and was obtaining its carbon and nitrogen from atmospheric CO2 and

N2 respectively, through carbon and nitrogen fixation. This was presented as a

possible scenario for a current martian "oasis" or a last refuge as the planet lost its

atmosphere and became cold and dry. In addition, he presented data from a

"strawman" Mars soil analysis experiment defined from the database gathered from

the ecological studies of simple microbial communities. This "strawman" experimental

design illustrated how one can identify organic matter in soil and gypsum halite

evaporites using differential thermal analysis and gas chromatography.

A. Zent presented a strawman conceptual design for the analysis of the oxidation

potential of the martian surface. For example, he proposed that acetonitrile be used in

place of water as a solvent for measuring the Eh of the martian surface material using

an Eh electrode.

24
v

N9z-l g 56

INTACT CAPTURE OF COSMIC DUST

P. Tsou*

Jet Propulsion Laboratory/California Institute of Technology

Cosmic dust are extraterrestrial particles of cometary, asteroidal, samples of

planetesimals or even interstellar origin. Capturing these particles and returning them

to Earth so that they can be individually analyzed will contribute to our understanding

of the origin and evolution of our solar system. Dust analyses include elemental,

isotopic, and organic compositions and morphologic, petrographic, and phase studies.

The precision of the measurements and the range in sizes of analyzed particles will

exceed what can be done with in situ techniques on any space flight missions.

Furthermore, when particles can be captured intact without melting, then biological

elements and compounds and especially the original structural and phase

characteristics of the material can be preserved. This information is important to the

study of the cosmic evolution of biogenic compounds and the development models for

prebiotic and biotic evolution.

The encounter speeds of cosmic dust in Earth orbit are at hypervelocities. It was

believed that hypervelocity particles could not be captured intact; thus, the use of

capture cell or atomized capture of cosmic dust. The focus of this development effort is

to capture dust particles at hypervelocities intact, unmelted to preserve even volatile

organics, at the same time the capture process must minimize any organic elemental

or compound contamination to prevent any compromise of exobiological analyses.

Inorganic silicate aerogel has been developed as a successful capture medium to

satisfy both requirements of intact capture and minimal organic contamination. Up to 6

km/s, silicate projectiles from few microns up to 100 I_m have been captured intact

without any melting and with minimal loss of mass. Carbon in silicate aerogel can be

reduced to less than 1 part in 1000 and hydrogen 3 parts in 1000 when baked in air.

Under controlled inert gas environments additional hydrocarbon reduction can be

achieved.

25
N9 2- 13 597

EXOBIOLOGICAL IMPLICATIONS OF DUST AGGREGATION IN

PLANETARY ATMOSPHERES: AN EXPERIMENT FOR THE GAS-GRAIN

SIMULATION FACILITY

J. L. Huntington* and D. E. Schwartz

SETI Institute, NASA Ames Research Center

and

J. R. Marshall

Arizona State University, NASA Ames Research Center

Processes involving small particles (micrometer to centimeter in size) are important to the

understanding of a wide diversity of phenomena. Among them is the tendency for very fine

particles (dust) to aggregate into clusters as a result of surface electrostatic charging and van

der Waals forces, for example. Clustering or aggregation of materials has played an important

role in the origin and evolution of life. Within our own solar system, this aggregation process

influenced the rate and mode of formation of the solar system bodies themselves; it has

continued to influence life by controlling the rate at which planetary atmospheres are cleansed

of dust palls.

Aggregation of fine particles has been extensively modeled by mathematical analysis and

computer simulations, but the study of such phenomena in the terrestrial laboratory is virtually

impossible due to the fact that aggregation causes rapid sedimentation of materials to the

bottom of the experimental chamber; there is insufficient time for aggregates to fully develop,

and there is insufficient time for studying their behavior. This problem can be overcome by

conducting experiments in microgravity where protracted suspension times can be achieved.

The Gas-Grain Simulation Facility (GGSF) will provide such a microgravity environment where

undesirable environmental effects are reduced, and thus, experiments involving interactions

between small particles and grains can be more suitably performed.

The GGSF will occupy a Space Station double rack and consist of a number of subsystems

supporting an experiment chamber. The subsystems will provide environmental control (to

regulate temperature, pressure, humidity, etc.), mechanisms for injecting and removing

pariicles and clouds of particles, levitation systems, shock mounts and other vibration-isolating

systems, energy sources, and a number of experiment monitoring and measuring devices. A

number of experiments spanning a range of disciplines have been proposed for performance

in the GGSF which will be flown in several phases until the year 2000 when it will be a fully

independent module onboard Space Station Freedom.

The earliest flight opportunity is the ESA glovebox facility onboard Shuttle. Slated for flight in

1992, this glovebox will serve as a scientific and technological testbed for GGSF exobiology

experiments as well as generating some basic scientific data. Initial glovebox experiments will

test a method of generating a stable, mono-dispersed cloud of fine particles using a vibrating

sprinkler system. In the absence of gravity and atmospheric turbulence, it will be possible to

determine the influence of interparticle forces in controlling the rate and mode of aggregation.

The experimental chamber can be purged of suspended material to enable multiple

repetitions of the experiments. Of particular interest will be the number of particles per unit

volume of the chamber because it is suspected that aggregation will occur extremely rapidly if

the number exceeds a critical value. All aggregation events will be recorded on highresolution video film. Changes in the experimental procedure as a result of surprise events

will be accommodated by real-time interaction with the mission specialist during the Shuttle

flight.

26
N92"13598

STABLE CARBON ISOTOPE MEASUREMENTS USING

LASER SPECTROSCOPY

T. B. Sauke

NASA Ames Research Center

and

J. F. Becker

San Jose State University

On Earth, autotrophic organisms incorporate carbon-12 into their bodies with greater

efficiency than carbon-13. Carbon in organic earth sediments is enhanced in 12C by

about 2-3% and this enhancement constitutes a striking signature of the presence of

life. The ability to measure 120/130 ratios in situ would represent a powerful

discriminatory tool for searching for now-extinct life on Mars which may have laid down

isotopically enhanced carbon deposits. A Mars Rover and Sample Return mission

could utilize a carbon isotopic ratio measurement to help select which rocks and soil

samples to bring back to Earth and which to discard. Lead-salt tunable diode lasers

(TDLs) emit coherent infra-red light with a very narrow linewidth of approximately

0.0003 cm -1. It is possible to use a TDL to measure individual rotational lines within

the vibrational absorption band and determine their intensities, which can be used to

determine gas concentration and carbon isotopic ratios of CO 2 derived from Martian

rock and soil samples.

The 2300 cm -1 spectral region is especially interesting because the 12002 and 13002

bands overlap in such a way that their rotational lines have approximately equal

absorbance at the anticipated isotopic ratio (~90) of carbon on Earth and Mars. Pairs

of rotational lines we have studied are separated by as little as 0.050 cm "1, but are well

resolved with a TDL. Using sophisticated sweep integration and signal averaging

techniques, we have measured the stable isotope ratio in carbon dioxide to a

precision of better than 1%.

27
\

PALEOLAKES

N92-13599

AND LIFE ON EARLY MARS

°._

M. A. Meyer, R. A. Wharton, Jr.*

Desert Research Institute

and

C. P. McKay

NASA Ames Research Center

Did life begin on early Mars, as it did on Earth, during the planets' first billion years

after accretion? Early Mars had volcanism, an atmosphere, and liquid water - the

essential ingredient for life as we know it. Knowing whether or not life existed on

Mars is fundamental to our understanding of how life began in our solar system.

During future Mars missions, the search for evidence of extinct life can be directed

by research of terrestrial analogs of the possible conditions on Mars as the planet

became cold and dry. The McMurdo Dry Valleys in Antarctica have a mean annual

temperature of -20°C and less than 10 mm precipitation, yet within this barren land,

perennially ice-covered lakes harbor rich communities of microbial mats, coldwater homologs of ancient stromatolitic communities. The translucent ice-cover

insulates the subsurface liquid water from a frigid environment and permits

photosynthetic microorganisms to proliferate. In addition, atmospheric gases are

concentrated well above saturation by the exsolution of gases during freezing and

the subsequent loss of water through sublimation. These results suggest that the

purported Martian lakes, such as in Valles Marineris, may have harbored and

extended the time period for life by providing light, liquid water, and concentrated

gases as Mars cooled and its atmosphere thinned.

Two research directions have begun to elucidate key parameters in the search for

extinct life on Mars. Carbonate sediments, deposited about 10,000 years ago in

association with biological activity, have been sampled from the paleolake beds of

Lake Vanda and Meirs in the McMurdo Dry Valleys. These samples are being

analyzed for simple biological signatures that remain in cold and dry paleolake

sediments, namely microfossils, percent carbonate, and total organic carbon. Our

second initiative is the study of Colour Lake, in the Canadian Arctic, that

periodically maintains a perennial ice-cover. Physical measurements started this

year will be used to determine one end-point for ice-covered lake environments

and will be compared to continuous measurements from Antarctic lakes started in

November 1985. Interestingly, Colour Lake atso supports benthic mat communities

but the low pH precludes carbonate deposition. This research will broaden our

knowledge base for what conditions are necessary for ice-covered lake formation

and what biological signatures will remain in paleolake deposits.

28
SUBSURFACE MICROBIAL

Nge-1360o

HABITATS ON MARS

P.J. Boston*

Complex Systems Research, Inc.

and

C. P. McKay

NASA Ames Research Center

We have developed scenarios for shallow and deep subsurface cryptic niches for

microbial life on Mars. Such habitats could have considerably prolonged the

persistence of life on Mars as surface conditions became increasingly inhospitable.

The scenarios rely on geothermal hot spots existing below the near or deep

subsurface of Mars. Recent advances in the comparatively new field of deep

subsurface microbiology have revealed previously unsuspected rich aerobic and

anaerobic microbial communities far below the surface of Earth. Such habitats

protected from the grim surface conditions on Mars could receive warmth from below

and maintain water in its liquid state. In addition, geothermally or volcanically reduced

gases percolating from below through a microbiologically active zone could provide

reducing power needed for a closed or semi-closed microbial ecosystem to thrive.

Sulfur is such an abundant element in the surface materials of Mars that one might

expect this element to be abundant in subsurface material as well. Sulfur in its many

forms should be readily available to enter into the microbial chemistry of a subsurface

Martian ecosystem. To begin to substantiate the plausibility of our scenarios, we are

conducting preliminary experiments on several pure cultures and samples from

natural sulfureta to investigate the minimum concentrations of H2S which can be used

in various metabolic processes by these organisms.

Scenario development of possible Martian habitats of the past or present is difficult in

light of our limited knowledge of the planet. Nevertheless, such development is critical

for designing future robotic and human expeditions to look for extant life or traces of

extinct life. The subsurface habitats we suggest are amenable to the new microbial

drilling technologies being developed in the field of deep subsurface microbiological

remediation of subsurface pollutants. Techniques which will recover microbiologically

uncompromised deep samples for biological analysis will also provide a wealth of

information for Martian geologists, hydrologists, and volcanologists to ponder.

29
PALEOBIOMARKERS AND DEFINING

FUTURE MARS

N92-13601, 

EXOBIOLOGY EXPERIMENTS FOR

EXPERIMENTS

R. L. Mancinelli*, L.J. Rothschild and M. R. White

NASA Ames Research Center

Mars is a cold, dry planet with an oxidizing surface bombarded by ultraviolet and ionizing

radiation making prospects for an extant Mars biota bleak. Yet, it is suggested that early earth

and early Mars were similar enough that life may have evolved on Mars. If life did evolve on

Mars, what evidence for its existence might we find, that is, what constitutes a Martian

paleobiomarker, and how can we distinguish such a marker from abiotically produced

substances? The topics studied to answer this question include carbon and nitrogen cycling,

as well as the stability and relative abundance of their intermediates in microbially dominated

ecosystems. The microbially dominated ecosystems studied are the cryptoendolithic microbial

community living within sandstone rocks, endoevaporite microbial community living inside salt

crystals, and the microbial mat communities living beneath perennially ice-covered lakes and

hypersaline ponds. The nitrogen cycle of these communities ranges from the simple, where

only assimilation occurs (e.g., cryptoendoliths and endoevaporites) to the more complex

where a complete cycle occurs (e.g., microbial mats). The carbon cycle of these communities

appears to be complete that is, carbon fixation and remineralization through respiration occur.

The nitrogen cycle of the cryptoendolithic community, composed primarily of a lichen,

inhabiting the Antarctic dry valleys, is incomplete. Biological nitrogen fixation, denitrification

and nitrification do not occur in nature within this community. All of the fixed nitrogen is

supplied exogenously. This is much like the nitrogen cycle of the endoevaporitic microbial

community inhabiting a natural mixed crust of halite and gypsum. The endoevaporite

community consists primarily of a cyanobacterium tentatively identified as a member of the

genus Synechococcus N&geli 1849. In situ measurements demonstrate that this community

fixes nitrogen in nature, but neither nitrification nor denitrification was detected. The microbial

community inhabiting these ecosystems perform the least number of transformations of

nitrogen of any ecosystem reported to date, and therefore may represent the simplest nitrogen

cycle in nature. Both of these communities, however, fix carbon photoautotrophically.

In contrast, benthic microbial mats carry out complete nitrogen and carbon cycles in nature.

The mat inhabiting Lake Hoare, a perennially ice-covered lake in Taylor Valley, Antarctica

exhibits an incomplete nitrogen cycle during the austral summer (no N2-fixation), and a

complete nitrogen cycle during spring before melt water runs into the lake. These data

suggest that the demand for nitrogen is being met by input from meltwater and sediment

entering the lake. Denitrification occurs only within anaerobic sediments, whereas nitrification

only occurs in the aerobic portions of the sediment and mat. In the microbial mats inhabiting a

hypersaline pond, the nitrogen cycle appears to always be complete. The pattern of nitrogen

and carbon fixation and denitrification varies diurnally. Data suggests that this phenomenon is

due to diurnal changes in nutrient limitation.

These studies allow us to define experiments and put limits on the types and kinds of

compounds that may be utilized as Martian paleobiomarkers. In addition, they provide a data

base for ecological data interpretation enabling us to distinguish abiotic from biotic processes.

30
CONCEPTUAL DESIGNS FOR IN SlTU

N92-13602

ANALYSIS OF MARS SOIL

C. P. McKay and A.P. Zent*

NASA Ames Research Center

and

H. Hartman

University of California, Berkeley

The Viking Biology results, and the absence of organic material in the soil of Mars

have led to the suggestion that there is one or more oxidants in the martian soil.

Based upon the results of the Gas Exchange Experiment and the Labeled Release

Experiment, Klein (Icarus, 34, 666, 1978) suggested the presence of three oxidants: a

strong thermally stable oxidant, a strong thermally labile oxidant, and a weak oxidant.

The nature and concentration of oxidants in the martian soil has two important

implications: for exobiology, the preservation of organic material from an early

biological period on Mars; and for human exploration, the health and safety of

astronauts on the surface. As indicated by the absence of organic material in the near

surface at the two Viking sites, the oxidant may have destroyed any organic material to

some depth. The depth from which samples must be returned if there is to be any

hope of finding organic material on Mars will depend on the nature of the soil oxidants

and their mobility through the soil. For human explorers the soil oxidant may pose a

hazard to material and equipment as well as a health hazard due to the inevitable

movement of dust within the habitat.

The goal of this research is to develop conceptual designs for instrumentation to

perform in situ measurements of the Martian soil in order to determine the existence

and nature of any reactive chemicals.

Our approach to this problem involves three aspects: 1) Assessment and critical

review of the Viking Biology results which indicated the presence of a soil oxidant. 2)

An investigation of the possible application of standard soil science techniques to the

analysis of Martian soil. 3) Preliminary consideration of non-standard methods that

may be necessary for use in the highly oxidizing Martian soil.

Based on our preliminary analysis we have developed strawman concepts for

standard soil analysis on Mars, including pH, suitable for use on a Mars rover mission.

In addition, we have devised a method for the determination of the possible strong

oxidants on Mars.

31
N9 2- 13 603

SPECTROSCOPY AND REACTIVITY OF MINERAL ANALOGS OF THE

MARTIAN SOIL

A. Banin

Soil and Water Science, Hebrew University,

J. Orenberg*

Chemistry Department, San Francisco State University

and

T. Roush

NASA Ames Research Center

in order for exobiologists to gain a better understanding of the similarities and

differences between the early environments on Earth and Mars, and thus to answer a

primary question in comparative planetology as to why life developed on earth to its

rather complex level and why, apparently, this did not occur on Mars, the geochemical

and physical aspects of the martian soil must be studied and elucidated, The martian

soil participates in present day surface-atmosphere interactions, volatile balances, and

geological land forming processes. The soil holds important clues to the processes

that shaped the early geological history of Mars, to the amount of liquid once present,

and to the possibility of early evolved life or existing life on the planet.

Some of the "best" Mars analog mineral models of the soil have been prepared and

justified according to known constraints of chemical composition, reflectance

spectroscopy and chemical reactivity. Detailed laboratory reflectance spectra in the

UVNIS/NIR (.30-2.5 I_m) and IR (2.5-25 t_m) regions have been obtained for the pure

candidate minerals and some analog mixtures and compared to Mars reflectance

spectra. Modeling of the reflectance spectra from optical constants determined for the

analog minerals has begun and will be interpreted in terms of the effects of particle

size variation, component mixing, and soil packing upon remotely sensed reflectance

spectra. This has implications not only for Mars, but for other planets and planetoids.

The ratio of Fe(ll)/Fe(lll) in the martian soil analog materials on spectral reflectance in

the visible range has begun, and the results will be evaluated according to conformity

with the visible Mars reflectance spectrum. Some initial LR and GEX data have been

collected for the mineral samples and their mixtures which can be compared to the

Viking data and interpreted in terms of the redox (Fe(ll)/Fe(lll) environment.

32
Ngz-13604

MIDINFRARED SPECTRAL INVESTIGATIONS OF

CARBONATES: ANALYSIS OF REMOTELY SENSED DATA

T. Roush*

NASA Ames Research Center/San Francisco State University Foundation Inc.,

J. B. Pollack and (3. P. McKay

NASA Ames Research Center

There are ample theoretical reasons and geomorphic evidence that during the earliest

history of Mars liquid water was stable at the surface. The higher temperatures

required to maintain water as a liquid are often attributed to higher concentrations (1-

10 bars) of the greenhouse gas carbon dioxide (CO2). The current observed

concentration of (302 (roughly 7 mbars) leads to an enigma regarding the fate of the

remaining original gas. One line of reasoning suggests that (302 reacted chemically

with igneous silicates to form carbonate (CO3) rocks, resulting in its permanent

removal from the atmosphere. If this scenario is correct, then identification of (303

rocks on the current martian surface would provide evidence of an early clement

environment where the presence of higher temperatures and liquid water may have

been conducive to the evolution of life. Additionally, identification of specific (303

species can provide significant insight into the depositional environment in which they

formed.

Recent airborne thermal infrared observations of Mars from the Kuiper Airborne

Observatory (KAO) have provided evidence for the presence of carbonates, sulfates

(SO4), and hydrates. Analyses of these data have relied upon radiative transfer

models which account for thermal emission from the surface, as well as absorption,

emission and scattering due to both solids and gases present in the atmosphere.

From first principals these models rely upon knowledge of the optical properties of

materials, and these are limited for CO3's and SO4's. While the optical properties of

calcite (CaCO3) and anhydrite (CaSO4) can not explain the details of specific spectral

features, values of more appropriate materials are unavailable. Using the optical

properties of calcite and anhydrite, it was estimated that CO3's and SO4's constituted

about 1-3 and 10-15 wt.%, respectively of the materials composing the atmospheric

dust. Using the derived value as an estimate of total CO3 abundance, and making an

assumption that the CO3's were uniformly distributed within the martian regolith, it was

estimated that such a CO3 reservoir could contain roughly 2-5 bars of (302.

While the results indicate that several volatile-bearing materials are present on Mars,

the observations from the KAO are inherently limited in their ability to determine the

spatial distribution of these materials. However, previous space craft observations of

Mars provide both the spectral coverage necessary to identify these materials, as well

as the potential for investigating their spatial variability. This has prompted us to

pursue a reinvestigation of the Mariner 6 and 7 infrared spectrometer and Mariner 9

infrared interferometer spectrometer observations. The former data have been

recently made available in digital format and calibration of wavelengths and intensities

are almost complete. Additionally, we are pursuing the derivation of optical constants

of more appropriate carbonates and sulfates.

33

PREBIOTI0 EVOLUTION

Chairman - S. Chang

Session III covered a wide range of topics in prebiotic evolution and the origin of life.

In the twenty one papers presented, the topics ranged from the origin of organic matter

in meteorites and the outer planets to nucleic acid polymerization and evolution on the

early Earth to the rise of oxygen in the Proterozoic.

J. Kerridge started the session by summarizing the status of isotopic studies of the

organic matter in carbonaceous meteorites in a paper entitled "Isotopic Constraints on

the Origin of Meteoritic Organic Matter." He pointed out the importance of isotopic

measurements of carbon, nitrogen and hydrogen in elucidating the origin and

synthetic pathways for the organic components, and he described his progress in

developing secondary ion mass spectrometry as a technique for measuring hydrogen

isotopic compositions of specific molecular fractions. Anomalously high ratios of D/H

which have been observed in organic extracts from meteorites have been attributed to

interstellar origins.

In "Kinetic Conversion of CO to CH4 in the Solar System," Y. Yung, M. Allen, and J.

Pinto described theoretical calculations showing the importance of formation of the

methoxy radical, CH30, in the conversion of CO to CH4. They discussed the possible

relevance of various steps in the overall process to organic synthesis in the Earth's

early atmosphere, to chemical evolution of carbon in the solar nebula and to putative

evidence for polyoxymethylene in comet Halley.

The next three papers described laboratory simulations of organic chemical processes

in the outer solar system. "Production of Organic Compounds in Plasmas: a

Comparison Among Electric Sparks, Laser-induced Plasmas and UV Light,"

summarized work by T. Scattergood, C. McKay, W. Borucki, L. Giver, H. Van

Ghyseghem, J. Parris, and S. Miller. This team showed that ultraviolet photochemistry

resulting from light produced in spark and plasma processes was responsible for the

synthesis of saturated hydrocarbons in excess of those predicted by theory. Results

of experiments on plasma excitation of simulated planetary atmospheres and charged

particle irradiation of mixtures of hydrocarbon and water ices as analogs of icy bodies

were described by C. Sagan, W. Thompson, B. Khare, and C. Chyba in the paper,

"Organic Synthesis in the Outer Solar System: Recent Laboratory Simulations for

Titan, the Jovian Planets, Triton and Comets." The plasma experiments were able to

account for all species observed by the Voyager spacecraft at Titan, and the ice

irradiations afforded product mixtures whose IR spectra contained a band at 3.4 m

matching the emission feature of Comet Halley and other comets. J. Ferris and J.

Guillemin reported on "Photochemical Reactions of Cyanoacetylene and

Dicyanoacetylene: Possible Processes in Titan's Atmosphere." These authors

described the production of cyanobenzenes and cyanocyclooctatetraenes and

suggested a synthesis mechanism involving cyanocyclobutadienes as intermediates.

The findings of all three papers underscored the rich organic chemistry that may be

found in the atmospheres and surface materials of objects in the outer solar system.

35 PRECEDING PAGE BLANK NOT RLMED
A transition in chemical evolution from the outer to the inner planets was provided by

two papers. The first was that of C. Chyba, C. Sagan, P. Thomas, and L Brookshaw

on " Terrestrial Production vs. Extraterrestrial Delivery of Prebiotic Organics to the

Early Earth." These workers conducted a theoretical study of the interaction of

impacting comets/asteroids with Earth's early atmosphere and surface. In their

evaluation of endogenic versus exogenic processes, they concluded that the

contribution of organic compounds delivered intact by comets would have exceeded

those provided by asteroidai impacts, interplanetary dust particles or atmospheric

synthesis in scenarios calling for a dense CO2 atmosphere. The second paper on

"Self-Assembly Properties of Primitive Organic Compounds" was given by D. Deamer.

He showed that pyrene, a major polycyclic aromatic hydrocarbon found in the

Murchison meteorite, acted as a photosensitizer in the aqueous photochemical

hydroxylation of hydrocarbons to produce surface active molecules which could have

been capable of participating in membrane formation on the primitive Earth.

In theoretical studies relevant to primitive membrane formation and function, A.

Pohorille, M. Wilson, and R. MacEIroy investigated the "Structure and Functions of

Water-Membrane Interfaces and Their Role in Proto-biological Evolution.'; In computer

simulations, these researchers showed that the dipolar orientation of water at nonpolar

interfaces facilitates the approach of positive rather than negative ions and that

amphiphilic molecules also take a preferred orientation such that the polar group is

buried in the water while the hydrocarbon portion extends into the nonpolar medium.

Their model studies have also revealed that simple ionophores bind and transport

ions by the same physical chemical mechanism as do ion channels and carriers from

modern cells.

The next series of papers discussed additional aspects of chemical evolution on the

Earth. In the first, "Sources and Geochemical Evolution of Cyanide and

Formaldehyde," delivered by G. Arrhenius, synthesis of cyanide by deposition of

• auroral electrons into a CO2-containing atmosphere was hypothesized. Literature

data and experimental results suggested that cyanide could have been preserved

against hydrolysis in the form of inorganic ferrocyanide and released by

photooxidation of the latter, followed by reactions with formaldehyde to form

glycolonitrile and other products of interest for chemical evolution. The role of

inorganic material in chemical evolution was also the subject of the paper by L. Coyne,

R. Mariner, and A. Rice entitled "Kaolinite-catalyzed Air Oxidation of Hydrazine:

Consideration of Several Compositional, Structural, and Energetic Factors in Surface

Activation." Using hydrazine oxidation as a reaction to investigate the energy sources

and identity of various types of catalytic sites in clay, these workers showed that O"

centers and ferric iron centers play dominant roles rather than simply trace structural

and surface contaminants. Energy was also the focus of "Carbohydrates as a Source

of Energy and Matter for the Origin of Life" by A. Weber who reported recent

developments in his model for early glycolysis including racemization-free thermal

synthesis of polyglyceric acid and determination of the free energy available through

hydrolysis of its 2- and 3-glyceryl esters. Weber also reported that glyceraldehyde is

bound and oxidized to glyceric acid on ferric hydroxide surfaces while soluble ferric

iron catalyzes the rearrangement of glyceraldehyde to lactic acid.

36
Ng -13665

ISOTOPIC CONSTRAINTS ON THE ORIGIN OF METEORITIC

ORGANIC MATTER

J. F. Kerridge*

UCLA

Salient features of the isotopic distribution of H, C and N in the organic material found

in carbonaceous meteorites are the following: Most organic fractions are strongly

enriched in D with respect to the D/H ratio characteristic of H2 in the protosolar system;

substantial variations in 130/120 ratio are found among different molecular species,

with oxidised species tending to be 13C-enriched relative to reduced species; some

homologous series reveal systematic decrease in 130/120 with increasing C number;

considerable variation in lSN/14N ratio is observed within organic matter, though no

systematic pattern to its distribution has yet emerged; no interelement correlations

have been observed between isotope enrichments for the different biogenic elements.

The isotopic complexity echoes the molecular diversity observed in meteoritic organic

matter and suggests that the organic matter was formed by multiple processes and/or

from multiple sources. However, existence of a few systematic patterns points towards

survival of isotopic signatures characteristic of one or more specific processes. The

widespread D enrichment implies either survival of many species of interstellar

molecule or synthesis from a reservoir containing a significant interstellar component.

Several of the questions raised above can be addressed by more detailed

determination of the distribution of the H, C and N isotopes among different wellcharacterised molecular fractions. Thus, the present study is aimed at discovering

whether the different amino acids have comparable D enrichments, which would imply

local synthesis from a D-enriched reservoir, or very variable D enrichments, which

would imply survival of some interstellar amino acids. The same approach is also

being applied to polycyclic aromatic hydrocarbons. Because the analytical technique

employed (secondary ion mass spectrometry) can acquire data for all three isotopic

systems from each molecular fraction, any presently obscured interelement isotopic

correlation should also be revealed, which will aid in identifying pertinent synthetic

processes.

37
N92-13506

KINETIC CONVERSION OF CO TO CH4 IN THE SOLAR SYSTEM

Y. L. Yung*, M. Allen and J. P. Pinto

California Institute of Technology

Some of the most interesting chemistry in the Solar System involves changes in the

oxidation state of the simple carbon species. The chemical pathways for the

conversion of CH4 to CO and CO2 are for the most part known. The reverse process,

the reduction of CO to CH4, is, however, poorly understood. This is surprising in view

of the importance of the reduction process in the chemistry of the Solar System.

Recently we investigated the chemical kinetics of a hitherto unsuspected reaction. It is

argued that the formation of the methoxy radical (CH30) from H+H2CO may play an

essential role in the reduction of CO to CH4. The rate coefficient for this reaction has

been estimated using the approximate theory of J. Troe and transition state theory. We

will discuss the implications of this reaction for the chemistry of CO on Jupiter, in the

solar nebula, for interpreting the laboratory experiments of A. Bar-Nun and A. Shaviv

and A. Bar-Nun and S. Chang and for organic synthesis in the prebiotic terrestrial

atmosphere. The possible relation of CO reduction in the solar nebula and

polyoxymethylene observed in comet Halley will be discussed.

38
}/92-13607

PRODUCTION OF ORGANIC COMPOUNDS IN PLASMAS: A

COMPARISON AMONG ELECTRIC SPARKS, LASER-INDUCED PLASMAS

AND UV LIGHT

T. W. Scattergood*

S. U. N. Y. at Stony Brook,

C.P. McKay, W. J. Borucld, L.P. Giver, H. Van Ghyseghem

NASA Ames Research Center,

J.E. Pan'is

SETI Institute

and

S.L. Miller

U. C. San Diego

The chemistry in planetary atmospheres that is induced by processes associated with hightemperature plasmas is of broad interest because such processes may explain many of the

chemical species observed. There are at least two important phenomena that are known to

generate plasmas (and shocks) in planetary atmospheres: lightning and meteor impacts.

Lightning has long been recognized to be an important driver of chemical reactions in the

Earth's atmosphere and, probably, in the atmospheres of Jupiter, Saturn and Venus.

Lightning may also have provided a source for prebiotic compounds on the early Earth.

Meteors and cometary objects impacting planetary atmospheres may have supplied prebiotic

compounds to or initiated chemical processes in the atmospheres. For both lightning and

impacts, rapid heating of atmospheric gases leads to the formation of a high-temperature

plasma which emits radiation and produces shock waves that propagate through the

surrounding atmosphere. These processes initiate chemical reactions that can transform

simple gases into more complex compounds. For example, electric discharges in mixtures of

H2/CH4/NH3 and CH4/N2, representing the atmospheres of Jupiter and Titan, respectively, are

known to produce a suite of gaseous and condensed phase hydrocarbons and C-N

containing compounds. Also, processing of Titan's early atmosphere from impacts of meteors

and comets may have been responsible for the molecular nitrogen still there today.

In order to study the production of organic compounds in plasmas (and shocks), various

mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete

sparks, laser-induced plasmas (LIP) and ultraviolet light. The yields of HCN and simple

hydrocarbons were measured and compared to those calculated from a simple quenched

thermodynamic equilibrium model. The agreement between experiment and theory was fair

for HCN and 02H2. However, the yields of C2H6 and other hydrocarbons were much higher

than those predicted by the model. Our experiments suggest that photolysis by ultraviolet light

from the plasma is an important process in the synthesis. This was confirmed by the

photolysis of gas samples exposed to the light, but not to the plasma or shock waves. The

results of these experiments demonstrate that, in addition to the well-known efficient synthesis

of organic compounds in plasmas, the yields of saturated species, e.g. ethane, may be higher

than predicted by theory and that LIP provide a convenient and clean way of simulating

planetary lightning and impact plasmas in the laboratory.

39
N92- 13 608

ORGANIC SYNTHESIS IN THE OUTER SOLAR SYSTEM:

RECENT LABORATORY SIMULATIONS FOR TITAN, THE JOVIAN

PLANETS,TRITON AND COMETS

C. Sagan,* W. R. Thompson, B.N. Khare, and C. F. Chyba

Laboratory for Planetary Studies, Cornell University

The atmosphere of Titan is composed mainly of N2, with 3-12% CH4 (depending on

altitude and details of the surface equilibrium). Voyager revealed Titan to be covered

by a thick haze; the optical properties of this haze derived by scattering models are

consistent with those of organic heteropolymer (tholin) produced in the laboratory by a

plasma discharge in 90% N2-10% CH4. Abundant amino acids are produced from this

tholin on hydrolysis. We have recently analyzed the volatile products of continuous

flow plasma excitation of this atmosphere (generated on Titan primarily by Saturnian

magnetospheric electrons and solar and galactic cosmic rays), and find some 60

products, including many multiply-bonded hydrocarbons and nitriles.

We tabulate below the most abundant gases and their radiation yields, for two

experimental pressures: 0.24 mb, more relevant to upper atmosphere excitation, and

17 mb, more relevant to tropospheric, cosmic ray excitation. The yields computed in

the 0.24 mb experiment combined with measured electronic fluxes and a simple, eddy

diffusion model of Titan's atmosphere predict abundances of detected molecules in

agreement with those found by Voyager and for heavier products, in somewhat better

agreement with observation than photochemical absolute reaction rate kinetics

models . All Voyager organics are accounted for and no detectable products are

found that Voyager did not detect. A striking increase of products with multiple bonds

is found with decreasing pressure. Hydrocarbon abundances decline slowly with

increasing carbon number.

Additionally, we list preliminary estimates for the yield of the heteropolymer, which

seems to be produced in a quantity comparable (in moles of C+N consumed) to the

total amount of gaseous product. The production rate required to sustain Titan's haze

against sedimentation also indicates yields of this order. As can be seen from the

table, over 109 years substantial amounts of these products can accumulate on the

surface -- ranging from cm thicknesses for the (C+N=4) species to a meter or more for

HCN and 02H2; we also expect a meter or more of tholins.

Similar analyses have been or are being done for the Jovian planets and Triton.

Charged particle irradiation of hydrocarbon clathrates or mixed hydrocarbon/water

ices produces a range of organic products, reddening and darkening of the ices and

characteristic infrared spectra. From such spectra, the predicted emission by fine

particles in cometary comae well-matches the observed 3.4 I_m emission spectra of

Comet Halley and other recent comets. Heliocentric evolution of organic emission

features in comets is predicted. Organic products of such ice irradiation may account

for colors and albedos on some of the satellites in the outer solar system, especially

Triton and Pluto, where solid methane is known to exist.

4o
Orzanic Synthesis in the Outer Solar System...Saglm et sl.

Titan Continuous Flow Simulation Results

(from W.R. Thompson, T. Henry, J. Schwsu'ts, B.N. Khare, and C. Ssgan, Icarus. in press)

G, 17 mb G, 0.24 mb Kinetic Colurrul, Deqslty

molec/lO0 eV molec/lO0 9V _ Chemical Model + This Work + m/cm_/10 _ y

HC_CH

HC_N

N_C-C_N

HC_C-C_N

CH3C_N

CH3-C_CH

1.6 x 10 -1 3.9 x 10 -3 2 x 10 -6 4.0 x 10 -6 0.3-1.3 x 10 -6 150 - 1770

3.3 x I0 -2 1.6 x I0 -I 2 x I0 -7 5.6 x 10 -7 1.8-9.0 x 10 -7 50 - 330

3.6 x 10 -3 2.8 x 10 -3 10 .7 - 10 -8 1.9 x 10 -8 1.4-7.0 x 10 "8 7.3 - 28

2.4 x 10 -3 8.8 x 10 "3 10 -7 - 10 -8 5.6 x 10 -8 1.6-8.0 x 10 -8 6.1 - 51

1,5 x 10 -3 4.6 x I0 "3 .......... 0.7-3.2 x 10 -8 2.8

1.4 x 10 -3 1.9 x 10 -2 $ x 10 -8 1.8 x 10 -7 0.3-1.4 x 10 -8 5 - 130

1.7 x 10 -3 .......... 0.6-$.0 x 10 -8 2.8

1.5 x 10 -3 10 -7 - 10 -8 7.8 x 10 -10 0,4-1.8 x 10 -8 1.7

1.6 x 10 "2 .......... 1.5-7.S x 10 "9 3.8

1.7 x 10 -3 .......... 1.1-5.5 x 10 .9 0.8

1.3 x 10 .3 .......... 0.8-4.1 x 10 -9 0.6

- 0.2-2 100 - 1000

H2C=CH-CH=CH 2 1.3 x 10 -3

HC=C-C=CH 8.2 x 10 -4

H2C=C=CH 2 7.7 x 10 "4

H2C=CH-C=CH 2.4 x 10 -4

H2C=CH-C=N 1.9 x 10-4

Heteropolymers* - 0.2-2

*Units of measure are total atomJ (C+N). +These volume mixing ratios derive from simple eddy diffusion modelm of

vertical transport. Laboratory results are shown for 0.24 rob, roughly where magnetospheri¢ electrons drive

atmospheric chemistry.

41
N92-13609

PHOTOCHEMICAL REACTIONS OF CYANOACETYLENE AND

DICYANOACETYLENE: POSSIBLE PROCESSES IN TITAN'S

ATMOSPHERE

J. P. Ferris* and J. C. Guillemin

Department of Chemistry, Rensselaer Polytechnic Institute

Titan has an atmosphere which is subject to dramatic chemical evolution due mainly to

the dramatic effect of the UV flux from the Sun. The energetic solar photons and other

particles are converting the methane-nitrogen atmosphere into the unsaturated carbon

compounds observed by the Voyager probes. These same solar photons are also

converting some of these unsaturated reaction products into the aerosols observed in

the atmosphere which obscure the view of the surface of Titan. In particular, the

photochemical reactions of cyanoacetylene, dicyanoacetylene, acetylene and

ethylene may result in the formation of the higher hydrocarbons and polymers which

result in the aerosols observed in Titan's atmosphere.

Polymers are the principal reaction products formed by irradiation of cyanoacetylene

and dicyanoacetylene. Irradiation of cyanoacetylene with 185 nm of light also yields

1,3,5-tricyanobenzene while irradiation at 254 nm yields 1,2,4-tricyanobenzene and

tetracyanocyclooctatetraenes. Photolyses of mixtures of cyanoacetylene and

acetylene yields mono- and di- cyanobenzenes. 1-Cyanocyclobutene is formed from

the photochemical addition of cyanoacetylene with ethylene. The photolysis of

dicyanoacetylene with acetylene yields 2,3-dicyano-l,3-butadiene and 1,2-

dicyanobenzene. Tetracyanocyclooctatetraene products were also observed in the

photolysis of mixtures of dicyanoacetylene and acetylene with 254 nm light. 1,2-

Dicyanocyclobutene is obtained from the photolysis of dicyanoacetylene and ethylene.

Reaction mechanisms will be proposed to explain the observed photoproducts.

42
N92-13610

CONTROLLED EVOLUTION OF AN RNA ENZYME

G. F. Joyce*

Department of Chemistry and Department of Molecular Biology,

Research Institute of Scripps Clinic

It is generally thought that prior to the origin of protein synthesis, life on earth was

based on self-replicating RNA molecules. This idea has become especially popular

recently due to the discovery of catalytic RNA (ribozymes). RNA has both genotypic

and phenotypic properties, suggesting that it is capable of undergoing Darwinian

evolution. RNA evolution is likely to have played a critical role in the early history of

life on earth, and thus is important in considering the possibility of life elsewhere in the

solar system. We have constructed an RNA-based evolving system in the laboratory,

combining amplification and mutation of an RNA genotype with selection of a

corresponding RNA phenotype. This system serves as a functional model of a

primitive organism. It can also be used as a tool to explore the catalytic potential of

RNA. By altering the selection constraints, we are attempting to modify the substrate

specificity of an existing ribozyme in order to develop ribozymes with novel catalytic

function. In this way, we hope to gain a better understanding of RNA's catalytic

versatility and to assess its suitability for the role of primordial catalyst.

All of the RNA enzymes that are known to exist in contemporary biology carry out

cleavage/ligation reactions involving RNA substrates. The Tetrahymena ribozyme, for

example, catalyzes phosphoester transfer between a guanosine-containing and an

oligopyrimidine-containing substrate. We tested the ability of mutant forms of the

Tetrahymena ribozyme to carry out a comparable reaction using a DNA, rather than

RNA substrate. An ensemble of structural variants of the ribozyme was prepared and

tested for their ability to specifically cleave d(GGCCCTCToA3TA3TA) at the

phosphodiester bond following the sequence CCCTCT. We recovered a mutant form

of the enzyme that cleaves DNA more efficiently than does the wild-type. Beginning

with this selected mutant we have now scattered random mutations throughout the

ribozyme and have begun an evolutionary search to further expand the catalytic

repertoire of RNA.

43
N92-13611 i.

SOURCES AND GEOCHEMICAL EVOLUTION OF CYANIDE AND

FORMALDEHYDE

G. Arrhenius

Scripps Institution of Oceanography

Although several systems have been proposed to be capable of molecular recognition and replication,

only pudne-pydmidine base pairing has been experimentally demonstrated to perform those combined

functions. Early precursors of RNA may be assumed to have utilized a minimum of two nitrogen bases

attached to acyclic hydroxyaldehydes, and originally, or at a more advanced stage, to have incorporated

phosphate linkages. Such an evolution would require satisfactory sources of cyanide, simple aldehydes,

and reactive phosphate species. Furthermore, efficient geochemical mechanisms are needed to

selectively concentrate these components into an environment where appropriate reactions can be

demonstrated to be possible and probable.

The major source of cyanide has, in current paleoatmosphedc models, been assumed to be the reaction

of photodissociated thermospheric nitrogen with a limiting supply of stratospheric methane.

Formaldehyde may be produced with more ease from an atmosphere with an atmosphere of carbon

dioxide as the dominant carbon species, and from carbonate in solution or sorbed in double-layer

hydroxide minerals.

Potentially more important sources for cyanide and other carbon containing molecules are the partially

photoprotected northern and southern auroral ovals where continuous currents reaching several megaamperes induce ion-molecule reactions, extending into the lower stratosphere - in simulated

environments of this kind cyanide ion is known to be produced from oxidized carbon species potentially

more abundant than methane.

Rainout of cyanide and formaldehyde place them in two different geochemical reaction reservoirs. In the

anoxic Archean hydrosphere, about 1 mM in Fe2+, cyanide ion would have been efficiently converted to

the stable ferrocyanide complex Fe(CN)64-, protecting it from the commonly considered fate of

decomposition by hydrolysis, and eventually incorporating it in pyroaudte materials type minerals, most

efficiently in green rust where it converts to insoluble ferriferrocyanide, prussian blue.

In snow and firn the Sanchez-Orgel freezeout process would lead to eutectic concentration of

glycolonitrile and its oligomers as reaction products of cyanide and formaldehyde, the latter probably

always present in excess.

The cyanide in the hydrosphere, strongly bound to ferrous iron, is shown experimentally to be liberated

on photooxidation of ferrocyanide with concurrent precipitation of -y-FeOOH. In the presence of an

equimolar or larger fraction of formaldehyde in 10mM solution pH 7, the liberated cyanide practically

completely converts to glycolonitrile.

The seemingly ubiquitous cyanohydrin production inferred from the Archean cryosphere and

hydrosphere focuses the attention on the following evolution of these compounds. Glycolonitrile

(formaldehyde cyanohyddn) in neutral or weakly alkaline solution oligomedzes along two different paths.

One, kinetically favored at low temperatures, such as in the Sanchez-Orgel situation, leads to a

crystallizable compound, presumed to be 6-amino-5-hydroxy-2,4-pyrimidine dimethanol. The prospect of

spontaneous formation of such a pyrimidine from geochemically plausible source is of interest for

biopoesis; the structure and reactivity of this model is now being investigated.

The second reaction of glycolonitrile, kinetically dominant at ambient temperature, produces a light yellow

oligomer, which at increasing polymerization turns into a brown, viscous liquid and eventually to a black

solid. Hydrolysis and pyrolysis of such a polymer may provide a source of amino compounds and

ammonia, difficult to produce and maintain in the Archean atmosphere.

44
N92-13612

KAOLINITE-CATALYZED AIR OXIDATION OF HYDRAZINE:

CONSIDERATION OF SEVERAL COMPOSITIONAL, STRUCTURAL AND

ENERGETIC FACTORS IN SURFACE ACTIVATION

L. M. Coyne*, R. Mariner and A. Rice

San Jose State University/NASA Ames Research Center

It appears from the fossil record that single-celled terrestrial life forms had proliferated by 0.7-

0.9 b.y. after the formation of the earth. Since impact heating did not end until several hundred

million years after the bulk accretion, a very narrow window has been established for the

complex sequence of precursive chemical processes required to produce, collect and

assemble the organic constituents of cellular life. It has long been recognized by biologists

that surfaces, particularly those with special sites, i.e. phospholipid membranes with protein

receptors and channels, have unique and varied functional properties, including the capacity

to differentially recognize and act to alter or transport materials. It has been even longer

accepted by chemists that solid surfaces have powerful catalytic properties that cannot be

even approximately explained by their bulk chemical composition and structure. By contrast,

the Origin of Life Community has been dishearteningly grudging in its acceptance even of the

concept (much less the need for careful investigation) of the fact that terrestrially abundant

mineral surfaces, particularly those with structural defects, have powerful informational and

energetic properties. Natural surfaces show not only a potential, but a capacity to promote

chemical reactions leading to the synthesis and oligomerization of biologically significant

monomers under conditions that better represent those of early earth than do single phase

models. Homogeneous, single-phase, artificial laboratory models for organic synthesis of

biologically significant molecules still 'rain' supreme from the atmosphere to the soup.

Leading scholars of organic material in comets and interstellar ices still pass off mineral grains

as "inert silicaeous contaminants" with a straight face in the O. of L. and Space Sciences

Communities with scholarly and funding impunity. For some minerals, their complexity is

adequate to sustain membrane, even whole cell, molecular operations of types required to

emulate the functional attributes of living systems. It can be postulated that the specific

adsorption and catalytic powers of these special minerals may prove adequate to adequate to

produce a translation mechanism between inorganic protolife systems and self-organizing

assemblies of organic molecules capable of serving as organic protolife forms.

Clay minerals have been shown to have numerous,curious, energetic properties by virtue of

ultra-violet light release which can be triggered by gentle environmental changes such as

wetting and dewetting by a variety of liquids, unique among them water and hydrazine. Since

both water and hydrazine play multiple key roles in the air-oxidation of hydrazine on kaolinite

surfaces, this reaction would seem to have prime potential for studying interrelationships of

energy storage, release and chemical reactivity of clay surfaces, capacities basic to either the

Bernal or Cairns-Smith roles of minerals in the origin of life. Establishment of the capacity for

stored electronic energy to significantly alter surface chemistry is important, regardless of the

reaction chosen to demonstrate it. Hydrazine air oxidation is overawingly complex, given the

possibilities for step-wise control and monitoring of parameters. In the light of recently

extended characterization of the kaolinite and model sheet catalysts we used to study

hydrazine oxidation, gamma-irradiated silica, previous studies of hydrazine air-oxidation on

aluminosilicate surfaces have been reevaluated. Our former conclusion remains intact that,

whereas trace structural and surface contaminants do play some role in the catalysis of

oxidation, they are not the only, nor even the dominant, catalytic centers. Initial intermediates

in the oxidation can now be proposed which are consistent with production via O--centers as

well as ferric iron centers. The greater than square dependence of the initial reaction rate on

the weight of the clay is discussed in the light of these various mechanistic possibilities.

45
N92-13613 -'

.J

TERRESTRIAL PRODUCTION VS. EXTRATERRESTRIAL DELIVERY

OF PREBIOTIC ORGANICS TO THE EARLY EARTH

C.F. Chyba and C. Sagan

Cornell University,

P.J. Thomas

University of Wisconsin

and

L. Brookshaw

Lawrence Livermore National Laboratory

Since early in this century, it has been speculated that Earth may have accreted much of the

prebiotic organics necessary for the origins of life from impacts of carbonaceous asteroids or

comets. This accretion would have been greatest during the period of heavy bombardment

4.5 to 3.8 Gyr ago. Over the last decade, this potential extraterrestrial source of organic

molecules for the primitive Earth has taken on new importance, as an emerging consensus in

planetary science has replaced previous models of a primordial reducing (CH4/NH3-rich)

terrestrial atmosphere with that of a neutral (002/N2) one, Synthesis of key prebiotic

molecules in CO2 atmospheres has been shown experimentally to be much more difficult than

in reducing ones, with production efficiencies dropping precipitously by many orders of

magnitude as the ration H2/CO2 falls below unity. However, while these results are

suggestive, there is certainly at present no requirement to invoke exogenous organics to

account for the evolution of life on Earth. Many other speculative mechanisms for terrestrial

prebiotic synthesis have been suggested. The goal of investigators at present must be to

quantify as best as possible prebiotic organic production from the various proposed sources,

so that their comparative importance may be weighed. A kind of "balance sheet* for organic

production from different sources in various putative early terrestrial atmospheres may then be

constructed.

A comprehensive treatment of comet/asteroid interaction with the atmosphere, ensuring

surface impact, and resulting organic pyrolysis is required to determine whether more than a

negligible fraction of the organics in incident comets and asteroids actually survived collision

with Earth. Results of such an investigation, using a smoothed particle hydrodynamic

simulation of cometary and asteroidal impacts into both oceans and rock, demonstrate that

organics will not survive impacts at velocities :_ 10 km s-1, and that even comets and asteroids

as small as 100m in radius cannot be aerobraked to below this velocity in 1 bar atmospheres.

However, for plausible dense (10 bar CO2) early atmospheres, there will be sufficient

aerobraking during atmospheric passage for some organics to survive the ensuing impact.

Combining these results with analytical fits to the lunar impact record shows that 4.5 Gyr ago

Earth was accreting at least ~106 kg yr 1 of intact cometary organics, a flux which thereafter

declined with a *.100 Myr half-life. The extent to which this influx was augmented by asteroid

impacts, as well as the effect of more careful modelling of a variety of conservative

approximations, is currently being quantified. These results may be placed in context by

comparison with in situ organic production from a variety of terrestrial energy sources, as well

as organic delivery by interplanetary dust. Which source dominated the early terrestrial

prebiotic inventory is found to depend on the nature of the early terrestrial atmosphere.

However, there is an intriguing symmetry: It is exactly those dense C02 atmospheres where in

situ atmospheric production of organic molecules should be the most difficult, in which intact

cometary organics would be delivered in large amounts.

46
._ ',9 _

SELF ASSEMBLY PROPERTIES OF PRIMITIVE ORGANIC COMPOUNDS

D. W. Deamer*

University of California

A central event in the origin of life was the self-assembly of amphiphilic, lipid-like

compounds into closed microenvironments. If a primitive macromolecular replicating

system could be encapsulated within a vesicular membrane, the components of the

system would share the same microenvironment, and the result would be a step

toward true cellular function. The goal of our research has been to determine what

amphiphilic molecules might plausibly have been available on the early Earth to

participate in the formation of such boundary structures. To this end, we have

investigated primitive organic mixtures present in carbonaceous meteorites such as

the Murchison meteorite, which contains 1-2 percent of its mass in the form of organic

carbon compounds. It is likely that such compounds contributed to the inventory of

organic carbon on the prebiotic earth, and were available to participate in chemical

evolution leading to the emergence of the first cellular life forms.

We found that Murchison components extracted into non-polar solvent systems are

surface active, a clear indication of amphiphilic character (Deamer and Pashley,

Origins of Life and Evolution of the Biosphere 19 (1989) 21-33.) One acidic fraction

self-assembles into vesicular membranes that provide permeability barriers to polar

solutes. Other evidence indicates that the membranes are bimolecular layers similar

to those formed by contemporary membrane lipids. We conclude that bilayer

membrane formation by primitive amphiphiles on the early Earth is feasible. However,

only a minor fraction of acidic amphiphiles assembles into bilayers, and the resulting

membranes require narrowly defined conditions of pH and ionic composition to be

stable. It seems unlikely, therefore, that meteoritic infall was a direct source of

membrane amphiphiles. Instead, the hydrocarbon components and their derivatives

more probably would provide an organic stock available for chemical evolution. Our

current research is directed at possible reactions which would generate substantial

quantities of membranogenic amphiphiles. One possibility is photochemical oxidation

of hydrocarbons. For instance, we have found that pyrene, a major polycyclic aromatic

hydrocarbon of carbonaceous meteorites, acts as a photosensitizer in the

hydroxylation of long chain hydrocarbons. This reaction is significant, in that a nonpolar species (the hexadecane) becomes a surface-active molecule which would be

available to partake in membrane formation.

47
N92-13615

STRUCTURE AND FUNCTIONS OF WATER-MEMBRANE INTERFACES

AND THEIR ROLE IN PROTO-BIOLOGICAL EVOLUTION

A. Pohorille*, M. Wilson, and R. D. MacEIroy

NASA Ames Research Center

Among the most important developments in proto-biological evolution was the

emergence of membrane-like structures. These are formed by spontaneous

association of relatively simple amphiphilc molecules that would have been readily

available in the primordial environment. The resulting interfacial regions between

water and nonpolar interior of the membrane have several properties which made

them uniquely suitable for promoting subsequent evolution. They can a) selectively

attract organic material and mediate its transport, b) serve as simple catalysts for

chemical reactions, and c) promote the formation of trans-membrane electrical and

chemical gradients which could provide energy sources for proto-cells.

Understanding the structure of interfaces, their interactions with organic molecules and

molecular mechanisms of their functions is an essential step to understanding protobiological evolution.

In our computer simulation studies, we showed that the structure of water at interfaces

with nonpolar media is significantly different from that in the bulk. In particular, the

average surface dipole density points from the vapor to the liquid. As a result,

negative ions can approach the interface more easily than positive ions. Amphiphilic

molecules composed of hydrocarbon conjugated rings and polar substituents (e.g.,

phenol) assume at the interface rigid orientations in which polar groups are buried in

water while hydrocarbon parts are located in the nonpolar environment. These

orientational differences are of special interest in connection with the ability of some of

these molecules to efficiently absorb photons. Flexible molecules with polar

substituents often adopt at interfaces conformations different from those in the bulk

aquaeous solution and in the gas phase. As a result, in many instances both

specificity and kinetics of chemical reactions in which these molecules can participate

is modified by the presence of surfaces.

Of special interest is the mechanism by which polar molecules are transferred across

interface between water and a nonpolar medium. Our recent study showed that

simple ionophores bind ions by the same mechanisms as ion channels and carriers

from modern cells. In particular, upon binding the ion these ionophores undergo

change in which their polar groups come into close contact with the ion and get buried

in the interior of the carrier. Simultaneously, groups soluble in oil become exposed to

the surface allowing the complex to penetrate the oily environment of the membrane.

Thus, our study lends support to one of the main concepts in studies of biochemical

evolution: that physico-chemical mechanisms of ubiquitous cell functions remained

similar throughout evolution, but became more accurate and efficient as the molecules

performing these functions gained structural complexity.

48
" N92-13616

MACROMOLECULAR RECOGNITION: STRUCTURAL ASPECTS

OF THE ORIGIN OF THE GENETIC SYSTEM

R. Rein*, D. Barak, N. Luo,

T. J. Zielinski and M. Shibata

Department of Biophysics, Roswell Park Memorial Institute

Theoretical simulation of prebiotic chemical processes is an invaluable tool for probing

the phenomenon of evolution of life. Using computational and modeling techniques

and guided by analogies from present day systems we seek to understand the

emergence of genetic apparatus, enzymatic catalysis and protein synthesis under

prebiotic conditions. In one possible scenario, the RNA enzymatic reaction plays a key

role in the emergence of the self-replicating and offers a clue to the onset of enzymatic

catalysis prior to the existence of the protein biosynthetic machinery. Our ultimate goal

is to propose a simple RNA segment which contains the specificity and catalytic activity

of the contemporary RNA enzyme and which could emerge in a primordial chemical

environment. To understand the mechanism of ribozyme catalyzed reactions ab initio

and semi-empirical (ZINDO) programs were used to investigate the reaction path of

transphosphorylation, A special emphasis was placed on the possible catalytic and

structural roles played by the coordinated magnesium cation..Both the inline and

adjacent mechanisms of transphosphorylation have been studied. Another important

aspect of this reaction is the identity of the functional groups which are essential for the

acid base catalysis. The structural characteristics of the target helices, particularly a

possible role of G°T pair, is under examination by molecular dynamics (MD) simulation

technique.

Modeling of the ancestral aminoacyl-tRNA-synthetases (aRS) may provide important

clues to the emergence of the genetic code and the protein synthetic machinery.

Assuming that the catalytic function evolved before the elements of specific recognition

of a particular amino acid we are exploring the minimal structural requirements for the

catalysis of tRNA aminoacylation. The molecular modeling system SYBYL was used

for this study based on the high resolution crystallographic structures of the present

day tyrosyl-adenylate:tyrRS and tRNAGIn: ATP:glnRS complexes. The trinucleotide

CCA of the 3'-end tRNA is placed into the active site pocket of tyrRS, based on the

scheme of interaction between tRNAGtn and glnRS, and upon the stereochemistry of

the tyrRS:tRNA:Tyr-AMP transition state. This provides a model of the non-specific

recognition of a tRNA's 3'-end by an aRS, which might be similar to that of the

ancestral aRS's. In the next step modeling of the interaction of the rest of the accepter

stem of tRNATy r with tyrRS is carried out.

49
N92-13617 .*

o.J

TEMPLATE POLYMERIZATION OF NUCLEOTIDE ANALOGUES

L. E. Orgel*

The Salk Institute for Biological Studies

Recent work on the template-directed reactions of the natural D-nucleotides has made

it clear that L-nucleotides and nucleotide-like derivatives of other sugars would

strongly inhibit the formation of long oligonucleotides. Consequently, attention is

focusing on molecules simpler than nucleotide that might have acted as the monomers

of an information-transfer system. We have begun a general exploration of the

template-directed reactions of diverse peptide analogues.

I will present work by Dr. Kazuo Harada showing analogues in which phosphate

groups are replaced by carboxylate groups will undergo template-directed

oligomerization provided cyclization is prevented. I will also present work by Dr.

Taifeng Wu on oxidative oligomerization of phosphorothioates and of Dr. Mary Tohidi

on the cyclic polymerization of nucleoside and related cyclic pyrophosphates.

50
N92-13618

PRODUCT AND RATE DETERMINATIONS WITH CHEMICALLY

ACTIVATED NUCLEOTIDES IN THE PRESENCE OF VARIOUS

PREBIOTIC MATERIALS, INCLUDING OTHER MONO- AND

POLYNUCLEOTIDES

A. Kanavarioti*, D. J. Alberas, M. T. Rosenbach, C. F. Bernasconi,

Chemistry Department, University of California, Santa Cruz

and

S. Chang

Planetary Biology Branch, NASA Ames Research Center

Template-directed syntheses of polynucleotides in the absence of enzymes provide a

promising model for the evolution of replicating systems and the concurrent transfer of

information from one generation to the next. In today's enzymatic systems,

polynucleotide synthesis uses the triphosphate mononucleotides as building blocks.

Although these molecules are chemically activated and serve as the energy source in

most biological syntheses, they exhibit a large barrier to non-enzymatic reaction.

Hence, in order to compensate for the large reductions in rates that occur when no

enzyme catalysts are present, modeling experiments are performed with similarly

activated but chemically more labile monomeric precursors. Indeed,

phosphoimidazolide activated nucleotides, so called ImpN's, have found widespread

application in template-directed chemistry.

The most interesting reaction of ImpN's is the template-directed oligomerization in the

presence of the appropriate template. However, the efficiency of this reaction depends

dramatically on the competition with other reactions that consume ImpN's. Therefore

we are investigating the reactions of ImpN's in the presence of a number of

prebiotically plausible materials, such as metal ions, phosphate, amines and other

nucleotides and hope to learn more about the stability/reactivity of ImpN's in a

prebiotic aqueous environment. Although ImpN's hydrolyze readily, we find that, in the

presence of phosphate, ImpN form substantial amounts of diphosphate nucleotides.

These diphosphate nucleotides are not very good substrates for template-directed

reactions, but are chemically activated and are known to revert to the

phosphoimidazolides in the presence of imidazole under solid-state conditions. With

respect to our studies of the oligomerization reaction, the determination of the

dimerization rate constant of a specific ImpN (guanosine 5'-phospho-2-

methylimidazolide) both in the absence and in the presence of the template lead to the

conclusion that at 37°C the dimerization is not template-directed although the

subsequent polymerization steps are. In other words this specific polynucleotide

synthesizing system favors the elongation of oligonucleotides as compared with the

formation of dimers and trimers. This favoring of the synthesis of long as opposed to

short oligonucleotides may be regarded as a rudimentary example of natural selection

at the molecular level.

51
N92-13619 ;

CARBOHYDRATES AS A SOURCE OF ENERGY AND MATTER FOR THE

ORIGIN OF LIFE

A. L. Weber*

The Salk Institute for Biological Studies

One of the most important questions concerning the origin of life is the nature of the

primitive process that provided the chemical energy necessary for the emergence of

biological complexity. We have approached this question by studying chemical

reactions that resemble glycolysis in the way they yield useful chemical energy. The

central role of glycolysis in metabolism plus its ability to function under the anaerobic

conditions of early Earth suggest that it may have provided the energy needed for the

origin of life. Our chemical studies have focused on the first energy-yielding step of

glycolysis involving the oxidation of glyceraldehyde-3-P which initially yields an

'energy-rich' glyceroyl enzyme thioester that drives the synthesis of ATP via a 1,3-

diphosphoglycerate intermediate. Our previous nonenzymatic studies established that

glyceraldehyde oxidation in the presence of a thiol yields 'energy-rich' thioesters and

that thioesters can act as condensing agents for the synthesis of phosphoanhydrides.

Recently, we proposed a new model of early glycolysis in which the oxidation of

glyceraldehyde self-hemiacetals yielded 'energy-rich' polyglyceric acid instead of

'energy-rich' thioesters. In this model, polyglyceric acid not only acts as an energy

source for phosphoanhydride synthesis, but also as an autocatalyst that can replicate

the sequence of D- and L-residues in its structure. We began our investigation of this

new hypothesis the triose model - by developing a thermal method for the

racemization-free synthesis of polyglyceric acid. The hydrolytic stability and the role of

chirality in interactions of polyglyceric acid were studied using this thermal polymer.

Next, we established that the the 2- and 3-glycerol esters of polyglyceric acid are

'energy-rich' by measuring the Gibbs free energy change of hydrolysis (AG °', pH 7) of

the 2- and 3-glycerol esters of 2- and 3-O-L glyceroyl-glyceric acid methyl ester -- a

model of polyglyceric acid. The AG ° of 2- and 3-glycerol esters were -9.1 kcal/mol and

-7.8 kcal/mol, respectively. Recently, we discovered 1) that glyceraldehyde is bound

and oxidized to glyceric acid on the surface of ferric hydroxide, and 2) that soluble

ferric ion catalyzes the rearrangement of glyceraldehyde to lactic acid. We are

exploring the possibility that these reactions could yield polyglyceric acid and

polylactic acid under plausible prebiotic conditions.

52
N92"13620

ON THE ORIGIN AND EARLY EVOLUTION OF BIOLOGICAL CATALYSIS

AND OTHER STUDIES ON CHEMICAL EVOLUTION

J.Oro*

Dept. Biochemical and Biophysical Sciences, University of Houston

and

A. Lazcano

Depto. de Biologia, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico

One of the lines of research in molecular evolution which we have developed for the

past three years is related to the experimental and theoretical study of the origin and

early evolution of biological catalysis. In an attempt to understand the nature of the

first peptidic catalysts and coenzymes, we have achieved the non-enzymatic synthesis

of the coenzymes ADPG, GDPG, and CDP-ethanolamine, under conditions

considered to have been prevalent on the primitive Earth. We have also

accomplished the prebiotic synthesis of histidine, as well as histidyl-histidine, and we

have measured the enhancing effects of this catalytic dipeptide on the

dephosphorylation of deoxyribonucleotide monophosphates, the hydrolysis of oligo A,

and the oligomerization 2',3' cAMP.

On the theoretical side, we have reviewed and further developed the hypothesis that

RNA preceded double-stranded DNA molecules as a reservoir of cellular genetic

information. This has led us to undertake the study of extant RNA polymerases in an

attempt to discover vestigial sequences preserved from early Archean times. So far,

we have been able to develop an evolutionary classification of all extant cellular and

viral RNA polymerases into a few families both on the basis of the amino acid

sequences and function. Moreover, since the "RNA prior to DNA hypothesis" implies

that reverse transcription is a very old phenomenon dating from the Archean Eon, we

have analyzed the substrate specificities of several retroviral reverse transcriptases

(including that of the AIDS virus) and discovered that under slightly modified

laboratory conditions, these RNA dependent DNA polymerases behave as replicases,

that is, as RNA dependent RNA polymerases.

In addition to the above research we have also continued our studies on the chemical

evolution of organic compounds in the solar system and beyond. Hydrogenolysis by

means of deuterium chloride of iron and other metal carbides found in meteorites has

demonstrated the formation of aliphatic hydrocarbons from C1 to C7, an experimental

finding which is in line with the recent observations of homonuclear linear carbon

species in circumstellar clouds.

We have also suggested a simple mechanism for the high enrichment of deuterium

found by other investigators in the amino acids of the Murchison meteorite, and we

have developed arguments for the presence of anaerobic life in Europa in light of

recent discussions about the possibility of a subsurface ocean in this satellite. These

different lines of research in chemical evolution and exobiology have been carried out

with the collaboration of G. Armangue, G. Fox, A. Mar, C. Marquez, T. Mills, and C.

Shen.

53
N9 2- 13 621

CHEMISTRY OF AMINOACYLATION OF 5'-AMP AND

THE ORIGIN OF PROTEIN SYNTHESIS

J.C. Lacey, Jr.*

Department of Biochemistry, University of Alabama at Birmingham

For many years our work centered around understanding the molecular basis for the

origin of the genetic code. As that work progressed, it became more and more obvious

that in order to understand the origin of coding, we needed to understand the origin of

the process of protein synthesis. So, our work in the last few years has shifted to the

study of chemical reactions and interactions related to the process of protein synthesis.

In contemporary protein synthesis, each amino acid is first activated by ATP and

becomes an aminoacyl adenylate anhydride. From that compound, it is passed to

become a 2' (3') ester of the 3' terminal 5'-AMP residue of tRNA. A new peptide bond

is then formed between that amino acid ester and the growing peptide on an adjacent

tRNA.

The chemistry of protein synthesis is thus the chemistry of aminoacyl AMP.

Consequently much of our recent work has been a study of aminoacyl AMP

derivatives. Elucidation of the character of aminoacyl AMP reactions has made it

obvious that AMP (and perhaps other purine monoribonucleotides) has characteristics

which should allow it to preferentially catalyze the synthesis of L-amino acid peptides.

The essential features which lead to this conclusion are: (1) all L-amino acids (but not

all D amino acids) when esterified to 5'-AMP preferentially (65%) distribute to the 3'

position of the 5'-AMP. (2) esterification is predominantly at the 2' position. (3) 2', 3'

diaminoacyl esters are readily formed. (4) a peptide bond can be formed between

adjacent 2', 3' aminoacyl esters.

The experimental data concerning these characteristics of 5'-AMP will be presented

with discussion of how they may have served to direct the origin and evolution of

protein synthesis, including the use of L-amino acids.

54
CATALYTIC RNA AND SYNTHESIS

N92-13622

OF THE I:;I=PTIDE BOND

D. A. Usher*, M. Kozlowski and X. Zou

Department of Chemistry, Cornell University

The existence of catalytic RNA has suggested to some workers that in the earliest

organisms RNA could have been both genetic material and catalyst. Although there

are problems with current theories of how these organisms may have arisen, it is

possible that translation was a relatively late invention by RNA organisms that already

had evolved a considerable degree of biochemical complexity 1. The range of

reactions that RNA is known to catalyze is limited, but it is possible that it once may

have carried a greater variety of functional groups, and therefore may have been able

to catalyze a greater variety of reactions. In collaboration with Tom Cech and Mike

Yarus at the University of Colorado, Boulder, we are studying whether the L-19 IVS

ribozyme from Tetrahymena thermophila can catalyze the formation of the peptide

bond when it is supplied with synthetic aminoacyl oligonucleotides. If this reaction

works, it could give us some insight into the mechanism of peptide bond formation and

the origin or coded protein biosynthesis.

Two short oligoribonucleotides, CCCCC and a protected form of CCCCU were

prepared; the former was made by the controlled hydrolysis of poly(C), and the latter

by multistep chemical synthesis from the protected monomers. The homopentamer

was then aminoacylated using 14C-labelled Boc-protected glycine imidazolide. This

aminoacylated oligo-nucleotide has now been shown to enter the active site of the L19 IVS, and aminoacyl transfer and peptide bond formation reactions are being

sought. Our synthesis of CCCCU made us aware of the inadequacy of many of the 2'-

hydroxyl protecting groups that are in use today and we therefore designed a new 2'-

protecting group that is presently being tested.

1. S.A. Benner and A. D. Ellington, Nature, 329, 295-6 (1987).

55
N92-13623

NEW EVIDENCE FOR A DRAMATIC RISE IN ATMOSPHERE

OXYGEN CA. 1,900 M.Y. AGO

H. D. Holland* and A. W. Macfarlane

Harvard University

The evolution of the oxygen content of the Earth's atmosphere has been tied closely to

the history of the biosphere. Before the advent of life, the 02 content of the atmosphere

must have been vanishingly small. At the beginning of the Phanerozoic, ca. 570 m.y.

ago, PO2 must have been at least 10% of the present 02 level of o.2 atm. During the

past 300 m.y. PO2 was almost certainly more than half and less than twice the present

level. To date, the 02 content of the atmosphere between the origin and life and the

opening of the Phanerozoic has been very poorly constrained. Several lines of

geologic evidence have pointed to a significant increase in P02 about 2,000 m.y. ago,

but the magnitude of P02 before and after that time has been quite uncertain. The data

that we have accumulated recently suggest that PO2 was <2 x 10 -3 atm more than

2,000 m.y. ago, and > 0.03 atm more recently than ca. 1,900 m.y. ago.

These estimates are based on the behavior of iron in Precambrian weathering

horizons. More than ca. 2,000 m.y. ago Fe÷2 released during the weathering of basalts

was not oxidized to Fe ÷3, and was removed in ground water from the upper layers of

soil horizons. More recently than ca. 1,850 m.y. ago, Fe +2 was oxidized to Fe ÷3 and

precipitated as iron oxides and hydroxides in such soil horizons and in the weathering

products of a carbonate facies banded iron formation in Griqualand West, South

Africa. The 02 content of the atmosphere must have increased dramatically about

1,900 m.yl ago to explain these observations. The reasons for the increase are still

obscure, but are probably related to changes in the biologic productivity of the oceans.

Eukaryotes appear to have developed shortly after the increase in PO2, perhaps in

response to the subsequent increase in the supply of nitrate from the atmosphere to

the oceans.

56
BIOSPHERIC-ATMOSPHERIC COUPLING

N92-i3624

ON THE EARLY EARTH

J.S. Levine*

Atmospheric Sciences Division, NASA Langley Research Center

Over the history of our planet, the production of gases within the biosphere and their

release into the atmosphere have had a very significant impact on the composition

and chemistry of the global atmosphere. Important atmospheric gases produced in the

biosphere include oxygen (02), nitrous oxide (N20), nitric oxide (NO), methane (CH4),

and ammonia (NH3). Photochemical calculations have been performed to assess the

relationship between the magnitude of the biospheric source of these gases and their

atmospheric abundance in the oxygen-free and later oxygen-evolving atmosphere.

The evolution of oxygen in the atmosphere impacted the composition and chemistry of

the atmosphere in several different ways: (1) Oxygen controlled the origin and

evolution of atmospheric ozone (03), (2) Oxygen and ozone control the rates of

molecular photolysis in the ultraviolet, and, hence, control many photochemical

processes in the atmosphere, (3) Oxygen controls the oxidation state of the biosphere

and, hence, controls the chemical nature of the production of gases, i. e., oxidizing vs.

reducing gases, and (4) The origin of atmospheric oxygen led to the possibility of

lightning-inducing fires, a significant source of many atmospheric gases, including

carbon dioxide, carbon monoxide, methane, nonmethane hydrocarbons, and nitric

oxide.

Theoretical calculations performed with a one-dimensional photochemical model have

been performed to assess the biospheric-atmospheric transfer of gases. Ozone

reached levels to shield the Earth from biologically lethal solar ultraviolet radiation

(220-300 nm) when atmospheric oxygen reached about 1/10 of its present

atmospheric level. In the present atmosphere, about 90 percent of atmospheric nitrous

oxide is destroyed via solar photolysis in the stratosphere with about 10 percent

destroyed via reaction with excited oxygen atoms. The reaction between nitrous oxide

and excited oxygen atoms leads to the production of nitric oxide in the stratosphere,

which is responsible for about 70 percent of the global destruction of oxygen in the

stratosphere. In the oxygen-/ozone-deficient atmosphere, solar photolysis destroyed

about 100 percent of atmospheric nitrous oxide, relegating the production of nitric

oxide via reaction with excited oxygen to zero. Our laboratory and field measurements

indicate that atmospheric oxygen promotes the biogenic production of N20 and NO via

denitrification and the biogenic production of methane by methanogenesis.

57
N92-13625

A WINDOW IN TIME FOR THE FIRST EVOLUTIONARY RADIATION

H. J. Morowitz

George Mason University

The window in time between the last globally sterilizing event and the evidence for a

complex procaryotic ecosystem is quite narrow, perhaps as small as 200 million years.

We will present a heuristic model outlining the first evolutionary radiation that could

have led from primordial vesicles to the universal ancestor. The concept of the

universal ancestor will be developed in terms of contemporary molecular biology.

58
EARLY EVQLUTION OF LIFE;

THE BIOLOGICAL RECORD

Chairman - L. I. Hochstein

The evolutionary record occurs in two forms: as the familiar fossil record in rocks, in

which phylogeny is deduced from morphology, and in the genome of extant

organisms, where mutational events, which are the stuff of evolution, are expressed in

sequences found in the organism's nucleic acids, or the gene products. The

presentation in this Symposium which addressed the early evolution of life reflected

studies at the level of the metabolic pathway; investigations of evoltuion at the

structural and functional levels; and finally investigations at the molecular level with

particular emphasis on sequence data obtained from proteins and nucleic acids.

L. Jahnke described studies on the evolution of oxygen-requiring metabolic systems.

The transition between oxygen-independent and oxygen-dependent systems may

correlate the evolution of these processes with the appearance of oxygen. Hopanoids

(whose synthesis does not require oxygen and which are only found in prokaryotes)

have been suggested to be evolutionary precursors of sterols (whose biosynthesis

requires oxygen and are found in prokaryotic and eukaryotic cells). Methane oxidizing

bacteria contain both of these cyclic triterpenes suggesting that these organisms may

be useful for studying the evolution of the biosynthetic pathway for sterol synthesis.

These studies characterized the relative distribution of the hopanoids and sterols

within the complex membrane systems of the methane oxidizing bacterium,

Methylococcus ca0sulatus, and the effect of temperature on the fatty acid and sterol

composition of the cells. The sterol and fatty acid content decreased as the

temperature was raised whereas the hopanoid content was unaffected suggesting that

sterols and hopanoids affect membrane function by regulating membrane fluidity.

L.I. Hochstein reported on a continuation of his studies on the membrane-bound

ATPase from the Archaebacterium Halobacterium saccharovorum. There are two

major classes of proton-translocating ATPases: the so-called F-type (or ATP

Synthases), which are associated with the cytoplasmic membranes of bacteria and the

membranes from thylakoids and mitochondria; and the V-type (or vacuolar) which are

found in the endomembranes systems which occur in Eukaryotic cells. These two

classes of ATPases appear to have arisen from a common ancestral enzyme. It has

been suggested that Archaebacterial ATPases are V-type ATPases, although this

hypothesis is based on the data obtained from a single Archaebacterium, the sulfurdependent acidophilic thermophile, Sulfolobus acidocaldarius. The studies from

Hochstein's laboratory indicate that the ATPase from the extremely halophilic

Archaebacterium, H. saccharovorum, possesses properties characteristic of F- and Vtype ATPases and suggest that this enzyme may be an intermediate in the evolution of

these two classes of proton-translocating ATPases.

J. Lanyi reported on a new research direction undertaken in his laboratory with respect

to the retinal pigments found in the extremely halophilic bacteria. These pigments,

which are exclusively found in the extreme halophiles, carry out a unique form of

59

Dii!_
energy transduction in which light energy is converted into a chemical gradient of

protons. This process represents a more primitive method of "photosynthesis" than

the more commonly known chlorophyll-based system. J. Lanyi also reported on the

successful cloning of the gene for halorhodopsin, a phototransducing pigment which is

involved in chloride transport. Sequence comparison of the genes for

bacteriorhodopsin and halorhodopsin from H. _, and halorhodopsin from

Natronobacterium _ indicate while there is considerable evolutionary

distance between these genes, there is significant similarity. It was concluded that

there has been strong selective pressure present during the evolution of these

phototransducing pigments.

R. Buchanan described a phylogenetic scheme for the evolution of photosynthesis.

The marker chosen, the thioredoxins, are small, photochemical reducible, proteins.

There are 2 types, thioredoxin .t and rn which have different functional and structural

properties. Amino acid sequence studies indicate significant homology between the

m-type thioredoxins from plants and bacteria. Thioredoxin f appears distantly related

to bacterial thioredoxin. A phylogenetic tree constructed for the thioredoxins indicated

that those from bacteria and animals fall into discrete groups. The chloroplast

thioredoxins show two patterns: one, the m-type, resembles thioredoxins from algae

and bacteria. The f-type thioredoxin shows a close relationship to animal thioredoxins.

One issue to understanding how to use sequence data (either nucleic acid or protein)

is related to the rate with which changes take place. George Fox described studies

related to this issue with respect to the use of ribosomal RNA as molecular

phylogenetic markers. The rationale considers that the nucleotide sequence of an

RNA molecule reflects a particular function, and that such sequences represent one of

many that may occupy a larger domain, or structure space. If RNA molecules within a

structure space are homogeneous, the rate of evolution would predictably be uniform

whereas if they are heterogeneously distributed, mutation rates would be dependent

on sequence and mutations not be uniform. Preliminary experiments involved

developing an artificial plasmid containing a 5s rRNA gene. A series of mutants were

prepared for testing the relative homogeneity of a particular structure space.

R. Krestsinger described a comparison of a number of calcium-binding proteins.

Analysis suggested that these calcium-binding proteins could be described by

fourteen discrete groupings. The results of these studies indicate that the ability to

bind calcium was lost and acquired a number of times. The rate of evolution of these

proteins within the group appeared to be much slower than prior to the formation of the

particular group.

J. Troust reported on studies whose goal is to characterize the early evolution of

photosynthesis. The approach is to examine the photosynthetic reaction centers in an

organism belonging to the genus Heliobacterium that contain the simplest known such

centers. These reaction centers appear to have arisen from a progenitor that also

gave rise to photosystem I which is found in oxygen-evolving photosynthetic

organisms. The centers were isolated and were found to contain a peptide that bound

photoreactive chlorophyll and bacteriochlorophyll g.

60
S. Fox sutnmarized studies which implicate thermal proteins as possessing the ability

to store and transfer biological information. The notion is that amino acids have an

inherent self-sequencing capacity. Data was presented to account for the origin of the

cells, including such essential characteristics as membranes and metabolic

processes.

G. Hinkle presented information with respect to the hypothesis for the symbiotic origin

of cilia, flagella, and the mitotic spindle from spirochetes.

The biological studies supported by the program in the early evolution of life are

characterized by an increasing degree of sophistication. Although not at first obvious,

a large number of the research projects are connected. The unifying theme is the

evolution of energy-transducing systems as evidenced by the studies of chemical

transducers (i.e. ATPases) and photochemical transducers (i.e. the retinal pigments of

the extreme halophiles, the reaction centers of the heliobacter, and the diverse

thioredoxins). Finally, G. Fox's studies are a novel approach directed toward a better

understanding as to what determines the rate of mutation (i.e evolution).

61
:N92-13626

THE EFFECTS OF OXYGEN ON THE EVOLUTION OF MICROBIAL

MEMBRANES

L. L. Jahnke*

NASA Ames Research Center

Extant microorganisms are an invaluable resource for furthering our understanding of

Earth's evolution. Perhaps the greatest influence on this process has been the rise in

levels of free oxygen. While the roots of biochemical pathways are anaerobic,

oxygenase-type mechanisms did evolve once sufficient molecular oxygen was

available. The products of these oxygen-requiring syntheses are more characteristic

of eukaryotic organisms and must have been particularly important for the

development of these more highly evolved cells. In a number of cases, examples of

this evolutionary transition exist in extant prokaryotes and are of importance to

furthering our understanding of cellular evolution. This is particularly true for the

biosynthesis of sterols and hopanoids. With few exceptions, sterols are a ubiquitous

constituent of eukaryotic membranes, however, only a few prokaryotes are known to

synthesize them. Hopanoids, on the other hand, are present in many bacteria. Both

compounds are cyclic triterpenes, products of the cyclization of squalene. While

hopanoid synthesis is anaerobic, sterol synthesis involves several oxygen-requiring

enzymes. Ourisson has suggested that hopane polyols are primitive analogues of the

sterol molecule acting as membrane stabilizers, and, indeed, model membrane

studies have suggested that hopanoids may perform a cholesterol-like function in

bacterial membranes. One prokaryote, Methvlococcus caD_latus, synthesizes both

hopanoids and sterols and, thus, provides a Unique opportunity to study the evolution

of membrane function.

Methane-oxidizing bacteria, such as M. ca osulatus, are characterized by the presence

of three potentially distinct membrane systems: an outer, cell boundary layer; an inner

or pericytoplasmic layer; and an extensive intracytoplasmic membrane system. When

the outer and cytoplasmic membranes of this organism were separated by sucrose

density centrifugation, lipid analysis showed that the sterol and hopane polyol (the

principal hopanoid in this organism) were associated predominantly with the outer

membrane. The molar ratio of phospholipid to hopane or sterol in the cytoplasmic

membrane was approximately 30:1, similar to the ratio for whole cells. However, the

ratios for outer membrane were 11:1 for hopane and 6:1 for sterol. When M.

was grown at different temperatures, lipid analysis of the whole cells

showed that both sterol and unsaturated fatty acid levels decreased at higher growth

temperatures; sterol concentrations were 0.116 p.mole/l_mole phospholipid at 30°C

and 0.025 I_mole/p.mole phospholipid at 45°C, while the saturated to unsaturated fatty

acid ratio increased from 0.397 to 1.475. Hopane polyol levels were constant over this

temperature range, however, methylation of the A-ring (a characteristic modification of

the hopane molecule in some methane-oxidizers) decreased markedly in cells grown

at 30°C. These results imply that sterol and hopane molecules are required for

enhancement of some specific membrane function, potentially by modulating

membrane fluidity.

62
k3 '

ON THE CHIMERICAL NATURE OF THE MEMBRANE-BOUND ATPASE

FROM

HALOBACTERIUM SA_HAROVORUM

L. I. Hochstein*

Planetary Biology Branch, Ames Research Center

There is increasing evidence that proton translocating ATPases evolved from a

progenitor that had the structural characteristics of vacuolar ATPases (V-ATPases) but,

unlike this class of enzymes, was capable of synthesizing ATP. Interestingly, the

Archaebacteria, a diverse collection of organisms that diverged from the Prokaryotes

at an early stage in the evolution of life, possess ATPases more closely related to VATPases than to FoF1-ATPases(F-ATPases).

However, an antiserum against the "B" subunit from S. acidocaldarius reacts with the

13subunit from an F-ATPase as well as subunit II from Halobacterium saccharovorum

ATPase (subunit II is probably the functional equivalent to the 13subunit). This

communication describes a series of experiments carried out with the goal of

determining how the membrane-bound ATPase from H. saccharovorum is related to Vand F-type ATPases, and reflect three approaches: the use of inhibitors; structural

studies; and immunological relatedness.

Nitrate is extremely useful for distinguishing between V- and F-ATPases since only the

former are inhibited by this reagent. The enzyme from H. saccharovorum is also

inhibited by nitrate and at concentrations that inhibit V-ATPases and ATPases from

other Archaebacteria. N-ethylmaleimide, which inhibits V- and F-ATPases, also

inhibits the ATPase from H. saccharovorum. However, whereas V-type enzymes are

inhibited by _M concentrations of this reagent, F-type and the halobacterial enzyme

are inhibited by mM concentrations of NEM. 4-chloro-7-nitrobenzofurazan, a

nucleotide analog, inhibits V-, F-, and the halobacterial ATPases. In the case of the VATPases inhibition is accompanied by the binding of the inhibitor to the largest of the

subunits, which is the catalytic subunit. 4-chloro-7-nitrobenzofurazan binds to the 13-

subunit of F-ATPases, which is the catalytic subunit. 4-chloro-7-nitrobenzofurazan

binds to subunit II of the halobacterial enzyme, which also contains the

dicylcohexylcarbodiimide-binding site. In spite of this apparent similarity, the

halobacterial enzyme is unrelated to F-type ATPases based on a comparison of the

isoelectric points, the amino acid compositions, the molecular mass, and the

proteolytic products of the two largest subunits from each enzyme. Furthermore,

antisera prepared against the largest subunit from the V-ATPase from _lg.._E.._D_g..[a

crassa reacts with subunit I from the halobacterial enzyme. On the basis of these

observations, the halobacterial enzyme may represent a chimera. Subunit II appears

to be immunologically and functionally related to the 13subunit from F-ATPases. On

the other hand, subunit I may be structurally related to the largest of the largest

subunits from V-ATPases but possibly functionally related to the (z-subunit from FATPases (which has a regulatory function). Whether this reflects the nature of the

progenitor enzyme or mixture of structure and function which arose after the evolution

of the proton ATPases into V- and F-type enzymes is not clear, but it is another

example of the evolutionary richness of the extremely halophilic bacteria.

63
N92-13628

ARCHAEBACTERIAL RHODOPSIN SEQUENCES:

EVOLUTION

IMPLICATIONS FOR

J. K. Lanyi*

University of California

It has been proposed over 10 years ago that the archaebacteria represent a separate

kingdom which diverged very early from the eubacteria and eukaryotes. It follows,

therefore, that investigations of archaebacterial characteristics might reveal features of

early evolution. Yet, the phylogeny of the archaebacteria and its constituent groups is

still subject to controversy. Few archaebacterial genes which code for proteins, and

could begin to help in deciding these important issues, have been sequenced so far.

The bacterial rhodopsins are found in halophilic archaebacteria, and constitute a

relatively well characterized group of membrane proteins. So far, two genes, one for

bacteriorhodopsin and another for halorhodopsin, both from Halobacterium halobium,

have been sequenced. We cloned and sequenced the gene coding for the

polypeptide of another one of these rhodopsins, a halorhodopsin in Natronobacterium

pharaonis (named here pharaonis halorhodopsin). Peptide sequencing of cyanogen

bromide fragments, and immuno-reactions of the protein and synthetic peptides

derived from the C-terminal gene sequence, confirmed that the open reading frame

was the structural gene for the pharaonis halorhodopsin polypeptide. The flanking

DNA sequences of this gene, as well as those of other bacterial rhodopsins, were

compared to previously proposed archaebacterial consensus sequences. In pairwise

comparisons of the open reading frame with DNA sequences for bacterio-opsin and

halo-opsin from Halobacterium halobium, silent divergences (mutations/nucleotide at

codon positions which do not result in amino acid changes) were calculated. These

indicate very considerable evolutionary distance between each pair of genes, even in

the dame organism. In spite of this, the three protein sequences show extensive

similarities, indicating strong selective pressures.

64
THIOREDOXIN AND

2" 13 629

EVOLUTION

B. B. Buchanan*

University of California

Thioredoxins are a widely distributed group of small proteins with a conserved dithiol

active site. Chloroplasts contain two types of thioredoxin (.tand m) for which functional

differences coincide with differences in structure. These thioredoxins, which are both

reduced photochemicaily by way of ferredoxin and ferredoxin-thioredoxin reductase,

regulate biochemical activity in chloroplasts in response to light by reducing specific

target enzymes and changing their activities. Thioredoxin .f.preferentially activates

enzymes of the photosynthetic carbon cycle (fructose bisphosphatase, sedohepulose

bisphosphatase, phosphoribulokinase, NADP-glyceraldehyde 3-P dehydrogenase).

Thioredoxin m preferentially activates an associated enzyme, NADP-malate

dehydrogenase, and deactivates, also apparently by enzyme reduction, an enzyme of

carbonate breakdown (glucose 6-P dehydrogenase). Both thioredoxins interact with

CF1-ATPase, the enzyme forming ATP. Recently the regulatory thiol site has been

identified for most of these enzymes. In each case, a specific disulfide (S-S) group is

reduced to the sulfhydryl (SH) level, leading to the activation of the enzyme. This

redox modulation enables chloroplasts to use light for the regulation of these

enzymes, thereby achieving "biochemical order"--i.e., futile cycling is minimized so that

starch can be built up in the light and broken down in the dark.

Comparisons of primary structure have revealed significant homology between the m

type thioredoxins of chloroplasts and the thioredoxins from a variety of bacteria.

Chloroplast thioredoxin L by contrast, remains an enigma: certain residues are

invariant with those of other thioredoxins, but a phylogenetic relationship to bacterial

or m thioredoxins seems distant. Knowledge of the evolutionary history of thioredoxin t

is, nevertheless, of interest because of its role in photosynthesis. We have, therefore,

attempted to gain information on the evolutionary history of chloroplast thioredoxin t.,

as well as El.. Our goal was first to establish the utility of thioredoxin as a phylogenetic

marker, and, if found suitable, to deduce the evolutionary histories of the chloroplast

thioredoxins. To this end, we have constructed phylogenetic (minimal replacement)

trees using computer analysis. The results show that the thioredoxins of bacteria and

animals fall into distinct phylogenetic groups--the bacterial group resembling that

derived from earlier 16s RNA analyses and the animal group showing a cluster

consistent with known relationships. The chloroplast thioredoxins show a novel type

of phylogenetic arrangement: one (m type) aligns with its counterpart of eukaryotic

algae, cyanobacteria and other bacteria, whereas the second (I type) tracks with

animal thioredoxin. The results give new insight into the evolution of photosynthesis.

65
EXPLORATION OF RNA

N92"13630 I,

STRUCTURE SPACES

G. E. Fox

University of Houston

Studies in molecular phylogeny have relied heavily on ribosomal RNAs to establish

relationships between extant organisms and to identify the earliest branchings. These

ribosomal RNAs are major components of the ribosomal machinery whose

development was central in the early development of life. The role of RNAin early

evolution may be even more general however, as even small RNAs have the potential

to carry genetic information while exhibiting catalytic activity. At this stage it is

essential to understand how an RNA molecule can respond to the evolutionary

processes. This will provide insight to the reliability of early branching patterns

detected in phylogeny studies and reveal how more complex structures can evolve

from simpler ones.

RNA molecules of any particular function are perceived as a set of primary sequences

that satisfy the biological conditions for that RNA. The set of such sequences for any

particular RNA is a subset of sequence space that is referred to as structure space.

Over evolutionary time, an RNA molecule explores its current structure space as long

as it retains its biological function. Changes in function and/or increases in complexity

require transition to a different structure space. In order to understand RNA evolution,

it is essential to understand how the sequences comprising a typical structure space

are related. If, for example, they are homogeneously distributed, then each has

essentially the same number of equally accessible neighbors and the rate of the

evolutionary process would be uniform. In contrast, in a heterogeneous structure

space the probability of mutations being accepted is strongly dependent on current

sequence and hence rates are not necessarily uniform.

In order to examine the structure of real structure spaces we are studying the 5S rRNA

structure space experimentally. A plasmid containing a synthetic 5S rRNA gene, two

rRNA promoters, and transcription terminators has been assembled. Assays are

conducted to determine if the foreign 5S rRNA is expressed, and to see whether or not

it is incorporated into ribosomes. Evolutionary competition is used to determine the

relative fitness of strains containing the foreign 5S rRNA and a control 5S rRNA. By

using site directed mutagenesis a number of mutants can be made in order to study

the boundaries of the structure space and how sharply defined they are. By making

similar studies in the vicinity of several points of structure space, it will be possible to

determine how homogeneous the 5S rRNA structure space is. Useable experimental

protocols have been developed, and a number of mutants have already been studied.

Initial results suggest an explanation of why single stranded regions of the RNA are

less subject to mutation than double stranded regions.

66
N92=13631

FUNCTIONAL CHARACTERISTICS OF THE CALCIIJM MODULATED

PROTEINS SEEN FROM AN EVOLUTIONARY PERSPECTIVE

R. H. Kretsinger*, S. Nakayama and N. D. Moncrief

Department of Biology, University of Virginia

We have constructed dendrograms relating 173 EF-hand proteins of known amino acid

sequence. The EF-hand, or calmodulin fold, consists of 29 amino acids -- 1-10 in helix E;

calcium coordinating side chains 10 X, 12 Y, 14 Z, 18 -X, 21 -Z; and 21-29 in helix F. This

homolog domain is present in from two to eight random repeats in (nearly) all calciummodulated proteins in the cytosol. The intradomain regions are much more highly conserved

than the interdomain regions. We aligned all of these proteins by their EF-hand domains,

omitting interdomain regions. Initial dendrograms were computed by minimum mutation

distance methods. Using these as starting points we determined the best dendrogram by the

method of maximum parsimony, scored by minimum mutation distance.

We identified fourteen distinct subfamilies as well as six unique proteins (indented), perhaps

the sole representatives of other subfamilies:

Name Ca-binding in Domains 1 2 3

Calmodulin

Troponin C

Troponin C (_

Parvalbumin

Calbindin

Calcineudn B

Sl00

Essential Light Chain of Myosin

Calcium Vector Protein

Regulatory Light Chain of Myosin

Caltractin & CDC31

Stron_olvocentrotus ectodermal prot.

co-Actinin

25 kDa Protein (.T__)

Ca-binding protein (1,_)

Sarcoplasm Ca-binding Protein

Ca-binding Protein _) +

Aequorin +

Calpain +

Ca-binding Protein (Canis thyroid) +

4-

+/-

4-

4-

+/-

4-/-

4-

4-

4-

+/-

4-

4-

4-

4 5 6

+ +/? +/?

+ +/- +

4- - +

4- +

4- 4- 4-

4- 4- 4-

+/-

+/- +/-

+ +

+/- +/- +

+/? +/? +

+/-

+ ? +

4- 4- 4-

+I- +/- +/-

? + +

4- 4-

4-

+ + ?

Within subfamilies, one can easily align interdomain regions. The resulting dendrograms are

very similar to those computed using domains only. Dendrograms constructed using pairs of

domains show general congruence. However, there are enough exceptions to caution

against an overly simple scheme in which a pair of gene duplications leads from a one

domain precursor to a four domain prototype from which all other forms evolved. The ability to

bind calcium was lost and acquired multiple times during evolution.

The distribution of introns does not conform to the dendrogram based on amino acid

sequences.

The rates of evolution appear to be much slower within subfamilies, especially within

calmodulin, than those prior to the definition of subfamily.

67
PHOTOSYNTHETIC REACTION CENTER

HELIOBACTERIA

N92-13632,.1,

COMPLEXES FROM

J. T. Trost, W. F. J. Vermaas and R. E. Blankenship*

Center for the Study of Early Events in Photosynthesis,

Arizona State University

Photosynthetic reaction centers are pigment-protein complexes that are responsible

for the transduction of light energy into chemical energy. Considerable evidence

indicates that photosynthetic organisms were present very early in the evolution of life

on Earth. The goal of this project is to understand the early evolutionary development

of photosynthesis by examining the properties of reaction centers isolated from certain

contemporary organisms that appear to contain the simplest photosynthetic reaction

centers. The major focus of this project is the family of newly discovered strictly

anaerobic photosynthetic organisms known as Heliobacteria. These organisms are

the only known photosynthetic organisms that are grouped with the gram-positive

phylum of bacteria. The properties of these reaction centers suggest that they may be

the descendants of an ancestor that also gave rise to Photosystem I found in oxygenevolving photosynthetic organisms.

Photoactive reaction center-core antenna complexes have been isolated from the

photosynthetic bacteria Heliobacillus mobili$ and Heliobacterium gestii by extraction

m" membranes with Deriphat 160C followed by differential centrifugation and sucrose

density gradient centrifugation (Trost and Blankenship, Biochemistry 28, 9898-9904,

1989). The purified complexes contain one or more 48,000 Mr peptides that bind both

the photoactive chlorophyll P800 and approximately 25 molecules of antenna

bacteriochlorophyll g. Time-resolved fluorescence spectroscopy indicates that the

antenna pigment are active in energy transfer to P800, exhibiting a major decay time

of 25 ps in both membranes and reaction centers. The absorption and fluorescence

properties of membranes and reaction centers are almost identical, suggesting that a

single pigment-protein complex serves as both antenna and reaction center.

Experiments in progress include sequence determination of the 48,000 Mr reaction

center protein, and evolutionary comparisons with other reaction center proteins.

These experiments are being done using chemical sequencing methods to obtain a

partial sequence, followed by oligonucleotide synthesis and DNA hybridization to

obtain the gene(s) for the protein(s).

68
MOLECULAR BASES FOR UNITY AND DIVERSITY IN ORGANIC

EVOLUTION

S. W. Fox*, P. Ruecknagel, and G. Braunitzer+

Departments of Engineering and Plant Biology, Southern Illinois University/

Max Planck Institute for Biochemistry

The origin of biological information on the Earth has been ascribed at various times to

DNA, RNA, or protein. The origin of nucleic acids without the action of prior informed

protein has not been supported by plausible experiments, although such possibilities

have been examined (e. g. Schwartz and Fox, 1964). DNA synthesis has been

assigned to a distant unnamed planet (Crick, 1981). The fallacies of concepts

involving RNA in this context, despite demonstrated catalytic activity (Cech, 1983),

have been reviewed by Waldrop (1989) and Fox (1984).

The one experimentally based explanation for the origin of biological information is the

endogenously ordered synthesis of thermal proteins due to the stereoelectronic

specificities of the types of precursor amino acid (Fox and Dose, 1972). This method

of selfsequencing of amino acids and its results have been described in numerous

reports (summaries in Fox, 1981; Dose, 1984; Melius, 1982). Moreover, Ivanov and

Foertsch (1986) have accumulated data from the Martinsried protein primary

sequence data bank that indicate the selfsequencing of amino acids is part of the

ordering mechanism in modern protein synthesis.

The behavior of the thermal proteins and of the microspheres selfassembled therefrom

explain the origin of the first cells, the first membrane, the first reproduction cycle,

ancient metabolism including ATP-aided syntheses of peptides and polynucleotides,

growth, bioelectricity, and of polybiofunctionality in general (Fox, 1980, 1989). Closer

study of the products of heating mixtures of amino acids may explain evolutionary

origins of unity and diversity in thermal proteins and in organisms.

+ Deceased, 1989

69
. 92-13634 .J

SEDIMENTARY ORGANIC MOLECULES: ORIGINS AND INFORMATION

CONTENT

J. M. Hayes* and K. H. Freeman

Biogeochemical Laboratories, Indiana University

Improved knowledge of ancient redox levels and of CO2 abundances is crucial to

correct reconstruction of earth's environmental history. Much relevant information

must be encoded in the sedimentary record of organic carbon. The presence of

organic material in sediments is commonly considered in terms of "preservation," in

the sense that some organic debris has escaped recycling. That ultimately

immobilized in sedimentary rocks, however, is the product of an ecosystem devoted to

utilization - not preservation - of organic material. Although it is interesting to think in

terms of the fraction of primary organic carbon that winds up in sedimentary rocks, use

of the primary production as the reference point directs attention away from most of the

action. Nearly all carbon-carbon bonds established in primary production are broken

as plant products and utilized within the food chain. Organic geochemistry, sometimes

described as "molecular paleontology," deals with the complex mixture of products

deriving from these processes. Each organic compound represents only a tiny part of

the parent organism. Extending the analogy, we must acknowledge that the fossils

have been disarticulated and scrambled.

To progress, we must dissect the processes controlling the composition of sedimentary

organic matter. Structurally, this has proven difficult. Individual "biomarkers" can often

be recognized, but their contribution to total organic matter is small, and their presence

does not imply that their biochemical cell mates have survived. We are finding,

however, that a combination of structural and isotopic lines of evidence provides new

information. A starting point is provided by the isotopic compositions of primary

products (degradation products of chlorophylls, alkenones derived from coccoliths).

We find strong evidence that the isotopic difference between primary carbonate and

algal organic material can be interpreted in terms of the concentration of dissolved

CO2. Moreover, the isotopic difference between primary and total organic carbon can

be interpreted in terms of characteristic isotopic shifts imposed by secondary

processes (responsive, for example, to 02 levels in the depositional environment). In

favorable cases, isotopic compositions of a variety of secondary products can be

interpreted in terms of flows of carbon, and, therefore, in terms of specific processes

and environmental conditions within the depositional environment.

70
N92-13635.

EARLY ARCHEAN STROMATOLITES: PALEOENVlRONMENTAL SETTING

AND CONTROLS ON FORMATION

D. R. Lowe*

Department of Geology, Stanford University

The earliest record of terrestrial life is contained in thin, silicified sedimentary layers

within enormously thick, predominantly volcanic sequences in South Africa and

Western Australia. This record includes bacteria-like microfossils, laminated

carbonaceous structures resembling flat bacterial mats and stromatolites, and a

morphologically diverse assemblage of carbonaceous particles. These structures and

particles and their host sediments provide the only direct source of information on the

morphology, paleoecology and biogeochemistry of early life; the nature of interactions

between organisms and surface systems on the early earth; and possible settings

within which life might have evolved.

The three known occurrences of 3.5 to 3.2 billion-year-old stromatolites have been

evaluated in terms of depositional setting and biogenicity. All occur within

sedimentary units deposited in shallow, probably marine waters on large, low-relief,

oceanic volcanic platforms. Hawaii provides perhaps the best modern analog.

Evaporitic sediments are common components of these sequences. Associated, offplatform, deep-water deposits commonly contain abundant detrital carbonaceous

matter but appear to lack in situ bacterial mats or stromatolites. This environmental

specificity of early bacterial communities represents perhaps the most convincing

evidence yet reported that they included photosynthetic organisms. The morphology

of small conical stromatolites in the Strelley Pool Chert, Western Australia, appears to

have been controlled mainly by precipitative processes in hypersaline waters. The

well-known stromatolite from the North Pole, Western Australia, consisting of a single

specimen that includes one partial stromatolite, probably represents a chunk of flat

bacterial mat deformed by soft-sediment movement and the post-depositional growth

of evaporitic carbonate or gypsum nodules. Stromatolites in the Barberton

Greenstone Belt, South Africa, formed at least in part by inorganic precipitation and

resemble siliceous sinter. They apparently developed by silica precipitation in waveand current-active shallow-water areas fringing the volcanic platforms. Although all of

these early Archean stromatolites appear to have been formed at least in part by

inorganic, commonly precipitative processes, there is also some evidence that they

were covered by active bacterial mats during growth. This may simply reflect passive

biological opportunism. It seems plausible, however, that the surficial mats played an

important role in controlling local microenvironments and influencing if not mediating

precipitation. This could reflect a more active strategy involving the coupling of

biological and inorganic processes to produce structures on the shallow sea floor that

enhanced community survival.

71
N92-13636

EARLY ARCHEAN (-3.4 Ga) PROKARYOTIC FILAMENTS FROM

CHERTS OF THE APEX BASALT, WESTERN AUSTRALIA:

THE OLDEST CELLULARLY PRESERVED MICROFOSSILS NOW KNOWN

J. W. Schopf*

Department of Earth and Space Sciences, Institute of Geophysics and Planetary

Physics, Center for the Study of Evolution and the Origin of Life

University of California

In comparison with that known from later geologic time, the Archean fossil record is

miniscule: although literally hundreds of Proterozoic formations, containing more than

2800 occurrences of bona fide microfossils, are now known, fewer than 30 units,

containing some 43 categories of putative microfossils (the vast majority of which are

of questionable authenticity), have been reported from the Archean. Among the oldest

fossils now known are Early Archean filaments reported from cherts of the Towers

Formation (Awramik et al., 1983) and the Apex Basalt (Schopf and Packer, 1987) of

the 3.3-3.6 Ga-old Warrawoona Group of Western Australia. The paleobiologic

significance of the Towers Formation microstructures is open to question" thin

aggregated filaments described by Awramik et al. are properly regarded as

"dubiomicrofossils" -- perhaps biogenic, but perhaps not -- and they therefore cannot

be regarded as firm evidence of Archean life. And although authentic, filamentous

microfossils were reported by Awramik et al. from a second Towers Formation locality,

because the "precise layer" containing the fossiliferous cherts "has not been relocated"

(Awramik et al., 1983, 1988), this discovery can neither be reconfirmed by the original

collector nor confirmed independently by other investigators.

Discovery of microfossils in bedded cherts of the Apex Basalt (Schopf and Packer,

1987), the stratigraphic unit immediately overlying the Towers Formation, obviates the

difficulties noted above. The cellularly preserved filaments of the Apex Basalt meet all

of the criteria required of bona fide Archean microfossils: (j.) they occur in rocks of

unquestionably Archean age; (ii) they are demonstrably indigenous to these Archean

sediments; (ii._) they occur in lithic clasts that are assuredly syngenetic with deposition

of this sedimentary unit (with the fossils themselves pre-dating deposition of the

bedded cherts in which the clasts occur); (iv) they are certainly biogenic; and (v) as

demonstrated by replicate sampling of the fossiliferous outcrop, the provenance of

these microfossils is known with certainty. Recent studies indicate that the Apex

assemblage includes at least six morphotypes of uniseriate filaments, composed of

barrel-shaped, discoidal, or quadrate cells and exhibiting rounded or conical terminal

cells and medial bifurcated and paired half-cells that reflect the occurrence of

prokaryotic binary cell division. Interestingly, the majority of these morphotypes are

morphologically more similar to extant cyanobacteria than to modern filamentous

bacteria. Prokaryotes seem clearly to have been "hypobradytelic," exhibiting

exceptionally slow rates of morphological evolutionary change, and the evidence

suggests (but does not prove) that physiologically advanced oxygen-producing

photosynthesizers may have been represented in the Early Archean biota.

72
THE ENVIRONMENTAL DISTRIBUTION

ORGANISMS

N92-13637

OF LATE PROTEROZOIC

A. H. Knoll

Harvard University

Along present day coast lines, the environmental distributions of prokaryotic and

protistan populations are often sharply delimited. Realized habitat ranges are

generally narrower than those circumscribed by physiological tolerances, suggesting

the importance of organism-organism interactions in the determination of population

distributions. Microfossil populations preserved in silicified carbonates, dolomites, and

shales of the 700-800 Ma old Akademikerbreen Group, Svalbard, and elsewhere

indicate that the environmental distributions were defined equally clearly during the

Proterozoic Eon. The Draken Conglomerate Formation is a tidal flat/lagoonal complex

in which we have distinguished five principle biofacies containing a total of 42 taxa.

Supratidal to subtidal gradients include the increasing abundance and diversity of

both mat dweller microbenthos and allochthonous (principally planktonic) organisms,

as well as a taphonomically important pattern of decreasing sheath thickness among

mat builder microorganisms. The seaward barriers of Akademikerbreen lagoons were

oolitic shoals, and these contain about a dozen endolithic and epilthic species not

observed elsewhere in the group. Subtidal environments below fair weather wave

base are represented by mudstones of the Svanbergfjellet Formation. These contain

abundant and diverse cyanobacteria-like fossils generally similar to but specifically

different from those found in tidal flat sediments, as well as diverse unicellular protists -

- some of impressive morphological complexity -- and at least half a dozen cellularly

preserved metaphyte populations. In all, more than 80 species are distributed among

Akademikerbreen lithologies. Fossil assemblages from Svalbard and elsewhere

illustrate the potential for a much finer paleoecological, biostratigraphic, and, hence,

evolutionary resolution of the early fossil record.

73
N92-13638

THE BIOGEOCHEMISTRY OF MICROBIAL MATS, STROMATOLITES AND

THE ANCIENT BIOSPHERE

D. J. Des Marais* and D. E. Canfield

NASA Ames Research Center

Stromatolites offer an unparalleled geologic record of early life, because they

constitute the oldest (3.5 Ga) and most abundant recognizable remains of microbial

ecosystems. Microbial mats are living homologs of stromatolites, thus we can study

the physiology of the microbiota as well as the processes which create those features

of mats (e.g., "biomarker" organic compounds, elemental and stable isotopic

compositions) which are preserved in the ancient record.

Our observations of the carbon isotopic composition (a13C) of stromatolites and

microbial mats are consistent with the hypothesis that atmospheric CO 2 concentrations

have declined by at least one to two orders of magnitude during the past 2.5 Ga.

Whereas a13C values of carbonate carbon average about 0 permil during both the

early and mid-Proterozoic, the a13C values of stromatolitic organic matter increase

from an average of -35 between 2.0 and 2.6 Ga ago to an average of about -28 about

1.0 Ga ago. Modern microbial mats in hypersaline environments have a13C values

typically in the range of -5 to -9, relative to an inorganic bicarbonate source at 0 permil.

Both microbial mats and pure cultures of cyanobacteria grown in waters in nearequilibrium with current atmospheric CO2 levels exhibit minimal discrimination against

13C. In contrast, hot spring cyanobacterial mats or cyanobacterial cultures grown

under higher CO2 levels exhibit substantially greater discrimination. If care is taken to

compare modern mats with stromatolites from comparable environments, it might be

possible to estimate ancient levels of atmospheric CO2.

In modern microbial mats a tight coupling exists between photosynthetic organic

carbon production and subsequent carbon oxidation, mostly by sulfate reduction. The

rate of one process fuels a high rate of the other, with much of the sulfate reduction

occurring within the same depth interval as oxygenic photosynthesis. That sulfate

reduction activity occurs within a well-oxygenated environment questions the

conventional view that this is an obligately anaerobic process. Also contrary to

conventional thought, appreciable isotopic discrimination is observed even at the

highest rates of sulfate reduction (>12 millimolar per day). The sulfide has an isotopic

composition (a34s) about 45% lighter than that of the sulfate from which it is produced.

This large isotopic discrimination might allow us to search for the evolution of sulfate

reduction as a carbon mineralization process in stromatolites. This process was

indeed an important addition to the cycling of carbon on the early earth.

74
SYMBIOSIS AND THE ORIGIN OF

N92-13639

EUKARYOTIC MOTILITY

L. Margulis* and G. Hinkle

Department of Botany, University of Massachusetts

Our work continues to test the hypothesis of the origin of eukaryotic cell organelles by

microbial symbioses. With the widespread acceptance of the serial endosymbiotic

theory (SET) of the origin of plastids and mitochondria, we are testing the novel idea of

the symbiotic origin of the centrioles and axonemes (i. e., kinetosomes [9(3) + 0]*;

undulipodia including cilia, eukaryotic 'flagella' and all [9(2) + 2] organelles; the mitotic

spindle, and other eukaryotic microtubular systems) from spirochete bacteria motility

symbioses. Intracellular microtubular systems are purported to derive from symbiotic

associations between ancestral eukaryotic cells and motile bacteria. We are pursuing

four lines of approach to this problem: cloning the gene of a tubulin-like protein we

discovered in Spirocheata bajacaliforniensis, seeking axoneme proteins in

spirochetes by antibody cross-reaction, attempting to cultivate larger, free-living

spirochetes and studying in detail spirochetes (e. g., Cristispira) symbiotic with marine

animals.

The recent discovery of megabase quantities of DNA in the kinetosomes (the

structures underlying all undulipodia) of the green alga Chylamydomonas reinhardtii

by Hall, Ramanis and Luck [_ (1989) 59:121-132] has brought our still-controversial

hypothesis to the fore of a long-standing, newly intensified debate within the cell

biology community on the origin of microtubules in eukaryotic cells. While we await

confirmation of Hall's et aL report on the presence of a third extranuclear genome

(complementary to the genomes of plastids and mitochondria), we plan to probe the

spirochete genomic DNA with kinetosome-specific DNA probes in hopes of finding

homologous sequences. Regardless of the presence or absence of spirochetekinetosome DNA homologies, the existence of an extranuclear genome within the

elemental structure of eukaryotes, i. e., the kinetosome, is strong circumstantial

evidence for an autonomous, symbiotic origin for eukaryotic microtubule-based motility

systems.

*-The numbers between brackets refer to the arrangement of 24nm microtubules as

seen in transverse electron-microscopic section of these structures.

75
N9 2- 13 640 !.

IS CO2 CAPABLE OF KEEPING EARLY MARS WARM?

J. F. Kasting*

Department of Geosciences, The Pennsylvania State University

One of the goals of NASA's Exobiology Research Program is to determine whether life

exists today on Mars (unlikely) or whether it might have existed there at some time in

the past (more likely). Speculation about extinct life is driven by the observation of

channels on the Martian surface, thought to indicate the past presence of liquid water

and, hence, the existence of a warmer climate. Current thinking suggests that such a

climate could have been maintained if early Mars had a dense CO2 atmosphere with a

surface pressure of 1 to 5 bars.

One of the phenomena that Martian climate modelers (including myself) have not

looked at very carefully is the process of CO2 condensation. Reexamination of some

of my own calculations indicates that condensation should occur at high altitudes in

some high-CO2, Martian atmospheres, particularly those in which the solar constant is

set to its initial main sequence value, about 70% of present. CO2 condensation should

affect the surface temperature in at least two ways: 1) If it occurs in the convective

lower atmosphere, condensation will reduce the magnitude of the greenhouse effect

by decreasing the lapse rate. 2) Condensation at any altitude will produce clouds,

which can either warm or cool the climate depending on their altitude and optical

depth. (The dominant effect, however, is likely to be cooling.) Preliminary calculations

with a one-dimensional, radiative-convective climate model indicate that the lapse rate

change is substantial for low solar luminosity models. Indeed, the calculations imply

that no amount of CO2 is capable of raising the mean surface temperature of early

Mars above the freezing point of water, because the increase in planetary albedo due

to Rayleigh scattering outstrips the greenhouse effect at high CO2 partial pressures!

These calculations are preliminary and do not take into account changes in cloudiness

(which may worsen matters) or the nonideal behavior of CO2 along its saturation vapor

pressure curve (effect not yet determined). More detailed calculations are presently

being performed. If this climate problem persists, then the question of what kept early

Mars warm may need to be reexamined.

76
NONMARINE STROMATOLITES AND THE

MARS

 92"13641

SEARCH FOR EARLY LIFE ON

S. M. Awramik*

Department of Geological Sciences, Preston Cloud Research Laboratory,

University of California, Santa Barbara

The available evidence permits one to conclude that streams flowed and lakes

developed on Mars sometime in the remote past. Speculating that (1) biopoesis

occurred on Mars during its earliest history, (2) life evolved and diversified, (3) life

inhabited aqueous environments, and (4) sunlight was an important environmental

resource, then the lessons learned from the Earth's earliest fossil record suggest that

stromatolites might have formed on Mars. The most likely place to find stromatolites

and possibly microbial fossils on Mars would be in ancient lake and stream deposits.

If thermal spring deposits can be identified, then they too are sites for biogeological

investigations.

Today, lakes and thermal springs are not uncommon sites for stromatolites. This

appears to be true for the Phanerozoic. However, for the pre-Phanerozoic, little is

known about the record of life in nonmarine settings. Understanding the Archean and

Proterozoic record of nonmarine stromatolites is important for the general

understanding of the diversity of habitats for early life on Earth, sites of prokaryote

evolution and diversification, and biogeological interactions through time. The

possibility that a number of Archean and Proterozoic stromatolites might be nonmarine

rather than marine has commonly been overlooked. Unfortunately, recognition of prePhanerozoic nonmarine deposits is difficult and ambiguous. Unlike pre-Phanerozoic

marine stromatolites which formed in peritidal to slope environments with submerged

carbonate platform settings apparently favoring luxuriant stromatolite development,

lacustrine stromatolites may have developed best in near-shore settings.

Morphological variability may be greater in nonmarine stromatolites. Thus,

environmentally and morphologically, some nonmarine stromatolites may be

distinctive. Favored environments for formation of Archean and Proterozoic lacustrine

stromatolites and knowledge of their size, shape, and other morphological attributes

are important for the search for evidence of ancient Martian life.

77
N92-13642 -]

ENDOLITHIC MICROBIAL MODEL FOR MARTIAN EXOBIOLOGY: THE

ROAD TO EXTINCTION

R. Oscampo-Friedmann*

Florida A&M University

and

E. I. Friedmann

Florida State University

Martian exobiology is based on the assumption that on early Mars, liquid water was

present and that conditions were suitable for the evolution of life. Assuming that this

was the case, two questions arise:

(1) How did life disappear from the surface?

(2) What recognizable fingerprints of past microbial activity could have

been preserved on Mars?

(1) The Antarctic cryptoendolithic microbial ecosystem is a model for extinction in the

deteriorating Martian environment. Laboratory measurements and computer analysis

of long-term satellite-mediated nanoclimate records indicate that individual organisms

live permanently near the lower limits of their temperature range (between -10°C and

+2°C) while their optima are between 15°C and 25°C. In contrast, the net

photosynthetic activity of the _ommunity shows a maximum around 0°C, reflecting the

ambient temperature range. This apparently paradoxical situation is a result of a shift

in the primary producer/consumer ratio, an adaptive response of the community. As

the organisms are pushed to the limit of their physiological adaptability, even slight

further deterioration in the environment (cooling) results in cell death. Such cases

have been observed in nature. Thus, the response of organisms to extreme

environmental pressures which result in extinction can be studied on this model at the

cellular, organismal and community levels.

(2) Extreme dry environments are not conducive for fossilization. Yet, both Antarctic

and hot desert endolithic microorganisms leave behind recognizable trace fossils in

rocks. These trace fossils are the result of microbial leaching and of characteristic

biogenous weathering patterns. Similar fingerprints of past microbial activity may also

have been preserved on the surface of Mars.

78
THE NASA PLANETARY BIOLOGY

 92=1364 ,¢,

INTERNSHIP EXPERIENCE

G. Hinkle* and L. Margulis

Department of Botany, University of Massachusetts

By providing students from around the world with the opportunity to work with

established scientists in the fields of biogeochemistry, remote sensing and origins of

life, among others, the NASA Planetary Biology Internship (PBI) program has

successfully launched many scientific careers. Begun in 1980, the PBI program has

sponsored 100 interns in the past decade in over 50 different laboratories studying the

effects of life on Earth at a planetary scale. The PBI program (from 1980-1986) has

been described in the NASA document "The Internship Experience."

Each year approximately ten interns participate in research related to planetary

biology at NASA centers, NASA-sponsored research in university laboratories, and

private institutions. The PBI program also sponsors three students every year in both

the Microbiology and Marine Ecology Summer courses at the Marine Biological

Laboratory in Woods Hole, Massachusetts. The internships are open to all graduate

students and senior undergraduates accepted in graduate programs regardless of

nationality and generally last 6-8 weeks. In stressing the truly global nature of PBI, we

have awarded approximately one-fifth of the internships in recent years to students

from outside the United States. The internship consists of an award of $2000 in

addition to a $1200 travel stipend (for 1990). In an area of fiscal constraints, the PBI

program is rare in awarding young scientists travel funds and access to NASA

supported research. These unparalleled opportunities have led to an increase in both

the quality and number of the applicants every year.

The PBI program is supported by the Life Sciences Division of NASA and is

administered by the Marine Biological Laboratory at Woods Hole, Massachusetts

through the MBL Education Committee. Applications are due the 1st of March, 1991,

and can be obtained from Gregory Hinkle, Department of Botany, University of

Massachusetts, Amherst, MA 01003.

79

.8_E_8.SJ.(Z L 

EVOLUTION OF ADVANCED LIFE

Chairman - J. Billingham

This session covered research being carried out on asteroid impacts and their role in

the great extinctions of the Phanerozoic Eon. F. Asaro, of the Lawrence Berkeley

Laboratory reported on the "Fine Structure of the Late Eocene Iridium Anomaly in

Marine Sediments". Iridium (Ir) anomalies due to the impact of asteroids or comets on

the Earth had previously been identified in sediments from nine Late Eocene (approx.

35 million year old) sites, all at low latitudes. If the explosion from the impacting

bodies were large enough to spread IR and other impact debris world-wide, then the

impact debris could have obscured the sunlight and resulted in major extinctions of

species. In this context it was important to know whether the late Eocene Ir

anomalies also existed at high latitudes. If, in addition, there were clusters of impacts,

then the Ir abundance profiles in the sediments might exhibit secondary peaks (fine

structure) which would be separated by the same number of years from the main peak

in each section (if the sedimentation rates were very well behaved). Such consistent

fine structure would be supportive of the comet cluster hypotheses for impact on the

Earth and also provide very accurate relative dating between sections.

The Iridium Coincidence Spectrometer was used to make detailed Ir profile

measurements of three high-latitude Late Eocene marine sections from the Tasman

Sea (36°S), the Weddell Sea (64°S) and the Massignano section in Italy (43°N). The

most extensive measurements (over 400) were made in the Weddell Sea section, and

only one Ir anomaly above 50 parts-per-trillion (ppt) was found in a continuous

sampling of 5 million years of deposition. In each section there was a main Ir anomoly

of 150 to 200 ppt which was not related to clay or other terrestrial abundances and

hence could have been caused by the impact of an asteroid or comet on the Earth.

Two and possibly all three sites exhibited shoulders below the main Ir peak of 13 to 27

ppt and another Ir peak of 17 to 27 ppt about 1 to 3 meters above the main peak.

Further work is planned to examine whether the main Ir peak in all three sections

represents the same impact and, if so whether the secondary Ir peaks are due to

separate impacts.

D. Rays, from the University of Chicago examined the critical role played by species

extinction in the evolution of advance life on Earth. Without extinction, complex (and

intelligent) organisms would probably not have developed. If we are to be successful

in the search for extraterrestrial life, it is important to understand the role of extinction

and to be able to recognize the physical conditions that cause extinction of species.

An analysis of Sepkoski's compendium of the geologic time ranges of 30,000+ genera

of fossil animals has yielded a cumulative frequency distribution of species extinctions

for the past 600 million years. This distribution, in the form of a "Kill Curve", gives the

mean waiting-time between extinction events of a given magnitude. Thus, for

example, events causing the extinction of 5% of existing species occur, on average,

81 PRECEDING PAGE BLANK NOT FILMED
every one million years, while events causing 65% extiction occur about every 100

million years.

The equation for the Kill Curve has been combined with the most recent estimates of

comet and asteroid impact rates to produce a curve that predicts the species kill that

would result from a large-body impact if impact has been the primary cause of

extiction of species in the past. The resulting curve is plausible and conforms to

available information on the killing effects of impact. This leads, therefore, to the

working hypothesis that impact is responsible for most species extinctions.

A new database on the geographic distribution of extinctions in the Cretaceous period

has been constructied and analysed to search for geographic patterns in the mass

extinction that ended the Cretaceous period. This is part of a larger project in

database development to evaluate various strategies of building databases from the

scientific literature.

One hundred eighty six previously published lists of fossil species and genera were

analysed. Each list represents the fossils found at a geologic locality of latest

Cretaceous age. The locations were converted electronically to their Cretaceous

positions (to correct for continental drift). Multivariated analysis of the converted data

shows clearly mappable biogeographic provinces, thus confirming the quality of the

database.

For each fossil fauna, an extinction rate for genera was computed by comparison with

Sepkoski's range data for the same fossil groups. The resulting map of extinction

rates indicates that organisms in northern, mid-latitudes suffered substantially greater

extinction than elsewhere. Any causal mechanisms proposed for the mass extinction

must be consistent with this geographic pattern.

The fossil record on evolution was discussed by J. Sepkoski, also from the University

of Chicago. He described the data he has assembled on diversification and extinction.

Understanding the evolution of complex life is dependent upon knowledge of the fossil

record. Sepkoski has been compiling a synoptic database on some 32,000 fossil

genera from the international paleontologic literature. These data are being used to

investigate the history of global biodiversity, to measure rates of evolution, and to test

the 26 million year periodicity of mass extinction, a pattern that has become more

pronounced as better data have been accumulated. Measured rates of extinction are

also being used to parameterize models of evolutionary radiations and faunal change.

It has been observed that new animal groups tend to expand first in stressed

environments and then to radiate into more stable environments. The model suggests

this will happen only if the new groups are characterized by species that are more

successful in weathering normal environmental perturbations than the older groups

being replaced. This same pattern is observed at periodic mass extinctions: groups

that are normally characterized by low rates of extinction preferentially survive the

abnormal times of mass extinction. Thus, the evolution of extinction resistance has

been a key factor in the history of complex life.

The last paper entitled "Biogeochemical Modeling at Mass Extinction Boundaries:

Atmospheric Carbon Dioxide and Ocean Alkalinity at the K/T Boundary".was given by

82
M. Rampino of the Goddard Institute for Space Studies. His co-author was K. Calderia

of New York University.

The causes of mass extinctions and the importance of major bio-events in the history

of life are subjects of scientific interest. A large amount of geological, geochemical,

and paleontological information now exists for the Cretaceous/Tertiary (K/T) boundary

(66 Myr BP). These data are used here to constrain a newly developed timedependent biogeochemical cycle that is designed to study transient behavior of the

Earth system.

Model results suggest that the rate of pelagic production of CaCO3 shells during the

low productivity Strangelove ocean period (66.5-66 Myr BP) should have fallen below

the rate of riverine supply of Ca ++ and Mg ÷+ions to the world ocean by about a factor of

two. These results are supported by the observed low accumulation rates of CaCO3 at

a number of DSDP and ODP drill sites. Without the flux of CaCO3 to the sediments,

ocean alkalinity should have increased, resulting in a decrease of atmospheric CO2,

lowering of the CaCO3 lysocline, and leading to a calculated global cooling of about

4.5°C for several hundred thousand years. Eventual return of ocean productivity and

increased rock weathering would have decreased ocean alkalinity, and released CO2

to the atmosphere causing a calculated warming of about 2°C over latest Cretaceous

values. Strontium (Sr) isotope data suggest an increasing weathering flux to the

oceans at the K/T boundary (possible warming and Cooling), but the interpretation of

these data is complicated by diagenesis and other effects. It is also possible that some

stabilizing feedback may have acted to reduce the variability in ocean alkalinity, and

hence atmospheric CO2 during the Strangelove period. One possibility is that nutrientrich waters may have led to increased rates of carbonate and organic precipitation in

shallow waters, decreasing ocean alkalinity.

It was clear from the reports of all the authors that evidence for major body impact

events is now becoming strong, and that their proposed role in the great extinction of

evolutionary biology is gaining ground.

83
FINE STRUCTURE OF THE LATE EOCENE

SEDIMENTS

N92"13644J

IR ANOMALY IN MARINE

F. Asaro*

Lawrence Berkeley Laboratory, University of California, Berkeley

The following studies are part of a collaboration with several other scientists. The Late

Eocene Ir abundance profile in deep sea cores from Ocean Drilling Program Leg 113

Hole 689B on the Maude Rise off of Antarctica was studied with 410 samples

(encompassing about 5 million years of accumulation) which were collected

continuously in 10 cm increments and measured with the Iridium Coincidence

Spectrometer (ICS). The ICS was subsequently modified to measure 13 other

elements simultaneously with the Ir. The abundance profiles of these elements were

then determined in the Late Eocene Massignano section in central Italy with 250

samples (encompassing roughly 2 million years of accumulation) which were

collected about every 5 cm in about 2 cm increments. These studies augmented a

previous one (which included many elements) of deep sea cores from Deep Sea

Drilling Project Site 592 on the Lord Howe Rise in the Tasman Sea between Australia

and New Zealand. In the latter study 50 samples (encompassing roughly 0.7 million

years of accumulation) were collected continuously in 10 cm increments.

In all three studies one major ir anomaly, spread over 25 or more cm, was found with

respective net abundances in parts-per-trillion (ppt) of 156+10 over an average

background of 5.9+1.8, 156+19 over an estimated average background of 42.5+1.2

and 191+6 over an average background of 8.5+0.3. The respective positions of the

main peaks were ODP 113-689B 14H-6, 100-110 cm; 5.61 meters (about 7.9 meters

below the top of combined nannoplankton zone 19/20) based on the field meter

markers in the Massignano section; and DSDP 90-592 38-5 50-60 cm (about 14.4

meters below the top of combined nannoplankton zone 19/20). The main Ir peak had

a shoulder on the lower side which had net abundances of 13+5, 27:L-6 and 27+2 ppt,

respectively, and was separated from the main peak by about 30, 17 and 30 cm,

respectively. The precision of the first measurement was not good enough to be sure

the peak was real. In two of the sections, Massignano and Site 592, another Ir peak

was observed 131 and 220 cm respectively, above the main peak with respective net

abundances of 27+5 and 19.2+1.5 ppt. A possible similar peak with a net Ir

abundance of 17+7 ppt over a background of 6 ppt was observed in Hole 689B

samples 330 cm above the main peak. The ICS was operating in a scanning mode in

that region, however, and the precision of the measurement was not good enough to

be certain the peak was real. The main Ir peaks tail upward in the three sections, and

the tails may contain additional structure. An isolated sample at 10.24 meters in the

Massignano section had an unusually high Ir abundance (313 ppt) and a Se

abundance 200 times higher than the samples above and below.

The ramifications of the data with respect to relative chronology and relative

sedimentation rates at the different sites and implications with respect to the comet

cluster hypotheses of periodic impacts on the Earth will be discussed.

84
CUMULATIVE FREQUENCY DISTRIBUTION

EXTINCTIONS

 92"1 645

OF PAST SPECIES

D. M. Raup*

University of Chicago

Analysis of Sepkoski's compendium of the time ranges of 30,000+ taxa yields a mean

duration of 28.4 ma for genera of fossil invertebrates. This converts to an average

extinction rate of 3.5 percent per million years or about one percent every 286, 000

years. Using survivorship techniques, these estimates can be converted to the

species level, yielding a Phanerozoic average of one percent species extinction every

40,000 years.

Variation in extinction rates through time is far greater than the null expectation of a

homogeneous birth-death model and this reflects the well-known episodicity of

extinction -- ranging from a few large mass extinctions to so-called background

extinction. The observed variation in rates can be used to construct a cumulative

frequency distribution of extinction intensity, and this distribution, in the form of a "kill

curve" for species, shows the expected waiting times between extinction events of a

given intensity. The kill curve is an average description of the extinction record and

does not imply any cause or causes of extinction.

The kill curve shows, among other things, that only about five percent of total species

extinctions in the Phanerozoic were involved in the five largest mass extinctions. The

other 95% were distributed among large and small events not normally called mass

extinctions.

As an exploration of the possibly absurd proposition that most past extinctions were

produced by the effects of large-body impact, the kill curve for species has been

mapped on the comparable distribution for comet and asteroid impacts. The result is a

curve predicting the species kill for a given size of impacting object (expressed as

crater size). The results are reasonable in that impacts producing craters less than 30

km (diameter) cause negligible extinction but those producing craters 100-150 km

(diameter) cause extinction of species in the range of 45-60 percent.

85
N92-13646

GEOGRAPHY OF CRETACEOUS EXTINCTIONS: DATA BASE

DEVELOPMENT

D. M. Raup*

University of Chicago

Data bases built from the source literature are plagued by problems of data quality.

Unless the data acquisition is done by experts, working slowly, the data base may

contain so much "garbage" that true signals and patterns cannot be detected. On the

other hand, high quality data bases develop so slowly that satisfactory statistical

analysis may never be possible due to the small sample sizes. This report describes

results of a test of the opposite strategy: rapid data acquisition by non-experts with

minimal control on data quality.

186 published lists of species and genera of fossil invertebrates of latest Cretaceous

age (Maestrichtian) were located through a random search of the paleobiological and

geological literature. The geographic location for each faunal list was then

transformed electronically to Maestrichtian latitude and longitude and the lists were

further digested to identify the genera occurring in each ten-degree, latitude-longitude

block. The geographical lists were clustered using the Otsuka similarity coefficient and

a standard unweight-pair-group method. The resulting clusters are remarkably

consistent geographically, indicating that a strong biogeographic signal is visible

despite low-quality data.

A further test evaluated the geographic pattern of end-Cretaceous extinctions. All

genera in the data base were compared with Sepkoski's compendium of time ranges

of genera to determine which of the reported genera survived the Cretaceous mass

extinction. In turn, extinction rates for the ten-degree, latitude-longitude blocks were

mapped. The resulting distribution is readily interpretable as a robust pattern of the

geography of the mass extinction.

The study demonstrates that a low-quality data base, built rapidly, can provide a basis

for meaningful analysis of past biotic events.

86
N92-13647

THE FOSSIL RECORD OF EVOLUTION:

DATA ON DIVERSIFICATION AND EXTINCTION

J. J. Sepkoski, Jr.*

University of Chicago

Understanding of the evolution of complex life, and of the roles that changing

terrestrial and extraterrestrial environments played in life's history, is dependent upon

synthetic knowledge of the fossil record. Paleontologists have been describing fossils

for more than two centuries. However, much of this information is dispersed in

monographs and journal articles published throughout the world. Over the past

several years, I have been surveying this literature and compiling a synoptic data base

on times of origination and extinction of fossil genera. The data base, which now

holds approximately 32,000 genera, covers all taxonomic groups of marine animals,

incorporates the most recent taxonomic assignments, and uses a detailed global time

framework that can resolve originations and extinctions to intervals averaging three

million years in duration. These data can be used to compile patterns of global

biodiversity, measure rates of taxic evolution, and test hypotheses concerning

adaptive radiations, mass extinctions, etc. Thus far, considerable effort has been

devoted to using the data to test the hypothesis of periodicity of mass extinction.

Rates of extinction measured from the data base have also been used to calibrate

models of evolutionary radiations in marine environments. It has been observed that

new groups, or "clades," of animals (i. e. orders and classes) tend to reach appreciable

diversity first in nearshore environments and then to radiate in more offshore

environments; during decline, these clades may disappear from the nearshore while

persisting in offshore, deep water habitats. These observations have led to

suggestions that there is something special about stressful or perturbed environments

that promotes the evolution of novel kinds of animals that can rapidly replace their

predecessors. The numerical model that is being investigated to study this

phenomenon treats environments along onshore-offshore gradients as if they were

discrete habitats. Each habitat contains a set number of genera (as observed in the

fossil record). During any time interval, genera within a habitat can become extinct

with a probability that varies among clades (as measured from the data base) and

increases toward the nearshore (as also observed in the fossil record). Extirpated

genera are replaced either by speciation within the habitat or by immigration of genera

from adjacent habitats. Solutions of the model demonstrate that extinction-resistant

clades will replace extinction-prone clades and that this replacement will proceed

along the onshore-offshore gradient regardless of where new clades originate. Thus,

patterns of replacement are not dependent on special evolutionary properties of

stressed environments. Instead, they reflect radiations of clades whose species are

more successful in weathering environmental perturbations. This is the same pattern

that is observed in taxonomic selectivity at mass extinctions (including the

Cretaceous-Tertiary event): clades that are characterized by low rates of extinction

during normal times appear to preferentially survive the abnormal times of mass

extinction.

87
N92-13648 j,

BIOGEOCHEMICAL MODELING AT MASS EXTINCTION BOUNDARIES

M. R. Rampino* & K. G. Caldeira

Earth Systems Group, New York University

The causes of major mass extinctions is a subject of considerable interest to those

concerned with the history and evolution of life on earth. The primary objectives of the

proposed plan of research are: 1) to develop quantitative time-dependent

biogeochemicai cycle models, coupled with an ocean atmosphere in order to improve

our understanding of global scale physical, chemical, and biological processes that

control the distribution of elements important for life at times of mass extinctions, and 2)

to develop a comprehensive data base of the best available geochemical, isotopic and

other relevant geologic data from sections across mass extinction boundaries. These

data will be used to constrain and test the biogeochemical model. These modeling

experiments should prove useful: 1) in determining the possible cause(s) of the

environmental changes seen at bio-event boundaries, 2) in identifying and

quantifying little-known feedbacks among the oceans, atmosphere and biosphere, and

3) in providing additional insights into the possible responses of the earth system to

perturbations of various timescales.

One of the best known mass extinction events marks the Cretaceous/Tertiary (K/T)

boundary (66 Myr ago). Data from the K/T boundary are used here to constrain a

newly developed time-dependent biogeochemical cycle model that is designed to

study transient behavior of the earth system. Model results predict significant

fluctuations in ocean alkalinity, atmospheric CO2, and global temperatures caused by

extinction of calcareous plankton and reduction in the sedimentation rates of pelagic

carbonates and organic carbon. Oxygen-isotope and other paleoclimatic data from

K/T time provide some evidence that such climatic fluctuations may have occurred, but

stabilizing feedbacks may have acted to reduce the ocean alkalinity and carbon

dioxide fluctuations.

88
&5.8.SJ.QtL.VJ

SETI

Chairman - J. Tarter

John Billingham (Acting Chief of SETI Office) and Dave Brocker (Project Manager) of

Ames Research Center outlined the recent technical and bureaucratic history of

NASA's SETI Microwave Observing Project. Together they described how it fit into the

overall Exobiology Program and what the Project Management structure was at Ames

Research Center (lead center) and the Jet Propulsion Laboratory.

Following this introduction, Larry Webster and Michael Klein (Deputy Project

Managers) described the Targeted Search and Sky Survey elements of the Project.

Prototype Observing systems are being developed for both elements and software to

permit real-time signal detection, and near-time signal recognition is being tested. If

funding is forthcoming, these prototypes will be used to inaugurate the MOP observing

phase October 12, 1992.

The Targeted Search prototype will provide dual circular polarization, six

simultaneous resolutions of 1, 2, 4, 8, 4, 28 Hz covering 10 MHz of input bandwidth

and will be capable of detecting drifting and non-drifting CW signals and narrowband

pulses. The volume of three dimensional space searched while examining 773 solartype stars over 1 to 3 GHz is limited by the achieved sensitivity and the unknown

transmitter power that determines the effective range for any signal. This prototype will

be replicated 6 times to produce the full observational capability of the Targeted

Search. Observing systems of 10 MHz bandwidth will be used separately or parallel

on large radio astronomy telescopes around the world as well as the DSSN 70 m

antennas and a dedicated SETI telescope to complete observations by 1999.

The Sky Survey prototype will initially provide dual circular polarization and a

resolution of 20 Hz covering 20 MHz. Software will continuously compare events

above threshold as the survey scans the sky and will record for later confirmation

those candidates that provide the appropriate point source response along and

between the individual scan lines. This prototype will be augmented to provide the full

300 MHz bandwidth coverage and 20 MHz resolution necessary to conduct the Sky

Survey search for drifting and non-drifting CW signals. The Sky Survey system will be

used on the DSN 34 m antenna at Goldstone (and perhaps also the Madrid station) to

search the Northern hemisphere before moving to Tidbinbilla to complete the Sky

Survey by 1999.

Stuart Bowyer of UC of Berkeley described the SERENDIP system for commensal

SETI observations that has been developed with NASA funds. This system provides a

spectrometer with 65,536 channels of 1 Hz resolution and was used to "piggy back" on

routine astronomical research programs, primarily at the 300 foot antenna at the

NRAO. A significant coverage of "interesting" frequencies and sky directions can

thereby be researched without requiring dedicated antenna time. Extensive postprocessing is required to remove RFI contamination. About half of the candidate

detections from 7000 hours of observation have been re-observed using the 140 foot

89
antenna without re-detection. The SERENDIP system has recently been upgraded

and sold to the SETI Microwave Observing Project for its program of RFI studies.

These funds will be used to create the next generation of SERENDIP III having 108

spectral channels, for continuous deployment at Arecibo on the carriage house

counter-balance for the new Gregorian system.

Bob Dixon form the Ohio State University Radio Observatory described the long

running SETI Sky Survey program at that site. A number of improvements to this site

are possible and could be part of a future upgrade program if funds become available.

This site is the only one to continuously monitor its RFI environment with a discone

antenna mounted on the main feed horn. In addition, a unique, rapid follow-up search

strategy will soon be functioning at the site. Software will make a real-time

comparison of events detected above threshold with the expected beam pattern for a

point source passing through the dual feed horn system. Whenever a strong event

having the correct pattern is detected, the telescope will automatically exit its transit

sky survey program and begin to track the detected source across the sky. When the

detected source sets, the software will again resume its standard sky survey program.

In this way, it is hoped that sufficient data can be collected to recognize the source of

detected signals, while they are still present in the antenna field of view.

The last paper of the session by Albert Betz of UC Berkeley described the construction

of a high resolution Infrared Spectrometer. This turnable CO2 laser spectrometer

mixes signals down to radio frequencies so that the standard heterodyne techniques

can be used to achieve extremely good spectral resolution. It will be used with one of

the 1.6 m mirrors from a newly completed IR interferometer to make a 10 _ search of

nearby solar-type stars. This search will be the first IR "magic frequency" program.

The question of whether signal-to-noise ratio is greater at radio or IR frequencies has

been the subject of decades of debate. This question cannot be answered

theoretically because it depends on how strongly beamed the transmitted signal is

assumed to be (ultimately how extraterrestrial engineers construct large antennas as a

function of wavelength!). Like most SETI questions, an experimental solution is the

only reasonable approach.

9O
THE NASA SETI

N92-13649

PROGRAM "

J. Billingham* and D. H. Brocker*

NASA Ames Research Center

In 1959 Morrison and Cocconi proposed that a sensible way to conduct interstellar

communication would be to use radio at or near the frequency of hydrogen. In 1960

Frank Drake conducted the first Search for Extraterrestrial Intelligence (SETI) using a

radiotelescope at Green Bank in West Virginia. Since 1970 NASA has systematically

developed a definitive program to conduct a sophisticated search for evidence of

extraterrestrial intelligent life.

The basic hypothesis is that life may be widespread in the universe, and that in many

instances extraterrestrial life may have evolved into technological civilizations. The

underlying scientific arguments are based on our continuously improving knowledge

of astronomy and astrophysics, especially star system formation, and of planetary

science, chemical evolution and biological evolution. If only one in a million sun-like

stars in our galaxy harbors species with cognitive intelligence, then there are 100,000

civilizations in the Milky Way alone.

The fields of radioastronomy digital electronic engineering, spectrum analysis and

signal detection have advanced rapidly in the last twenty years and now allow us to

build sophisticated systems to attempt the detection of ETI signals. In concert with the

scientific and engineering communities NASA has developed, over the last several

years, a Microwave Observing Project whose goal is to design, build and operate SETI

systems during the decade of the nineties in pursuit of the goal of signal detection.

The Microwave Observing Project is now approved and underway. It is managed in

Washington as a part of the Exobiology Program in the Division of Life Sciences at

NASA HQ. It is supported with additional funding from the Office of Space Operations.

Ames and JPL carry out the Project, with Ames as Lead Center. There are two major

components in the Project, the Targeted Search Element, under Ames management,

and the Sky Survey Element, under JPL management. The total budget for the

Microwave Observing Project is $115 over the ten year period 1990-1999. More

detailed descriptions of the two elements of the Project are given in the following

reports by the Ames and JPL Project Managers, respectively.

91
N92-13650 !

NASA-SETI MICROWAVE OBSERVING PROJECT

ELEMENT

TARGETED SEARCH

L. D. Webster*

NASA Ames Research Center

The Targeted Search Element (TSE) performs one of two complimentary search

strategies of the NASA-SETI Microwave Observing Project (MOP): the Targeted

Search. The principle objective of the Targeted Search strategy is to scan the

microwave window between the frequencies of one to three gigahertz for narrow-band

microwave emissions eminating from the direction of 773 specifically targeted stars.

The scanning process is accomplished at a minimum resolution of one or two Hertz at

very high sensitivity. Detectable signals will be of a continuous wave or pulsed form

and may also drift in frequency. The TSE will possess extensive Radio Frequency

Interference (RFI) mitigatation and verification capability as the majority of signals

detected by the TSE will be of local origin. Any signal passing through RFI

classification and classifiable as an Extraterrestrial Intelligence (ETI) candidate will be

further validated at non-MOP observatories using established protocol.

The Targeted Search will be conducted using the capability provided by the Targeted

Search Element. The TSE provides six Targeted Search Systems (TSS) which

independently or cooperatively perform automated collection, analysis, storage, and

a_chive of signal data. Data is collected in 10 megahertz "chunks" and signal

processing is performed at a rate of of 160 megabits per second. Signal data is

obtained utilizing the largest radio telescopes available for the Targeted Search such

as those at Arecibo and Nancay or at the dedicated NASA-SETI facility. This latter

facility will allow continuous collection of data. The TSE also provides for TSS

utilization planning, logistics, remote operation, and for off-line data analysis, and

permanent archive of both the Targeted Search and Sky Survey data.

The TSE is being developed "in-house" by the NASA Ames Research Center (ARC).

ARC is performing TSE Systems Engineering and developing a preproduction version

of the Targeted Search System (TSS). The preproduction TSS will be used to initiate

the MOP Targeted Search on Columbus Day, 1992 at the Arecibo Observatory in

Puerto Rico.

92
NASA SETI

 92-13651

MICROWAVE OBSERVING PROJECT -

SKY SURVEY ELEMENT

M. J. Klein*

Jet Propulsion Laboratory, California Institute of Technology

The SETI Sky Survey observing program is one of two complimentary strategies that

NASA plans to use in its microwave Search for Extraterrestrial Intelligence (SETI).

The primary objective of the Sky Survey is to search the entire sky over the frequency

range 1.0 GHz to 10.0 GHz for evidence of narrow band signals of extraterrestrial,

intelligent origin. Frequency resolutions of 30 Hz or narrower will be used across the

entire band. Spectrum analyzers with upwards of ten million channels are required to

keep the survey time approximately 6 years. Data rates in excess of 10 megabits per

second will be generated in the data taking process. Sophisticated data processing

techniques will be required to determine the ever changing receiver baselines, and to

detect and archive potential SETI signals. Existing radio telescopes, including several

of NASA's Deep Space Network (DSN) 34 meter antennas located at Goldstone, CA.,

and Tidbinbilla, Australia, will be used for the observations. The Jet Propulsion

Laboratory has the primary responsibility to develop and carry out the Sky Survey.

In order to lay the foundation for the full scale SETI Sky Survey, a prototype system is

being developed at the Jet Propulsion Laboratory. The system will be installed at the

new 34-m high efficiency antenna at the DSS 13 research and development station,

Goldstone, CA, where it will be used to initiate the observational phase of the NASA

SETI Sky Survey. It is anticipated that the early observations be useful to test signal

detection algorithms, scan strategies, and RFI rejection schemes. The "SETI specific"

elements of the prototype system are:

(a)

(b)

(c)

the Wide Band Spectrum Analyzer (WBSA); a 2-million channel

FFT spectrum analyzer which covers an instantaneous bandpass

of 40 MHz.

the signal detection processor: a hardware module which

executes a detection algorithm "along the scan", which reduces

the data rate by factors of 1,000 or more.

the SETI Sky Survey Manager, a network-based C-language

environment that provides observatory control, performs data

acquisition and analysis algorithms.

A high level description of the prototype hardware and software systems will be given

and the current status of the system development will be reported.

This paper presents the results of one phase of research carried out at the Jet

Propulsion Laboratory, California Institute of Technology, under a contract with the

National Aeronautics and Space Administration.

93
THE SERENDIP Ii SET! PROJECT:

N9 2- 13 652 .j.

CURRENT STATUS

C.S. Bowyer, D. Werthimer, C. Donnelly, W. Herrick

and M. Lampton

Space Sciences Institute, University of California, Berkeley

Over the past 30 years interest in extraterrestrial intelligence has progressed from

philosophical discussion to rigorous scientific endeavors attempting to make contact.

Since it is impossible to assess the probability of success and the amount of telescope

time needed for detection, SETI projects are plagued with the problem of attaining the

large amounts of time needed on the world's precious few large radio telescopes. To

circumvent this problem, the SERENDIP instrument operates autonomously in a

piggyback mode utilizing whatever observing plan is chosen by the primary observer.

In this way large quantities of high-quality data can be collected in a cost-effective and

unobtrusive manner.

During normal operations, SERENDIP logs statistically significant events for further offline analysis. Due to the large number of terrestrial and near-space transmitters on

earth, a major element of the SERENDIP project involves identifying and rejecting

spurious signals from these sources. Another major element of the SERENDIP project

(as well as most other SETI efforts) is detecting ETI signals. Events selected as

candidate ETI signals are studied further in a targeted search program which utilizes

between 24 to 48 hours of dedicated telescope time each year.

94
 92-i, 65 

REOPTIMIZATION OF THE OHIO STATE UNIVERSITY RADIO

TELESCOPE FOR THE NASA SETI PROGRAM

R. S. Dixon

The Ohio State University Radio Observatory

The Ohio State University radiotelescope is the second largest radio telescope in the

United States, equivalent in collecting area (2200 m2) to a 175-foot diameter dish. For

the past 17 years it has been dedicated fulltime to SETI, and it is now being

considered by NASA for selection as the NASA dedicated SETI observatory.

The telescope was originally designed, optimized, and used as an all-sky survey

instrument to create detailed maps and catalogs of the radio astronomical sky. For the

SETI program, some reoptimizations are required.

Right ascension tracking for one to two hours (depending on the declination) has been

achieved by exploiting the exceptionally large f/d ratio of the telescope. The feed

horns have been mounted on a large moveable, rubber-tired cart which is capable of a

total motion of 100 feet. The cart can carry many horns, making possible simultaneous

observations at many sky directions and frequency ranges.

Rapid declination movement and its automation will be accomplished through

simplification of the existing braking system, and replacement of older mechanical

sensors by modern electronic inclinometers and proximity detectors.

Circular polarization capability will be achieved through an increase in the number of

horizontal wires in the reflector mesh, or addition of a finer mesh on top of the existing

one.

The telescope has great inherent resistance to radio frequency interference, due to its

ground-mounted feed horns and shielding by the large reflectors of half the horizon.

The resistance has been recently increased further by installation of rolled-edges and

diffraction-trapping gratings on the feed horns. If further shielding should be required,

inexpensive side shields could be added to the telescope, making it a totally closed

structure on all four sides.

95
A DIRECTED SEARCH

N92- 13 654 .J

FOR EXTRATERRESTRIAL LASER SIGNALS

A. Betz

Space Sciences Laboratory

The focus of NASA's SETI program is on microwave frequencies, where receivers

have the best sensitivities for the detection of narrowband signals. Such receivers,

when coupled to existing radio telescopes, form an optimal system for broad area

searches over the sky. For a directed search, however, such as toward specific stars,

calculations show that infrared wavelengths can be equally as effective as radio

wavelengths for establishing an interstellar communication link. This is true because

infrared telescopes have higher directivities (gains) that effectively compensate for the

lower sensitivities of infrared receivers. The result is that, for a given level of

transmitted power, the S/N ratio for communications is equally as good at infrared and

radio wavelengths. It should also be noted that the overall sensitivities of both receiver

systems are quite close to their respective fundamental limits: background thermal

noise for the radio frequency system and quantum noise for the infrared receiver.

Consequently, the choice of an optimum communication frequency may well be

determined more by the achievable power levels of transmitters rather than the

ultimate sensitivities of receivers at any specific frequency. In the infrared, CO2 laser

transmitters with power levels >1 MW can already be built on Earth. For a slightly

more advanced civilization, a similar but enormously more powerful laser may be

possible using a planetary atmosphere rich in CO2. Because of these possibilities and

our own ignorance of what is really the "optimum" search frequency, a search for

narrowband signals at infrared frequencies should be a part of a balanced SETI

program.

Detection of narrowband infrared signals is best done with a heterodyne receiver

functionally identical to a microwave spectral line receiver. We have built such a

receiver for the detection of CO2 laser radiation at wavelengths near 10 _m (30 THz).

The spectrometer uses a high-speed HgCdTe diode as the photomixer and a small

CO2 laser as the local oscillator. Output signals in the intermediate frequency range

0.1-2.6 GHz are processed by a 1000-channel acousto-optic (AOS) signal processor.

The receiver is being used on a 1.5-m telescope on Mt. Wilson to survey a selected

sample of 150 nearby stars. The current status of the work will be discussed along

with a prognosis for further technical development and observational work.

96
SOLAR SYSTEM EXPLORATION (11)

Chairman - G. C. Carle

The concluding session of the Symposium was comprised of a spectrum of

presentations related to the extraterrestrial aspects of exobiology. Subjects ranged

from planetary protection to instrumentation for the exploration of Titan, and from

advanced technology development for future missions to the importance of meteors

and comets to prebiotic chemistry.

D. DeVincenzi began the session with a report on planetary protection in respect to the

Space Exploration Initiative announced last year by U.S. President Bush. The central

focus of the Initiative is to establish a manned presence on Mars which will require a

number of robotic precursor missions. With each of these missions, cross

contamination of Earth and Mars becomes an important issue. To address questions

related to this issue, a workshop was held, the preliminary result of which was a report

which made several recommendations for dealing with forward and backward

contamination as well as non-scientific issues including public relations, legal,

regulatory, international, and environmental concerns. The report will be further

discussed when it is presented at the next COSPAR meeting.

The next paper was presented by W. Irvine who discussed an analysis of the images

of Phobos obtained from the recent Soviet mission to the martian system with the

Phobos 2 spacecraft. Earlier ground-based and flight data indicates that Phobos may

be a captured C-type asteroid which could contain relatively unaltered organic as well

as preserved interstellar material representative of the early history of the solar system.

Unfortunately, both Phobos 1 and 2 suffered major technical failures and only a small

number of images were obtained by the FREGAT camera. Results-to-date include

root-mean-square surface slopes, albedo fluctuations, and corresponding correlation

lengths.

G. Carle presented a paper describing an instrument he and his colleagues have

proposed for the Cassini Mission. The Cassini Mission is a joint undertaking of the

National Aeronautics and Space Administration and the European Space Agency to

explore the saturian system with a Saturn orbiter and the Huygens Probe (a Titan

atmospheric entry probe). The mission will be launched in 1996 and arrive at Titan in

2003. The proposed instrument is the Titan Aerosol and Gas Experiment (TAGEX)

which, if selected, will identify and quantify the major and trace components of the

atmospheric aerosols and gases. Such measurements would aid in the

understanding of planetary-scale organic chemistry and help clarify prebiotic

processes on Titan as well as on Earth.

D. Kojiro followed with a paper describing the use of an advanced ion mobility

spectrometer to analyze model components of Titan's atmosphere. The instrument

described will be a fundamental part of TAGEX if it is selected. The ion mobility

spectrometer is an atmospheric pressure, chemical detector that quantifies and

produces an identifying spectrum for each chemical species analyzed. Conventional

97
ion mobility spectrometers use a molecule-ion reaction based on water to ionize each

analyte, which is not appropriate for hydrocarbons. The newly developed instrument

uses either an ultra-dry system or metastable ionization to accomplish ionization, thus

extending the capability to the hydrocarbons and increasing sensitivity by several

orders of magnitude.

T. Shen presented work he has conducted in developing novel and powerful gas

chromatograph columns that can be used with the advanced detectors required for

flight experiments. These columns are based on a new silicone polymer developed by

him and can rapidly and efficiently separate mixtures of highly polar compounds, such

as amines, and nonpolar organics, such as hydrocarbons. He also presented

preliminary results from a mathematical model which is being developed to predict the

chromatographic behavior of potential polymeric structures before they are

synthesized.

J. Valentin presented the results of studies on various advanced gas chromatographic

analytical concepts for possible use in future planetary missions. He reported on the

first-time use of Multiplex Gas Chromatography for samples which changed in

composition and concentration during the analytical sampling period, and a waterspecific instrument based on this technique which is under development for a future

Mars mission. Another area reported upon was the technique of cryofocussing which

provides the capability to collect samples from low pressure environments for very low

level (ppb) analysis; this technique has been included the TAGEX instrument which

was proposed for the Cassini-Huygens Probe mission.

The last paper of the session was presented by S. Miller who reported on theoretical

considerations of the fate of prebiotic amino acids including those supplied from

extraterrestrial sources and those produced in the primitive atmosphere. It was

reasoned that amino acids cannot accumulate over more than 107 years because the

entire ocean cycles through hydrothermal vents during this time period thus any

accumulated amino acids would be destroyed. It was further estimated that during this

period atmospheric processes would produce an amino acid concentration of = 10-4

M in an ocean of present size. Further, it was concluded that cometary and meteoritic

contributions to the prebiotic earth were only a few percent of the Earth-based

synthesis.

98
PLANETARY PROTECTION ISSUES AND

MARS

N92-13655

b .

HUMAN EXPLORATION OF

D. L. DeVincenzi

NASA Ames Research Center

A key feature of the Space Exploration Initiative announced last year by the President

involves human missions to Mars. The report describing the initiative cites the search

for life on Mars, extant or extinct, as one of five science themes for such an endeavor.

Because of this, concerns for Planetary Protection (PP) have arisen on two fronts: 1)

forward contamination of Mars by spacecraft-borne terrestrial microbes which could

interfere with exobiological analyses, and 2) back contamination of Earth by species

that may be present in returned Mars samples. The US is also signatory to an

international treaty designed to protect Earth and planets from harmful crosscontamination during exploration. Therefore, it is timely to assess the necessity for,

and impact of, PP procedures on the mission set comprising the human exploration of

Mars.

A recent Workshop addressed PP questions of this type. The following ground-rules

were adopted: 1)information needed for PP must be obtained during the robotic

precursor phase prior to human landings, 2) returned samples will be considered

biologically hazardous until proven otherwise, 3) deposition of microbes on Mars is

inevitable when humans land, and 4) human landings are unlikely until it is

demonstrated that there is no harmful effect of martian materials. These

considerations drove the adoption of a conservative PP strategy for precursor missions

as follows: 1) for forward contamination prevention, all orbiters will have Mars

Observer-like controls on assembly, trajectory, and lifetime. All landers will have

Viking-like controls on assembly, sterilization, and bioshield, and 2) for back

contamination prevention, all sample return missions will have controls including

hardware sterilization, bioshield, fail-safe sample sealing, break contact chain with

surface, and Earth containment and quarantine analysis. In addition, the Workshop

produced several recommendations for dealing with forward and back contamination

concerns from non-scientific perspectives, including public relations, legal, regulatory,

international, and environmental.

99
N92-13656 .]

ANALYSIS OF IMAGES OBTAINED BY THE PHOBOS 2 SPACECRAFT

W. M. Irvine*

University of Massachusetts

The reflection spectrum and density of the Martian satellite Phobos suggest that it may

be a captured C-type asteroid and hence may contain relatively unaltered organic

material from the early history of the solar system. Since there is evidence from the

isotopic anomalies that meteorites presumably derived from such asteroids contain

preserved interstellar material, it is conceivable that evidence for interstellar matter

might also be present on Phobos. The present research concerns interpretation of the

chemical composition of Phobos' surface and analysis of images of Phobos taken by

the FREGAT camera equipment aboard the Phobos 2 spacecraft, including both diskintegrated and disk-resolved photometry. Because the surface of Phobos is a regolith

(a pulverized surface layer of irregular texture), spectral information on the surface

composition will be convolved with information on the surface texture. A primary goal

of the present research has been to untangle these effects.

Unfortunately, the spacecraft Phobos 1 lost contact with Earth during its transit to Mars,

and Phobos 2 likewise lost contact after two months in orbit around Mars. Thus, the

"hovering" phase of very close approach and the landing of instruments on the surface

of Phobos did not take place, so that no data on the elemental composition of the

surface is available. However, thirty-seven images were obtained of the satellite. The

results include the first such observations at near infrared wavelengths, for which diskintegrated results show that the corresponding geometric albedo is quite small and

very similar to the value in the blue. The resolved surface photometry has been

analyzed by developing new methods of radiative transfer in rough surface layers and

a procedure referred to as "statistical photoclinometry". The results provide rms

surface slopes on scales from the order of 1 millimeter to 250 meters, albedo

fluctuations, and corresponding correlation lengths.

100
N92-13657

TITAN AEROSOL AND GAS EXPERIMENT FOR THE HUYGENS PROBE

G. C. Carle, D. R. Kojiro, V. Oberbeck, B. J. O'Hara, J.B. Pollack, J.R. Valentin

NASA - Ames Research Center,

A. Bar-Nun

University of TeI-Aviv,

M. J. Cohen

PCP, Inc.,

J. P. Ferris

Rensselaer Polytechnic Insititute,

J. M. Greenberg

University of Leiden

and

T. W. Scattergood

State University of New York - Stony Brook

The Cassini mission is a joint undertaking of the National Aeronautics and Space

Administration (NASA) and the European Space Agency (ESA) to explore the Saturnian

system with a Saturn orbiter and a Titan probe. The launch vehicle and the Saturn orbiter are

the responsibility of NASA while the Huygens Probe (the detachable Titan probe) is the

responsibility of ESA. The spacecraft will be launched in 1996 and the Huygens Probe will

arrive at Titan in 2003.

The Cassini Mission - Huygens Probe provides a unique opportunity to obtain detailed

information about the atmosphere and, possibly, the surface of Titan. Titan possesses a

substantial nitrogen atmosphere containing methane and many other organic compounds.

Although the conditions on present day Titan are significantly different from the primitive Earth,

Titan provides a venue for both comparative planetology and the study of certain aspects of

exobiology on a planetary scale. For example, within Titan's atmosphere, irreversible

conversion of methane, presumably dominated by photochemical reactions, into more

complicated models which settle to and remain on the surface is taking place. Aerosols play

an important role in the atmospheric processes on Titan. An understanding of these

processes will help clarify prebiotic chemical and physical processes not only on Titan, but

also on primitive Earth. The Huygens probe offers an opportunity to determine how organic

particles are formed and grow which will, again, clarify their role on the early Earth.

A powerful analytical instrument, capable of addressing the above exobiology and other

science questions, was recently proposed by the authors for the Huygens Probe. It is

comprised of an aerosol and gas sampler and processor and a gas chromatograph - ion

mobility spectrometer. The Instrument will be able to measure complex organics that make up

the collected aerosols to the ~1 ppm level. Gases will be measured to the ~10 ppb. Because

the Titan atmosphere is expected to be quite complex, a gas chromatograph - ion mobility

spectrometer is used to provide unequivocal identification of the components of the analytes.

Further details of the science questions to be investigated will be discussed and the proposed

instrument will be described. Expected results and their implications will also be addressed.

101
ANALYSIS

N9 2-._ 13 658 j.

w

OF MODEL TITAN ATMOSPHERIC COMPONENTS

USING ION MOBILITY SPECTROMETRY

D. R. Kojiro*

NASA Ames Research Center,

M. J. Cohen, R. F. Wernlund and R. M. Stimac

PCP, Inc.,

D. E. Humphry

SETI Institute

and

N. Takeuchi

TMA/Norcal

A detailed knowledge of the history and abundances of the biogenic elements and

their compounds throughout the solar system can provide exobiologists with a basis

for understanding the conditions necessary for chemical evolution and the origin of

life. Flight experiments conducting in situ analyses have already produced a wealth of

information on the environments of Venus and Mars. Future missions will require

instrumentation capable of providing identification and quantitation of a multitude of

molecular species over a wide range of concentrations. As one of these future

missions, NASA, in conjunction with the European Space Agency, plans to send a

spacecraft to the Saturnian system (Cassini mission) to study Saturn and its satellite,

Titan. An analysis of Titan's atmosphere presents a highly challenging task because

of the complexity of the analysis, particularly in terms of the many species of organic

carbon compounds that may be present, and the very low concentration levels that

must be detected. The Gas Chromatograph - Ion Mobility Spectrometer (GC-IMS) has

been proposed as an analytical technique for the analysis of Titan's atmosphere.

The Ion Mobility Spectrometer (IMS) is an atmospheric pressure, chemical detector

that produces an identifying spectrum of each chemical species measured. When the

IMS is combined with a Gas Chromatograph (GC) as a GC-IMS, the GC is used to

separate the sample into its individual components, or perhaps small groups of

components. The IMS is then used to detect, quantify, and identify each sample

component. Conventional IMS detection and identification of sample components

depends upon a source of energetic radiation, such as beta radiation, which ionizes

the atmospheric pressure host gas. This primary ionization initiates a sequence of ionmolecule reactions leading to the formation of sufficiently energetic positive or

negative ions, which in turn ionize most constituents in the sample. In conventional

IMS, this reaction sequence is dominated by the water cluster ion. However, many of

the light hydrocarbons expected in Titan's atmosphere cannot be analyzed by IMS

using this mechanism at the concentrations expected. Research at NASA Ames and

PCP Inc., has demonstrated IMS analysis of expected Titan atmospheric components,

including saturated aliphatic hydrocarbons, using two alternate sample ionizations

mechanisms. The sensitivity of the IMS to hydrocarbons such as propane and butane

was increased by several orders of magnitude. Both ultra dry (waterless) IMS sample

ionization and metastable ionization have successfully been used to analyze a model

Titan atmospheric gas mixture.

102
 92=13659

A SILICONE COLUMN FOR GC ANALYSIS OF POLAR AND NONPOLAR

CHEMICALS

T. C. Shen*

SETI Institute, NASA Ames Research Center

The investigation of the Saturnian system is being proposed jointly by NASA and ESA.

The mission is scheduled for a launch in 1996. The mission provides an opportunity

for close observation and exploration of Saturn's atmosphere, the complex Saturnian

system of satellites and rings, Titan (Saturn's planet-sized moon), and Saturn's

magnetosphere. The mission gives special attention to Titan which is blanketed by a

thick, opaque atmosphere. An atmospheric probe will be deposited into the Titan

atmosphere for in situ measurement during a slow, three hours descent to the surface.

The results from this analysis may provide the information which is important to the

research of chemical evolution, and the origin of life.

We have developed an analytical system as a part of the Titan Aerosol Gas

Experiment (TAGEX), a proposed experiment for the Cassini mission. This system will

use two highly sensitive detectors, MID (metastable ionization detector) and IMS (ion

mobility spectrometer). Unfortunately, when commercial columns are utilized with

these highly sensitive detectors, volatile components continuously bleed from the

column and interfere with the detector. In addition, light columns must be able to

separate polar and nonpolar organic chemicals within 10-15 minutes under isothermal

conditions for the Titan mission. Therefore, we have developed a highly crosslinked

silicone polymeric packed column which is able to efficiently separate amines,

alcohols, and hydrocarbons with retention times less than 15 minutes at 100°C

isothermal condition.

103
GAS

5/92-- 13 660 .J.

CHROMATOGRAPHIC CONCEPTS FOR THE ANALYSIS OF

PLANETARY ATMOSPHERES

J. R. Valentin* and D. K. Cullers

NASA Ames Research Center,

K. W. Hall

San Jose State University,

R. L. Krekorian

SETI Institute

and

J. B. Phillips

Southern Illinois University at Carbondale

Over the last few years, new GC concepts have been developed for use on board

spacecraft or any other restricted environments for determining the chemical

composition of the atmosphere and surface material of various planetary bodies.

Future NASA missions include an entry probe that will be sent to Titan and various

spacecraft that will land on Mars. In order to be able to properly respond to the

mission science requirements and physical restrictions imposed on the instruments by

these missions, GC analytical techniques are being developed in our Branch. Some

of these techniques include hardware and mathematical techniques that will improve

GC sensitivity and increase the sampling rate of a GC descending through a planetary

atmosphere.

The technique of Multiplex Gas Chromatography (MGC) is an example of a technique

that was studied in a simulated Titan atmosphere. In such an environment that

atmospheric pressure at instrument deployment is estimated to be a few torr. Thus, at

such pressures the small amount of sample that will be acquired might not be enough

to satisfy the detection requirements of the gas chromatograph. In MGC many

samples are pseudo-randomly introduced to the chromatograph without regard to

elution of preceding components. The resulting data is then reduced using

mathematical techniques such as cross-correlation or Fourier Transforms.

Advantages realized from this technique include: improvement in detection limits of

several orders of magnitude and increase in the number of analyses that can be

conducted in a given period of time.

Results proving the application of MGC at very low pressures emulating the same

atmospheric pressures that a Titan probe will encountered when the instruments are

deployed will be shown. The sample used contained hydrocarbons that are expected

to be found in Titan's atmosphere. In addition, a new selective modulator was

developed to monitor water under Martian atmospheric conditions. Since this

modulator is selective only to water, the need for a GC column is eliminated. This

results in further simplification of the instrument.

104
 92"13661

THE RELATIVE IMPORTANCE OF PREBIOTIC SYNTHESIS ON

THE EARTH AND INPUT FROM COMETS AND METEORITES

S. L. Miller*

Department of Chemistry, University of California, San Diego

We have been studying the prebiotic synthesis of hydrogen cyanide and formaldehyde

by the action of electric discharges on various model primitive atmospheres containing

CH4, CO and CO2. Photochemical production rates would also have been important

and have been calculated for HCN and H2CO. A reasonable rate of synthesis of

amino acids from these sources is about 10 n moles cm-2yr -1 or 0.10 moles cm-2 in 10 7

yrs. This would give a concentration of 3 x 10-4 M in an ocean of the present size (300

liters cm-2). The amino acids cannot accumulate over a longer period because the

entire ocean passes through the 350°C submarine vents in 107yrs, which

decomposes all the organic compounds.

A number of workers have calculated the influx of comets and meteorites on the

primitive earth, both as a destructive process for organic compounds and for any life

that was present, as well as a source of organic compounds. Some of the amino acids

from the meteorite proposed to have hit the earth 65 x 106 yrs ago have been detected

at the Cretaceous/Tertiary boundary sediments.

The problem with proposing a large scale input of organic compounds from meteorites

and comets is that they must survive passage through the atmosphere and impact.

There are some processes that would allow survival such as showers of centimeter to

meter sized meteorites and various aerodynamic braking processes for larger objects.

Even if a significant amount of the organic material survived impact, the destructive

processes in the hydrothermal vents would remove these compounds on the average

in 107 yrs or less. If it is assumed that the input rate was sufficient to overcome these

destructive processes, then too much carbon and water, especially from comets, would

have been added to the surface of the earth. We conclude that while some organic

material was added to the earth from comets and meteorites, the amount available

from these sources at a given time was only a few percent of that from earth based

syntheses.

105

r
i!i
Poster Session

107 PRECEDING PAGE BI.A_K NOT FI',-MED
N92-13662. ,

"LIFE ON ICE, ANTARCTICA AND MARS"

D. T. Andersen

Lockheed Engineering and Sciences Company,

C. P. McKay

NASA Ames Research Center,

R. A. Wharton

Desert Research Institute,

C. Sagan and S. W. Squyres

Laboratory for Planetary Studies, Cornell University,

and

G. M. Simmons

Virginia Tech

"Within our solar system, there are two worlds where rock and ice and chilling

winds rule bleak landscapes. Once both were warmer, and rivers wandered

through valleys where today the highest temperatures just barely pass the

melting point of liquid water. In one of them winter lasts four months of freezing

darkness. Upon the other, winter has lasted three billion years or more. Two

lands where life had a chance to flourish. Two lands where - at first - it seems

no trace of life remains. But one of them is rich in hidden life, though alien and

strange. And the other is a planet we yearn to explore with the wisdom gained

from discoveries. This is the story of Antarctica and Mars, a courageous and

astonishing search for life that has taken humans deep below the icy crust of

lakes near Earth's south pole, and given us tools to search for ancient life on the

planet Mars." FromUFE ONICE, ANTARCTICAANDMARS

The study of the origin of life and the prospects for human exploration of Mars are two themes

developed in a new 57-minute film, Life on Ice, Antarctica and Mars, produced by the

lnnerSpace Foundation and WHRO Television for broadcast by PBS. What follows is a brief

explanation of the film and how it relates to the future human exploration of space.

The film is about exploration in the traditional sense - Antarctica, diving, living in tents,

adventure, risk - and in a not-so-traditional sense - the rationale for sending people to the

planet Mars. This film relates directly to the Space Exploration initiative now under study by

NASA and the National Space Council. It educates the viewer about the planet Mars and

helps explain the need for pursuing such an initiative, while conveying its inherent excitement.

The story line is easy to follow, the photography is spectacular, and the narration is excellent.

"Life on Ice" is also about the study of microbial life forms thriving on the bottom of perp_.tually

ice-covered (up to 18 feet thick) lakes in the dry valleys of Antarctica. The research team

featured in the film includes exobiologists Dale Andersen (now with Lockheed Engineering &

Sciences Co, in support of the Life Sciences Division at NASA Headquarters); planetary

scientist Christopher P. McKay of NASA's Ames Research Center; exobiologist Robert

Wharton of the Desert Research Institute in Reno, Nevada (at NASA Headquarters for 1989-91

under the Visiting Senior Scientist program); biologist George Simmons of the faculty of

Virginia Tech; planetary geologist Steve Squyres of Cornell University; John D. Rummel, the

Exobiology Program Manager for the Life Sciences Division, NASA Headquarters; and Carl

Sagan, David Duncan Professor of Astronomy and Space Sciences, and Director of the

Laboratory for Planetary Studies at Cornell University.

The film, written by Geoff Haines-Styles and produced by Mark Jenkins, relates Antarctic

research to the study of the origins of life and to the question of whether life ever existed on

Mars (or anywhere else beyond Earth). The film also shows how the working experience

gained by this research team relates to planning for human missions to Mars or other harsh,

isolated environments.

•" 108
 92"13663

IDENTIFICATION AND CHARACTERIZATION OF EXTRATERRESTRIAL

NON-CHONDRITIC INTERPLANETARY DUST

D.F. Blake and and R.H. Fleming*

NASA Ames Research Center, Moffett Field, CA 94035

*Charles Evans & Associates, 301 Chesapeake Dr., Redwood City, CA 94063

Interplanetary Dust Particles (IDPs) are among the most pristine and primitive extraterrestrial materials

available for direct study. Most of the stratospheric particles selected for study from the JSC Curatorial

Collection have been chondritic in composition (major element abundances within a factor of two of

chondritic meteorites) because of this composition virtually ensures that the particle is from an

extraterrestrial source.

It is likely that some of the most interesting classes of IDPs have not been recognized simply because they

are not chondritic or do not fit established cdteda for extraterrestrial origin. Indeed; mass spectroscopy

data from the Giotto flyby of comet Halley indicate that a substantial fraction of the dust is in the sub-micron

size range and that a majority of these particles contain C,H,O, and/or N as major elements.

The preponderance of CHON particles in the coma of Halley implies that similar particles may exist in the

JSC stratospheric dust collection. However, the JSC collection also contains a variety of stratospheric

contaminants from terrestrial sources which have these same characteristfcs. Because established cdteda

for extraterrestrial origin may not apply to such particles in individual cases, an integrated approach is

required in which a variety of analysis techniques is applied to the same particle.

Non-chondritic IDPs, like their chondritic counterparts, can be used to elucidate preo and early solar

system processes and conditions. The study of non-chondritic IDPs may additionally yield unique

information which bears on the nature of cometary bodies and the processing of carbonaceous and other

low atomic number materials.

We will utilize a suite of complementary techniques, including Low Voltage Scanning Electron Microscopy

(LVSEM), Energy-Dispersive X-ray Microanalysis (EDX), Secondary Ion Mass Spectrometry (SIMS)

isotope-ratio imaging and Analytical Electron Microscopy (AEM) to accomplish the following two

objectives: 1. Develop cdteria for the unequivocal identification of extraterrestrial non-chondritic IDPs,

and 2. Infer IDP parent body, solar nebula and pre-solar conditions through the study of phases, textures

and components contained within non-chondritic IDPs. The general approach we are taking is designed

to maximize the total information obtained from each particle. Techniques will be applied in order from

least destructive to most destructive.

LVSEM is the premier technique for the high resolution non-destructive surface imaging of particles. The

powerful combination of LVSEM with Secondary Ion Mass Spectroscopy (SIMS) isotope ratio imaging

allows for the first time the identification of isotopic hot spots and their correlation with original phases

and/or morphological features within intact particles.

The application of SIMS isotope ratio imaging to ultramicrotome thin sections of particles allows for the first

time the complete characterization by Analytical Electron Microscopy (AEM) of phases which harbor

isotopic anomalies.

The result of this investigation will be a data set on a variety of non-chondritic IDPs including surface

morphology, bulk composition, D/H isotopic ratios and nanometer-scale phase identification using AEM.

From these date we anticipate that objective cdteria can be established for the extraterrestrial and/or

interstellar origin(s) of non-chondritic carbonaceous IDPs. Using known stability relationships, phase

equilibria and the like, it should be possible to constrain interstellar, pre- and early solar system condition

extant during formation and aggregation of the parent bodies represented by the IDPs.

109
N92-13664 j.

LDEF POST-RETRIEVAL EVALUATION OF EXOBIOLOGY INTERESTS

T.E. Bunch

NASA Ames Research Center,

F. Radicatl di Brozolo

Charles Evans & Associates

and

R. Fitzgerald

Diafin

Cursory examination of LDEF (Long Duration Exposure Facility) shows the existence

of thousands of impact craters of which less than 1/3 exceed 0.3 mm in diameter; the

largest crater is 5.5 mm. Few craters show oblique impact morphology (low impact

angle) and, surprisingly, only a low number of craters have recognizable impact debris

(ejecta spray patterns, crater interior impactor residue). Study of this debris could be

of interest to Exobiology in terms of C content and carbonaceous materials. All craters

> 0.3 mm have been imaged and recorded into a data base by the preliminary

examination team (the "A-Team"). Various portions of LDEF surfaces are

contaminated by outgassed materials from experimenters trays, in addition to LDEF

autocontamination and impact with orbital debris not of extraterrestrial origin.

Because IDPs (interplanetary dust particles, a.k.a, cosmic dust) nominally impacted

LDEF at velocities > 3 km/s, the potential for intact survival of carbonaceous

compounds is mostly unknown for hypervelocity impacts. Calculations show that for

solid phthalic acid (a test impactor), molecular dissociation would not necessarily

occur below 3 km/s, if all of the impact energy was directed at breaking molecular

bonds, which is not the case (e.g., most energy is used for crater formation and

impactor fragmentation). We performed hypervelocity impact experiments (LDEF

analogs) by using the Ames Vertical Gun Facility. Grains of phthalic acid and the

Murchison meteorite (grain dia.= 0.2 mm for both) were fired into AI plate at 2.1 and 4.1

km/s, respectively. Laser ionization mass spectrometry (LIMS) microanalyses of the

impactor residues confirm that phthalic acid molecules remain intact on impact at 2.1

km/s and some of the carbonaceous compounds in Murchison retain their molecular

integrity on impact at 4.1 km/s. We assume that some of the LDEF craters were formed

at impact velocities < 5 km/s and conclude that meaningful biogenic elemental and

compound information can be obtained from IDP impacts on LDEF.

An LDEF catalog of preliminary observational data and imagery will be made

available within the 1991 fiscal year (Johnson Space Center, NASA). Sample

analysis opportunities will also be announced in the near future through the LDEF

Project Office (Langley Research Center, NASA).

110
N92-13665

RECENT SPECTROSCOPIC FINDINGS CONCERNING CLAY/WATER

INTERACTIONS AT LOW HUMIDITY: POSSIBLE APPLICATIONS TO

MODELS OF MARTIAN SURFACE REACTIVITY

L. Coyne, J. Bishop and L. Howard

San Jose State University/NASA Ames Research Center

and

T. W. Scattergood

SUNY Stony Brook/NASA Ames Research Center

The Viking expedition to Mars provided an invaluable, but still little appreciated lesson for diehard Vitalists among the scientific community and public at large. Not every chemical

sequence of cosmochemical evolutionary significance is mediated by "living cells," even those

with cosmochemical ramifications for the generation and maintenance of complex life forms.

Egotists that we all are, life forms are interesting to us in how they produce their chemistry and

in what they can achieve using it. However, cells are by no means unique in the chemistry

that they can produce. Viking performed four chemical tests for cellular life forms; Mars

passed all but the requirement for significant quantities of organic carbon. Mineral surfaces

proved capable of most, if not all, of the chemistry formerly tagged as diagnostic of cellular life.

Whereas we now reluctantly acknowledge the chemical facility of mineral systems, we still

understand it only primitively. Nor do we even know the surface mineralogy of our closest

planetary neighbors. Mineralogists and space scientists, while cognizant of the centrality of

planetary mineralogy in planetary formation and evolution, have yet to fully credit the actuality

that, among mineral types consistent with the Viking elemental analysis, some are more

interesting than others on the basis of their capacity to drive surface chemistry of types

producing precursors and constituents of cellular life. Among those minerals "more equal" to

Exobiologists are the phyllosilicates, carbonates and phosphates that are postulated or known

to be catalysts of biologically interesting organic chemistry, or to be relics of cellular life forms.

Analysis of Viking elemental data and surface chemical simulations allow consideration of

variably iron cation-exchanged montmorillonites as plausible MarSAMs. Analysis of Martian

surface reflectance data are more inclusive than, even at odds with this simple model.

However, quantitatively estimated mineralogy using reflectance data is a risky business in the

light of our abysmally developed repository of ground based truth regarding structurally

defective, non-stoichiometric materials and mineral mixtures in the less than 2_ particle size

range.

We have extended a feasibility study assessing the utility of our adaptation of near infrared

correlation spectroscopy to quantifying iron and adsorbed water in some clay-based

MarSAMs. The work was intended to constitute Phase I of a novel approach to identifying

optical analytical wavelength regions, not only for important mineral classes, but for chemically

active centers within them. Many of these centers are common to unrelated mineral classes

and of disproportionate influence relative to the mineral structure as a whole in determining

the surface reactivity of mineral surfaces. We previously reported linearity between

reflectance and total iron and total moisture over a large range of both key variables. We also

discovered interesting relationships between the intensity of iron bands and the relative

humidity of the systems. These relationships now have been confirmed. We show also that, in

the low humidity range, reflectance is linearly dependent on a different kind of water from that

best representing the full humidity range (the kind of water associated, in clays, with surface

acidity). These relationships and the sensitivity and capability of quantitation of NIR data

indicate high promise of the method for being able to predictively correlate mineral

spectroscopy with the production of reactive surface intermediates or products of surface

reactions.

111
N9 2- 13 666 .],

CRYSTAL-FIELD-DRIVEN REDOX REACTIONS: HOW COMMON

MINERALS SPLIT H20 AND CO2 INTO REDUCED H= AND C

PLUS OXYGEN

F. Freund, F. Batllo, R. C. LeRoy, S. Lersky, M. M. Masuda,

San Jose State University

and

S. Chang

NASA Ames Research Center

It is difficult to prove the presence of molecular H2 and reduced C in minerals

containing dissolved H2 and CO2. We developed a new technique by which we can

unambiguously show that minerals grown in viciously reducing environments contain

peroxy in their crystal structures. These peroxy represent interstitial oxygen atoms left

behind when the solute H20 and/or CO2 split off H2 and C as a result of internal redox

reactions, driven by the crystal field. The observation of peroxy affirms the presence of

H2 and reduced C. It shows that the solid state is indeed an unusual reaction medium.

112
 92-13667

KINETICS OF THE TEMPLATE-DIRECTED OLIGOMERIZATION OF

GUANOSINE 5'-PHOSPHATE-2-METHYLIMIDAZOLIDE: EFFECT OF

TEMPERATURE ON INDIVIDUAL STEPS OF REACTION

A. Kanavarioti, C. F. Bernasconi and D. J. Alberas

Chemistry Department, University of California, Santa Cruz, CA 95064

Non-enzymatic, template-directed reactions have been proposed as models for

prebiological polynucleotide synthesis (Orgel, 1986). Chemically activated

mononucleotides react in the presence of a polynucleotide, acting as the template in a

Watson-Crick base-pairing fashion, and form the complementary daughterpolynucleotide. Phosphoimidazolide-activated nucleotides have been used

successfully as substrates in these reactions (Inoue and Orgel, 1983).

We studied the kinetics of the guanosine 5'-monophosphate-2-methylimidazolide (2-

MelmpG) reaction in aqueous pH 8.0 solutions in the presence and in the absence of

polycytidylate (poly(C)), acting as the template at 6°C, 23°C and 37°C. In the absence

of the template the major reaction pathway of 2-MelmpG is hydrolysis of the P-N bond

to form the unreactive guanosine 5'-monophosphate (5'-GMP) and 2-methylimidazole.

Concentrated solution of 2-MelmpG (>0.02 M) in the absence of the template form only

small amount of dinucleotide, (pG)2, but in the presence of poly(C), oligoguanylates,

(pG)n with 2<n<40, can be detected (Inoue and Orgel, 1982).

We were able to determine the rate constants for individual steps of this reaction. Our

conclusions can be summarized as follows: (i) The effect of the template on the rate of

the internucleotide bond formation, which corresponds to an approximately 200-fold

catalysis (obtained from kn/k2 where kn the biomolecular rate constant of reaction of

an oligomer with n>5 and k2 the rate constant of dimerization of 2-MelmpG in the

absence of poly(C) stays constant in the temperature range of 6°C to 37°C. This

implies similar activation energies for the two reactions, i.e. the dimerization in the

absence of the template and the elongation in the presence of the template. This

result may suggest that the template acts as a site for bringing the reactants together

without affecting the transition state of the internucleotide bond formation (not a true

catalyst). (ii) In the early stages of the reaction hydrolysis of 2-MelmpG, initiation of the

oligomerization (k2, k3 and k4) and elongation (kn, 5<n<11), occur simultaneously

and compete in such a way to give rise to a larger total percentage of shorter

oligomers (n<5) at the lower temperature. This competition implies that for a constant

supply of activated monomer the oligomerization process would favor longer

oligomers at the higher temperature.

113

L .... : ......... ;.................. -=--
N92-13668

MACROMOLECULAR RECOGNITION: STRUCTURAL ASPECTS

OF THE ORIGIN OF THE GENETIC SYSTEM

Robert Rein*, W. Andrzej Sokalski, Dov Barak, Ning Luo,

Theresa Julia Zielinski and Masayuki Shibata

Department of Biophysics

Roswell Park Memorial Institute

Buffalo, NY 14263

Theoretical simulation of prebiotic chemical processes is an invaluable tool for probing

the phenomenon of evolution of life. Using computational and modeling techniques

and guided by analogies from present day systems we week to understand the

emergence of the genetic apparatus, enzymatic catalysis and protein synthesis under

prebiotic conditions.

Modeling of the ancestral aminoacyl-tRNA-synthetases (aRS) may provide important

clues to the emergence of the genetic code and the protein synthetic machinery.

Assuming that the catalytic function evolved before the elements of specific recognition

for a particular amino acid, we are exploring the minimal structural requirements for

the catalysis of tRNA aminoacylation. The first step reaction, a formation of an

aminoacyl adenylate was studied in the framework of ab initio MO theory. Based on

the available inhibitor-TyrRS complex, the role of individual residues in the vicinity of

the TyrRS active site was examined. The effect of all possible amino acids

substitutions near the active site was studied by estimating differential stabilization of

the corresponding transition complex. Results indicated prominent catalytic role of

His45, His48, Lys225, Lys230 and Lys233. Subsequent sequence analysis indicated

that the pattern of these positively charged residues is conserved among different

aRSs. This led us to propose a hypothesis that the three dimensional orientation of

these positively charged residues may confer the essential catalytic role of the

ancestral aRS. The second reaction, a formation of aminoacyl tRNA was studied by

the molecular modeling system SYBYL with the high resolution crystallographic

structures of the present day tRNA, aRSs complexes. The trinucleotide CCA of the 3'-

end of tRNA is placed into the active site pocket of TyrRS, based upon the interaction

scheme between tRNA GIn and GInRS, and upon the assumed stereochemistry of the

TyrRS:tRNA:Tyr-AMP transition state.

In another possible scenario, RNA enzymatic reactions play a key role in the

emergence of the self-replicating system offering a clue to the onset of enzymatic

catalysis prior to the existence of the protein biosynthetic machinery. Our ultimate goal

is to propose a simple RNA segment that is small enough to be built in the primordial

chemical environment but maintains the specificity and catalytic activity of the

contemporary RNA enzyme. To understand the mechanism of ribozyme catalyzed

reactions, ab initio and semi-empirical (ZINDO) programs were used to investigate the

reaction path of transphosphorylation. A special emphasis was placed on the possible

catalytic and structural roles played by the coordinated magnesium cation. Both the

inline and adjacent mechanisms of transphosphorylation have been studied. The

structural characteristics of the target helices, particularly a possible role for the G.T

pair, is also studied by molecular dynamics (MD) simulation technique.

114
THE 2.5-5.0

 92"13669

p.M SPECTRA OF IO: EVIDENCE FOR H2S AND

H20 FROZEN IN SO2

F. Salama

NASA Ames Research Center/National Research Council,

L. J. Allamandola, F.C. Witteborn, D.P. Cruikshank, S.A. Sanford

and J.D. Bregman

NASA Ames Research Center

The techniques of low temperature spectroscopy are applied here to identify the

constituents of the ices covering the surface of Io, a satellite of Jupiter.

Infrared spectra of Io in the 4000-2000 cm "1 region, including new observational data,

are analyzed using laboratory studies of plausible surface ices.

Besides the well-known absorption bands attributable to sulfur dioxide frosts, four

unidentified infrared spectral features of Io are pointed out. Two are at 2597 cm "1 and

2558 cm "1 and the second pair fall at 3367 cm -1 and 3175 cm -1. These absorptions fall

close to the fundamental X-H stretching modes in H2S and H20 respectively. The

infrared absorption spectra of mixed molecular ices ranging from pure materials, to

binary mixtures of H2S and SO2 (either mixed at different concentrations or layered), to

H20/H2S/SO 2 mixtures are discussed. The effects of ultraviolet irradiation (120 and

160 nm) and temperature variation (from 9 K to 130 K) on the infrared spectra of the

ices are also examined. The comparative study shows that: (1) Io most likely contains

H2S and H20 mixed with SO2. The 2597 cm °1 and 2558 cm -1 bands in the Io spectra

can be accounted for by the absorption of the S-H stretching vibration (vl) in H2S

aggregates and isolated molecules in an SO2 matrix. The weak 3367 cm -_ and 3175

cm-_ bands which vary spatially and temporally in the Io spectra coincide with the v3

and vl O-H stretching vibrations of clusters of H20 complexed with SO2. (2) The

observations are well matched by SO2.matrices containing about 3% H2S and 0.1%

H20 and which have been formed by the condensation of a mixture of the gases onto

a 100 K surface. (3) In the comparison of the spectra using the mixed molecular ice

samples versus the layered ice samples only the former can explain the shifts and

splitting of the absorption bands in the Io spectrum and account for the fact that solid

H2S is observed in the surface material of Io at temperatures and pressures above the

sublimation point of pure H2S. In addition to pointing out the presence of H2S and

H20 on Io, the originality of this study comes from the fact that it is the first to consider

mixed solids in carrying out laboratory simulations of planetary surfaces providing a

realistic simulation of the "dirty" ices covering the surfaces of many satellites.

115
N92-13670 j.

LABORATORY SIMULATION OF THE PHOTOPROCESSING AND WARMUP OF COMETARY AND PRE-COMETARY ICES: PRODUCTION OF

COMPLEX ORGANIC MOLECULES

W. A.Schutte, L. J. Allamandola and S.A. Sanford

NASA Ames Research Center

The recent missions to Comet Halley detected large quantities of organic material on

grains as well as organic molecules in the gas phase. A possible origin of these

materials is the energetic processing of ice mantles on the grains prior to comet

formation, either in the pre-solar nebula or the interstellar medium. We simulated this

process in the laboratory by depositing interstellar ice analogs (H20/CH3OH/CO/NH3)

on a cold (10 K) substrate with simultaneous UV irradiation. The material evaporating

during warm-up of the photolyzed ice as well as the residue remaining at room

temperatures was analysed by a number of techniques. It was found that a large

number of organic molecules of various complexity are synthesized during the

simulation process, stressing the possible significance of UV photolysis for producing

the organic Comet material.

116
BIOLOGICALLY CONTROLLED MINERALS

OF LIFE

 T92- 13 ( 71

AS POTENTIAL INDICATORS

D.E. Schwartz and R.L. Mancinelli

Solar System Branch, NASA Ames Research Center,

and

E. Kaneshiro

University of Cincinnati

Minerals can be produced and deposited either by abiotic or biologic means.

Regardless of their origin, mineral crystals reflect the environmental conditions (e.g.,

temperature, pressure, chemical composition, and redox potential) present during

crystal formation. Biologically-produced mineral crystals are grown or reworked under

the control of their host organism andreflect an environment different from the abiotic

environment. For example, we have gathered sufficient evidence demonstrating that

most biologically controlled minerals have attributes, such as morphologies and

isotopic ratios, which differ from an abiotically produced mineral of the same chemical

composition. In addition, minerals of either biologic or abiotic origin have great

longevities. For these reasons, biologically produced minerals have been proposed

as biomarkers. Biomarkers are key morphological, chemical, and isotopic signatures

of living systems that can be used to determine if life processes have occurred.

To date, more than 60 different minerals have been identified as being produced or

reworked by an assortment of organisms. Several of these minerals and the

organisms that produce them have been well studied, such as magnetite produced by

bacteria and aragonite produced by mollusks. Although some of the minerals

produced by organisms, such as silica produced by diatoms, are abundant, very

widely distributed, and have played an important role in the geologic record, much

work still remains to be done.

The technique of using biologically-produced minerals as biomarkers has great

potential and must be tested. The key to the use of minerals as biomarkers is the

ability to distinguish between abiotically and biologically produced minerals. To

accomplish this, universal traits unique to biologically controlled minerals must be

identified. We have begun studies of biologically controlled minerals produced by the

protist Paramecium tetraurelia since techniques have already been developed to

culture them and isolate their crystalline material, and methods are already in place to

analyze this material. Two direct crystalline phases have been identified. One phase,

whose chemical composition is high in Mg, was identified as struvite. The second

phase, whose chemical composition is high in Ca, has not been previously found

occurring naturally and may be considered a newly discovered material. Analyses are

currently underway to determine the characteristics of these minerals in order to

compare them with characteristics of minerals formed abiotically, but with the same

chemical composition.

117
PHOTOSYNTHETIC REACTION CENTER COMPLEXES FROM

HELIOBACTERIA

J. T. Trost, W. F. J. Vermaas and R. E. Blankenship*

Center for the Study of Early Events in Photosynthesis,

Arizona State University

Photosynthetic reaction centers are pigment-protein complexes that are responsible

for the transduction of light energy into chemical energy. Considerable evidence

indicates that photosynthetic organisms were present very early in the evolution of life

on Earth. The goal of this project is to understand the early evolutionary development

of photosynthesis by examining the properties of reaction centers isolated from certain

contemporary organisms that appear to contain the simplest photosynthetic reaction

centers. The major focus of this project is the family of newly discovered strictly

anaerobic photosynthetic organisms known as Heliobacteria. These organisms are

the only known photosynthetic organisms that are grouped with the gram-positive

phylum of bacteria. The properties of these reaction centers suggest that they may be

the descendants of an ancestor that also gave rise to Photosystem I found in oxygenevolving photosynthetic organisms.

Photoactive reaction center-core antenna complexes have been isolated from the

photosynthetic bacteria He/iobaci//us mobi/is and He/iobacterium gestii by extraction

of membranes with Deriphat 160C followed by differential centrifugation and sucrose

density gradient centrifugation (Trost and Blankenship, Biochemistry 28, 9898-9904,

1989). The purified complexes contain one or more 48,000 Mr peptides that bind both

the photoactive chlorophyll P800 and approximately 25 molecules of antenna

bacteriochlorophyll g. Time-resolved fluorescence spectroscopy indicates that the

antenna pigment are active in energy transfer to P800, exhibiting a major decay time

of 25 ps in both membranes and reaction centers. The absorption and fluorescence

properties of membranes and reaction centers are almost identical, suggesting that a

single pigment-protein complex serves as both antenna and reaction center.

Experiments in progress include sequence determination of the 48,000 Mr reaction

center protein, and evolutionary comparisons with other reaction center proteins.

These experiments are being done using chemical sequencing methods to obtain a

partial sequence, followed by oligonucleotide synthesis and DNA hybridization to

obtain the gene(s) for the protein(s).

118
AUTHOR INDEX

Alberas, D.J., 48

Aliamandola, L.J., 17, 109, 110

Allen, M., 35

Andersen, D.T., 102

Anicich, V.G., 18

Arakelian, T., 18

Arrhenius 41

Asaro, F., 80

Awramik, S.M., 74

Banin, A., 30

Bar-Nun, A., 97

Barak, D., 46

Batllo, F., 106

Becker, J.F., 25

Bernasconi, C.F., 48

Betz, A., 92

Billingham, J., 77, 87

Bishop, J., 105

Blair, N.E., 20

Blankenship, R.E., 65, 112

Borucki, W.J., 36

Boston, P.J., 27

Bowyer, C.S., 90

Braunitzer, G., 66

Bregman, J.D., 109

Brocker, D.H., 87

Brookshaw, L., 43

Buchanan, B.B., 62

Bunch, T.E., 12, 104

Caldeira, K.G., 84

Canfield, D.E., 71

Carle, G.C., 93, 97

Chang, S., 20, 32, 48, 106

Chyba, C.F., 37, 43

Cohen, M.J., 97, 98

Coyne, L., 42, 105

Cronin, J.R., 20

Cruikshank, D.P., 109

Cullers, D.K., 100

Deamer, D.W., 44

DeFrees, D.J., 15

Des Marais, D.J., 20, 71

DeVincenzi, D.L., 95

Dixon, R.S., 91

Donnelly, C., 90

Ferris, J.P., 39, 97

Fitzgerald, R., 104

Fox, G. 63

Fox, S.W. 66

Freeman, K.H., 67

Freund, F., 106

Friedmann, E.I., 75

Gibson, E.K., Jr., 19

Giver, L.P., 36

Greenberg, J.M., 97

Guillemin, J.C., 39

Hall, K.W., 100

Hanner, M.S., 18

Harmetz, C.P., 19

Hartman, H., 29

Hayes, J.M., 67

Herrick, W., 90

Hinkle, G., 72, 76

Hochstein, L.I., 56, 60

Holland, H.D., 53

Howard, L., 105

Humphry, D.E., 98

Huntington, J.L., 24

Irvine, W.M., 14, 96

Jahnke, L.L., 59

Joyce, G.F., 40

Kanavarioti, A., 48

Kaneshiro, E., 111

Kasting, J.F., 73

Kerridge, J.F., 34

Khare, B.N., 37

Klein, M.J., 89

Knoll, A., 70

Kojiro, D.R., 97, 98

Kozlowski, M., 52

Krekorian, R.L., 100

Kretsinger, R.D., 64

119
Lacey, J.C., Jr., 51

Lampton, M., 90

Lanyi, J.K., 61

Lazcano, A., 50

LeRoy, R.C., 106

Lersky, S., 106

Levine, J.S., 54

Lowe, D.R., 68

Luo, N., 46

MacEIroy, R., 45

Macfarlane, A.D., 53

Mancinelli, R.L., 21, 28, 111

Margulis, L., 72, 76

Mariner, R., 42

Marshall, J_R., 24

Masuda, M.M., 106

McKay, C.P., 26, 27, 29, 31,36, 102

Meyer, M.A., 26

Miller, S.L., 36, 101

Moncrief, N.D., 64

Morowitz, H.J., 55

Nakayama, S., 64

O'Hara, B.J., 97

Oberbeck, V., 97

Orenberg, J., 30

Orgel, L.E., 47

Oro, J., 50

Oscampo-Friedmann, R., 75

Parris, J.E., 36

Phillips, J.B., 100

Pinto, J.P., 35

Pohorille, A., 45

Pollack, J.B., 31, 97

Radicatl di Brozolo, F., 104

Rampino, M.R., 84

Raup, D.M., 81,82

Rein, R., 46

Rice, A., 42

Rosenbach, M.T., 48

Rothschild, L.J., 28

Roush, T., 30, 31

Ruecknagel, P., 66

Sagan, C., 37, 43, 102

Salama, F., 109

Sanford, S.A., 17, 109, 110

Sauke, T.B., 25

Saykally, R., 16

Scattergood, T.W., 36, 97, 105

Schopf, J.W., 69

Schutte, W.A., 17, 110

Schwartz, D.F., 24, 111

Sepkoski, J.J., Jr., 83

Shen, T.C., 99

Shibata, M., 46

Simmons, G.M., 102

Squyres, S.W., 102

Stimac, R.M., 98

Takeuchi, N., 98

Tarter, J., 16, 85

Thomas, P.J., 43

Thompson, W.R., 37

Tielens, A.G.G.M., 17

Trost, J.T., 65, 112

Tsou, P., 23

Usher, D.A.,52

Valentin, J.R., 97, 100

Van Ghyseghem, H., 36

Vermaas, W.F.W., 65, 112

Weber, A.L., 49

Webster, L.D., 88

Wernlund, R.F., 98

Werthimer, D., 90

Wharton, R.A., Jr., 26, 102

White, M.R., 28

Wilson, M., 45

Witteborn, F.C., 109

Yuen, G.U., 20

Yung, Y.L., 35

Zent, A.P., 29

Zielinski, T.J., 46

Zou, X., 52

120
LIST OF ATTENDEES

Diann J. Alberas

2766 E. Uzbeth Ave.

Anaheim, CA 92304

Louis Allamandola

Mail Stop 245-6

NASA Ames Research Center

Moffett Field, CA 94035

Dale Andersen

600 Maryland Ave. SW

Suite 600

Washington, D.C. 20046

Vincent G. Anicich

Jet Propulsion Lab

183-601

4800 Oak Grove Dr.

Pasadena, CA 91109

Frank Asaro

Lawrence Berkeley Laboratory

B 70, Rm. 103

#1 Cyclotron Road

Berkeley, CA 94720

David H. Atkinson

Dept. of Electrical Engineering

Univ. of Idaho

Moscow, Idaho 83843

Stanley Awramik

Department of Geological Sciences

University of California, Santa Barbara

Santa Barbara, CA 93106

Joseph F. Becker

NASA Ames Research Center

Mail Stop 239-12

Moffett Field, CA 94035

Albert Betz

Space Sciences Laboratory

University of California

Berkeley, California 94720

John Billingham

Mail Stop 239-22

SETI Office

NASA Ames Research Center

Moffett Field, CA 94035

David Blake

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Robert E. Blankenship

Department of Chemistry

Arizona State University

Tempe, AZ 85287-1604

Penelope Boston

Complex Systems Research, Inc.

Box 548

10695 Arapahoe Road

Lafayette, CO 80026

Barbara Bowman

Hoffman-LaRoche Inc.

1145 Atlantic Ave. Suite 100

Alameda, CA 94501

Stuart Bowyer

Department of Astronomy

Space Sciences Laboratory

University of California

Berkeley, California 94720

David H. Brocker

Mail Stop 239-22

NASA Ames Research Center

Moffett Field, CA 94035-1000

Bob B. Buchanan

Division of Plant Biology

University of California

Berkeley, CA 94720

Mark A. Bullock

14301 Saratoga Ave. #1

Saratoga, CA 95070

121
J

Theodore E. Bunch

Mail Stop 245-3

NASA Ames Research Center

Moffett Field, CA 94035

Eric Burgess

13361 Frati Lane

Sebastopol, CA 95472

Angelo D. Calabrese

Mail Stop 233-8

NASA Ames Research Center

Moffett Field, CA 94035

Glenn C. Carle

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035

Sherwood Chang

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

John Birger Christensen

1095 McGregor Way

Palo Alto, CA 94306

Christopher F. Chyba

Center for Radiophysics and Space

Research

320 Space Sciences Building

Cornell University

Ithaca, NY 14853

Charles A. Collins

2540 Hawkington Court

Santa Clara, CA 95051

Lelia M. Coyne

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Wanda L. Davis

Mail Stop 245-3

NASA Ames Research Center

Moffett Field, CA 94035

David W. Deamer

Dept. of Zoology

University of California-Davis

Davis, CA 95616

Douglas J. Defrees

Almaden Research Center

650 Harry Road, K84/801

San Jose, CA 95120

David J. Des Marais

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Donald L. DeVincenzi

Space Science Division

Code SS, Mail Stop 245-1

NASA Ames Research Center

Moffett Field, CA 94035

Vincent Vinh Dinh

675 Pinto Drive

San Jose, Ca 95111

Robert S. Dixon

Radio Observatory

2015 Neil Avenue

Ohio State University

Columbus, OH 43210

Charles S. Donnelly

615 Anthony Ct

Sonoma, CA 95476

Douglas E. Fairchild

NASA Ames Research Center

Mail Stop 239-4

Moffett Field, CA 94035

Christine M. Falsetti

NASA Ames Research Center

Mail Stop 233-8

Moffett Field, CA 94035-1000

James P. Ferris

Department of Chemistry

Rensselaer Polytechnic Institute

Troy, NY 12180

122
Ronald H. Fleming

Charles Evans & Associates

301 Chesapeake Drive

Redwood City, CA 94063

Francis X. Flores

G-20 Koshland Way

Santa Cruz, CA 95064

George E. Fox

Department of Biochemical Sciences

University of Houston

Houston, TX 77004

Sidney Fox

Room 408

Life Science Building II

Southern Illinois University

Carbondale, IL 62901

Friedemann Freund

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Georgette George

2650 Keystone Avenue #67

Santa Clara, CA 95051

Cynthia R. Giver

Mail Stop 239-14

NASA Ames Research Center

Moffett Field, CA 94035

Lorraine J. Giver

1061 Sargent Dr.

Sunnyvale, CA 94087

Thomas D. Gutierrez

3516 Benton Street

Santa Clara, CA 95051

Kirsten W. Hall

Department of Physics

San Jose State University

1 Washington Square

San Jose, CA 95125

John M. Hayes

Biogeochemical Laboratories

Geology Building

Indiana University

Bloomington, IN 47405

Aram (NMN) Henesian

SETI Institute

NASA Ames Research Center

Mail Stop 239-12

Moffett Field, CA 94035-1000

Tucker Hiatt

47 Alta Way

Corte Madera, CA 94925

Gregory Hinkle

Botany Department

University of Mass.

Amherst, MA 01003

Larry Hochstein

NASA Ames Research Center

Mail Stop 239-4

Moffett Field, CA 94035

Heinrich D. Holland

Department of Earth and Planetary

Sciences

Harvard University

Cambridge, MA 02138

Fay W. Hsu

33270 Pheasant St.

Fremont, CA 94555

Judith L. Huntington

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035

William M. Irvine

Department of Physics and Astronomy

University of Massachusetts

Amherst, MA 01003

123
"b

Linda Jahnke

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Gerald F. Joyce

Department of Molecular Biology, MB8

Research Institute of Scripps Clinic

10666 N. Torry Pines Rd.

La Jolla, CA 92037

Everett K. Gibson, Jr.

SN2 Planetary Sciences Branch

NASA Johnson Space Center

Houston, TX 77058

Anastassia Kanavariotti

Department of Chemistry

University of California, Santa Cruz

Santa Cruz, CA 95064

James F. Kasting

211 Deike

College of Earth and Mineral Sciences

Pennsylvania State University

University Park, PA 16802

John F. Kerridge

Institute of Geophysics and Planetary

Physics

University of California, Los Angeles

Los Angeles, CA 90024

Harold P. Klein

Biology Department

Santa Clara University

Santa Clara, CA 95053

Michael J. Klein

Mail Stop 303-401

Jet Propulsion Laboratory

California Institute of Technology

4800 Oak Grove

Pasadena, CA 91109-8099

Andrew H. Knoll

Harvard University

Botanical Museum

26 Oxford Street

Cambridge, MA 02138

Daniel R. Kojiro

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035

Robert H. Kretsinger

Department of Biology

University of Virginia

Charlottesville, VA 22901

James C. Lacey

Department of Biochemistry

University of Alabama at Birmingham

Birmingham, AL 35294

Janos K. Lanyi

Department of Physiology and

Biophysics

University of California, Irvine

Irvine, CA 92717

Eric B. Larrivee

NASA Ames Research Center

Mail Stop 233-8

Moffett Field, CA 94035

Edmond Lau

NASA Ames Research Center

Mail Stop 239-12

Moffett Field, CA 94035

Antonio Lazcano

Depto de Biologia, Fac de Ciercias,

UNAM

Apdo. Postal 70-407, Cd. Universitaria

04511, Mexico D.f., Mexico

Jeffrey S. Lee

6248 Current Dr.

San Jose, CA 95123

124
Rodney LeRoy

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035-1000

Joel S. Levine

NASA-Langley Research Center

Hampton, VA 23665-5225

Gilda Loew

Molecular Research Institute

845 Page Mill Road

Palo Alto, CA 94304

D.R. Lowe

Department of Geology

School of Earth Sciences

Stanford University

Stanford, CA 94305-2115

Norman Lynn

Flight International

Lynn/Western Inc.

975 Akire P.O.B. 335

Morgan Hill, CA 95037

Shirley Lynn

Lynn-Western Newswires

P.O. Box 335

Morgan Hill, CA 95037

Robert D. MacEIroy

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Rocco Mancinelli

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035

Lynn Margulis

Department of Botany

University of Massachussetts

Amherst, MA 01002

125

John R. Marshall

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035

Michael M. Masuda

2120 Doxey Drive

San Jose, CA 95131

David Mauzerall

Rockefeller Center

1230 York Ave.

New York, NY 10021

Stanley L. Miller

Chemistry Department

University of California, San Diego

La Jolla, CA 92093

Stefan P. Moelles

Christian-August-Weg 31

2000 Hamburg 55

West Germany

Harold J. Morowitz

207 East Bldg.

George Mason University

Fairfax, VA 22030

David Morrison

Space Science Division

NASA Ames N245-1

Moffett Field, CA 94035

Elaine F. Munoz

NASA Ames Research Center

Mail Stop 239-4

Moffett Field, CA 94035

Bonnie J. O'Hara

NASA Ames Research Center

Mail Stop 239-12

Moffett Field, CA 94035

Vern Oberbeck

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035
Jim B. Orenberg

Department of Chemistry

San Francisco State University

1600 Halloway Ave.

San Francisco, CA 94132

Leslie E. Orgel

The Salk Institute for Biological Studies

P.O. Box 85800

San Diego, CA 92138

John Oro

Department of Biochemical and

Biophysical Sciences

University of Houston

Houston, TX 77204-5500

Roseli Oscampo-Friedmann

Florida State University

Tallahassee, FL 32306

Tanya I. Paris

i3604 Howen Drive

Saratoga, CA 95070

David A. Perlman

San Francisco Chronicle

901 Mission Street

San Francisco, CA 94119

Etta Peterson

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035-1000

Tom Pierson

SETI Institute

2035 Landings Drive

Mountain View, CA 94043

Andrew Pohoriile

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Fillippo Radicati di Brozolo

Charles Evans & Associates

301 Chesapeake Drive

Redwood City, CA 94063

Michael R. Rampino

Earth Systems Group

New York State University

26 Stuyvesant Street

New York, New York 10003

David M. Raup

Department of Geophysical Science

5734 South Ellis Avenue

University of Chicago

Chicago, IL 60637

Robert Rein

Roswell Park Memorial Institute

Building CCC, Suite 218

666 Elm Street

Buffalo, NY 14263

Alexander Rich

Department of Biology

Massachusetts Institute of Technology

Cambridge, MA 02139

Morgan T. Rosenbach

1156 High Street

Thimann Labs

Santa Cruz, CA 95064

Ted L. Roush

NASA Ames Research Center

Mail Stop 245-3

Moffett Field, CA 94035-1000

John D. Rummel

Code SBR

Life Sciences Division

NASA

Washington, DC 20546

Carl Sagan

Center for Radiophysics and Space

Research

Space Science Building

Cornell University

Ithaca, NY 14853

126
Timothy A. Sandstrom

Mail Stop 233-8

NASA Ames Research Center

Moffett Field, CA 94035-1000

Todd B. Sauke

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035-1000

Richard J. Saykally

Department of Chemistry

University of California

Berkeley, CA 94720

Thomas Scattergood

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

J. William Schopf

Director, CSEOL

Geology Building

University of California, Los Angeles

Los Angeles, CA 90024

David F. Schuck

H-5 Koshland Way

Santa Cruz, CA 95064

William A. Schutte

Mail Stop 245-6

NASA Ames Research Center

Moffett Field, CA 94035-1000

Debbie Schwartz

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035-1000

Kenneth R. Schwartz

Mail Stop 243-6

NASA Ames Research Center

Moffett Field, CA 94035-1000

J. John Sepkoski

Department of Geophysical Sciences

University of Chicago

5734 S. Ellis Avenue

Chicago, IL 60637

Joseph Sharp

Mail Stop 200-7

NASA Ames Research Center

Moffett Field, CA 94035-1000

Thomas L. Shen

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035-1000

Pearish J. Smith

131 Palo Verde Terrace

Santa Cruz, CA 95060

Helga Stan-Lotter

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035-1000

Jon F. Stanley

W. 311 32nd Ave.

Spokane, WA 99203

Bradley M. Stone

Department of Chemistry

San Jose State University

San Jose, CA 95192-0101

David M. Stratton

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035-1000

Michael Wm. Stronach

E-6 Koshland Way

Santa Cruz, CA 95064

Michael K. Sulzner

Auhofstr. 126/10

1130 Vienna

Austria

127
David P. Summers

806 Coleman Ave, #14

Menlo Park, CA 94025

Norishige Takeuchi

NASA Ames Research Center

Mail Stop 239-12

Moffett Field, CA 94062

Jill C. Tarter

Mail Stop 239-22

NASA Ames Research Center

Moffett Field, CA 94035

Anne F. Tharpe

NASA Ames Research Center

Mail Stop 239-4

Moffett Field, CA

Peter Tsou

Jet Propulsion Laboratory

Mail Stop 233-306

Pasadena, CA 91109

Richard J. Twarowski

N 244-14

NASA Ames Research Center

Moffett Field, CA 94035

David A. Usher

Department of Chemistry

Cornell University

Ithaca, NY 14853

Jose R. Valentin

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA 94035

Judith M. Vandonzel

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA 94035

Willem F. J. Vermaas

Department of Botany

Arizona State University

Tempe, AZ 85287-1601

128

Peter W. Waller

Mail Stop 204-12

NASA Ames Research Center

Moffett Field, CA 94035

Arthur L. Weber

The Salk Institute for Biological Studies

P.O. Box 85800

San Diego, CA 92037

Esther Weber

The Salk Institute

P.O. Box 85800

San Diego, CA 92037

Larry D. Webster

Mail Stop 239-27

NASA Ames Research Center

Moffett Field, CA 94035

Robert A. Wharton

NASA Headquarters

Code SBR

Washington, DC 20546

Jessica W. Wilcox

245 Jasmine St.

Denver, CO 80220

Michael A. Wilson

3610 Lakeshore Ave.

Oakland, CA 94610

Taifeng Wu

CEL

The Salk Institute

San Diego, CA 92138

Richard S. Young

Code MD RES

KSC

Kennedy Space Center, FL 32899

George U. Yuen

Department of Chemistry

Arizona State University

Tempe, AZ 85287
Yuk Ling Yung

170-25

Division of Geological and Planetary

Sciences

California Institute of Technology

Pasadena, CA 91125

Kevin Zahnle

Mail Stop 245-1

NASA Ames Research Center

Moffett Field, CA 94035

Aaron P. Zent

Mail Stop 245-3

Space Sciences Division

NASA Ames Research Center

Moffett Field, CA 94035

129
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"1. AGENCY USE ONLY (Leave blank) 2. REPORTDATE 3. REPORTTYPE AND DATES COVERED

October 1991 Conference Publication

4. TITLE AND SUBTITLE S. FUNDING NUMBERS

Fourth Symposium on Chemical Evolution and the Origin

and Evolution of Life

6.AUTHOR(S)

Robert A. Wharton, Jr., Dale T. Andersen, Sara E. Bzlk,

and John D. Hummel, Editors

7. PERFORMING ORGANIZATION NAME(S) AND ADDRES$(ESi' ' '

Life Sciences Division

Office of Space Science and Applications

Wshington, D.C. 20546

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Admlnstratlon

Washington, D.C. 20546

199-52

8. PERFORMING ORGANIZATION

REPORTNUMBER

10. SPONSORING/ MONITORING

AGENCY REPORTNUMBER

NASA CP-3129

11.SUPPLEMENTARYNOTES

Robert A. Wharton, 3r., and John D. Hummel: NASA Headquarters, Washington, D.C.

Dale T. Andersen: Lockheed Engineering & Sciences Company, Washington, D.C.

Sara E. Bzik: Ames Research Center, Moffett Field, California.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclasslfled/Unlimlted

Subject Catego_ry 55

12b. DISTRIBUTION CODE

13. ABSTRACT(Maximum200word$)

This symposium was held at the NASA Ames Research Center, Moffett Field, California

July 24-27, 1990. The NASA Exobiology principal investigators reported their

recent research findings. Scientific papers were presented in the following

areas: cosmic evolution of blogenlc compounds, preblotlc evolution (planetary

and molecular), early evolution of llfe (biological and geochemical), evolution

of advanced llfe, solar system exploration, and the Search for Extraterrestlal

Intelligence (SETI).

14. SUBJECTTERMS

exobiology, biological evolution, chemical evolution, planetar 3

evolution, extinction, solar system, exploration, Titan, planetary atomsphere, SETI

17. SECURITYCLASSIFICATION 18. SECURITYCLASSIFICATION 19, SECURITYCLASSIFICATION

OF REPORT OF THIS PAGE OF ABSTRACT

Unclassified Unclassified

NSN 7540-01-280-5500

i15. NUMBER OF PAGES

132

16. PRICECODE

A07

20. LIMITATION OF ABSTRACT

Standard Form 298 (Hey 2-89)

Prescribed by AN_I Std Z39-18

298-102

NASA-LanKIey , 1991