NASA Conference Publication 2425

Second Symposium on

Chemical Evolution

and the Origin

Evolution of

and

Life

Edited by

Donald L. DeVincenzi

NASA Headquarters

Washington, D.C.

Patricia A. Dufour

The George Washington University

Washington, D.C.

Proceedings of a symposium sponsored by the

National Aeronautics and Space Administration

and held at NASA Ames Research Center

Moffett Field, California

July 23-26, 1985

NfiSA

National Aeronautics

and Space Administration

Scientific and Technical

Information Branch

1986
FoPeword

This report includes the program, session summaries,

abstracts, and list of participants from the "Second Symposium on

Chemical Evolution and the Origin and Evolution of Life," held

July 23-26, 1985 at the NASA Ames Research Center, Moffett Field,

CA and organized by Donald L. DeVincenzi.

The purpose of the symposium was for the NASA Exobiology

Program principal investigators to present their research

progress and to encourage the scientists in different exobiology

disciplines to exchange information. More than 165 participants

attended, including the principal investigators, staff members of

the NASA centers involved in exobiology, graduate students, and

other interested guests.

This symposium is held approximately every three years. The

first symposium was held August 2-4, 1982 at the NASA Ames

Research Center (see NASA Conference Publication 2276).

Additional information about the Exobiology Program, such as the

annual bibliography of scientific reports and articles sponsored

by the program, may be obtained from the NASA Headquarters

Program Office.

We would like to thank Vera Buescher for coordinating the 1985

symposium at the NASA Ames Research Center. The scientific

session summaries were prepared by the session chairmen.

pRECEDINQPAGIEBI.ANKNOTIFILJliD

iii
Table of Contents

Page

Foreword ........................... iii

Introduction .......................... I

Program ............................ 5

Scientific Session Summaries .................. 17

Abstracts

Sesslon I: Cosmic Evolution of Biogenic Compounds ....... 39

Sesslon II: Prebiotic Evolution--Planetary .......... 46

Sesslon III: Solar System Exploration ............. 51

Sesslon IV: Prebiotic Evolution--Molecular .......... 60

Sesslon V: Early Evolution of Life--Geochemical ........ 80

Sesslon VI: Early Evolution of Life--Biological ........ 86

Sesslon VII: Evolution of Advanced Life ........... 101

Sesslon VIII: Search for Extraterrestrial Intelligence . . . 106

Author Index .......................... 117

Appendix: Symposium Participants .............. 119

P ,E BI.A NOT Fn.MED

V
Introduction

NASA's Exobiology Program is a multidisciplinary and an

interdisciplinary research effort directed towards understanding

fundamental questions concerning the origin, evolution, and

distribution of life and life-related molecules throughout the

universe. The unifying concept underlying all research in

exobiology is that the origin and evolution of life is an

integral part of the origin and evolution of stars and planets;

thus, life is a product of a continuum of physical and chemical

processes that started with the origin of the universe itself.

In keeping with this theme, the Exobiology Program encompasses

four major research areas, each addressing (in a chronological

sense) the major epochs associated with the origin and evolution

of life on a planet: I) cosmic evolution; 2) prebiotic

evolution; 3) early evolution of life; and 4) evolution of

advanced life forms. The program is intriguing because of the

fundamental questions it addresses, complex because of the need

for research in disciplines as diverse as radioastronomy and

molecular biology, and scientifically sound as measured by the

continued excellence of its research product.

The classic experiments of Miller and Urey, demonstrating the

abiotic synthesis of essential biomolecules, were followed by a

marked progression or evolution of research ideas that can be

characterized as follows: precise identification of prebiotic

simulation products; tests of the generality of conditions under

which these syntheses occur; examination of extraterrestrial

materials and environments for evidence of similar compounds and

processes; adaptation of organisms to simulated extraterrestrial

environments; the search for life in lunar samples, on Mars and

beyond; and probing the origin of biological structures,

metabolic processes, and the genetic code. NASA-sponsored

research in these areas has been highlighted by several key

discoveries, including the demonstration of the abiotic origin of

meteoritic biomolecules, expansion of the range of environmental

extremes over which organisms can adapt, characterization of the

unusual surface chemistry on Mars, determination of the earliest

microbiological phylogenetic relationships, and development of

the role of clays in the origin of essential biopolymers.

It can be seen that achieving an understanding of exobiology

questions requires a methodical research strategy which traces

the history of the biogenic elements from their origins in

stellar formation processes, through the chemical evolution of

molecules essential for life, and into primitive and ultimately

complex living systems. This research strategy involves the

synthesis of data collected from solar system exploration
missions, ground-based and orbiting observatories, and

ground-based and orbiting laboratories.

Solar system exploration spacecraft provide information

concerning the potential for life on and the physical and

chemical characteristics of planets, planetary satellites,

planetesimals and primitive bodies of our solar system--the one

stellar system in which we know life originated. These data

provide insight on how physical and chemical properties of the

biogenic elements and compounds may have influenced the course of

events during the formation of the solar system and the bodies in

it. Direct studies of biogenic elements and compounds in comets,

asteroids, planets and their satellites, and dust in interstellar

and interplanetary space, are needed to achieve two major

objectives. The first is to clarify the relationship between

these bodies and the second is to establish the present

distribution of the biogenic elements and compounds in the solar

system as a firm foundation upon which to build a better

understanding of the way in which the dynamics of nebular

evolution and planetary accretion distributed the biogenic

elements and compounds throughout the solar system.

Ground-based and especially orbiting observatories provide a

means to elucidate the processes associated with star formation

and the development of planetary systems, with particular

emphasis on the organic chemical processes associated with these

events. Observational data are used to assess the abundance and

interaction of the biogenic elements into compounds from which

life may derive in stellar systems. Indeed, the fact that

organic compounds in increasing numbers and complexity are being

detected by radioastronomy in the interstellar medium is of

fundamental importance to exobiology. This is because it

demonstrates clearly that the chemical evolution of organic

matter was not restricted to planets, but occurred widely in the

universe as an integral part of cosmic evolution.

Although observatories are important in understanding

exobiology questions, the basis from which understanding emerges

is primarily comprised of insights gained in ground-based and

orbiting laboratories. These are where both theoretical models

and models that simulate interstellar, stellar, and planetary

environments allow exobiologists to formulate hypotheses and

theories regarding the processes that influence the origin,

evolution and distribution of life in the universe. Improvements

in the fidelity of these models are largely derived from sample

analyses of meteorites and cosmic dust, and observational and

explorational data. In turn, information derived from models and

the requirement for "space truth" verification of model

information is often essential in defining the science content

and instrument requirements of various missions.

The next decade offers increasing opportunities for
significant advances in exobiology research. The suite of space

missions planned provides a unique opportunity to synthesize

observational, space exploration, in situ sample collection data,

and simulation experiments in order to investigate the relationship of meteorites, comets, interstellar dust clouds, and cosmic

dust collected in orbit in a complementary set of studies. The

Exobiology Program is actively planning a series _of low Earth

orbital investigations involving the Space Shuttle and Space

Station and is preparing for the Comet Rendezvous Asteroid Flyby

mission (scheduled for launch around 1990) and for the Titan

Probe and Mars Network missions (scheduled for launch around

1994), as well as a series of other solar system missions. One

of the critical activities planned for the Space Station involves

the development of a sophisticated "cosmic dust" collector and

source detector that will nondestructively capture particles of

cometary, asteroidal, and interstellar origin and provide

specific information regarding the source of the particles. On

the ground, it is planned for the NASA-sponsored Search for

Extraterrestrial Intelligence (SETI) to enter its operational

phase to detect evidence of the existence of extraterrestrial

civilizations by detecting signals that may be radiating from them.

Although other federal agencies also support specific research

tasks relevant to the origin and evolution of life, NASA's

Exobiology Program is unique in several respects: I) an emphasis

on the relationship between the origin of life and the properties

of the solar system; 2) a scope that ranges from biogenic

elements to the search for extraterrestrial life; 3) maintenance

of a strong in-house technical core around which an extensive

extramural program has been fashioned.

Effective study of questions in exobiology requires space

flight resources that are either available now or will be

available in the near future. The maximum benefit from these new

opportunities will be derived from the talents and creativity of

the scientific community as a whole and offers many opportunities

for fruitful collaboration on an international scale to continue

our exploration of life's relationship with the universe.
Second Symposium on Chemical Evolution and the Origin and

Evolution of Life, July 23-26, 1985, NASA Ames Research Center,

Moffett Field, California

Program

Speakers are indicated with an asterisk.

Tuesday, July 23, 1985

7:30 AM Visitor Reception Bldg. N-253

Registration, Foyer, Bldg. N-201

8:30 AM Welcome

Jack Boyd*

Associate Director

Ames Research Center

Alan Chambers*

Director of Space Research

Ames Research Center

8:45 AM "Future Directions in Exobiology"

Donald L. DeVincenzi*

(NASA Headquarters, Washington, D.C.)

9:15 AM "Exobiology Flight Experiment Opportunities"

Lynn Griffiths*

(MATSCO, Washington, D.C.)

Session I: Cosmic Evolution of Biogenic Compounds

Chairman: Theodore E. Bunch, NASA Ames Research Center

9:40 AM "Organic Chemistry of Murchison Meteorite:

Carbon Isotopic Fractionation"

G.U. Yuen* (Arizona State University,

Tempe), N.E. Blair, D.J. Des Marais,

J.R. Cronin, and S. Chang

PREYING _PAGE BLANK NOT F|LidF_

5
10:00 AM "Characterization of Biogenic Elements in

Interplanetary Dust Particles"

T.E. Bunch*

(NASA Ames Research Center)

Coffee

"Boundary Conditions for the Paleoenvironment:

Chemical and Physical Processes in Dense

Interstellar Clouds"

W.M. Irvine*, F.P. Schloerb, and L.M.

Ziurys

(University of Massachusetts, Amherst)

"Interstellar Isomers"

D. DeFrees* (Molecular Research

Institute, Palo Alto, CA), D. McLean,

and E. Herbst

"Photolysis Products of CO, NH_ and H20

and Their Significance to Reactions on

Interstellar Grains"

J.P. Ferris*

(Rensselaer Polytechnic Institute, Troy,

NY)

"Observational Exobiology"

J. Tarter*

(SETI Institute, University of

California, Berkeley and NASA Ames

Research Center)

12:00 noon Lunch

Session II: Prebiotie Evolution--Planetary

Chairman: Sherwood Chang, NASA Ames Research Center

1:00 PM "The Production of Trace Gases by

Photochemistry and Lightning in the Early

Atmosphere"

J.S. Levine* (NASA Langley Research

Center), G.M. Tennille, K.M. Towe, and

R.K. Khanna

10:20 AM

10:40 AM

11:00 AM

11:20 AM

11:40 AM
I :20 PM "The Organic Aerosols of Titan"

B.N. Khare, C. Sagan*, W.R. Thompson,

E.T. Arakawa, F. Suits, T.A. Callcott,

M.W. Williams, S. Shrader, H. Ogino,

T.O. Willingham, and B. Nagy

(Cornell University, Ithaca, NY)

I :40 PM "The D to H Ratio on Titan and the Planets:

Implications for Origin and Evolution of

Planetary Atmospheres"

J.P. Pinto* (Harvard University,

Cambridge, MA), J.I. Lunine, S.-J. Kim,

and Y°L. Yung

2:00 PM "Measurements of Physical Properties of Model

Titan Atmospheres"

T.W. Scattergood* (SUNY at Stony

Brook), S. Chang, C.P. McKay, B.J.

O'Hara, and G.C. Carle

Session III: Solar System Exploration

Chairman: Glenn C. Carle, NASA Ames Research Center

2:20 PM "Experimental Basis for a Titan Probe Organic

Analysis"

C.P. McKay* (NASA Ames Research

Center), T.W. Scattergood, W.J. Borucki,

J.F. Kasting, and S.L. Miller

2:40 PM "A Gas Chromatograph Experiment for a Titan

Entry Probe"

G.C. Carle* (NASA Ames Research

Center), D.R. Kojiro, B.J. O'Hara, J.R.

Valentin, V.R. Oberbeck, and T.W.

Scattergood

3:00 PM Coffee

3:20 PM "Molecular and Elemental Dust Analyzer (MEDA)

for the Comet Rendezvous Asteroid Flyby

Mission"

B.J. O'Hara* (NASA Ames Research

Center), G.C. Carle, and B.C. Clark
3:40 PM "Investigation of Porous Polymer Gas

Chromatographic Packings for Atmospheric

Analysis of Extraterrestrial Bodies"

4:00 PM

G.E. Pollock*

(NASA Ames Research Center)

"Miniature Metastable Ionization Detectors for

Exobiology Flight Experiments"

4:20 PM

4 : 40 PM

5 : O0 PM

F.H. Woeller*

(NASA Ames Research Center)

,,Multiplex Gas Chromatography: A Novel

Analytical Technique for Future Planetary

Studies"

J.R. Valentin* (NASA Ames Research

Center), G.C. Carle, and J.B. Phillips

"Ion Mobility Drift Spectrometry (IMDS) as a

Flight Analytical Instrument Technique"

D.R. Kojiro and G.C. Carle*

(NASA Ames Research Center)

"New Techniques for the Detection and Capture

of Micrometeoroids"

J.H. Wolfe* (San Jose State University),

T.E. Bunch, and G.C. Carle

5:20 PM Adjourn

Wednesday, July 24, 1985

Session IV:

Chairman:

8:30 AM

8:50 AM

Prebiotic Evolutlon--Moleeular

Robert D. MacElroy, NASA Ames Research Center

"Energy Yields in the Prebiotic Synthesis of

Hydrogen Cyanide and Formaldehyde"

R. Stribling and S.L. Miller*

(University of California, San Diego)

"Synthesis and Analysis in Studies of Chemical

Evolution"

C. Ponnamperuma, M.K. Hobish*, K.

Kobayashl, H. Lu-Lin, and N. Senaratne

(University of Maryland, College Park)

8
9:10 AM

9:30 AM

9:50 AM

10:10 AM

10:30 AM

I0:50 AM

11:10 AM

11:30 AM

11:50 AM

"Isotopic Characterisation of Prebiotic

Synthesis of Organic Material"

J.F. Kerridge* (University of

California, Los Angeles), S. Chang, R.

Shipp, and K. Wedeking

"Origin of Life and Iron-Rich Clays"

H.H. Hartman*

(Massachusetts Institute of Technology,

Cambridge)

Coffee

"Clay Energetics in Chemical Evolution"

L.M. Coyne*

(San Jose State University)

"Further Work on Sodium Montmorillonite as

Catalyst for the Polymerization of Activated

Amino Acids"

F.R. Eirich* (Polytechnic Institute of

New York) and M. Paecht-Horowitz

"Adsorption and Condensation of Amino Acids

and Nucleotides with Soluble Mineral Salts"

J. Orenberg* (San Francisco State

University) and N. Lahav

"Paleosols and the Chemical Evolution of the

Atmosphere"

H.D. Holland, E.A. Zbinden, and J.P.

Pinto*

(Harvard University, Cambridge, MA)

"Cooperation of Catalysts and Templates"

D.H. White* (University of Santa Clara),

A. Kanavarioti, C. Nibley, and J.W.

Macklin

Lunch
I :00 PM

I :20 PM

1:40 PM

2 :00 PM

2:20 PM

2:40 PM

3:00 PM

3 :20 PM

"Molecular Microenvironments: Solvent

Interactions with Nucleic Acid Bases and Ions"

R.D. MacElroy* (NASA Ames Research

Center) and A. Pohorille

"Intramolecular Interactions in Aminoacyl

Nucleotides: Implications Regarding the

Origin of Genetic Coding and Protein

Synthesis"

J.C. Lacey, Jr.*, D.W. Mullins, Jr.,

C.L. Watkins, and L.M. Hall

(University of Alabama in Birmingham)

"Molecular Replication"

L.E. Orgel*

(The Salk Institute for Biological

Studies, San Diego, CA)

"Stereoselective Aminoacylation of RNA"

D.A. Usher*, M.C. Needels, and T.

Brenner

(Cornell University, Ithaca, NY)

"Models of Glycolysis: Glyceraldehyde as a

Source of Energy and Monomers for Prebiotic

Condensation Reactions"

A.L. Weber*

(The Salk Institute for Biological

Studies, San Diego, CA)

"A Comparative Study of Prebiotic and Present

Day Translational Models"

R. Rein*, G. Raghunathan, J. McDonald,

M. Shibata, and S. Srinivasan

(Roswell Park Memorial Institute,

Buffalo, NY)

Coffee

"Protobiological Information, Bidirectional

Recognition, and Reverse Translation"

S.W. Fox*, T. Nakashima, A. Przybylski,

and G. Vaughan

(University of Miami, Coral Gables, FL)

10
3:40 PM "Photochemical Reactions of Various Model

Protocell Systems"

C.E. Folsome*

(University of Hawaii, Honolulu)

4:00 PM "The Principle of Cooperation and Life's

Origin and Evolution"

J. Oro*, G. Armangue, and A. Mar

(University of Houston)

4:20 PM "Base Pairing and Base Mis-pairing in Nucleic

Acids"

A.H.-J. Wang* and A. Rich

(Massachusetts Institute of Technology,

Cambridge)

4:40 PM Adjourn

Banquet

Location: Dinah's Shack, Palo Alto

7:00 PM Dinner

Guest Speaker: Stanley L. Miller (University

of California, San Diego)

Topic: "Historical Perspectives on Chemical

Evolution"

Thursday, July 25, 1985

Session V: Early Evolution of Life--Geochemical

Chairman: David J. Des Marais, NASA Ames Research Center

8:30 AM "Carbon Exchange between the Mantle and the

Crust, and Its Effect upon the Atmosphere:

Today Compared to Archean Time"

D.J. Des Marais*

(NASA Ames Research Center)

8:50 AM "Earth's Early Atmosphere as Seen from Carbon

and Nitrogen Isotopic Analysis of Archean

Sediments"

E.K. Gibson, Jr.* (NASA Johnson Space

Center), L.P. Carr, I. Gilmour, and C.T.

Pillinger

11
9:10 AM "Use of Laboratory Simulated Pyrolysis in

Tracing the History of Sedimentary Organic

Matter"

I.R. Kaplan*, E. Tannenbaum, and B.E.

Huizinga

(Institute of Geophysics and Planetary

Physics, University of California, Los

Angeles)

9:30 AM "Isotopic, Petrologic, and Biogeochemical

Investigations of Banded Iron-Formations"

J.M. Hayes* (Indiana University,

Bloomington), A.J. Kaufman, C. Klein,

S.A. Studley, M.E. Baur, and M.R. Walter

9:50 AM "The Lunar Nodal Tide and the Distance to the

Moon during the Precambrian Era"

J.C.G. Walker and K.J. Zahnle

(University of Michigan, Ann Arbor)

[This paper was not presented orally.]

10:10 AM Coffee

Session VI: Early Evolution of Life--Biological

Chairman: Lawrence I. Hochstein, NASA Ames Research Center

10:30 AM "Recent Progress in Precambrian Paleobiology"

J.W. Schopf*

(University of California, Los Angeles)

10:50 AM "Higher-order Structure of rRNA"

R.R. Gutell* and C.R. Woese

(University of Illinois, Urbana)

11:10 AM "rRNA Evolution and Procaryotic Phylogeny"

G.E. Fox*

(University of Houston)

11:30 AM "Investigations with Methanobacteria and with

Evolution of the Genetic Code"

T.H. Jukes*

(University of California, Berkeley)

11:50 AM Lunch

12
I :00 PM

I :20 PM

I :40 PM

2:00 PM

2:20 PM

2:40 PM

3:00 PM

3:20 PM

"Is the ATPase from Halobacterium

saccharovorum an Evolutionary Relic?

L.I. Hochstein* (NASA Ames Research

Center), W. Altekar, and H. Kristjansson

"Functional and Evolutionary Relationships

between Bacteriorhodopsin and Halorhodopsin in

the Archaebacterium, Halobacterium halobium"

J.K. Lanyi*

(University of California, Irvine)

"Thioredoxins in Evolutionarily Primitive

Organisms"

B.B. Buchanan*

(University of California, Berkeley)

"Biosynthetic Porphyrins and the Origin of

Photosynthesis"

D. Mauzerall* (Rockefeller University,

New York, NY), A. Ley, and J.A.

Mercer-Smith

"Oxygen and the Evolution of Metabolic

Pathways"

L.L. Jahnke*

(NASA Ames Research Center)

"Evolution of Thiol Protective Systems in

Prokaryotes"

R.C. Fahey* and G.L. Newton

(University of California, San Diego)

Coffee

"Microfossils in the Antarctic Cold Desert -

Possible Implications for Mars"

E.I. Friedmann* (Florida State

University, Tallahassee) and R.

Ocampo-Friedmann

13
3:40 PM

4 :O0 PM

4:20 PM

4:40 PM

7:30 PM

"Evolutionary Significance of Osmoregulatory

Mechanisms in Cyanobacteria"

J.H. Yopp*, K.A. Pavlicek, and M.H.

Sibley

(Southern Illinois University,

Carbondale)

"Microbial Contributions to the Precambrian

Earth"

L. Margulis, D. Bermudes*, and R. Obar

(Boston University)

"Organic 613C Values Vary Slightly with

Salinity in Microbial Mats at Guerrero Negro,

Baja Californi_Sur, Mexico: Implications for Stromatolite 6 JC Values

D.J. Des Marais*, E. Peterson, E. Kwong,

and H. Bui

(NASA Ames Research Center)

Dinner break

Evening Session

Discussion Session--Exobiology Flight

Experiment Opportunities

Friday, July 26, 1985

Session VII:

Chairman:

8:30 AM

8:50 AM

Tom Perry

(NASA Headquarters, Washington, D.C.)

Evolution of Advanced Life

John Billingham, NASA Ames Research Center

"The Fossil Record of Evolution:

Extinction"

D.M. Raup*

(University of Chicago)

"The Fossil Record of Evolution:

Diversification and Extinction"

J.J. Sepkoski, Jr.*

(University of Chicago)

Analysis of

Data on

14
9:10 AM

9:30 AM

9:50 AM

Session VIII:

Chairman:

10:10 AM

10:30 AM

10:50 AM

11:10 AM

11:30 AM

1:00 PM

"Geochemical Anomalies, Bolide Impacts and

Biological Extinctions on the Earth"

F. Asaro* (Lawrence Berkeley

Laboratory, University of California,

Berkeley), L.W. Alvarez, H.V. Michel,

and W. Alvarez

"Climatic Consequences of Very High CO2 Levels

in Earth's Early Atmosphere"

J.F. Kasting*

(NASA Ames Research Center)

Coffee

Search for Extraterrestrial Intelligence

Bernard M. Oliver, NASA Ames Research Center

"A Decade of SETI Observations"

R.S. Dixon*

(Ohio State University, Columbus)

"The Berkeley Serendip Project"

S. Bowyer, D. Werthimer*, J. Tarter, and

R. Buhse

(University of California, Berkeley)

"An Infrared Search for Extraterrestrial Laser

Signals"

A. Betz*

(University of California, Berkeley)

"Using the IRAS Data to Search in the Asteroid

Belt for any Potential Evidence of Galactic

Colonization"

M.D. Papagiannis*

(Boston University)

Lunch

"Overview of the NASA SETI Program"

B.M. Oliver*

(NASA Ames Research Center)

15
I :20 PM

1:40 PM

2:00 PM

2:20 PM

2:40 PM

"Stanford Hardware Development Program"

A. Peterson, I. Linscott* (Stanford

University and NASA Ames Research

Center), and J. Burr

"Goldstone Field Test Activities: Target

Search"

J. Tarter*

(University of California, Berkeley and

NASA Ames Research Center)

',Goldstone Field Test Activities: Sky Survey"

S. Gulkis and E.T. Olsen*

(NASA Jet Propulsion Laboratory)

"JPL's Role in the SETI Program"

M.J. Klein*

(NASA Jet Propulsion Laboratory)

Adjourn

16
Scientific Session Summaries

17
Q_airman:

Session I

Cosmic Evolution of Biogenic Compounds

Theodore E. Bunch, NASA Ames Research Center

The overall concept of this program is to understand the

history of biogenic elements (e.g., C, H, N, O, P, S) and their

compounds in the galaxy and the early solar system. The program

has three basic goals: I) trace the physical and chemical

pathways taken by the biogenic elements and their compounds from

their origins in stars to their incorporation in the preplanetary bodies; 2) determine the kinds of measurements that can

be made on the biogenic elements and compounds in the galaxy and

solar system in order to develop theories about the formation of

the solar system, prebiotic evolution, and the origin of life;

and 3) determine the ways in which the physical and chemical

properties of the biogenic elements and compounds may have

influenced the course of events during the formation of the solar

system and its component bodies.

Meteorite organic chemistry was the topic of the first

presentation by Yuen, Blair, Des Marais, Cronin, and Chang.

Organic matter in meteorites is basically a product of abiotic

processes and may be derived from solar nebula condensates that

have been altered by mechanical, thermal, and hydrothermal

processes in the meteorite parent body. Although the carbon

isotopic composition of individual organic compounds in

meteorites is largely unknown, Yuen et al. have determined carbon

isotopic ratios for hydrocarbons and monocarbox_ic ac_ in Murchison. For both classes of compounds, the _C to ratios

decreased with increasing carbon number in a parallel manner.

This and other isotopic data indicate a kinetically controlled

synthesis of heavy homologues from lighter ones.

Bunch discussed analyses of interplanetary dust particles.

Microprobe-SEM studies of dust particles indicated two groups:

I) particles similar to carbonaceous chondrites in terms of

mineral contents; and 2) unique particles that are enriched in

refractory elements, namely Ti and AI. Laser microprobe analyses

of particles yielded mass spectra of negative ionic species

suggesting the possible presence of poorly crystallized carbon

(carbon clusters, CH-), nitrogen-bearing organic matter (CN-,

HCN-, CN0-), phosphorus (PO 2 , PC3-), sulfur, and possibly water (OH-).

Irvine , Schloerb, and Ziurys presented observations bearing

on interstellar clouds. Research on the occurrence of organic

and other molecules in dense molecular clouds has yielded the

identification of four new molecules: CH_C_N, C_O, C_H, and

C3H 2 (the first interstellar molecular ri_g_to b_ identified).

18
Ongoing research also includes modeling chemical processes that

are important to the interstellar environment and the dynamics of

molecular cloud/new star evolution.

DeFrees, McLean, and Herbst used ab initio molecular orbital

theory, reaction rate theories, and molecular cloud models to

estimate the relative abundances of interstellar isomers. The

existence of the pair, HCN/HNC, has been confirmed; another

potential pair, HCO+/HOC +, is near confirmation as HCO + is a

known interstellar molecule and the tentative identification of

HOC + has been made. Methyl cyanide is also known and the

theoretical prediction of methyl isocyanide has prompted the

search for its existence in molecular clouds.

Ferris reported results of experiments intended to simulate

interstellar grains. Interstellar grains are thought to consist

of a silicate core and of inorganic and organic compounds (HpO,

CH 4, C02, CO, NH ) along with possible higher molecular weight

organic material 3 Photolysis of CO, NH_, and H^O mixtures have

yielded the reaction products lactic acid, glycolic acid, urea,

and eight other compounds whose formation mechanism may yield

clearer insight into interstellar abiotic organic chemistry.

Tarter summarized the proceedings of two Workshops on

Exobiology from Earth Orbit held during the past year that

focused on conducting research from some of the proposed

spacecraft and observational platforms. Clearly, observation

from beyond the Earth's atmosphere prevents optical distortion

and precludes absorption of UV and IR radiation. Many answers to

questions pertaining to the origin and evolution of biogenic

elements and compounds and the detection of terrestrial types of

planets can only be obtained from orbiting facilities. A final

report on the workshops will contain a list of observational

priorities that will ultimately be of great benefit to the

exobiology research community.

Chairman:

Session II

Prebiotie Evolution--Planetary

Sherwood Chang, NASA Ames Research Center

The epoch of Prebiotic Evolution begins with the formation of

planets and ends with the emergence of living systems.

Encompassed by this time frame are two kinds of processes:

planetary and molecular. Planetary processes occur on global or

local scales as a consequence of the development of planets.

These processes are responsible for setting the physical and

chemical conditions of the planets' various environments, wherein

the chemical evolution of organic matter may occur and living

19
systems may arise. Molecular processes may also occur on macroor microenvironmental scales, but they comprise the chemical

mechanisms by which the structures and functions that are

attributable to primitive life forms develop and assemble from

the materials of the prebiotic environment. The papers on

Prebiotic Evolution were given in Sessions II and IV (summarized

below) on the basis of this distinction.

The first paper in the session by Levine, Tennille, Towe, and

Khanna tackled the problem of assessing atmospheric sources and

rates of production for compounds that could have provided

protection to the earliest organisms against potentially lethal

solar ultraviolet radiation. Using an atmospheric model in which

the dominant species were molecular nitrogen, carbon dioxide, and

water, their computations suggested that atmospheric photochemistry could not have produced enough ozone or hydrogen

cyanide, nor allowed survival of sufficient volcanogenic sulfur

dioxide or hydrogen sulfide to have provided adequate shielding.

On the other hand, Levine and co-workers also reported

experimental and theoretical results indicating that nitric oxide

produced by lightning, then converted to nitric acid and "rained

out" of the atmosphere, could have helped attenuate UV radiation

in the upper levels of oceans.

A paper by Khare, Sagan, Thompson, Arakawa, Suits, Callcott,

Williams, Shrader, Ogino, Willingham, and Nagy reviewed their

studies of so-called tholin, a reddish organic solid formed by

continuous Tesla coil electric discharges through a simulated

Titan atmosphere. These experiments were intended to simulate

the irradiation of Titan's upper atmosphere by high energy

electrons. The real and imaginary parts of tholin's refractive

index were consistent with those deduced for the aerosols in

Titan's atmosphere, and similarities in the visible reflection

spectra of these materials were described. Molecular analysis of

tholins using pyrolysis GC-MS revealed a great variety of

hydrocarbons, nitriles, amines, and other nitrogen-bearing

species; acid hydrolysis produced amino acids. The work of K]_are

et al. reflects the viewpoint that the chemistry of Titan's

atmosphere constitutes a model for the chemistry of a prebiotic

Earth atmosphere dominated by nitrogen, methane, and hydrogen.

The paper by Pinto, Lunine, Kim, and Yung assessed the

possible causes for the ratio of deuterated to undeuterated

methane in Titan's atmosphere, which is higher by several times

than that observed in Jupiter and Saturn. Among the causes

investigated were formation of Titan, condensation of methane to

form tropospheric clouds, fractionation between atmospheric gas

and the putative hydrocarbon ocean or crustal clathrates, and

kinetic isotope effects in the photochemical reactions in the

atmosphere. Their calculations indicated two processes with

sufficiently large effects to account for the fractionation. The

first is grain-mediated equilibrium isotopic fractionation

2O
between molecular hydrogen and methane in the region of the

Saturnian nebula from which Titan accreted its methane. The

second is the kinetic isotope effect associated with atmospheric

photochemical reactions of the acetylenic free radical (C2H) ,

which destroys undeuterated methane faster than it does

deuterated methane. Both processes contributing equally could

account for the enrichment.

The final paper of the session by Scattergood, Chang, McKay,

O'Hara, and Carle was also related to Titan. This report

described simulations of lightning discharges--a hypothetical

mechanism for production of aerosols in the lower regions of

Titan's atmosphere--and the preliminary analysis of the resulting

products. When a simulated atmosphere was subjected to high

energy shocks created by a pulsed laser, a reddish-brown waxy

solid was produced. Pyrolysis GC analysis of this material

produced a variety of simple hydrocarbons, hydrogen cyanide, and

acetonitrile. The use of a pulsed laser to produce shocks

avoided the possibility of artifacts that might have arisen from

the use of metal electrodes and continuous discharges entailed in

other lightning simulations. Preliiinary evidence of benzene in

the laser-shocked gas was noted as possibly relevant to

understanding the observations of benzene on Jupiter.

Chairman:

Session Ill

Solar System Exploration

Glenn C. Carle, NASA Ames Research Center

The session on Solar System Exploration was devoted to two

major areas: i) reports of ongoing studies that will define

appropriate flight experiments for future planetary opportunities

where exobiology science objectives can be addressed; and

2) reports of current research studies into analytical concepts

and techniques which will lead to advanced flight instrumentation

for exobiology experiments. Experiment definition studies

focused on Titan in preparation for the Titan Cassini Probe and

on a short period comet, e.g., Kopff, Wild 2, Tempel 2, in

preparation for the Comet Rendezvous Asteroid Flyby Mission

(CRAF). As in the first Symposium, studies of advanced analytical concepts mainly treated advanced gas chromatographic techniques and components. However, ion mobility drift spectrometry

as applied to the special analytical needs of exobiology, e.g.,

organic molecules, and a novel concept for a micrometeoroid

collector and detector were presented for the first time.

McKay, Scattergood, Borucki, Kasting, and Miller reported

their work on laboratory and theoretical studies of the

atmosphere of Titan with respect to definition of the optimum

21
flight experiment for a Titan Cassini Probe. Titan is of

particular interest as, in many respects, it can be considered as

a terrestrial planet. Further, the unique nature of its

atmosphere, i.e., 5% CH_, makes it an analog of some models of

the early earth as well-as the site of very interesting and

pertinent organic chemistry. The authors' simulation studies of

lightning-induced chemical processes in model Titan atmosphere

gas mixtures produced evidence that existing models may not be

adequate to satisfactorily predict bounds on atmospheric

constitutents for design of a flight experiment. Their work

showed that larger amounts of ethane than predicted were present

which is in disagreement with the simple shock model. Continuing

studies are planned to reconcile theoretical models with

experimental results and define flight experimental requirements.

A paper on the development of a flight instrument concept for

a Titan entry probe was presented by Carle, Kojiro, O'Hara,

Valentin, Oberbeck, and Scattergood. Emphasis was placed on the

characterization of the entire atmosphere of Titan which requires

the detailed analysis of the various aerosols and hazes as well

as the gas phase. Results of preliminary studies on

electrostatic, filter, and wire impactor collectors were

presented showing that the electrostatic device provided the most

promise for efficient collection. Additionally, a concept for a

high altitude gas chromatograph sampling system was presented

which was demonstrated to be able to obtain representative gas

samples in model Titan atmospheres at a simulated altitude of

180 km (I mbar). Studies are planned to further develop the

collection concepts and to apply flight prototype pyrolysis-gas

chromatographic systems developed for a cometary dust analyzer to

the analysis of model atmosphere gases and aerosol components.

O'Hara, Carle, and Clark presented a paper on a molecular and

elemental dust analyzer that is to be proposed for the Cometary

Rendezvous Asteroid Flyby mission, which will seek to

characterize a comet nucleus in depth. Since comets are presumed

to be some of the most primitive bodies in the solar system and

may have played an important role in providing the biogenic

elements and their compounds to the early Earth, this mission is

of particular interest to the exobiology community. The flight

instrument concept presented was based on a pyrolysis-gas

chromatograph and an X-ray fluorescence spectrometer integrated

with a cometary dust collection and distribution system. The

instrument proposed would be able to collect and analyze as

little as a few micrograms of dust and ice grains ejected from

the comet as well as collect and analyze gases in the coma.

Molecular analysis would be accomplished with the pyrolysis-gas

chromatograph and polar molecules (e.g._ H20, NH_, HCOH), light

gases

determined

(e.g.,

to

N_,

_ I

CO,

ppm

Ar,

sensitivity

CO ), and

in

hydrocarbons

i gram of cometary

_ould be

dust .

Elemental Analysis would be accomplished with an x-ray

fluorescence spectrometer which would determine most elements

22
from Z = 6 to 92 which are present at > 10 ppm.

Pollock next presented results on studies of advanced gas

chromatographic columns and packing materials. These columns and

materials are being developed for future solar system exploration

missions where a gas chromatograph may be a candidate instrument,

e.g., the Comet Rendezvous Mission, a Titan Entry Probe. Such

directed development has been necessary due to the unavailability

of efficient, reliable, reproducible, and ultrastable column

packing materials, the heart of the chromatographic process, for

use in the demanding environment of a flight instrument. Studies

leading to an improved miniature light gas column for flight use

have been of particular importance due to physical resources

limitations aboard future spacecraft. A new porous polymer

packing made from divinylbenzene, styrene, and ethyleneglycol

dimethacrylate has now been developed. It is fully compatible

with the helium ionization detectors to be used in future flight

instruments, resulting in a 50% reduction in column size below

earlier flight columns, i.e., 8 m vs. 16 m. Similar studies on

miniature hydrocarbon-resolving columns have resulted in columns

as short as I m. Continuing work will include development of

improved polar compound-resolving columns as well as studies of

improved and ultrastable capillary column coatings.

Woeller then reported studies of the other important element

of the gas chromatograph: detectors. Again, past flight and

commercially available devices are inappropriate for future

missions mainly with respect to sensitivity and size. Woeller's

work has focused on new configurations of the helium ionization

detector, generically a metastab_ ionization detector (MID).

These MID's are sensitive to 10--- moles/sec and when coupled

with a special circuit that modulates the applied voltage as a

function of signal current have a dynamic range in excess of 7

orders of magnitude. Detectors developed by Woeller are

currently being incorporated in a flight instrument for the

monitoring of astronaut denitrogenation prior to EVA (Extra

Vehicular Activity) and their use is planned for the CRAF

mission. Recent work has produced a new MID which is an order of

magnitude smaller in active volume than those reported by Woeller

earlier. This detector is directly and fully compatible with

capillary column applications and produces sensitivities of a few

ppb. Woeller also reported on studies of the physical and

chemical principles of the MID and pointed out the necessity of

maintaining a contaminant-free system. He went on to show that

contamination in the gas stream, either from carrier or column

bleed, was an increasingly important consideration as carrier

flow and detector volume was reduced.

Valentin, Carle, and Phillips reported on recent advances in

the technique of multiplex gas chromatography--a novel

mathematical approach where samples are introduced into the

chromatographic stream pseudorandomly without regard to elution

23
of preceding components. The technique provides a large increase

in sample throughput thus improving either sensitivity or

analysis rate. Additionally, the technique opens up new

opportunities for novel sample introduction schemes. Until

recently the technique has been rather a laboratory curiosity,

because it had never been applied to a practical analytical

problem. Valentin reported here of the first practical

application of the technique where he analyzes methane in the

atmosphere with ambient air serving as both the carrier gas

stream and sample. The new technique uses a heated catalytic

modulator to selectively oxidize hydrocarbons in the air carrier

gas. On command of a computer, the modulator is cooled producing

a pulse (or injection) of hydrocarbon containing carrier gas.

The remaining chromatographic process is as in the conventional

except data are collected by the same computer that controls the

modulation pulses. Since as many as 220 visually uninterpretable

chromatograms are processed in an hour, this computer also

mathematically obtains the final chromatogram. Data presented by

Valentin not only demonstrated the utility of the technique for

future flight missions to study planetary atmospheres, it

revealed some previously unobserved variations in ambient methane

concentrations that are currently under study. Future work will

also include further studies of catalytic modulators and

specialized detectors for application to planetary atmospheres.

Kojiro and Carle reported on ion mobility drift spectrometry,

another advanced analytical technique that could be applied to

Exobiology's requirements in solar system exploration. An ion

mobility drift spectrometer is an ion/molecule reactor coupled

with an ion drift spectrometer. Sample molecules enter the

reactor where they are ionized forming product ions that are

structurally representative of the original sample molecule. The

product ions are then extracted from this region into the

spectrometer. These ions are separated in an electric field and

finally collected providing a signal. The time required for the

ions to drift through the field is directly related to their

structure and molecular weight. This instrument concept is

particularly attractive as a tool for solar system exploration as

it is easily interfaced with a gas chromatograph, i.e., it

operates at the same pressures as the vent of a gas chromatograph

and uses a reasonably high throughput of gas. Kojiro reported on

the prospects of fitting such a device to a flight gas

chromatograph. He found that the commercial device could be

operated with consumables appropriate for a flight instrument and

could be used with the miniature columns currently available. He

also showed that the device could be used to identify the

molecular species important to Exobiology. Plans for future work

include miniaturization studies and studies of alternative ion

reactions.

Wolfe, Bunch, and Carle presented advanced instrumentation

concepts for a micrometeoroid detector and collector that might

24
be flown on the Space Station. It was stated that in order to

understand the origin and distribution of the biogenic elements

and their compounds, it will be necessary to study many classes

of extraterrestrial objects. Of major importance are the

primitive bodies which may shower the earth with fragments in the

form of cometary dust. Collection of these particles in a

pristine environment as found in space would provide samples for

study in Earth-based laboratories. Additionally, detection of

these particles and characterization of their paths and energies

would aid in verifying their origin. To this end, Wolfe et al.

described a particle detector that could effectively "listen" for

collisions with a large structure in space using acoustic

detectors. The detector structure would, over long periods, be

pointed in all directions in space and incoming particle vectors

(source), fluence, as well as momentum information, could be

accurately determined for the cosmic dust particles. The

collection concept advanced was based on electrostatic

deceleration of the same particles. Using a computer-controlled,

staged decelerator, incoming particles would be detected and,

based on their mass and speed, would be sequentially slowed down

and brought to rest on a sample pan. The pan would be removed

and replaced occasionally and collected samples would be returned

to earth for analysis.

Chairman:

Session IV

Prebiotie Evolution--Molecular

Robert D. MacElroy, NASA Ames Research Center

The research areas in Prebiotic Evolution covered in this

session included the following: I) formation of small organic

materials under laboratory conditions simulating the primitive

Earth; 2) synthesis of organic structures on surfaces, including

meteorites, clays and mineral salts; 3) investigation of model

systems of catalysis, self-replication and translation; 4) exploration of the environments and molecular structures that may

have been important in the generation of prebiotic functions;

5) possibly useful prebiotic energy sources; and 6) evidence for

the state of the early biotic environment.

Stribling and Miller reported on an evaluation of the yield of

organics (HCN and H2CO) of spark discharge experiments as a

function of energy input. The amount of product resulting from

the reactions was determined after increasing time intervals and

extrapolated back to zero time. Yields of the order of 0.7 to 6

x 10 -8 moles/cal were observed. The results suggest that

products were destroyed during the course of the reaction. The

data provide a better evaluation of productivity of various kinds

of organic syntheses in the prebiotic environment than has been

25
available before. The experiments were extended to include other

energy input forms, as well as consideration of subsequent

reactions of the initial products.

The possible prebiotic formation of organic matter was also

reported by Folsome. He had previously reported that organic

microstructures formed in spark discharge experiments containing

N_, CO, and H_ could catalyze photoreduction of carbonate to

o_ganic carbo_. Current studies showed the formation of organic

structures after prolonged exposure of N^, carbonate, and water

to long wavelength UV, extending his earlier observations.

Folsome concluded that such phase-bounded systems can serve

effectively to form reduced organics from oxidized carbon in a UV

energy flux.

Fox, Nakashima, Przybylski, and Vaughan reported on studies of

reverse translation in thermal proteinoids. One object of study

was the catalysis of 5'-phosphorimidazolides by thermal

polypeptides. It was observed that a deceleration of the

reaction is caused by thermal polylysine polymers in the

reaction, whereas they accelerate the formation of nucleoside

triphosphates. Included in the presentation was a discussion of

the appearance of electrical signals apparently generated by

proteinoid microspheres, which is interpreted as support for the

concept that such entities contain information.

Evidence for prebiotic formation of organics was addressed by

Kerridge, Chang, Shipp and Wedeking. The occurrence of organic

kerogen-like materials in meteorites has stimulated interest in

the synthesis of such materials in laboratory simulations of

possible production mechanisms. Methods for analyzing them and

comparing them to meteoritic organics have been devised.

Decomposition of the material by heat, in the presence and

absence of 02, followed by isotopic analysis of the products

released as a function of temperature was used as a method of

characterization. While carbon fractions of laboratory-produced

materials were found to grossly resemble meteoritic materials,

the deuterium-hydrogen release patterns were very different. It

was suggested that the discrepancies in release patterns may be

evidence that meteoritic materials contained several compounds

that were formed at different times and from starting materials

of differing isotopic compositions.

Another correlation between meteoritic organic syntheses and

those that may have occurred on the primitive Earth was suggested

by Hartman. Iron-rich clays are found on meteorites, and also

are implicated in his hypothesis that they played a significant

role in the synthesis of organics on the primitive Earth.

Hartman, Sweeney and Kroll have exploredpthe radiolysis of

ammonium carbonate in the presence of Fe-+ and have found that

glycine is formed 3-4 times faster than in its absence.

26
Coyne addressed the role of clays in the origin of terrestrial

life. She pointed out that clays have been implicated in the

origin of terrestrial life as: a) substrates on which the organic

precursors of cellular life were synthesized and assembled and b)

as inorganic prototypic life forms that served as templates for

cellular life. The capacity to store and transfer chemically

significant quantities of electronic energy would have been

useful for a and is prerequisite to b. Coyne and her colleagues

have predicted and shown experimentally that clays can store and

transfer electronic energy. They have also predicted and are

investigating the extent to which the energy storage capacity is

of sufficient magnitude to impact surface chemistry in or on

clays. Previously they investigated the correlation between

luminescence, induced by wetting/drying with water and

substituted hydrazines, and the degree of interlayer hydration in

two series of hydrated kaolins.

Clays as catalysts for polymerization of amino acids were

discussed by Eirich and Paecht-Horowitz. They reported the

synthesis of a discrete set of condensed poly-amino acids, and

have explored stereoselective synthesis on clays in the presence

of copper ion. They also reported the production of a

predominance of L-alanine peptides when Cu-L-proline was first

adsorbed to the clay and when a D,L-alanine adenylate was used as

a starting material. They concluded by reporting that studies of

preferential adsorption of nucleotides to clay surfaces indicate

that preadsorption of adenine (but not adenylic acid) to clay

surfaces causes an adsorption of UMP that is proportional to the

amount of adenine adsorbed.

Surfaces, not of clays, but of soluble mineral salts, have

been studied by Orenberg and Lahav as sites of biopolymer

synthesis. They suggest that the process of synthesis is cyclic,

as would occur during the wetting/drying cycles of a small pond.

A plausible and most primitive mechanism of information transfer

operating in a fluctuating environment may include i) adsorption

of biomolecules onto mineral surfaces, acting as an adsorbed

template; 2) specific adsorption of biomonomers onto the

template; 3) condensation of adsorbed monomers; and 4) desorption

of the elongated molecule. This mechanism is being tested with a

variety of soluble mineral salts, for example, CaS04, SrS04,

FeCl_, Fe(OH)_, and ZnSO_, with several monomerlc specles

(gly_ine, 5'-KMP, 5'-GMP. and 5'-CMP). The adsorbed templates

being tested are poly-A, poly-G, poly-C and poly-U.

Orgel reported further work on the template-directed synthesis

of polynucleotides from activated nucleotides. The results

reported indicate that i) good yields and correspondences are

obtained provided that the template is rich in C; 2) templates

can be as short as 5 monomers long and show efficient activity;

3) synthesis proceeds in the 5'-->3' direction; 4) fidelity is

high; and 5) the incorporation reaction is enantiomerically

27
specific.

White, Kanavarioti, Nibley, and Macklin reported on recent

progress in the investigation of possible catalysts,

protoenzymes and templates in the prebiotic environment. They

reported that with a model primitive translation system,

consisting of dried clays in the presence of various ribo- and

deoxyribo-polynucleotides, an increase in the formation of

polypeptides was found with ribo- but not with

deoxyribo-polynucleotides. They have also, in collaboration with

Orgel, recently initiated investigations into the possible

function of small peptides in the polymerization of

oligonucleotides.

MacElroy and Pohorille reported recent data on the interaction

of water molecules with putative prebiological molecules, such as

nucleic acid bases and amino acids. The computer simulation

studies were conducted to better understand the role of solvent

interactions as an organizing influence on simple prebiotic

molecules. One result of the studies demonstrated that the

energy of interaction between water molecules in the presence of

nucleic acid bases can be quantified, and provides an explanation

for the stacking, rather than hydrogen bonded pairing of bases,

that is observed in solutions of these solutes. A discussion

involving the extrapolation of the results and concepts to

include the role of water in determining the structure, and thus

the function, of larger molecules (peptides, nucleic acids) was

also presented.

The origin of translation mechanisms was the object of a

presentation by Lacey, Mullins, Watkins, and Hall. The

correlation of physical characteristics of codons and anticodons

with amino acid assignments found in the genetic code was

discussed. Studies of activated amino acids were reported,

specifically including NMRstudies of adenylates of amino acids.

The data indicate that such adenylates exhibit interactions

between the side chains and the adenine ring, and that the

strongest interactions occur between L amino acid forms and the

ring.

Ponnamperuma, Hobish, Kobayashi, Lu-Lin, and Senaratne focused

their presentation on the importance of analysis of materials,

such as meteorites that contain abiotic organic materials, and

the fact that similar materials can be synthesized abiotically in

the laboratory. Further, they called attention to their recent

studies of NMRdata that demonstrate that definite biased interactions exist between amino acids and their anticodonic nucleotide sequences. Specifically, if those methyl esters of amino

acids with homopolymeric nucleotide codes, such as gly, pro, phe

and lys, are analyzed by NMR in solution with mononucleotides,

their interactions show definite preferences of interaction. The

preference increases are maintained and the binding constants are

28
increased when examined in the presence of dinucleotides.

Usher and Needles reported on the continuation of studies of

template-directed synthesis, and specifically on stereoselective

aminoacylation of RNA. The 2' hydroxyl groups of RNA can by

aminoacylated, starting from an amino acyl-imidazolide, and the

process selects the chirality of the amino acid. The chiral

selectivity has been found to depend on the presence of an amino

protective group, and is influenced by the hydrophobicity of the

amino acid side chain. The studies have been conducted using ApA

as the model RNA acceptor and involve the use of NMRas a method

of examining chiral selectivity.

Energy sources for prebiotic and early biotic forms was the

topic of the presentation made by Weber. The hypothesis is that

nonenzymatic reactions that generate ATP were possible in the

prebiotic environment, and that certain components of the present

day glycolytic pathway are likely candidates for consideration.

Of particular interest is the oxidation of glyceraldehyde3'-phosphate to produce a thioester, which in turn can drive the

formation of the phosphoanhydride bond of pyro- and polyphosphate. The presentation also suggested that polyglyceric

acid can contain information in the form of sequences of D and L

glyceric acid residues, that the polymer might act as a catalyst

by virtue of the acid base behavior of its hydroxyl groups.

The three dimensional structure of nucleic acids and their

role in the generation of the genetic code was the topic of a

presentation by Rein, Raghunathan, McDonald, Shibata, and

Srinivasan. Folding of polynucleotides was studied using

computer graphics methods, and simulations of possible mechanisms

of decoding between nucleic acids and protein (translation) were

investigated. Possible prebiotic coding schemes were compared to

present day translation mechanisms. The central issues that

emerged not only involved identification of possible reaction

mechanisms in present day systems, but also identified

geometrical difficulties associated with some prebiotic

translation systems that have been proposed.

Wang and Rich used very high resolution x-ray crystallographic

data of nucleic acid structures to illustrate the possible role

of structure in the functions that the molecules perform. Of

particular interest was the structure of Z-DNA and the

consequence that such a structure has on the characteristics of

the molecule as a whole. In particular, the types of

base-pairing were discussed, raising the issue as to whether

base-pairing other than the standard Watson-Crick, which is now

most commonly observed in RNA molecules, m_ght have been the

structure of importance in the prebiotic evolution of molecules.

The conjecture _s supported by the relative ease with which

crystal lattices of Hoogstein base pairs are generated.

29
Correlations between atmospheric composition and evolution

were discussed in the presentation by Holland, Zbinden and Pinto.

Paleosols found in Australian and South African rocks ranging

between I and 2.9 billion years in age (bya) were examined to

determine the oxidation state of the atmosphere. The method is

based upon the oxidation state of iron in the rock, which is due

to the initial amount of reductant (ferrous iron) in the rock,

and the amount of oxidant and CO^ in the rainfall at the time the

paleosol was formed. They conclude that the oxidation state of

the atmosphere 2.9 bya was lower than at 2.4 bya.

In addition, presentations were made by staff members of the

laboratories of J. Oro and C. Ponnamperuma.

Session V

Early Evolution of Life--Geochemical

Chairman: David J. Des Marais, NASA Ames Research Center

The traditional theme of geochemical research in the Planetary

Biology Program has been to examine specifically the morphology

of microfossils and the chemistry of organic matter in ancient

rocks. Some of the papers in this session addressed this

traditional theme. In addition, other papers attempted to define

various aspects of the primitive environment in which early life

flourished. This broader approach toward studying the history of

the biosphere underscores the recognition that numerous

interactions between the Earth and the biosphere have exerted a

critical influence upon biological evolution.

The presentation by Des Marais noted that, over the great time

interval of the Precambrian, interactions between the Earth's

mantle and crust very likely influenced the changes in the

surface environment. This paper estimated the rate at which

carbon is exchanged between the mantle and the crust. Because

the upper mantle has cooled by at least 300°C during Earth

history, and because the present exchange rate of carbon between

mantle and crust is non-negligible (between Ixi012 and 8xi012

moles C yr_), the crustal carbon inventory may have been greater

on the Archean earth than it is today. This circumstance favored

an Archean atmospheric carbon dioxide concentration which was

higher, perhaps by a factor of 100 or more, than the present

level.

Gibson, Carr, Gilmour, and Pillinger presented results of

stepwise combustions of Archean sediments, and sought to identify

the origins of the carbon and nitrogen fractions which were

evolved at the various temperatures. They proposed that carbon

and nitroge_ from the_sediments' organic matter is released

between 300 C and 700°C, and that carbon and nitrogen components

30
from the ancient atmosphere are released above 900°C. Their

presented data suggested that the carbon and nitrogen isotopic

compositions of atmospheric carbon dioxide and nitrogen have been

remarkably constant over geologic time. Some in the audience

questioned the validity of the assumption that the carbon and

nitrogen released above 900°C did not include a significant

contribution from residual sedimentary organic matter. Future

work may clarify this issue.

Kaplan, Tannenbaum, and Huizinga presented results from

laboratory experiments in which organic matter was heated in the

presence of various geochemically important minerals. This

organic matter decomposes at significantly lower rates in calcite

and chert matrices than in the presence of clay. Water appears

to inhibit the breakdown process. Kaplan and coworkers have also

tested montmorillonite and illite clays as well as a variety of

kerogen types. Such work allows a more precise interpretation to

be made regarding the state of preservation of ancient organic

matter.

Hayes, Kaufman, Klein, Studley, Baur, and Walter are

conducting a multidisciplinary investigation of banded iron

formations which are iron-rich Precambrian sediments whose

precipitation is attributed to biological oxidation processes.

Prior to the development of a highly oxygenated atmosphere,

dissolved iron was an important seawater constituent. Hayes and

co-workers have identified stable carbon and nitrogen isotopic

heterogeneities in iron formation carbonates. Such patterns are

not metamorphic in origin, and they likely reflect biogeochemical

processes that occurred shortly after the sediments were

deposited. These and other observations are helping to elucidate

the processes associated with the deposition and alteration of

these significant rock formations.

Although the paper by Walker and Zahnle was not presented at

the meeting, its importance merits summary here. The authors

proposed that the 23.3-year periodicity observed in Hamersley

banded iron formation laminations reflects the climatic influence

of the lunar nodal tide. If such is the case, then detailed

measurements of iron formation laminae ultimately will help to

define the evolution of the Earth-Moon orbital system. Such work

promises to eludicate, among other things, the length of Earth

days and the distance between the Earth and the Moon during

Archean and early Proterozoic time.

Chairman:

Session VI

Early Evolution of Life--Biological

Lawrence I. Hochstein, NASA Ames Research Center

31
This session covered an extremely divergent range of topics.

The unifying theme was the notion that contemporary organisms

contain within them information which allows for a retrospective

look at the evolution of early life.

The session was introduced by Schopf who reviewed several

issues associated with the Precambrian environment. Further

understanding of this period requires more information

concerning: day length, temperature, atmospheric composition, and

ultraviolet flux. In addition, Schopf suggested several unsolved

problems related to that era: a) why is there no evidence of the

primordial soup in sediments; b) was early photosynthesis

oxygenic; c) are there markers that relate morphological and

biochemical evolution; d) to what extent was lateral gene

transfer an important process in the early evolution of life; and

e) how did biomass vary over time?

There followed a series of papers dealing with rRNA. Gutell

and Woese reported on the possibility of using secondary

structures of rRNA as phylogenetic probes. The 16s rRNAs were

found to have a common secondary structure within which occurred

highly conserved nucleotide regions. Fox described further

structural studies with 5s rRNA. The results were consistent

with the phylogenies obtained using 16s rRNA sequences. He also

found that among the gram negative bacteria, phylogenies obtained

from rRNA sequences, DNA hybridization, and cytochrome c

sequences are in good agreement. Jukes, addressing the issue as

to whether the code was a frozen accident or the result of

stochastic processes, concluded it was probably the latter. In

addition he reported on codon assignments in mitochondrial DNA

and in Mycoplasma which violated the dogma •of the universal code.

Two papers reported on bioenergetic processes found in the

halobacteria. Hochstein, Altekar, and Kristjansson described an

ATPase from Halobacterium saccharovorum. The subunit composition

of this enzyme is clearly unlike that of an FoFI ATPase or other

ion-translocating ATPase. Whether this represents a functional

or structural precursor of energy-transducing ATPase is not

clear. Lanyi discussed the evolutionary relationship between two

retinal-containing molecules: bacteriorhodopsin, which functions

as a llght-dependent proton pump, and halorhodopsin, which acts

as a chloride pump. Structural and functional studies revealed

that the opsins must be different and that few if any sequence

homologies exist.

Buchanan reported on the distribution and properties of

several thioredoxins. The thioredoxin system from Clostridlum

pasteurianum behaves like the thioredoxin from photosynthetic

organisms in that it was reduced by ferredoxin. Prior to this

observation it was thought that ferredoxin acted as the reductant

in oxygenic photosynthetic plants and NADPH was the reductant in

other organisms. The ferredoxin/thioredoxin system acts to

J

32
regulate CO2 assimilation via the reductive pentose phosphate

cycle in organisms that carry out oxygenic photosynthesis.

Further evidence for this notion was the occurrence of such

regulation in a cyanobacterium (carrying out oxygenic

photosynthesis) but not in Chromatium (which carries out

non-oxygenic photosynthesis). The possibility that this

biochemical process left a permanent record (see Schopf's points

b and c) suggests the possibility of dating the appearance of

anoxygenic and oxygenic photosynthesis. Mauzerall, Ley and

Mercer-Smith are studying the origins of photochemical systems

and reported on the efficacy of model chemical systems using

cobalt complexes and porphyrin precursors as catalysts for the

photooxidation of organic molecules.

Fahey and Newton found that the nature of thiol compounds in

various organisms appeared to be associated with the oxygen

relationship of the organism (i.e., aerobic, facultative, or

anaerobic). In an intriguing observation, Entamoeba histolytica

(which does not possess mitochondria) lacks thiols associated

with organisms thought to be likely endosymbiotic candidates.

These observations suggest that the nature of intracellular

thiols may be useful probes for understanding the role of

endosymbiosis in the evolution of life. Yopp, Pavlicek, and

Sibley reported on the relationship of osmoregulators to the

physiology of a variety of cyanobacteria. The pattern which

emerged was that fresh water and marine cyanobacteria used

non-reducing carbohydrates whereas the extremely halophilic

organisms employed betaine as the osmoregulator. In further

studies relating the mode of energy-transduction to the nature of

the osmoregulator, organisms which were photoautotrophic

accumulated trehalose whereas those which were photoheterotrophic

used sucrose.

Jahnke found that the synthesis of sterols and unsaturated

fatty acids was enhanced in a methanotroph when grown at low

oxygen concentrations. The occurrence of sterol synthesis in a

procaryote may permit studying the evolution of oxygen-requiring

pathways found in eukaryotic cells in the more primitive

procaryotes.

The last set of papers dealt with the properties of organisms

found in environments that may serve as either putative Martian

environments or Precambrian ones. Friedmann and Friedmann

described and provided visual examples of the endolithic

communities found in Antarctic rocks. Margulis, Bermudes, and

Obar spoke of the organisms found in mat communities. Des

Marais, Peterson, Kwong, and Bui reported on carbon isotope

fractionation in mats from salt ponds. These studies were

carried out to determine if salinity could account for the

differences in the carbon isotope ratios in stromatolites and

contemporary mats. The results suggested that salinity, per se,

would not account for the observed differences.

33
Chairman:

Session Vll

Evolution of Advanced Life

John Billingham, NASA Ames Research Center

One of the newer elements of the NASA Planetary Biology

Program deals with the evolution of multicellular life over the

last billion years. The major thrust of the research is an

examination of the way in which extraterrestrial events

influenced the evolution of advanced life on Earth. A minor

objective is to begin the difficult task of examining important

basic questions about the existence of advanced forms of

extraterrestrial life. Both questions were discussed extensively

in a series of Science Workshops held in 1981 and 1982 at the

Ames Research Center and attended by leading scientists from the

fields of evolutionary biology, paleontology, astronomy, and the

planetary sciences. The Chairman was David Raup from the

University of Chicago. A report from this workshop is now

available (Milne, D., D. Raup, J. Billingham, K. Niklas, and K.

Padian. The Evolution of Complex and Hi_her Organisms. NASA

SP-478. Washington, D.C.: NASA, 1985) and may be obtained from

my office at Ames Research Center.

During the July 1985 symposium a number of speakers dealt with

different aspects of the evolution of advanced life. Raup

discussed the asteroid impact theory of mass extinctions as well

as the new hypothesis, proposed by Raup and Sepkoski, that mass

extinction may be periodic over the last 260 million years. He

discussed the possible astronomical causes that are now being

examined. Sepkoski followed with a paper discussing his detailed

analysis of the fossil record down to the genera level. He found

that periodicity breaks down as one goes back to the Cambrian,

that background extinctions decrease markedly with time, that

extinction is indiscriminate in the oceanic environment, and that

long established taxa are more likely to disappear during mass

extinction events than during the normal background intervals.

Asaro, Alvarez, Michel, and Alvarez described the latest

Berkeley team results on geochemical anomalies at extinction

boundaries. He reported that high iridium concentrations had

been found at the Eocene-Oligocene boundary in eight to nine

sites around the world, suggesting that this event might also

have been caused by an asteroid impact.

Kasting of the Ames Space Science Division discussed the

importance of COn in the early atmosphere of the Earth and the

current theory t_at the CO 2 pressure at that time may have been

as much as 20 bars. Model calculations indicate that a runaway

greenhouse would not have occurred because of reduced solar

luminosity, an increase in planetary albedo because of the CO 2,

34
and the stabilizing effects of moist convection.

Session VIII

Search for Extraterrestrial Intelligence

Chairman: Bernard M. Oliver, NASA Ames Research Center

This session presented reports on various Extraterrestrial

Intelligence (ETI) searches that have been conducted over the

past decade, are currently underway, or are proposed for the

decade ahead.

The first paper by Dixon described the full-time dedicated sky

survey that has been in progress at Ohio State for the past 12

years. The search concentrates on a 500 khz band centered on the

hydrogen line at 21 cm. The scan in right ascension is provided

by the Earth's rotation with jumps in declination provided by

adjusting the telescope reflector angle periodically. Fifty

channels each 10 kHz wide are monitored automatically. The

(quantized _) intensity and channel number of signals exceeding

threshold are printed out for later study. Two populations of

signals have been detected. The first is a small number of

signals lasting for over a minute. The second is a large number

of signals lasting less than 10 seconds and whose locations

appear anticorrelated with the galactic plane. The signals do

not recur and their origin is unknown at present.

The second paper, presented by Bowyer, Wertheimer, Tarter, and

Buhse described the U.C. Berkeley SERENDIP project, which looks

for ETI signals on radio telescopes while they are engaged in

radio astronomy. New data processing equipment will extend the

sensitivity and frequency coverage of this system. A fast

Fourier transform spectrum analyzer provides 65,536 bins 2 Hz in

width for a frequency coverage of 131 kHz. After searching for

and recording significant peaks in a 100 kHz band the

programmable synthesizer jumps to the next 100 kHz band. When

the whole IF band has been covered, the scanning repeats. A

trial run is planned at the Hat Creek Observatory in late summer.

Betz next described his proposed ETI search in the 10 um

infrared portion of the spectrum. The search postulates powerful

CO_ laser sources. These are to be detected using a laser

he_erodyne receiver. The IF processing will provide 1000

channels each I MHz wide. Using a ground-based IR telescope,

several hundred selected stars will be surveyed.

Papagiannis presented his rationale for searching the

asteroids of our own solar system for evidence of ETI activity.

Such activity might be revealed by excess infrared emission

detectable by the IRAS satellite. The IRAS catalogue is expected

35
to be ready at the end of 1985 and will contain some 10,000

objects. Papagiannis proposes to search this catalogue for

objects having anomalous IR spectra, and then to study these

objects using radio and optical telescopes.

The remaining five papers were all concerned with the NASA

SETI program. Oliver, Chief of the SETI Program Office,

presented an overview of the program, which features a two mode

search strategy. An all sky survey will cover the frequency

range of I to 10 GHz using an instantaneous bandwidth of 250 MHz

and a resolution of about 30 Hz. Simultaneously, a targeted

search will examine the 800 closest solar type stars over the I

to 3 GHz frequency range, using an instantaneous bandwidth of 10

MHz and a resolution of I Hz. In the present R and D phase of

the program, signal processing hardware and software is being

designed and tested. Algorithms are being developed that for the

first time will permit the sensitive detection of not only steady

CW (narrowband continuously present signals) but also both CW and

pulsed signals that drift in frequency due to doppler effect. A

new start is planned for FY 88, with observations beginning in

1990. This program will test the hypothesis that ETI signals can

be detected with presently existing radio astronomy or Deep Space

Net antennas. If the hypothesis is false, the future of SETI

will require much larger, dedicated receiving antennas.

Peterson, Linscott, and Burr reported on the Multichannel

Spectrum Analyzer (MCSA) and pattern detector needed for data

processing in the targeted search. These devices, currently

being refined at Stanford, are highl_ocOncurrent processors with

computation rates on the order of 10 operations per second. A

prototype of the MCSA is operational at Goldstone, and has

detected Pioneer 10, now outside the solar system. Economical

realization of the full scale signal processing equipment

requires the use of very large scale integration. This is

currently being designed.

Tarter described a number of questions which hopefully can be

resolved by the current and planned field tests at Goldstone and

possibly at Arecibo. Of particular concern is the RFI (strong

man-made interfering signals) environment and how the system can

best identify signals as not ETI but RFI. Also of interest are

the time statistics of receiver noise particularly in the low

probability tails of the distribution. These may well depart

significantly from the assumed Gaussian form.

Gulkis and Olsen described some details of the sky survey

program including the proposed scanning pattern and the detection

algorithms. The RFI surveillance system built by JPL for use at

SETI observing sites was also discussed.

Finally Klein spoke about JPL's role in the NASA SETI program.

This is primarily in the planning and execution of the sky survey

36
but includes the design of feeds and receivers for both the sky

survey and the targeted search. A SETI implementation plan for

the use of the NASA Deep Space Network facilities for the sky

survey is under preparation.

37
o.

Session I

Cosmic Evolution of Biogenic Compounds

PW_D_ PAGE LANK NOT

39
r486: 6845

Organic Chemistry of Murchison Meteorite:

Carbon Isotopic Fractionation

George U. Yuen, I* Neal E. Blair, 2 David J. DesMarais, 3

John R. Cronin I and Sherwood Chang 3

i Arizona State University, Tempe, Arizona

2 North Carolina State University, Raleigh, North Carolina

3 Ames Research Center, Moffett Field, California

Carbonaceous meteorites remain the only source of isolable organic

compounds of extraterrestrial origin, even though radio astronomy has

provided evidence for the existence of more than 50 compounds in interstellar space, of which the overwhelming majority are organic. Most

investigators now agree that the organic matter in the meteorites are

products of abiotic processes. Most likely, these materials are derived

from solar nebula condensates that have been altered to varying degrees by

mechanical, thermal, and hydrothermal processes in the meteorite parent

body. These processes and the locale in which they occurred are essential

to the understanding of the organic chemistry secreted in these specimens.

Carbon isotopic fractionation of these organic compounds may reveal

information about these processes as they often leave in their products a

recognizable isotopic signature.

The carbon isotopic composition of individual organic compounds of

meteoritic origin remains unknown, as most reported carbon isotopic ratios

are for bulk carbon or solvent extractable fractions. Recently, we managed

to determine the carbon isotopic ratios for individual hydrocarbons and

monocarboxylic acids isolated from a Murchison sample by a freeze-thawultrasonication technique. The abundances of monocarboxylic acids and

saturated hydrocarbons decreased with increasing carbon number and the

acids are more abundant than the hydrocarbon with the same carbon number.

For both classes of compounds, the 13C to 12C ratios decreased with

increasing carbon number in a roughly parallel manner, and each carboxylic

acid exhibits a higher i sotopicTnum_er than the hydrocarbon containing

the same number of carbon atoms. These trends are consistent with a

kinetically controlled synthesis of higher homologues from lower ones.

4O
N86-26846

CHARACTERIZATION OF BIOGENIC ELEMENTS IN INTERPLANETARY DUST PARTICLES

T. E. Bunch*

Life Science Division

NASA-Ames Research Center

Moffett Field, CA 94035

We assume that comets and cometary particles that we have collected at high

altitudes via the U-2 aircraft have been stored in a mostly nonalteratlon

environment for most of their lifetime. If this assumption is correct,

then we have a unique opportunity to study near pristine samples, which

will allow us insight into the origin of early solar system materials and

possibly interstellar matter. Moreover we may be able to understand the

evolution of biogenlc elements and their compounds from stellar formation

through the interstellar medium to their present day configuration.

Those particles that we designate cometary are aggregates of amorphous

materials including carbon, iron-magnesium silicates, sulfides, metal and

trace amounts of unusual phases. Most aggregates are carbon-rlch with

major and minor element abundances similar to a fine-grained matrix of

carbonaceous chondrites.

Several particles have been analyzed by a laser microprobe. The negative

ionic species identified to date include carbon clusters (C 2- thru C13-),

protonated carbon clusters (C2H-, C3H- etc.),CN-, HCN-, CNO-, PO2- , PO 3- S-,

S2- and OH-. These species are similar to those observed in cometary

spectra and they support the assumption that organic materials are present.

The occurrence of phosphate ions suggests the presence of apatlte or

whltlocklte.

Cometary particle characteristics may indicate that the component grains

represent primitive unaltered dust whose overall properties are extremely

similar to altered "primitive" dust in carbonaceous chondrites.

...."4 "_

_J

41
t

N86-26847

BOUNDARY CONDITIONS FOR THE PALEOENVIRONMENT:

CHEMICAL AND PHYSICAL PROCESSES IN DENSE INTERSTELLAR CLOUDS

William M. Irvine*

F. Peter Schloerb

Lucy M. Ziurys

Department of Physics and Astronomy and

Five College Radio Astronomy Observatory

University of Massachusetts

Amherst, MA 01003

It is now well established that stars, and presumably planetary systems,

form in dense interstellar clouds of gas and "dust". In individual cases

such clouds may contain as much material as millions of Suns, making them

the most massive objects in the Galaxy. More than 60 molecular species,

the vast majority of them organic, have been identified in the gas phase,

and the particulate matter may also be rich in complex organics. These

"molecular clouds" thus play a crucial role in the history of the biogenic

elements, intermediate between the diffuse interstellar gas which is

primarily atomic in composition, and the solar nebula itself, in which the

Sun and planets actually for_ed. The present research includes searches

for important new interstellar constituents; observations relevant to

differentiating between different models for the chemical processes that

are important in the interstellar environment; and coordinated studies of

the chemistry, physics, and dynamics of molecular clouds which are the

sites or possible future sites of star formation.

Recent research has included the detection and study of four new interstellar molecules: methylcyanoacetylene (CH3C3N), tricarbon monoxide

(C30) , propynylidine (C3H), and cyclopropenylidene (C3H2), the latter

being the first interstellar hydrocarbon ring; searches which have placed

upper limits on the abundance of several other potential constituents of

interstellar clouds, including molecular oxygen, CH3NC, HCCN, and

CH3CH2C2H; quantitative studies of comparative molecular abundances

in different types of interstellar clouds, which have resulted in the first

detection in cold, quiescent clouds of SO 2, CH3CHO, and CH3OH; investigation of reaction pathways for astrochemistry from a comparison of theory

and the observed abundance of related species such as isomers and isotopic

variants; studies of possible "tracers" of energenic events related to star

formation, including silicon and sulfur containing molecules; and mapping

of physical, chemical, and dynamical properties over extended regions of

nearby cold molecular clouds.

42
N86-26848

Interstellar isomers

Doug DeFrees*

Molecular Research Institute

Palo Alto, CA 94304

Doug McLean

IBM Research Laboratory

San Jose, CA 95193

Eric Herbst

Duke University

Durham, NC 27706

The most complex chemical systems known are those characterizing organic life on

earth's surface. They exist at the end of a long evolutionary chain of chemical events

which extends from a hot cloud of hydrogen and helium atoms very shortly after the big

bang to the earth's present biosphere. While many of the links in this chain were forged

on the planet's surface, the raw materials came from the solar nebula. Studies of

structures in the galaxy which are believed to be analogous to the solar nebula have shown

that they have an important organic-molecular component. (Thus, they are called

molecular clouds). Furthermore, evidence for the existence of organic molecules in the

interstellar precursor to our own solar system lie in the carbonaceous meteorites, phases

of which have been shown to have had an interstellar origin. Knowledge of the chemical

and physical conditions which prevailed as the earth formed is vital to achieving an

understanding of those links in the long chain of chemical events which led to the

evolution of life on earth.

Both observational and theoretical studies of molecular clouds are hindered by many

difficulties. One way to partially circumvent the difficulties of characterizing the

chemistry within these objects is to study the relative abundances of isomers which are

synthesized from a common set of precursors. Unfortunately, only one such system has

been confirmed, the HCN/ITNC pair of isomers. While the basic outlines of its chemistry

have been known for some years, there are still many aspects of the chemistry which are

unclear. Another potential pair of isomers is HCO+/HOC+; HCO + is an abundant

interstellar molecule and a tentative identification of HOC + has been made in Sgr B2.

This identification is being challenged, however, based on theoretical and laboratory

evidence that HOC + reacts with H 2. Another potential pair of interstellar isomers is

methyl cyanide (CH3CN, acetonitrile) and methyl isocyanide (CHaNC). The cyanide is

well known, however the isocyanide has yet to be observed despite theoretical prc:! ictions

that appreciable quantities should be present.

43
• . ¥_

N86-268 9

..

PHOTOLYSIS PRODUCTS OF CO, NH 3 AND H20 AND THEIR

SIGNIFICANCE TO REACTIONS ON INTERSTELLAR GRAINS I

James P. Ferris*

Rensselaer Polytechnic Institute

Troy, NY 12180-3590

Interstellar gas and grains comprise about I0 percent of the mass of the

stars in our galaxy. A typical grain consists of a silicate core and

a mantle of organics. If the grain is present in a diffuse cloud of interstellar gas the organic mantle consists of relatively non-volatile higher

molecular weight compounds. Grains in denser clouds of interstellar dust

are believed to be coated with volatile inorganic and organic compounds

(H20 , CH4, C02, CO, NH 3) along with the higher molecular weight organics.

Previous studies focussed 2 on modelling the photochemical processes which

may occur on grains when the volatile inorganic compounds are converted

to the nonvolatile organic compounds. 3

With the increase in evidence that interstellar grains are the basic building blocks of comets and with the realization that comet collisions with

the earth have probably occurred at a much higher frequency than earlier

assumed it may be presumed that interstellar dust chemistry played an

important role in the early chemistry of the earth.

As a part of the study of the photochemical processes taking place on

interstellar grains the photolysis of mixtures of CO, NH 3 and H20 was

performed at 10°K, 77°K and 298°K. The reaction products were determined

by GC/MS and HPLC analysis to be lactic acid, glycolic acid, hydroxyacetamide, urea, biuret, oxamic acid, oxamide, glyceric acid and glyceramide.

Ethylene glycol and glycerol were also detected but it is not clear at

present whether these are true photoproducts or contaminants. The mechanism

of formation of these molecules will be discussed as well as their possible

significance to the origins of life.

I. A collaborative study with J. M. Greenberg.

2. J. M. Greenberg:1982, Submillimetre Wave Astronomy, (ed. by D. Phillips

and J. E. Beckman), Cambridge University Press.

3. J. M. Greenberg:1984, Scientific American 250[6], 124-135.

44
N 86 -.26 8 5 0

OBSERVATIONAL EXOBIOLOGY

Jill Tarter*

University of California Berkeley Astronomy Department

SETI Institute

During the past year, two workshops on Exobiology from Earth Orbit

have been held at NASA Ames Research Center under the direction of

co-chairman John Billingham (NASA Ames) and Bill Irvine (University of

Massachusetts). The central concern of these workshops was to examine

the possibilities for conducting exobiology research from some of the

many spacecraft and platforms that will be placed into Earth orbit in the

coming decades. The workshops focussed on three different types of

opportunities: collection of pristine samples of interstellar material,

in situ experiments, and telescopic observations relating to origin and

evolution of the biogenic elements and compounds. This last topic is

referred to as observational exobiology, and does indeed offer exciting

opportunities for research not possible from ground-based facilities.

The Earth's atmosphere absorbs partially or completely many

ultraviolet, infrare_ and sub-millimeter wavelengths. Atmospheric seeing

distorts small images, imposing a limit on the achievable angular

resolution at optical and infrared wavelengths that is much poorer than

the intrinsic capability of telescope optics. The atomic and molecular

species of the atmosphere (particularly 02 and H20) confuse or prevent

the spectral studies of similar compounds outside of the terrestrial

environment. Telescopes placed in orbit above the atmosphere avoid these

problems and enjoy a unique view of the universe. There are many complex

questions pertaining to the origin and evolution of the biogenic elements

and compounds and the existence of terrestrial types of planets elsewhere

that can only be tackled from orbiting facilities. The workshops

considered the detailed nature of the spacecraft, platforms and

instrumentation most likely to be launched by the United States and

Europe in the near future in an attempt to determine what observational

programs would be tractable and which areas of interest to exobiology

required hardware capabilities beyond those currently envisioned. In

addition it was recognized that a vigorous program of laboratory and

theoretical support studies was crucial to the ability to correctly

interpret and understand the observations pertaining to the complex gas

phase or grain surface organic chemistry occurring in non-terrestrial

environments.

A second draft of a report on these workshops is in preparation.

The final version of that report will contain a prioritized list of

observations that would be of value to the exobiology community, with

particular emphasis on any areas that are likely to be overlooked by the

traditional astronomical users of the orbiting observatories. This

should serve as a starting point for encouraging cooperative proposals

between the exobiology and astronomical communities for observing time on

established facilities and possible modification of future spacecraft,

whose instrument complement is not yet fixed.

45
7

Session II

Prebiotlc Evolution--Planetary

46
THE PRODUCTION OF TRACE GASES BY PHOTOCHEMISTRY AND LIGHTNING IN

THE EARLY ATMOSPHERE

Joel S. Levine* and Geoffrey M. Tennille

NASA Langley Research Center, Hampton, VA 23665

Kenneth M. Towe

Dept. of Paleobiology, Smithsonian Institution, Washington, DC 20560

Raj K. Khanna

Dept. of Chemistry, University of Maryland, College Park, MD 20742

The composition and photochemistry of the early atmosphere were of major

importance in chemical evolution and the origin and evolution of life on our

planet. The early atmosphere provided the material that, through chemical

evolution formed organic molecules of increasing complexity, eventually forming

the first living systems. Atmospheric species most probably provided the

shielding from biologically lethal solar ultraviolet (UV) radiation so that the

newly formed life could thrive and evolve. The shielding of life from UV

radiation could have occurred either in the atmosphere or in the early oceans,

although it is known that pure ocean water is a very poor UV absorber. Our

understanding of the UV shielding of the newly formed life is very uncertain.

Recent atmospheric calculations by several investigators suggest that the

prebiological atmosphere was most probably composed of nitrogen (N2) , carbon

dioxide (C02) , and water vapor (H20), resulting from volatile outgassing, as

opposed to the older view of a strongly reducing early atmosphere composed of

methane (CH4) , ammonia (NH3), and hydrogen (H2). Photochemical calculations

indicate that methane would have been readily destroyed via reaction with the

hydroxyl radical (OH) produced from water vapor and that ammonia would have been

readily lost via photolysis and rainout. The rapid loss of methane and ammonia,

coupled with the absence of a significant source of these gases, suggest that

atmospheric methane and ammonia were very short-lived, if they were present at

all. An early atmosphere of N2, C02, and H20 is stable and leads to the chemical

production of a number of atmospheric species of biological significance,

including oxygen (02), ozone (03), carbon monoxide (CO), formaldehyde (H2CO), and

hydrogen cyanide (HCN). Using a photochemical model of the early atmosphere, we

have investigated the chemical production of these species over a wide range of

atmospheric parameters. These calculations indicate that early atmospheric

levels of 03 were significantly below the levels needed to provide UV shielding.

We have also investigated the fate of volcanically emitted sulfur species, e.g.

sulfur dioxide (S02) and hydrogen sulfide (H2S), in the early atmosphere to

assess their UV shielding properties. Our photochemical calculations indicate

that these species were of insufficient levels, due in part to their short

photochemical lifetimes, to provide UV shielding. However, laboratory

experiments conducted in our lightning facility indicate that a mixture of N2,

C02, and H20 exposed to lightning produces significant yields of nitric oxide

(NO). Once formed by lightning, NO is chemically converted to water-soluble

nitric acid (HN03), which readily "rains" out of the atmosphere, providing a

significant source of nitrate (NO3-) to the early oceans. As pointed out by

Rambler and Margulis, nitrate dissolved in the ocean can act to increase the

turbidity of the upper levels of the ocean and may help to attenuate solar UV

radiation.

47
N86-26852

THE ORGANIC AEROSOLS OF TITAN

B.N. Khare, C. Sagan,* W.R. Thompson, E.T. Arakawa, F. Suits, T.A.

Callcott, M.W. Williams, S. Shrader, H. Ogino, T.O. Willingham and B.

Nagy.

*Laboratory for Planetary Studies, Cornell University, Ithaca, NY 14853.

A dark reddish organic solid, called tholin, is synthesized from

simulated Titanian atmospheres by irradiation with high energy electrons

in a plasma discharge. The visible reflection spectrum of this tholin

is found to be similar to that of high altitude aerosols responsible for

the albedo and reddish color of Titan. The real (n) and imaginary (k)

parts of the complex refractive index of thin films of Titan tholin prepared by continuous D.C. discharge through a 0.9 N2/O.I CH4 gas mixture

at 0.2 mb is determined from x-ray to microwave frequencies. Values of

n (: 1.65) and k (: 0.004 to 0.08) in the visible are consistent with

deductions made by ground-based and spaceborne observations of Titan.

Many infrared absorption features are present in k(_), including the

4.6 _m nitrile band. Molecular analysis of the volatile component of

this tholin was performed by sequential and non-sequential pyrolytic gas

chromatography/mass spectrometry. More than one hundred organic compounds are released; tentative identifications include saturated and

unsaturated aliphatic hydrocarbons, substituted polycyclic aromatics,

nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the

purine, adenine. In addition, acid hydrolysis produces a racemic mixture of biological and non-biological amino acids. Many of these

molecules are implicated in the origin of life on Earth, suggesting

Titan as a contemporary laboratory environment for prebiological organic

chemistry on a planetary scale.

In Advances in Space Science, 1985, in press.

48
N86-26853

THE D TO H RATIO ON TITA_ AND THE PLANETS:

IMPLICATIONS FOR ORIGIN AND EVOLUTION OF

PLANETARY ATMOSPHERES

J.P. Pinto*, Harvard University, Cambridge, MA 02138, J.I.

Lunine, S.-J. Kim, and Y.L. Yung, California Institute of

Technology, Pasadena, CA 91125

Measurements of deuterated methane show that Titan's atmosphere is

enriched by at least several times in deuterium compared to the major

planets. Potential causative factors for this enrichment are condensation to

form tropospheric methane clouds, fractionation occurring over a hypothetical

CH4-C2H 6 ocean and between the ocean and the clathrate crust beneath,

fractionation which occurred during the formation of Titan and fractionation

occurring as a result of the evolution of Titan's atmosphere. The greater

part of the observed fractionation is probably derived from the formation

of Titan and the subsequent evolution of Titan's atmosphere driven by photochemistry. The latter process is developed here for the first time. The D/H

ratio in a planetary atmosphere is one readily available measure of the

origin and evolution of the hydrogen bearing volatiles on the planet.

Comparison between D/H ratio in the inner solar system (Earth, Mars and

Venus) and the outer solar system (Jupiter, Saturn and Titan) may pose

important constraints on current theories.

49
NSe-2eS5 

MEASUREMENTS OF PHYSICAL PROPERTIES

OF MODEL TITAN ATMOSPHERES

ThemesW. :Sc_ttergoo_

SUNYatStony Broo_

Stony Brook, NYt 1794

end

Chang,Chris McKoy,BonnieO'Heraend81ennCerle

NASA-AmesReseerd_Center

Moffett Field, CA940:55

One of the major goals of NASA is the study of the nature and

evolutlon of the solar system, In partlcular,how the chemlcal and

physical evolution of the solar system may have influencedthe origin

and evolutlon of life.As part of thls effort,the study of the chemlcal

and physical properties of bodies in our solar system Is necessary In

order to help define the conditions under which evolutlon must have

taken place. Of the objects In the solar system, one of the most

interesting is Titan, as ground-based and spacecraft (Voyager)

observations of this satellite show it to possess a substantial

atmosphere dominated by nitrogen. Present In the atmosphere are

also simple hydrocarbons, nitrilesand CO and C02, along with at least

three haze layers,one of which gives the satellite its orange-red

color. The presence of these materials Indicates the occurrence (past

or present) of active chemlcal processes. Thus study of the nature of

the materials present In Titan'satmosphere should provide Important

data points for correlating the relatlonshlp between chemlcal

evolution and planetary evolutlon Inour solar system.

One aspect of the study of Tltan's atmosphere Is the elucidation of

the chemical and physical nature of the aerosols. In order to

facilitatethls,a program to produce laboratory synthesized model

materials for Titan'saerosol and to study their chemical and physical

properties is now In progress. Various processes, including electric

discharge, photolysls by ultravlolet light, and Irradiation by

energetic particles,will be used to produce the materlals. A firstset

of experiments where a nominal Titan mixture (97% N2, 3_ CH4, 0.2_

H2) was subjected to pulsed high-temperature shocks yielded a

reddish-brown waxy solid. This material was then subjected to

pyrolysis/gas chromatography, a technique that has been proposed as

a method for analysis of the Titan aerosols. Preliminary results show

the material to consist of simple hydrocarbons but little else, at

least up to temperatures of 600°C. Since the material was colored

(and solid), compounds other than those mentioned above must be

present. Work will contlnue on refining the analytical technique in

order to learn more about the nature of candidate Titan aerosols and

to provide a method which will enable the analysis of the actual

aerosols from a future Titan probe.

50
k

7

Session llI

Solar System Exploration

51
N86-268 5

Experlmenta_ Basis for a Titan Probe Organic Analysis

C.P. McKay* ,I, T. W. Sosttergood2, W. d. Borucki 1, d. F. Kesttng1, endS. L. Miller 3

1. NASA- Ames Research Center, Moffatt Field, CA94035

2. SUNYat Stony Brook, Stony Brook, NY ! i 794

3. University of California, San Diego, Le doila, CA92093

The recent Voyager flyby of Titan produced evidence for at least nine

organic compounds in that atmosphere that are heavier than methane.

Several models of Tltan's atmosphere, as well as laboratory simulations,

suggest the presence of organics considerably more complex than those

observed. An entry probe for the detailed study of Tltan's atmosphere Is

currently being planned by NASA and the European Space Agency. Clearly,

the opportunity to make in situ measurements of the chemlcal

composition of thls atmosphere from the exobiologlcal perspectlve is

unlque and will provlde valuable informatlon leading to a more

comprehenslve understanding of the relationship between the chemical

and physical evolutlon of the solar system and the appearance of life.

However, to ensure that these in situ measurements are definitlve with

respect to Tltan's atmosphere, experiment concepts, and the related

Instrumentatlon, must be carefully developed specifically for such a

mlsslon. To thls end, the posslble composltlon of the envlronment to be

analyzedmust be bracketedand model samples must be providedfor

instrumentationdevelopmentstudies.Allconflictingtheoreticalmodels

of theenvironmentwillbe examined and allrealpossibilitieswillbe

Included.

Laboratorystudiesto definethe optimum flightexperimentand sampling

strategyfora Titanentryprobeare currentlybeingconducted.Titan

mixtures(97_ N2, 31_CH 4) are beingsubjectedto a varietyof energy

sourcesincludinghighvoltageelectronsfrom a DC discharge,high

currentelectricshock,and laserdetonation.Gaseous and solidproducts

areproducedwhlch are thenanalyzed.Samples from these experiments

are alsoprovidedto candidateflightexperimentsas models for

instrumentdevelopment studies.Preliminaryresultsshow thatexisting

theoreticalmodels forchemistry inTitan'satmosphere cannot

adequatelyexplainthe presenceand abundanceof alltracegases

observedIntheseexperiments.A more comprehensive theoreticalmodel

Isbeingdevelopedand willbe presented.

52
A GAS CHROMATOGRAPH

FOR A

EXpER, N 6 : 26 856

TITAN ENTRY PROBE

01ennC.C='le*, DanielR.Kojiro, BonnieJ.O'Hare,JoseR.Velentin,VerneR.Oberbeck,

- AmesResearchCenter

I'loffettField,CA94035

end

ThomasW._:atteroood

,SUNYetStonyBrook

StonyBrook,NYl 1794

A major goal In the study of Exobiology ls to understand the relationship

between the chemlcal and physical evolution of the solar system and the

appearance of life. Within this context, the elucidation of the structure,

particularly of the organics, of the atmosphere of Tltan ls one of the

most Important tasks yet to be accomplished towards this goal. Recent

observations of Tltan by Voyager have provided a more complete picture

of its atmosphere. Not only were volatile organics, principally methane,

ldentlfled and measured, but significantly, a dark-orange to brown haze

was observed In the upper atmosphere. Thls haze or aerosol ls thought to

be conglomerations of organic molecules which are produced In the upper

atmosphere by posslbly photochemistry or lightning. Clearly, detalled

measurements or thls haze, and other aerosol layers, In conjunction with

the gaseous molecules In Tltan's atmosphere wlll be Important for any

future entry probe mlsslons.

Development of a gas chromatographic (GC) technique for analysls of

aerosols and volatile organlcs from a Tltan entry probe ls now In

Progress. Prellmlnary lnvestlgatlons of aerosol collectors have shown

that an electrostatic devlce should be the most efflclent for the partlcle

sizes expected In Titan's atmosphere. Such a device particularly lends

Itself to development of a slmple pyrolyzer whlch can be used to break

down any collected organic conglomerate structures Into volatlle

fragments. Those fragments can subsequently be analyzed by OC

provldlng Information about the orlglnal chemlcal structure of the

aerosol. Studles show that as llttle as I-5 l_g of model aerosol can be

successfully analyzed. Hlgh altltude (_ 200 kin) atmospherlc gas

samplingwillalsobe importanton Titandue to thegreatdepthof the

atmosphere. Studies show that a GCanalysis of model Titan atmospheres

at pressures approximating thls altltude (2 mbar) can be made with a

sensitivity of a few ten's of parts-per-billion for the trace gases of

interest.

53
MOLECULAR AND ELEMENTAL DUST ANALYZER (MEDA)

FOR THE

COMET RENDEZVOUS ASTEROID FLYBY MISSION

Bonnied. O'Hera*, OlennC.Cerle.

NASA-AmesResearchCenter

Moffett Field, CA94035

end

BentonC.Clark

MartinMariettaDenver Aerospace

Denver,CO80201

Comets are some of the most primitive bodies in the solar system and

thereforeshould contain elemental, chemlcal, and Isotopicrecords of the

early historyof the solar system. Determining the chemical and elemental

composition, wlth emphasis on the biogenic elements and their

compounds, of the grains and dust In the cometary nucleus would ald in

placingchemical and physlcal bounds on the environment in which comets

formed as well as providing an inventory of elements and compounds

available for planetary accretion of cometary material by the Earth. An

opportunlty to perform in situ analyses of a comet nucleus exists with

the Comet Rendezvous Asteroid Flyby (CRAF) mission. An integrated gas

chromatograph/X-ray fluorescence Instrument (MEDA), belng proposed for

Inclusion onboard the CRAF spacecraft, wlll measure the molecular and

elemental constltuents of collected dust grains and Ices.

The gas chromatograph (GC), employing hellum Ionization detectors and

three columns designed to separate llght gases, l.e, N2, CO, CO2, polar

gases, 1.e, H20, and hydrocarbons, I.e., _ C4, will measure the volatile

compounds of the biogenic elements (C,H,O,N,S) thermally released from

collected dust grains. The sensitivity of the GC for compounds of interest

is at the plcogram level. X-ray fluorescence (XRF) utilizes cryogenically

cooled SI(L1) solld state detectors of nominal 150 eV resolution at 5.9

keV. Excitation is by X-rays from Fe-55 radioisotope and alpha

particles/X-rays from Cm-244 radioisotope sources. The XRF measures

the elemental composition of the collected dust at a detection limit of

100 nanograms per square centimeter for elements such as 51, Fe, O, 5,

Ca, and C. Based on laboratory work with carbonaceous meteorites, both

the GC and XRF can perform meaningful analyses with a few micrograms

of collected comet dust.

54
N86-26858

INVESTIGATION OF POROUS POLYMER GAS CHROMATOGRAPHIC

PACKINGS FOR ATMOSPHERIC ANALYSIS

OF EXTRATERRESTRIAL BODIES

01ennE.Pollock*

N&SA-AmesResearchCenter

Moffett Field,CA 9403_

For extraterrestrial probes, whether planetary, moon or cometary,

atmospheric composition is an important analysis and gas

chromatography (GC) is the technique best suited to carry it out. The

rationale for such analysis is that the data may provide important

information on the origin and evolution of the solar system, chemical

evolution and life. Gas chromatographic instrumentation was used quite

successfully aboard the Mars and Venus probes, however, for missions of

much greater duration, weight, power and volume considerations have

caused us to seek ways and means to reduce significantly the size of the

instrumentation and increase its sensitivity. Column packings are the

functional components of a GC system which cause the separation of

multicomponent gas mixtures into individual elutable and measurable

peaks for quantitation. The improvement of GC column packings is the

subject of this study.

Measurement of the permanent gases in the atmospheres of mission

targets is a major objective. A16 meter long Porapak N column was used

on the Venus probe and required a rather high carrier gas flow rate. We

have, therefore, surveyed commercial porous polymer types which had

some ability to resolve nitrogen, oxygen, argon and carbon monoxide

gases. Porapaks N and O appeared superior to most. Batch to batch

variation, however, was quite wide, so we learned how to synthesize

porous polymers and investigated some of the factors affecting the

separations. A polymer was synthesized which was superior to all

commercial products and allowed at least a 50_ reduction in length and

flow rate of carrier gas. Similar studies were made concerning the

separation of hydrocarbons and new porous polymers have been

synthesized which represent significant improvements in time of

analysis, column length, and carrier gas flow rate. Further work will

include column development for polar gases and water and investigation

of capillary column usage to reduce further carrier gas requirements.

55
t N86:26859

HINIATURE HETASTABLE IONIZATION DETECTOR5

FOR

EXOBIOLOGY FLI GHT EXPERIHENT5

FritzH.Woeller*

NASA - Ames Research Center

MoffettField,CA 94035

The explorationof the solarsystem and an understandingof the originof

life are two of NASA'S important goals. An analysis of the planetary

atmospheres and volatiles associated with life and the origin of life,

will provide information necessary for scientists to attain these goals.

Investigating the history and abundances of the biogenic elements and

their compounds provides a basis for a detailed understanding of

exobiology in the solar system. Gas chromatography has already proven

to be a highly successful analytical technique for NASA's flight

programs. Gas Chromatographs (GC) have been flown to both Mars and

Venus where detailed compositional measurements were made.

Although quite small and relatively sensitive when compared to

commercially available instruments, these instruments do not appear

adequate for the future missions currently being planned. The

Metastable Ionization Detector (MID) is three orders of magnitude more

sensitive than the thermal conductivity detectors used on previous flight

instruments. The miniature MID provides scientists with a much

smaller and highly sensitive detector for flight gas chromatographs.

A miniatureMID featuringan unconventionaltriaxialelectrode

configurationhas been developedand used routinelyinour laboratories.

Althoughmuch smallerand lighterthan the commercial MID, its

performancecharacteristicsparallelthose of the traditionaldesign.

The detectoriscompatiblewith themodulated voltagecircuitry,also

developed here, and thus can perform over an expanded response range of

more than 7 orders of magnitude. A micro volume version of a miniature

MID, with an internal volume of less than 8 i_1, has recently been

designed and is now being tested. The micro volume MID uses carrier

gas flow rates of = 2 cc/min thus eliminating the need for makeup gas

when capillary columns are used. These prototype detectors represent a

three order of magnitude increase in sensitivity and a decrease in weight

and volume of two to three orders of magnitude when compared to

previous flight GCdetectors.

56
N86-26860

'. MULTIPLEX GAS CHROMATOGRAPHY: A NOVEL ANALYTICAL

TECHNIQUE FOR FUTURE PLANETARY STUDIES

R. Yslentln*andOlannC.Carle

NA6A-AmesResearchCenter

MoffettField,CA94055

and

dohn B.Phillips

SouthernIllinois UniversityatCarbondsle

Carbon(hie,IL 62901

Determination of molecular species comprised of the biogenic elements in

the atmospheres of planets and moons of the solar system is one of the

foremost requirements of the exobiologiststudying chemical evolution and

the originof life.Flightexperiments have been conducted on both Mars and

Venus in the past and a wealth of data has been acquired by the gas

chromatograph, mass spectrometer, and gas chromatograph/mass

spectrometer. Future missions to explore Titan,Saturn,Mars, and Venus

will require advanced instrumentation concepts which are highly sensitive,

efficient,physicallysmall, and capable of analyzing complex mixtures.

Recent advances in gas chromatography suggest that conventional gas

chromatography isstillone of the most powerful methods availableto

conduct the desired analyses in future constrained missions, but limitations

in the technique stillexist which can be alleviatedwith multiplex gas

chromatography.

Multiplex chromatography is a technique where many samples are

pseudo-randomly introduced to the chromatograph without regard to elution

of preceding components. The resulting data are then reduced using

mathematical techniques such as cross-correlation or Fourier Transforms.

To demonstrate the utility of this technique for future solar system

exploration, chemical modulators have been developed. Several advantages

have been realized from this technique in combination with these

modulators: improvement in detection limits of several orders of magnitude,

improvement in the analysis of complex mixtures by selectively modulating

some of the components present in the sample, increase in the number of

analyses that can be conducted in a given period of time, and reduction in

the amount of expendables needed to run an analysis. In order to apply this

technique In a real application, methane in ambient air was monitored

continuously over a period of one week. By using ambient air as its own

carrier all expendables beyond power were eliminated.

57
N86-26861

ION HOBILITY DRIFT 5PECTROt'IETRY (IHDS)

AS A

FLI 6HT ANALYTI CAL INSTRUHENT TECHNIQUE

Daniel R. Kojiro and Glenn C. CaMe*

NASA - Ames Research Center

Moffett Field, CA 94035

A detailed knowledge of the history and abundances of the biogenic

elements and their compounds throughout the solar system can provide

the exobiologist 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. In particular, analysis of the complex organics

expected for a mission to Titan may tax the limits of current analytical

technology. A flight instrument utilizing IMDS technology can provide

scientists with a powerful means of obtaining this information.

The Ion Mobility Drift Spectrometer is an ion molecule reactor coupled

with an ion drift spectrometer. Sample molecules are ionized to form

product ions in the reactant region. An electric field moves the ions

through a drift region against the flow of a drift gas where they are

separated according to their size and structure producing an ion mobility

spectrum. These spectra provide the IMDS with virtually universal

sample identification capability. To conform to the rigid limits of

weight, volume and consumables placed on flight instrumentation,

several aspects of the IMD5 must be studied and redesigned for Might

use. In addition to miniaturization of the instrument, a reduction in the

high flow rates used for the drift gas is an obvious necessary

consideration. The effect of drastically reduced drift flow rates on

IMD5 spectra was investigated by lowering flow rates from SOOmi/min

to 50 mi/min. Changes in peak shape, drift time and total spectra were

studied at each Mow rate. Although changes did occur, IMD5 analysis

appears acceptabl e at the lower Mow rates. Investigations into

alternate drift gases and reactive carrier gases are also being pursued.

58

_r%L
. N86- 6862

NEW TECHNIQUES FOR THE DETECTION AND CAPTURE OF

HICROHETEOROIDS

John H. Wolfe*, San Jose State University, San Jose, CA 95192

Theodore E. Bunch and Glenn C. Carle, NASA Ames Research

Center, Moffett Field, CA 94035

Inorder to understand the originand distributionof the biogenic

elements and their compounds in the solar system, itwill be necessary

to study material from many classes of objects.Chemical, elemental,

and isotopicmeasurements of returned samples of comets, asteroids,

and possibly extra-solar system dust clouds would provide information

on a particularlyimportant class:the primitive objects.Extraterrestrial

micron-sized particles in the vicinityof earth are one source of such

materials that might otherwise be inaccessible.The Space Station

appears to be an eminently suitableplatform from which to collectand

detect these various particles.The primary challenge,however, is to

collect intact,uncontaminated particleswhich will be encountered at

tens of kilometers per seconds.

A concept for a micrometeoroid detector that could be deployed from

Space Station has been developed which uses a large area detector plate

implanted with acoustic transducers. When an impact event occurs, the

resultingsignal is subjected to spectral analysis providing positive

detection,momentum information,and angle of incidence.The primary

advantage of this detector is the large area which increases the

probabilityof measuring events.A concept of a nondestructive

micrometeoroid collectorfor use from Space Station has also been

developed.The collectorutilizesinputport charging of the incoming

particlefollowed by staged high voltage deceleration for nondestructive

capture.Low velocity particles(localcontamination) would be rejected

due to insufficientenergy and only uncontaminated micrometeoroids

would be collected.Particlesso collectedwould then be returned to

Earth for subsequent analysis.

59
Session IV

Prebiotic Evolution--Molecular

6O
N.86- 26863

ENERGY YIELDS IN THE PREBIOTIC SYNTHESIS OF

HYDROGEN CYANIDE AND FORMALDEHYDE

Roscoe Stribling and Stanley L. Miller*

Department of Chemistry, B-017

University of California, San Diego

La Jolla, California 92093

Prebiotic experiments are usually reported in terms of carbon yields,

i.e., the yield of product based on the total carbon in the system. These

experiments usually involve a large input of energy and are designed to maximize the yields of product. However, large inputs of energy result in multiple

activation of the reactants and products. A more realistic prebiotic experiment is to remove the products of the activation step so they are not exposed

a second time to the energy source. This is equivalent to transporting the

products synthesized in the primitive atmosphere to the ocean, and thereby

protecting them from destruction by atmospheric energy sources. Experiments

of this type, using lower inputs of energy, give energy yields (moles of

products/joule) which can be used to estimate the relative importance of the

different energy sources on the primitive earth.

Simulated prebiotic atmospheres containing either CHa, CO or CO_ with N^,

HpO and variable amounts of Hp were subjected to a high f_equency Tesla _ coil.

S_mples of the aqueous phase _ere taken at various time intervals from I hr to

7 days, and the energy yields were obtained by extrapolation to zero time.

The samples were analyzed for HCN with the cyanide electrode and for H2CO by

chromotropic acid. The spark energy was estimated by calorimetry. The temperature rise in an insulated discharge flask was compared with the temperature rise from a resistance heater in the same flask.

The energy yields for HCN production are about 10 n moles/joule with CH_

(H2/CH 4 = I), 5 n moles/joule with CO (Hp/CO = 2), and 0.4 n moles/joule with

COp (Hp/COp = 2). In contrast, the repotted carbon yields for HCN synthesis

wi_h t_e aSove mixtures are nearly equal. This demonstrates the importance of

using energy yields as a basis of comparison of various energy sources and

atmospheric compositions.

The energy yields for HpCO production are about 2 n moles/joule with CHg

(H_/CH a = I), 15 n moles/jouIe with CO (H_/CO = 2), and 0.3 n moles/joule with

CO_ (HI/CO p = 3). The reported carbon yields of HpCO production with these

mixtures axe also nearly equal.

These results will be compared with calculated production rates of HCN

and H2CO from lightning and a number of photochemical processes on the primitive earth.

61
SYNTHESISANDANALYSISIN STUDIESOFCHEMICALEVOLUTION

Cyril Ponnamperuma,Mitchell K. Hobish*, Kensei Kobayashi,

Hua Lu-Lin, Nalinie Senaratne

Laboratory of Chemical Evolution

Department of Chemistry

University of Maryland

College Park, MD20742

Studies of the various processes that may have given rise to life on the

earth have demonstrated the appropriateness of an approach that makesuse of

analysis and synthesis. Analysis of extraterrestrial samples in the form of

meteorites has demonstrated the presence of several precursors of biomolecules,

most notably a full suite of nucleic acid bases and nucleosldes of biological

significance. These species were determined after exhaustive extraction of the

sample and subsequent analysis using HPLC,GC, MS, and GC-MS. Procedural

blanks indicate that these molecules are likely not the result of contamination

during the extraction and analysis process. Similar species were found as

products of spark discharge experiments in atmospheres thought to mimic

primitive earth conditions. These results indicate that the basic chemistry

underlying these syntheses is common,and that llfe maynot be unique to the

earth.

This lack of "magic" in the formation of important biomolecules takes on

even greater significance whenwe next ask, "What is the nature of the origin

of the genetic code?" Studies underway in our laboratory to address this

question makeuse of proton nuclear magnetic resonance spectroscopy as a probe

to assess associations between selected amino acids and any of several

nucleotides comprising their genetic code and genetic anticode sequences.

These studies demonstrate a clear selectivity by the anticode sequences, thus

confirming the hydrophobicity studies performed by Lacey et al. These studies

further support the contention that life is likely a natural result of the

physics and chemistry of the universe.

62
• . N86-26865

ISOTOPIC CHARACTERISATION OF PREBIOTIC SYNTHESIS OF ORGANIC MATERIAL

John F. Kerridge* Institute of Geophysics, UCLA, Los Angeles, Ca 90024

Sherwood Chang, Ruth Shipp & Kim Wedeking, NASA Ames Research Center,

Moffett Field, Ca 94035

Many primitive meteorites contain an insoluble organic material,

much like terrestrial kerogen, whose mode of origin is currently unknown.

When subjected to stepwise decomposition, this material, unlike its

terrestrial counterpart, reveals characteristic release patterns for the

stable isotopes of carbon, hydrogen and nitrogen as a function of

fractional release of each element. The purpose of this study is to try

to match those release patterns using organic matter synthesised in the

laboratory under controlled conditions. Analogous studies have attempted

to reproduce chemical and structural characteristics of the meteoritic

material by such syntheses. If successful, such a study would shed light

on the origin of kerogen-like organic matter in the early solar system

and, by extension, on prebiotic organic synthesis in general.

The range of possible syntheses, starting materials and reaction

conditions to be investigated is considerable. Samples analysed to date

include: a heavy "oil" produced by Fischer-Tropsch-type catalysis of

CO + H2; a solid residue generated by a plasma discharge in CO + H2 + N2;

a solid deposited on the electrodes of a Miller-Urey synthesis operating

on CH 4 + H20 + N2; and a solid residue formed by polymerisation of light

hydrocarbons produced by a Miller-Urey discharge acting on CH_.

Significant structure is observed in the release patterns for the

carbon and hydrogen isotopes from the synthetic samples, though there is

little evidence for isotopic fractionation during the analysis itself.

For neither carbon nor hydrogen do the patterns observed so far resemble

those characteristic of meteoritic material; the release patterns for

carbon show the same magnitude of isotopic variations as do meteoritic

kerogens but differ in detail, whereas for D/H ratios there are vast

discrepancies in magnitude as well as in shape of the release profiles.

Besides the obvious interpretation of these discrepancies in terms of

incomplete sampling of processes, starting materials and/or reaction

conditions, it is possible that the meteoritic material represents a

mixture of phases produced in different circumstances with intrinsically

different isotopic compositions. Evidence bearing on these possibilities

will be discussed.

63
N86-26866 .°

ORIGIN OF LIFE AND IRON-RICH CLAYS

Hyman H. Hartman*

Massachusetts Institute of Technology

Cambridge, _ssachusetts 02139

We are exploring the premise that life began with self-replicating iron-rich

clays. In association with these clays and u.v. light, polar organic

molecules, such as oxalic acid, were synthesized.

The carbonaceous chondrites have both iron-rich clays and organic molecules.

It is convenient to classify meteoritic organic matter into 3 categories:

insoluble polymer, hydrocarbons a_id _olar organics (sol1_le in water).

Recent work on the _D, _N 15 and 6C 13 has made it clear that these three

fractions have been made by three different mechanisms. 1'2

A significant fraction of the insoluble polymer has a 6D which suggests

that it was made in an interstellar medium. 3 The hydrocarbons seem to

have been made on a parent body by a Fischer-Tropsch mechanism. The polar

organics were probably synthesized in a mixture of carbonate (NH4)2C03,

Fe ++ ion and liquid water by radiolysis. In a set of experiments done

with Mike Sweeney and M. Kroll we have looked at the radiolysis of (NH_)2C03

in the presence and absence of Fe ++ ion. The synthesis of glycine in the

presence of Fe ++ ion is 3-4 times that in the absence of ferrous ion.

We are exploring the effects of the addition of hydrocarbons to this mixture.

We are also synthesizing iron-rich clays at low temperature and pressure.

So far the results are not sufficiently crystalline to look for replication.

It should be noted that organic chelating agents such as oxalic acid do

increase the crystallinity of the clays but not sufficiently. We are now

exploring hydrothermal synthesis of iron-rich clays.

i. Robert, F. and Epstein, S. (1982) GCA 46, 81.

2. Becker, R. H. and Epstein, S. (1982-_-GCA 46, 97.

3. Yang, J. and Epstein S. (1983) GCA 477-2199.

64
N8e- 6867

CLAY ENERGETICS IN CHEMICAL EVOLUTION

Lelia M. Coyne*

San Jose State University

Clays have been implicated in the origin of terrestrial life since the

suggestion of Bernal in the 1950's. Originally they were considered as agents

which aid in selecting, concentrating and promoting oligomerization of the

organic monomeric substituents of cellular life forms. However, more recently,

Graham Cairns-Smith has suggested that minerals, with particular emphasis on

clays, may have played a yet more fundamental role. He has suggested that clays

are prototypic life forms in themselves and that they served as a template which

directed the self-assembly of cellular life.

If the "clay-life" theory is to have other than conceptual credibility,

cl_ys must be shown by experiment to execute the operations of cellular life,

net only individually, but also in a sufficiently concerted manner as to produce

some semblance of the functional attributes of living cells. I define the

"operations" of life to include processing of energy (conversion, storage and

transfer); charge and materials (separation, storage and transport, reaction

catalysis and structural stabilization); and information (reception, storage,

retrieval). These operations support the functional attributes of life, which

include adaptive response to environmental stimuli, self-replication with transfer of information and growth and repair.

My current studies are focussed on the ability of clays to absorb, sto_e

and transfer energy under plausible prebiotic conditions and to use this energy

to drive chemistry of prebiotic relevance. Conclusions of the work are applicable to the role of clays either as substrates for organic chemistry, or in

fueling their own life-mimetic processes.

Several aspects of the energy storage/transfer work are being simultaneously pursued. Investigation of the relationship between thermoluminescence

(TL) and electron spin resonance (ESR) in a series of variably Fe/Ca cation

exchanged montmorillonites has revealed iron-iron interactions at high iron

concentrations. Investigation of the range of the forces which produce the

emission of light upon dehydration is being done by measuring the critical

moisture content at which light is released from a series of variably hydrated

kaolins prepared by Pat Costanzo and Ross Giese. The degree of interlayer

hydration markedly affects the profile of light emission on drying. However,

it is thought that this change in profile reflects some compositional changes

in Lhe structural hydroxyls. If so, some unexpected fundamental insights

relating the charge mobility and light release may be gained. The nature of

the _uminescent trigger is being explored by studying light released on wetting

by hydrazine and unsymmetrically substituted dimethylhydrazine (USDMH). Hydrazinc complexes with the kaolin surface, intercalates the layers and chemically

decomposes. USDMH complexes with the surface, intercalates the layers of some,

but not all of the hydrated forms. Formation of the intermediate for the

presumed dominant pathway for decomposition should be sterically hindered.

Preliminary results indicate the light release to be more directly associated

with the intercalation than with the decomposition. Oefinitive interpretation

will require spectroscopic data on the spectral distribution both of the diffuse

reflectance and of the light emission, in order to correct for emission/reabsorption effects. The relationship between energy storage and surface reactivity is being investigated using the decomposition of hydrazine as a chemical

actinometer. The decomposition of hydrazine is proceeding by at least two mechanistically different pathways on the kaolin surface. The effect of energy

storage is being examined.

65
N86-26868

FURTHER WORK ON SODIUM MONTMORILLONITE AS CATALYST

FOR THE

POLYMERIZATION OF ACTIVATED AMINO ACIDS

Frederick R. Eirich*

Polytechnic Institute of

New York

333 Jay Street

Brooklyn, New York 11201

Dr. Mella Paecht-Horowitz

Hebrew University of Jerusalem

Rehovot

Israel

i] When we catalyzed the polycondensation of amino acid acylates

with Na-montmorillonite, the polypeptides were consistently found

to exhibit a distribution of discrete molecular weights, for as

yet undiscovered reasons. One possible explanation was connected

to our stepwise mode of monomer addition. New experiments have

eliminated this possibility, so that we are left with the general

assumption that this discreteness is the result of a preference

of shorter oligomers to add to others of the same length, a

feature that could be attributed to some structure of the

platelet aggregates of our montmorillonite.

2) We have in the past repeatedly looked for the production of

optical stereoisomers, when D,L-amino acids were polymerized on

montmorillonite. Recently, we observed that Na-montmorillonite,

on which Cu-L-proline was adsorbed prior to the polymerization of

D,L -alanine adenylate, produces an excess of about 1.6 : 1 of

D-alanine oligomers (_b-P = 9.5). The latter consist again of a

limited number of fractions (6) of DP's up to 28. Since we used

an optically active surface, the essence of the results lies not

only in the occurrence of optically active oligomers and

polymers, but also in the fact that the latter exhibit the same

molecular weight characteristics as the D,L -polymers.

3) We have also started to polymerize all L -isomers of asperticand adenyl adenylates. In homo- as well as in co-polymerization

(though somewhat less) we encounter severe solubility problems

and, thus, so far obtained only lower oligomers, 2-7. These

findings are possibly significent for the problem of the selection

of L -isomers by early life, and wil_ be further investigated.

4) Preparatory to the work that we contemplate on a parallel

synthesis of amino acid and nucleotide oligomers, we continued

studies on the co-adsorption of amino acids, nucleotides, and

amino acid-nucleotides on montmorillonite. Our findings include

adsorption increases of UMP proportional to the preadsorption

adenine, but not of adenylic acid, and further that the

adsorption of phe, but less so that of lys, is increased when

acetyl-adenylate or ATP are absorbed beforehand. ATP is threefold more adsorbed than AMP, but less than polyadenylic acid or

polyuridylic acid. More work is planned to clarify these

co-adsorption patterns which will serve as a guide for the

planning of parallel amino acid-nucleotide oligomerization

experiments.

66
N86-26869

ADSORPTION AND CONDENSATION OF AMINO ACIDS AND NUCLEOTIDES

WITH SOLUBLE MINERAL SALTS

James Orenberg*

Dept. of Chemistry

San Francisco State U.

1600 Holloway Avenue

San Francisco, CA 94132

Noam Lahav

Dept. of Soil and Water

Faculty of Agriculture

Hebrew Univ. of Jerusalem

Rehovot 76-100, Israel

The directed synthesis of biopolymers in an abiotic environment is presumably a cyclic sequence of steps which may be

realized in a fluctuating environment such as a prebiotic pond

undergoing wetting-drying cycles. Soluble mineral salts have

been proposed as an essential component of this fluctuating

environment. The following sequence may be considered as a

most primitive mechanism of information transfer in a fluctuating environment:(1) adsorption of a biomolecule onto a soluble mineral salt surface to act as an adsorbed template;(2)

specific adsorption of biomonomers onto the adsorbed template;

(3) condensation of the adsorbed biomonomers; and (4) desorption of the elongated oligomer. In this investigation, the

salts selected for study were CaSO4.2H=O(gypsum), SrS04, and

several other metal sulfates and chlorides. Adsorption of the

monomeric species, gly, 5"AMP 5"GMP, and 5"CMP was investigated. The adsorbed template biopolymers used were Poly-A,

Poly-G, Poly-C, and Poly-U.We shall report the results of studies involving these experimental participants, the first two

steps of the proposed primitive information transfer mechanism, and condensation of amino acids to form oligomers in a

fluctuating environment.

67
ti .

,, N86-26870

PALEOSOLS AND THE CHEMICAL EVOLUTION OF THE ATMOSPHERE

H.D. Holland, E.A. Zbinden, and J.P. Pinto*

Harvard University

Cambridge, MA 021 38

The chemistry and mineralogy of soils reflects the chemistry of the atmosphere

below which they develop. Today the presence of a cover of land plants can

obscure the signature of a highly oxidizing atmosphere. Prior to the advent

of higher land plants ca. 400 m.y. ago the obscuring effect of a biologic

interface should have been minor. It can be shown that under such conditions

the behavior of ferrous iron during weathering depends on the relationship

between the ratio of the net concentration of oxidants to the concentration

of acids in rainwater, and on the ratio of the oxygen demand to the acid demand for complete weathering of the parent rock. An analysis of the behavior

of iron in some 15 paleosols between 1.0 and 2.9 b.y. in age showed some time

ago that iron was retained, or largely retained, in paleosols developed on

rocks with a low ratio of oxidant demand to acid demand (R value) and was lost

from paleosols with a high R value. The results indicate that between I.I and

2.9 b.y.b.p, the ratio of the net concentration of oxidants to CO2 in rainwater

was less than ca. 1/600 of the present-day value.

Our work during the past year has sought to extend the data base for pal eosols

and to define more precisely the relationship between the composition of paleosols and the chemistry of the atmosphere below which they developed. A field

excursion to Western Australia last summer netted only a single paleosol (or

probable paleosol) from the Peak Hill area. A drill core intersected what seems

to be the base of a weathering horizon developed on serpentinite. This horizon

is highly oxidized. Although our work on this material is not yet complete,

the apparent behavior of the serpentinite during weathering is consistent with

prior expectations based on the analysis of other paleosols of similar age.

This is also true for the chemistry of the Sturgeon River Falls paleosol in

the Upper Peninsula of Michigan, a paleosol that was developed on hydrothermally

altered Keewenawan basalts (age I.I b.y.) and that has been studied in considerable detail during the past year.

The only paleosol which falls outside the established pattern is a paleosol

developed on granite below Dominion Reef sediments (age 2.9 b.y.) in South

Africa. Iron has been lost from this paleosol. It is not clear, however,

whether iron loss occurred during weathering or at a later time. If the loss

of iron occurred during weathering, the oxidation state of the atmosphere was

almost certainly lower 2.9 b.y. ago than 2.4 b.y. ago. We expect to collect

more material from this paleosol horizon during the summer and hope to be able

to settle the matter during the coming year.

Today, 02 is the dominant oxidant in rainwater. During the past year, calculations carried out by J.F. Kasting have shown that H20_ is probably the dominant

oxidant in rainwater falling through an atmosphere containing < 10-2 to 10 -3

P.A.L. of molecular oxygen. These calculations have also shown that reductants

such as formaldehyde can be important constituents of rainwater falling through

Iow-O R atmospheres. Such photochemical products would have reacted with algal

mats _overing Precambrian soils and with the mineral constituents of the soils

themselves. A better understanding of these reactions could be of great importance for relating the observed behavior of iron and related elements to the 02

content of the Precambrian atmosphere.

68
i 4. N 86 - 26 1

COOPERATION OF CATALYSTS AND TEMPLATES

David H. White*, Anastassia Kanavarioti, and Carle Nibley

Chem. Dept., Santa Clara University, Santa Clara, CA 95053

John W. Macklin

Dept. of Chemistry, Univ. of Washington, Seattle, WA 98195

In order to understand how self-reproducing molecules could

have originated on the primitive Earth or extraterrestrial bodies,

it would be useful to find laboratory models of simple molecules

which are able to carry out processes of catalysis and templating.

Furthermore, it may be anticipated that systems in which several

components are acting cooperatively to catalyze each other's

synthesis will have different behavior with respect to natural

selection than those of purely replicating systems. As the major

focus of our work, we are trying to devise laboratory models to

study the influence of short peptide catalysts on template

reactions which produce oligonucleotides or additional peptides.

Such catalysts could have been the earliest protoenzymes of

selective advantage produced by replicating oligonucleotides.

Since this is a complex problem, we are also studying simpler

systems which embody only one aspect at a time, such as peptide

formation with and without a template, peptide catalysis of

nontemplated peptide synthesis, and model reactions for

replication of the type pioneered by Orgel.

Three areas of recent progress will be emphasized: (i) In

order to develop a model for primitive translation, we studied

the reaction of amino acids to form peptides on dried clays with

polyribonucleotides added, and found a large yield increase

specifically with ribo- but not deoxyribo- polynucleotides.

Recent progress with FTIR spectra and direct trapping experiments

have demonstrated the presence of acyl ribonucleotide esters

between pyroglutamic acid and poly (G). Furthermore, covalent

adducts between amino acids and polyribonucleotides could

conceivably produce a kind of crude templated peptide formation,

and we are directing future efforts toward this goal. (2) We

have collaborated with Orgel to find whether short peptides

catalyze the template-directed synthesis of oligonucleotides.

Although that search was only marginally successful, one offshoot

has been a new reaction system developed to provide mechanistic

insight into oligonucleotide templating. RNA primers of defined

structure have been studied kinetically to ascertain specific

rates of each step in the template-directed elongation sequence.

(3) Computer modeling has provided new insight into the behavior

of small groups of molecules capable of very crude processes of

replication, translation, and catalysis. Natural selection would

enforce their cooperation to the extent that a "selfish gene'

would actually gain an advantage by slowing down and allowing its

partners to catch up rather than racing ahead. Thus mutual

catalysis leads to molecular cooperation and the first glimmer of

a stable genome, which would not be the case with a purely

replicating system.

69 C" 2>
N86-26872

Molecular Microenvi ronments :

Solvent Interactions with Nucleic Acid Bases and Ions

R.D. MacElroy* Life Sciences Division, NASA Ames Research Center

A. Pohorille, Chemistry Dept. University of California, Berkeley

The possibility of reconstructing plausible sequences of events

in prebiotic molecular evolution is limited by the lack of fossil

remains. However, with hindsight, one goal of molecular

evolution was obvious: the development of molecular systems that

became constituents of living systems. By understanding the

interactions among molecules that are likely to have been present

in the prebiotic environment, and that could have served as

components in protobiotic molecular systems, plausible

evolutionary sequences can be suggested. When "stable"

aggregations of molecules form, a net decrease in free energy is

observed in the system. Such changes occur when solvent

molecules interact among themselves, as well as when they

interact with organic species. A significant decrease in free

energy, in systems of solvent and organic molecules, is due to

entropy changes in the solvent. Entropy-driven interactions

played a major role in the organization of prebiotic systems, and

understanding the energetics of them is essential to

understanding molecular evolution.

Monte Carlo simulation has been used to explore the interactions

and structure of solvent molecules in the vicinity of some simple

biomolecules, nucleic acid bases, and around ions. One of the

striking results of these computer experiments is that the bases

significantly alter the structure of solvents, resulting in a

profound change in both enthalpy and entropy. A second

observation is that hydrogen bonded bases (Watson-Crick pairs),

which form readily in the absence of a solvent (vacuum), or in

the presence of apolar solvents (e.g. carbon tetrachloride),

were found to be energetically less stable in water than stacked

bases. Such data indicate that, in aqueous solution, bases are

more stable when stacked above one another, rather than when

forming hydrogen bonded pairs. Understanding the behavior of

such small systems will allow descriptions of the energetics and

dynamics of larger systems.

These data, and data on the formation of ion-solvent complexes,

raise fundamental questions about the energetics of the formation

of self replicating systems based on nucleic acid interactions.

Similarly interesting questions are raised about possible early

translation systems and about the role of surfaces. It is clear

that a systems view must be adopted when using the energetics and

dynamics of molecules to predict molecular behavior, but that

such an approach is valid, and is likely to prove fruitful in

understanding molecular evolution.

70
.... Nt 6 -,26873

Intramoiecuia_ _nte_a_ions in Aminoacyl Nucleotides: Implications Regarding the

Origin of Genetic Coding and Protein Synthesis

J. C. Lacey, Jr.*, D. W. Mullins, Jr., C. L. Watkins, and L. M. Hall

Department of Biochemistry, University of Alabama in Birmingham, Birmingham,

Alabama 35294

All contemporary cellular organisms store information as sequences of

nucleotides in double stranded DNA. This information is quite useless unless it

can be converted into the active molecular species, protein. How this is done

in contemporary creatures involves first transcription of one strand to give a

complementary strand of mRNA. By a very complex process, the sequence of

nucleotides is then translated into a specific sequence of amino acids in a protein. Translation is made possible by a genetic coding system in which a

sequence of three nucleotides codes for a specific amino acid. Our problem is

to explain how, given four nucleotides for coding and the twenty amino acids for

making proteins, the coding system and the process of protein synthesis arose.

Our guiding principle has been that the origin and evolution of any chemical

system can be understood through elucidation of the properties of the chemical

entities which make up the system. There is an underlyin_ logic to the coding

system revealed by a correlation of the hydrophobicities of amino acids and

their anticodonic nucleotides (i.e. the complement of the codon). This and

other work has suggested that the origin of the code might have been a problem

of the origin of active sites in which amino acids and their anticodons could be

partitioned. Other studies have concentrated on reactions of active acyl compounds relevant to the synthesis of the peptide bond. One compound of great

importance in protein synthesis is the aminoacyl adenylate. Its importance lies

in the fact that every amino acid going into protein synthesis must first be

activated. This is universally accomplished with ATP, resulting in the formation of the energy rich aminoacyl adenylate. Past studies have concentrated

on the chemistry of the adenylates, but more recently we have found, through the

use of NMR, that we can observe intramolecular interactions even at low concentrations, between amino acid side chains and nucleotide base rings in these

adenylates. The use of this type of compound thus affords a novel way of elucidating the manner in which amino acids and nucleotides interact with each other.

In aqueous solution, when a hydrophobic amino acid is attached to the most

hydrophobic nucleotide, AMP, a hydrophobic interaction takes place between the

amino acid side chain and the adenine ring. The studies to be reported concern

these hydrophobic interactions.

The adenylates can be easily purified by high pressure liquid chromatography and then lyophilized and dissolved in D20 for the proton magnetic resonance studies. We have made the following observations from these studies:

i. In a series of hydrophobic aminoacyl adenylates (Phe, Leu, Val and Ile),

NMR shows that, even at low pH where the adenine ring is protonated, all of

these side chains participate in hydrophobic interactions with the "face" of the

adenine ring. The importance of this finding is that it shows not only that

aromatic side chains may intercalate with adenine residues, but aliphatic side

chains as well. The strength of the association varies (Phe > Leu = Ile > Val).

2. If an N-acetyl amino acid is used, it racemizes during synthesis of the

adenylate. Again, using HPLC, we have separated the two diastereoisomers and

found that in one the Phe ring was associated more strongly with the adenine.

We established enzymatically that it is the biologically important L isomer.

3. Using a series of carboxylic acid anhydrides, we found that the longer

chains associate more strongly with adenine and, furthermore, that the propionyl

chain is the smallest which can associate with the planar "face" of adenine

in these compounds. These studies continue to support an active site model for

the origin of the code and protein synthesis.

71
 8 ' 6874

, MOLECULAR REPLICATION

Leslie E. Orgel*

The Salk Institute for Biological Studies

San Diego, California 92138

The object of our research program is to understand how polynucleotide replication originated on the primitive earth. We

believe this to be a central issue in studies of the origins

of life since a process similar to modern DNA and RNA synthesis is likely to have formed the basis for the most primitive

system of genetic information transfer.

The major conclusion of our studies so far is that a preformed polynucleotide template under many different experimental

conditions will facilitate the synthesis of a new oligonucleotide with a sequence complementary to that of the template. We have, for example, shown that poly(C) facilitates

the synthesis of long oligo(G)s and that the short template

CCGCC facilitates the synthesis of its complement GGCGG.

Very recently we have shown that template-directed synthesis

is not limited to the standard oligonucleotide substrates.

Nucleic acld-llke molecules with a pyrophosphate group replacing the phosphate of the standard nucleic acid backbone

are readily synthesized from deoxynucleotide 3'-5'-diphosphates on appropriate templates.

Most of our recent work has used 2-MeImpG and the corresponding derivatives of the other bases as substrates. We have

shown that:

(I) Synthesis of complementary oligomers is efficient

provided the template is rich in C.

(2) Ollgomers as

templates.

short as a pentamer are efficient

(3) Synthesis proceeds in the 5'->3' direction.

(4) The fidelity is high - wrong bases are discriminated

from correct bases by at least a factor of 200.

(5) The incorporation reaction is enantiomerically specific, but is inhibited by the wrong enantiomer.

72
N86-26875

STEREOSELECTIVE AMINOACYLATION OF RNA

D. A. Usher_ M. C. Needels and T. Brenner

Department of Chemistry

Cornell University

Ithaca, N. Y. 14853

Prebiotic chemistry is faced with a major problem: how could

a controlled and selective reaction occur, when there is present in

the same solution a large number of alternative possible

coreactants? This problem is solved in the modern cell by the

presence of enzymes, which are not only highly efficient and

controllable catalysts, but which also can impose on their

substrates a precise structural requirement. However, enzymes are

the result of billions of years of evolution, and we cannot invoke

them as prebiotic catalysts. One approach to solving this problem

in the prebiotic context is to make use of template-directed

reactions. These reactions increase the number of structural

requirements that must be simultaneously present in a molecule for

it to be able to react, and thereby increase the selectivity of the

reaction. They also can give a large increase in the rate of a

reaction, if the template constrains two potential coreactants to

lie close together. A third benefit is that information that is

present in the template molecule can be passed on to the product

molecules.

If the earliest organisms were based on proteins and nucleic

acids, then the investigation of peptide synthesis on an

oligonucleotide template is highly relevant to the study of the

origin of life. This template-directed synthesis could be

remarkably efficient, both in its rate of reaction, and in its

ability to discriminate correct from incorrect partners to a

reaction. It also could suggest a mechanism for the origin of the

genetic code. For the past few years we have been studying a

number of possible "working models" for template-directed peptide

bond formation. During this work we found that aminoacylation of

the "internal" 2'-hydroxyl groups of RNA with the imidazolide of an

alpha-amino acid was chirally selective. This is the first

example of stereoselection in non-enzymic aminoacylation of RNA,

and we have begun investigating in a systematic way the structural

requirements for this chiral selection. We have shown that the

degree and direction of chiral selectivity depends on the presence

or absence of an N-protecting group on the amino acid, and the bulk

or hydrophobicity of the side chain, and we are now studying the

effect of the leaving group and the structure of the RNA.

"Internal" 2'-aminoacyl esters of D,D-3',5'-adenylyl-adenosine

(ApA) can be used as models of the transition state for the

aminoacylation reaction, and we have studied their proton nuclear

magnetic resonance (nmr) spectra to try to understand the basis for

the stereoselectivity. The resonance of the alpha-methyl group of

D-AIa-D,D-ApA is upfield, and that of L-AIa-D,D-ApA is downfield,

with respect to the resonance of the alpha-methyl group of alanine

methyl ester. These results suggest that the alpha-methyl group

of the D-AIa-D,D-ApA ester is more shielded by the aromatic rings

than is the case for the _-Ala ester.

73
.:

MODELS OF GLYCOLYSIS: GLYCERALDEHYDE AS A SOURCE OF ENERGY

AND MONOMERS FOR PREBIOTIC CONDENSATION REACTIONS

Arthur L. Weber*

The Salk Institute

San Diego, California 92138

All organisms require energy in a chemical form for maintenance and growth.

In contemporary life this chemical energy is obtained by the synthesis of

the phosphoanhydride bonds of ATP. Among the biological processes that yield

ATP, fermentation is generally considered primitive, because it operates

under anaerobic conditions by substrate-level phosphorylation which does not

require compartmentation by membranes. Fermentation by the glycolytic

pathway, which is found in almost every living cell, is an especially attractive energy source for primitive life. Glycolysis not only produces

useful chemical energy (ATP), but intermediates of this pathway are also involved in amino acid synthesis and photosynthetic carbon-fixation. It is our

belief that energy and substrates needed for the origin of life were provided by nonenzymatic chemical reactions that resemble the enzyme-mediated

reactions of glycolysis. These nonenzymatic reactions would have provided

a starting point for the evolutionary development of glycolysis.

Our efforts to model glycolysis have stressed the initial energy-yielding

reactions of this pathway. Since these early reactions of glycolysis involve the oxidation of glyceraldehyde-S-phosphate to give initially an

'energy-rich' thioester that is used to drive the synthesis of the phosphoanhydride bonds of ATP, we have studied similar nonenzymatic oxidation and

rearrangement reactions of glyceraldehyde that yield 'energy-rich' thioesters, and have examined condensation reactions that use thioesters as an

energy source in the synthesis of phosphoanhydrides and polyglyceric acid.

We have demonstrated the formation of lactoyl thioester by the rearrangement

of glyceraldehyde in the presence of a thiol under anaerobic conditions.

In the presence of ammonia this anaerobic reaction also yields alanine, presumably via alanyl thioester. When oxygen is present, this model reaction

yields both lactoyl thioester and glyceroyl thioester. We have also shown

that thioesters can be used to drive the synthesis of phosphoanhydrides,

such as pyrophosphate, tripolyphosphate and phosphorylimidazole. Recently,

we have been studying the ability of thioesters to drive phosphorylation reactions via a cyclic phosphorimidazolide intermediate, and the autocondensation of glyeeroyl thioester to give polyglyceric acid. The autocondensation of glyceroyl thioester would have allowed the direct use of thioester

energy in early polymer synthesis, rather than using its energy to synthesize phosphoanhydrides which are then used to drive polymer synthesis as in

contemporary life. We are currently examining the synthesis and properties

of polyglyceric acid, since it appears to be a good candidate for the earliest self-replicatlng and catalytic macromolecule. Presumably, its information content would have been in its sequence of D- and L-glyceric acid residues, and its catalytic ability derived from the acld-base behavior of its

hydroxyl groups and bound metal ions.

74
N86-26877

A COMPARATIVE STUDY OF PREBIOTIC AND PRESENT DAY TRANSLATIONAL _IODELS

R. Rein*. G. Raghunathan, J. McDonald, M. Shibata, and

Unit of Theoretical Biology

Roswe11 Park Memorial Institute

Buffalo, New York 14263

S. Srinivasan

It is generally recognized that the understanding of the molecular

basis of primitive translation is a fundamental step in developing a

theory of the origin of life. However, eve_ in modern molecular

biology, the mechanism for the decoding of messenger RNA triplet codons

into an amino acid sequence of a protein on the ribosome is understood

incompletely. Most of the proposed models for prebiotic translation

lack, not only experimental supvort, but also a careful theoretical

scrutiny of their compatibility with well understood stereochemical and

energetic principles of nucleic acid structure, molecular recognition

principles, and the chemistry of peptide bond formation.

Our studies are concerned with comparative structural modelling and

mechanistic simulation of the decoding apparatus ranging from those

proposed for prebiotic conditions to the ones involved in modern

biology. Any primitive decoding machinery based on nucleic acids and

proteins, and most likely the modern day system, has to satisfy certain

geometrical constraints. The charged amino acyl and the peptidyl

termini of successive adaptors have to be adjacent in space in order to

satisfy the stereochemical requirements for amide bond formation.

Simultaneously, the same adaptors have to recognize successive codons

on the messenger. This translational complex has to be realized by

components that obey nucleic acid conformational principles,

stabilities, and specificities. This generalized condition greatly

restricts the number of acceptable adaptor structures.

Making use of the above criteria, refined models of various previously

proposed prebiotic decoding apparatus are examined for consistency using

distance geometry and energy based stability analysis on one side, and

our newly developed Evans and Sutherland PS 300 system modelling program

on the other.

In consideration of the present day translational system, the apparatus

is reconstructed by making use of available tRNA crystallographic data,

as well as distance constraints extracted from literature on

fluorescence energy transfer, cross-linking, and other experiments.

Using the above described methodology to integrate Obese data, we may

obtain the possible spatial configurations of the complex. The

stereochemical feasibility of the models are examined by computer model

building. The presentation will examine the prebiotic models in the

context of their potential functional similarity and stereochemical

relatedness to present day systems.

75
i.: , N86 - 26878 i

Protobiological Information 1 /,

Bidirectional Recognition, and

Reverse Translation

Sidney W. Fox*, Tadayoshi Nakashima,

Aleksander Przybylski and Graham Vaughan

Institute for Molecular and

Cellular Evolution, university of

Miami, Coral Gables, FL 33134

Emergence of protobiological information has been suggested

by experiments in which heated mixtures of e-amino acids order

themselves into a self limited array of thermal proteins. The

polymers display selective catalytic, hormonal, and other

activities. Interactions of varied cationic thermal proteins

with polynucleotides indicate selective recognition in both

directions. Reverse translation is partly a missing link in the

molecular evolution flowsheet. Interest in reverse translation

(Fox and Dose, 1972) has been increasing (Root-Bernstein, 1982;

Wassermann, 1982; Prusiner, 1982; Melius, 1983; Berger, 1984;

Brunori and Talbot, 1985).

Some selectivity has been observed in the catalysis of

polymerization of 5'-phosphorimidazolides of various nucleosides

(Orgel et al.) in the presence of thermal heteropolypeptides.

Added Leuchs homopolypeptides have no measurable effect, except

for homopolylysine, which is deceleratory. When thermal

heteropolypeptides are added to the reaction, selective effects

are observed. The patterns for cytosine and adenine

phosphorimidazolides are common as are the patterns of effect of

thermal copolyamino acids on uracil and guanine imidazolides.

The deceleration by lysine-rich polymers contrasts to the

acceleration earlier observed with the same polymers acting on

nucleoside triphosphates instead of nucleoside

phosphorimidazolides. The self _rderingof amino acids serves

conceptually as a deterministic evolutionary precursor of the

modern coding mechanism.

The possibility for the evolution of information at an early

nontemplated protein stage is supported by findings of electrical

signals from proteinoid microspheres prepared with no DNA/RNA in

their history. The deposition of thermal copolyamino acids on

lipid membranes in the Mueller-Rudin apparatus has here been

found to produce electrical behavior like that evoked by

bacterial EIM polypeptide. A new procedure is to make a film of

membrane on the electrode; the results provide maximal

repeatability.

The principle of nonrandom biomacromolecular specificity

identified by these studies in molecular evolution have been

extrapolated to principles of evolution of advanced organisms (Ho

and Saunders: Beyond Neo-Darwinism, An Introduction to

the - ' - --_ ....

New Evolutlonary Paradlgm, (Academlc Press, London,

1984).

_/ Information is here operationally defined as capacity

for selective interaction of molecule or system.

76
Q

Photochemical Reactions of Various Model Protocell Systems

Clair E. Folsome*

Exobiology Laboratory

Department o÷ Microbiology

University of Hawaii

Honolulu_ Hawaii 96822

Models abound for the emergence of cellular life on the primitive

earth_ and for physical environments of that era. That model set

which we are studying embodies these assumptions: (1) Pregenetic cellular forms were phase-bounded systems primarily

photosynthetic in nature_ and (2) the early earth environment was

ano×ic (lacking appreciable amounts of free hydrogen).

We had previously shown that model protocells prepared by

quenched spark discharge reactions upon N2_ CO_ H2 gases over

water can conduct photochemical reductions of carbonate to

organic carbon under ano×ic conditions (Nature 291_ 482s 1981).

However_ several serious questions remain as to the plausibility

of this particular model system because reducing conditions were

used initially to prepare the structures.

We have found that organic structures can also be formed under

ano×ic conditions (N2_ C03=_ H20) by protracted longwavelength UV

radiation. Apparently these structures form initially as organic

layers upon CaC03 crystalloids.

The question remains as to whether the UV photosynthetic ability

of such phase bounded structures is a curiosity_ or a general

property of phase bounded systems which is of direct interest to

the emergence of cellular life.

We have addressed the question of the requirement and salient

features of a phase boundary for UV photosynthetic abilities by

searching for similar general physical properties which might be

manifest in a variety of other simple protocell-like structures.

Since we have shown that our laboratory protocell models (either

those prepared under slightly reducing or under ano×ic

conditions) can effect the UV photosynthesis of low molecular

weight compounds_ we are using this reaction as an assay to

survey other types of structures for similar UV photosynthetic

reactions. Various kinds of structures surveyed are: (1)

proteinoids_ (2) liposomes9 (3) reconstituted cell membrane

spheroids_ (4) coacervates, (5) model protocells formed undeP

anoxic conditions.

The conclusion which emerges is that phase bounded systems can

serve effectively (perhaps by developing appropriate transmembrane potentials_ see Tien_ J. Phys. Chem._ 88_ 3172-74_ 1984)

to reduce o×idized carbon to organic carbon in a world subjected

to long-wavelength UV light and supplied with very simple

precursors as carbon in the plus-4 (oxidized) state.

77
: ' ' :":"-" N86 - 96 SSO,

THE PRINCIPLE OF COOPERATION AND LIFE'S ORIGIN AND EVOLUTION

J. Oro*, GII Armangue, Arnulfo Mar

University of Houston

Houston, Texas 7700q

In simple terms a living entity is a negentropic system that replicates, mutates and evolves. A number of suggestions have been made recently, such as directed panspermia, atmospheric photosynthesis, genetic

overtaking from inorganic processes, etc., as alternative models to the

accepted Oparin-Haldane-Urey model of the origin of life on Earth. This

has probably occurred because in spite of tremendous advances in the prebiotic synthesis of biochemical compounds, the fundamental problem of the

appearance of the first life--a primordial replicating cell-ancestral to

all other forms of extant life, has remained elusive. This is indeed a

reflection on the different fundamental nature of the problem involved.

Regardless of which were the fundamental processes which occurred on the

primitive Earth, it had to end up with the fundamental characteristics of

an ancestral protocell. The problem of the emergence of the first ancestral cell was one of synergistic macromolecular cooperation, as it has been

discussed by authors recently (COSPAR XXV Plenary Meeting). An analogous

situation must have occurred at the time of the appearance of the first

eucaryotic organism. Procaryotic life appeared probably during the first

600 million years of Earth history when the Earth was sufficiently cool and

continually bombarded (in the late accretion period) by comets and minor

bodies of the solar system, when the sea had not yet acquired its present

form.

The first organisms on Earth depended initially on the available

organic matter. At any rate they were living in an anaerobic Earth. When

the first energy crisis took place, probable solutions to the problem were:

a) the archaebacterial fixation of COA; b) the non-photosynthetic fixation

of CO 2 by means of such reducing agents as H2S, produced ubiquitously from

the Earth's interior (this could also be a model for the satellite of Juplter, Europa). Later on, with the invention of chlorophyllc photosynthesis

other modes of CO fixation and photoconversion processes were introduced.

At any rate, abou_ 2,000 million years ago biological evolution had come to

a standstill, since the Earth had been populated during 2 billion years of

history only by procaryotlc unicellular organisms. Another quantum jump

was necessary to lead to eucaryotes and eventually to higher organisms.

This required another major discovery, which is the use of H20, instead of

H2S, as a reducing agent by photosynthetic procaryotes. Apparently this

was not a minor feat because today we do not yet know the exact mechanisms

of this reaction. But at any rate when 0 became prevalent (10% of PAL)

the energy-yieldlng processes (oxidative 2hosphorylatlon) speeded evolution

in a tremendous manner. After several unsuccessful trials this oxygenic

environment became prevalent 2 x 10" years ago. This in turn led to the

appearance of aerobic free-llving bacteria, which together with other

procaryotes, gave rise to slngle-cell eucaryotes by endosymbiotlc processes

at about 1,400 million years ago. From here the takeoff toward higher organisms could have been expected. In conclusion, synergistic cooperative

processes were necessary for the emergence of the first single-celled procaryotes and similar processes became also necessary for the appearance of

the first slngle-celled eurcaryote. Therefore there is a need for studies

that can elucidate the early cooperative processes among macromolecules

which interacted to generate by synergistic cooperation all of the essential attributes of the ancestral cell. Obviously this approach is not the

one we have used so successfully in the past going from A to B in the

prebiotic synthesis of biochemical compounds.

78
N86-26881

BASE PARRING KND BASE KI_S-PAIRIN6 IN NU(LEIC ACIDS

Andrew H.-J. Wang*and Alexander Rich

Department of Biology

Massachusetts Institute of Technology

Cambridge, MA 02139

In recent years we have learned that I)NA is conformationally active. It

can exist in a nmnbe_ of different stable conformations including both

right-handed and left-handed forms. Using single crystal X-ray diffraction

analysis we are able to discover not only additional conformations of the

nucleic acids but also different types of hydrogen bonded base-base

interactions. Although Watson-Crick base pairings are the predominant type of

interaction in double helical DNA, they are not the only types. Recently, we

have been able to examine mismatching of guanine-thymine base pairs in

left-handed Z-DNA at atomic resolution (lg). A minimum amount of distortion

of the sugar phosphate backbone is found in the G'T pairing in which the bases

are held together by two hydrogen bonds in the 'Wwobble pairing w_ interaction.

Because of the high resolution of the analysis we can visualize water

molecules which fill in to_c_mmodate the other hydrogen bonding positions in

the bases which are not used in the base-base interactions.

Studies on other DNA oligomers have revealed that other types of

non-Watson-Crick hydrogen bonding interactions can occur. In the structure of

a DNA octamer with the sequence d(GC_TA(I_C) complexed to an antibiotic

triostin A, it was found that the two central AT base pairs are held together

by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G'C base

pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. The

cytosines have to be protunated. Hoogsteen base pairs make a modified helix

which is distinct from the Watson-Crick double helix. The relative ease with

which modifications of hydrogen bonding in the double helix can be found in

crystal lattices provides a basis fo_ wondering what contribution they may

have played in prebiotic evolution.

79
Session V

Early Evolution of Life--Geochemical

8O
N86-26882

CARBON EXCHANGE BETWEEN THE MANTLE AND THE CRUST, AND ITS EFFECT

UPON THE ATMOSPHERE: TODAY COMPARED TO ARCHEAN TIME

David J. Des Marais*

NASA - Ames Research Center

Moffett Field, California 94035

Paleobiologists now recognize that the earth's biosphere has been

profoundly affected by geologic processes. One very important process

is the dissipation of heat which has been generated by radioactivity

and/or stored within the earth. Heat flow is responsible for crustal

movements and therefore it is the principal architect for constructing

the environments (e.g. shallow marine, continental, etc.) wherein life

developed and flourished. Heat flow has also influenced the movements

of volatile elements (e.g. C, N, H, S, rare gases, etc.) both within

the earth's crust and between the crust and mantle. The inventory of

these elements in theearth's crust is important, not just because some

of them constitute the building blocks of organic matter, but also

because they influence the biosphere's climate.

The purpose of this work is to evaluate how the decline of heat flow

over the course of the earth's history has influenced the carbon

inventory in the earth's crust. Such an evaluation must first consider

whether the rate at which carbon is presently being exchanged between

the mantle and crust is sufficient to play an important role in

controlling the crustal inventory. Secondly, this exchange of carbon

must be reevaluated in the context of the Precambrian Earth's

environment. One very important consideration is that the upper mantle

was perhaps 300°C hotter 3 b.y. ago than it is today.

Estimates of the midocean ridge mantle carbon flux can be made by

estimating concentration ratios of carbon to helium in hydrothermal

fluids and tholeiitic glasses and by multiplying these by the oceanic

primordial 3He flux. The estimated ranges of carbon fluxes for the

earth today and 3 b.v. ago are Ixl012 to 8x1012 moles yr -I and 3x1012

to 48xi012 moles yr -_I, respectively. These fluxes are comparable in

magnitude to the present-day flux estimated for carbonate metamorphism,

6xl_ 12 moles yr -I. A net carbon flux from the mantle of 5x1012 moles

r-"

y would require less than 1400 m.y. to generate the present-day

crustal carbon inventory. Given present-day geothermal gradients,

carbonate sediments can be at least partly subducted into the mantle.

Perhaps between 3 and 50 percent of the sedimentary carbon presently

transported by the lithospheric plates to subduction zones will

eventually be injected into the upper mantle. A hotter upper mantle 3

b.y. ago would have made this injection process less efficient. During

the late Archean, the earth's crustal carbon inventory very likely

equalled or even exceeded the present crustal inventory. This

circumstance, together with the likelihood that the land area at that

time was considerably less than it is today, suggests that 3 b.y. ago

the atmosphere contained at least two orders of magnitude more CO 2

than it does today.

81
N86-2688 3

EARTH'S EARLY ATMOSPHERE AS SEEN FROM CARBON AND NITROGEN

ISOTOPIC ANALYSIS OF ARCHEAN SEDIMENTS

Everett K. Gibson_ Jr. and

SN4, Experimental Planetology

NASA Johnson Space Center

Houston, Texas 77058

L.P. Carr, I. Gilmour and C.T. Pillinger

Department of Earth Sciences

The Open University

Milton Keynes MK7 6AA, England

The origin and evolution of the Earth's early atmosphere has long been

a topic of great interest but determination of actual compositions over geologic time is a difficult problem. However, recent systematic studies of

stromatolite deposits (Precambrian Paleobiology Research Group) has extended

our knowledge of Archean ecosystems. It has been shown that many stromatolite

deposits have undergone negligible alteration since their time of formation.

The discovery of primary fluid inclusions within unaltered 3.5 b.y. old Archean sediments and the observation that the 3.3 b.y. old Barberton cherts have

remained closed to argon loss and have not been subjected to thermal metamorphism suggests that an opportunity exists for the direct measurement of

the volatile constituents present at their time of formation. Of primary

interest to our study was the possibility that the stromatolites and other

Archean sediments might retain a vestige of the atmosphere and thus afford

an indication of the variations in carbon dioxide and nitrogen isotopic

compositions with time.

A suite of essentially unaltered Archean stromatolites and cherts of

different ages and geologic sites have been analyzed for their trapped carbon

dioxide and nitrogen compositions by the stepped combustion extraction technique utilizing static mass spectrometers for the isotope measurements.

Studies of modern-day sediments have shown that both nitrogen and carbon associated with unmetamorphosed organic matter is released in the 300-700°C interval

during combustion..Release of carbon from carbonates and graphite is completed prior to 900°C. It has been shown from pyrolysis studies of Archean

cherts that modern-day atmospheric argon is lost below 900 to lO00°C and the

argon released above this temperature interval represents samples of trapped

early atmospheric araon. We have assumed that the carbon dioxide and nitrogen released above 900°C represents gases trapped during the formation of

the sediments and may be a remnant of atmospheric gases during Archean times.

Isotopic analysis of nitrogen released at elevated temperatures from

samples ranging in age from "1.7 to 3.5 b.y. (Frere, Hamersley, and Barberton

Formations) ranged from +6 to +I %o, similar to modern-day atmospheric nitrogen value of 0 %o. The nitrogen released from the Archean sediments occurs

in at least three forms of different isotopic compositions, ranging from -30

to +18 %,. Carbon dioxide released above 900°C for six sediments (Frere,

Hamersley, Manjeri, Cheshire, Barberton and Isua Formations) ranged from -7 to

-14 %o and the majority of the values were similar to the present day atmospheric value of -8 %o. At lower temperatures carbon isotopic compositions

ranging from -7 to -56 %o were observed. The -56 %o value was obtained from

the analysis of kerogen extracted from Fortescue Formation. Evidence exists

which suggests that many of the samples contain "secondary" carbon and nitrogen

of a post-depositional origin in addition to the trapped atmospheric components

and indigenous organic material incorporated at the time the sediments were

consolidated.

82
L N 86-2,6 884 i

USE OF LABORATORY SIMULATED PYROLYSIS IN TRACING

THE HISTORY OF SEDIMENTARY ORGANIC MATTER

I.R. Kaplan*, E. Tannenbaum and B.E. Huizinga

Institute of Geophysics and Planetary Physics

Los Angeles, California 90024

In order to obtain maximum preservation of the organic record, it

is desirable for the preserved biological and chemical fossils to

alter at a slow rate or not to alter at all. It is generally

believed that preservation is mostly a function of shallow burial

depth in rocks with low porosity which prevent water circulation.

At greater depths, it is generally assumed thermal processes

decompose the kerogen. Results from laboratory simulated

pyrolyses experiments performed at UCLA show that in addition to

depth of burial, preservation of kerogen, and hence any

morphologic structure in it, is also dependent on the mineral

matrix with which it is associated. In the presence of clay

minerals, and especially under dry conditions, extractable lipids

released during kerogen decomposition are more rapidly destroyed

than in the presence of calcite or chert matrices. The result is

production of gas, polar bitumen (resins and asphaltenes) and

pyrobitumen (or charred organic matter) and destruction of

biomarkers. During such an early reorganization of the kerogen,

the biomarker constituents can be destroyed, or unrecognizably

altered.

The above process of organic residues maturation appears to be

inhibited in the presence of water and is significantly reduced

where kerogen is hosted in limestones, dolomites or cherts.

These minerals have been characteristically found to be the most

reliable in yielding morphological fossils and small quantities

of extractable bitumen in Archean and Proterozoic rocks. Shales

may contain enrichments of carbon but these usually have low H/C

ratios and questionable amounts of extractable bitumen.

To understand the validity of chemical and morphological fossils,

in the early geologic record, it will be necessary to understand

the process of kerogen in sedimentary rocks.

To test the role of various minerals on the preservation process,

kerogen extracted from a variety of _ocks has been heated

together with montmorillonite, illite and calcite. The kinetics

of the process has been monitored and the products quantitatively

identified. During the coming year, research will be directed

toward continuing the pyrolyses experiments using different types

of kerogen under both dry and aqueous conditions.

83
N86-26885

ISOTOPIC9 PETROLOGIC, AND BIOGEOCHEMICAL INVESTIGATIONS

OF BANDED IRON-FORMATIONS

J. M. Hayes .1, A. J. Kau_man I, C. Klein 2, S_A. Studley 1

M. E. Baur 9 and M. R. Walter

4

1 Biogeochemical Laboratories9 Departments of Chemistry and

of Geology, Indiana University9 Bloomington, Indiana 47405

Department of Geology, University of New Mexico,

Albuquerque9 New Mexico 87131

3

Department of Chemistry, University of California,

Los Angeles, California 90024

Baas Becking Geobiological Laboratory, Bureau of Mineral Resources9

Box 3789 Canberra, A. C. T. 2601, Australia

It is recognized that the first occurrence of BIFs clearly predates biological oxygenation of the atmosphere-hydrosphere system and

that their last occurrences extend beyond plausible dates of pervasive

biological oxygenation. For this reason9 and because enormous quantities of oxidizing power have been sequestered in them9 it is widely

thought that these massive, but enigmatic9 sediments must encode

information about the mechanism and timing of the rise of atmospheric

02 . By coupling isotopic analyses of iron-formation carbonates with

biogeochemical and petrologic investigations9 we are studying (i) the

mechanism of initial sedimentation of iron; (ii) the role of iron in

microbially mediated diagenetic processes in fresh iron-formation sediments; (iii) the logical integration of mechanisms of deposition with

observed levels of banding.

We have, thus far 9 shown that (i) carbonates in BIFs of the

Hamersley Group of Western Australia are isotopically inhomogenous;

(ii) the nature and pattern of isotopic ordering is notl_onsistent

with a metamorphic origin for the overall depletion of 1 C observed in

the carbonates; (iii) if biological 9 the origin of the 3C-depleted

carbonate could be either respiratory or fermentative$ (iv) iron may

have been precipitated as Fe3+9 then reduced to Fe 2+ within the sediment; (v) sedimentary biogeochemical systems may have been at least

partially closed to mass transport of carbonate species; and (vi)

very-closely correlated variations of carbon- and oxygen-isotopic

abundances in the Dales Gorge Members suggest that evaporative processes were important during its deposition.

84
 '8:6 - 8 8,,,11

THE LUNAR NODAL TIDE AND THE DISTANCE TO THE MOON DURING THE

PRECAMBRIAN ERA

James C. G. Walker and Kevin J. Zahnle

The University of Michigan

Ann Arbor, Michigan 48109

The origin and early evolution of life on Earth occurred under physical

and chemical conditions distinctly different from those of the present

day. The broad goal of this research program is to characterize these

conditions. One aspect involves the dynamics of the Earth-moon system,

the distance of the moon from the Earth, and the length of the day.

These have evolved during the course of Earth history as a result of

the dissipation of tidal energy. As the moon has receded the amplitude

of oceanic tides has decreased while the increasing length of the day

should have influenced climate and the circulation of atmosphere and

ocean.

We interpret a 23.3 year periodicity preserved in a 2500 million year

old banded iron-formation as reflecting the climatic influence of the

lunar nodal tide. The corresponding lunar distance would then have

been ~ 52 Earth radii. The influence of the lunar nodal tide is also

apparent in rocks with an age of 680 million years B.P. Our derived

value for lunar distance 2500 million years ago is the only datum on

the dynamics of the Earth-moon system during the Precambrian era of

Earth history. The implied development of Precambrian tidal friction

is in accord with more recent paleontological evidence as well as the

long term stability of the lunar orbit.

85
Session VI

Early Evolution of Llfe--Blologlcal

86
N86-26887 ,

A

RECENT PROGRESS IN PRECAMBRIAN PALEOBIOLOGY

J. William Schopf*, Department of Earth & Space Sciences,

University of California, Los Angeles 90024

Ongoing studies at UCLA supported by NASA Grant NGR 05-007-

407 include the following:

I. Investigations of stromatolites, microfossils and

sedimentary structures in Archean (Warawoona Group, 3.5 Ga)

and Early Proterozoic (Fortescue Group, 2.8 Ga) sequences

of Western Australia; in Archean (Onverwacht Group, 3.5 Ga)

and Early Proterozoic (Transvaal Supergroup, 2;3 Ga) sequences

of eastern and central South Africa; in Early Proterozoic

(Kona Dolomite, Tyler Fm., Pokegama Quartzite, Biwabik and

Gunflint Iron Fms., 2.0 Ga) sequences of North America; and

in Middle Proterozoic (Gaoyuzhuang Fm., 1.4 Ga; Wumishan Fm.,

1.2 Ga) and Late Proterozoic (Jiudingshan Fm., 0.9 Ga;

Wanshan Fm., 0.7 Ga) sequences of northern and south-central

China.

2. Laboratory and field studies of modern microbial

biocoenoses -- analogues of Precambrian microbial communities

-- especially those at Laguna Mormona, Baja California, Mexico.

3. Development of new laboratory techniques for the

separation and concentration of minute cellularly preserved

fossils for isotopic and organic geochemical analyses.

4. Assembly of a computerized database for assessment

of the timing and nature of major events occurring during

Precambrian biotic evolution, and of the potential applicability

of ancient microbiotas to problems of global biostratigraphy

and biogeography.

In addition, during the past year, with support from the

UCLA Center for the Study of Evolution and the Origin of

Life and the National Geographic Society, a consortium of

some three dozen scientists having interest in the interrelated lithospheric-biospheric-atmospheric evolution of

the Proterozoic Earth, has been assembled. This multidisciplinary group -- calling itself the P.P.R.G.-P (Precambrian Paleobiology Research Group-Proterozoic) and

drawing its membership from Canada, Australia, South Africa,

Sweden and the United States -- plans to work together at

UCLA in 1987-88 to produce a major monographic work on

Proterozoic paleobiology. This new venture will intermesh

well with the studies outlined above as part of an ongoing

effort to decipher and better define the nature, mode,

rate and course of biotic, geologic and environmental

evolution during early, Precambrian, Earth history.

87
N86 - 26 888 .

Higher-order Structure of rRNA

R.R. Gutell* and C.R. Woese

University of Illinois

Urbana, IL 61801

A comparative search for phylogenetically covarying

basepair replacements within potential helices has been the

only reliable method to determine the correct secondary

structure of the 3 rRNAs, 5S, 16S, and 23S. The analysis of

16S (and more recently 23S rRNA) from a wide phylogenetic

spectrum, that includes various branches of the eubacteria,

archaebacteria, eucaryotes, in addition to the mitochondria

and chloroplast, is beginning to reveal the constraints on

the secondary structures of these rRNAs. A common secondary

structure for all of these 16S-like rRNAs emerged from this

analysis, and further, comparisons among these revealed a

highly constrained secondary structure core, in addition to

the specific regions that are structurally variable. Within

the conserved secondary structure core exists many universally conserved nucleotides, with the majority of these

clustered into a few regions of the molecule.

Based on the success of this analysis, and the assumption that higher order structure will also be phylogenetically conserved, we have begun a comparative search for

positions that show co-variation not involved in secondary

structure helices. From a list of potential higher order

interactions within 16S rRNA we are presenting two higherorder interactions.

The first of these interactions involves positions 570

and 866. Based on the extent of phylogenetic covariation

between these positions while maintaining Watson-Crick pairing, we consider this higher-order interaction proven. The

other interaction involves a minimum of six positions

between the 1400 and 1500 regions of the 16S rRNA. Although

these patterns of covariation are not as striking as the

570/866 interaction, the fact that they all exist in an

anti-parallel fashion and that experimental methods previously implicated these two regions of the molecule in tRNA

function suggests that these interactions be given serious

consideration.

88

- [,
N86-26889

rRNA EVOLUTION AND PRfXIARYOTIC PHYIDGENY

George E. Fox*

Department of Biochemical Sciences

University of Houston

Houston, TX

Studies of ribosomal RNA primary structure allow reconstruction of

phylogenetic trees for prokaryotic organisms. Such studies reveal

a major dichotomy among the bacteria that separates them into

eubacteria and archaebacteria. Both groupings are further

segmented into several major divisions. The results obtained from

5S rRNA sequences are essentially the same as those obtained with

the 16S rRNA data. In the case of Gram negative bacteria the

_ibosomal RNA sequencing results can also be directly compared

with hybridization studies and cytochrome c sequencing studies.

There is again excellent agreement among the several methods. It

seems likely then that the overall picture of microbial phylogeny

that is emerging from the RNA sequence studies is a good

approximation of the true history of these organisms.

The RNA data allow us to begin to examine the evolutionary

process in a semi-quantitative way. The secondary structures of

these RNAs are largely established. As a result it is possible to

recognize examples of local structural evolution. Evolutionary

pathways accounting for these events can be proposed and their

probability can be assessed.

89
N 86 - 2,6 890

INVESTIGATIONS WITH METHANOBACTERIA AND WITH EVOLUTION OF THE GENETIC CODE

Thomas H. Jukes*

Space Sciences Laboratory

University of California

Berkeley, CA 94720

(I) Evolutionary changes in the genetic code. Mycoplasma capricolum was

found by Osawa et al. to use UGA instead of UGG as the code for tryptophan

and to contain 75% A + T in its DNA. This change could have been from

evolutionary pressure to replace C + G by A + T, resulting in the following

steps; first, replacement of UGA stop codons by UAA. This would prevent UGA

codons from producing chain termination. The second step would be a

mutational change of the anticodon in tryptophan tRNA from CCA (which pairs

only with UGG) to UCA (which pairs with both UGA and UGG). The third step

would be replacement of UGG tryptophan codons by UGA. None of these changes

would be deleterious.

(2) Silent nucleotide substitutions in evolution. Numerous studies have been

reported of evolution of proteins as measured by amino acid replacements that

are observed when homologous proteins, such as hemoglobins from various

vertebrates, are compared. These replacements result from nucleotide substitutions in amino acid codons in the corresponding genes. Simultaneously,

silent nucleotide substitutions take place that can be studied when sequences

of the genes are compared. These silent evolutionary changes take place mostly

in third positions of codons. Two types of nucleotide substitutions are

recognized: pyrimidine-pyrimidine and purine-purine interchanges (transitions)

and pyrimidine-purine interchanges (transversions). Silent transitions are

favored when a corresponding transversion would produce an amino acid

replacement. Conversely, silent transversions are favored by probability when

transitions and transversions will both be silent. Extensive examples of

these situations have been found in protein genes, and it is evident that

transversions in silent positions predominate in "family boxes" in most of

the examples studied.

(3) Lysis of Methanobacteria (work by John Bush). A streptomycete from cow

manure produces an extracellular enzyme capable of lysing the pseudomureincontaining methanogen Methanobacterium formicicum. The lytic activity has

been partially purified from culture fluid and appears to be a serine protease.

Similar activity has been fractionated from Pronase. Optimal conditions have

been developed for lysis of the bacterium by commercial preparations of

Proteinase K. The three lytic enzymes have been partially characterized.

9O

L_
N,e ,-26egi '

IS THE ATPase FROM HALOBACTERIUM SACCHAROVORUM AN

EVOLUTIONARY RELIC?

Lawrence I. Hochstein *(1) , Wijaya Altekar (2)

and Hordur Kristjansson

Ames Research Center, Mo_tt Field, CA 94035; (i) Bhabha

Research Center, India; --- National Research Council

Post_Doctor_%_Fellow, Ames Research Center, Moffett Field,

CA 94035. "-'

The ATP Synthase Complex present in the membranes of

mitochondria, chloroplasts or bacteria is composed of 2 sectors:

F^, an integral membrane protein consisting of 3 subunits

U

mediating proton translocation across the membrane and F I, the

catalytic component composed of 5 non-identical subunits. The

apparent early origin of the ATP Synthase Complex, as implied by

its ubiquitous distribution, seems inconsistent with its

structural and functional complexity and raises the question if

simpler versions of the ATP Synthase exist. We have searched for

such an ATP Synthase in various Archaebacteria. Here we describe

a purified halobacterial ATPase activity which possesses certain

properties consistent with those of an ATP Synthase but which has

a different subunit structure.

Membranes from H. saccharovorum were treated with detergent so as

to extract the ATPase activity. The soluble enzyme was further

purified by gel filtration, phenyl sepharose chromatography, and

ammonium sulfate_mediated DEAE_chromatography. The final

material hydrolyzed 2.9 umols of ATP/min/mg protein which

represented a 150_fold purification. The purified enzyme was

cold sensitive and was most active and stable in at least 3 M

NaCI and at least 3.5 M NaCI respectively. ATPase activity was

competitively inhibited by ADP indicating that an E.ADP complex

was formed which made unlikely that the hydrolysis of ATP was

catalyzed by an alkaline phosphatase or ion_translocating enzymes

such as a Na/K ATPases. The purified enzyme was inhibited by

DCCD in a manner that resembled the interaction of the inhibitor

with the F I sector. However, only three subunits were detected

by sodium aodecylsulfate polyacrylamide gel electrophoresis. Two

(the major bands) had molecular weights of 85,000 and 60,000; the

third (estimated to represent <10% of the total protein) had a

molecular weight of 28,000. Thus, whether this enzyme is a

different ATP Synthase or another type of ion_translocating

ATPase is not clear. At the present time, studies are underway

to determine the function of this ATPase activity.

t.r

P

91
° N86-26892

FUNCTIONAL AND EVOLUTIONARY RELATIONSHIPS BETWEEN

5ACTERIORHODOPSIN AND HALORHODOPSIN IN THE ARCHAEBACTERIUM,

HALOBACTERIUM HALOBIUM

Janos K. Lanyi*

University of California

Irvine, California 92717

The archaebacteria occupy a unique place in phylogenetic trees

constructed from analyses of sequences from key informational

macromolecules, and their study continues to yield interesting

ideas on the early evolution and divergence of biological

forms. It is now known that the halobacteria among these

species contain various retinal-Proteins , resembling

eukaryotic rhodopsins, but with different functions. Two of

these pigments, located in the cytoplasmic membranes of the

bacteria, are bacteriorhodopsin (a light-driven proton pump)

and halorhodopsin (a light-driven chloride pump). Comparison

of these systems is expected to reveal structure/function

relationships in these simple (primitive?) energy transducing

membrane components and evolutionary relationships which had

produced the structural features which allow the divergent

functions.

Both systems consist of a small intrinsic membrane protein

(opsin), which binds retinal via a protonated Schiff-base

linkage. The retinal undergoes isomerization (trans to 13-

cis) upon absorption of light in both cases, which moves the

Schiff-base to a new environment in the proteins. From here

on, however, the two systems function differently. In

bacteriorhodopsin the isomerization is followed by deprotonation of the Schiff-base nitrogen and release of the

proton into the extracellular medium. Reisomerization of the

retinal occurs only after reprotonation of the Schiff-base

from the cytoplasmic side. In halorhodopsin, however, the

deprotonation does not take place after the isomerization,

thus the spatial displacement of the positively charged

nitrogen will cause instead a rearrangement of charges in the

protein. It is the redistribution of the charges which

presumably caus_ the movement of chloride ions, known to have

bound in the dark to the extracellular side of the protein.

Release of the chloride on the cytoplasmic side ultimately

accompanies the reisomerization of the retinal. It seems

clear that very different primary structures are needed for

these proteins to accomplish their different functions.

Indeed, analysis of partial amino acid sequences from haloopsin shows already that few if any long segments exist which

are homologous to bacterio-opsin. Either these proteins

diverged a very long time ago to allow for the observed

differences, or the evolutionary clock in the halobacteria

runs faster than usual.

92
N86' 26893 ,

THIOREDOXINS IN EVOLUTIONARILY PRIMITIVE ORGANISMS "

Bob B. Buchanan* Division of Molecular Plant Biology,

Hilgard Hall, University of California, Berkeley, CA 94720

Thioredoxins are low molecular weight redox proteins, alternating between the S-S (oxidized) and SH (reduced) states,

that function in a number of biochemical processes, including

DNA synthesis, DNA replication, and enzjnne regulation. Until

recently, reduced ferredoxin was known to serve as the source

of reducing power for the reduction of thioredoxins only in

oxygenic photosynthetic cells. In all other organisms, the _

source of hydrogen (electrons) for thioredoxin reduction was

considered to be NADPH. We found in our NASA-supported research that Clostridium pasteurianum, an anaerobic organism

normally living in the soil unexposed to light, resembles

photosynthetic cells in using ferredoxin for the reduction of

thioredoxin. Moreover, the transfer of electrons from reduced

ferredoxin to thioredoxin is catalyzed by a flavoprotein enzyme that has not been detected in other organisms. The results reveal the existence of a pathway in which ferredoxin,

reduced fermentatively either by molecular hydrogen or by a

carbon substrate, provides the reducing power for the reduction of thioredoxin via the flavoprotein enzyme, ferredoxinthioredoxin reductase.

In related studies, we have found that Chromatium vinosum, an anaerobic photosynthetic purple sulfur bacterium re-

_bles evolutionarily more advanced micro-organisms in having

an NADP-thioredoxin system composed of a single thioredoxin

which is reduced by NADPH via NADP-thioredoxin reductase. The

adoption of the NADP-thioredoxin system by Chromatium seems

appropriate in view of evidence that the organism utilizes

ATP-driven reverse electron transport, rather than direct

photoreduction to reduce electronegative acceptors such as

NAD. Accordingly, because of the more oxidizing redox potential, thioredoxin reduction via NADP would be energetically

less costly than via ferredoxin and would have the added advantage of lying closer to the main photosynthetic electron

transport pathway should there be a need to relate electron

transport status to the extent of thioredoxin reduction as is

the case in oxygenic photosynthesis. Apropos this point, we

have also found that, in contrast to oxygenic photosynthetic

organisms, the role of thioredoxin in anoxygenic prokaryotes

such as Chromatium seems to lie outside the regulation of

photosynthetic CO2 assimilation.

Our most recent NASA-support research has dealt with the

identification of target enzymes of the ferredoxin/thioredoxin

system in a cyanobacterium (Nostoc muscorum). The results

show that thioredoxin-linked pot-h-6T6-syntheticenzymes of cyanobacteria are similar to those of chloroplasts. It thus now

seems that the ferredoxin/thioredoxin system functions in

regulating CO 2 assimilation via the reductive pentose phosphate cycle in oxygenic but not anoxygenic photosynthetic

cells.

93
N86-26894 i

BIOSYNTHETIC PORPHYRINS AND THE ORIGIN OF PHOTOSYNTHESIS

David Mauzerall*, Arthur Ley and Janet A. Mercer-Smith

Rockefeller University Los Alamos National Laboratory

New York, NY Los Alamos, NM

Living matter requires a continuous flux of free energy to remain in its

organized state. Thus the evolution of a photosynthetic system may be intimately associated with the successful evolution of living matter. It is

probable that photochemistry driven by wavelengths around the maximum of

solar energy output is required to support bio-evolution on a terrestrial

scale. The present day photosynthetic system is highly optimized for this

function. It was hypothesized by Granick that the biosynthetic pathway of

photosynthetic pigments recapitulates the evolutionary history of the photosynthetic system. Thus each pigment would have had a photosynthetic function

in its time period, to be replaced by the next along the sequence which

served a more efficient or more useful function. Since the prebiotic atmosphere was anaerobic, if not reducing, a useful function of primordial _oto-)

synthesis would have been to photooxidize reduced substrates such as Fe -, S "

or reduced organic molecules and to emit hydrogen. A major advance occurred

with the discovery of a mechanism for the photoformation of oxygen from the

omnipresent material water. It is the aim of this research to show that the

chemical and photochemical properties of the pigments formed early in the

biosynthetic pathway are consistent with these hypotheses.

We have shown that the early biogenic pigments uroporphyrin and coproporphyrin do photooxidize organic compounds and emit hydrogen in the presence of a

platinum catalyst. These experiments were carried out in dilute aqueous

sol_tion near neutral pH under anaerobic atmosphere, and quantum yields near

I0 were obtained. Thus relevant prebiotic conditions were maintained. Rather

than to further optimize conditions, attempts were made to replace the platinum catalyst by a more "prebiotically"suitable catalyst. Trials with an

Fe4S4(SR) 4 cluster, in analogy to the present hydrogenase and nitrogenase,

were not successful. However, experiments using cobalt complexes to catalyze

the formation of hydrogen are promising. In analogy with biological photosynthetic systems which group pigments, electron transfer molecules and enzymes

in clusters for efficiency, it was found that binding the biogenic porphyrins

to the polyvinyl alcohol used to support the platint_n catalyst did increase

the quantum yield of the reaction. This also made the reaction less dependent

on auxiliary electron transfer molecules. It was also found that ultra violet

light can serve to photo-oxidize porphyrinogens to porphyrins under anaerobic

•conditions. Thus the formation of the colorless porphyrinogens (absorbing

< 250 nm) by the extraordinarily simple biosynthetic pathway would not be a

problem because of the prevalence of UV light in the prebiotic, anoxic atmosphere. We will explore the possible catalytic activity of various cobalt

complexes, including derivatives of vitamin BI) , as hydrogen forming catalysts

under primitive earth conditions. This opens _[n intriguing connection between

the photochemical activity of uroporphyrin, the earliest biogenic porphyrin,

and the biosynthetically fntimately related _itamin BI2.

94
S

OXYGEN AND THE EVOLUTION OF METABOLIC PATHWAYS

Linda L. Jahnke*

Ames Research Center, NASA

Moffett Field, California 94035

N86-2689 i

Life on Earth presumably originated in an essentially

anaerobic environment. At some time, perhaps as much as 9.5

billion years ago, the process of oxygenic photosynthesis was

"invented" and oxygen gradually accumulated in the atmosphere.

While a considerable amount of evidence has been accumulated

about the history of oxygen on this planet, little is known

about the relative amounts to which primitive cells might have

•been exposed. One clue may be found in the metabolic pathways

of extant microorganisms. Biosynthetic pathways appear to

have evolved by sequential steps. The initial enzymatic steps

which are found in all organisms are anaerobic, i.e.

oxygensses are not involved, while subsequent steps reflect

with increasing frequency the use of oxygen as an enzymatic

substrste. From the standpoint of evolutionary development,

particularly eucaryotlc, the emergence of a number of

oxygen-requlring processes was crucial. While eucaryotes are

principally aerobic organisms, a number are capable of

anaerobic growth by fermentation. One such eucaryotic

microorganism, Saccharomyces cerevisiae, will grow in the

complete absence of oxygen when supplemented with unsaturated

fatty acid and sterol. Oxygen-requiring enzymes are involved

in the synthesis of both of these compounds. Studies in our

laboratory have demonstrated that the oxidative desaturatlon

of palmitic acid and the conversion of squalene to sterols

occur in the range of 10-3 to 10-2 PAL. Thus, if the oxygen

requirements of these enzymatic processes are an indication,

eucaryotes might be more primitive than anticipated from the

microfossll record. Recent work has focused on the oxygen

requirements for sterol and unsaturated fatty acid synthesis

in a more primitive procaryotlc system.

The synthesis of sterols or monounsaturated fatty acids by an

oxidative mechanism is not widespread among procaryotic

organisms. A number of bacteria have been shown to use

oxygenases for the synthesis o_ unsaturated fatty acids,

including a number of cyanobacterla and bacilli, however, the

best example of sterol synthesis in s procaryote is found in a

methanotroph, Methylococcus capsulstus. Electron microscopic

studies have shown that methanotrophic organisms contain well

defined systems of intracytoplasmic membranes which increase

when cells are grown at low levels of oxygen. We have

attempted to correlate the observed changes in

intracytoplssmlc membranes in M. capsulatua by studying the

quantitati_variatlons in the levels of membrane llpids,

principally phospholipld, fatty acid and sterol. Preliminary

studies have shown that when cells are grown at lower oxygen

levels, phosphollpld and aterol synthesis increases, and the

fatty acid content changes dramatically. Cells grown at 10-2

PAL oxygen contain high levels of sterols.

95
i< N86 - 26896

EVOLUTION OF THIOL PROTECTIVE SYSTEMS IN PROKARYOTES

Robert C. Fahey and Gerald L. Newton

University of California, San Diego

La Jolla, California 92093

Biological thiols are essential elements in most aspects of cell function but

undergo rapid oxidation to disulfides in the presence of oxygen. The evolution of systems to protect against such oxygen toxicity was essential to the

emergence of aerobic life. The protection system used by eukaryotes is based

upon glutathione (GSH) and GSH-dependent enzymes but many bacteria lack GSH

and apparently use other mechanisms. The objective of this research is to

elaborate the thiol protective mechanisms employed by prokaryotes of widely

divergent evolutionary origin and to understand why GSH became the central

thiol employed in essentially all higher organisms. Thiol-selective fluorescent labeling and HPLC analysis has been used to determine key monothiol

components.

The major thiols present in representative species from all major lines of

prokaryotic evolutionarydescent have been determined. Among the archaebacteria it has been found that the halobacteria (aerobes) produce Y-glutamylcysteine and thiosulfate in large amounts and produce a disulfide reductase

which maintains the 7-Glu-Cys in the reduced state, whereas the methanogens

(strict anaerobes) contain sulfide as the major thiol component and have low

levels of cysteine and coenzyme M. The eubacteria include the Gram positive

bacteria and the radiobacteria whose aerobic and facultative members were

found to produce coenzyme A as the major thiol and to contain one or more

disulfide reductases which reduce CoA disulfide to its thiol. Anaerobic Gram

positive bacteria contained sulfide as the dominant thiol. Several unidentified thiols were detected in specific Gram positive bacteria in substantial

amounts and their structures are being elucidated. Representatives of the

spirochaetes and the green sulfur bacteria were found to have sulfide as the

main thiol component. Glutathione was found to be the dominant thiol only in

facultative and aerobic members of the purple photosynthetic and related bacteria, and in the cyanobacteria. The later finding is significant because

these two groups are considered to have been the precursors to eukaryotic mitochondria and chloroplasts via the process of endosymbiosis, suggesting that

GSH metabolism may have been incorporated into eukaryotes at the same time

that mitochondria and chloroplasts were acquired. Our finding that Entamoeba

histolytica, a eukaryote lacking both mitochondria and chloroplasts, lacks

GSH and GSH-dependent enzymes is consistent with this view. GSH metabolism

thus appears to have its origins closely linked to the evolution of oxygenic

photosynthesis and oxygen-utilizing metabolism. A key factor in the evolution of GSH as a protective thiol appears to be its slow rate of air oxidation relative to Cys, Cys-Gly, and other thiols with free beta amino groups.

96
i 186- 26897

¢,

MICROFOSSILS IN THE ANTARCTIC COLD DESERT -

POSSIBLE IMPLICATIONS FOR MARS

E. Imre Friedmann*

Department of Biological

Science

Florida State University

Tallahassee, FL 32306

Roseli Ocampo-Friedmann

Department of Biology

Florida A & M University

Tallahassee, FL 32307

In the Ross Desert of Antarctica, the principal life form is the

cryptoendolithic microbial community in the surface-near layers

of porous sandstone rocks.

Biological, geological and climatic factors interact in a complex

and precarious balance, making life possible in an otherwise

hostile environment. Once this balance is tipped, fossilization

sets in. In the reverse case, new colonization of the rock

surface may be initiated. As a result, fossilization is

contemporary with modern life and both may be simultaneously

present in a mosaic pattern. Also, different stages of

fossilization are present. The process of fossilization takes

place in a non-aquatic environment.

If primitive life ever appeared on Mars, it is possible that with

increasing aridity, life withdrew into an endolithic niche

similar to that in the Antarctic desert. Fossilization in a

non-aquatic environment may have set in with the result that

traces of past life could be preserved. If such was the case,

the study of the fossilization process in Antarctica may hold

useful information for the analysis of Martian samples for

microfossils.

97
EVOLUTIONARY SIGNIFICANCE OF OSMOREGULATORY MECHANISMS IN CYANOBACTERIA

John H. Yopp,* Kenneth A. Pavlicek and Marion H. Sibley

Southern Illinois University

Carbondale, Illinois 62901

Physiological processes of all life forms on this planet are intrinsically

related to their intracellular water potential. The overall goal

of this research is the elucidation of the mechanism(s) whereby earth's

first oxygenic photoautotrophs (the cyanobacteria) adjust their water

potential to that of a changing external water potential (that is,

osmoregulate). Osmoregulation is achieved by intracellular adjustment

of inorganic and/or organic solutes (osmolytes) involving specific

biochemical mechanisms. Structural and biochemical evolution within

the cyanobacteria is believed to have been completed (and fixed in

present day forms) by the end of the Precambrian eon. Therefore,

research using cyanobacteria of all three structural types (unicellular,

filamentous and branched), each grown in the photoautotrophic (PA),

photoheterotrophic (PH) and chemoheterotrophic (CH) modes of nutrition,

should provide insight into the origin and evolution of the photosyntheticallyrelated osmoregulatory mechanisms of eukaryotic organisms. The chloroplasts

of these organisms are phylogenetical_ related to the cyanobacteria.

13

Studies involving C-NMR and other conventional analytical instrumentation

on osmoregulating organisms have provided substantial information

on cyanobacterial osmoregulation. Non-reducing carbohydrates are

the principal (10-fold greater than amino acids) osmolytes accumulated

during light or dark periods in freshwater and marine cyanobacteria,

grown in all nutritional modes. Glycinebetaine is the major osmolyte

in only the extremely halotolerant species (e.g. Aphanothece halophytica).

Unicellular forms (e.g. Synechocystis ATCC#27178) accumulate glucosylglycerol,

whereas filamentous (e.g. Calothrix ATCC#27914) and branched (e.g.

Chlorosloeopsis ATCC#27181) forms accumulate trehalose in light (sucrose

in dark) when grown in PA mode. Under PH nutrition, sucrose is the

major osmolyte in both light and dark for all three forms. Glutamate,

proline, lysine and arginine accumulate, each depending upon light

and nutritional conditions. These osmolytes have roles other than

osmotic adjustment. Trehalose prevents membrane dessication and _etaine

permits enzymatic function in high intracellular potassium ion (K-)

by lowering the Km of salt inhibited enzymes. Halotolerant cyanobacteria,

like halobacteria, employ K+ in an osmotic role, but the former possesses

enzymes that are inhibited by intracellular salt. Cyanobacteria have,

therefore, evolved an alternative mechanism of salt tolerance by synthesizing

betaine to allow enzymatic functioning in high intracellular salt.

T_e betaine effect varies inversely with a particular enzyme's inherent

K sensitivity. This mechanism of osmoregulation and salt tolerance

through betaine synthesis _as also been elucidated. Osmotically stressed

cyanobacteria accumulate K which inhibits the favored synthesis activity

of S-Adenosylhomocysteine _SAH) hydrolase. The hydrolytic direction

is not inhibited by high K and, therefore, SAH is removed. SAH is

a potent inhibitor of the methylase enzyme required for betaine synthesis.

Betaine then accumulates to a level that permits full activity of

the SAH hydrolase in the favored synthetic direction. SAH then accumulates

and betaine synthesis ceases.

98
• •

N86-26899

MICROBIAL CONTRIBUTIONS TO THE PRECAMBRIAN EARTH

Lynn Margulis

David Bermudes*

and

Robert Obar

Boston University

Boston, Massachusettes

Life has existed on earth for approximately 3.5 billion

years. For most of this time, prokaryotic communities including

those of microbial mats and stromatolites, some of which

preserved as laminated cherts, provided the major biological

forces changing the earth. Many changes in atmospheric gas

composition (for example the depletion of C0 2) occurred during

the Archean and Proterozoic eons as a result of microbial

activity. The study of extant microbial communities has been

used to help understand the dynamics which contributed to these

atmospheric changes.

Our study of microbial mat communities has begun with

characterization of the organismic constituents. Continuing

microbial characterization has led to the establishment of 3 new

prokaryotes: I) a red Beneckea sp., 2) Ar_

_j_ strain BC-2, and 3) _Z_ro/_bajacaliforniensis.

We have recognized symbiosis in microbial communities as

major force in cell evolution. Among the evolutionary enigmas we

are investigating is the problem of the origin of the undulipodia

(cilia, eukaryotic "flagella"). Ondulipodial microtubules are

still deployed for major cellular processes such as mitosis and

meiosis.

bajacaliforniensis may yield clues towards

the origin of tubulin-microtubules in eukaryotic cells. By

immunohistochemistry this spirochete was previously shown to have

antitubulin activity. The immuno-active protein was partially

purified using standard temperature cycling for brain tubulin.

Although two proteins ($1 and S2) co-purify (analogous to alphaand beta-tubulin) only Si is antitubulin immuno-reactive. The S1

protein (67K) has now been isolated by gel filtration and

chromatofocusing. The partial biochemical characterization of S1

protein that has been achieved includes determination of its

isoelectric point (6.3), that polymerization is GTP independent,

and peptide mapping. Several prokaryotes have been tested for

the presence of the Sl-type protein, so far only spirochetes have

been found to possess it. We are seeking Sl in cyanobacteria

reported to contain microtubules.

99
N86-269oo

ORGANIC S13C VALUES VARY SLIGHTLY WITH SALINITY

IN MICROBIAL MATS AT GUERRERO NEGRO, BAJA C_IFORNIA SUR, MEXICO:

IMPLICATIONS FOR STROMATOLITE S_C VALUES

David J • Des Marais* , Etta Peterson, Emil Kwong and Hua Bui

NASA - Ames Research Center

Moffett Field, California 94035

Stromatolites, layered sedimentary rock structures

produced by communities of microorganisms, constitute the

most abundant early evidence of life on earth. Microbial

mats, which are found most frequently in hypersaline

marine or hot spring environments, serve as useful modern

analogs of stromatolitic communities. Our laboratory is

conducting biogeochemical studies of mats to assist our

interpretations of stromatolites.

O{_anic carbon preserved in Precambrian stromatolites has

S_C values typically in the range -19 to -35, whereas

microbial mats growing today in marine hypersaline

envirg_ments have S _C values in the range -6 to -14.

This _C shift has been attributed to selective

preservation of isotopically light organics, a decline in

atmospheric CO 2 levels, or the restriction of microbial

stromatolitic communities to hypersaline environments in

the Phanerozoic due to grazing pressures in lower salinity

environments. The salinity argument requires that the

organic S_C of microbial mats increases with salinity,

perhaps ranging from -20 to -35 in less saline waters

(having 0 to 3.3% salt) to -6 to -14 in hypersaline waters

(3.3 to 20% or more).

Microbial mats inhabit those Guerrero Negro salt works

ponds with salinities between 5.0 and 13.0%. Principal

mat-forming cyanobacteria are Microcoleus and Phormidium

(5 to 7% salinitie_ and Aphanothece (9 to 13%).

Inorganic carbon S_C values range from about +i (4% salt)

to -4.4 (6.6%) to -5.6 (13.6%_. Carbonate alkalinitie_ in

the ponds range from 2.7xi0 -_ moles/L (4%) to 3.6xi0 -_

moles/L (13%). Microcoleus mats' organic 813C values vary

from -12.4 to -14.2 with no clear dependence upon

salinity. Aphanothece mats appear to be 1 to 2 permil

enriched, relative to Microcoleus mats.

The data suggest that salinity effects are insufficient by

themselves to cause the ±_C differences observed between

Precambrian stromatolites and modern microbial mats.

i00
• L

Session VII

Evolution of Advanced Life

i01
N86-26901

THE FOSSIL RECORD OF EVOLUTION: ANALYSIS OF EXTINCTION

David M. Raup

University of Chicago

Chicago, Illinois 60637

There is increasing evidence that events in space have had direct

effects on earth history and on the history of life on earth. Nowhere

is this more evident than in mass extinction. The biosphere has

undergone repeated devastation caused by relatively short-lived

environmental stress, with species kill rates up to 80% (terminal

Cretaceous) and 95% (terminal Permian). For five of the mass extinctions, geochemical or other evidence has been reported suggesting

large body impact as the cause of the environmental stress producing

the extinctions. Furthermore, it has been argued on statistical

grounds that the major extinction events are uniformly periodic

in geological time. If it is true that large body impact is a

principal cause of mass extinctions and if the periodicity is real,

then a cosmic driving mechanism is inescapable. However, much

more geological, geochemical, paleobiological, and astrophysical

work is needed before this hypothesis can be established.

Paleontological datasets have been developed which detail the ranges

in geological time of about 4,000 families and 25,000 genera of

fossil marine organisms. These datasets provide a unique opportunity

for rigorous analysis of the extinction phenomenon and its distribution in time. Analyses to date have concentrated on the most recent

250 million years of the record (Mesozoic and Cenozoic eras). A

stationary periodicity of 26 x 106 years has been established for

extinction events in the family data and these events have been

confirmed with the generic data. Furthermore, the generic data,

having better time resolution, make it possible to pinpoint the

events more exactly. This in turn provides a "map" which can be

used as a guide for detailed field and laboratory studies of the

events themselves. Geochemical and other analyses of the finer

scale details of the events should lead ultimately to a clearer

understanding of the nature of the environmental stresses and thence

to the nature of the extraterrestrial forces involved. Associated

with these studies are analyses of other aspects of earth history

which may have signatures indicative of extraterrestrial effects.

Included are analyses of the history of reversals of the earth's

magnetic field over the last 160 million years. There appears

to be a statistically robust, stationary periodicity of 30 x 106

years in the intensity of reversal activity, a periodicity which

may be related to the extinction periodicity.

102
THEFOSSIL_CORDOFEVOLUTION:

N86-26902

DATA ON DIVERSIFICATION AND EXTINCTION

J. John Sepkoski, Jr.*

University of Chicago

Chicago, lllinois 60637

Synoptic studies of the fossil record of complex life on earth

indicate increasingly that extinction,and especially mass extinction,

have been extremely important driving forces in life's history.

Analysis of a new compilation of geologic ranges for 25,000 genera of

marine animals suggests that extinction events have been much more

frequent in occurrence and variable in magnitude than previously

suspected. At least 30 well-documented and potential mass extinctions

can be identified in the dataset. The most recent i0 events,

distributed over 260-0 ma, exhibit a stationary periodicity of 26.2 ± i ma,

implicating a cosmological forcing mechanism. Earlier events, especially

in the 575-450 ma interval, are more frequent, possibly indicating

either (i) a breakdown of periodicity in the more distant past;

(2) an as yet undemonstrated diminution (possibly abruptly) of the

period length; or (3) frequent aperiodic terrestrial perturbations of a

less stable biota superimposed upon the cosmological periodicity.

Other analyses of the generic dataset indicate three aspects of

extinction that may be important in governing what are perceived as

"progressive" trends in life's history: (i) The average intensity of

background extinction decreases markedly through time from about 50%/7 ma

between 500 and 575 ma to less than 10%/7 ma over the last 65 ma.

This implies that the rate of change of marine faunas (and their

possessed morphologies) has been declining since complex life first

diversified. (2) Extinction is indiscriminate with respect to oceanic

environments, at least through the Paleozoic Era (245-575 ma). No

perceptible large-scale differences that are independent of the

intrinsic turnover rates within taxa can be found from nearshore to

deep-water habitats. (3) Long-established taxa (especially families),

many of which appear archaic in aspect, have a disproportionately

higher probability of extinction during events of mass extinction than

during normal, background intervals. Therefore, since younger taxa

have a higher chance of survival, mass extinctions will speed biotic

change even more than expected from simple rebounds following random

elimination of faunal elements.

103
" N86:26903

Geochemical Anomalies, Bolide Impacts and

Biological Extinctions on the Earth

Frank Asaro , Luis W. Alvarez, H. V. Michel

Lawrence Berkeley Laboratory

and

W. Alvarez

University of California at Berkeley

Our group, in collaboration with about 30 geologists and paleontologists,

is using geochemical and mineralogical techniques to search for evidence of

extraterrestrial impacts associated with mass and lesser biological extinction

peaks in the geological record. Such geochemical anomalies, particularly

those of Ir, can provide very precise relative dating of rock strata in different parts of the world and determine just how synchronously extinctions of

different taxa took place and the extent to which evolution changed more or

less gradually or abruptly.

Studies of the Cretaceous-Tertiary boundary serve as a baseline for

evaluating geochemical data from the extinction horizons. It was found, for

example, that two such sections half way around the world from each other

which experienced similar marine (reducing) environments have chemical abundances as similar as two samplings of the same section.

Other studies were generally concentrated on rock strata corresponding to

the periodic extinction peaks noted by Raup and Sepkoski. A significant iridium anomaly in late Eocene marine sediments associated with extinctions of

radiolaria in low latitudes and attributed to an extraterrestrial source is

widely distributed in 8-9 sites around the world. Low intensity multiple Ir

anomalies have been found in sediments deposited significantly later at the

Eocene-Oligocene boundary, but further testing is necessary to determine their

origin. An Ir anomaly at the 150 MY Callovian-Oxfordian boundary observed by

others was confirmed in samples from Poland. The origin of the anomaly is

not yet determined. No Ir above background was found in samples from the

British Yorkshire coast of the 80 MY Pliensbachian-Toarcian boundary. No Ir

could be detected in samples of the _230 MY Permian-Triassic boundary from

the same quarry that Chinese scientists reported Ir. Negotiations are underway to obtain other samples from China from more propitious regions.

No Ir was detected in samples of the Precambrian-Cambrian boundary from

the Siberian platform in Russia where Russian scientists reported an Ir anomaly. Work in progress includ_samples from the _92 MY Cenomanian-Turonian

boundary, the 340 MY Frasnian-Fammenian boundary, and spherule laden strata

in the Precambian. A high capacity Iridium Coincidence Spectrometer which is

capable of analyzing 20,000 samples per year is under construction.

104
N86-26904

CLIMATIC CONSEQUENCES OF VERY HIGH CO 2 LEVELS

IN EARTH'S EARLY ATMOSPHERE

James F. Kastlng*

Space Science Division

NASA Ames Research Center

Moffett Field, CA 94035

Two factors which would have strongly influenced prebiotic evolution and

the origin of life were the composition and climate of the early atmos_

phere. Current theories of atmospheric evolution favor the idea that

the primitive atmosphere consisted primarily of CO 2, H20, and N2, with

trace amounts of reduced species such as CO and H 2. CO 2 is particularly

important because it is an effective infrared absorber which could have

warmed the Earth's surface by contributing to the greenhouse effect. It

also provides a source for oxygen atoms which would have influenced

early atmospheric chemistry. It is therefore useful to try to under_

stand the factors controlling the CO 2 abundance in the early atmosphere,

and to model the climatic and photochemical effects of various plausible

CO 2 levels.

Earth has approximately 60 bars of carbon dioxide tied up in carbonate

rocks, or roughly 2/3 the amount of CO 2 that Venus has in its atmosphere. Two different lines of evidence, one based on thermodynamics and

the other on geochemical cycles, indicate that a substantial fraction of

this CO 2 (I0_20 bars) may have resided in the atmosphere during the

first few hundred million years of the Earth's history. A natural

question which arises is whether this much CO 2 would have resulted in a

runaway greenhouse, that is, an atmosphere which was too hot to allow

the existence of liquid water at the surface. One-dimensional radia_

tive/convective model calculations presented here show that the surface

temperature of a hypothetical primitive atmosphere containing 20 bars of

CO 2 would have been less than 100 °C; thus, no runaway greenhouse should

have occurred. The climatic stability of the early atmosphere is a

consequence of three factors: reduced solar luminosity at that time, an

increase in planetary albedo caused by Rayleigh scattering by CO 2, and

the stabilizing effects of moist convection. The latter two factors are

sufficient to prevent a C02_induced runaway greenhouse on the present

Earth as well, for CO 2 levels up to 100 bars. Further studies are being

undertaken to determine whether a runaway greenhouse could have occurred

during the latter stages of the accretion process and, if so, whether it

would have collapsed once the influx of material slowed down.

105
Session VIII

Search for Extraterrestrial Intelligenee

106
Ns6: 69o 

A DECADE OF SETI OBSERVATIONS

Robert S. Dixon*

Ohio State University Radio Observatory

2015 Neil Avenue

Columbus, Ohio 43210

To the current limits of man's observational and theoretical

knowledge, there is no evidence that intelligent life has not

arisen elsewhere in the universe. Man's instruments are as yet

too feeble to show the absence of life elsewhere, but they do

provide the possibility of detecting its presence. There may

exist communications signals from other civilizations that could

be detected with today's technology. Such signals could be

intended for internal consumption (such as our own radio,

television, radar, etc.) or for wide dissemination in space

(navigation beacons, intercivilization communications, broadcasts

seeking emerging civilizations, etc.). The microwave portion of

the electromagnetic spectrum has the lowest level of naturally

occurring background noise, and is hence the most efficient place

to conduct long-range communications. For this reason, the

microwave region is a good starting point for a search for

extraterrestrial intelligence.

A full-time dedicated search for extraterrestrial radio signals

of intelligent origin has been in progress at the Ohio State

University Radio Observatory since 1973. The radio telescope has

a collecting area of 2200 square meters, which is equivalent to a

circular dish 175 feet in diameter. The search concentrates on a

500 kHz bandwidth centered on the 1420 MHz hydrogen line, doppler

corrected to the galactic standard of rest. A large portion of

the sky visible from Ohio has been searched, with particular

emphasis on the galactic center region and the M31 Andromeda

galaxy. The survey is largely computer-automated, and all data

reduction is done in real time. Two distinct populations of

signals have been detected. The first is a relatively small

number of signals which persist for over a minute and which are

clearly extraterrestrial in origin. The second is a large number

of signals which persist less than 10 seconds whose locations are

anticorrelated with the galactic plane but show clumps along the

galactic axis. None of these signals have been observed to

recur, despite repeated observations. The cause of these signals

has not yet been determined.

107
N86-26906

The Berkeley Serendip Project

Stuart Bowyer, Dan Werthimer* Jill Tarter and Rachael Buhse

University of California, Space Sciences Laboratory

Berkeley, California 94720

We are developing an automated system designed to perform a real

time search for narrow band radio signals in the spectra of sources in

a regularly scheduled, non-SETl astronomical observing program. Because we expect this system to run continuously without requiring dedicated observing time, we hope to survey a large portion of the sky

at high sensitivity and low cost. This system Will compute the power

spectrum using a 65,536 channel fast Fourier transform processor with

a real time bandwidth of 128 KHz and 2 Hz per channel resolution.

After searching for peaks in a I00 KHz portion of the radio telescope's

IF band, this system will move to the next I00 KHz portion using a

programmable frequency synthesizer; when the whole IF band has been

scanned, the process will start again. Unidentified peaks in the power

spectra are candidates for further study and their celestial coordinates

will be recorded along with the time and power, IF and RF frequency,

and bandwidth of the peak.

Most of the hardware has now been developed and we are in the

process of finalizing the machine software. We are also in the process

of developing software to process the data tapes. We are investigating

a number of means for identifying and rejecting power spectra peaks which

have a high likelihood of being non-useful. We expect to start a trial

run of the instrumentation at the Hat Creek Radio Observatory in Northern

California in late summer.

i08
N86-26907

AN INFRARED SEARCH FOR

EXTRATERRESTRIAL LASER SIGNALS

Albert Betz*

Space Sciences Laboratory

University of California, Berkeley

The focus of NASA's SETI program is on microwave frequencies, where receivers fundamentally have the best sensitivity for the detection of

narrowband signals. Such receivers, when coupled to existing radio

telescopes, form an optimum system for broad area searches over the

sky. For a directed search, however, such as toward i00 selected stars,

it can be shown that infrared frequencies are equally as effective for

maintaining an interstellar communication link. Although infrared receivers have higher noise levels, the directivity of infrared telescopes

is also higher. As a result, the signal-to-noise ratios of radio and

infrared links are quite comparable. In addition, the sensitivities

of both receiving systems, even at terrestrial levels of technology,

are quite close to their respective fundamental limits: background

thermal noise for the radio system and quantum noise for the infrared

receiver. Consequently, the choice of an optimum communication frequency may well be determined by the power and efficiency levels of

available transmitters. In the infrared, CO 2 laser transmitters with

>I MW power can already be built on Earth. For a slightly more advanced civilization, a similar but enormously more powerful laser may

be possible by using an entire planetary atmosphere rich in CO 2. Because of these possibilities and our own ignorance of what is really the

"optimum" frequency, a search for narrowband infrared signals should

be a part of a balanced SETI program.

Detection of narrowband infrared signals is best done with a laser heterodyne receiver similar in function to a microwave spectral line receiver. We have built such a receiver for astrophysical observations

at 30 THz (i0 microns) and now are adapting the spectrometer for SETI

work. The receiver uses a small CO 2 laser as the local oscillator, a

HgCdTe diode as the photomixer, and a multichannel intermediate frequency (IF) filterbank. An advanced multichannel IF processor is now

being built to detect infrared line radiation in i000 spectral channels

each i MHz wide. When completed this processor will be used with a

ground-based telescope next year for a survey of several hundred selected stars for narrowband CO 2 laser signals at 30 THz.

109
N86-26908

USING THE IRAS DATA TO SEARCH IN THE ASTEROID BELT

FOR ANY POTENTIAL EVIDENCE OF GALACTIC COLONIZATION

Michael D. Papagiannis*

Department of Astronomy

Boston University

Boston, Massachusetts 02215

The end product of the biological evolution seems to be the

appearance of technological civilizations, which are characterized by

their superior technology that supersedes their biological capabilities.

The Search for Extraterrestrial Intelligence (SETI) has gained in recent

years wide scientific recognition (the first IAU Symposium on the Search

for Extraterrestrial Life was held with great Success in Boston, June

18-21, 1984, and was cosponsored by the IAF/IAA, COSPAR, ISSOL, IUBS, and

NASA), and strong momentum in its experimental programs.

The concept of galactic colonization has been debated extensively,

with opinions ranging from the impossible to the inevitable, but without

a clear resolution. Answers can be obtained only with experimental tests

and not with endless debates. One of the alternative scenarios is that

the colonization of the Galaxy, including our solar system, occurred a

long time ago, but for some reason they have chosen not to reveal their

presence to us. A test of this theory would be to search for large space

colonies in the asteroid belt, which is an ideal source of raw materials

for a space-borne civilization, and where they could have easily remained

undetected among the thousands of natural asteroids.

The catalogue of solar system objects obtained from the Infrared

Astronomy Satellite (IRAS) observations at 12, 25, 60, and 100 microns,

is an ideal source for such a search. The catalogue is expected to be

ready at the end of 1985 and will contain more than I0,000 objects. I

plan to go carefully through this catalogue, and possibly even through

earlier and larger data banks, in search for objects with a peculiar

infrared spectrum that might indicate an artificial origin. If any such

candidates are found, they will be subjected to further optical and radio

tests.

In a comprehensive and universal search for extraterrestrial

intelligence, it seems prudent not to forget to check also our own back

yard.

ii0
OVERVIEWOF THE NASA SETI PROGRAM

Bernard M. Oliver*

NASA Ames Research Center

Scientific discoveries over the past 50 years have completely

reversed our opinion as to the prevalence of life in the

universe. No longer is the sun's retinue of planets thought

to be unique, nor the origin of life on a fertile planet

thought to be unlikely. In fact there may be on the order

of i0 I0 potential life sites in the Galaxy. If life on only

1% of these has evolved intelligence we are not only not

alone, we are in a crowd!

The only practical way we know to find other civilizations

around other stars is to detect signals they may be

radiating either for their own purposes or to attract our

attention. The NASA Search for Extraterrestrial

Intelligence (SETI) program plan is to scan the microwave

window from i to i0 GHz with existing radio telescopes and

sophisticated signal processing equipment looking for narrow

band features that might represent artificial signals.

A microwave spectrometer has been built and is being field

tested. A pattern recognition computer to search for

drifting CW signals and pulse trains in the output spectra

is being designed. Equipment to characterize the radio

frequency interference environment has also been built.

The plan is to complete the hardware and software by FY 88.

Then, with increased funding, this equipment will be

replicated in VLSI form. Observations, both a complete sky

survey and a search of nearby solar type stars, will begin

in about 1990.

The sensitivity, sky and frequency coverage of this search

will far exceed all previous searches but will still be

inadequate to detect inadvertent leakage signals from any

but the closest stars. We will be testing the hypotheses

that very powerful signals exist or that signals are being

beamed at us. To detect the kinds of signals we radiate at

distances of 100 light years will require a collecting area

kilometers in diameter.

111
• IF .- N86-26910

Stanford Hardware Development Program

Allen Peterson, Ivan Linscott* and Jim Burr

Radioscience Laboratory, Stanford University

We are developing architectures for high performance, digital

signal processing, particularly for high resolution, wide

band spectrum analysis. These developments are intended to

provide instrumentation for NASA's Search for Extraterrestrial

Intelligence (SETI) program. Our approach to real time

signal processing is both formal and experimental. We are

investigating the efficient organization and optimal scheduling of signal processing algorithms. This work is

comp_mented by efforts in processor architecture design and

implementation. Even though we have limited our scope to

real time signal processing, our microcoded signal processors

are capable of performing more general purpose computations

at very high speeds.

We currently are testing a high resolution, multichannel

spectrometer that incorporates special purpose microcoded

signal processors. We are designing a more general purpose

signal processor for the data from the multichannel spectrometer, to function as the processing element in a highly

concurrent machine. The processor performance required for

the spectrometer is in the range of i000 to i0,000 million

instructions per second (MIPS). We are interested in

multiple node processor configurations where each node

performs at I00 MIPS. The nodes are microprogrammable and

are interconnected through a network with high bandwidth for

neighboring nodes, and medium bandwidth for nodes at

"larger" distance. We are proceeding with the implementation of both the current multichannel spectrometer and the

signal processor as VLSI CMOS chip sets.

112
N86-26911

Goldstone Field Test Activities: Target Search

Jill Tarter*

University of California Berkeley Astronomy Department

SETI Institute

In March of this year protoytpe SETI equipment was installed at DSSI3, the 26

meter R&D antenna at NASA's Goldstone complex of satellite tracking dishes. The

SETI equipment will remain at this site at least through the end of the summer

so that the hardware and software developed for signal detection and recognition

can be fully tested in a dynamic observatory environment. The field tests are

expected to help us better understand which strategies for observing and which

signal recognition algorithms perform best in the presence of strong man-made

interfering signals (RFI) and natural astronomical sources.

The SETI prototype consists of a 74000 channel, wlrewrap implemented, multichannel spectrum analyzer (MCSA) mated to a VAX 11/750 computer. The VAX serves

as a host for the signal recognition algorithms and directs communications with

the antenna control system. A SUN Workstation provides real time data display.

A scanning spectrometer, connected to a small rotating dish under independent

control of a dedicated mlnl-computer, provides an RFI site surveillance capability over the frequency range of i-I0 GHz. This equipment has been designed for

use in a bl-modal SETI search strategy and is intended to be flexible enough to

address the special requirements of both a selected target search mode and a

survey of the entire sky.

During a search that looks in the vicinity of nearby solar-type stars, data from

one source may be acquired for up to I000 seconds. This time allows a search for

a variety of signal types, in particular, narrowband continuously present

signals (CW) at a single frequency (or drifting slowly in frequency) and

narrowband pulses that repeat with a regular periodicity somewhere between a few

milliseconds and a few hundred seconds. These pulses may also be changing their

frequency slowly in time. The field tests give us the opportunity to investigate

the effective sensitivity of such a long sidereal observing track in view of the

elevation dependent system temperature and RFI contribution. How close to the

horizon can we expect to operate at Goldstone, or other sites? In the presence

of strong RFI, is it best to remain on source and switch to another band of

frequencies, or is it better to remain on frequency and slew to a source in a

different part of the sky? Can astronomical sources be easily identified? What

are the effects of strong, but transient, RFI on algorithms optimized for

recognition of weak pulses or CW signals? Does RFI recognition and rejection

become easier if the receiver's local oscillators are not corrected to compensate for the orbital and rotational components of the Earth's motion relative to

the target source? How severely will the scintillation caused by the interplanetary and interstellar plasma modulate a distant ETI signal and how well do

the algorltms we have developed function in the face of this amplitude

modulation? What is the best strategy for obtaining a "reference" spectrum, or

fitting a baseline to the channel outputs at a given frequency resolution? What

will be the actual percentage of time spent slewing between sources, observing

reference sources and making repairs to the overall system? What is the optimum

way to schedule the target observations in order to maximize the efficiency of

the SETI search and the chances for radio astronomical fallout? How long will

it actually take to search the nearest I000 solar-type over a range of

frequencies from I to 3 GHz?

113
NS6-26912

GOLDSTONE FIELD TEST ACTIVITIES: SKY SURVEY

Samuel Gulkis and Edward T. Olsen*

NASA Jet Propulsion Laboratory

The goals are to conduct a research and development program aimed

at determining the most effective way to do SETI within the

constraints of current technology and estimated budgets. The

general search strategy adopted is that which is recommended by

the SETI Science Working Group (NASA Technical Paper 2244, Eds.

F. Drake, J.H. Wolfe, and C.L. Seeger, October 1983).

The strategy for an all sky survey for SETI has been further

developed over the last year. Scan patterns, scan rates, and

signal detection algorithms have been developed. Spectral power

measurement instrumentation has been tested at the Venus Station

of the Goldstone Deep Space Communication Complex. A specially

designed radio frequency interference measurement system was built

and installed at the Venus Station. A Data Base Management system

for storage and retrieval of the RFI data has been partially

implemented on a VAX 750 computer at the Jet Propulsion

Laboratory.

114
N86-26913

JPL'S ROLE IN THE SETI PROGRAM

Michael J. Klein*

NASA Jet Propulsion Laboratory

The goal of the JPL SETI Team is to develop the strategies and

the instrumentation required to carry out an effective, yet

affordable, SETI Microwave Observing Program. The primary

responsibility for JPL is the development and implementation of

the Sky Survey component of the bimodal search program

recommended by the SETI Science Working Group (NASA Technical

Paper 2244, 1983). JPL is also responsible for the design and

implementation of microwave analog instrumentation (including

antenna feed systems, low noise RF amplifiers, antenna monitor

and control interfaces, etc.) to cover the microwave window for

the Sky Survey and the Target Search observations.

The primary site for the current SETI Field Test activity is the

Venus Station of the Goldstone Deep Space Communication Complex.

A significant fraction of the JPL work units has been directed

toward the support of the Field Tests. A SETI controller was

constructed and installed so that pre-programmed and real time

SETI monitor and control data can be sent to and from the station

controller. This unit will be interfaced with the MCSA. A SETI

Hardware Handbook was prepared to describe the various systems

that will be used by the project at the Venus Station; the handbook is frequently being expanded and updated. The 65,000 channel

FFT Spectrum analyzer in the RFI Surveillance System was modified

to permit operation with variable resolutions (300 Hz to less

than 1 Hz) and with real-time accumulation, which will enhance

the capability of the system for testing Sky Survey search strategies and signal detection algorithms.

Progress was also made in the preparation of a SETI

Implementation Plan for the Deep Space Network (DSN), which will

be called upon to support the Microwave Observing Program through

the use of the DSN antennas and low-noise receiving systems.

Modifications will be necessary to meet the radio frequency

coverage and the antenna monitor and control functions that are

required.

115
Author Index

Altekar, W., 91

Alvarez, L.W., 104

Alvarez, W., 104

Arakawa, E.T., 48

Armangue, G., 78

Asaro, F., 104

Baur, M.E., 84

Bermudes, D., 99

Betz, A., 109

Blair, N.E., 40

Borucki, W.J., 52

Bowyer, S., 108

Brenner, T., 73

Buchanan, B.B., 93

Buhse, R., 108

Bui, H., 100

Bunch, T.E., 41, 59

Burr, J., 112

Callcott, T.A., 48

Carle, G.C., 50, 53-54, 57-59

Carr, L.P., 82

Chang, S., 40, 50, 63

Clark, B.C., 54

Coyne, L.M., 65

Cronin, J.R., 40

DeFrees, D., 43

Des Marais, D.J., 40, 81, 100

Dixon, R.S., 107

Eirich, F.R., 66

Fahey, R.C., 96

Fox, G.E., 87

Fox, S.W., 76

Ferris, J.P., 44

Folsome, C.E., 77

Friedmann, E.I., 97

Gibson, E.K., Jr., 82

Gilmour, I., 82

Gulkis, S., 114

Gutell, R.R., 88

Hall, L.M., 71

Hartman, H.H., 64

Hayes, J.M., 84

Herbst, E., 43

Hobish, M.K., 62

Hochstein, L.I., 91

Holland, H.D., 68

Huizinga, B.E., 83

Irvine, W.M., 42

Jah nke, L.L., 95

Jukes, T.H., 90

Kanavarioti, A., 69

Kaplan, I.R., 83

Kasting, J.F., 52, 105

Kaufman, A.J., 84

Kerridge, J.F., 63

Khanna, R.K., 47

Khare, B.N., 48

Kim, S.-J., 49

Klein, C., 84

Klein, M.J., 115

Kobayashi, K., 62

Kojiro, D.R., 53, 58

Kristjansson, H., 91

Kwong, E., 100

Lacey, J.C., Jr., 71

Lahav, N., 67

Lanyi, J.K., 92

Levine, J.S., 47

Ley, A., 94

Linscott, I., 112

117
Lu-Lin, H., 62

Lunine, J.I., 49

MacElroy, R.D., 70

Macklin, J.W., 69

Mar, A., 78

Margulis, L., 99

Mauzerall, D., 94

McDonald, J., 75

McKay, C.P., 50, 52

McLean, D., 43

Mercer-Smith, J'A'' 94

Michel, H.V., 104

Miller, S.L., 52, 61

Mullins, D.W., Jr., 71

Nagy, B., 48

Nakashima, T., 76

Needels, M.C., 73

Newton, G.L., 96

Nibley, C., 69

Obar, R., 99

Oberbeck. V.R., 53

Ocampo-Friedmann, R., 97

Ogino, H., 48

O'Hara, B.J., 50, 53-54

Oliver, B.M., 111

Olsen, E.T., 114

Orenberg, J., 67

Orgel, L.E., 72

Oro, J., 78

Paecht-Horowitz, M., 66

Papagiannis, M.D., 110

Pavlicek, K.A., 98

Peterson, A., 112

Peterson, E., 100

phillips, J.B., 57

Pillinger, C.T., 82

Pinto, j.p., 49, 68

Pohorille, A., 70

Pollock, G.E., 55

Ponnamperuma, C., 62

przybylski, A., 76

Raghunathan, G., 75

Raup, D.M., 102

Rein, R., 75

Rich, A., 79

Sagan, C., 48

Scattergood, T.W., 50, 52-53

Schloerb, F.P., 42

Schopf, J.W., 87

Senaratne, N., 62

Sepkoski, J.J', Jr., 103

Shibata, M., 75

ShipP, R., 63

Shrader, S., 48

Sibley, M.H., 98

Srinivasan, S., 75

Stribling, R., 61

Studley, S.A., 84

Suits, F., 48

Tannenbaum, E., 83

Tarter, j., 45, 108, 113

Tennille, G.M., 47

Thompson, W.R., 48

Towe, K.M., 47

Usher, D.A., 73

Valentin, J.R., 53, 57

Vaughan, G., 76

Walker, J.C.G., 85

Walter, M.R., 84

Wang, A. H.-J., 79

Watkins, C.L., 71

Weber, A.L., 74

Wedeking, K., 63

Werthimer, D., 108

White, D.H., 69

Willingham, T.O., 48

Williams, M.W., 48

Woeller, F.H., 56

Woese, C.R., 88

Wolfe, J.H., 59

Yopp, J.H., 98

Yuen, G.U., 40

Yung, Y.L., 49

Zahnle, K.J., 85

Zbinden, E.A., 68

Ziurys, L.M., 42

i18
Appendix

Symposium Participants

Oscar L. Acevedo

The Salk Institute for

Biological Studies

San Diego, CA

Joe Alvarnas

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Frank Asaro

Lawrence Berkeley Laboratory

Berkeley, CA

Maurice Averner

(University of New Hampshire)

NASA Headquarters

Washington, D.C.

Peter Backus

Mail Stop 229-8

NASA Ames Research Center

Moffett Field, CA

John Balboni

Mail Stop 229-4

NASA Ames Research Center

Moffett Field, CA

Lorraine Beeman

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

David Bermudes

Boston University

Boston, MA

Albert L. Betz

University of California

Berkeley, CA

John Billingham

Mail Stop 239-11

NASA Ames Research Center

Moffett Field, CA

William J. Borucki

Mail Stop 245-3

NASA Ames Research Center

Moffett Field, CA

Penelope Boston

National Center for

Atmospheric Research

Boulder, CO

Stuart Bowyer

University of California

Berkeley, CA

Bob B. Buchanan

University of California

Berkeley, CA

Vera Buescher

Mail Stop 229-8

NASA Ames Research Center

Moffett Field, CA

Rachel Buhse

University of California

Berkeley, CA

Hoa Bui

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Theodore E. Bunch

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Sara Bzik

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Glenn C. Carle

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

119
Sherwood Chang

Mail Stop 239-11

NASA Ames Research

Moffett Field, CA

Center

Michael Cheatham

(University of California,

Los Angeles)

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Christopher Churchill

Mail Stop 245-3

NASA Ames Research Center

Moffett Field, CA

Benton Clark

Martin Marietta

Denver, CO

Judie L. Corrales

Mail Stop 239-10

NASA Ames Research

Moffett Field, CA

Center

Lelia M. Coyne

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Sonia Cronin

Mail Stop 239-10

NASA Ames Research

Moffett Field, CA

Center

Kent Cullers

Mail Stop 229-8

NASA Ames Research

Moffett Field, CA

Center

Mike Davis

Mail Stop 229-8

NASA Ames Research

Moffett Field, CA

Center

Wanda Davis

Molecular Research

Palo Alto, CA

Institute

David W. Deamer

University of California

Davis, CA

Stanley R. Deans

Mail Stop 229-8

NASA Ames Research

Moffett Field, CA

Center

Doug DeFrees

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

David J. Des Marais

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Donald L. DeVincenzi

NASA Headquarters

Washington, D.C.

Robert S. Dixon

Ohio State University

Columbus, OH

William Drew

California Institute

Technology

Pasadena, CA

of

Joyce Durado

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Frederick R. Eirich

Polytechnic Institute

New York

Brooklyn, NY

of

Joze Erlichman

Mail Stop 245-5

NASA Ames Research

Moffett Field, CA

Center

Robert C. Fahey

University of California

San Diego, CA

120
James P. Ferris

Rensselaer Polytechnic

Institute

Troy, NY

Ben Finney

Mail Stop 229-8

NASA Ames Research Center

Moffett Field, CA

Clair E. Folsome

University of Hawaii

Honolulu, HI

George E. Fox

University of Houston

Houston, TX

Sidney W. Fox

University of Miami

Coral Gables, FL

Friedemann Freund

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

E. Imre Friedmann

Florida State University

Tallahassee, FL

R.O. Friedmann

Florida A & M University

Tallahassee, FL

John S. Garavelli

Mail Stop 239-4

NASA Ames Research Center

Moffett Field, CA

Kevin Gardner

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Des Garner

San Francisco State University

San Francisco, CA

Joseph George

University of Santa Clara

Santa Clara, CA

Everett K. Gibson, Jr.

NASA Johnson Space Center

Houston, TX

David Grinspoon

University of Arizona

Tucson, AZ

Robin R. Gutell

University of Illinois

Urbana, IL

David Harper

Mail Stop 229 -8

NASA Ames Research Center

Moffett Field, CA

Jean Harris

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Hyman H. Hartman

Massachusetts Institute of

Technology

Cambridge, MA

John M. Hayes

Indiana University

Bloomington, IN

Mitchell K. Hobish

University of Maryland

College Park, MD

Lawrence I. Hochstein

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Martin Hoffert

New York University

New York, NY

121
Lois P. Hunt

Georgetown University

Medical Center

Washington, D.C.

Heather Huppe

University of California

Berkeley, CA

William M. Irvine

University of Massachusetts

Amherst, MA

Johnny Jackson

University of California

Berkeley, CA

Linda L. Jahnke

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Tom Johnson

University of California

Berkeley, CA

Thomas H. Jukes

University of California

Berkeley, CA

Toivo Kallas

University of California

Berkeley, CA

Anastassia Kanavarioti

Mail Stop 239-12

NASA Ames Research Center

Moffett Field, CA

Isaac R. Kaplan

University of California

Los Angeles, CA

James F. Kasting

Mail Stop 245-3

NASA Ames Research Center

Moffett Field, CA

John F. Kerridge

University of California

Los Angeles, CA

Michael J. Klein

Jet Propulsion Laboratory

Pasadena, CA

Bob Krekorian

Mail Stop 229-8

NASA Ames Research Center

Moffett Field, CA

Hordur Kristjansson

Mail Stop 239-10

NASA Ames Research Center

Moffett Field, CA

Emil Kwong

(Arizona State University)

NASA Ames Research Center

(239-12)

Moffett Field, CA

James C. Lacey, Jr.

University of Alabama

Birmingham, AL

Janos K. Lanyi

University of California

Irvine, CA

James Lawless

Mail Stop 242-4

NASA Ames Research Center

Moffett Field, CA

Antonio Lazcano-Aranjo

University of Mexico

Mexico City, Mexico

Louis Lerman

Stanford University

Stanford, CA

Susan Leschine

University of Massachusetts

Amherst, MA

Joel S. Levine

NASA Langley Research Center

Hampton, VA

Vickey Lindsey

University of California

Berkeley, CA

L

122
Ivan Linscott

(Stanford University)

NASA Ames Research Center

Mail Stop 229-8

Moffett Field, CA

Lesa Lochmyer

Mail Stop 245-12

NASA Ames Research

Moffett Field, CA

Center

Bernhard Londoner

Mail Stop 245-3

NASA Ames Research

Moffett Field, CA

Center

Robert D. MacElroy

Mail Stop 239-10

NASA Ames Research

Moffett Field, CA

Center

John Macklin

University of

Seattle, WA

Washington

Rocco Mancinelli

Mail Stop 239-10

NASA Ames Research Center

Moffett Field, CA

Anthony Mannucci

University of California

Berkeley, CA

Joan Mathog

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Marsha Mathog

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Nick Matorangus

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

David Mauzerall

Rockefeller University

New York, NY

123

Jerri Mazzurco

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Chris P. McKay

Mail Stop 239-12

NASA Ames Research

Moffett Field, CA

Center

Jennifer McPhate

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Center

Susan Mead

Mail Stop 239-11

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Moffett Field, CA

Center

Heide Meiners

Mail Stop 239-12

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Moffett Field, CA

Center

Stanley L. Miller

University of California

San Diego, CA

Richard M. Mitterer

University of Texas

Dallas, TX

Tom Monyette

Mail Stop 239-12

NASA Ames Research Center

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David Moore

Mail Stop 239-12

NASA Ames Research

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Center

Diane Moser

Space World Magazine

Washington, D.C.

Eric Muller

University of

Berkeley, CA

California
Mark Myrhum

University of

Madison, WI

Wisconsin

Bonnie J. O'Hara

Mail Stop 239-12

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Center

Sofia Oldmark

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Center

Bernard M. Oliver

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Edward T. Olsen

Jet Propulsion Laboratory

Pasadena, CA

James B. Orenberg

San Francisco State

San Francisco, CA

University

Leslie E. Orgel

The Salk Institute

Biological Studies

San Diego, CA

for

John Oro

University of

Houston, TX

Houston

Rob Palmer

Mail Stop 239-10

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Center

Michael D. Papagiannis

Boston University

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Tom Perry

NASA Headquarters

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Etta Peterson

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John B. Phillips

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Tom Pierson

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Joseph P. Pinto

(Harvard University)

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Andrew Pohorille

(University of California,

Berkeley)

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Glenn E. Pollock

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Center

Greg Rau

(San Francisco State

University)

NASA Ames Research Center

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Moffett Field, CA

David M. Raup

University of

Chicago, IL

Chicago

Robert Rein

Roswell Park

Institute

Buffalo, NY

Memorial

124
Bashar Rizk

University of

Tucson, AZ

Arizona

John Rummel

Mail Stop 239-4

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Patricia Russell

American Institute of

Biological Sciences

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Carl Sagan

Cornell University

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Thomas W. Scattergood

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Gene Schloemer

Photo & Sound of

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University of Chicago

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University of Arizona

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Center

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Stanford, CA

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Space World Magazine

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Center

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University of Santa

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Clara

Norishige Takeuchi

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Gery Tomlinson

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Center

Desiree Tsao

San Francisco State

San Francisco, CA

University

125
David A. Usher

Cornell University

Ithaca, NY

Jose R. Valentin

Mail Stop 239-12

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Moffett Field, CA

Center

Tyler Volk

(New York University)

NASA Ames Research Center

Mail Stop 239-4

Moffett Field, CA

Andrew H.-J. Wang

Massachusetts Institute

Technology

Cambridge, MA

of

Arthur L. Weber

The Salk Institute

Biological Studies

San Diego, CA

for

Esther Varon Weber

The Salk Institute

Biological Studies

San Diego, CA

for

Kim Wedeking

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Center

Daniel Werthimer

University of California

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Robert _arton

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Center

David H. White

Mail Stop 239-12

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Warren Winovich

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Center

Fritz H. Woeller

Mail Stop 239-12

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Center

John H. Wolfe

San Jose State

San Jose, CA

University

Peter Wood

(University of California,

Berkeley)

NASA Ames Research Center

Mail Stop 239-4

Moffett Field, CA

John H. Yopp

Southern Illinois

Carbondale, IL

University

Richard S. Young

GE-MATSCO

Washington, D.C.

George U. Yuen

Arizona State University

Tempe, AZ

126
1. Report No. 2. Government Accez=ionNo. 3. Recipient's Catalog No.

NASA CP-2425

4. Title and Subtitle

Second Symposium on Chemical Evolution and the

Origin and Evolution of Life

7. Author(s)

Donald L. DeVincenzl and Patricia A. Dufour,

,,.

9. PerformingOrganization Name and Addrest

Life Sciences Division

Office of Space Science and Applications

Washington, DC 20546

!2. S_nsoring A_ncy Name and Addr_s

National Aeronautics and Space Administration

Washington, DC 20546

Editors

5. Report Date

May 1986

6. Performing Organization Code

EBR

8. PerformingOrganization Report No.

10. Work Unit No.

'11. Contract or Grant No.

NASW- 3165

13. Type of Report and Period Covered

!Conference Publication

14. Sponsoring Agency Code

15. _pplementary Notes

Donald L. DeVincenzi: NASA Headquarters, Washington, D.C.

Patricia A. Dufour: The George Washington University, Washington, D.C.

Proceedings of the First Symposium on Chemical Evolution and the Origin and

Evolution of Life are available as NASA Conference Publication 2276 (1983).

16. Abstract

This symposium was held at the NASA Ames Research Center, Moffet Field,

California, July 23-26, 1985. The NASA Exobiology principal investigators

reported their recent research findings. Scientific papers were presented

in the following areas: cosmic evolution of biogenic compounds, prebiotic

evolution (planetary and molecular), early evolution of life (biological

and geochemical), evolution of advanced life, solar system exploration, and

the Search for Extraterrestrial Intelligence (SETI).

17. Key Words(Suggest_ by Auth.(s))

exobiology, biological evolution,

chemical evolution, planetary

evolution, extinction, space exploration, Titan, planetary atmospheres,

primitive Earth atmosphere, SETI

19. Security Oa_if.(oft_sreport) 20. SecudtyCla=if.(ofthis

Unclassified Unclassified

18. Distribution Statement

Unclassified - Unlimited

page)

Subject Category 55

21. No. ofPages 22. _ice

134 A07

For sale by the National Technical Information Service. Springfield, Virginia 22161

NASA-Langley, 1986