Abstracts of the Annual Meeting of Planetary Geologic 

Mappers, Tucson, AZ 2007 

Edited by Leslie F. Bleamaster III1, Tracy K.P. Gregg2, Kenneth L. Tanaka3, and R. Stephen Saunders4

1 Planetary Science Institute, 1700 E. Ft. Lowell Rd., Suite 106, Tucson, AZ 85719. 

2

 The State University of New York at Buffalo, Department of Geology, 710 Natural Sciences Complex, Buffalo, NY 14260. 

3

 U.S. Geological Survey, 2255 N. Gemini Drive, Flagstaff, AZ 86001. 

4

 NASA Headquarters, Office of Space Science, 300 E. Street SW, Washington, DC 20546. 

Open-File Report 2007–1233 

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U.S. Geological Survey, Reston, Virginia 2007 

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Report of the Annual Mappers Meeting 

Planetary Science Institute 

Tucson, Arizona 

June 28 and 29, 2007 

Approximately 22 people attended this year’s mappers meeting, and many more 

submitted abstracts and maps in absentia. The 2007 meeting was convened by Tracy 

Gregg, Les Bleamaster, Steve Saunders, and Ken Tanaka and was hosted by David 

Crown and Les Bleamaster of the Planetary Science Institute (PSI) in Tucson, Arizona. 

Oral presentations and poster discussions took place on Thursday, June 28 and Friday, 

June 29. This year’s meeting also included a unique opportunity to visit the operations 

centers of two active Mars missions; field trips to the University of Arizona took place on 

Thursday and Friday afternoons. 

Outgoing Geologic Mapping Subcommittee (GEMS) chairperson, Tracy Gregg, 

commenced the meeting with an introduction and David Crown followed with a 

discussion of logistics and the PSI facility; Steve Saunders (Planetary Geology and 

Geophysics Discipline Scientist) then provided a brief program update. Science 

presentations kicked off with Venus mapper Vicki Hansen and graduate students Eric 

Tharalson and Bhairavi Shankar of the University of Minnesota, Duluth, showing a 3-D 

animation of the global distribution of tesserae and discussing the implications, a 

progress report for V-45 quadrangle mapping, and a brief discussion of circular lows. Les 

Bleamaster (PSI) followed with a progress report on mapping of the V-50 quadrangle and 

the 1:10M Helen Planitia quadrangle. David Crown (PSI) concluded the Venus 

presentations with a discussion of progress made on the V-30 quadrangle. The remainder 

of Thursday’s presentations jumped around the Solar System including Mars, Io, and 

Earth. Ken Tanaka of the U.S. Geological Survey (USGS) began the afternoon with a 

general discussion of the status of the planetary mapping program at USGS. Buck Janes 

(University of Arizona) provided background information about the Mars Odyssey 

Gamma Ray Spectrometer (GRS) and presented some new element maps, which may be 

useful for geologic mapping. Dave Williams of Arizona State University reported on the 

progress of his global Io map and James Dohm (University of Arizona) discussed results 

of terrestrial remote mapping studies. Thursday afternoon, the mappers were given a tour 

of the High Resolution Imaging Science Experiment (HiRISE) operations facility and 

were given some basic information about how the images are obtained, processed, and 

publicly released. 

With official GEMS transition completed at lunch on Thursday, incoming GEMS chair 

Leslie Bleamaster took the reigns of Friday’s meeting. Science presentations began with 

Ken Tanaka discussing 1:20M-scale global and 1:2M-scale polar mapping of Mars. Jim 

Zimbelman (Smithsonian Institution) described his 1:1M Medusae Fossae map (MC-8 

SE), which is nearing completion, and new mapping (MC-16 NW and MC-23 NW) to 

further evaluate the Medusae Fossae. Brent Garry, also of the Smithsonian Institution, 

presented work on Ascraeus Mons. Peter Mouginis-Mark (University of Hawai‘i) 

reported progress on his 1:200K and larger maps of Tooting crater and of the Olympus 

Mons summit caldera. Laszlo Keszthelyi (USGS) presented mapping of Athabasca 
Valles, with much of the credit going to Windy Jaeger. Jim Skinner (USGS) introduced a 

new mapping project including nine MTM quadrangles in the Utopia Planitia region. 

Tracy Gregg finished off the day’s science presentations with discussion of Hesperia 

Planum. After discussion was complete, the group once again traveled to the University 

of Arizona - this time for a tour of the Mars Phoenix operations center. Principal 

Investigator Peter Smith beamed as he led mappers through the multi-million dollar 

facility. 

A main topic of discussion throughout the entire meeting was that of nomenclature, 

specifically how to classify the individual depressions at the tops of volcanoes. Paterae, 

as has been used for Mars, Venus, and Io, was suggested, but introduces several problems 

with the classical and literal usage of the term over the past few decades. The group 

proposed that crater, like it is used for terrestrial volcanoes, would be the most 

appropriate term and suggested that GEMS, along with Jenny Blue (USGS), approach the 

IAU to discuss this issue further. 

The next mappers meeting will be held in Flagstaff, at the U.S. Geological Survey, 

tentatively on June 19 and 20, 2008. 
CONTENTS 

Venus

Geologic Maps of Shimti Tessera (V-11) and Vellamo Planitia (V-12), Venus 

J.C. Aubele 

Geology of the Western Part of the V-36 Thetis Regio Quadrangle 

A.T. Basilevsky and J.W. Head 

Geologic Mapping of Isabella Quadrangle (V-50) and Helen Planitia, Venus 

L.F. Bleamaster III 

Global Mapping of Venus’ Ribbon Tessera Terrain: Preliminary Results 

V.L. Hansen, T. Nordberg, and I. López 

Global Geologic Map of Venus: Preliminary Results 

M.A. Ivanov

Geologic History of the Lavinia Planitia/Lada Terra Region, Venus: Results of Mapping 

in the V-55, V-61, and V-56 Quadrangles 

M.A. Ivanov and J.W. Head 

The Fredegonde (V-57) Quadrangle, Venus: Preliminary Results 

M.A. Ivanov and J.W. Head 

The V-7 Quadrangle: Sequence of Events during Formation of Lakshmi Planum, Venus 

M.A. Ivanov and J.W. Head 

Geologic Mapping of the Lada Terra (V-56) Quadrangle, Venus: Preliminary 

Observations 

P.S. Kumar and J.W. Head 

Preliminary Global Survey of Circular Lows, a Subset of Venusian Coronae 

B. Shankar and V.L. Hansen

Update on Mapping of Quadrangles V-28, V-52, and V-19 

E.R. Stofan, J.E. Guest, A.W. Brian, and P.M. Martin 

Preliminary Geologic Map of Agnesi Quadrangle, V-45 (25-50S/30-60E) 

E.R. Tharalson and V.L. Hansen 

Geologic Mapping of the Kawelu Planitia (V-16) and Bellona Fossae (V-15) 

Quadrangles on Venus 

J.R. Zimbelman 
Galilean Satellites

Global Geologic Map of Europa 

T. Doggett, P. Figueredo, R. Greeley, T. Hare, E. Kolb, D. Senske, K. Tanaka, 

and S. Weiser 

The Global Geologic Map of Ganymede 

G.W. Patterson, J.W. Head, G.C. Collins, R.T. Pappalardo, L.M. Procter, and 

 B.K. Lucchitta 

The Global Geologic Map of Io: Approach and Mapping Status 

D.A. Williams, L.P. Keszthelyi, P.E. Geissler, W.L. Jaeger, T.L. Becker, D.A. 

Crown, P.M. Schenk, and J.A. Rathbun 

Moon

Use of Clementine UVVIS and NIR Data for Lunar Geologic Mapping 

L.R. Gaddis 

Remote Sensing Studies of Copernicus Rays: Implications for the Calibration of the 

Lunar Stratigraphic Column 

B.R. Hawke, T.A. Giguere, L.R. Gaddis, B.A. Campbell, D.T. Blewett, J.M. Boyce, 

J.J. Gillis-Davis, P.G. Lucey, C.A. Peterson, M.S. Robinson, and G.A. Smith 

Mars

Geology of MTM Quadrangles -40277, -40272, -45277, and -45272, Eastern Hellas 

Planitia, Mars 

L.F. Bleamaster III and D.A. Crown 

Geologic Map of MTM 35337, 40337, and 45337 Quadrangles, Deuteronilus Mensae 

Region of Mars 

F.C. Chuang and D.A. Crown 

Mapping Margaritifer Terra: MTMs -15017, -20002, -20007, -20017, -20022, -25002, 

-25007 

C.M. Fortezzo, K.K. Williams and J.A. Grant 

Mapping Hesperia Planum, Mars 

T.K.P. Gregg and D.A. Crown

Hydrologic and Volcanic Evolution of Athabasca Valles, Mars: The First Step to 

Geologic Mapping at 1:500,000 Scale 

 L. Keszthelyi, W. Jaeger, and K. Tanaka

Geologic Mapping of the Martian Impact Crater Tooting 

P. Mouginis-Mark 
Geologic Mapping of the Olympus Mons Caldera 

P. Mouginis-Mark 

Final Map Results of the Olympia Cavi Region of Mars (MTM 85200): Geologic Units 

and History 

J.A. Skinner, Jr. and K. Herkenhoff 

Geology of the Southern Utopia Planitia Highland-Lowland Boundary Plain: Current 

Understanding and First Year Mapping Plan 

J.A. Skinner, Jr., K.L. Tanaka, and T.M. Hare

New Global Geologic Map of Mars 

K.L. Tanaka, J.M. Dohm, T.M. Hare, R.P. Irwin III, E.J. Kolb, and 

J.A. Skinner, Jr. 

Recent Geologic Mapping Results for the Polar Regions of Mars 

K.L. Tanaka and E.J. Kolb 

Margaritifer Terra Quadrangles -20012 and -25012: Reviewed and Submitted 

S.A. Wilson, J.A. Grant, and C.M. Fortezzo 

Geologic Mapping of the Medusae Fossae Formation on Mars (MC-8 SE) 

J.R. Zimbelman 

Other

Remote Geologic Mapping of Lunar Crater Volcanic Field, Nye County, Nevada: a Test 

for Planetary Geologic Reconnaissance 

J.M. Dohm, K.L. Tanaka, J.A. Skinner, Jr., L.A. Crumpler, and T.M. Hare 

Geoscience Data Visualization Systems Applied to Planetary Geological Mapping 

J.W. Head, Prabhat, A.S. Forsberg, A.T. Basilevsky, M.A. Ivanov, J.L. Dickson, 

C.I. Fassett, J.S. Levy, G.A. Morgan, and P.S. Kumar 
GEOLOGIC MAPS OF SHIMTI TESSERA (V-11) AND VELLAMO PLANITIA (V-12), VENUS 

 J.C. Aubele, New Mexico Museum of Natural History & Science, Albuquerque, NM jayne.aubele@ state.nm.us

Introduction. Two quadrangles in the Niobe 

Planitia region have been mapped as part of the Venus 

geologic mapping effort. Shimti Tessera (V-11) and 

Vellamo Planitia (V-12) are adjacent quadrangles 

located in the northern hemisphere of Venus. V-11 

extends from 25° to 50° N and 90° to 120° E, and V-12 

extends from 25° to 50° N and 120° to 150° E. 

Shimti Tessera (V-11). This quadrangle includes 

Tilli-Hanum Planitia in the north, a portion of Akkruva 

Colles in its northeast quadrant, and Niobe Planitia in its 

southeast and south-central regions. Shimti and Kutue 

Tesserae cover portions of the central and southeastern 

part of the quadrangle. Three named coronae within the 

quad are: Eurynome Corona, Metra Corona, and MaaEma Corona. Near the northern boundary of the quad are 

two named volcanic centers: Kurukulla Mons and Hiei 

Chu Patera (mapping has shown that flows originating 

from the patera clearly overlay material associated with 

Kurukulla Mons). Named impact craters include: 

Manzolini, Antonina, Irina, Vallija, Moses, and Cather, 

and several additional unnamed impact craters have been 

mapped within the quad. Medeina Chasma enters from 

the WNW, Friagabi Fossae enters from the north, and 

Uni Dorsa extends NNW-SSE across the boundary 

between V-11 and-V12. 

Vellamo Planitia (V-12). Akkruva Colles also 

extends across the V-11 and V-12 boundary to form the 

extreme northwestern portion of V-12. Ananke Tessera 

occurs in the north-central portion of the quad; however, 

most of V-12 consists of lowland plains – Vellamo 

Planitia in the northeast and Llorona Planitia in the 

southeast. Two named coronae within the quadrangle 

are: Boann Corona and Cauteovan Corona. Named 

impact craters include: Vallija (on the boundary between 

V-11 and V-12, Nijinskaya, MacDonald, Kollwitz, 

Regina, Taglioni, Polina, Almeida, Irene, Laura, 

Valentina, and Barto. Nephele Dorsa is oriented northsouth in Vellamo Planitia and and Frigg Dorsa occurs in 

the extreme northeast corner of the quad. 

Description of Stratigraphic Units. 

Tessera. In both V-11 and V-12, Tessera 

material (t) is interpreted to be the stratigraphically 

oldest unit, and is embayed by other units. Tessera 

material is radar bright and consists of at least two sets 

of intersecting ridges and grooves; it has been referred to 

as complex ridged terrain [1,2]. 

Densely lineated plains material (pdl), identical 

to the unit defined by Ivanov & Head in V-13 [3], is a 

minor unit in V-12 but covers more area within V-11, 

and appears to be spatially associated with tessera in 

most cases. This unit is characterized by parallel and 

subparallel lineaments (dominantly fractures) that are 

generally aligned in a single direction. Mapping of V-11 

provides strong observational evidence that pdl may be 

interpreted to be partially flooded or resurfaced margins 

of tessera terrain. 

Ridged and grooved plains material (prg), 

identical to the unit defined in V-13 [3], is characterized 

by sets of relatively broad ridges, arranged in linear 

belts. As Ivanov and Head stated: “although defined by 

structural elements (arches and ridges), this unit exhibits 

consistent characteristics and stratigraphic relationships 

and can be mapped as a material unit” [3]. In both V-11 

and V-12, this unit is of minor areal extent and includes 

Uni Dorsa, Nephele Dorsa, and Frigg Dorsa. 

Shield plains material (psh). During analysis of 

the Venera 15/16 data [1], some regions on Venus were 

recognized as consisting of extensive areas of small hills 

interpreted to be volcanoes, and were given the feature 

name “colles” (defined as an area of small hills or knobs) 

by the Venus nomenclature subcommittee of the I.A.U. 

During initial analysis of the Venera data and subsequent 

analysis of Magellan [4], these regions were confirmed 

as areas of abundant small, predominantly shield-type, 

volcanoes occurring over extensive areas rather than in 

the well-defined, relatively small, local clusters called 

shield fields. One of these regions is Akkruva Colles, 

first described by Schaber [5] as a region of abundant 

small volcanoes. 

Quadrangle V-12 was mapped and reports were 

presented in the mid-late 1990s [6]. The reports included 

the description and interpretation of a new unit in V-12, 

the “shield plains” or “Akkruva shield plains,” 

designated as psh in the original map (mid-90s) and in 

the current submitted map. The geologic unit described 

from V-12 is a plains unit which contains almost all of 

the small volcanoes in the Ananke Tessera area. The 

type example of this unit is located at 43N, 131.5E, and 

consists of an average density of small volcanoes 

numbering 4500/106

km2 in association with plains 

material of intermediate radar backscatter. Unit Psh 

exhibits consistent characteristics and stratigraphic 

relationships within V-12, consistently overlying tessera 

in this region and directly and consistently overlain and 

embayed by wrinkle ridged plains material. It is 

interpreted as a distinctive plains unit erupted by, or in 

association with, small volcanoes, and a useful local to 

regional stratigraphic marker. Mapping of V-11 has 

extended the significance and extent of the unit; it has 

been mapped over an area of 2.3X106

km2 in V-11 and 

V-12. Other mappers have also identified the 

continuation of this shield plains unit into adjoining 

quadrangles [3,7]. Hansen’s description of a thin, locally 

discontinuous layer that is lace-like in appearance [7] is 

an apt description of the unit as mapped. Ivanov and 
Head [3] have shown that the unit is much more 

extensive areally than was initially assumed. 

Wrinkle ridged plains material (pwr) covers 

much of V-12 and V-11; the unit is characterized by 

relatively homogeneous plains material with few 

associated small volcanoes and many wrinkle ridges in 

parallel or orthogonal patterns. The plains are analogous 

to the ridged unit on Mars [8] and interpreted to be 

regional volcanic plains subsequently deformed by ridge 

structure. 

In V-12, two units of pwr can be defined, both 

of which are younger than the shield plains (psh), with 

the lower unit (pwr1) mottled to radar bright and the 

upper unit (pwr2) radar dark. This is not consistent with 

the plains units mapped in adjacent quadrangles V-4 and 

V-13 [3] and may be a local stratigraphic relationship, 

where (pwr2) in V-12 is correlative with (pwr1) mapped 

regionally in surrounding quads. 

Wrinkle ridged plains material in V-11 is also 

consistently younger than psh but is difficult to divide 

into two consistent and well-defined units. In V-11, 

wrinkle ridged plains has been mapped as a complex 

unit consisting of regional radar dark to intermediate 

plains and local radar bright contributions from local 

volcanic centers. 

Lobate plains material (pl) and digitate plains 

material (pd) form local units, in both V-11 and V-12, 

primarily associated with mapped volcanic centers, 

including Hiei Chu Patera and an unnamed and newly 

mapped patera at 25°N, 115°E. These units are 

characterized by plains with sinuous to lobate to digitate 

radar bright patterns interpreted to be volcanic flow 

fields that postdate the emplacement of pwr. A flow field 

has also been identified in association with a cluster of 

small shields located between Shimti Tessera and 

Eurynome Corona at 27.5°N, 95°E. 

Streaked plains material (pst) in V-12 is 

interpreted to be aeolian aggradational or degradational 

resurfacing of the pre-existing plains terrain (pwr1) 

Impact craters have been mapped, where 

possible, by two units: undivided crater floor, wall, rim 

and continuous ejecta (c); and outflow deposits (cf). 

Several craters are characterized by radar dark material 

or a circular pattern of radar dark and bright material. 

In most cases, the coronae in both quads are 

defined solely by structural lineations; however, Boann 

Corona in V-12 and an unnamed and newly mapped 

corona-like structure at 27°N, 141° are partially 

delineated by mappable patches of densely lineated 

plains material (pdl). 

Observations of Akkruva Shield Plains, V-11 

and V-12. The Akkruva shield plains material is 

characterized by abundant small shield-shaped hills 

ranging from a few kilometers in diameter to 

approximately 20 km, and associated plains apparently 

formed by coalesced point-source eruptions. Ten (10) 

larger volcanic edifices, classified as intermediate 

volcanoes, occur within the Akkruva shield plains, but 

the majority of the hundreds to thousands of individual 

edifices are small and relatively consistent in diameterrange. Shields commonly occur in clusters, giving the 

unit a locally hilly texture. In fact, the preliminary map 

of V-12 called this unit “hilly mottled plains material.” 

Individual shields are radar dark or radar bright, circular 

features, with or without a central pit. At times, they are 

defined by a “halo” of flank material encircled by 

younger ridged plains material surrounding an individual 

edifice or by a network of structural ridges surrounding 

an edifice. Evidence for structural deformation after 

emplacement occurs in V-11 where a small fracture 

visibly cuts through one of the shield edifices. A cluster 

of shields at 37°N, 96°E in V-11 is clearly covered, but 

still visible in outline, beneath a radar bright surficial 

material associated with a dark “spot” impact crater. An 

opportunity to observe and test the differences between 

shield plains and shield fields also exists in V-11. One 

cluster of shields in the southwest corner of the quad has 

an associated flow field, but otherwise appears to be in 

the same stratigraphic position with respect to tessera as 

is the shield plains unit. 

The entire unit is extensive, crossing the 

boundary between V-11 and V-12, and covering much of 

Tilli-Hanum Planitia and eastern Niobe Planitia. In V12, it covers much of the region between 120° and 130°E 

for the entire latitude range of the quad and in V-11, it 

covers a wedge shaped region from 50°N, 105°E to 

25°N, 120°E and then extends along the entire southern 

boundary of the quad and into adjacent quadrangle V-23. 

Patches of shield plains occur in the same stratigraphic 

position, always above the basal terrains, in western V11 and eastern V-12. Similar map relations exist across 

V-3, V-4, V-13, V-23 and V-24 [3,7]. Mapping of these 

patches provides evidence for a regional shield plains 

unit in this particular region of Venus that is extensive 

and continuous, but intermittently exposed beneath 

younger plains units. 

V-11 and V-12 provided the original definition 

and type example of the unit that has been subsequently 

also mapped by others as shield plains material. The 

completed geologic maps of V-11 and V-12 can now 

provide additional data to better understand this unit. 

[1] Barsukov&others (1986) JGR 91; Basilevsky&others (1986) JGR 91 [2] 

Solomon&others (1992) JGR 91 [3]Ivanov&Head (2004) Geol Map of V-4, 

I-2792; Ivanov&Head (2005), Geol Map of V-13, I-2870; Ivanov&Head (in 

press) Geol Map of V-3 [4]Guest et al. (1992) JGR 97; Head et al. (1992)

JGR 97; Crumpler et al. (1989) Sci 246; Aubele&Slyuta (1990) EMP, 

50/51; Garvin&Williams (1990), GRL17; Aubele&Crumpler (1992) 

International Colloquium on Venus, LPI Contrib. 789; Aubele (1993) 

LPSC24; Crumpler et al (1997) in Venus II UofA Press; Crumpler&Aubele 

(2000) in H. Sigurdsson et al. Encyl of Volcanology Academic Press 

[5]Schaber (1988) LPSC19 [6]Aubele (1997) GSA Abst. 29, no. 6, A-138; 

Aubele (1996) LPSC 27, 49; Aubele (1995) LPSC 26, 59; Aubele (1994) 

LPSC 25, 45; Aubele (1993) GSA Abst. 25, A-221 [7]Hansen (2005) GSA 

Bull 117, no.5/6; Hansen (2003) LPSC 34; Hansen (in press) Geol Map of 

V-23; Lang&Hansen (in press) Geol Map of V-24 [8] Scott&Tanaka (1986) 

Geologic Map of the Western Hemisphere Mars, USGS Map I-1802-A
GEOLOGY OF THE WESTERN PART OF THE V-36 THETIS REGIO QUADRANGLE. A. T. Basilevsky1,2 and J. W. 

Head2, 1Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, Moscow, Russia, atbas@geokhi.ru, 2Department 

of Geological Sciences, Brown University, Providence RI 02912 USA.

Introduction: This work is a continuation of the photogeologic mapping of the V-36 quadrangle, that is part of 

the USGS 1:5M planetary mapping project [1]. Here we 

report on mapping of the western half of this quadrangle.

Mapping Results: As a result of mapping, eleven material stratigraphic units and three structural units have been 

identified and mapped. The material units include (from 

older to younger): tessera terrain material (tt), material of 

densely fractured plains (pdf), material of fractured and 

ridged plains (pfr), material of shield plains (psh), material 

of plains with wrinkle ridges (pwr), material of smooth 

plains of intermediate brightness (psi), material of radardark smooth plains (psd), material of lineated plains (pli),

material of lobate plains (plo), material of craters having no 

radar-dark haloes (c1), and material of craters having clear 

dark haloes (c2).

The morphologies of the material units in the study area 

are generally similar to those observed in other regions of 

Venus [2]. The youngest units are lobate plains (plo) which 

here typically look less lobate than in other areas of the 

planet. Close to them in age are smooth plains which are 

indeed smooth and represented by the two varieties mentioned above. Lineated plains (pli) are densely fractured in 

a geometrically regular way. Plains with wrinkle ridges, 

being morphologically similar to those observed in other 

regions, here occupy unusually small areas. Shield (psh) 

plains here are also not abundant. Locally they show wrinkle ridging. Fractured and ridged plains (pfr), which form 

the so-called ridge belts in other regions, are observed as 

isolated areas of clusters of ridged plains surrounded by 

other units. Densely fractured plains (pdf) are present in 

relatively small areas in association with coronae and corona-like features. Tessera terrain (tt) is dissected by structures oriented in two or more directions. Structures are so 

densely packed that the morphology (and thus nature) of 

the precursor terrain are not known.

Structural units include tessera transitional terrain (ttt), 

fracture belts (fb) and rifted terrain (rt). Tessera transitional 

terrain was first identified and mapped by [4] as areas of 

fractured and ridged plains (pfr) and densely fractured 

plains (pdf) deformed by transverse faults that made it formally resemble tessera terrain (tt). The obvious difference 

between units tt and ttt is the recognizable morphology of 

precursor terrain of unit ttt. Fracture belts are probably 

ancient rift zones [3]. Rifted terrain (rt), as in other regions 

of Venus, is so saturated with faults that according to the 

recommendation of [1] it should be mapped as a structural 

unit. 

The lower crater material unit is represented by 5 craters, one of which, Mariko, is superposed on rifted terrain. 

The upper unit is represented by one splotch in the northwestern part of the mapped part of quadrangle.

Conclusions: Our mapping analysis and results show 

that although the mapped units are generally similar to 

those observed in other regions of the planet, some of them 

have unusual areal abundances that imply unique aspects of 

the geologic history of this region. In particular, the unusually high abundance of rifted terrain (rt) and tessera transitional terrain (ttt) have interesting implications and require 

additional studies.

References: [1] Tanaka K. (1994) USGS Open File Report 

94-438. [2] Basilevsky A. T. & Head J. W. (2000) Planet. Space 

Sci., 48, 75-111. [3] Banerdt et al. (1997) in Venus II, U. Arizona 

Press, 901-930. [4] Ivanov M. A. & Head J. W. (2001) JGR, 106, 

17,515-17,556. 

GEOLOGIC MAPPING OF ISABELLA QUADRANGLE (V-50) AND HELEN PLANITIA, VENUS. Leslie 

F. Bleamaster III, Planetary Science Institute, corporate address - 1700 E. Ft. Lowell Rd., Suite 106, Tucson, 

AZ 85719; mailing - 3635 Mill Meadow Dr., San Antonio, TX 78247; lbleamasPSI@satx.rr.com 

Introduction. The Isabella Quadrangle (25-

50°S, 180-210°E – Figure 1) lies to the south of 

the eastern extent of the Diana-Dali Chasmata 

system and Atla Regio, which contains the 

volcanoes Sapas, Maat and Ozza Montes. 

Isabella Quadrangle is host to numerous coronae 

and small volcanic centers (paterae and shield 

fields), focused (Aditi and Sirona Dorsa) and 

distributed (penetrative north-south trending 

wrinkle ridges) contractional deformation, and 

radial and linear extensional structures, all of 

which contribute materials to and/or deform the 

expansive surrounding plains (Nsomeka and 

Wawalag Planitiae). Specific questions posed 

for geologic mapping of the V-50 quadrangle 

include: 1) What and where are the source 

locations for the regionally dominant plains 

materials (e.g., coronae, paterae, shield fields, 

rifts and fissures)? 2) What is the relationship, if 

any, between focused (deformation belts) and 

distributed (wrinkle ridges) contractional strain 

and local/regional volcanism? 3) What role does 

structural reactivation play in deformation belt 

and wrinkle ridge development? 4) What are the 

spatial and temporal relationships between 

craters with outflows and volcanic constructs, 

and to what extent are crater outflows directly 

related to impact processes versus post-impact 

modification? 

Figure 1. V-50, Isabella Quadrangle (25-50°S, 180-

210°E). Mapping in progress. 

In addition to V-50, this project is mapping 

Helen Planitia at 1:10M-scale (0-57°S/180-

300°E – Figure 2), which covers over 70 million 

square kilometers (approximately 1/8th) of the 

surface of Venus, expresses 10 kilometers of 

relief from the highlands of Atla and Phoebe 

Regiones to the depths of Parga Chasmata and 

vast Helen lowlands, and exposes areas 

representing the entirety of Venus’ preserved 

geologic history as determined by Average 

Surface Model Ages (ASMA) [1 and 2]. 

Geologic mapping will afford the opportunity to 

synthesize previous mapping efforts and place 

existing geologic interpretations V-39, V-40, 

and V-59 [3 - 5], and the diversity of other 

features into a coherent geologic history in order 

to help address the geodynamical and thermal 

evolution of the region across several 

physiographic provinces, a substantial number 

of which may be indicative of recent and/or 

present activity (three volcanic rises, two major 

chasmata, hundreds of coronae and paterae, and 

thousands of small volcanic constructs) [1, 6, 

and 7]. 

Isabella Quadrangle (V-50). Isabella 

Quadrangle is dominated by regional plains 

(blues above), which have tentatively been 

divided into two members (regional plains, 

members a and b) based on unimpressive 

backscatter variations, which result in very 

inconsistent mottled characteristics of both 

members. The regional plains have been 

deformed by penetrative north-trending wrinkle 

ridges and east-striking fractures, and several 

broad north-trending topographic undulations, 

suggesting that both members were in place 

prior to east-west shortening. Most noteworthy 

is that member b (lighter backscatter, light blue 

above) lacks channel forms (canali), and is 

found on the trailing side of some wind blown 

features and topographic obstacles. It will be 

important to comprehensively address the spatial 

relationship between these two regional plains 

members and the preservation of channel forms, 

shield edifices, wrinkle ridges and their 

orientations, wind-blown features, all SAR 
cycles, topography, reflectivity, and emissivity. 

Further evaluation will help determine if the 

member a and b boundary as currently 

delineated is a true unit contact or just a radar 

facies boundary related to surficial deposits of a 

mobile material. 

Helen Planitia. Current efforts are focused on 

mapping the distribution and orientation of 

structural trends and flow morphologies, and the 

demarcation of flow unit boundaries based on 

primary and secondary surface morphologies. 

To date, several hundred radial and circular 

features (both digitate and lobate flow fields and 

fracture, fault, and ridge suites) have been 

documented and match closely the existing 

coronae and/or volcanic landform databases [8 

and 9]; however, not all correspond directly with 

defined Type I or Type II coronae, or other 

named volcanic landforms. 

The majority of these radial/circular features 

lie within a few hundred kilometers of the Parga 

Chasmata rift system (see below), marking a 

southeast trending line of relatively young 

volcano-tectonic activity. Although some very 

localized embayment and crosscutting 

relationships display clear relative age relations 

between centers of activity, the majority of 

Parga Chasmata volcanism and tectonism 

overlaps in time from Atla Regio in the west to 

Themis Regio in the east, extending ~10,000 

linear kilometers. Atla and Themis Regiones 

(rift-dominated and coronae-dominated volcanic 

rises, respectively [10]) lie in characteristically 

different ASMA regions (Atla-young; Themisintermediate); however, preliminary mapping 

has not revealed any significant ‘stratigraphic’ 

support for these model age differences. 

References: [1] Phillips, R.J. and Izenberg, 

N.R. (1995) Geophys. Res. Lett., 22, 1517-1520. 

[2] Hansen, V.L. and Young, D.A. (in press) 

GSA Special Paper. [3] Brian, A.W. et al., 

(2005) USGS Sci. Inv. Map 2813. [4] Chapman, 

M.G. (1999) USGS Geo. Inv. Sers. I-2613. [5] 

Johnson, J.R. et al., (1999) USGS Geo. Inv. Sers. 

I-2610. [6] Herrick R.R., and Phillips, R.J. 

(1994) Icarus, 111, 387-416. [7] Price and 

Suppe (1994) Nature, 372, 756-759. 

[8] Crumpler L.S. et al., (1997) in Venus II, 697-

756. [9] Stofan E.R. et al., (2001) Geophys. Res. 

Lett., 28, 4267-4270. [10] Smrekar, S.E., et al., 

(1997) in Venus II, 8445-878. 

Figure 2. Preliminary geologic map of the Helen Planitia Regional Study Area (0-57°S, 180-300°E; 1:10M-scale). 

Volcanic flows and deformation related to Parga Chasmata dominate the eastern portion of the map area (browns, 

reds, oranges, and yellows) and embay/crosscut Phoebe Regio (green) in the northeast. Background blue has not 

been mapped at this scale. Red box to the west delineates 1:5M-scale V-50 quadrangle boundary (Figure 1). 
GLOBAL MAPPING OF VENUS' RIBBON TESSERA TERRAIN: PRELIMINARY RESULTS. 

V. L. Hansen1

, T. Nordberg1 and, I. López2, 1Department of Geological Sciences, University of Minnesota 

Duluth, Duluth, MN 55812; 2

Área de Geología, Escuela Superior de Ciencias Experimentales y 

Tecnología. Universidad Rey Juan Carlos, 28933. Móstoles, Madrid, Spain (vhansen@d.umn.edu) 

Introduction: Venus displays a rich variety 

of exogenic and endogenic structures that 

provide clues to its history. Currently, widely 

accepted hypotheses that dominate textbooks 

and popular science call for a globally extensive 

catastrophic volcanic flooding event to bury 

100-80% of Venus’ surface with 1-3 km lava in 

10 to 100 m.y. time. Flooding would create a 

crater-free global surface in the form of lowland 

plains, effectively erasing (through burial) the 

recorded geologic history prior to flooding at 

~750 Ma. Subsequent to flooding, colliding 

bolides created the suite of ~970 well preserved 

impact craters, which display a near random 

distribution across Venus. Catastrophic volcanic 

resurfacing hypotheses call for an ~1-3 km thick 

layer in order to bury pre-existing impact 

craters; this prediction is tested through global 

mapping of ribbon tessera terrain, and 

construction of isopach surfaces. Ribbon tessera 

terrain reportedly formed as a globally extensive 

layer prior to catastrophic flooding. 

Such a map will allow us to identify global 

patterns of tessera-terrain outcrops and fabric 

patterns in order to identify local, regional or 

global patterns. Such patterns will provide clues 

to tessera terrain formation. In addition this 

database will allow us to test such hypotheses as 

global to near global catastrophic resurfacing as 

tessera terrain should form the basal layer for 

widespread flooding. Ribbon-terrain 

characterizes highland plateaus, but it also 

occurs in small to large kipukas scattered across 

much of the Venusian lowlands. 

Method: Using NASA Magellan SAR 

images we are creating a geologic map of ribbon 

tessera terrain at a global scale. Tessera terrain 

outcrops and structural patterns (ribbons and 

folds) are mapped across individual 

georeferenced VMap quadrangles using linked 

data files in an Adobe Illustrator environment. 

We transfer the results to the ArcGlobe GIS 

environment using Map Publisher. Once in the 

ArcGlobe GIS environment data is projected 

global allowing us to discount projection issues 

and observe outcrop and structural patterns 

across VMap boundaries. In addition the data 

can be compared to other global data sets. 

Data layers include USGS VMap SAR 

image bases, and synthetic stereo images 

(created by combining USGS SAR images and 

Magellan altimetry using macros developed by 

D.A. Young). SAR and synthetic stereo images 

are consulted in both normal and inverted 

modes. Most VMap quadrangles were examined 

by each of the co-authors for ribbon tessera 

terrain identification. To date we do not have 

SAR data for V-62, the south pole region, and 

we lack synthetic stereo for V-1, the north pole 

region. Despite the lack of synthetic stereo data 

for the north pole, we have been able to conduct 

ribbon tessera terrain mapping and this region is 

included on the global map. 

The global tessera map is a work in 

progress. Tessera terrain on all VMAPs have 

been identified and transferred to the ArcGlobe 

environment. Numerous boundary mismatches 

are currently being addressed, while the map of 

ribbon and fold trends is in progress. About 

twenty five percent of the VMap quadrangles 

have structural trends mapped, with the northern 

hemisphere receiving the most attention to date. 

Results to date: Perhaps the most striking 

result is the uneven global distribution of ribbon 

tessera terrain, with the second most striking 

result being the detailed patterns that might 

emerge from this style of mapping. 

Tessera terrain is distributed across the 

northern hemisphere in large to small outcrops. 

The region of Lakshmi Planum marks the single 

largest region that is relatively tessera free (we 

are still debating whether small exposures within 

Lakshmi represent ribbon tessera terrain or not). 

In places the outcrops mark bead-like necklaces 

tracing out arcs and circular features 1200-1800 

km in diameter. Elsewhere tessera outcrops as 

quite large extensive regions. Despite the high 

concentration of tessera terrain only Fortuna and 

Tellus Tesserae occur across a north polar 

centered view, as recognized crustal plateaus. 

The southern hemisphere view is strikingly 

different. Crustal plateau Alpha Regio lies along 

1
the perimeter of a south pole centered global 

view, and elsewhere tessera terrain occurs as 

small outcrops in chains of clusters, but 

representing only a small percent of the southern 

hemisphere surface. 

The eastern and western hemisphere views 

are also quite different from one another. The 

eastern hemisphere (1-180°) is dominated by 

crustal plateaus Tellus Tesserae, and W. Ovda, 

E. Ovda and Thetis Regiones, and an extensive 

circular tract of ribbon tessera west of W. Ovda. 

Elsewhere tessera exposures define arcs to 

circular chains, as well as scattered to clustered 

groups. Although exposures are more dominate 

in the northern hemisphere in this view, there are 

exposures across the southern hemisphere. The 

western hemisphere (180-360°) lacks the 

obvious crustal plateaus and associated huge 

tracts of tessera terrain; tessera chains and 

numerous small, scattered and regionally 

dispersed outcrops of tessera mark this view. 

Globally three styles of outcrop patterns 

emerge from the data to date: 1) large quasicircular tracts of tessera similar to crustal 

plateaus, although not preserved as elevated 

plateaus; 2) long curvilinear arcs, 100s to 1000+ 

km long with varying widths up to 250-400 km; 

the arcs in general have long aspect ratios, in 

strong contrast with the more blob-like tracts; 

and 3) small scattered, yet grouped exposures as 

small as tens of km2

, yet occurring across 

regional areas covering over 2 to 3 million km2

. 

Across the global view cross-cutting 

relations seem likely given the intersecting or 

overlapping nature of the outcrop arcs. The 

addition of structural trends to the global map 

will provide further constraints to identify 

temporal patterns and relations that might exist. 

Structural mapping to date indicates that tessera 

structural fabrics generally parallel the arcuate 

outcrops with fold ridges parallel to the arc, and 

ribbon trends typically normal to the arc. Across 

the dispersed small outcrops, structural patterns 

are consistent between outcrops across extensive 

regions. 

Although SAR data strictly constrain only 

surface geometry, the patterns preserved in SAR 

images can be used to construct threedimensional views in the same way that 

terrestrial map patterns reflect subsurface rock 

patterns. The dispersed nature of small isolate 

outcrops, taken together with the detailed 

digitate contact between tessera terrain and 

cover material can allow us to project regional 

subsurface slopes of tessera terrain and cover 

material. Based on relations gleaned from 

dispersed outcrops within V-23, we calculated a 

moderately steep slope between underlying 

ribbon tessera and cover material. We used a 

particularly steep slope in order to maximize the 

estimate of cover material. Using this slope 

(0.4°) we created global isopach surfaces 

marking the projected location of 1 km and 3 

km-thick cover layer above the ribbon tessera 

terrain. In most places the slopes are 

significantly shallower, and thus the isopach 

surfaces represent a conservative view of those 

regions of Venus that could harbor cover above 

ribbon tessera thicker than 1 km (and 3 km). 

Given that volcanic catastrophic resurfacing 

hypotheses call for 1-3 km thick flows emplaced 

above ribbon tessera terrain, this analysis should 

provide a valid test of the catastrophic volcanic 

resurfacing. 

Isopach surfaces for 1 and 3 km of cover 

above tessera terrain indicate that portion and 

distribution of the surface of Venus that could 

harbor buried impact craters would not result in 

Venus’ current near random impact crater 

distribution. Visual inspection indicates that less 

than 50 percent of the northern hemisphere 

(polar view) could have >1 km thick cover 

above a basal tessera terrain layer (tessera terrain 

need not exist everywhere in the subsurface, in 

this case the ‘cover’ would exceed 1 km); 

similarly the eastern hemisphere view indicates 

>50 percent surface covered by 1-km flows. In 

contrast, the southern and western hemispheres 

show significantly more burial possible, with 

perhaps 90 percent of the southern hemisphere 

(south pole view) capable of burial beneath 1-

km, and 60-70 percent of the western 

hemisphere. The western hemisphere includes 

volcanic rises Atla, Beta and Themis Regiones, 

which might well contribute to more significant 

burial of basal tessera terrain. Small isolated 

exposures of ribbon tessera terrain across this 

region suggest that tessera originally existed 

across large regions, and has been subsequently 

buried or otherwise removed. Both the low 

amounts of regions in the northern and eastern 

hemisphere that could be buried, and the striking 

2
global differences indicate that catastrophic 

resurfacing hypotheses are incompatible with the 

global ribbon tessera terrain mapping. Mapping 

of structural trends within ribbon terrain may 

provide critical clues to tessera terrain 

formation. Ribbon and fold trends mapped to 

date indicate coherent patterns across and 

between isolated tessera outcrops, providing 

strong evidence that Venus likely preserves a 

geologic record (and history) that extends 

further back in time than widely appreciated. 

 

3
GLOBAL GEOLOGICAL MAP OF VENUS: PRELIMINARY RESULTS. M. A. Ivanov, Vernadsky Institute, 

RAS, Moscow, Russia (Mikhail_Ivanov@brown.edu).

Introduction: The Magellan SAR images provide 

sufficient data to compile a geological map of nearly the 

entire surface of Venus. Such a global and selfconsistent map would serve as an important document 

to address many key questions in the geologic history of 

Venus. 1) What units/structures characterize the surface 

[1-3]? 2) What volcanic/tectonic regimes do they 

represent [4-7]? 3) Did these regimes occur globally or 

locally [8-11]? 4) What are the relative time 

relationships among the units [8]? 5) Are these 

relationships consistent regionally or globally [8-10]? 6) 

What is the absolute timing of formation of the units 

[12-14]? 7) What is the history of the long-wavelength 

topography and geoid? 7) What model(s) of heat loss 

and lithospheric evolution [15-21] does this history 

represent? The ongoing USGS program of Venus 

mapping has already resulted in a series of published 

maps at the scale 1:5M [e.g. 22-30]. These maps have a 

patch-like distribution, however, and are being compiled 

by authors with different mapping philosophies that are 

not always in agreement with each other in terms of 

mapped units and their relationships. Here the 

preliminary results of global geological mapping of 

Venus at the scale 1:10M is presented, representing the 

current status of a global mapping project. The map 

represents a contiguous area extending from 82.5oN to 

22.9oS and comprises ~70% of the planet. The new map 

permits one to address some of the questions raised 

above.

Mapping procedure: For the initial mapping 

analyses, images of high resolution (C1-MIDR and FMIDR) were used to define units [1,9,11]. The map was 

then compiled on C2-MIDR sheets, the resolution of 

which permits identifying the basic characteristics of 

previously defined units. The higher resolution images 

were again used during the mapping to clarify geologic 

relationships. When the map was completed, its quality 

was checked using published USGS maps [e.g., 22-30] 

and the catalogue of impact craters [31]. The results 

suggest that the mapping on the C2-base provided a 

high-quality map product.

Units and structures: A set of material units and 

tectonic structures describes the geological 

configurations throughout the map area (Fig. 1). The 

complete stratigraphic column consists of the following 

units (from older to younger): Tessera (t) displays 

multiple sets of tectonic structures. Densely lineated 

plains (pdl) are dissected by numerous subparallel 

narrow and short lineaments. Ridged plains (pr) 

commonly form elongated belts of ridges. Mountain 

belts (mt) resemble ridge belts and occur around 

Lakshmi Planum. Shield plains (psh) have numerous 

small volcanic edifices on the surface. Regional plains

were divided into the lower (pr1) and the upper (pr2) 

units. The lower unit has uniform and relatively low 

radar albedo; the upper unit is brighter and often forms 

flow-like occurrences. Shield clusters (sc) are 

morphologically similar to psh but occur as small 

patches that postdate regional plains. Smooth plains (ps) 

have uniform and low radar albedo and occur near 

impact craters and at distinct volcanic centers. Lobate 

plains (pl) form fields of lava flows that are typically 

undeformed by tectonic structures and are associated 

with major volcanic centers.

Specific structural assemblages accompany the 

material units: Tessera-forming structures (ridges and 

grooves), ridge belts, groove belts (structural unit gb), 

wrinkle ridges, and rift zones (structural unit rt). The 

tessera-forming structures and ridge belts predate vast 

plains units such as psh and rp1. Groove belts postdate 

tessera and ridge belts. Shield plains and regional plains 

mostly embay groove belts. In places, groove belts 

appear to form contemporaneously with the vast plains 

units. Wrinkle ridges deform all material units predating 

smooth and lobate plains. Rift zones appear to be 

contemporaneous with sc, pl, and ps and cut older units.

Crater statistics: Two factors, the atmosphere 

screening [32-34] and the observational bias [35], 

appear to affect the statistics of the smaller (<16 km) 

craters. For the larger craters these factors are negligible 

and the larger craters were used to estimate the crater 

density on mapped units. The shape and size of 

occurrences of units may also affect the crater statistics 

on Venus where the total number of craters is small. To 

minimize influence of this factor the crater density on 

large and contiguous units that have quasiequidimensional occurrences was estimated. These units 

are: t, psh, rp1, rp2, pl, and rt; together, they cover ~84% 

of the surface. The mean densities (craters per 106km2) 

of craters on these units are as follow: tessera: 1.046 

(±0.158, one σ); shield plains: 1.004 (±0.126); regional 

plains, lower unit: 0.982 (±0.103); regional plains, 

upper unit: 0.614 (±0.140); lobate plains: 0.547 

(±0.144); rifts: 0.609 (±0.173). The mean density of 

craters in the map area (all units) is 0.938 (±0.054). If 

the mean crater density corresponds to the mean surface 

age, T [19], then the ages of the above units as fractions 

of T are: tessera: 1.11T, shield plains: 1.07T, regional 

plains, lower unit: 1.05T, regional plains, upper unit:

0.67T, lobate plains: 0.58T, rifts: 0.67T.

These results are consistent with the mapped 

stratigraphic relationships and indicate that there are 

two groups of units: The older units (t, psh, rp1) are 

densely clustered around 1.1T and the younger units 

(rp2, pl, rt) were formed around 0.6T. The exposed area 
of the older units is ~59% of the map area (the true area 

must be larger) and the younger units cover ~25% of the 

surface. Depending upon the estimates of the absolute 

value of T (from 750 Ma [36] through 500 Ma [37] to 

300 Ma [38]), it is possible to estimate the duration of 

specific periods in the observable geologic history of 

Venus. The older units appear to form during a 

relatively short time, from 45 m.y (T = 750 Ma) to 18 

m.y (T = 300 Ma). The minimum integrated resurfacing 

rate (both volcanic and tectonic) at this time was from 

~4.2 to ~10.4 km2/y. The younger units spanned a 

longer time and the integrated resurfacing rate during 

their formation was from ~1.2 to ~3.0 km2/y. The large 

time gap (from 285 to 114 m.y.) between the two groups 

of units and the significant drop in the resurfacing rates 

suggest that the older and the younger units correspond 

to two different geodynamic regimes that were probably 

related to different patterns of mantle convection and 

lithospheric properties.

References: 1) Basilevsky, A.T. and J.W. Head, PSS, 43, 

1523, 1995; 2) Basilevsky, A.T. and J.W. Head, PSS, 48, 75, 

2000; 3) DeShon, H.R. et al., JGR, 105, 6983, 2000; 4) Head, 

J.W. et al., JGR, 97, 13153, 1992; 5) Solomon, S.C. et al., 

JGR, 97, 13199, 1992; 6) Squyres, S.W. et al., JGR, 97, 

13579, 1992; 7) Stofan, E.R. et al., JGR, 97, 13347, 1992; 8) 

Guest, J.E., and E.R. Stofan, Icarus, 139, 56, 1999; 9) 

Basilevsky, A.T., et al., in: Venus II, S.W. Bougher et al. eds., 

Univ. Arizona Press 1047, 1997; 10) Head, J.W. and A.T. 

Basilevsky, Geology, 26, 35, 1998; 11) Ivanov, M.A. and J.W. 

Head, JGR, 106, 17515, 2001; 12) Price, M. and J. Suppe,

Nature, 372, 756, 1994; 13) Price, M. et al., JGR, 101, 4657, 

1996; 14) Namiki, N. and S.C. Solomon, Science, 265, 929, 

1994; 15) Parmentier, E.M. and P.C. Hess, GRL, 19, 2015, 

1992; 16) Head, J.W. et al., PSS, 42, 803, 1994; 17) Turcotte, 

D.L., JGR, 98, 127061, 1993; 18) Arkani-Hamed, J. and M.N. 

Toksoz, PEPI, 34, 232, 1984; 19) Solomon, S.C, LPSC 

(Abstr.), XXIV, 1331, 1993; 20) Phillips R.J. and V.L. Hansen, 

Science, 279, 1492, 1998; 21) Solomatov, S.V. and L.-N. 

Moresi, JGR, 101, 4737, 1996; 22) Bender, K.C., et al., USGS 

Map I-2620, 2000; 23) Rosenberg, E. and G.E. McGill, USGS 

Map I-2721, 2001; 24) Ivanov, M.A. and J.W. Head, USGS 

Map I-2684, 2001; 25) Ivanov, M.A. and J.W. Head, USGS 

Map I-2792, 2003; 26) Ivanov, M.A. and J.W. Head, USGS 

Map 2870, 2005; 27) Bridges, N.T. and G.E. McGill, USGS 

Map I-2747, 2002; 28) Campbell, B.A. and P.G. Campbell, 

USGS Map I-2743, 2002; 29) Hansen, V.L. and H.R. DeShon, 

USGS Map I-2752, 2002; 30) Brian, A.W., et al., USGS Map 

2813, 2005; 31) Schaber, G.G.et al., USGS OFR 98-104, 1998; 32) Phillips, R.J., et al., JGR, 97, 15923, 1992; 33) 

Ivanov, B.A., et al., JGR , 97, 16167, 1992; 34) Herrick, R.R. 

and R.J. Phillips, Icarus, 112, 253, 1994; 35) Ivanov, M.A. 

and A.T. Basilevsky, GRL, 20, 2579, 1993; 36) McKinnon, 

W.B., et al., in: Venus II, S.W. Bougher et al. eds., Univ. 

Arizona Press, 1014, 1997; 37) Schaber, G.G., et al., JGR, 97, 

13257, 1992; 38) Strom, R.G., et al., JGR, 99, 10899, 1994.

Fig. 1. Geological map of Venus. Scale is ~1:10M; 

Lambert equal-area projection.
GEOLOGIC HISTORY OF THE LAVINIA PLANITIA/LADA TERRA REGION, VENUS: RESULTS OF 

MAPPING IN THE V-55, V-61, AND V-56 QUADRANGLES. M. A. Ivanov1,2 and J. W. Head2; 1Vernadsky 

Institute, RAS, Moscow 119991, Russia (mikhail_ivanov@brown.edu), 2Brown University, Providence, RI 02912, 

USA, 3 (james_head@brown.edu).

Introduction: Lada Terra (~300-90oE, 55-80oS, V61 and V-56) is a region of midlands (0-2 km above 

MPR) that is dominated by a large dome-shaped structure. Lada hosts many coronae interconnected by belts of 

graben and large complexes of lava flows [1-5]. The 

lowland of Lavinia Planitia (~330-0oE, 25-55oS, V-55) is 

to the N of Lada Terra. Deformational belts of ridges and 

grooves and vast mildly deformed plains characterize the 

floor of Lavinia [6]. The pattern of deformation, topography, and gravity signature are consistent with mantle 

downwelling under Lavinia [6-8] and with mantle upwelling in the region of Lada Terra [9]. Thus, Lada Terra 

and Lavinia Planitia apparently represent contrasting 

geodynamic provinces, the history of which may be coupled [4]. Here we summarize results of the geological 

mapping in three (V-55 [10], V-61 [11], and V-56, in 

progress) quadrangles that cover the Lavinia/Lada region. The main goal of our study was to establish the

timing and sequence of events during formation and evolution of these regions and reconstruct the major episodes of Lada Terra/Lavinia Planitia geologic history.

Topographic configuration of Lavinia Planitia 

and Lada Terra: Lavinia Planitia is a large basin ~1500 

km across and is as deep as ~1.5 km below MPR. The 

deepest portion of the basin is at its S edge. The major 

portion of Lada Terra is within midlands. The most 

prominent topographic feature of Lada Terra is a broad 

(~1000 km) symmetric swell, the summit of which is at 

elevation ~3.5 km. Two regional-scale topographic features (1000s of km long, 100s of km wide, 1-2 km amplitude), an elongated depression, and a topographic ridge, 

concentrically outline the swell of Lada from the north 

and east.

Units, structures, and their stratigraphic relationships: In our mapping, we used traditional methods 

of unit definition [12,13] modified for radar data [14]. 

On this basis [14-18], we defined units and structures 

and mapped relations between them using F/C1-MIDR 

images and altimetry data. All mapped quadrangles display similar sets of material and tectonic units. Consistent age relationships allow broad stratigraphic correlations among the units. The oldest unit is tessera (t), 

which is deformed by intersecting ridges and grooves 

[19-25] and embayed by less deformed materials. 

Densely lineated plains (pdl) are cut by densely packed 

lineaments and embay tesserae where these units are in 

contact. Broad (5-10 km) ridges arranged in linear belts 

commonly deform ridged plains (pr). The belts predominantly occur on the floor of Lavinia Planitia. Abundant small (a few km) shield-like features characterize 

shield plains (psh). The unit occurs mostly in Lavinia 

Planitia where it embays ridged plains. Regional plains 

(rp) consist of two units. The lower unit (rp1) has relatively low radar backscatter and preferentially occurs in 

the lowlands surrounding Lada Terra. The upper unit 

(rp2) has a higher radar albedo and, sometimes, lobate 

boundaries. Both units embay shield plains. Lobate 

plains (pl) have lobate and digitate boundaries and internal flow-like features. Smooth plains (ps) display 

morphologically smooth surfaces with uniform radar 

albedo. Shield clusters (sc) form groups of small shields 

similar to those of psh but with flow-like features. 

Materials of ps, pl, and sc preferentially occur in central 

Lada and embay the majority of tectonic structures.

The older contractional structures in the map area 

are the ridges that deform ridged plains (pr). Shield 

plains and regional plains embay the ridges. The younger 

contractional features are wrinkle ridges that deform 

regional plains and other older units and are embayed by 

ps and pl. Fractures and graben in the studied region are 

typically collected in zones of extensional structures, 

groove belts and rift zones. Groove belts (gb) preferentially occur on the floor of Lavinia Planitia where they 

cut ridges of the unit pr and are embayed by shield plains 

and regional plains. Rift zones (rt) are concentrated in 

Lada Terra and appear to be contemporaneous with the 

youngest plains units (pl, ps, sc).

Discussion and conclusions: The V-55, V-61, and 

V-56 quadrangles cover a region that consists of two 

provinces, Lavinia Planitia and Lada Terra, contrasting 

in gravity, topography, and overall geologic history. The 

deformational zones of ridge belts populate the floor of 

Lavinia and the most prominent belts preferentially occur at the deepest portion of the lowland. The important 

characteristic of the basin is the absence of young deformation and volcanic materials postdating wrinkle 

ridges. The general topographic configuration of Lavinia 

Planitia and the radial pattern and topographic position 

of the belts of ridges are consistent with formation of the 

belts due to subsidence of the Lavinia basin [7]. The 

stratigraphic position of the belts implies that the subsidence has largely occurred relatively early and the topographic asymmetry of Lavinia suggests that the locus 

of the subsidence was near its S and E edges. The vast 

plains (psh, rp1, and rp2) were emplaced on the floor of 

the lowland when it already was largely formed.

In contrast to Lavinia, Lada Terra is an elevated region dominated by the swell and characterized by abundant young volcanism (pl) and young extensional deformation (rt). The summit of the swell is one of the 

most important sources of young lavas that flow down 

the slopes of the swell [12,26]. Magellan gravity data 
[27,28] show that the swell is characterized by significant geoid height (~40 m). The geological, topographic, 

and gravity characteristics are consistent with mantle

upwelling [9] in central Lada. The stratigraphic position 

of the most abundant units in Lada Terra (pl) means that 

this latest upwelling largely postdated the subsidence in 

Lavinia Planitia.

The geologic history of the region of Lavinia Planitia and Lada Terra appears to consist of two major 

phases. The earlier phase corresponds to formation of 

the vast basin in Lavinia, development of deformational 

belts on its floor, and near-contemporary formation of 

marginal groove belts. Later, during the phase of broad 

updoming, massive volcanism and extensional tectonics 

occurred in Lada Terra largely postdating formation of 

Lavinia and the groove belts. The close geographic position of Lavinia Planitia and Lada Terra, their overall 

topographic configuration, and general sequence of 

events in these regions suggest a genetically linked evolution [4]. In this model, the downwelling in Lavinia 

occurred together with marginal extension in Lada, followed by younger rifting and volcanism in Lada Terra.

References: 1) Stofan, E.R. et al., JGR, 97, 13347, 1992; 2) 

Crumpler, L.S. and J. Aubele, in: Encycl. of Volcanoes, 727, 

2000; 3) Roberts, K.M., et al., JGR, 97, 15991, 1992; 4) 

Magee, K.M. and J.W. Head, JGR, 100, 1527, 1995; 5) Baer, 

G. et al., JGR, 99, 8355, 1994; 6) Squyres, S.W. et al., JGR, 

97, 13579, 1992; 7) Bindschadler, D.L. et al., JGR, 97, 13495, 

1992; 8) Simons, M., et al., GJI, 131, 24, 1997; 9) Kiefer, 

W.S. and B.H. Hager, JGR, 96, 20947, 1991; 10) Ivanov, 

M.A. and J.W. Head, USGS Geol. Inv. Ser., Map I-2684,

2001; 11) Ivanov, M.A. and J.W. Head, USGS Geol. Inv. Ser.,

2006; 12) Code of Stratigraphic Nomenclature, AAPGB, 45, 

645, 1961; 13) Wilhelms, D.E., in: Planetary Mapping, 208, 

1990; 14) Tanaka, K.L., USGS OFR 94-438, 50, 1994; 15) 

Basilevsky, A.T. and J.W. Head, EMP, 66, 285, 1995; 16) 

Basilevsky, A.T. and J.W. Head, PPS, 43, 1523, 1995; 17) 

Basilevsky, A.T. et al., in: Venus II 1047-1086, 1997; 18) 

Ivanov, M.A. and J. W. Head, JGR, 106, 17515, 2001; 19) 

Barsukov, V.L. et al., JGR, 91, D399, 1986; 20) Basilevsky, 

A.T., et al., JGR, 91, D399, 1986; 21) Bindschadler, D.L. and 

J.W. Head, JGR, 96, 5889, 1991; 22) Sukhanov, A.L., in:

Venus Geology, Geochemistry, and Geophysics, 82, 1992; 23) 

Solomon, S.C. et al., JGR, 97, 13199, 1992; 24) Ivanov, M.A. 

and J. W. Head, JGR, 101, 14861, 1996; 25) Hansen, V.L. and 

J.J. Willis, Icarus, 123,296, 1996; 26) Bridges, N.T. and G.E. 

McGill, USGS Geol. Inv. Ser., Map I-2747, 2002, 27) Konopliv, A.S., et al., GRL, 20, 2403, 1993, 28) Konopliv, A.S. 

and W.L. Sjogren, Icarus, 112, 42, 1994.

Fig. 1. Geological map of the Lavinia Planitia/Lada Terra region. Lambert equal-area projection.
THE FREDEGONDE (V-57) QUADRANGLE, VENUS: PRELIMINARY RESULTS, M. A. Ivanov1,2 and J. W. Head2 

1

Vernadsky Institute, RAS, Moscow, Russia, mikhail_ivanov@brown.edu; 2Brown University, Providence, RI, 

USA, james_head@brown.edu

Introduction: The most significant topographic 

province on Venus (~80%) are midlands (0-2 km above 

MPR, [1,2]) that display the richest variety of features

[3-12]. The sequence of terrains, units, and structures 

in the midlands are crucially important in the 

understanding of the time and modes of formation of 

this topographic province. The Fredegonde quadrangle 

(V-57, 50-75oS, 60-120oE) in the southern hemisphere 

of Venus is a typical region of midlands that exposes 

abundant features characterizing this province. The 

area of the map is also in contact with the upland of 

Lada Terra to the W and the lowland of Aino Planitia 

to the NE and, thus, may portray characteristics of the 

transitions from the midlands to the other major 

topographic provinces of Venus, lowlands and 

highlands. Here we report on the preliminary results of 

geologic mapping in the V-57 quadrangle and describe 

major features, units, and structures exposed in the map 

area, and outline the main episodes of the geologic 

history of this region.

Major geologic and topographic features of the 

V-57 area: The Fredegonde quadrangle (Fig. 1) covers 

the eastern portion of Lada Terra, which is within the 

midlands. The most prominent features in the map area 

are several large and small coronae organized into 

chains of circular structures interconnected by swarms 

of extensional structures, grooves and graben. The 

largest corona chain includes four coronae (Ilyana, 

Ambar-ona, Dunne-Musun, and Triglava Coronae) and 

extends in a NNE direction for several thousands of km 

through the central portion of the quadrangle. The 

second chain occurs in the NW corner of the map area. 

It includes two coronae (Shyv-Amashe and Marzyana 

Coronae) embedded within a broad deformational zone 

of extensional structures consisting of Geyaguga and 

Xaratanga Chasmata. The corona-groove chains 

resemble in many aspects the corona-rift zones at the 

margins of large equidimensional basins such as 

Lavinia (V-55) and Atalanta (V-4) Planitiae [13,14]. 

Subordinate structural zones within the V-57 area are 

fragments of belts of contractional ridges (Oshumare 

Dorsa) that occur centrally. The corona-groove chains 

and belts of ridges represent broad (100s km wide) and 

relatively low (100s m up to a kilometer high) 

topographic ridges. Broad and shallow (100s km 

across, 100s m deep) basin-like features of Mugazo, 

Alma-Merghen, Laimdota Planitiae occur between the 

corona-groove chains. Mildly deformed plains units 

cover the surface of the basins.

Material and structural units and their 

relationships: The variety of material and structural 

units that make up the surface of the V-57 quadrangle 

can be divided into three groups of different relative 

ages (Fig. 1). (I) The first group of oldest units consists 

of two material units, densely lineated plains (pdl) and 

ridged plains (pr), and one structural unit of groove 

belts (gb). Unit pdl occurs as small outliers in the 

central area of the map area. Ridged plains are exposed 

in fragments of the belts of ridges (Oshumare Dorsa). 

Groove belts consist of dense swarms of fractures and 

graben that interconnect coronae within the coronagroove chains. All units of this group form either local 

(pdl) or regionally important elevated areas (pr and gb) 

that are embayed by vast plains units. (II) The second 

group consists of two material units, shield plains (psh) 

and regional plains (rp). These units occur at the 

middle stratigraphic level and cover the majority of the 

quadrangle. Abundant small shield- and cone-like 

features (interpreted to be small volcanoes [15-17]) 

characterize the surface of shield plains. The volcanoes 

appear to be sources of the locally adjacent plains 

material. Regional plains have morphologically smooth 

surfaces and uniform radar backscatter. Sources of 

these plains material are not obvious. Wrinkle ridges 

deform both units of this group and sometimes occur in 

the older units. Shield plains and regional plains occur 

at relatively low topographic levels and fill the 

topographic basins. (III) The third group forms the top 

of the regional stratigraphic column and consists of two 

material units of smooth plains (ps) and lobate plains 

(pl). Smooth plains have uniform and preferentially 

low radar albedo and lobate plains are characterized by 

lobate and digitate boundaries. Both units are 

tectonically undeformed and embay most tectonic 

structures including wrinkle ridges. Lobate plains are 

spatially associated with some coronae (e.g. DunneMusun) of the corona-groove chains. Individual flows 

of this unit extend down the regional slopes and partly 

fill the basin-like topographic lows.

Summary: The results of our preliminary mapping 

in the V-57 quadrangle (Fig. 1) allow reconstruction of 

the major episodes of the geologic and topographic 

evolution of the eastern portion of Lada Terra [18]. 

Tectonic deformation apparently prevailed during the 

early stages of the history. The most prominent tectonic 

features were formed early on and are currently 

exposed as deformational belts of ridges and the 

corona-groove chains. The relationships between the 

older contractional and extensional structures suggest 

that the ridge belts are older and the corona-groove 

chains are younger features. The tectonic components 

of coronae (annulae, fracturing in the core, etc.) appear 

to be quasi-synchronous with the linear segments of the 

groove swarms that connect the coronae. The vast 
plains of the second group of units, however, broadly 

embay the corona-groove complexes and, thus, appear 

to be younger. During the earlier episodes of the 

regional geologic history, the most important 

topographic features, the broad topographic ridges and 

the basins, were formed.

During the middle and late periods of the geologic 

history, volcanic activity dominated in the region and 

the vast plains units were emplaced. These plains, now 

moderately deformed by tectonic structures filled the 

broad basin-like topographic features but left the older 

topographic ridges (ridge belts and corona-groove 

chains) exposed. Such a topographic distribution of 

shield plains and regional plains suggests that the 

overall topographic configuration of the midlands 

within the map area was established prior to 

emplacement of the units from the middle stratigraphic 

level. The youngest lobate plains sometimes represent 

a volcanic component of some coronae (e.g. DunneMusun). This association of the younger volcanic 

materials with the older tectonic structures suggests 

that some coronae were either 1) reactivated later, 2) 

their volcanic activity was delayed until the later 

stages, or 3) formational activity continued, but 

volcanism represents a late phase. The flow direction 

of lobate plains (from the broad topographic ridges

toward the floor of the basins) suggests, however, that 

the general topographic shape of the region within the 

V-57 quadrangle remained stable until the latest stages 

of the geologic history in this area.

References: 1) Masursky, H., et al., JGR, 85, 8232, 1980, 2) 

Pettengill, G.H., et al., JGR, 85, 8261, 1980, 3) Ford, P.G. 

and G.H. Petttengill, JGR, 97, 13103, 1992, 4) Barsukov, 

V.L., et al., JGR, 91, D399, 1986, 5) Frank, S.L. and J.W. 

Head, EMP, 50/51, 421, 1990, 6) Basilevsky, A.T. and J.W. 

Head, PSS, 48, 75, 2000, 7) Basilevsky, A.T. and J.W. Head, 

JGR, 105, 24583, 2000, 8) Stofan, E.R., et al., Icarus, 152, 

75, 2001, 9) Bleamaster, L.F. and V.L. Hansen, JGR, 109, 

doi: 10.1029/2003JE002193, 2004, 10) Nunes, D.C., et al., 

JGR, 109, doi: 10.1029/2003JE002119, 2004, 11) Young, 

D.A. and V.L. Hansen, JGR, 110, doi: 10.1029/2004JE00 

1965, 2005, 12) Herrick, R.R., et al., JGR, 110, doi: 10.1029/ 

2004JE002283, 2005, 13) Ivanov, M.A. and J.W. Head,

USGS Map I-2684, 2001, 14) Ivanov, M.A. and J.W. Head, 

USGS Map I-2792, 2004, 15) Aubele J.C., LPSC XXVI, 59, 

1995, 16) Addington, E.A., Icarus, 149, 16, 2001, 17) 

Ivanov, M.A. and J.W. Head, JGR, 109, doi:10.1029/ 2004 

JE002252, 2004, 18) Kumar, S. and J.W. Head, this volume.

Fig. 1. Preliminary geological map of the Fredegonde (V-57) quadrangle.
THE V-7 QUADRANGLE: SEQUENCE OF EVENTS DURING FORMATION OF LAKSHMI PLANUM, VENUS.

M. A. Ivanov1,2 and J. W. Head2 ; 1Vernadsky Institute, RAS, Moscow, Russia, mikhail_ivanov@brown.edu; 2Brown 

University, Providence, RI, USA, james_head@brown.edu

1. Introduction: Lakshmi Planum (western Ishtar 

Terra) represents a unique class of highlands on Venus: 

It is a high-standing volcanic plateau (3-4 km above 

MPR), which is surrounded by the highest Venusian 

mountain ranges that are 7-10 km high [1-7]. Lakshmi 

Planum is the key feature of the V-7 quadrangle (50-

75oN, 300-360oE). Two classes of models were 

proposed to explain the unique topographic and 

morphologic characteristics of western Ishtar Terra. In 

the first, this feature is considered as a result of mantle

upwelling followed by formation and collapse of a 

large dome [6, 8-10]. In the second, Lakshmi Planum is 

explained by a mantle downwelling and collision of 

terrains against a foreland in the core of Lakshmi [11-

16]. The sequence of events during the formation of 

Lakshmi plays a crucial role in the assessment of both 

models. The first class of models predicts a general 

progression of events from inside out whereas the 

alternative model would be consistent with the opposite 

direction of the geologic activity, the older relative age 

of the mountain ranges, and younger volcanic activity 

in the central area of the plateau. Here we describe the 

set of mapped units and structures and outline the 

apparent sequence of events during formation of 

Lakshmi Planum based on the results of the mapping of 

the V-7 area.

2. Material units: Eleven material units make up 

the surface of the V-7 quadrangle (Fig.1). (1) Tessera 

(t) is exposed inside and outside Lakshmi Planum and 

appears to be the oldest material because it is embayed 

by most of the other units in the map area. (2) Densely 

lineated plains (pdl) postdate tessera and form one of 

the oldest units. Patches of pdl occur outside Lakshmi 

Planum. (3) Ridged plains (pr) postdate pdl and occur 

outside Lakshmi. (4) Shield plains (psh) display 

abundant small (a few km) shield-shaped features 

interpreted to be small volcanoes. The unit embays the 

previous ones and occurs predominantly within the 

lowlands around Lakshmi. (5) Pitted and grooved 

material (pgm) displays small pits and is cut by broad 

and shallow grooves with scalloped edges. The unit 

occurs inside Lakshmi in spatial association with the 

mountain ranges. (6) Regional plains (rp) have a 

smooth surface, which is cut by wrinkle ridges. This is 

the most widespread unit and occurs inside and outside 

of Lakshmi Planum. (7) Lower unit of lobate plains 

(pl1) is also deformed by wrinkle ridges but has lobate 

boundaries and higher radar albedo than regional 

plains. The unit occurs both inside and outside 

Lakshmi. (8) Upper unit of lobate plains (pl2) is 

characterized by lobate flows that embay most tectonic 

structures including wrinkle ridges. The unit forms 

flow complexes outside Lakshmi and surround Colette 

and Sacajawea Paterae inside the plateau. (9) Smooth 

plains (ps) have uniform and low radar albedo. Material 

of unit ps embays wrinkle ridges. The largest 

occurrence of the unit is in the southern portion of 

Lakshmi Planum. (10) Impact craters (c) and (11) crater 

outflow deposits (cf) are peppered throughout the 

quadrangle without any preferential concentrations.

3. Structures (Fig.1): Extensional structures. In 

places, extensional structures (fractures and graben) are 

closely spaced and obscure underlying terrain. These 

concentrations form belts (groove belts, gb) that extend 

for hundreds of kilometers mostly within the southern 

regional slope of Lakshmi Planum where they cut the 

units pdl and pr and are embayed by shield plains and 

regional plains. Contractional structures. Several types 

and scales of contractional features are observed within 

the quadrangle. Wrinkle ridges mildly deform shield 

plains and regional plains. Broader and more linear 

ridges dominate ridged plains (pr), which are largely 

equivalent to the ridge belts of [17,18]. The most 

important occurrences of contractional structures in the 

map area are mountain belts (unit mt) that surround the 

interior of Lakshmi Planum and consist of densely 

spaced ridges 5-15 km wide and tens of km long. 

Regional plains inside and outside Lakshmi usually 

embay the ridges.

4. Discussion and conclusions There are three 

major physiographic provinces in the map area: the 

exterior of Lakshmi Planum, the interior of Lakshmi, 

and the surrounding mountain ranges. The exterior of 

Lakshmi displays abundant tectonized units that 

predate regional plains (t, pdl, gb, pr, Fig. 1) suggesting 

that tectonic deformation dominated in this region 

during the earlier episodes of the geologic history. The 

oldest unit in the interior of Lakshmi is tessera and the 

heavily tectonized units such as pdl, pr, and gb are 

almost absent there (Fig. 1). This suggests a possible 

gap in the tectonic/stratigraphic sequence from tessera 

to regional plains in the interior of Lakshmi Planum. 

The outliers of tessera are scattered throughout the 

interior probably because the suite of the younger 

plains units there is relatively thin. The important 

feature of the interior is the absence of either ridges or 

ridge belts that indicates virtual lack of contractional 

deformation there. The absolute majority of 

contractional deformation is concentrated within the 

mountain belts (Fig. 1). The oldest unit embaying the 

ranges is regional plains. Thus, the mountain belts 

formed relatively early during the geologic history of 

the region. Regional plains and the younger plains units 

occur both inside and outside Lakshmi. The state of 
2

their deformation units indicates that tectonic activity 

responsible for the deformation of such units as pdl, pr, 

and gb and formation of the mountain ranges mostly 

ceased by the time of emplacements of the vast plains 

(psh, rp, pl1, pl2, ps).

The general sequence of events documented within 

the V-7 quadrangle indicates that tectonism dominated 

during the earlier episodes of the geologic history 

before emplacement of shield plains and regional 

plains. The major deformational belts, including the 

mountain ranges, formed during this period. The 

concentration of the tectonized units outside Lakshmi 

and their absence in the Lakshmi interior suggests the 

general progression of tectonic events oriented from 

outside toward the planum, which is consistent with the 

formation of the western Ishtar Terra due to large-scale 

horizontal convergence, underthrusting, imbrication, 

and folding [13,14,16,19]. The major plains units were 

emplaced, and preserved their morphological identity at 

a time when tectonic deformation had largely waned 

and the general topographic configuration of the region 

was established. The youngest activity in the region 

was related to volcanism through a few distinct 

volcanic centers inside and outside Lakshmi.

References: 1) Masursky, H., et al., JGR, 85, 8232, 1980, 2) 

Pettengill, G.H., et al., JGR, 85, 8261, 1980, 3) Basilevsky, 

A.T., et al., JGR., 91, D399, 1986, 4) Barsukov, V.L. et al., 

JGR, 91, D399, 1986, 5) Sukhanov, A.L., et al., USGS Map I2059, 1989, 6) Pronin, A.A. In: Venus Geology, 

Geochemistry, and Geophysics, 68-81, 1992. 7) Kaula, W.M., 

et al., JGR., 97, 16085, 1992, 8) Pronin, A.A., Geotectonics, 

20, 271, 1986, 9) Grimm, R.E. and R.J. Phillips, GRL, 17, 

1349, 1990, 10) Grimm, R.E. and R.J. Phillips, JGR, 96, 

8305, 1991, 11) Vorder Bruegge, R.W. and J.W. Head, GRL, 

16, 699, 1989, 12) Vorder Bruegge, R.W. and J.W. Head, 

Geology, 19, 885, 1991, 13) Head, J.W., Geology, 18, 99, 

1990, 14) Roberts, K.M. and J.W. Head, GRL, 17, 1341, 

1990, 15) Bindschadler, D.L., et al., GRL, 17, 1345, 1990, 16) 

Keep, M. and V.L. Hansen, JGR., 99, 26015, 1994, 17) 

Solomon, S.C., et al., JGR, 97, 13199, 1992, 18) Squyres, 

S.W., et al., JGR, 97, 13579, 1992, 19) Vorder Bruegge, R.W. 

and J.W. Head, EMP, 50/51, 251, 1990.

Fig. 1 Geological map of the Lakshmi Planum (V-7) quadrangle.
GEOLOGICAL MAPPING OF THE LADA TERRA (V-56) QUADRANGLE, VENUS: PRELIMINARY OBSERVATIONS, 

P. Senthil Kumar1,2 and James W. Head2

, 1National Geophysical Research Institute, Hyderabad 500007, India, 

senthilngri@yahoo.com; 2

Department of Geological Sciences, Brown University, Providence, RI 02912, USA, 

james_head@brown.edu. 

Introduction: Geological mapping of the V-56 

quadrangle (Fig. 1) reveals various tectonic and 

volcanic processes in Lada Terra that consist of 

tesserae, regional extensional belts, coronae, volcanic 

plains and impact craters. This study aims to map the 

spatial distribution of different material units, 

deformational features or lineament patterns and 

impact crater materials. In addition, we also establish 

the relative age relationships (e.g., overlapping or 

cross-cutting relationship) between them, in order to 

reconstruct the geologic history. Basically, this 

quadrangle addresses how coronae evolved in 

association with regional extensional belts, in addition 

to evolution of tesserae, regional plains and impact 

craters, which are also significant geological units of 

Lada Terra. 

Geologic mapping: We used 250-m-per-pixel 

Magellan SAR images to prepare a geologic map in a 

scale of 1:5,000,000. Wherever necessary, fullresolution (75-m-per-pixel) images are used for fine 

details. This quadrangle is bordered by Kaiwan Fluctus 

(V-44) [1] and Agnesi (V-45) [2] quadrangles in the 

north; Mylitta Fluctus (V-61) [3,4], Fredegonde (V-57) 

[5] and Hurston (V-62) [2] quadrangles in the west, 

east, and south, respectively. From the geologic 

mapping, we report on the distribution of the following 

material and structural units, and reconstruct the 

geologic history. 

Material and structural units: The oldest known 

material units are tesserae. They are radar bright areas 

characterized by multiple orientations of lineaments; 

two sets are dominant: NNW-SSE and ESE-WNW 

oriented lineaments. Tightly spaced ridges and troughs 

generally characterize tesserae. The third dominant 

lineaments are NNE-SSW and NNW-SSE oriented 

long rift zones, namely, Chang Xi Chasmata and SeoNe Chasma; but these are apparently restricted to the 

Cocomama Tessera. In the northeastern part of the 

quadrangle, terrains (TLT, Fig. 1) similar to tessera are 

found. They have NNE-SSW to NE-SW oriented 

ridges, which are cut by ESE-SNW to NW-SE oriented 

troughs. The spacing of these structures is greater than 

the structures of the tessera. The tessera units contain 

intra-tessera basins, which are filled by lava flows of 

different ages; most of them are derived from the units 

outside the tessera, and a few are from intra-tessera 

volcanism. 

Regional plains units embay the tessera terrain; they 

have wrinkle ridges and a few young fracture systems. 

The oldest known plains (but younger than tessera) are 

lineated (LP, Fig. 1), and are closely associated with 

shield plains (unit 5, Fig. 1) and the tessera. The LP is 

characterized by tightly spaced, NNW-SSE oriented 

fractures, which are also common in the tessera. Two 

types of shield plains are present: a few occur in the 

pre-regional plains areas, while others occur in the core 

of coronae and adjoining areas. 

The older regional plains (unit 4, Fig. 1) are cut by 

two regional extensional belts [6]: (1) NNW-SSE 

trending, 6000-km long and 50-200 km wide, AlphaLada (AL) belt, and (2) NNE-SSW trending, 2000 km 

long and 300 km wide, Derceto-Quetzalpetlatl (DQ) 

belt. These two belts are composed of fractures, rift 

basins and strike-slip zones. The DQ belt is punctured 

by Sarpanitum, Eithinoha and Quetzalpetlatl Coronae, 

while the Otygen, Demvamvit and Okhin-Tengri 

Coronae occur along the AL belt. A few coronae have a 

circular central dome and outer concentric depression; 

they are defined by fractures, rift basins and ridge belts. 

Asymmetric and multiple coronae also occur in the 

southern part of the AL belt. Two other extensional 

belts branch from the AL belt. Dyamenyuo and Toyouke Coronae and Loo-wit and Kshumay Montes 

puncture these extensional belts. At many places, 

corona structures cut across the regional extensional 

belts, while at other places, the extensional belts cross 

the corona structures. There is a clear overlapping 

time relationship, as the one affects the formation of 

the other. Corona volcanism and tectonics are also 

closely related to one another. Lava flows erupt along 

the corona fractures, for example, in the Ethinoha 

Corona. Lava flows emanating from coronae travel 

several hundred kilometers. Volcanism is also related 

to shield volcanoes in many places. 

The DQ and AL belts separate the plains units of 

Lavinia Planitia, Aibarchin Planitia and Mugazo 

Planitia, where lava flows are abundant; principally 

there are four plain units, of which the oldest one 

appears to be common to all the planitia units. Most of 

the younger units are locally derived from the coronae. 

The regional plains occurring to the east of Otygen 

Corona have undergone intense fracturing and 

emplacement of dykes after post corona-extensional 

belt deformation. These fractures occur in two 

directions: ENE-WSW and NW-SE. It appears that 

they represent the latest deformation, and could 

probably be related the terrain uplift, as is evident in 

many terrestrial examples. 

Impact craters are the youngest geologic units, 

except for one that is affected by the extensional belt 

deformation and the other embayed by regional plains. 

Most impact craters show complex geometry and a few 
are bowl-shaped. Many complex craters show run-out 

flows characteristic of oblique impacts. Further 

detailed mapping is underway to reconstruct the 

complete geologic history of this quadrangle in near 

future. 

Acknowledgements: We thank Misha Ivanov for 

his help while initiating this mapping project, and 

Jay Dickson and Prabhat while working with the 

virtual wall image facility. 

References: [1] Bridges, N.T., and McGill, M.E., 

USGS Scientific Investigations Map I-2747, 2002. [2] 

http://astrogeology.usgs.gov/Projects/PlanetaryMappin

g/MapStatus/VenusStatus/Venus_Status.html. [3] 

Ivanov, M.A., and Head, J.W., USGS Scientific 

Investigations Map 2920, 2006. [4] Ivanov, M.A., and 

Head, J.W., this volume. [5] Ivanov, M.A., et al., this 

volume. [6] Baer, G., et al., J. Geophys. Res., 99, 8335-

8369, 1994. 

Fig. 1. Preliminary geological sketch map of V-56 Lada Terra quadrangle (50oS-75oS; 0oE-60oE): Material units 

(from older to younger): tessera terrain (Te), tessera-like terrain (TLT), lineated plains (LP), plain units from 5 to 1 

and impact craters. Lineament patterns defining the tessera (Te) extensional belts (RZ) and coronae (C) are shown in 

different colors: greenish yellow–tessera, green–extensional belts; dark blue–coronae. Many of the plains units (3 to 

1) are related to volcanism of coronae. 
PRELIMINARY GLOBAL SURVEY OF CIRCULAR LOWS, A SUBSET OF VENUSIAN 

CORONAE. B. Shankar1

 and V. L. Hansen1, 1Department of Geological Sciences, University of Minnesota 

Duluth, Duluth, MN 55812 (shank075@d.umn.edu; vhansen@d.umn.edu). 

Introduction: Venus preserves over 500 

coronae, most of which occur in chains (68%) or 

clusters (21%) spatially associated with mesoland 

chasmata and highland volcanic rises, respectively 

[1-8]. Coronae range in diameter from 60-1100 km 

(~200-km diameter median [4, 5]). Many workers 

accept that coronae represent the surface 

expression of endogenic diapirs [e.g., 2, 4, 9-14], 

although other hypotheses have been proposed, 

including formation as volcanic caldera and by 

exogenic impactors [e.g., 2, 15-29]. The wide 

range in character of coronae might indicate that 

not all coronae formed by similar processes. We 

investigate the formation of a subset of coronae, 

herein called circular lows, through detailed 

mapping of individual circular lows, regional 

mapping of circular lows in V-45, and a global 

survey of circular lows. 

Background: Were all coronae created 

equally? That is, did all coronae form by a similar 

mechanism? Can a claim of similar genetic 

formation be robustly supported? The spatial 

association of corona chains and corona clusters 

with chasmata and volcanic rises, respectively, 

favors endogenic formation for these two broad 

groups of coronae. Many of these coronae also 

display radial fractures and concentric structures 

(called radial concentric coronae [4]), as well as 

associated flows that are consistent with endogenic 

genesis [e.g., 4-5, 10, 12, 29]. But ~11% of 

coronae occur as relatively isolated features in 

Venus’ lowland [4-5]. In contrast to chained and 

clustered coronae, lowland/isolated coronae lack 

compelling spatial evidence for endogenic 

formation. Lowland/isolated coronae do not, so far 

as has been recognized, define geometric patterns 

among coronae, nor do they correlate spatially 

with other geological features. Morphologic and 

structural characteristics might also set 

lowland/isolated coronae apart from ‘typical’ 

coronae that occur in chains and clusters. Some 

lowland/isolated coronae lack significant fracture 

annuli, and/or associated flows [5]; these 

differences could reflect post-formation burial or 

different mechanisms of formation. The subset of 

lowland/isolated coronae might be divisible into 

two distinct morphologic types (not including 

stealth coronae of Stofan et al. [5]): (a) features 

marked by positive topography and radial fractures 

(radial lowland coronae, herein; although the 

morphology of these coronae appears to be similar 

to radial concentric coronae of Stofan et al. [4], we 

use radial lowland coronae herein to specify their 

lowland location), and (b) features marked by 

circular basins (negative topography relative to 

surroundings) with morphology akin to sunken 

amphitheaters (coronae types 4 or 8 of Smrekar 

and Stofan [6]; circular lows, herein). 

Methods: We are in the process of conducting 

a global survey of circular lows. We use Magellan 

SAR and altimetry data for all the Vmap 

quadrangles (V-1 to V-62), in addition to synthetic 

stereo images for V-2 to V-61 as circular lows are 

best recognized in synthetic stereo imagery. The 

polar quadrangles, V-1 and V-62, do not have 

synthetic stereo images. This data base allows us 

to conduct a global survey to identify all circular 

features with negative topographic signatures. We 

have previously constructed synthetic stereo 

images for each of the Venus VMap quadrangles, 

except the polar regions, using the USGS VMap 

SAR image base and Magellan altimetry data 

following the procedure outlined by Kirk et al. 

[31] using macros developed by D.A. Young. 

Adobe IllustratorTM allows layer transparency 

which enables concurrent consideration of 

altimetry and SAR data, as is crucial for circular 

low identification. Circular lows are most readily 

visible in synthetic stereo imagery, but these 

images do not allow us to easily quantify relative 

heights of rims, or interior depths, which can be 

gained from contoured altimetry data. D.A. Young 

also developed macros that allow us to contour 

altimetry data so VMap synthetic stereo imagery 

and contoured altimetry are easily overlain and 

compared in Abode IllustratorTM. 

Global survey data is collected on 

georeferenced VMap images using Adobe 

Illustrator; full resolution SAR images are 

imported from USGS Map-a-Planet as required. 

Survey results are tabulated such that individual 

circular low locations and characteristics can be 

plotted globally in order to allow comparison with 

other global data bases. All information will be 

complied on the USGS VMap bases. Map 

PublisherTM software enables us to reproject 

1
mapping in an ArcGlobe GISTM environment, in 

order to make comparisons with other global data 

sets including: coronae, impact craters, ridge belts, 

tessera terrain, tectonic provinces, etc. We have 

found that the method of data collection and 

reprojection of the data, rather than reprojection of 

image data, allows us to consider the highest 

resolution data in such a project. 

We are mapping circular low locations using 

ArcGlobe GISTM so that we can compare spatial 

locations of circular lows with one another and 

with global scale geomorphic features across 

Venus. In addition, we examine individual circular 

lows through VMap data analysis in order to 

determine a range of criteria including: location, 

tectonic setting, host terrain, shape (ellipticity), 

diameter, topographic profiles, annuli character 

(width, degree spread, structural character), 

presence and extent of radial fractures, location 

and extent of flows, presence of rim, and interior 

features. We will compare circular lows to the 

global database of ribbon tessera that are 

independently generated and still in progress. We 

expect that other criteria may emerge during the 

course of the global survey. 

Preliminary results: To date we have 

identified 67 potential circular lows that range in 

diameter from 30-375 km (~125 km diameter 

median). Although most circular lows are circular, 

a few are elliptical in shape. Circular lows are 

relatively equally distributed throughout the planet. 

They appear equally in the northern and southern 

hemispheres, although the latitudes between 125°E 

and 202°E host only a few (three) circular lows. 

Circular lows commonly occur as relatively 

isolated features. However, they can occur in near 

proximity to one another. For example, six circular 

lows occur on either side of Gegute Tessera, north 

of Aphrodite Terra (~15o

N/120oE). A group of 

three circular lows occur around at 53o

S/290oE. 

Topographically, circular lows dominantly 

occur within the lowlands; however they avoid the 

deepest lowland basins. Seven circular lows occur 

in highlands locations including: three in Lakshmi 

Planum, one each in Atla and Ovda Regiones, and 

two in western Ovda Regio. Six circular lows may 

occur within the region between Atla Regio and 

Atahensik Corona; these features might, however, 

reflect regional topographic complexity, rather 

than specific morphological features. 

Tectonically, circular lows do not occur in 

chasma-corona chains except as previously noted. 

They also do not occur in volcanic rises. 

References: [1] J.W. Head et al. JGR, 97 

13153-13198 (1992). [2] S.W. Squyres et al. JGR, 

97 13611-13634 (1992). [3] K.M. Roberts & J.W. 

Head GRL, 20, 1111-1114 (1993). [4] E.R. Stofan 

et al. JGR, 97, 13347-13378 (1992). [5] E.R. 

Stofan et al. GRL, 28 4267-4270 (2001). [6] S.E. 

Smrekar & E.R. Stofan Sci., 277 1289-1294 

(1997). [7] S.E. Smrekar & E.R. Stofan Icarus, 139 

(1) 100 (1999). [8] J.E. DeLaughter & D.M. Jurdy 

Icarus, 139 (1) 81 (1999). [9] D.M. Janes et al. 

JGR, 97 16055-16068 (1992). [10] E.R. Stofan et 

al. in, Venus II, 931-968, Univ. AZ Press (1997). 

[11] D.M. Koch JGR, 99 2035–2052 (1994). [12] 

D.M. Janes & S.W. Squyres JGR, 100 (E10) 

21,173-21,187 (1995). [13] D.M..Koch & M. 

Manga GRL, 23 225-228 (1996). [14] V.L .Hansen 

Geol. Soc. Amer. Bull., 115 1040-1052 (2003). 

[15] V.L. Barsukov et al. Geokhimia, 12 1811-

1820 (1984). [17] D.B. Campbell & B. Burns 

Science, 204 1424-1427 (1979). [18] R.A.F. 

Grieve & J.W. Head, Episodes, 4(2) 3-9 (1981). 

[19] J.W. Head & S.C. Solomon Science, 213 62-

76 (1981). [20] H. Masursky et al. JGR, 85 8232-

8260 (1980). [21] G.G. Schaber & J.M. Boyce 

Impact and explosion cratering—Planetary and 

terrestrial implications: New York, Pergamon 

Press, 603-612 (1977). [22] O.V. Nikolayeva et al. 

Geochemistry International, 23(9) 1-11 (1986). 

[23] O.V. Nikolayeva LPSC, 24 1083-1084 

(1993). [24] R. Greeley Planetary Landscapes; 2nd

ed., Allen & Unwin, London (1987). [25] W.B. 

Hamilton, Geol. Soc. Am., C-2 597-614, (1993). 

[26] W.B. Hamilton, GSA Spec. Paper 388, 781-

814 (2005). [27] P.H. Schultz LPSC, 24 1255-

1255 (1993). [28] C. Vita-Finzi et al., GSA Spec. 

Paper 388, 815-824 (2005). [29] V.E. Hamilton & 

E.R. Stofan Icarus, 121 (1) 171 (1996). [30] R.L. 

Kirk et al. JGR, 97 16371-16380 (1992). 

2
UPDATE ON MAPPING OF QUADRANGLES V-28, V-52 AND V-19. E.R. Stofan1, 2, J.E. Guest2

, A.W. 

Brian2 and P.M. Martin3

, 1Proxemy Research (20528 Farcroft Lane, Laytonsville, MD 20882, ellen@proxemy.com), 2 Department of Earth Sciences, University College London WC1E 6BT, 3

Department of Earth Sciences, Durham 

University DH1 3LE. 

Introduction: Although extensive mapping of the 

surface of Venus and continued analysis of Magellan 

data have allowed a more complete understanding of 

the venusian surface, controversy remains over the 

evolution the surface [e.g., 1, 2]. We are finalizing 

maps of three quadrangles, which will add to this ongoing scientific debate. Quadrangle V-28, in revision, 

covers an area along Hecate Chasma. V-53, in revision, covers a portion of Parga Chasmata and Themis 

Regio. Quadrangle V-19, to be submitted fall 2007, 

covers the northern margin of western Eistla Regio and 

Sedna Planitia. 

V-28: We identified nine plains materials units in V28. V-28 has a variety of mappable volcanic landforms 

including several large shield volcanoes (Nazit Mons, 

Polik-mana Mons, Kono Mons, and Xochiquetzal 

Mons), numerous intermediate volcanoes, abundant 

small volcanic edifices and a large flow field. Few of 

the edifies are in contact with each other. Eighteen 

coronae, ranging in size from 125 to 525 km, are located in V-28, as well as flows from a nineteenth corona, Miti, located outside the quadrangle. Of the 

eighteen coronae, ten have associated mappable deposits. Three outcrops of materials with two or more 

dominant fracture and/or ridge orientations were 

mapped as tessera. Thirteen impact craters are in the 

V-28 quadrangle. Two of the craters, Nuriet and Higgins, have very unusual morphology, with an indistinct, irregular crater and outflow-like deposits. Eight 

have at least partial dark floors. 

 The geologic history of V-28 is dominated by 

formation of rifts, volcanism and corona formation. 

We can identify no regional-scale plains units; the numerous plains units appear to be local units. Identifying different plains units in and near the rift is extremely difficult, owing to the intensity of the fracturing. Therefore, we do not feel overly confident of the 

age relationship or continuity of plains units mapped in 

the immediate vicinity of the rift. 

 The large number of small and intermediate volcanoes in V-28 illustrates the typical abundant volcanism within the BAT region (Beta-Atla-Themis) [3]. 

Edifice fields are thought to be relatively young based 

on superposition relationships, and all plains units, 

particularly those south of the rift, tend to have anomalously high concentrations of small edifices. Individual small edifices, both within edifice fields and within 

plains units, appear to span a relatively long period of 

time, based on cross-cutting relationships with local 

structures. The earliest history of this quadrangle is 

preserved in deformed plains units and tessera on either side of the rift. The amount of time represented by 

these units, and whether they represent earlier episodes 

of rift formation in this region, is not clear. Later 

plains units of relatively limited aerial extent were 

formed by volcanic processes. These units were subsequently rifted. Volcanism and corona formation occurred prior to, during and after rift formation. 

On Venus, only ~17% of the total population of 

impact craters are either volcanically embayed and/or 

tectonized (Schaber et al., 1992). In V-28, 38% of 

craters are embayed or tectonized. In addition, several 

other craters have a somewhat ambiguous relationship 

with surrounding units. We also do not include in the 

embayed population the number of dark floored craters; therefore, we would argue that the 38% is likely 

to be an underestimate. Detailed mapping clearly is 

likely to raise the number of tectonized and embayed 

craters on Venus. Despite this, the V-28 region clearly 

contains an anomalous number of modified craters. 

V-53: We have identified seven plains materials units 

within V-53. None of the plains units are analogous to 

regional-scale plains units mapped in other quadrangles. Eleven units associated with nine named volcanic 

edifices have been mapped, including those associated 

with the large volcanoes Chloris Mons, Mielikki Mons 

and Tefnut Mons. Multiple materials units associated 

with unnamed or unknown sources have also been 

mapped and combined into a single unit: a volcanic 

center unit (unit vc) and edifice field unit (unit ef). 

Most of the volcanic flow units are not in contact with 

each other, or with consistent plains or corona units, 

making an overall volcanic stratigraphy difficult to 

determine. 

 Nineteen named coronae have associated flow 

materials units, along with units associated with three 

unnamed coronae. In addition, twelve impact craters 

are in the V-53 quadrangle. They range in diameter 

from 11- 52 km. Four are superposed on the mottled 

plains unit; the crater Kitna is superposed on the 

Themis fractured plains, and Aksentyeva crater is superposed on the Themis lobate plains. The craters 

Jocelyn and Elza are superposed on flows from 

Obiemi Corona. The 52 km diameter crater Kenny is 

clearly embayed by flows from Abeona Mons. 

 Two craters, Peck and Bernadette, have a complex 

relationship with the surrounding units. Peck appears 

to be superposed on unit pdf, but its ejecta has been 

fractured and embayed, and its interior embayed by 

later flows that occurred within pdf. We interpret it to 
STATISTICAL ANALYSES OF CORONAE: E.R. Stofan et al. 

have formed during the apparently protracted evolution of unit pdf. The crater Bernadette is supposed on 

Nzambi Corona flows, but it is also embayed by small, 

difficult to map, later Nzambi flows. 

 The earliest geologic activity in V-53 is recorded 

by plains units pdf and pl, suggesting that the region 

has been subjected to multiple episodes of plains forming volcanism and deformation, culminating in the 

current (ongoing?) activity of Parga Chasmata and 

Themis Regio. The large number of plains units, coronae and volcanoes in V-53 results in a very horizontal 

stratigraphic column, as few units are in direct contact. 

The bulk of the geologic activity is related to uplift, 

volcanism and corona formation at Themis Regio, and 

the rifting of Parga Chasmata. All of this activity 

overlapped in time; the duration of the activity is unknown. 

V-19: We have mapped seven plains units in the V-19 

quadrangle. One of these plains units (Sedna homogeneous plains) is a much larger scale unit than those 

mapped in the two chasma-related quadrangles. 

Twelve flow units associated with five coronae (Nissaba, Purandhi, Idem-Kuva, Tutelina and Mesca) have 

been delineated. Idem-Kuva and Nissaba units are interfingered; other corona units are not in contact. Flow 

units associated with eight volcanoes were mapped, 

including flows from Gula and Sif Montes. Intermediate scale edifices mapped include Toci Tholus, Sachs 

Patera, Evaki Tholus, and Bunzi Mons. In addition, 

volcanic center and edifice field units were mapped. 

In the northern portion of the quadrangle are flow units 

associated with Neago Flūctus. 

 Tectonic features in V-19 include Manzan-Gurme 

Tesserae, Zorile Dorsa, and Karra-māhte Fossae. The 

dorsa and tessera units are embayed by later plains 

units and thus form mappable units, while faults of the 

fossa cut the plains. 

 The early history of the quadrangle is characterized by tectonic deformation of volcanism (tessera and 

dorsa formation and plains volcanism). The bulk of 

the history of the quadrangle is characterized by interfingered, large – and intermediate- scale plains units 

and corona formation, with activity associated with 

Eistla Regio (volcanism, corona formation) occurring 

in the later part of the history of V-19. 

Discussion: Two end-member models have been proposed for Venus: a directional model in which specific 

types of features formed globally at specific times 

(e.g., 2), and a non-directional model in which types of 

geologic features form over the range of observable 

Venus history (~ 750 my) [1, 4]. An exception to the 

non-directional model is tessera; the majority of 

tessera plateaus seem to predate the plains that immediately surround them (e.g., 5, 6). All of the quadrangles contain fragments of tessera; theories for these 

fragments range from an old, widespread unit that underlies much of the plains [5] to the fragments forming 

at multiple times by different mechanisms [6]. In all 

three quadrangles the fragments are in close proximity 

(~100 km), suggesting that they once formed a larger 

unit. However, the extent and the origin of this unit 

and the age of it relative to the other ‘old’ plains units 

in the quadrangles are not known. 

 Plains, volcano and corona units in these quadrangles are more consistent with a non-directional model. 

We see no evidence here for a widespread episode of 

resurfacing, with the possible exception of V-19; instead the patch-like, composite character supports incremental resurfacing over time. Small edifices have 

formed throughout the histories of the quadrangles. 

References. [1] Guest J.E. and Stofan E.R. (1999) 

Icarus, 139, 55. [2] Basilevsky A.T. et al. (1997), in 

Venus II, eds. S.W. Bougher, D.M. Hunten, R.J. Phillips, Univ. of Ariz. Press, Tucson, 1047. [3] Crumpler, 

L.S., et al., (1997) in Venus II, eds. S.W. Bougher, D. 

M. Hunten, R.J. Phillips, Univ. of Ariz. Press, Tucson, 

1047. [4] Stofan E.R. et al., (2005) Icarus, 173, 312-

321, 2005. [5] Ivanov, M.A. and Head, J.W., (1996) J. 

Geophys. Res. v. 101, 14, 861-14,908. [6] Hansen, 

V.L. and J.J. Willis (1996) Icarus v. 123, 296-312. 
PRELIMINARY GEOLOGIC MAP OF AGNESI QUADRANGLE, V-45 (25-50S/30-60E). E. R. 

Tharalson1

 and V. L. Hansen1, 1Department of Geological Sciences, University of Minnesota Duluth, 

Duluth, MN 55812 (thar0030@d.umn.edu; vhansen@d.umn.edu). 

Introduction: We are creating a 1:5 M scale 

geologic map of Agnesi quadrangle (V-45), in 

order to understand the evolution of lowland 

tessera terrain, and to compare the formation of 

radial lowland coronae, and lowland coronae 

marked by circular basins, referred to as circular 

lows. Mapping uses full resolution Magellan 

SAR data, and altimetry.

V-45 Geology: Agnesi quadrangle (V-45), 

named for centrally located Agnesi crater, hosts 

nine coronae and several tracts of tessera terrain 

and lies within Venus’ lowland. The area ranges 

in altitude from 6050.8 to 6053.5 km, with an 

average of ~6052 km. V-45 is marked by 

numerous linear to curvilinear ridges, and 

several local highs which host Tushita and Xi 

Wang-mu Tesserae in the east and central 

region, respectively, and various domical 

coronae in the NW and SE corners of the map 

area. Fonueha Planitia, which trends east 

between WNW-trending Tushita Tesserae ridge 

to the north and a broad mesoland area to the 

south, is narrow and relatively poorly defined 

compared to other Venusian planitiae. In the 

NW part of the quadrangle curvilinear ridges 

describe concentric circles with diameters of 

900-1200 km. The three nested ridges are 100-

75 km wide and hundreds of km long, each 

separated by 200-100 km basins that parallel the 

adjacent ridges. These ridges host linear tracts 

of ribbon tessera terrain, with structural fabric 

parallel to the ridge crests. The intervening 

elongate basins parallel tessera fold trends. V-45 

also hosts nine lowland coronae, two montes, 

and 13 ‘pristine’ impact craters. Sezibwa Vallis, 

in the southwest, hosts long flows up to 

hundreds of km in length sourced from V-44 to 

the west. V-45 lacks chasmata, except for the 

misnamed ‘Artio Chasma,’ which forms the 

middle curvilinear ridge, rather than a 

topographic low. Artio ridge preserves shallowly 

buried ribbon tessera terrain, with structural 

fabrics parallel to the ridge axis. Shield-terrain 

occurs across much of V-45. Regional 

lineaments trend ENE across the map area. The 

NE corner preserves the only tract of wrinkle 

ridges, which trend NNW, perpendicular to 

ENE-fractures. A data gap ~500-650 km occurs 

across the south-central part of the map area. 

We have focused geologic mapping to date 

on the coronae and tessera terrain, each of which 

are briefly described in turn. 

V-45 coronae: The coronae include four 

features (Mama-Allpa, Inanna, Codidon, and 

Mou-nyamy) marked by topographic domes and 

radial fracture suites (termed radial coronae, 

herein) and four (Umay-ene, Xcanil, Zemlika, 

and a small unnamed corona) represent circular 

basins (termed circular lows, herein). EkheBurkhan Corona, which straddles the southcentral boundary, differs morphologically from 

both the radial coronae and circular lows. Gurshi 

Mons (SE corner) displays radial fractures, and 

appears morphologically similar to the adjacent 

radial coronae. 

The four circular lows from NE to SW, and 

from largest to smallest include: Umay-ene, 

Zemlika, Xcanil, and an unnamed corona at 

~39S/42.5E (here called CL45A). Umay-ene 

Corona (~370 km diameter), a double-ringed 

feature, displays a circular basin marked by two 

nested circular ridges, with an interior central 

peak (?). Umay-ene lacks radial fractures, 

although the surrounding region is cut by 

closely-spaced NE-trending regional fractures to 

the east, and ribbon tessera terrain to the west. 

Zemlika (~250 km diameter), marked by 

concentric structures and sharp topographic 

gradients, lacks radial features, and clearly 

crosscuts and hence post-dates ribbon tessera 

terrain. Xcanil and CL45A lie in the relatively 

featureless central V-45, southwest of Zemlika; 

both features display NE-trending fractures 

parallel to regional trends, but lack radial 

fracture suites. 

Radial coronae Mama-Allpa (NW corner; 

~200 km diameter), Mou-nyamy and Codidon 

(SE corner; each ~200 km diameter), and 

Inanna, (central-western V-45; ~200 km 

diameter) display raised interiors and radial 

fracture suites common among chained and 

clustered coronae, such as those along Parga and 

Hecate Chasmata [Hamilton & Stofan 1996]. 

Unlike their chained and clustered counterparts 

1
however, these radial coronae lack association 

with chasmata or volcanic rises. Gurshi Mons, 

which lies between the two SE radial coronae, 

appears similar to its neighbors. 

The topographic and structural difference 

between these two coronae subsets, circular lows 

and radial coronae, begs the question: How are 

geological histories of radial coronae and 

circular lows similar and/or different? How 

might documented differences contribute to 

differences in the mode of formation of these 

features? Can the differences be explained 

within the context of different stages of 

preservation of a similar mode of formation, or 

do geohistory differences require different 

modes or mechanisms of formation? 

If all coronae form via diapiric mechanism 

then circular lows might represent older more 

evolved coronae in which the interior has 

subsided and early-formed radial fractures are 

simply buried from obvious view. If circular 

lows represent a genetically different type of 

feature, then we should be able to determine this 

from detailed geological mapping and 

geohistory analysis. Circular lows might 

represent, for example, ancient impact features 

formed under different rheological conditions, 

either locally or globally defined. Or perhaps an 

entirely different hypothesis for the formation of 

either or both subsets of lowland coronae will 

emerge from the geological mapping and 

geohistory analysis. 

V-45 lowland tessera terrain: This terrain is 

divisible into at least two packages, northern 

tessera and southern tessera. Tessera outcrops, 

marked by penetratively developed tectonic 

fabrics occur at the highest altitude, and likely 

represent the oldest local deformation. Northern 

tessera host well-defined ribbon and fold fabrics 

typical of ribbon tessera terrain preserved in 

crustal plateaus. The southern tessera terrain 

hosts a similar, but possibly different fabric. The 

northern tessera terrain ribbons and folds 

describe regional patterns coherent over 100’s of 

km, yet the patterns show apparent truncation by 

one another. Locally linear tessera tracts mark 

asymmetric fabric similar to S-C shear fabrics. 

Both right-lateral and left-lateral shear directions 

are preserved. Tessera that lies along the crest of 

two nested curvilinear ridges record right-lateral 

shear, as do ENE-trending tessera fabrics to the 

east. But these regions show apparent crosscutting relations by WNW-trending Pasommana Tesserae ridges, which record apparent 

left-lateral shear. Xi-Wang-mu Tessera, which 

outcrops along a NE-trending high along the east 

boundary records local dextral shear, parallel to 

the trend of the ridge. Tushita Tesserae, which 

outcrops along a broad WNW-trending high to 

the south might record a confluence of NW- and 

NE-trending tessera fabrics. A region, mapped 

as flooded, or covered tessera terrain, occurs 

around much of the northern tessera; lineaments 

within this region typically parallel the trends of 

adjacent tessera structural patterns. The covered 

region commonly hosts numerous small shields, 

forming a thin veneer above tessera terrain 

below. 

The southern tessera lacks clear ribbon and 

fold fabrics, yet the penetrative tectonic fabric 

commonly marked by two or more lineaments 

trends is typical of tessera terrain. Locally 

ribbon and fold structures might be delineated 

with moderate confidence. Southern tessera 

occurs most extensively in the SW corner 

associated with Ekhe-Burkhan Corona, and 

outcrops as kipukas among flows of Sezibwa 

Vallis, and numerous shields in the region 

surrounding Tuzandi Mons. A penetrative radial 

fabric marks Tuzandi Mons reminiscent of 

tessera terrain, and tectonomagmatic centers 

preserved within the interior of Artemis (V-48); 

Tuzandi Mons may have formed synchronously 

with local tectonic fabric. 

Circular lows Umay-ene, Zemlika, and 

Xcanil clearly crosscut adjacent tessera terrain 

topography and tectonic fabric. The radial 

coronae are spatially separate from the tessera, 

and as such temporal relations are less certain; 

however, it appears that radial coronae likely 

post-date tessera formation. The incredibly sharp 

demarcation of the circular low features 

(topographic and tectonic) stands in strong 

contrast to the gradational character 

(topographic and tectonic) typical of the radial 

coronae—differences that could reflect: 1) 

marked difference in strength of the strong layer 

during feature formation, 2) strain rate of 

impacting body (endogenic or exogenic), or 3) 

direction of responsible forces (whether from 

above or below). Radial coronae and circular 

lows might reflect different genetic processes. 

2
GEOLOGIC MAPPING OF THE KAWELU PLANITIA (V-16) AND BELLONA FOSSAE (V-15) 

QUADRANGLES ON VENUS. J. R. Zimbelman, CEPS/NASM, Smithsonian Institution, Washington, D.C. 

20013-7012 (zimbelmanj@si.edu). 

Introduction: This report summarizes the 

current status of a Venus mapping project supported 

by NASA grant NAG5-11743 (the no-cost extension 

of which ended in April of 2006). Work during this 

past year has focused almost exclusively on the 

Kawelu Planitia map, but results from this work have 

application to the Bellona Fossae map as well. 

V-16, Kawelu Planitia: The revised map, text, 

description of map units (DOMU), correlation of map 

units (COMU), and figures for V-16 were submitted 

to the U.S. Geological Survey in March, 2007 (see 

Figs. 1 and 2). The revisions addressed the major 

Figure 1. 2007 version of the V-16 geologic map. 

Figure 2. 2007 version of the V-16 COMU. 

issues raised by reviewers and incorporated relevant 

literature that appeared since the map was originally 

submitted. Unfortunately, U.S.G.S. personnel soon 

found that the map contact lines did not match up to a 

digital base map for the quadrangle. After 

considerable discussion and work with the original 

map files, it was determined that the root cause 

appears to be the fact that the map is a composite of 

several revisions over the years, including major 

parts that were done on a photo print base rather than 

on a digital base product. It now appears that at best 

only a portion of the map line work can be matched 

to a digital base. We are now attempting to identify 

how to minimize the amount of new line work that 

will be required to get the entire map aligned with a 

digital base map. This is the unfortunate heritage of 

map work that began in the non-digital mapping era. 

We will work closely with U.S.G.S. personnel to get 

this map into an acceptable format as quickly as 

possible, but the need to redo line work means that 

this effort likely may take some time. 

V-15, Bellona Fossae: Essentially all efforts 

since the end of the no-cost extension of the mapping 

grant have gone into preparation of the V-16 

materials, described above. The V-15 map (Fig. 3) 

Figure 3. Current version of the V-15 geologic map. 

remains the same as what was presented at the 2006 

mappers meeting. We do not anticipate major 

changes being needed to the geology for this map, 

and it will also benefit greatly from the V-16 

materials for text, DOMU, and COMU preparations. 

We will pursue completion of this map for 

submission once the V-16 issues have been resolved. 
GLOBAL GEOLOGIC MAP OF EUROPA. T. Doggett1

, P. Figueredo1,*, R. Greeley1, T. Hare2, E. Kolb1, D. 

Senske3

, K. Tanaka2 and S. Weiser1, 1School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 2

U.S. Geological Survey, Flagstaff, AZ, 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, 

CA, (*currently at the ExxonMobil Research Company, Houston, TX.) 

Introduction: Europa, with its indications of a 

sub-ice ocean, is of keen interest to astrobiology and 

planetary geology. Knowledge of the global distribution and timing of Europan geologic units is a key step 

for the synthesis of data from the Galileo mission, and 

for the planning of future missions to the satellite. 

The first geologic map of Europa [1] was produced 

at a hemisphere scale with low resolution Voyager

data. Following the acquisition of higher resolution 

data by the Galileo mission, researchers have identified surface units and determined sequences of events 

in relatively small areas of Europa through geologic 

mapping [2-6] of images at various resolutions acquired by Galileo’s Solid State Imaging (SSI) camera 

[7]. These works [2-6] provided a local to subregional perspective and employed different criteria 

for the determination and naming of units. Unified 

guidelines for the identification, mapping and naming 

of Europan geologic units were put forth by [8] and 

employed in regional-to-hemispheric scale mapping 

[9,10] which is now being expanded into a global geologic map. 

Methodology: A global photomosaic [11] of Galileo and Voyager data was used as a basemap for mapping in ArcGIS, following suggested methodology of 

allostratigraphy for planetary mapping [12]. Due caution was exercised given that the mosaic has a resolution varying from 12.6 to 0.23 km per pixel (Fig. 1), as 

well as variations in illumination and viewing geometry, to avoid making distinctions between units that are 

artifacts of these variations. In areas of high resolution coverage, contacts were marked as definite, and 

left as queried in areas of low resolution coverage. 

The cut-off between these two mapping regimes is a 

resolution of 1.7km/pixel. 

Stratigraphy: The earliest epoch recorded on the 

current surface of Europa is typified by plains which 

appeared smooth at Voyager resolutions, but were 

shown to be intensely ridged at Galileo resolutions. 

The following epoch was dominated by the formation 

of widely spaced, wider lineae, according to a stratigraphic sequence derived for this work. The multiring impact crater Callanish sits early in the lineaforming period, while Tyre sits in the later stages. All 

other impacts appear to be younger than the lineaforming epoch. The most recent epoch includes the 

formation of chaos units, with implied genetic similarity, but are formally distinct in terms of stratigraphy, 

and photometric and resolution differences place a 

caveat on morphological comparisons. The stratigraphy for the youngest, chaos-forming epoch was separated into distinct regional provinces: 

(1) The trailing hemisphere equatorial province, dominated by the large chaos blocks of Annwn and Dyfed 

Regiones, inclusive of the archetypical Conamara 

Chaos, and the young Pwyll crater, whose rays and 

secondaries superimpose on the chaos. 

(2) The leading hemisphere equatorial province, dominated by the large chaos blocks of Powys and Tara 

Regiones, appearing as a rough counterpart to Annwn 

and Dyfed, though in addition to the resolution/photometry caveat, the differences in the space 

weathering environment between trailing and leading 

hemispheres almost certainly causes superficial differences in the appearances of the chaos units contrasted 

between the two provinces. 

 A dark unit, transected by lineae, is at the base of 

the stratigraphic sequence of both provinces, roughly 

centered on the sub-jovian and anti-jovian points respectively. This appears to indicate a phase of chaos 

formation prior to the linea-forming epoch. 

(3) The Argadnel Regio province, distinctive because 

of its densely packed ridges and bands in circular and 

semi-circular configurations and maculae such as 

Thrace and Thera Maculae. Features called microchaos [3] in this region are similar to the knobby chaos 

unit of other regional maps [9, 10]. 

(4) The north polar province, mostly poorly resolved, 

with some high resolution images showing ridges super-imposed on chaotic terrain, inferred to be similar 

to the ridged dark units at the anti- and sub-jovian 

points. 

(5) The south polar province, appears to be another 

regional-scale block of chaos, albeit poorly resolved. 

References: [1] Lucchitta and Soderblom, in The 

Satellites of Jupiter: 521, 1982; [2] Senske et al., LPSC

XXIX, #1743, 1998; [3] Prockter et al., JGR., 104: 

16531-16540, 1999; [4] Kadel et al., JGR, 105, 22657-

22669, 2000; [5] Figueredo et al., JGR, 107, 

10.1029/2001JE001591, 2002; [6] Kattenhorn, Icarus, 

157, 490-506, 2002; [7] Belton et al., Space Science 

Reviews, 60, 413-455, 1992; [8] Greeley et al., JGR, 

105, 22559, 2000; [9] Figueredo and Greeley, JGR, 

22629-22646, 2000; [10] Figueredo and Greeley, 

Icarus, 167, 287-312, 2004; [11] USGS, I-2757, 2003; 

[12] Skinner and Tanaka, LPSC XXXIV, #2100, 2003.
Figure 1: Differences in spatial resolution in the underlying dataset (Galileo/Voyager mosaic) used as base for the global geological map of Europa. 

Figure 2: Portion of global geological map of Europa in orthographic projection, centered on northern anti-jovian hemisphere, 

light blue represents global plains unit, darker blue and green represent disrupted (chaotic units), yellow represents impact craters, dark blue lines represent major lineaments, green dots represent lenticulae. 
THE GLOBAL GEOLOGIC MAP OF GANYMEDE. G. Wesley Patterson1

, James W. Head1, Geoffrey C. Collins2, 

Robert T. Pappalardo3

, Louise M. Prockter4, and Baerbel K. Lucchitta5, 1Department of Geological Sciences, Brown 

University, Providence, RI, 02912 (Gerald_Patterson@brown.edu), 2

Wheaton College, Norton, MA, 02766, 3Jet 

Propulsion Laboratory, Pasadena, CA, 91109, 4

Applied Physics Laboratory, Laurel, MD, 20723, 5USGS, Flagstaff, 

AZ, 86001. 

Introduction: The surface of Ganymede can generally 

be divided into two material types that exhibit 

differences in albedo, crater density, and surface 

morphology. Covering approximately a third of the 

surface is a lower albedo or dark material that is heavily 

cratered and commonly modified by the presence of 

large-scale arcuate fracture systems termed furrows. 

Crater density suggests dark materials represent the 

oldest preserved surfaces on Ganymede, though they 

generally have lower crater densities than neighboring 

Callisto, suggesting a limited amount of resurfacing [1]. 

The other two thirds of the surface are covered by vast 

globe-encircling swaths of a higher relative albedo or 

light material that has a crater density significantly 

lower than dark material. These swaths are themselves 

divided into polygons that range in appearance from 

relatively smooth to heavily modified by troughs 

termed grooves, at resolutions > 500 m/pixel. It has 

been suggested that light material formed 

predominantly through the modification of dark 

material by tectonic and cryovolcanic resurfacing 

processes [2]. 

The presence of this surface dichotomy leads to a 

number of fundamental questions about the formation 

and evolution of the surface of Ganymede. What is the 

origin of the albedo heterogeneity of the surface? How 

have dark and light materials evolved through time? 

What internal forces led to the formation of tectonic 

structures like furrows and grooves? Does the 

formation of grooves primarily reflect a local or global 

stress regime and how has that stress regime changed 

through time? What are the properties of craters on 

Ganymede and what are the relative age relationships 

among geologic features on the surface? 

Understanding the geological record of Ganymede is 

crucial to answering these questions. 

We have compiled a global geological map of 

Ganymede that represents the most recent 

understanding of the satellite on the basis of Galileo 

mission results. This contribution builds on important 

previous accomplishments in the study of Ganymede 

[e.g., 1, 3-9] and will help to provide constraints on 

models for the formation and evolution of Ganymede 

and potentially the other the Galilean satellites. 

Material units:

Dark material: Dark material is subdivided into 

three units for the global geologic map: A cratered unit 

(dc), a lineated unit (dl), and an undivided unit (d). 

This material has been heavily modified via impact 

processes (palimpsests, craters, basins, and related 

furrows), sublimation, mass wasting, and tectonism. 

Galileo high resolution images suggest that the dark 

material is composed of a relatively thin dark deposit 

overlying brighter icy material, and that it has been 

modified by surface processes such as sublimation, 

mass wasting, ejecta blanketing, and tectonism [8, 10]. 

Light material: Light material is subdivided into four 

units: A grooved unit (lg), a subdued unit (ls), an 

irregular unit (li), and an undivided unit (l). Light 

material forms swaths that cross-cut the older dark 

terrain and contain polygons 10s to 100s of kilometers 

wide, forming an intricate patchwork across the 

surface. Light material is primarily characterized by 

the density and orientation of structural grooves that 

exist within a given polygon. Light materials are 

interpreted to form from dark material via extensional 

tectonism, likely initiated along preexisting fractures 

(such as furrows). 

Reticulate terrain: This terrain consists of a single 

unit (r). It is often associated with and surrounded by 

bright grooved, bright subdued, and/or dark lineated 

units but can be distinguished from them by its variable 

albedo and presence of grooves with two dominant 

directions (typically near-orthogonal to each other). 

Reticulate terrain appears to represent dark and light 

material that has been modified by the formation of 

orthogonal sets of grooves. It has been suggested that 

the formation of reticulate terrain may be the result of 

subsequent episodes of extensional tectonism [1,6], or 

of block rotation within a distributed shear zone [11]. 

Impact material: Impact material is divided into 

three subunits: Crater, Palimpsest, and Basin material. 

These divisions are based on crater diameter, relative 

age, and differences in morphology. 

Crater material is subdivided based on relative albedo 

contrast with respect to surrounding materials and the 

presence of rays and continuous ejecta into degraded 

craters (c1), partially degraded craters (c2), and fresh 

craters (c3). A crater ejecta unit (ce) is also defined. 

Craters that cannot be categorized in this manner, most 

often due to resolution effects, constitute a fourth crater 

material unit: unclassified craters (cu). 

Palimpsest material is subdivided into four units: old 

palimpsests (p1), young palimpsests (p2), unclassified 

palimpsests (pu), and palimpsest interior plains (pi). 

The first two are categorized based on their crosscutting 

relationships with light materials, the third includes all 
other palimpsests, and the last represents the interior 

deposits of some palimpsests. 

Basin material represents units describing the ejecta 

from Gilgamesh basin and is subdivided into two units: 

Basin rugged material (br) and basin smooth material 

(bs). 

Stratigraphy: 

To determine age relationships among the various 

mapped units of the global map of Ganymede (Fig. 1), 

we utilized observed cross-cutting relationships and 

crater density measurements [12]. The conclusions 

drawn from these relationships and crater density 

measurements are broadly supported by previous crater 

counting efforts based on Voyager data [1,13]. 

Fig. 1. Correlation chart of Ganymede material units. 

Younger units are shown above older units; diagonal lines 

represent transitional or overlapping boundaries; ‘saw-tooth’ 

pattern indicates uncertain boundary ages.

References: [1] Shoemaker et al., Sats. of Jupiter, 435, 

1982; [2] Pappalardo et al., Jupiter, 363-396; [3] Guest et al., 

USGS Map I-1934, 1988; [4] Wilhelms, USGS Map I-2242, 

1997; [5] Lucchitta et al., USGS Map I-2289, 1992; [6] 

Lucchitta, Icarus, 44, 481-501, 1980; [7] Pappalardo et al., 

Icarus, 135, 276-302, 1998; [8] Prockter et al., Icarus, 135, 

317-344, 1998; [9] Murchie et al., JGR, 91, E222-E238, 

1986; [10] Prockter et al., JGR 105, 22,519-22,540, 2000; 

[11] Murchie and Head, JGR 93, 8795-8824, 1988; [12] 

Patterson et al., 38th LPSC, #1098 [13] Murchie et al., Icarus 

81, 271-297, 1989. 

Fig. 2. Preliminary geological map of Ganymede. Unit 

descriptions are given in the text 
THE GLOBAL GEOLOGIC MAP OF IO: APPROACH AND MAPPING STATUS. David A. Williams1

, 

Laszlo P. Keszthelyi2

, Paul E. Geissler2, Windy L. Jaeger2, Tammy L. Becker2, David A. Crown3, Paul M. Schenk4, 

and Julie A. Rathbun5

; 1School of Earth and Space Exploration, Arizona State University, Box 871404, Tempe, 

Arizona, 85287 (David.Williams@asu.edu); 2

Astrogeology Team, U.S. Geological Survey, Flagstaff, Arizona; 3

Planetary Science Institute, Tucson, Arizona; 4Lunar and Planetary Institute, Houston, Texas; 5University of Redlands, Redlands, California. 

Introduction: Jupiter’s volcanic moon Io is a challenging place to study using typical planetary mapping 

techniques, because of 1) rapid (in geologic terms) 

resurfacing from volcanic activity and 2) non-uniform 

coverage from multiple spacecraft flybys, resulting in 

a wide range of image resolutions and photometric 

properties. Nevertheless, because Io’s level of volcanic 

activity makes it unique in our Solar System, it is desirable to map its surface in order to complete a global 

reconnaissance of its surface features and material 

units and to understand better its geologic evolution. In 

this abstract we discuss our approach and progress in 

producing a global geologic map of Io. For production 

of our map, we are using a set of combined GalileoVoyager global mosaics and ArcGIS software. We are 

also creating a GIS database to contain all compatible 

Galileo, Voyager, and other Io data sets to show surface changes and aid in geologic interpretations. 

Background: Io, the innermost Galilean satellite of 

Jupiter, is the most volcanically active body in the Solar System. Tidal heating produces magma that feeds 

~300 active volcanic centers [1-3]. The 1979 Voyager

flybys observed ~25% of Io’s surface at resolutions of 

<2 km/pixel (the rest at 2-20 km/pixel: [4]), covering 

mostly the subjovian hemisphere. The Galileo mission 

(1996-2003) included five close flybys of Io, focused 

mostly on the antijovian hemisphere [5-7], with resolutions between ~10 m/pixel to 20 km/pixel. Previous 

geologic mapping of Io includes a series of four regional Voyager-based maps [8], a Voyager-based 

global map [9], and four Galileo-based regional maps 

[10]. 

The complementary coverage of Io by Voyager and 

Galileo has enabled the production of a series of high 

quality grayscale and color global mosaics. Our goal is 

to complement the new mosaics with a corresponding 

global compilation of geologic understanding at the 

end of the Galileo era. Geologic mapping is a tool that 

enables the definition and characterization of surface 

features into process-related material units and structures and places them within their stratigraphic context, allowing recognition of the geologic evolution of 

an area, region, or planet. 

Global Io Mosaics: The USGS Io global mosaics 

(1 km/pixel nominal resolution) are now the definitive 

global compilation of image products for Io. They consist of four distinct products: 1) a global mosaic of 

Galileo color images (756nm-green-violet as R-G-B, 

4 phase angle); 2) a global mosaic of the best resolution Galileo monochrome images; 3) a global mosaic 

of the best resolution Voyager and Galileo monochrome images; and 4) a merged product combining 

Galileo color information with the higher resolution 

monochrome images. Each of these four products is 

available as an ISIS cube in Sinusoidal, Mercator and 

Polar Stereographic projections (both north and south 

pole). An extensive set of ancillary data was developed 

for all of these mosaics to help users understand the 

various combinations of data from different sensors, 

filters, dates, and illumination and viewing geometries. 

These include footprint plots showing the identity of 

each of the component images and diagrams that show 

the incidence, emission, and phase angles, along with 

the spatial resolutions of the individual frames used. 

Strategies for Global Mapping: After analysis of 

all previous geologic maps and study of the new global 

mosaics, we developed the following strategy for 

global mapping. All mapping is done using ArcMap 

software, part of the ArcGIS package by ESRI: 

1) Map diffuse deposits using Galileo global color 

data. This is done because of the wide variety of diffuse deposits on Io (black, yellow, white, red, green), 

which are thought to represent distinct compositions 

(silicates, sulfurous materials, SO2-dominated materials, short-chain sulfur allotropes, products of silicate/sulfur interaction, respectively). 

2) Map mountains, surrounding plateaus, and 

structural features using various mosaics. Various 

image products are used to identify mountains, layered 

plateaus, and other materials delineated by scarps and 

other structural features, because they have nearly the 

same color and texture as background plains and cannot be identified except in images taken during low 

solar incidence angles. 

3) Map vents and paterae using various mosaics.

4) Map lava flow fields using various mosaics. We 

first map the outermost boundaries of each flow field 

around a vent, followed by the addition of more detail 

(individual lobate flow margins, fresher interior flows) 

as the available resolution permits. Active or recently 

active flows are identified by the following criteria: 1) 

observed surface changes in images obtained at different times; 2) thermal anomalies detected in NIMS data; 

and/or 3) an observed plume source at or near the flow 

margins. 

5) Map plains. The bright plains include everything 

not mapped in the previous categories, and are thought 

to consist of silicate crust mantled by various S-
GLOBAL GEOLOGIC MAPPING OF IO: D.A. Williams et al. 

bearing materials [10]. The primary interpatera Plains 

Material has three subunits based on color (Yellow, 

White, and Red-Brown); Layered Plains are composed 

of plateaus separated from surrounding plains by 

scarps and are thought to be produced by degradational processes [11]. 

Mapping Progress: We have mapped the polar regions of Io (±57.5 -90 ) as of May 2007. The following summarizes our results: 

In general, Io displays five primary types of morphological units: plains, patera floors, flows, mountains, and diffuse deposits. Plains materials cover 

~86% of Io’s surface in the polar regions. The greatest 

percentage (79%) consists of radiation-altered RedBrown Plains, with lesser amounts of White Plains 

(SO2-dominated, 3%) and Bright (yellow) Plains (sulfur-dominated, 2%). Eroded plateaus, or Layered 

Plains, make up ~3% of the polar regions. 

Patera floors have a range of albedos and colors in 

the polar regions, and are mapped as Bright (presumably sulfur-covered, 0.3%), Dark (presumably silicatecovered, 0.3%), and Undivided (0.8%). There are suggestions of additional paterae in the polar regions, 

based on albedo and color differences in the mosaics, 

but confirmation must await more high-resolution coverage. Patera floors range from bright white to yelloworange to dark black in Galileo images, in which the 

colors suggest various compositions, including mixes 

of silicates, sulfurous compounds, and relatively pure 

sulfur dioxide in some cases [12]. Heno Patera 

(57.1 S, 311.5 W), a 71.1 km diameter patera, has a 

dark floor and dark flows that surround a circular feature approximately centered on the patera floor. We 

speculate that this may be the site of an impact that is 

experiencing modification by volcanism. 

There are significant expanses of Bright Lava Flow 

materials in the polar regions (3% of all mapped polar 

units), thought to be indicative of sulfur volcanism. 

The area of the Bright Flows is twice that of the Dark 

Flows (silicate-dominated, ~1%), although Undivided 

Flows (units with intermediate albedos and colors) 

make up another 6% of polar materials. These mapping results suggest that lava flows outside paterae 

may have a greater role in resurfacing Io than previously thought. Many polar bright flow fields are not 

directly adjacent to dark flows, perhaps indicative of a 

significant component of primary sulfur volcanism. 

Lithologically, Patera Floor materials and Lava Flow 

materials are probably identical in composition. However, their distinctive geologic settings justifies separating them on the global map. 

In the polar regions, Lineated Mountain materials 

make up about ~2% of the surface. By number there 

are more mountains identified in the south polar region, due to the better Voyager imaging (i.e., need 

right illumination & resolution). Mottled and Undivided Mountain materials each make up <1% of the 

polar areas. Lineated Mountain materials are topographically-distinct massifs (relative to layered plains) 

containing ridges, grooves, scarps, and lineaments on 

positive-relief edifices. This unit is interpreted as tectonically-disrupted sections of crust containing planar 

structural features, possibly faults involved in uplift 

and/or collapse during mountain formation [2]. Massifs with no visible patterns are classified as Undivided. Mottled Mountain materials have smoother surfaces lacking lineations and indicative of mass wasting 

processes. No volcanic mountains (Tholus, Cone, or 

Shield materials) were recognized in the polar regions. 

The polar regions contain extensive diffuse deposits, which cover 16.5% of the surfaces of other units. 

White Diffuse deposits are thought to be dominated by 

SO2-rich frosts, and make up 64% of all diffuse deposits at the poles. They usually occur at the margins of 

lava flows or around paterae, but also make up extensive halos around some mountains. Yellow Diffuse 

deposits are likely composed of some combination of 

sulfur-rich materials and SO2, albeit less SO2 than 

White deposits. Only 10% of diffuse deposits at the 

poles are yellow, and these are less extensive than in 

equatorial regions. Red Diffuse deposits occur as 

ephemeral mantles around active vents, and make up 

~10% of polar diffuse deposits. There are the remnants 

of two faint red rings in the north polar region, one 

surrounding Dazhbog Patera (which erupted during the 

Galileo I31 flyby) and one around an unnamed patera 

at 70 N, 55 W. They have been interpreted as pyroclastic deposits rich in metastable, S3 and S4 allotropes, 

which are red when quenched from magmatic S2 gas 

[13], possibly also containing Cl-bearing materials at 

some vents [14]. Dark Diffuse deposits are interpreted 

as pyroclastic deposits derived from silicate lavas [15], 

and cover ~16% of the area of polar units.

A wide range of structural features can be identified in the polar regions of Io, including scarps, ridges, 

lineaments, and circular depressions (pits and patera 

rims). The additional low-sun observations and higher 

resolution of the Galileo camera has enabled recognition of these and other structural features over a wider 

part of Io’s surface than was previously possible.

References: [1] Radebaugh et al., 2001, JGR 106, 33,005-33,020; [2] 

Schenk et al., 2001, JGR 106, 33,201-33,222; [3] Lopes et al., 2004, Icarus 

169/1, 140-174; [4] Smith et al., 1979a,b, Science 204, 951-972, & Science

206, 927-950; [5] McEwen et al., 2000, Science 288, 1193-1198; [6] Keszthelyi et al., 2001, JGR 106, 33,025-33,052; [7] Turtle et al., 2004, Icarus, 169/1, 

3-28; [8] Moore, H.J., 1987, USGS Map I-1851, 1:1,003,000; Greeley, R., et 

al., 1988, USGS Map I-1949, 1:2,000,000; Schaber, G.G., et al., 1989, USGS 

Map I-1980, 1:5,000,000; Whitford-Stark, J.L., et al., 1991, USGS Map I2055, 1:5,000,000; [9] Crown, D.A., et al., 1992, USGS Map I-2209, 

1:15,000,000; [10] Williams, D.A., et al., 2002, JGR 107, 5068, 

doi:10.1029/2001JE001821; Williams, D.A., et al., 2004, Icarus 169, 80-97; 
Williams, D.A., et al., 2005, Icarus 177, 69-88; Williams, D.A., et al., 2007, 

Icarus, 186, 204-217; [11] Moore et al., 2001, JGR 106, 33,223-33,240; [12] 

Carlson, R.W., et al., 1997, GRL 24, 2479-2482; [13] Spencer et al., 2000, 

Science 288, 1208-1210; [14] Schmidt & Rodriguez, 2003, JGR 108, 5104, 

doi: 10.1029/2002JE001988; [15] Geissler et al., 1999, Icarus 140, 265-282. 
USE OF CLEMENTINE UVVIS AND NIR DATA FOR LUNAR GEOLOGIC MAPPING. 

Lisa Gaddis, Astrogeology Team, U.S. Geological Survey, Flagstaff, AZ 86001 

(lgaddis@usgs.gov). 

Introduction: The Clementine global, 11-band 

mosaic is now available at ~100 m/pixel for 5 

ultraviolet-visible (UVVIS) wavelengths (415, 750, 

900, 950, and 1000 nm; [1]) and 6 near-infrared 

(NIR) wavelengths (1100, 1250, 1500, 2000, 2600, 

and 2780 nm; [2]). The Clementine UVVIS mosaic 

is available online at the Map-a-Planet 

(http://www.mapaplanet.org/explorer/moon.html)

and the Planetary Image Atlas (http://pdsimaging.jpl.nasa.gov/Missions/Clementine_mission

.html) Web sites of the Planetary Data System 

(PDS). The NIR mosaic is available online at 

http://astrogeology.usgs.gov/Projects/ClementineNI

R/ and it is now being reviewed prior to release by 

PDS. Although additional processing of these data 

may yet occur, the data quality is such that firstorder analyses can be made [e.g., 3, 4]. These 

multispectral data are well-suited for use in lunar 

geologic mapping [e.g., 5]. 

Color Data for Lunar Mapping: Color 

information at multiple wavelengths has been used 

for some time to characterize and map geologic 

units on Earth [e.g., 6 and references therein]. For 

the Moon, color information was provided by 

Earth-based imaging and telescopic data [e.g., 7] 

and Apollo cameras prior to the Galileo mission 

and the acquisition of multispectral data by the 

Solid State Imager (SSI; [8]). In 1994 the 

NASA/DOD Clementine Mission acquired the first 

global color data for the Moon using the UVVIS 

and NIR cameras [9]. 

Mineralogy: Clementine UVVIS and NIR 

wavelengths were selected to maximize information 

on the mineralogy of lunar units (Figure 1). 

Pyroxenes have two absorption bands at these 

wavelengths, one centered near 1 micron and 

another near 2 microns; these band centers move to 

longer wavelengths as Ca and Fe substitute for Mg 

[e.g., 10]. Olivine has an absorption band centered 

beyond 1.05 micron that moves as Fe substitutes for 

Mg [11]. Significant amounts of olivine in lunar 

soils will broaden the pyroxene absorption at 1 

micron and shift it to longer wavelengths. Because 

olivine lacks a band at 2 microns, the 1 micron 

absorption in olivine-rich lunar deposits will be 

strengthened relative to the 2 micron band. The 

presence of iron-rich volcanic glasses causes 

~broad, shallow absorption bands in lunar soils 

because of the amorphous structure of the glasses 

[e.g., 12]. As the most abundant opaque mineral in 

lunar soils, ilmenite lowers their albedo and 

spectral contrast, and causes the typically red (i.e., 

sloping toward shorter wavelengths) lunar spectra 

to become less red [e.g., 13]. The presence of 

abundant plagioclase increases the albedo and alters 

other spectral properties of lunar soils. 

Figure 1. Laboratory reflectance data for common lunar 

minerals with Clementine UVVIS and NIR bandpasses 

superimposed. (after Pieters, Ch. 14, in [7]).

Maturity: Space weathering on the lunar surface 

has a significant influence on lunar soils, and 

causes them to appear more mature with time [e.g., 

14, 15]. Comminution, production of agglutinates, 

and addition of coatings of amorphous silica with 

submicroscopic metallic iron all act to produce 

‘mature’ lunar soils. Remote spectra of such soils 

are redder and have lower albedos and lower 

spectral contrast [16]. To understand the meaning 

of color variations in analyses of lunar soils, the 

effects of both maturity and particle size must be 

considered. 

Unit Identification and Characterization: Singleband Clementine images, particularly the 750-nm 

‘albedo’ mosaics, provide first-order compositional 

information and allow distinction between mare 

and highland units, low- and high-titanium maria, 

fresh vs. ancient craters, and some relative age 

relationships. Soil maturity is a major factor at 750 

nm and this has allowed Lucey and others [17] to 

derive an ‘optical maturity’ (OMAT) parameter 

from the UVVIS data at 750 and 950 nm. These 

OMAT views have been used to determine relative 

ages of lunar craters [14, 18] and to refine the age 

of the stratigraphic boundary between the 

Copernican and Eratosthenian [e.g., 19] epochs on 

the Moon. Gillis and Lucey [20] note that the 2780 

nm NIR data are particularly useful for 

distinguishing between mare basalt units on the 

basis of composition and without major soil 
maturity effects. Analyses of crater ray brightness 

and distribution at the 2780 nm wavelength may be 

especially helpful for relative age assessment of 

lunar units. 

Additional map bases derived from the Clementine 

data include the UVVIS “standard” color-ratio 

views (R=750/415; G=750/950; B=415/750) that 

cancel out the dominant brightness variations of the 

scene (controlled by albedo variations and 

topographic shading) and enhance color differences 

related to soil mineralogy and maturity [e.g., 21]. 

In these views, lunar highlands, mostly old (~4.5 

b.y.) anorthositic rocks, are depicted in shades of 

red (older) and blue (younger). The lunar maria 

(~3.9 to ~1 b.y.), mostly iron-rich basaltic materials 

with varying titanium content, are portrayed in 

shades of yellow/orange (iron-rich, lower titanium) 

and blue (iron-rich, higher titanium). Superimposed 

on and mixed with these materials are those from 

basins and craters of various ages, ranging from the 

dark reds and blues of ancient basins to the bright 

blue rays of younger craters. More sophisticated, 

Clementine-derived maps include those based on 

FeO and TiO2 content [17, 20, 22, 23, 24]. ‘Rock 

type’ [25], petrologic [26] and mineral maps [27] 

have also been derived from Clementine UVVIS 

data and used to identify and characterize geologic 

units and features on the Moon. 

Visualization and analysis techniques developed for 

use with terrestrial multi- and hyperspectral data 

can be used to further characterize and identify 

geologic units on the Moon with Clementine color 

data. For example, using spectral scatterplots [e.g., 

28] allows segregation of mature and immature 

lunar soils, and identification of spectral endmembers of unique, spatially coherent units. Linear 

unmixing methods have also been applied to 

Clementine color data to distinguish 

compositionally ‘pure’ units from those of mixed 

lithologies [e.g., 29]. Geographic Information 

Systems (GIS) methods have also been applied to 

the analysis of lunar Clementine and numerous 

other digital datasets [e.g., 5, 30, 31]. Lunar GIS 

databases are available to facilitate mapping, data 

processing and analysis, and mission support 

activities (see http://webgis.wr.usgs.gov/pigwad/-

maps/the_moon.htm, and especially the lunar data 

download site at http://webgis.wr.usgs.gov/pigwad-

/down/moon_dl.htm). 

Summary: Clementine data for mature and 

immature lunar soils provide information on the 

shape and position of the 1-micron band and the 

strength of the 1- and 2-micron bands. Analyses of 

the UVVIS and NIR data will provide better 

discrimination of the presence of high- and lowcalcium pyroxenes, olivine, ilmenite and Fe-rich 

glass and plagioclase in lunar soils. These data thus 

provide a viable tool for characterizing and 

mapping lunar geologic units at ~high spatial 

resolution (≤200 m/pixel). 

References: [1] Eliason et al. 1999, PDS Vol. 

USA_NASA_PDS_CL_4001 to 4078. [2] Gaddis et 

al., 2007, PDS Volumes 

USA_NASA_PDS_CL_5001 through 5078. [3] 

Cahill et al., 2004, LPS XXXV, abs. # 1469. [4] 

Staid et al., 2003, LPS XXXIV, abs. #1767. [5] 

Gaddis et al., 2006, LPS XXXVII, abs. #2135. [6] 

Rencz, A.N. (ed.), 1999, Man. Rem. Sens., 3rd Ed., 

V. 3, 707 pp. [7] Pieters and Englert (eds.), 1993, 

Rem. Geochem. Anal.: Elem. And Min. Comp., 

Cambridge Univ. Press. [8] Pieters et al., 1993, J. 

Geophys. Res. 98, 17,127. [9] Nozette et al., 1994, 

Science, 266, 1777. [10] Cloutis and Gaffey, 1991, 

J. Geophys. Res., 96, 22809. [11] Burns, 1993, 

Min. App. Of Crystal Field Theory, Cambridge 

Univ. Press. [12] Bell et al., 1976, Proc. Lun. Sci. 

Conf. 7th, 2543. [13] Wilcox et al., 2006, J. 

Geophys. Res., 111, E09001, 

doi:10.1029/2006JE002686. [14] Blewett et al., 

2005, J. Geophys. Res., 110, E04015, 

doi:10.1029/2004JE002380. [15] Lucey et al., 

2006, Rev. Min. Geochem., 60, 83. [16] Fischer 

and Pieters, 1994, Icarus 111, 475. [17] Lucey et 

al., 2000, J. Geophys. Res., 105, E8 20377. [18] 

Grier et al., 2001, J. Geophys. Res., 106, E12, 

32847. [19] Hawke et al., 2007, LPS XXXVIII, 

abs. # 1133. [20] Gillis and Lucey, 2004, LPS 

XXXV, abs. #2158. [21] Pieters et al., 1994, 

Science, 266, 1844. [22] Lucey et al., 1995, J. 

Geophys. Res., 103, 3679. [23] LeMouelic et al., 

2000, Jour. Geophys. Res., v. 105, 9445. [24] 

Wilcox et al., 2005, Jour. Geophys. Res., v. 110, 

doi:10.1029/2005JE002512. [25] Pieters et al., 

2001, J. Geophys. Res., 106(E11), 28,001–28,022. 

[26] Zellner et al., 2002, J. Geophys. Res., 

107(E11), 5102, doi:10.1029/2001JE001800 [27] 

Lucey, 2004, Geophys. Res. Lett., 31, L08701, 

doi:10.1029/2003GL019406. [28] Staid and Pieters, 

2001, J. Geophys. Res. 106, 27887. [29] Li and 

Mustard, 2000, J. Geophysical Res., Vol. 105, 

20,413-20,450. [30] Hare et al., 2007, Lunar Expl. 

Arch. Wkshp., Tempe, AZ, March 2007. [31] 

Skinner et al., 2005, LPS XXXVI, abs. #2344. 
REMOTE SENSING STUDIES OF COPERNICUS RAYS: IMPLICATIONS FOR THE CALIBRATION 

OF THE LUNAR STRATIGRAPHIC COLUMN. B.R. Hawke1

, T.A. Giguere1,2, L.R. Gaddis3, B.A. Campbell4, 

D.T. Blewett5

, J.M. Boyce1, J.J. Gillis-Davis1, P.G. Lucey1, C.A. Peterson1, M.S. Robinson6, and G.A. Smith1, 1

Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822, 2Intergraph 

Corporation, P.O. Box 75330, Kapolei, HI 96707, 3

U.S. Geological Survey, Astrogeology Program, 2255 N. Gemini 

Drive, Flagstaff, AZ 86001, 4

Center for Earth and Planetary Studies, National Air and Space Museum, Washington, 

D.C. 20560, 5

NovaSol, 733 Bishop Street, Honolulu, HI 96813, 6School of Earth and Space Exploration, Box 

871404, Tempe, AZ 85287-1404. 

Introduction: The nature and origin of lunar 

rays have long been the subjects of major 

controversies. We have been investigating the origin 

of lunar crater rays in support of the new Lunar 

Geologic Mapping Program. In an effort to better 

understand the processes responsible for the 

formation of lunar rays, we have utilized a variety of 

remote sensing data to study selected rays. 

Clementine UV-VIS images were used to produce 

high-resolution FeO, TiO2, and optical maturity 

(OMAT) maps for the various rays utilizing the 

methods presented by Lucey et al. [1, 2]. Near-IR 

spectra and 3.8- and 70-cm radar maps were also 

utilized [3, 4]. Our preliminary finding resulted in a 

model for lunar ray formation [5, 6]. It was found 

that lunar rays are bright because of compositional 

contrast with the surrounding terrain, the presence of 

immature debris, or some combination of the two. 

The purpose of this report is to present the results of 

studies of Copernicus rays, to assess the implications 

for the calibration of the lunar stratigraphic column, 

and to reevaluate the ages of large craters in Mare 

Imbrium. 

The Origin of Copernicus Rays in Mare 

Imbrium: Copernicus is a large bright-rayed crater, 

93 km in diameter, located at 9.5o N, 20.0o W on the 

lunar nearside, and has long been used as a 

stratigraphic marker for lunar geology [7, 8, 9]. 

Continuous ejecta deposits occur up to a crater 

diameter away from the rim crest of Copernicus, 

while the ray system extends radially for more than 

500 km [9]. We have investigated the Copernicus 

rays that extend north across the surface of Mare 

Imbrium with particular emphasis on four major rays. 

Two of these rays (Rays 1 and 2) extend north of 

Copernicus, and two (Rays 3 and 4) extend to the 

northeast. The albedo of the rays varies from 

moderate to high, and all exhibit numerous secondary 

craters which range in diameter from 200 m to 7.0 

km.

The rays north of Copernicus (Rays 1 and 2) 

exhibit moderate to strong returns in the 3.8-cm 

depolarized radar image mosaic. The highest values 

are associated with secondary crater clusters. These 

areas have greater abundances of 1- to 40-cm-sized 

fragments in the upper 0.5 m of the regolith. Portions 

of Rays 1 and 2 exhibit slightly enhanced backscatter 

in the depolarized 70-cm radar image. The strongest 

enhancements are associated with secondary crater 

clusters. These enhancements have an excess of 

meter-sized blocks within 5-10 m of the surface. 

The Copernicus rays in Mare Imbrium exhibit 

lower FeO and TiO2 values than do the adjacent mare 

deposits. The background mare flows have FeO 

values that range between 17 and 19 wt.% and TiO2

concentrations that range between 4 and 6 wt.%. The 

rays north of Copernicus have FeO abundances that 

vary from 12 to 16 wt.% and TiO2 values that range 

from 2 to 4 wt.%. The FeO and TiO2 concentrations 

generally show a negative correlation with the albedo 

values exhibited by the ray surfaces. FeO 

abundances generally increase along a given ray as a 

function of distance from Copernicus. The measured 

FeO value (8.0 wt.%) for the Copernicus ejecta 

blanket can be used to calculate the amount of 

highland-rich primary ejecta in the rays north of 

Copernicus. The calculated abundances of primary 

ejecta range from 20% to 60%. 

The optical maturity (OMAT) images of the 

Copernicus rays indicate that relatively high OMAT 

values are associated with secondary crater chains 

and clusters. The highest values are exhibited by 

steep slopes on the crater interiors. Apparently, 

downslope movement on the interior crater walls 

constantly adds fresh material to the regolith. Ray 

surfaces away from the interiors of secondary craters 

display much lower OMAT values. These OMAT 

values are slightly higher than those exhibited by 

fully mature background mare surfaces near the rays. 

The rays of Copernicus in Mare Imbrium have not 

reached full optical maturity. 

In summary, the Copernicus rays in Mare 

Imbrium display relatively low FeO and TiO2 values 

because of the presence of variable amounts of 

highland-rich primary ejecta. The rays exhibit 

relatively low OMAT values except for areas with 

secondary crater clusters. Still, the rays are not fully 

mature. The Copernicus rays are bright largely due 

to contrast in albedo between the ray material 

containing highland-rich primary ejecta and the 

adjacent dark mare surfaces. 

Implications for the CopernicanEratosthenian Boundary: The working distinction 

between the Eratosthenian (E) and Copernican (C) 
Systems is that Copernican craters have visible rays 

whereas Eratosthenian-aged craters do not [7, 11, 

12]. Since compositional rays can persist for 3 Ga or 

more, the mere presence of bright rays is not a 

reliable indicator that a crater was formed during the 

C Period [6, 9, 13, 14, 15]. It is clear that a new 

method is required to distinguish C- from E-aged 

craters. It has been suggested that the OMAT 

parameter be used to define the C-E boundary [6, 14, 

15]. With increasing age, the OMAT values for 

ejecta and rays decrease and eventually become 

indistinguishable from the background value, which 

is the optical maturity index saturation point [2, 15]. 

The time required for a fresh surface to reach the 

optical maturity index saturation point could be 

defined as the Copernican Period. Surfaces that have 

reached full optical maturity would then be of 

Eratosthenian (or greater) age. Grier and co-workers 

[14, 15] noted that if the ejecta of Copernicus were 

slightly more mature, it would be indistinguishable 

from the background in an OMAT image. Our 

results for the Copernicus rays in Mare Imbrium are 

consistent with these findings. Hence, the saturation 

of the optical maturity index may occur at about 0.8 

Ga, which is the commonly accepted age of 

Copernicus [16, 17, 18]. 

A Reevaluation of Lunar Crater Ages: 

Because of the new definition of the C-E boundary, 

we have investigated the ejecta and rays associated 

with a number of large craters in Mare Imbrium. Our 

purposes were to determine the compositions and 

maturity states of the rays and to assess the ages of 

the parent craters in light of the new criteria. 

Aristillus, Autolycus, and Theaetetus are located 

north of the Apollo 15 site. They have been mapped 

as Copernican craters based on the presence of rays 

[8, 10, 12]. The high-albedo rays of Aristillus, 

Autolycus, and Theaetetus contain highland material 

and are bright because of compositional contrast with 

the surrounding mare terrain. The rays and ejecta of 

these craters have reached full optical maturity. 

Hence, Aristillus, Autolycus, and Theaetetus are 

older than Copernicus and should be mapped as 

Eratosthenian-aged craters. 

Timocharis (D=34km) and Euler (D=28 km) 

were mapped as Copernican-aged craters by Carr 

[19] and Wilhelms and McCauley [8] because they 

exhibit bright ejecta and rays. However, Wilhelms 

[20] recommended that they be assigned an 

Eratosthenian age. Portions of the ejecta deposits of 

Euler and Timocharis are bright because they contain 

FeO-poor highlands material. The OMAT data 

indicate that the ejecta and rays of both craters have 

reached full optical maturity. Hence, Euler and 

Timocharis should be mapped as Eratosthenian-aged 

craters. Unlike Euler and Timocharis, Lambert 

(D=30 km) excavated only FeO-rich mare material 

and does not exhibit bright rays. The OMAT image 

shows that Lambert ejecta is fully mature. Lambert 

was correctly mapped as an Eratosthenian crater by 

previous workers [8,19,20]. 

Pytheas (D=20 km) has been mapped as a 

Copernican-aged crater [8,19,20] because it exhibits 

bright ejecta deposits. FeO and TiO2 maps indicate 

that the high-albedo portions of the Pytheas ejecta 

blanket contain abundant highland material. The 

OMAT data indicate that these highlands-rich 

deposits are fully mature and are bright only because 

of compositional contrast with the adjacent mare 

terrain. Since the Pytheas ejecta and rays have 

reached full optical maturity, it should be assigned an 

Eratosthenian age. An Eratosthenian age for Pytheas 

is confirmed by crater size-frequency values. 

Delisle (D=25 km) and Diophantus (D=18 km) 

have been mapped as Eratosthenian-aged craters 

because they lack well-defined rays [e.g.,8]. It is not 

possible to determine the true degree of maturity of 

the Diophantus ejecta deposit because it is largely 

covered by immature ejecta from small, superposed 

craters such as Diophantus C as well as Aristarchus 

and Copernicus rays. However, those portions of the 

Delisle ejecta blanket not covered with fresh, small 

crater ejecta appear to be fully mature. 

References: [1] Lucey P. et al. (2000) J. 

Geophys. Res., 105, 20,297. [2] Lucey P. et al.

(2000) J. Geophys. Res., 105, 20,377. [3] Zisk S. et 

al. (1974) Moon, 10, 17. [4] Campbell B. and Hawke 

B. (2005) J. Geophys. Res., 110, E09002. [5] Hawke 

B. et al. (2006) LPSC 37, #1133. [6] Hawke B. et al. 

(2004) Icarus, 170, 1. [7] Shoemaker E. and 

Hackman R. (1962) The Moon-Sym. 14 of the I.A.U., 

289. [8] Wilhelms D. and McCauley J. (1971) 

U.S.G.S. Map I-703. [9] Pieters C. et al. (1985) J. 

Geophys. Res., 90, 12,393. [10] Page N. (1970) 

U.S.G.S. Map I-666. [11] Ryder G. et al. (1991) 

Geology, 19, 143. [12] Wilhelms D. (1987) U.S.G.S. 

Prof. Pap., 1348. [13] McEwen A. et al. (1993) J. 

Geophys. Res., 98, 17,207. [14] Grier J. and 

McEwen A. (2001) Accretion of Extraterrestrial 

Material Throughout Earth History, 403. [15] Grier 

J. et al. (2001) J. Geophys. Res., 106, 32,847. [16] 

Eberhardt P. et al. (1973) Moon, 8, 104. [17] Bogard 

D. et al. (1994) GCA, 58, 3093. [18] Stoffler D. and 

Ryder G. (2001) Space Sci. Rev., 96, 9. [19] Carr M. 

(1965) U.S.G.S. Map I-462. [20] Wilhelm D. (1980) 

U.S.G.S. Prof. Pap., 1046-A. [21] Neukum G. and 

Konig B. (1976) Proc. Lunar Sci. Conf., 7th, 2867. 
GEOLOGY OF MTM QUADRANGLES -40277, -40272, -45277, AND -45272, EASTERN HELLAS 

PLANITIA, MARS. Leslie F. Bleamaster III1,2, and David A. Crown1

, Planetary Science Institute, 1

corporate address - 1700 E. Ft. Lowell Rd., Suite 106, Tucson, AZ 85719; 2mailing - 3635 Mill Meadow 

Dr., San Antonio, TX 78247, lbleamasPSI@satx.rr.com. 

Introduction: Geologic mapping studies at the 

1:1M-scale are being used to characterize geologic 

processes that have shaped the highlands 

surrounding the Hellas impact basin and, in 

particular, to evaluate landforms and deposits 

resulting from modification of highland terrains by 

volatile-driven degradation. Specific research 

objectives for geologic mapping of MTM 

quadrangles -40277, -40272, -45277 and -45272, 

located in eastern Hellas Planitia, include: 1) to 

reconstruct fluvial systems that dissect the Hellas 

rim, 2) to characterize the extensions of Dao and 

Harmakhis Valles onto the basin floor and to 

identify, if present, sediments contributed to Hellas 

Planitia from the rim, 3) to investigate the nature of 

the boundary between the east rim and Hellas 

Planitia in order to infer its mode of origin, age, and 

history of modification, and 4) to use small-scale 

surface morphology and small crater populations to 

examine finely layered deposits, local erosion, and 

burial/mantling/exhumation of surfaces. This 

mapping study builds on previous mapping in 

eastern Hellas [1-10] and facilitates comparisons 

between the geologic history of the east rim, the 

remainder of the rim, and Hellas Planitia. 

Mapping Region: The map area includes the 

terminal portions of Dao and Harmakhis Valles and 

their floor deposits, dissected and channeled plains 

materials, and deposits associated with the Hellas 

basin floor. Following the mapping precedents of [3 

and 8], materials in MTM -40277, -45277, and -

45272 (and -40272 [8]) quadrangles have been 

divided into two major geologic assemblages: the 

Hellas rim assemblage (3 units) and the Hellas floor 

assemblage (3 units). The contact between these 

assemblages occurs at a prominent topographic 

break near the -5800 meter contour. In addition, 

valles and channel materials (7 units), and crater 

materials (3 units) have been defined. At 1:5Mscale, materials within this region above -5800m 

were mapped as the Hesperian/Noachian dissected 

unit, member 1; below -5800m, materials were 

mostly mapped as the Hesperian smooth interior 

unit [3]. Mapping at 1:1M-scale by Price [8] 

subdivided the dissected unit (rim assemblage) into 

Hesperian smooth plains (unit Hps) and 

Hesperian/Noachian hummocky plains (unit HNh), 

but did not evaluate any of the floor assemblage. 

Figure 1. Geologic map of MTM quads –40277, -45277, -45272, 

and –40272. Rim/floor assemblage boundary runs from the upper 

left to lower right. Red stars represent finely layered outcrops. 

Hellas rim assemblage. Using THEMIS IR and 

VIS data, we have evaluated the contacts of units 

Hps and HNh mapped by Price [8] and have 

extended these unit boundaries westward from 

MTM -40272 to the rim/floor boundary. These two 

areally expansive units (new designations of HNps 

and Nph, respectively) surround the distal portions 

of the Dao and Harmakhis Valles canyon systems. 

The hummocky plains (unit Nph) display 10s to 

100s of meters of relief and are located more near 

the rim/floor assemblage boundary and within highstanding inselbergs along the floor. Nph is bound by 

elevations –5200m and –5800m. Outcrops of finely 

layered materials are exposed in local high standing 

mesas, knobs, and surfaces near -5700±100m within 

the hummocky plains. The smooth plains (unit 

HNps) superpose unit Nph and are correlated with 

the locations of small-scale surface channels. The 

exposure, elevation, and spatial concentration of the 

layered deposits with unit contacts between units 

Nph and HNps (Fig. 1) suggest that the isolated 

layered outcrops most likely represent remnants of a 

once laterally continuous deposit of the smooth 

plains (unit HNps) that was part of a more 

widespread depositional shelf in eastern Hellas [11]. 

Removal of the upper smooth plains surface exposes 

the hummocky plains either by down cutting from 

channels, scarp retreat and aeolian erosion, and/or 
collapse from loss of volatiles. Although it is 

unclear if the smooth plains channels are responsible 

for emplacing the smooth plains (i.e., bank-full 

deposits) or if they simply cut the smooth plains 

(most likely both circumstances exist), the smallscale channels within the smooth plains likely 

represent the first stage in canyon development and 

hummocky plains exposure [11]. 

In the SE corner of the map area, the division 

between the rim and floor assemblages is not 

distinct. Here, it is expressed as a much less 

pronounced facies transition between the channeled 

plains (unit AHpc, an expansive unit to the east) and 

the floor. The rim to floor gradient is more gradual 

than the sharp margin in the north; however, the 

-5800m contour still marks a significant 

morphologic change. Some ridge trends trace across 

this gradational boundary, but east of the contact, 

the surface is smooth and displays superposed 

channels (unit AHpc), whereas to the west 

prominent channels are lacking and several small to 

medium-sized craters mark a distinct morphological 

difference. 

 

The scarp-bound plateaus in this region preserve 

trends consistent with wrinkle ridge trends to the 

north and south of the sinuous depressions. There 

are no topographic expressions of any wrinkle 

ridges across the depressions, suggesting that 

topography associated with the wrinkle ridges and 

plateaus was established prior to the excavation of 

the channel-like features. Thus the surfaces of the 

plateaus and the surrounding plains most likely 

represent the same surface (unit HNfis). South of 

this plateau region are several large craters with 

commingled ejecta blankets. Some ejecta blankets 

display radial striations, lobate margins, and dark 

albedo materials. A variety of degradation states are 

evident, consistent with various ages of the impact 

events; however, the exposed surface is dominated 

by armored ejecta blankets with few superposed 

pristine craters suggesting that this surface was 

buried and has since been exhumed in a relatively 

uniform manner. To the east, near the contact 

between units HNfis and AHpc, an anomalous zone 

of semi-exhumed craters exists. This zone represents 

the sub-surface bridge between the rim Nph units 

and floor Nph inselbergs and the thinnest 

preservation of unit HNfis. Several crater rims 

merge with both pronounced and subdued 

topography associated with the regional wrinkle 

ridges, making this region older than the 

deformation, and potentially the oldest area within 

the map area. 

Hellas floor assemblage. Hellas floor materials 

are moderately to heavily cratered, deformed by 

wrinkle ridges, and are locally dissected by the 

farthest extensions of Dao and Harmakhis Valles. 

With the exception of a lobe extending from the 

mouth of Dao Vallis (unit AHvt), there is a general 

lack of distinct depositional margins/contacts in the 

vicinity of channel and canyon mouths that cross the 

rim/floor assemblage boundary. This leaves several 

hypotheses about the origin of the eastern Hellas 

floor materials: 1) they are composed of far reaching 

deposits from Dao and Harmakhis Valles with 

contacts west of the map area, 2) they are not 

comprised of significant materials delivered by Dao 

and Harmakhis Valles, but rather consist of planitiawide deposits, or 3) both the floors of the canyons 

and Hellas received materials from the rim, but have 

undergone significant Amazonian softening (aeolian 

infill, mid-latitude mantling), which has masked any 

original genetic and/or temporal relationships 

between canyon floor and Hellas floor materials. 

Relatively deep sinuous depressions extend from 

the mouth of Harmakhis Vallis and meander around 

several high standing plateaus. These depressions do 

not preserve primary channel features but do 

maintain a characteristic planform shape indicative 

of fluvial processes, supporting hypothesis 3 as 

described above. The subdued topography of these 

depressions and the surrounding plateaus suggests 

burial by meters to 100s of meters of material. The 

deepest portions of these depressions exhibit the 

smoothest materials, perhaps indicating the greatest 

degree of burial (unit AHfs). These farthest 

extensions of Harmakhis Vallis may or may not 

represent ancient surface connections between the 

Harmakhis head valley to the northeast and its 

terminus located within the map area. 

Valles and Channel materials. The larger, more 

mature, canyon segments of Dao and Harmakhis 

Valles also dissect the rim and floor assemblages; 

the lower reaches of Dao Vallis preserve several 

episodes of channel/canyon development showing 

abandoned truncated channels (units Hch1 and 

AHch2). Where the canyons are wide and more fully 

developed, Amazonian/Hesperian valley fill 

superposes their floors (units AHvD and AHvH). 

References. [1] Crown D.A. et al. (1992) Icarus, 100, 

1-25. [2] Mest S.C. and Crown D.A. (2001) Icarus, 153, 

89-110. [3] Leonard G.J. and Tanaka K.L. (2001) USGS 

Geol. Invest. Ser. Map I-2694. [4] Tanaka K.L. and 

Leonard G.J. (1995) JGR, 100, 5407-5432. [5] Greeley R. 

and Guest J.E. (1987) USGS Geol. Invest. Ser. Map I1802B. [6] Mest S.C. and Crown, D.A. (2002) USGS 

Geol. Invest. Ser. Map I-2730. [7] Mest S.C. and Crown, 

D.A. (2003) USGS Geol. Invest. Ser. Map I-2763. [8] 

Price K.H. (1998) USGS Geol. Invest. Ser. Map I-2557. 

[9] Mest S.C. and Crown, D.A. (2006) USGS Sci. Invest. 

Map 2934. [10] Crown D.A. and Greeley R. (2007 in 

press), USGS. [11] Crown D.A. et al. (2005) JGR, 110, 

E12S22.
GEOLOGIC MAP OF MTM 35337, 40337, AND 45337 QUADRANGLES, DEUTERONILUS MENSAE 

REGION OF MARS. Frank C. Chuang and David A. Crown, Planetary Science Institute, 1700 E. Fort Lowell 

Rd., Suite 106, Tucson, AZ 85719 (e-mail: chuang@psi.edu). 

Introduction: Deuteronilus Mensae, a gradational 

zone along the dichotomy boundary in the northern 

mid-latitudes of Mars, includes the transition from the 

rugged cratered highlands of Arabia Terra to the northern lowland plains of Acidalia Planitia. Within Deuteronilus Mensae, polygonal mesas are prominent 

along with features diagnostic of Martian ‘fretted’ terrain, including lobate debris aprons, lineated valley 

fill, and concentric crater fill [1-3]. Lobate debris 

aprons, as well as the valley and crater fill deposits, are 

considered to be geomorphic indicators of ground ice 

[4-8] and their concentration in Deuteronilus Mensae 

is of great interest because of their potential association with Martian climate change. The morphologic 

and topographic characteristics of the Deuteronilus 

Mensae region record a diverse geologic history [9-

10], with significant modification of the ancient highland plateau and resurfacing of low-lying regions. Recent geologic mapping of Deuteronilus Mensae and 

regional studies of lobate debris aprons and other icerich flow features have revealed insights into highland 

plateau degradation, including the significance of surface collapse [11-12]. 

Data and Methods: Digital files in raster and vector format produced by the U.S. Geological Survey 

(USGS), along with some non-USGS data, were used 

in the geological mapping of the Deuteronilus Mensae 

region in conjunction with ArcGISTM Geographic Information Systems (GIS) software. The geology was 

mapped primarily on a Viking MTM base mosaic, supplemented with a THEMIS daytime IR mosaic. The 

contacts and structures were digitized and saved in an 

ArcGIS “geodatabase.” The individual geodatabase 

components were then imported into Adobe Illustrator 

CS using a MAPublisher 7.0 software plug-in. The 

locations of individual craters, along with other information for crater count age dating, were saved as a 

point shapefile in ArcGIS. 

Geologic Map: Deuteronilus Mensae was first 

mapped at 1:5M scale using Mariner 9 data and later at 

1:15M scale with Viking Orbiter data [13-14]. We 

have mapped 3 Mars Transverse Mercator (MTM) 

quadrangles (35337, 40337, and 45337; 32.5-47.5oN, 

20-25oE) that transect the dichotomy boundary in Deuteronilus Mensae (Fig. 1). A total of 17 geologic units 

were identified, which can be grouped into 4 material 

types (from oldest to youngest): Plateau, Plains, Impact Crater, and Surficial materials. Plateau materials 

consist of the continuous ancient highland plateau and 

polygonal mesas and small knobs scattered within the 

plains. Plains materials consist of relatively flat expanses of smooth-to- hummocky deposits in the lowland plains north of the continuous highland margin. 

Impact Crater materials consist of rim, floor, and ejecta 

deposits of impact craters in a variety of preservation 

states, and include the central peak materials of an 

ancient impact structure. Surficial materials consist of 

Smooth-to-Hummocky Fill deposits within the floors 

of impact craters, plateau depressions, and other lowlying regions near Cerulli impact crater, and Lobate 

Debris Apron materials, which cover much of the surface area in the mapping region and surround and extend beyond the bases of impact crater walls, mesas, 

escarpments, and other features that have significant 

relief. For a complete description of the geologic history, see [15]. 

Key Mapping Results: 1) Within the highland 

plateau, three prominent large, elongated, closed depressions 300-500 m deep contain numerous polygonal 

blocks and rounded knobs that have different sizes and 

abundances, indicating progressive stages of highland 

degradation and provides a potential formation mechanism for the polygonal mesas and fretted valleys in the 

region [12]. 2) Analyses of MOLA profiles from the 

dichotomy boundary to the northern extent of polygonal mesas show elevation differences within some far 

boundary mesas. The differences could be due to progressive erosion of the plateau to the north, a lessresistant, upper layer that has been removed, a general 

downsloping of the plateau into the lowlands, or any 

combination of these. 3) Distinct geomorphologic evidence for an ancient ocean or standing bodies of water 

along the dichotomy boundary in the map region was 

not apparent. 

Acknowledgments: This work was supported by 

NASA PG&G Grant NNG04GI85G. 

References: [1] Sharp R.P. (1973) JGR, 78, 4073-4083. [2] 

Carr M.H. (1996) Water on Mars, Oxford Univ. Press, 221 p. [3] 

Carr M.H. (2001) JGR, 106, 23571-23593. [4] Squyres S.W. (1978) 

Icarus, 34, 600-613. [5] Squyres S.W. (1979) JGR, 84, 8087-8096. 

[6] Squyres S.W. (1989) Icarus, 79, 229-288. [7] Lucchitta B.K. 

(1984) JGR, 89, B409-B418. [8] Squyres S.W. and Carr M.H. (1986) 

Science, 231, 249-252. [9] McGill G.E. (2000) JGR, 105, 6945-

6959. [10] McGill G.E. (2002) USGS Geol. Invest. Ser. Map I-2746, 

1:1M scale. [11] Crown D.A. et al. (2006) LPSC 37, abstract #1861. 

[12] Chuang F.C. and Crown D.A. (2007) LPSC 38, abstract #1455. 

[13] Lucchitta B.K. (1978) USGS Misc. Invest. Ser. Map I-1065, 

1:5M scale. [14] Greeley R. and Guest J.E. (1987) USGS Misc. Invest. Ser. Map I-1802B, 1:15M scale. [15] Chuang F.C. and Crown 

D.A. (2007) USGS Sci. Invest. Ser. Map, submitted (available for 

download: http://www.psi.edu/pggroup/mapping.htm). 
Figure 1. Geologic map of MTM Quadrangles 35337, 40337, and 45337, Deuteronilus Mensae region of Mars and 

accompanying chart showing the Correlation of Map Units. See [15] for more details.
Figure 1: Shaded relief overlain by MOLA 128 

pix/deg of Margaritifer Terra. Arrows point to the 

locations of prominent features. The red boxes 

indicate individual MTM quads. Red boxes with 

black numbers are the 7 quads currently being 

mapped and boxes with a hatch pattern and white 

numbers indicate quads under review. 

MAPPING MARGARITIFER TERRA: MTMS -15017, -20002, -20007, -20017, -20022, -25002, -25007. C. M. 

Fortezzo1

, K. K. Williams2, and J. A. Grant3, 1Northern Arizona University, Flagstaff, AZ, 86001. cmf@nau.edu, 2

Earth Sciences Department, Buffalo State College, Buffalo, NY 14222. williakk@buffalostate.edu, 3Center for 

Earth and Planetary Studies, National Air and Space Museum, Washington, DC, 20013-7012. 

Introduction: As part of a continuing campaign to 

better understand the relationship between valleys 

and resurfacing events through mapping, we are 

mapping seven 1:500,000-scale MTM quads in the 

Margaritifer Terra region. Results from this mapping 

will also help constrain the role and extent of past 

water in Margaritifer Terra. The MTMs are grouped 

in two different areas (Figure 1, red boxes with black 

text) within the region and compliment the completed 

mapping in four quads (Figure 1, red boxes with 

hatch pattern) that are currently in the review process 

[1-5]. 

Three western quads focus on Jones crater and the 

Himera, Samara and Loire Valles systems (central 

portion of Figure 1). The four eastern quads focus on 

the headward regions of Paraná Valles and the 

valleys on the western flank of Newcomb crater 

(southeastern area of Figure 1). 

Datasets: For these maps, we used MDIM 2.1 

and MOLA 128 pix/deg datasets as the initial 

mapping base and have processed THEMIS daytime 

and nighttime infrared images. We rubbersheet the 

daytime IR images using MDIM 2.1 as the control 

and are using them as a mapping base with ~95% 

coverage. THEMIS daytime and nighttime infrared 

band 9 images were processed using the ISIS-based 

THEMIS processing tools (them-proc.mars.asu.edu) 

and overlain in ArcMap. THEMIS daytime IR threeband RGB (8-7-5, 9-6-4, and 6-4-2) decorrelation 

stretch images are being used for mineralogy 

information [6]. Regional-scale map bases are 

supplemented with processed and georeferenced 

THEMIS visible and MOC narrow angle images 

where available. Several HiRISE images provide 

detailed textural information where available. 

Methods: We have imported and registered all 

pertinent raster and vector data using ESRI’s ArcMap 

GIS software. Using this digital environment, we 

have begun digitizing lines (e.g., contacts, structures, 

etc.) and polygons (e.g., units and craters). Arc 

extensions provide robust tools for (1) analyzing 

spatial relationships across multiple data layers, (2) 

attributing and updating digital linework, (3) building 

and analyzing vector topologies, and (4) importing 

new data as they are released. To inspect and 

quantify stratigraphic relations, we are compiling 

crater counts in ESRI’s ArcView GIS software to 

make use of crater counting tools [7] specifically 

developed for planetary mappers [8]. 

Current Work: Work on the seven quads began 

by concentrating on the Newcomb-Paraná area 

(MTMs -20002, -20007, -25002, and -25007; Figure 

2) in order to determine the relative ages of 

resurfacing events in upper Paraná Valles and to 

examine how valleys either incise or are mantled by 

resurfacing deposits within the Newcomb-Paraná 

region. 

In this mapping area, as was demonstrated in the 

adjacent two western quadrangles (MTM -20012 and 

-25012) [1-5], Noachian cratered plains dissected by 

fluvial erosion are resurfaced by two separate events. 

In addition to dissection of the ancient highland 

terrain unit, troughs and valleys are also found in the 

first resurfacing unit. The second resurfacing episode 

infills craters, embays valleys and troughs, and 

appears smooth in THEMIS IR images. 

The valleys, valley networks and troughs in the 

area dissect the ancient Noachian highland terrain, 

the first resurfacing event, and craters in the mapping 

area. Centers of deposition along the paths of these 

valleys are usually impact basin interiors or small, 

flat areas adjacent to the outer flanks of the mapcentered large impact basin. This ~350 km diameter 

ancient impact has multiple inlets flowing into its 

eastern and southern flanks. The interior of the basin 

is basically horizontal (slope <0.01); the outlet is only 

~200 meters lower than the main input. On the basin 

floor are several areas of positive relief chaotic 

terrain similar to that of a basin west of Paraná Valles 

[1-5]. There is also a paucity of 
Figure 3: THEMIS 

daytime infrared image 

mosaic of the Jones 

crater area. Gaps in the 

dataset are areas where 

there is currently no 

THEMIS daytime 

coverage. 

geomorphic evidence of fluvial erosion in this basin. 

These observations lead to the hypothesis that this 

was an extensive area of fluid ponding and (possibly) 

infiltration into the Martian regolith. 

The western edge of Newcomb crater is 

characterized by a plateau area flanked by dense 

fluvial dissection. The plateau area does not appear to 

be a large enough contributing area to feed the valley 

networks with overland flow, and the valley networks 

are consistent with the geometry described for 

terrestrial sapping valleys [9]. The radial pattern of 

valleys in this area may relate to the groundwater 

flow through the system of fractures created by the 

impact that formed Newcomb crater with some 

contribution from overland flow. 

The western 3 quads (MTMs -15017, -20022, and 

-20017; Figure 3) cover Himera and Samara Valles to 

the west, Jones crater, and Loire Valles to the east 

(Figures 1 and 3). Current work in this area involves 

counting craters and demarcating initial units. This 

work now involves three undergraduate students. 

Future Work: For both areas, geologic linework 

advances as the science tasks are continued. 

In the Newcomb-Paraná area, crater counting 

techniques designed for calculating the ages of 

narrow, linear features [10, 11] will be used to 

establish comparative ages of the valley networks 

relative to each other. This analysis will be performed 

on the Paraná Valles network and on the network on 

the western flank of Newcomb crater, and the results 

of each area will be compared to determine their ages 

relative to each other. We will compute the 

cumulative crater densities for sub-basins within the 

valley networks and compare them against each other 

to further constrain the role and persistence of water 

in the region. 

In the Jones crater area, review of Viking Orbiter 

images led to the hypothesis that the drainage history 

of the Jones-Loire area may have been affected by 

emplacement of Jones crater [12]. These images 

showed that ejecta from Jones crater partially buried 

parts of Samara and Loire Valles and totally obscured 

portions of Samara Valles [12]. We will test the 

hypothesis that a second order pathway once 

connected Samara Valles with Loire Valles east of 

the third ring of the Ladon basin using higher 

resolution MOC and THEMIS images, MOLA 

topography and the 1:500,000 map. 

References. [1] Grant J.A. and D.A. Clark (2002) 

Planetary Mappers Meeting (abst.). [2] Williams, 

K.K. and J.A. Grant (2003) Planetary Mappers 

Meeting (abst.). [3] Fortezzo, C.M. and J.A. Grant 

(2004) Planetary Mappers Meeting (abst.). [4] Grant, 

J.A., K.K. Williams, and C.M. Fortezzo (2005) 

Planetary Mappers Meeting (abst.). [5] Wilson, S. et. 

al. (this volume) Planetary Mappers Meeting (abst). 

[6] Rogers, D. et. al., (2003) J. Geophys. Res., 108. 

[7] Hare, T. et al. (2006) LPSC XXXVII, 2398 (abst.).

[8] Barlow, N. (2006) LPSC XXXVII, 1337 (abst.). 

[9] Laity, J.E. and M.C. Malin, (1985), Geo. Soc. Am. 

Bull, 96, 203-217. [10] Tanaka, K.L. (1982) NASA 

Tech. Memo., 85127, 123-125. [11] Wichman, R. and 

P.H. Schultz (1987) NASA Tech. Memo., 89810, 474-

475. [12] Grant, J.A. (1987) NASA Tech. Memo., 

89871, 1-268. 

Figure 2: MOLA topography overlain on THEMIS 

daytime IR strips for the southeast portion of 

Margaritifer Terra. Blue arrows indicate flow 

direction of numerous valley networks in the area. NC 

= Newcomb crater; CB = crater basin; PC = Peta 

crater; and PV = Paraná Valles. 
MAPPING HESPERIA PLANUM, MARS. Tracy K.P. Gregg1

 and David A. Crown2, 1Department of Geology, 

876 Natural Sciences Complex, University at Buffalo, Buffalo, NY 14260, tgregg@geology.buffalo.edu; 2

Planetary 

Science Institute, 1700 E. Ft. Lowell Rd., Suite 106, Tucson, AZ 85719, crown@psi.edu. 

Introduction: Hesperia Planum, characterized by 

a high concentration of mare-type wrinkle ridges and 

ridge rings [1-4], encompasses > 2 million km2

 in the 

southern highlands of Mars (Fig. 1). The most 

common interpretation is that the plains were 

emplaced as “flood” lavas with total thicknesses of 

<3 km [4-10]. The wrinkle ridges on its surface make 

Hesperia Planum the type locale for “Hesperian-aged 

ridged plains” on Mars [e.g., 9], and recent 

investigations reveal that wrinkle-ridge formation 

occurred in more than one episode [4]. Hesperia 

Planum’s stratigraphic position and crater-retention 

age [e.g., 9, –11, 12] define the base of the Hesperian 

System. However, preliminary results of geologic 

mapping reveal that the whole of Hesperia Planum is 

unlikely to be composed of the same materials, 

emplaced at the same geologic time. To unravel these 

complexities, we are generating a 1:1.5M-scale 

geologic map of Hesperia Planum and its 

surroundings (Fig. 1). To date, we have identified 4 

distinct plains units within Hesperia Planum and are 

attempting to determine the nature and relative ages 

of these materials (Fig. 2) [13-15]. 

Hesperia Planum Plains Materials: Using 

images from the Thermal Emission Imaging System 

(THEMIS) [16], we have been able to broadly divide 

the “Hesperian ridged plains materials” identified 

using Viking Oribiter images [9] into 6 distinct 

geologic units. MOLA data reveal that the east and 

west boundaries of the continuous topographic basin 

that defines Hesperia Planum [cf. 9] closely follow 

the 2-km elevation contour, and most of what has 

been geologically defined as Hesperia Planum [cf. 1, 

7, 9] is contained within that contour line. In contrast, 

highland plains occur in isolated outcrops surrounded 

by highlands material (Fig. 3). Units with the 

descriptor “highlands” are found at elevations above 

2 km [16]. 

Geologic units within Hesperia Planum can be 

broadly classified as those associated with Tyrrhena 

Patera, and those that are not (Fig. 2). Crown and 

others [15] discuss the characteristics and relative 

ages of the Tyrrhena Patera materials [see also 17-

21]. The plains materials to the south and southeast 

of Tyrrhena Patera are heavily affected by fluvial, 

ice, and possibly lacustrine processes [17, 22, 23], 

making interpretations of the original nature of the 

materials difficult. “Modified plains materials” 

contain mare-type wrinkle ridges, but the ridges are 

not morphologically crisp; they appear to have been 

modified by erosional processes, locally revealing 

layers within the plains. “Dissected plains materials” 

also contain mare-type wrinkle ridges and have 

locally been dissected by channels. Within dissected 

plains materials, small channels surrounded by lobate 

deposits are observed. Available images do not yet 

allow an unequivocal interpretation for these channel 

features: they may be lava flows, fluvial features, or 

debris flows. 

The region of Hesperia Planum located to the 

east of Tyrrhena Patera (Fig. 2) is the typical 

“Hesperian ridged plains” [7, 9]. Aside from 

Tyrrhena Patera, no obvious volcanic vents have 

been found within Hesperia Planum [cf. 4, 13, 18, 20-

22]. Lava flows can be seen at available image 

resolutions in the Tyrrhena Patera lava flow field [18] 

that post-dates the ridged plains, but they are not 

readily apparent within the ridged plains. Within 

these “ridged plains materials,” we have thus far 

identified four distinct plains units [14], suggesting 

that a range of depositional and/or erosional 

processes have operated across Hesperia Planum 

through time [cf. 22]. 

Mapping Progress: Units have been identified 

and are being mapped across the region. Preliminary 

crater size-frequency distributions have been 

calculated using Barlow’s crater database for craters 

≥5 km in diameter 

References: [1] Scott, D.A. and M. Carr (1978) 

USGS Misc. Series I-1083. [2] Chicarro, A.F., P.H. 

Schultz and P. Masson (1985) Icarus 63:153. [3] 

Watters, T. and D.J. Chadwick (1989), NASA Tech. 

Rpt. 89-06:68. [4] Goudy, C., R.A. Schultz and 

T.K.P. Gregg, J. Geophys. Res. 110: E10005 

10.1029/2004JE002293. [5] Potter, D.B. (1976) 

USGS Misc. Series I-941. [6] King, E.A. (1978) 

USGS Misc. Series I-910. [7] Greeley, R. and P. 

Spudis (1981) Rev. Geophys. 19:13. [8] Scott, D.A. 

and K. Tanaka (1986) USGS Misc. Series I-1802A. 

[9] Greeley, R. and J. Guest (1987) USGS Misc. 

Series I-1802B. [10] Leonard, J.G. and K. Tanaka 

(2001) USGS Misc. Map Series I-2694. [11] Tanaka, 

K.L., 1986, Proc. LPSC 17th, JGR Suppl. 91, E139-

E158. [12] Tanaka, K. (1992), in Mars, U. Arizona 

Press, p. 345. [13] Gregg, T.K.P. and D.A. Crown, 

2007, Lun. Planet. Sci. Conf. 38th, Abstract #1190. 

[14] Crown, D.A., D.C. Berman and T.K.P. Gregg, 

2007, Lun. Planet. Sci. Conf. 38th, Abstract #1169. 

[15] Jones, T.K., T.K.P. Gregg and D.A. Crown, 

2007, Lun. Planet. Sci. Conf. 38th, Abstract #2156. 
[16] Christensen, P.R. and others, 2004, Space Sci. 

Rev. 110:85-130. [17] Mest, S. and Crown, D.A. 

(2001) Icarus 153:89. [18] Greeley, R. and D.A. 

Crown (1990) J. Geophys. Res. 95:7133. [19] Gregg, 

T.K.P., D.A. Crown and R. Greeley (1998) USGS 

Misc. Series I-2556. [20] Gregg, T.K.P. and M.A. 

Farley (2006) J. Volcanol. Geotherm. Res. 151:81-91. 

[21] Farley, M.A., T.K.P. Gregg and D.A. Crown 

(2004) USGS Open File Rpt. 2004-1100. [22] 

Ivanov, M.A. et al., 2005, JGR 110, E12S21. [23] 

Crown, D.A., L.F. Bleamaster III and S.C. Mest, 

2005, J. Geophys. Res. 110, E12S22, 

doi:10.1029/2005JE002496. 

Figure 1. Gridded MOLA data (128 

pixels/degree) of the area being mapped at 1:1.5 

million scale. Reds are topographic highs 

(Tyrrhena Patera summit is ~3 km above mean 

planetary radius) and blues are lows. 

Figure 2. Rough boundaries of identified plains 

materials within Hesperia Planum. Portions of 

these materials were originally mapped as 

“Hesperian-aged ridged plains” at 1:15 million 

[9]. 

Figure 3. Hesperia Planum with 1-km-interval 

contour lines. The boundary of Hesperia 

Planum [9] roughly corresponds with the 2-km 

elevation line [22]. 
HYDROLOGIC AND VOLCANIC EVOLUTION OF ATHABASCA VALLES, MARS: THE FIRST STEP 

TO GEOLOGIC MAPPING AT 1:500,000 SCALE. L. Keszthelyi1

, W. Jaeger1, K. Tanaka1, 1U.S. Geological 

Survey, Astrogeology Team, 2255 N. Gemini Dr., Flagstaff, AZ 86001. 

Introduction: The “Follow-the-Water” Mars exploration strategy espoused by NASA places a great 

deal of emphasis on the most recent examples of largescale aqueous flow on Mars. The Cerberus region, 

which includes Athabasca Valles, has long been recognized as one of the geologically youngest areas on 

the planet with large-scale fluvial and volcanic activity 

[e.g., 1-10]. The fact that Athabasca Valles was seriously considered as a landing site for the MER mission 

and the Beagle 2 lander is one indication of the level 

of interest in this location [11,12]. 

Understanding the recent activity at Athabasca has 

implications for adjacent regions and times. For example, the lava and water from the Cerberus Fossae 

extended through Marte Vallis into western and perhaps northern Amazonis Planitia [e.g., 5, 8, 10, 13, 

14]. Thus, the recent resurfacing processes in Athabasca may have also operated across much of the 

northern plains in the more distant past [e.g., 15]. 

Work Plan: This project has been divided into 

five tasks to be completed over three years. We are 

near the end of the 1st year. The tasks are (1) combine 

the relevant Mars data sets into a single georegistered 

GIS project, (2) choose the geologic units to be 

mapped, (3) determine the spatial and temporal nature 

of the contacts between these units at key locations, (4) 

extrapolate the contacts across the entire region, and 

(5) publish a peer-reviewed journal article and a set of 

4 USGS MTM quadrangle maps. 

Task 1: A GIS project containing the following 

datasets has been assembled: Viking MDIM, MOLA, 

all available MOC images, and all available THEMIS 

VIS images. THEMIS IR data were initially processed 

for inclusion but we are now moving to simply use the 

mosaics provided by the THEMIS team. While 

slightly lower in spatial resolution, the mosaic is much 

easier to work with than the individual images. A 

slight delay has been introduced by the processing 

upgrade from ISIS2 to ISIS3. The tools to update the 

pointing (and thus locations) of the MOC and 

THEMIS data are just now coming on line. The other 

more significant delay is that we are awaiting the June 

8th release of MRO CTX data which we have good 

reason to expect to be extremely valuable for mapping 

this region. CTX data ingestion is expected to be 

straightforward because all the necessary tools are 

available (and tested) in ISIS3. 

Task 2: Partly based on new MRO data, but relying largely on work for this project, we have determined what geologic unit to classify the floor of Athabasca Valles. It is a lava flow [16-19]. We have also 

determined the other major units (the equivalents of 

units HBu2, HNn, AHEe, AEc2 and AEc3 from [20]). 

The ejecta from Persbo crater will also be mapped 

separately. While further refinement will be inevitable 

as the actual linework of the map starts (we expect to 

be able to subdivide AEc3), Task 2 is largely complete. 

Task 3: In completing Task 2, the detailed localized studies have been completed. This has been accomplished using both new MRO data and older MGS 

and MO data. As noted above, the key finding is that 

Athabasca Valles is draped by a recent lava flow. No 

exposures of fluvial sediments have been identified. 

Task 4: The actual drawing of lines on the 

basemaps will begin later this summer and continue 

through the next fiscal year. 

Task 5: The last year of this project will be dedicated to publication of the maps and journal articles. 

Preliminary Results: The basic geologic history 

that we have found is as follows: (1) Long lobate lava 

flows from the Elysium volcanic rise covered the region, (2a) wrinkle ridges formed, (2b) the Persebo 

impact, (3a) Athabasca Valles was cut by fluids (water 

or lava) from the Cerberus Fossae, (3b) minor extensional fracturing of the floor of Athabasca Valles, (4) 

Athabasca Valles is filled by a large fluid flood lava 

flow, (5) the lava flow drains out leaving a thin draping, (6) a light toned mantle is deposited, (7) the Zunil 

impact and the formation of a field of secondary craters, (8) wind erosion of the light-toned mantle except 

where protected by crater ejecta and local topography. 

Very little time may have passed between (3) – (6). 

References: [1] Tanaka, KL (1986) JGR, 91, E139-

158. [2] Greeley, R and JE Guest (1987) USGS Misc. Inv. 

Map I-1802-B. [3] Plescia, JB (1990) Icarus, 88: 465-490. 

[4] Plescia, JB (1993) Icarus, 104: 20-32. [5] Plescia, JB 

(2003) Icarus, 164, 79-95. [6] Berman DC and WK Hartmann (2002) Icarus, 159: 1-17. [7] Burr, DM et al. (2002a) 

GRL, 29: 2001GL013345. [8] Burr, DM et al. (2002b) Icarus

159, 53-73. [9] Rice, J.W. et al. (2002) LPSC 33 Abstract 

#2026. 10] Tanaka, KL et al. (2003) JGR, 108: 

2002JE001908. [11] Golombek, MP et al. (2003) JGR 108, 

CiteID 8072. [12] Bridges, JC et al. (2003) JGR, 108, 

2001JE00182003. [13] Fuller, ER, and JW Head (2002) JGR

107, CiteID 5081. [14] Keszthelyi, L et al. (2004) Geochem. 

Geophys. Geosys., 5, 2004GC000758. [15] Tanaka, KL et al. 

(1992) U.S. Geol. Surv. Misc. Invest. Ser., Map I-2147. [16] 

Jaeger, WL et al. (2007) LPSC 38, Abstract #1995. [17] 

Jaeger, WL et al. (2007) LPSC 38, Abstract #2066. [18] 

Jaeger WL et al. (2007) Mars7, Abstract #3394. [19] Jaeger 

WL et al. (in revision) Science. [20] Tanaka, KL et al. (2005) 

U.S. Geol. Surv. Sci. Inv. Map 2888. 
Figure 1. Mosaic of MRO CTX images in the mapping area over the Viking MDIM 2.1 basemap. All processing was completed in ISIS3 but the CTX images have not yet been controlled. There is already almost complete 

CTX coverage of the Athabasca Valles channel system (which runs diagonally NE-SW across the mosaic). Much 

of the Cerberus Fossae fissures (in the NE) and the Cerberus Palus basin (in the SW) are also imaged. The link between Cerberus Palus and the eastern part of Elysium Planitia (called Lethe Vallis) is covered by the southernmost 

CTX image. The contacts between each of the main geologic units have been at least sampled by CTX. 
Geologic Mapping of the Martian Impact Crater Tooting. Pete Mouginis-Mark, 

HIGP/SOEST, Univ. Hawaii, Honolulu, HI 96822. <pmm@higp.hawaii.edu> 

Introduction: Tooting crater is ~29 km in diameter, is located at 23.4°N, 207.5°E, and is 

classified as a multi-layered ejecta crater [1]. Tooting crater formed on virtually flat lava 

flows within Amazonis Planitia where there appears to have been no major topographic 

features prior to the impact, so that we can measure ejecta thickness and cavity volume 

[2]. To date, we have: (1) Produced a 30-image THEMIS VIS mosaic of Tooting crater 

with extensive help from Ryan Luk at Arizona State University. (2) Finished a first draft 

of the geologic map of Tooting Crater (Figure 1). (3) In collaboration with Alfred 

McEwen and Livio Tornebene of the HiRISE Team, we have obtained five 25-cm 

resolution HiRISE images of Tooting crater that dramatically show some of the errors of 

our previous studies, and show the importance of dewatering of the ejecta blanket [3]. 

Science Questions: We are trying to resolve several science issues that have been 

identified during this mapping, including: 

1) What is the relative importance of dewatering of the ejecta (both within the crater 

cavity and within the ejecta blanket)? HiRISE images indicate that dewatering has been 

responsible for the formation of several flows on the crater rim and inner walls, and 

desiccation of the wet ejecta may also be responsible for the formation of extensive pitted 

material on the crater floor. 

2) Do the ejecta layers lie on top of each other, so that the layers closest to the primary 

are the youngest? Or are the outermost ejecta layers on top of layers more proximal to 

the parent crater? Resolving this stratigraphic relationship has fundamental implications 

for understanding the process that creates the ejecta blanket of multi-layered impact 

craters on Mars. 

3) We want to distinguish the distal ramparts of the ejecta layers as separate 

morphologic units, as they may offer unique insights into the formation of the ejecta 

layers as deceleration features [4]. However, they are probably made of the same 

material as the rest of the ejecta layers. Their identification as a separate unit could help 

with the interpretation of the ejecta flow processes [4 – 6]. 

Plans for Year 2:

a) Complete a draft geologic map of Tooting crater (i.e., refine Figure 1), and submit 

this map to the U.S. Geological Survey for preliminary review. 

c) Publish a research paper (either in JGR-Planets or Meteoritics and Planetary 

Science) on the HiRISE contributions to our understanding of impact melt at 

Tooting crater. 

d) Start the accompanying map text. 

e) Map the distribution of secondary craters from Tooting crater. This will form a 

second map, to be included with the 1:200K geologic map, and will be produced at 

a scale of 1:1M. 
Figure 1: First draft of the Tooting crater geologic map. Individual secondary craters are 

shown as black dots surrounding the crater. Blue boxes mark the locations of HiRISE 

images studied in detail. 

References: [1] Barlow N. G. et al. (2000). Standardizing the nomenclature of Martian impact crater 

ejecta morphologies. Journal of Geophysical Research 105: 26,733 - 26,738. [2] Mouginis-Mark, P.J. and 

H. Garbeil (2007). Crater geometry and ejecta thickness of the Martian impact crater Tooting. In press: 

Meteoritics and Planetary Science. [3] Mouginis-Mark, P.J., L.L. Tornabene, J.M. Boyce, and A.S. 

McEwen (2007). Impact melt and water release at Tooting crater, Mars. 7th Int. Conf. On Mars. Abs 

#3039. [4] Mouginis-Mark P.J. and Baloga S.M. (2006). Morphology and geometry of the distal ramparts 

of Martian impact craters. Meteoritics and Planetary Science 41: 1469 – 1482. [5] Baloga, S.M., S.A. 

Fagents, and P.J. Mouginis-Mark (2005). Formation of rampart ejecta deposits around Mars impact 

craters. Journal of Geophysical Research 110, E10001, doi: 10.1029/2004JE002338. [6] Barnouin-Jha O. 

S., Baloga S., and Glaze L. (2005). Comparing landslides to fluidized crater ejecta on Mars. Journal of 

Geophysical Research 110, E04010, doi: 10.1029/2003JE002214.
Geologic Mapping of the Olympus Mons Caldera. Pete Mouginis-Mark, 

HIGP/SOEST, Univ. Hawaii, Honolulu, HI 96822. <pmm@higp.hawaii.edu> 

The second year of this mapping has focused on trying to understand the mode of 

formation of the different units within the Olympus Mons caldera. In collaboration with 

Ryan Luk at Arizona State University, we have produced a new THEMIS VIS mosaic of 

the summit caldera that will be used for all the formal mapping. This new mosaic (Fig. 

1) is a great improvement over the earlier images that we were using because it contains 

many of the THEMIS VIS images that were obtained in Years 4 and 5 of the mission 

(i.e., since the start of this mapping), and we have used it for our preliminary mapping. 

Figure 1: (Left): Latest version of the THEMIS VIS base image of the Olympus Mons caldera, produced 

in collaboration with Ryan Luk at Arizona State University. (Right) Major units and depressions within 

the area to be mapped. Rim units are difficult to precisely identify due to varying illumination conditions, 

but are currently sub-divided into undifferentiated lava flows (light tan) and individual lobate flows (darker 

peach color). Note that the central crater (in bright green) probably comprises several discrete collapse 

features. In order to better identify the resurfacing of this unit, initial attention has focused on mapping the 

collapse and compressional features in this part of the caldera. Rectangle illustrates location of Fig. 2. 

As can be seen from Figure 1, there is a large segment of the western caldera floor 

that comprises (probably) three or four separate collapse events that have now been 

almost totally buried under more recent lava flows. A science goal of this mapping is to 

determine more of the details of this burial process, because it would help to constrain the 

volume of each eruption within the caldera. This segment of the caldera floor is unusual 

because it contains a large number of collapse pits and numerous compressional features 

(Fig. 2). The final map will include the distribution of these features on all segments of 

the caldera floor because it is believed that they are indicators of the post-fill 

modification of the caldera floor. The collapse pits seem to be preferentially located 

within a few kilometers of the boundary with the oldest segment of the caldera (i.e., the 
largest crater that occupies most of the eastern side of the caldera). The compressional 

features are more enigmatic. In particular, there appears to be several generations of 

ridges on the caldera floor. Some of these ridges form broad swells that have then had 

narrow (<200 m wide) ridges superimposed upon them. There are also several broad, 

generally flat and horizontal, segments of the floor that lack any ridges. Even at MOC 

resolution (<4 m/pixel), there are no clear signs of lava flow fronts of volcanic vents in 

this part of the caldera floor (Fig. 2c), so that the exact mode of origin for the caldera 

floor has yet to be identified. 

Figure 2: Distribution of collapse features (white outlines in image at left) and compressional features 

(center), mapped from the new THEMIS VIS mosaic (see Figure 1 for location). Notice that almost all of 

the collapse features are located on the eastern side of the complex, where the basal unit (the earlier part of 

the floor) is probably closest to the surface. The wall material of the different collapse features is shown in 

mid-tones. MOC image (Figure 2c at right) is denoted by the black rectangle in left image. 

Outstanding Issue: At the summer 2006 Mappers’ Meeting, we discussed whether the 

features that comprise the caldera should be called “pit craters.” This formal naming is 

needed because there are several specific differences that will be referred to on the map, 

and there is the need to compare the different collapse features. However, the IAU 

prefers a more generic name, such as “patera.” This does not seem to be acceptable to 

this PI, as the collapse features are clearly part of the entire caldera. In the terrestrial 

community, these features would be called “craters,” except that this standard terrestrial 

nomenclature only applies to features that are less than 1 km in diameter. Larger features 

on Earth would be called “calderas,” but this does not seem to be appropriate for 

Olympus Mons, where we would have to have “calderas within a caldera.” This PI 

prefers to have formal names, with each feature being called a “crater.” 

 

Publication derived from this mapping: 

Mouginis-Mark, P.J., A.J.L. Harris and S.K. Rowland (2007). Terrestrial analogs to the calderas of the 

Tharsis volcanoes on Mars. In: The Geology of Mars: Evidence from Earth-based Analogs, ed. Mary 

Chapman. Cambridge University Press, pp. 71 - 94. 
FINAL MAP RESULTS OF THE OLYMPIA CAVI REGION OF MARS (MTM 85200): GEOLOGIC 

UNITS AND HISTORY. J. A. Skinner, Jr. and K. Herkenhoff, Astrogeology Team, U.S. Geological Survey, 2255 

N. Gemini Drive, Flagstaff, AZ 86001 (jskinner@usgs.gov).

 Introduction. Our recently-completed, 1:500K-scale 

geologic map of MTM 85200--the Olympia Cavi region-

-provides details of geologically-recent Martian processes. The quadrangle includes dunes of Olympia Undae, the deep depressions of Olympia Cavi and the narrow troughs of Boreales Scopuli. A >1000 m high scarp 

located at ~85° N (termed herein the “boreal scarp”) 

elevates higher-latitude troughs above the lower-latitude 

depressions and dune fields. In this paper, we present the 

regional geologic history of materials in MTM 85200 

and environs using excerpts from the completed map. 

Surface Morphologies. A variety of kilometer-, meter- and sub-meter-scale surface landforms and texture 

are apparent in MOLA, MOC narrow and wide angle, 

THEMIS VIS, HRSC, and HiRISE data sets. Within 

MTM 85200, these include (1) asymmetric, troughparallel surface troughs and swales, (2) linear hummocks 

located south of the boreal scarp, (3) multiple, overlapping, eolian dune-forms, (4) darks streaks and mantles of 

variable albedo, and (5) small-scale impact craters. 

Based on cross-cutting relationships, these features span 

the entire exposed sequence of layered rocks within the 

north polar plateau (Fig. 1). Along with unit descriptions, their occurrence and range of formational mechanisms assist in unraveling the geologic history of 

Planum Boreum. 

 Unit Descriptions. Linework was digitized at 

1:75,000 using MOLA 115 m/px DEM, the most continuous, highest-resolution, geo-registered base map. We 

used a late summer 1976 mosaic of Viking Orbiter 1 and 

2 images as a temporal “control” to show the extent of 

the residual ice cap [2]. Geologic units of MTM 85200 

are located in the Borealis province [1]. We apply Amazonian epochs to units based on the stratigraphic work of 

other workers [3-7]. Units are described below from 

youngest to oldest. 

 Planum Boreum 2b unit (ABb2b) – Very high-albedo 

material that forms the uppermost surface of Planum 

Boreum. Dominates polar flats and extends into spiral 

troughs, mostly south of the boreal scarp. Drapes all 

other polar units. Forms rugged patches at lower latitudes and elevations and on trough margins. No impact 

craters observed. Interpretation: Extent of the 1976 residual water-ice cap [2]. Unit thickness ranges from several-meters-thick down to thin coatings interfingered 

with adjacent units (Fig. 1). Subjacent units are only 

locally exposed. Buried contacts are inferred.

 Olympia Undae 2 unit (ABou2) – Low-albedo, closelyspaced, crescent and transverse dune-forms in both 

Olympia Planum and Cavi. Where frosted, unit detected 

by high-albedo hummocks and mottles. Unit overlies 

Olympia Undae 1 unit, Planum Boreum 1 unit, and 

Olympia Cavi 1 unit. Inferred time transgressive contact 

with both Planum Boreum 2a and 2b units (Fig.1). Interpretation: Wind-blown sand and silt of basaltic composition (including weathering products). Accumulated 

primarily through erosion of the Olympia Cavi 1 unit, 

with secondary contributions from other plateau units.

Figure 1. Schematic correlation of map units and associated major 

geologic events that affected the materials of MTM 85200.

Olympia Cavi 2 unit (ABoc2) – Forms the flat floors of 

Olympia Cavi located south of the boreal scarp. Medium- to low-albedo. Smooth at MOLA scale. Decameter-scale features include hummocks, pits, and undulations. Overlain by the Olympia Undae 2 unit near the 

base of northward-facing trough walls. Interpretation: 

Residuum formed through the sublimation of ice-rich 

mantles, lag deposits, or mass-wasting slough from 

higher-standing layered units. 

 Planum Boreum 2a unit (ABb2a) – Forms on trough 

floors and on the shallowly-sloping, north-facing trough 

walls and polar flats. Moderately-smooth at MOLA 

scale. High-albedo with local low-albedo patches and 

mottles. Lower boundary commonly diffuse and is 

drawn using a downward transition to smooth-surfaced, 

evenly-layered material. Thickest at steeply-sloped, 

southward-facing trough walls. Some very low-angle 

unconformities are observed. Interpretation: Dust and ice 

layers of laterally-variable thickness. Texture and appar-
ent layer subparallelism formed either by deposition of 

ice-rich lithic layers or erosion of the unit’s layers. Actively accumulating on decadal time scales. Timetransgressive contact with residual ice (unit ABb2b) and 

polar dunes. 

Planum Boreum 1 unit (ABb1) – Outcrops occur on 

southward-facing trough walls. Unit forms the bulk of 

the polar plateau and has maximum single exposures of 

~800 m; total unit thickness is >1800 m. Has characteristic parallel, even layers of alternating high- and lowalbedo. Layers meter-scale and form ~100-meter-thick 

packages. Unconformities are common, mostly south of 

the boreal scarp. Lower boundary defined by transition 

to low-albedo, slab-like material. Interpretation: Dust 

and ice layers of laterally-continuous thickness. Layering reflects varying dust-ice ratios. Deposited from atmospheric fall-out and/or surface saltation. Rhythmic 

nature relict of climatic alternations caused by orbital 

cyclicity, regional volcanic activity, and/or large-scale 

planetary impact. Forms the bulk of the polar plateau. 

Olympia Cavi 1 unit (ABoc1

) – Occurs on southwardfacing trough and depression walls of Olympia Cavi. 

High- and low-albedo, slab-like, cross-bedded, cliffforming, thickly-bedded layers. Very low-albedo layers 

grade into sand sheets and dunes. Maximum apparent 

thickness in any single exposure is ~400 m. Interpretation: Layers of dust and sand, perhaps indurated with 

varying amounts of ice, salt, or other cementing agents. 

Outcrop morphology may be evidence of low-grade 

diagenesis, perhaps via compaction and/or chemical induration/alteration. Cliff-forming layers may have a 

higher proportion of ice or another cementing agent. 

Olympia Undae 1 unit (ABou1

) – Occurs in northern 

Olympia Planum. Contains irregularly-shaped, low amplitude swales, commonly abutted by dunes on their 

windward edges. Small, discontinuous patches of 

closely-spaced ripples and meter-scale, crescent-shaped 

ridges common. Overlain by the Planum Boreum 2a and 

2b units and Olympia Undae 2 unit. Interpretation: Moderately-resistant, eolian-scoured substrate. Localized 

sand ripples are inactive. Crescent-shaped ridges are the 

preserved bases of dunes, indurated perhaps by saltcementation. 

 Geologic History. We reconstruct the geologic evolution of the units in MTM 85200 using morphologic, geologic, and stratigraphic observations (Fig. 1) as well as 

past investigative results of other authors. Crater paucity 

impedes accurate relative age dating and an understanding of when Planum Boreum began to form [e.g., 4-6]. 

Superposition of these materials on Vastitas Borealis 

(VB) units clearly shows that the earliest possible start 

was during the Early Amazonian [1, 3]. Based on past 

work, we suggest the unit ABoc1 began to accumulate 

during the Middle Amazonian [1, 3-7], after a prolonged 

episode of lowland surface degradation [8] (Fig. 1), evidenced by lowland pedestal–type craterforms [e.g., 1, 9]. 

Unit ABoc1 was deposited as massive, overlapping, 

cross-bedded dunes whose thickness appears to be >400 

m based on the minimum apparent thickness of outcrops. Dunes may have contained minor ice and finegrained lithic components. The unit rooted the Middle 

Amazonian polar plateau into buried, volatile-rich rocks 

of the VB units, though it is unclear how unit ABoc1 

rocks may interfinger with subjacent lowland plains materials. Unit ABoc1 may have sourced from eroded Scandia materials, Chryse outflow sediments, or other regional units [1, 7]. 

 During the Middle (or Late?) Amazonian, unit ABoc1

dune rocks were eroded into irregularly-shaped hillocks 

<400 m high, based on a capping unconformity. Eroded 

detritus may have been dispersed across the adjacent 

lowland plains as dune fields, some of which may be 

exposed today (as unit ABou2). This erosional event was 

followed by deposition of the units ABou1 and ABb1, 

locally interrupted by erosional or depositional hiatus 

(forming unconformities). We suggest the unit ABou1

unit is stratigraphically equivalent to lower portions of 

unit ABb1, perhaps representing a planated and partlyburied sequence of layered rock. Unit ABb1 may have 

started accumulating during the most recent major decrease in solar insolation (estimated at ~5 Myr [7, 10]). 

 During the Late Amazonian, Planum Boreum 1, which 

was locally >1800 m thick, underwent planum-wide 

erosion, though there is some evidence for depositional 

hiatus. A resumption of rhythmic layer accumulation 

deposited unit ABb2a. The temporal extent of the unit 

ABb1 erosional episode is not known. Unit ABb2a may 

have begun accumulating during the most recent high 

obliquity cycle (estimated at ~20 Kyr [7, 10]). The original extents of units ABb1 and ABb2a are not precisely 

known; it is possible both units were severely eroded 

from previous extents. Time-transgressive contacts between units ABb2a, ABou2, and ABb2b allude to these materials forming (in part) simultaneously, perhaps by localized erosion and re-deposition of layered materials. 

These observed interfingerings and time-transgressive 

contacts are potential evidence for current large-scale 

erosion of the much of the quadrangle surface. 

 References. [1] Tanaka et al. (2005) USGS SIM 2888, 

1:15M scale. [2] Herkenhoff (2003) USGS I-2753, 

1:500K scale. [3] Cutts et al. (1976) Science 194, 1329-

1337. [4] Tanaka and Scott (1987) USGS I-1802-C, 

1:15M scale. [5] Thomas et al. (1992) in Mars, 767-795. 

[6] Herkenhoff and Plaut (2000) Icarus 144, 243–253. 

[7] Tanaka (2005) Nature 437, 991-994. [8] Tanaka et 

al. (2003) JGR 108, (E4), 8043. [9] Skinner et al. (2006) 

LPSC 37, abs. #1476. [10] Laskar et al. (2002) Nature

419, 374-377. 
GEOLOGY OF THE SOUTHERN UTOPIA PLANITIA HIGHLAND-LOWLAND BOUNDARY PLAIN: 

CURRENT UNDERSTANDING AND FIRST YEAR MAPPING PLAN. J. A. Skinner, Jr., K. L. Tanaka, T. M. 

Hare., and D. B. Christensen. Astrogeology Research Program, U. S. Geological Survey, 2255 N. Gemini Drive, 

Flagstaff, AZ 86001 (jskinner@usgs.gov). 

Introduction. Mars’ highland-lowland boundary 

(HLB) scarp spans >4000 m of elevation and >60o of 

latitude, borders at least three known giant impact basins 

(Utopia, Chryse, and Isidis), and transects, underlies, or 

bounds almost every currently-identified geologic unit. 

Modern (post-Viking Orbiter) data sets reveal that the 

HLB is generally accompanied by a geologically and 

stratigraphically complex plain of material along its 

down-slope margin (i.e., the highland-lowland “boundary” plain) [1-6]. In southern Utopia Planitia, the boundary plain forms bench-like platforms that contain depressions, pitted cones (some organized into arcuate chains 

and thumbprint terrain), isolated domes, lineated depressions, buried circular depressions, ring fractures, polygonal fractures, and other locally- to regionallydispersed landforms. Because the origins of these features are not well-understood, the objective of our mapping project is to clarify the geologic evolution of the 

southern Utopia Planitia HLB by identifying the geologic, structural, and stratigraphic relationships of surface materials in MTMs 10237, 15237, 20237; 10242, 

15242, 20242; 10247, 15247, 20247 (Fig. 1). 

Current Understanding. The southern Utopia HLB 

extends >1500 km westward from northern Nepenthes 

Mensae to the topographic saddle that separates the Isidis and Utopia Planitiae. The map area contains 20% 

Noachian highland materials, 60% Hesperian boundary 

plain materials, and 20% Amazonian lowland plain materials. These three geologic provinces and the transition 

between each hold important geologic and stratigraphic 

information. Yet, a coherent geologic and stratigraphic 

framework for interpreting these features based on the 

most modern data sets is currently lacking.

Highlands - Past geologic maps delineated the southern margin of the southern Utopia Planitia HLB as assemblages of Noachian and Hesperian basement and 

regolith materials that were eroded by fluvial activity, 

mass-wasting, impacts, and other geologic processes [3-

5]. Remnants of the Utopia impact massifs and/or ejecta 

blanket are not generally detected aside from cursory 

morphologic inference [e.g., 6]; these have been either 

deeply buried or eroded beyond recognition. 

Boundary plain - The southern Utopia boundary plain 

is divided into the Early Hesperian Utopia Planitia 1 unit 

and the Late Hesperian Utopia Planitia 2 unit [3]. These 

two units cover the majority of our selected quadrangles. 

The boundary plains units and their contained morphologies are interpreted to be evidence of temporally 

and spatially pervasive deposition and/or modification of 

the dichotomy boundary during the Hesperian, prior to 

the Early Amazonian emplacement of Vastitas Borealis 

units [3,6]. The transition between these two HLB units 

is demarcated by isolated and scalloped depressions of 

Amenthes Cavi, which are unique to the southern Utopia 

boundary plain and well-covered by our selected MTM 

quadrangles. Among the suggested origins of boundary 

plain landforms are (1) marginal marine erosional platforms [7-10], (2) surficial cryoturbation vestiges [11], 

(3) highland detritus of varying thickness and origin [12-

13], and (4) soft-sediment deformation products [6].

Figure 1. Mars globe centered at 120o E, 10oN showing the nine quadrangles that cross the southern Utopia Planitia HLB. Orthographic 

projection of MOLA shaded-relief image.

 Lowlands – The four units that previously comprised the Vastitas Borealis Formation [14-15] were 

recently re-interpreted as only two stratigraphicallydiscrete geologic units (e.g., the Vastitas Borealis marginal and interior units) based on well-defined crater 

counts and other stratigraphic relationships [3, 11]. The 

Vastitas Borealis units, which are variably pockmarked 

with eroded and/or exhumed impact craters, extend 

northward from the southern Utopia Planitia boundary 

plain into the broader lowland basins. These materials 

are generally interpreted as laterally-gradational, sedimentary sequences derived from the erosion of highland, 

boundary, and lowland terrains, locally to regionally 

interfingered with volcanic materials [3, 7, 9-11]. While 

the most recent lowland plains surface formed during the 

Early Amazonian [3, 14-16], it is unclear to what degree 
the exposed surface represents combined depositional 

and modificational processes.

 Mapping Method. Our base maps include fullcoverage image and topographic data sets, including the 

Viking MDIM 2.1 (231 m/px), MOLA 1/128 px/degree 

(463 m/px) digital elevation model, the THEMIS IR 

mosaic (231 m/px), and the MOC WA mosaic (231 

m/px) along with various supplemental map layers and 

ancillary information (e.g. topographic high-pass filters 

and internet-hotlinked THEMIS VIS and IR footprints). 

We use ArcGIS®

 as our map environment and will continually update metadata over the life of the project in 

order to improve documentation during the mapping 

stages and to ease production of a final map product. 

We are using both “classical” and updated planetary 

mapping methods [3, 17-19]. Because many of the materials that form the southern Utopia Planitia HLB are 

likely to be dispersed sedimentary sequences [3-6, 11], 

daytime and nighttime thermal data provide critical information for defining unit boundaries (where not covered by dust), particularly as such sequences may laterally grade into other materials. Where possible, particularly in the wall-rock of high-standing, eroded highland 

materials adjacent to the HLB scarp, we are examining 

bedding locations, paying close attention to the character 

and continuity of such features as they may hint at subsurface layering. 

Year 1 Work Plan. The beginning of our Year 1 

work plan has focused on (1) creating/updating crater 

inventories and (2) surveying, comparing, and contrasting morphologic features that dominate the region. 

Firstly, we are logging crater locations, diameters, and 

ejecta characteristics. This task also provides a cursory 

examination of the regional geology using “exploratory” 

methods during the early stages of mapping. Crater densities (and “curves”) provide a means to infer both the 

age and resurfacing history of any given surface, particularly when used to supplement cross-cutting information. We are currently locating all craters within the 

selected mapping quadrangles that are ≥ 2 km diameter. 

In addition, we are tabulating the erosional state of crater 

ejecta (“high,” “medium,” or “low”) as a preliminary 

proxy for superposition (e.g., a “low” erosional state 

may signify the effects of post-impact modification) 

[20]. Secondly, we are surveying and then comparing 

and contrasting morphologic features that dominate the 

region. We began this effort by using landform assessments of past mapping efforts [3-5] and topical studies 

[6, 11-13], including highland-transitional landforms 

such as knobs, mesas, mass-wasting fans, and channels, 

and lowland-transitional landforms such as lobate margins, pitted cones, and depressions. We are also using 

thermophysical characteristics to identify potentially 

unique geologic surfaces. Of particular interest in this 

early part of the study is to characterize, without preconception, a distinct thermophysical transition from the 

boundary plain into the lowland plain. This transition is 

dominated by south-facing, overlapping, (relatively) 

lower thermal inertia, thin lobes that appear to have been 

emplaced around (relatively) higher thermal inertia surfaces and knobs [3, 6]. This area coincides with a general increase in regional crater onset diameters (the diameter at which crater ejecta transitions from ballistic to 

lobate) [6], perhaps indicating a local shallowing of subsurface water and/or ice. 

Year 1 Anticipated Results. Total Year 1 efforts will 

consist of (1) processing and geo-registration of pertinent data sets, (2) cataloging of craters ≥ 2 km in diameter and assignment of a preliminary “high,” “medium,” 

or “low” ejecta erosional state, (3) geology, geomorphology, and structure mapping, (4) and nomenclature 

updates and refinements. These efforts will result in, by 

the close of Year 1, a preliminary assessment of quadscale geomorphologies (and any clustered variability 

thereof) and stratigraphic characteristics of regional surfaces. Relative ages and units will be resolved using the 

crater inventory as well as the observed erosional state 

of the ejecta. We will use this information to delineate 

preliminary geologic units to stratigraphically correlate 

map units. Year 2 efforts will focus on testing and revamping Year 1 map results with intent to submit map 

for review by the beginning of Year 3.

References. [1] McGill, G.E., (2005) USGS I-2811, 

1:1M scale. [2] Irwin, R.P., et al., (2004) J. Geophys. 

Res. 109. [3] Tanaka et al., (2005) USGS SIM 2888, 

1:15M scale. [4] Scott, D.H. and Carr, M.H., (1978) 

USGS I-1083, 1:25M scale. [5] Greeley, R. and Guest, 

J.E., (1987) USGS I-1802-B, 1:15M scale. [6] Skinner, 

J.A. Jr. et al., (2007) Icarus, 186, 41-59. [7] Head, J.W. 

III, et al. (1999) Science, 286, 2134-2137. [8] Thomson, 

B.J. and Head, J.W. III, (2001) J. Geophys. Res., 106, 

23,209-23,230. [9] Parker, T.J., et al., (1989), Icarus, 

82, 111-145. [10] Parker, T.J., et al., (1993) J. Geophys. 

Res., 98, 11,061-11,078. [11] Tanaka, K.L. et al., 

(2003a) J. Geophys. Res., 108, (E4). [12] McGill, G.E., 

(1989) J. Geophys. Res., 94, 2753-2759. [13] 

Buczkowski, D.L. et al., (2005) J. Geophys. Res., 110, 

E03007. [14] Scott, D.H. et al., (1986-87) USGS I-1802-

A/B/C, 1:15M scale. [15] Tanaka, K.L., (1986) J. Geophys. Res., 91, E139-158. [16] Head, J.W. III et al. 

(2002) J. Geophys. Res., 107, (E1). [17] Wilhelms, D.E., 

(1990) in Planetary Mapping (R. Greeley and R.M. Batson (eds.)), Cambridge U. Press. [18] Hansen, V.L. 

(2000) EPSL, 176, 527-542. [19] Skinner and Tanaka 

(2003) LPSC XXXIV, abs. #2100. [20] Barlow, N.G. 

(2006) LPSC XXXVII, abs. #1337.
NEW GLOBAL GEOLOGIC MAP OF MARS. K. L. Tanaka1

, James M. Dohm2, Trent M. Hare1, R. P. Irwin, 

III3

, E. J. Kolb4, and J. A. Skinner, Jr.1, 1U.S. Geological Survey, Flagstaff, AZ (ktanaka @usgs.gov), 2U. Arizona, 

Tucson, AZ, 3

Smithsonian Inst., Washington, DC, 4Arizona State U., Tempe, AZ 

 

Introduction. We recently received a NASA 

Planetary Geology and Geophysics grant to remap the 

global geology of Mars at 1:20M scale (printed), 

which will employ the lower resolution mapping data 

sets in Table 1 and digital tools and approaches using 

the latest Geographic Information Systems technology. 

Our work plan runs for five years (2007 to 2011; the 

Viking-based global map at 1:15M scale and more 

recent northern plains map at 1:15M scale each took 

~six years to complete). Our team includes additional 

colleagues who will contribute mapping of particular 

features and regions, perform detailed crater counts, 

and provide additional analyses of the mapping results. 

Along the way, we will present our progress, including 

preliminary results and updated thinking about geologic and stratigraphic schemes for Mars. We will 

encourage input from the planetary geology community during the course of the project as the results of 

concurrent studies by others will help us to improve 

our global geologic map in various ways. 

Table 1. Mars geologic mapping data sets. MOLA = 

MGS Mars Orbiter Laser Altimeter; THEMIS = ODY 

Thermal Emission Imaging System; HRSC = MEX 

High Resolution Stereo Color camera; CTX = MRO 

Context Camera; IR = infrared, VIS = visual range.

Data Type Resolution 

(m/pixel) 

Current 

coverage 

MOLA Altimetry 460 (115 at 

poles) 

global 

THEMIS 

IR 

Infrared images 100 global 

HRSC Color, stereo 

images 

10 to 30 extensive 

THEMIS 

VIS 

Visual range 

images 

18 to 40 patchy 

CTX Visual range 

images 

6 little 

Issues that can be addressed. Our newly-funded 

global mapping project will achieve a better understanding of the global geology of Mars. In particular, 

we will focus on the following science objectives. 

1. Update global stratigraphy. Each previous 

global map of Mars has resulted in constructions and 

formal definitions of global stratigraphic and chronologic schemes, first with the establishment of the 

Noachian, Hesperian, and Amazonian Periods from 

Mariner 9-based mapping [1], and later with the subdivision of the periods into Early, Middle, and Late 

epoch divisions using Viking images [2-3]. A “preNoachian epoch” was introduced in the northern plains 

map [4], based on the recognition of quasi-circular 

depressions indicative of primordial, buried crustal 

material underlying the oldest determined exposed 

Noachian surface materials [5]. Another major stratigraphic revision was the re-assignment of the beginning of the Amazonian Period to the surface age of the 

Vastitas units of [4] (those units are roughly equivalent 

to the Vastitas Borealis Formation of [2]). These units 

are much more geologically and spatially significant 

and broadly coeval than the lava flows of Amazonis 

Planitia previously used as the basal Amazonian stratigraphic marker, which are now perceived to have a 

complex stratigraphy [4]. Global mapping will provide 

us with the proper perspective to consider whether any 

other significant revisions to the unit-based stratigraphic divisions ought to be made, such as to represent younger deposits related to climate cycling [4, 6-

7], as well as re-evaluation of each Martian epoch. 

Furthermore, discrepancies exist in crater sizefrequency distributions at the most critical diameter 

range, between ~1 and 20 km, where the distributions 

are most at odds [8]. Discrepancies also exist at larger 

diameters [cf. 9-10]. Our work will provide an extensive database of crater size-frequency data as a function of geologic units in these critical diameter ranges. 

The new mapping and crater statistics, when applied 

judiciously (with proper consideration to resurfacing) 

will result in an improved scheme of Martian epochs 

defined by crater densities. In turn, ages and rates of 

geologic activity can be estimated [e.g., 8], which can 

be useful for scientific and mission-related applications. 

2. Update global tectonic history. Global structural 

mapping will permit refinement of the tectonic history 

for Mars, as follows: 

(a) Contractional history. Viking-based mapping 

of wrinkle ridges recognized few ridges in the northern 

plains and indicated stress sources primarily due to 

Late Noachian and Early Hesperian global contraction 

and local compression caused by outflow channel erosion and Tharsis tectonism [11]. MOLA shaded-relief 

and detrended maps and THEMIS day IR images permit identification and mapping of wrinkle ridges previously unrecognized in Viking images [4]. Furthermore, some wrinkle ridges located in the northern 
plains may have been active more recently than previously interpreted, perhaps during the Late Hesperian 

and Early Amazonian [4]. Remapping and relative-age 

dating of wrinkle ridges will better constrain lithospheric stress history, particularly in the highlands. 

(b) Extensional history. We do not expect significant alteration to the line mapping of extensional structures such as graben and rifts because much of the 

original printed maps have been digitally renovated, 

including improved spatial registration [12]. This 

renovation improved the positioning of previously 

mapped tectonic structures, which enabled their accurate registration to more recent global data sets (e.g., 

MOLA DEM and MDIM 2.1) [12]. We do, however, 

anticipate some refinement in the constraints to dating 

of these features as they relate to newly-defined geologic units and their boundaries. We can also more 

adeptly assess relative-age information for globallymapped tectonic features through the application of 

digital tools, improved mapping, and more detailed 

crater counting of the map units that constrain their 

ages. Impact craters and their preservation states can 

be more precisely delineated and characterized using 

THEMIS IR images rather than with panchromatic, 

visible-range Viking images. 

3. Analysis of fluvial valleys, paleolakes, oceans, 

and surficial mantles. Our global mapping will provide 

the broadest context to search for geologic associations 

that various climatic/hydrologic scenarios predict. We 

can document the relative timing and spatial relations 

of major fluvial, mass wasting, and potential glacial 

erosion vs. age of emplacement of sedimentary and 

other possibly related units. For example, a significant 

gap in time between valley network activity and plains 

emplacement would suggest non-fluvial materials, 

whereas contemporary deposits would be consistent 

with a fluvial origin or perhaps a combined fluvial and 

volcanic suite where magma/volatile interactions have 

occurred. 

The relative-age relationships between fluvial erosion and extensive mantling (sedimentary or volcanic) 

events will help to characterize the activity during 

waning stages of activity, perhaps when the supply of 

water was episodic. In areas where extensive eolian 

deflation has not occurred, mantle deposits can be 

dated relative to fluvial activity by simple cross-cutting 

and burial relationships. In addition, catastrophic 

floods sourced from chaos within highland material 

may have ponded in the northern plains as transient 

oceans and/or lakes, perhaps causing the punctuated 

development of short-lived (tens of thousands of 

years?) regional to global hydrologic cycles and climatic perturbations [13-14]. The latter may have 

caused environmental conditions (and, thus, geologic 

conditions) at the surface to deviate, perhaps significantly, to an unusually warm and wet Mars [e.g., 13-

16]. Despite such assertions, geologic evidence for a 

paleo-ocean remains inconclusive [e.g., 16], perhaps 

because the large amount of time since their putative 

existence has allowed for thorough erosional masking. 

Oceans may also have formed by elevation-controlled 

surface runoff [17] or ground-water discharge [18-19], 

hypotheses that can be tested with a global map and 

the MOLA data set. Alternatively, topographicallycontrolled groundwater basins may have inhibited the 

delivery of highland recharged groundwater to a putative northern ocean. We can also assess the timing and 

distribution of features potentially related to precipitation and ground-water recharging hypotheses that involve sapping [e.g., 19] and tapping of Tharsis and 

east Hellas aquifers that led to catastrophic discharges 

evident in the carving of outflow channels [20-21]. 

4. Other volatile-related processes. These processes include deposition and exhumation of ice and 

dust mantles [6], volatile-exchange and weathering in 

near-surface materials (including formation of phyllosilicates and hydrous sulfates [22-23]), and cryoturbation and soft-sediment deformation [24]. Global 

examination of such processes will help us understand 

the volatile history within the near surface and its relation to geologic and climate history. 

References: [1] Scott D.H. and Carr M.H. (1978) 

USGS Map I-1083. [2] Scott D.H. et al. (1986-87) USGS 

Maps I-1802-A, B, C. [3] Tanaka K.L. (1986) JGR 91, 

suppl., E139-E148. [4] Tanaka K.L. et al. (2005) USGS 

Map SIM-2888. [5] Frey H.V. (2004) LPS XXXV, Abstr. 

#1382. [6] Mustard J.F. et al. (2001) Nature 412, 411-

414. [7] Head J.W. et al. (2003) Nature 426, 797-802. [8] 

Hartmann W.K. and Neukum G. (2001) Space Sci. Rev. 

96, 165-194. [9] Barlow N.G. (1988) Icarus 75, 285-305. 

[10] Frey H.V. et al. (2002) GRL 29, 1384. [11] Tanaka 

K.L. et al. (1991) JGR 96, 15617-15633. [12] Skinner 

J.A., Jr. et al. (2006) LPS XXXVII, Abst. #2331. [13] 

Baker V.R. et al. (1991) Nature 352, 589-594. [14] Fairén 

A.G., et al. (2003) Icarus 165, 53-67. [15] Parker T.J. et 

al. (1993) JGR 98, 11061-11078. [16] Carr M.H. and 

Head J.W. (2003) JGR 108, 5042. [17] Craddock R.A. 

and Maxwell T.A. (1990) JGR 95, 14265-14278. [18] 

Tanaka K.L. et al. (2003) JGR 108, 8043. [19] Grant J.A. 

(2000) Geology 28, 223-226. [20] Harrison K.P. and 

Grimm R.E. (2004) GRL 31, doi:10.1029/2004GL020502. 

[21] Crown D.A. et al. (2005) JGR 110, 

doi:10.1029/2005JE002496. [22] Bibring J-P. et al. 

(2006) Science 312, 400-404. [23] Wyatt M.B. et al. 

(2004) Geology 3, 645-648. [24] Skinner J.A. Jr. and Tanaka K.L. (2007) Icarus 186, 41-59. 
RECENT GEOLOGIC MAPPING RESULTS FOR THE POLAR REGIONS OF MARS. K.L. Tanaka1

 and 

E.J. Kolb2

,

 1Astrogeology Team, U.S. Geological Survey, Flagstaff, AZ 86001, ktanaka@usgs.gov, 2

Arizona State 

University, Tempe, AZ 85287, eric.kolb@asu.edu. 

Introduction: The polar regions of Mars include the 

densest data coverage for the planet because of the polar 

orbits of MGS, ODY, and MEX. Because the geology of 

the polar plateaus has been among the most dynamic on 

the planet in recent geologic time, the data enable the 

most detailed and complex geologic investigations of any 

regions on Mars, superseding previous, even recent, mapping efforts [e.g., 1-3]. Geologic mapping at regional and 

local scales is revealing that the stratigraphy and modificational histories of polar materials by various processes 

are highly complex at both poles. Here, we describe some 

of our recent results in polar geologic mapping and how 

they address the geologic processes involved and implications for polar climate history. 

North polar stratigraphy: The exposed geologic record for the north polar region appears largely limited to 

the Amazonian Period, as redefined by [3]. The north 

polar plains are made up of the Vastitas Borealis units, 

perhaps emplaced as fluvial sediments and (or) periglacially reworked material at the beginning of the Amazonian following cessation of outflow-channel discharges 

from the Chryse region [3]. 

Thereafter, the Scandia region unit was emplaced in 

the form of circular plateaus and irregular hilly complexes 

of Scandia Tholi and Cavi and planar deposits that have 

since eroded into knobs and mesas, forming Scandia 

Colles. This unit may have once covered ~1.5 x 106

 km2

of the plains north of Alba Patera to Planum Boreum to an 

average thickness of 100 m. We interpret that the material 

represents deposits related to mud-diapir-like processes, 

possibly redistributed by wind. In this scenario, the north 

polar gypsum discovered by the OMEGA instrument [4] 

may relate to Alba Patera magmatism [5]. 

Possibly coeval with and following formation of the 

Scandia region unit was emplacement of evenly to wavybedded material forming the Rupes Tenuis unit [6]. This 

material forms the base of much of Planum Boreum. West 

of Chasma Boreale, along the Rupes Tenuis scarp, the 

unit includes more than 20 beds and is >1000 m thick. A 

number of large impact craters on the unit indicate that it 

is a fairly ancient polar deposit. In spite of the unit’s great 

thickness, it appears to be completely eroded back to an 

abrupt margin. Possibly correlative is the mantle material 

that forms the bases of >1800 pedestal craters in surrounding plains [7]. 

Perhaps during much of the Amazonian, dark, (possibly made up of weathered basalt [8]) dune fields migrated 

across the circum-polar plains mainly north of 70oN 

where dunes are presently common. We map the current 

dune fields as the Olympia Undae unit, after the largest 

dune field. This unit also includes rippled surfaces as seen 

in MOC images that may form an underlying, indurated 

sand sheet. Some of the present dune fields originate 

from steep scarps exposed on the margins of Abalos 

Mensa, from Boreum and Tenuis Cavi at the head of 

Chasma Boreale, and from reentrants of Olympia Cavi 

into Planum Boreum. The bases of the scarps include 

dark, cross-bedded bright and dark layered material 

mapped as the Planum Boreum cavi unit [9]. Some of 

the dunes of Olympia Undae are embayed by the young 

mid-latitude mantle [10] and the youngest polar layered 

deposits (Planum Boreum unit 2). 

The Planum Boreum cavi unit grades upwards into 

Planum Boreum 1 unit, which forms the majority of 

what are commonly referred to as “polar layered deposits” (however, other polar deposits are also layered, thus 

the term is now ambiguous). The unit includes dozens 

of unconformities as seen in MOC images, which may 

be related to changing patterns of spiral-trough development and (or) local variations in topographically controlled depositional environments [11]. Correlation of 

layer sequences exposed in various troughs is challenging, but rhythmic sequences of layers ~30-m-thick have 

been detected [12]. Deformation within this unit is 

rarely observed, such as near Udzha crater [13]. 

Within Chasma Boreale and troughs and adjacent 

plains of Planum Boreum, several dark layers form a 

sequence as much as 200 m thick and forms the Planum 

Boreum 2 unit. This unit is sculpted with yardangs and 

within Chasma Boreale is embayed by dozens of bright 

layers of the Chasma Boreale unit, which also includes 

yardangs. In turn, the youngest layered deposit, Planum 

Boreum 3 unit, consists of several layers as much as a 

few tens of meters thick that unconformably overlie 

older Planum Boreum units. In turn, the residual ice cap 

forms the Planum Boreum 4 unit, which rests unconformably on underlying materials [14]. The basal layer 

of the upper unit appears to be made up of a sandy, dark 

layer, which is the source of veneers of material that 

appear to contribute to erosion of the spiral troughs and 

related undulations [15]. 

South polar stratigraphy: In contrast to the north 

polar region, the south polar region exposes a geologic 

record that extends into the Noachian Period. Here, the 

oldest rocks form the Noachis Terra unit and consist of 

impact breccia and melt, volcanic materials, and eolian 

and other sediment of the southern cratered highlands. 

Many impact craters within the highland terrain have 

undergone degradation and removal, and some unusual 

remnants, perhaps modified by volcanism, form the 

rounded massifs of the Sisyphi Montes unit [16]. Also, 

outpourings of likely volcanic material during the Late 

Noachian through Early Hesperian formed the Aonia 

Terra, Malea Planum, and Terra Cimmeria units. 
Throughout the Hesperian, the nearly circum-polar 

deposits of the Dorsa Argentea province were emplaced, 

forming a complex sequence consisting of lobate plains 

and superposed sinuous ridges, high-standing rugged terrain, and depressions. These unusual characteristics have 

led to various interpretations [see 2 and references 

therein]. We divide the Dorsa Argentea province into 

eight units that differ markedly from those mapped by [1]. 

The province includes: (1) a thick basal sequence of layered deposits exposed within the pits of Cavi Angusti and 

Sisyphi Cavi, (2) a high-standing rugged member that 

includes pitted cones and ridges, (3) five units of plains 

materials, and (4) a thick, fine-grained friable planar deposit that caps mesas and plateaus of Cavi Angusti. We 

suggest that the deposits and structures are best explained 

collectively by cryovolcanic eruptions and discharges of 

volatile-rich, fluidized slurries formed by the mixing of 

subsurface volatiles with fine-grained, unconsolidated 

crustal material and perhaps cryoclastic ash. This activity 

may have arisen from instabilities in Hesperian aquifers 

and triggering events caused by seismic shaking, fracturing, intrusions, and loading by polar deposition [2]. 

The Planum Australe 1 unit forms the majority of 

Planum Australe, the south polar plateau, reaching a 

maximum thickness of ~3 km within the plateau’s thickest region, Australe Mensa. The unit is exposed along 

plateau margins and within canyons, and its basal layer 

sequences are perhaps Early Amazonian in age. A regional unconformity identified in the chasmata of Promethei Lingula and the curvilinear canyons of Australe 

Scopuli divides the Planum Australe 1 unit into the lower 

and upper members. The erosion associated with the unconformity was primarily wind and sublimation driven, 

and occurred after approximately one-third of the Planum 

Australe 1 unit stratigraphy was emplaced. The unconformity’s orientation and outcrop expression indicates the 

chasmata formed by down-cutting of Planum Australe 1 

unit surface depressions formed where the unit overlies 

uneven substrate [17] and marks the initiation of curvilinear canyon formation within Australe Scopuli [18]. 

The Planum Australe 2 unit unconformably buries 

eroded Planum Australe 1 surfaces. The unit was emplaced after the canyons had largely reached their current 

form and after the plateau margins underwent extensive 

removal from Argentea, Promethei, and Parva Plana. The 

unit is <300 m thick and is comprised of layers that are 

slightly thicker than those of Planum Australe 1 unit. 

The Planum Australe 3 unit crops out mostly in a series of narrow, shallow (<~200 m) curvilinear Australe 

Mensa canyons between 270°E and 30°E and on the 

floors of canyons that cut the southernmost sections of 

Australe Scopuli [19]. The unit is ~300 m thick and is 

comprised of 6-7 uniformly thick, conformable layers; 

individual layers have undergone differential erosion, 

resulting in an outcrop profile of cliffs and terraces. The 

characteristic low-to-intermediate albedo of the individual 

layers suggests they are relatively dust rich. The unit 

unconformably overlies the Planum Australe 1 and 2 

units. 

The Planum Australe 4 unit delineates the residual 

ice cap, the bright, <~10 m-thick veneer centered between 225°E through 45°E and poleward of ~82°S. The 

upper member consists of the high-albedo CO2-

dominated sections [20] of the residual ice cap and constitutes the majority of the deposit’s areal extent. The 

lower member is a thin basal layer consisting of water 

ice [21-22] that forms the moderate-albedo margins of 

the residual ice cap. The unit unconformably overlies 

the Planum Australe 1 through 3 units. 

Synthesis of polar geology: Polar deposits include 

atmospheric volatile and dust precipitates and aeolian 

dunes and sheets made up of basaltic fines that have 

undergone some moderate cementation and weathering 

and extensive aeolian reworking. Our mapping studies 

generally indicate that the availability of dust, sand, and 

volatiles controlled by climate conditions and geologic 

activity and the variable circum-polar wind patterns 

controlled by topography and weather conditions have 

resulted in a complex history of accumulation and erosion at Planum Boreum and Planum Australe. Both 

climate-related cycles operating at differing time scales 

as well as unique geologic and climatic events have 

driven these processes. However, we find no compelling evidence for glacial-like deformation and for basal 

melt-water discharge of polar deposits. 

References: [1] Tanaka K.L. and Scott D.H. (1987) 

USGS Map I-1802-C. [2] Tanaka K.L. and Kolb E.J. 

(2001) Icarus 154, 3-21. [3] Tanaka K.L. et al. (2005) 

USGS Map SIM-2888. [4] Langevin Y. et al. (2005) 

Science 307, 1584-1586. [5] Tanaka K.L. (2006) 4th

Mars Polar Sci. Conf. Abs. #8079. [6] Tanaka K.L. et 

al. (2006) LPSC XXXVII, Abs. #2344. [7] Skinner J.A., 

Jr. (2006) LPSC XXXVII, Abs. #1476. [8] Wyatt M.B. 

et al. (2004) Geology 32, 645-648. [9] Byrne S. and 

Murray B.C. (2002) JGR 107, 5044. [10] Mustard J.F. 

et al. (2001) Nature 412, 411. [11] Fortezzo C. and Tanaka K.L. (2006) 4th Mars Polar Sci. Conf. Abs. #8079. 

[12] Milkovich S.M. and Head J.W. (2005) JGR 110, 

doi:10.1029/ 2004JE002349. [13] Tanaka K.L. (2005) 

Nature 437, 991. [14] Skinner J.A., Jr. et al. (2006) 4th

Mars Polar Sci. Conf. Abs. #8083. [15] Rodriguez 

J.A.P. et al. (2006) LPSC XXXVII, Abs. #1437. [16] 

Rodriguez J.A.P. and Tanaka K.L. (2006) 4th Mars Polar Sci. Conf. Abs. #8066. [17] Kolb E.J. and Tanaka 

K.L. (2006) Mars 2, 1-9. [18] Kolb E.J. and Tanaka 

K.L. (2006) 4th Mars Polar Sci. Conf. Abs. #8085. [19] 

Kolb E.J. and Tanaka K.L. (2006) LPSC XXXVII, Abs. 

#2408. [20] Bibring et al. (2006) Nature 428, 627. [21] 

Byrne S., and Ingersoll A.P. (2003) Science 299, 1051. 

[22] Titus T.N., Keiffer H.H., and Christensen P.R. 

(2003) Science 299, 1048. 
MARGARITIFER TERRA QUADRANGLES -20012 AND -25012: REVIEWED AND RESUBMITTED. 

S. A. Wilson1

, J. A. Grant1 and C. M. Fortezzo2,

 1Center for Earth and Planetary Studies, National Air and Space 

Museum, Smithsonian Institution, Washington, DC 20560, 2

 Department of Geology, Northern Arizona University, 

Flagstaff, AZ 86011. 

Introduction: Valley networks and associated landforms in Margaritifer Terra (Figure 1), located southeast 

of Valles Marineris, reflect a complex history involving 

water transport, storage, and release [1-6]. Margaritifer 

Terra straddles a depression known as the Chryse trough 

[7], with the Uzboi-Ladon-Margaritifer (ULM) northward-flowing, mesoscale outflow system draining the 

west side of the trough [2], and the Samara and ParanáLoire valley systems draining the east side of the trough 

[3-5]. Both valley systems merge in Margaritifer basin 

near the head of Ares Vallis [5] (Figure 1). 

Mars Transverse Mercator (MTM) -20012 and -25012 

(latitude 17.5oS to 27.5oS between 345oE and 350oE) are 

two of multiple quadrangles in a series of 1:500,000-scale 

study areas on Mars sponsored by NASA Planetary Geology and Geophysics Program grants (NAG5-4157, 

NAG5-10390). These two quadrangles cover a portion of 

Margaritifer Terra (Figure 1) centered on the collection 

basin between Loire Valles to the west and Paraná Valles 

to the east (Figures 2 and 3). 

Map Status and Results: MTM quadrangles -20012 

and -25012 were submitted, reviewed, updated and resubmitted in June, 2007. MTM quadrangles -10022 and -

15022 are submitted and in review. The results from 

mapping quadrangles -20012 and -25012 are emphasized 

here (Figures 2 and 3). 

The degraded Ladon and Holden multi-ringed impact 

basins [8] are the oldest features in Margaritifer Terra 

(Figure 1), followed by evolution of the cratered upland 

surface (Nm and Npld in Figures 2 and 3). Subsequently, 

widespread resurfacing events occurred [4, 5]. The first 

two resurfacing events, which are not in the map area, 

date to the early to middle Noachian with the second 

event ending at an N5 age of around 1000 (number of 

craters >5 km in diameter per 1,000,000 km2

). The third 

resurfacing event (HNsp), which began in the late Noachian (N5 age ~300), was coincident with waning highland volcanism. From the late Noachian extending into at 

least the early [5] or middle to late [9] Hesperian, valley 

networks (HNvn), dissected terrain (HNspd), fans (Hspf), 

positive-relief chaotic terrain (Hctp) and depositional 

sinks formed. The initial collapse of the Margaritifer 

Chaos in the Margaritifer basin occurred at this time, as 

well as chaos to the northwest of the basin (Figure 1). A 

final, more localized resurfacing event (AHsp) began in 

the middle Hesperian (N5 age ~130), typically embaying 

many of the valleys and channels [4, 5]. Whereas the 

older resurfacing events (including HNsp) created widespread plains that may be related to a variety of processes, 

the final resurfacing event (AHsp) emplaced materials we 

favor as volcanic rather than sedimentary in origin based 

on the presence of wrinkle ridges, occasional lobate morphology [5], confinement to topographic basins, and a 

paucity of valleys. 

The duration of valley formation is uncertain; some 

drainages along the ULM valley system may have extended into the Hesperian (N5 ~150), and late-stage flows 

may have been concurrent with local volcanic activity 

into the early Amazonian (N5 ~40) adjacent to the ULM 

system in quadrangles -10022 and -15022 (Figure 1). 

Additional mapping of the Samara and Paraná-Loire 

Valles and adjacent drainages is underway (Figure 1), and 

should help place further constraints on the timing and 

extent of valley formation. 

Figure 1. MOLA Topography of Margaritifer Terra. Reviewed and re-submitted MTM quadrangle maps (white 

boxes), funded maps (black boxes) and maps under review (red boxes) are shown. Contour interval is 1 km and 

north is towards the top of the image. 

Ongoing Mapping in Margaritifer Terra: Mapping 

in Holden crater in SW Margarititfer Terra is underway as 

part of a new project. Impact megabreccia is unconformably overlain by distal alluvial fan and/or lacustrine sediments that were deposited during two or more Noachianage phases of aqueous activity. A lower and mechanically 
weak, light-toned, layered, phyllosilicate-bearing unit 

exhibits few resolvable blocks and laterally continuous 

(on a kilometer scale), meter to sub-meter thick beds. 

This light-toned, layered unit was likely deposited in a 

distal alluvial or lacustrine environment. Dark-toned layers with little or no phyllosilicates drape the lower sequence and were emplaced during later, relatively shortduration, high-magnitude flooding as a confined Uzboi 

Vallis lake overtopped the Holden rim (Figure 1). The 

diverse stratigraphy exposed in Holden crater provides a 

rare opportunity to evaluate the changing potential for 

habitability during the Noachian Period. 

Figure 2. Completed 1:500,000 map of MTM -20012 and 

-25012 covering the headward reaches of the ParanáLoire Vallis systems. Mapped units are described in Figure 3. 

 

Figure 3. Correlation of mapped units in Figure 2. Relative ages are expressed as the number of craters larger 

than 5 km-in-diameter per 1,000,000 km2

 and were derived via comparison to [10] and [11] on the left side and 

right side, respectively. The oldest materials in the map 

are heavily cratered mountainous material (Nm) and dissected highland material (Npld). The Noachian/Hesperian 

smooth plains resurfacing unit (HNsp) was emplaced before the valley networks (HNv) and associated degraded 

surfaces (HNspd), the positive-relief chaotic terrain 

(Hctp), and the fan (Hspf). The Amazonian/Hesperian 

smooth plains resurfacing unit (AHsp) typically embays 

valleys, channels and older materials. Craters mapped as 

c3, c2, and c1, are well-preserved, moderately preserved 

and heavily degraded, respectively. 

References: [1] Saunders, S.R., 1979, USGS Map I-1144. [2] Parker, T.J., 1985, MS Thesis, Cal. State Univ., LA. [3] Grant, J.A., 

1987, NASA Tech. Memo. 89871, 1-268. [4] Grant, J.A., 2000, Geology, 28, 223-226. [5] Grant, J.A., and Parker, T.J., 2002, J. Geophys. Res., 107, 10.1029/2001JE001678. [6] Hynek, B.M., and R.J. Phillips, 2001, Geology, 29, 407-410. [7] Phillips, R.J., et al., 2001, 

Science, 291, 2587-2591. [8] Schultz, P.H., et al., 1982, J. Geophys. Res., 87, 9803-9820. [9] Rotto, S., and K.L. Tanaka, 1995, USGS 

Map I-2441. [10] Neukum, G. and Hiller K., 1981, J. Geophys. Res., 86, 3097-3121. [11] Hartmann, W.K. and Neukum, G., 2001, 

Space Science Rev., 96, 165-194. 

2
GEOLOGIC MAPPING OF THE MEDUSAE FOSSAE FORMATION ON MARS (MC-8 SE). J. R. 

Zimbelman, CEPS/NASM, Smithsonian Institution, Washington, D.C. 20013-7012 (zimbelmanj@si.edu). 

Introduction: This report summarizes the status 

of a mapping project supported by NASA grant 

NAG5-11743 (the no-cost extension of which ended 

in April of 2006), and the current plans for new 

mapping of the Medusae Fossae Formation (MFF) on 

Mars through a proposal that was selected for 

funding by the Planetary Geology and Geophysics 

program in March of 2007. Money has not yet been 

received for this new grant, but here we present the 

areas identified in the proposal for mapping during 

the next three years. 

MC-8 SE: Mapping in the eastern portion of 

MFF was initiated at 1:500K scale using the best 

available Viking images, then mapping commenced 

at 1:4M scale to provide a broader context. As 

THEMIS daytime IR coverage became steadily more 

complete, a map-projected base of daytime IR images 

was used for mapping at 1:2M scale, which we 

concluded was the best scale for portraying the MFF 

geology on the new base materials [1]. During the 

no-cost extension of the old grant, mapping 

proceeded to the point of completing a 1:2M scale 

map for the MC-8 SE quadrangle (0° to 15°N lat., 

202.5° to 225°E long.) (Fig. 1, which includes a 0.5° 

margin around the quadrangle). Little change in the 

Figure 1. 2007 version of the MC-8 SE geologic 

map. See Fig. 2 for correlation of geologic units. 

unit locations or designations (Fig. 2) are present on 

the new map, relative to the mapping and stratigraphy 

presented at the 2006 Mappers meeting, but 

structural mapping has been added in the new map. 

As a result of the mapping, we have identified six 

subunits to the upper member of MFF and three 

subunits to the middle member of MFF, expanding 

on the units as designated by Scott and Tanaka [2]. 

Conclusive evidence for the origin of the enigmatic 

Figure 2. Correlation chart of the geologic units 

identified from mapping of MC-8 SE (Fig. 1). All 

units are derived from those as originally identified 

by Scott and Tanaka [2]. 

MFF materials remains elusive, but considerable 

progress has been made in evaluating the numerous 

hypotheses of formation that have been proposed for 

MFF. Our results to date have either an ignimbrite or 

an aeolian origin as the hypotheses with the greatest 

likelihood of being a part of the MFF story. We are 

optimistic that new data, such as the spectacular 

images now being returned by the High Resolution 

Imaging Science Experiment (HiRISE) (Fig. 3), plus 

results from the SHARAD and MARSIS radar 

sounders, will provide new evidence to aid in 

distinguishing between the two most viable 

hypotheses of origin. 

MC-16 NW: A proposal to extend the mapping 

of MFF materials on THEMIS daytime IR base maps 

was selected for funding in March of 2007. Money 

for the new work has not yet been received, but here 

we present the main goals for the new mapping. MC16 NW (0° to 15°S lat., 180° to 202.5°E long.) was 

identified for mapping because it includes large 

exposures of material previously identified [2] as 

upper (u-MFF) or middle (m-MFF) members of MFF 

(Fig. 4). This quadrangle also has large exposures of

cratered highlands material, and we intend to devote 

particular attention to the contacts with these ancient 

materials in an effort to obtain better constraints on 

the likely emplacement of the MFF materials. 
Figure 3. HiRISE image of MFF material in MC-8 

SE. TRA_0001865_1905, 25 cm/p, center at 10.2°N, 

211.5°E, NASA/JPL/U of A. 

Figure 4. MC-16 NW quadrangle, on color-coded 

MOLA shaded relief base. u-MFF is upper member, 

m-MFF is middle member. 

MC-23 NW: Previous mapping was carried out 

in areas where the upper and middle members of 

MFF have been dominant. MC-23 NW (0° to 15°S 

lat., 135° to 157.5°E long.) includes large exposures 

of the lower member (l-MFF) of MFF (Fig. 5), the 

unit showing the largest degree of erosion of all MFF 

materials [2, 3]. Unusual deposits superposed on the 

central peak of Gale crater (5°S, 138°E) will be 

investigated as a possible outlier of MFF material. 

HiRISE data will once again be crucial in refining the 

interpretation of the heavily eroded MFF materials, 

which are apparently sufficiently competent to 

maintain m-scale blocks during erosion (Fig. 6). We 

will most likely proceed first with mapping of MC-23 

NW before starting work on MC-16 NW, in order to 

obtain initial interpretations of the lower member of 

Figure 5. MC-23 NW quadrangle, on color-coded 

MOLA shaded relief base. l-MFF is lower member. 

Figure 6. HiRISE image of the upwind nose of a 

yardang in MFF material just north of MC27-NW. 

TRA_000828_1805, 27 cm/p, center at 0.5°N, 

142.5°E, NASA/JPL/U of A. 

the MFF materials, which has not yet been 

investigated through detailed mapping utilizing the 

recent data sets. 

References: [1] Zimbelman, J.R. (2006) 

Planetary Geology Mappers Meeting Abstracts, 

Zimbelman_medusae_edited_final.pdf. [2] Scott 

D.H. and Tanaka K.L. (1986) USGS Map I-1802-A, 

1:15,000,000 scale. [3] Greeley R. and Guest J. 

(1987) USGS Map I-1802-B, 1:15,000,000 scale. 
Remote Geologic Mapping of Lunar Crater Volcanic Field, Nye County, Nevada: A Test for 

Planetary Geologic Reconnaissance. J.M. Dohm1

, K.L. Tanaka2, J.A. Skinner, Jr.2, L.A. Crumpler3, and 

T.M. Hare2

, 1Dept. of Hydrology and Water Resources, University of Arizona, Tucson, AZ, 85721 

jmd@hwr.arizona.edu; 2

Astrogeology Team, U. S. Geological Survey, Flagstaff, AZ 86001; 4New Mexico 

Museum of Natural History, Albuquerque, NM 

Introduction: Geologic mapping of Mars and 

other planetary bodies in the solar system has 

recorded their evolutionary histories. Often cited 

geologic maps of Mars [1], for example, portray 

an episodically dynamic planet with magmatic, 

tectonic, water/ice, and wind activity throughout 

its recorded history, a picture supported by recent 

missions. Information obtained from these and 

future missions will continue to improve upon past 

mapping efforts by adding additional layers of 

information for further comparative analyses 

(increased perspectives at varying scales, 

including enhancing the geologic detective work 

and ultimately resulting in the identification of 

prime targets for further in situ investigation [2]). 

This includes testing and revising existing 

working hypotheses, as well as generating new 

ideas that stimulate further scientific inquiry. 

Importantly, though the published geologic map 

information is often cited, the accuracy of the 

information and the utility of the mapping 

approaches that yield such information have not 

been field evaluated, except for the spatially limited 

reaches of Mars Sojourner (tens of meters) and the 

Mars Exploration Rovers, Opportunity and Spirit 

(tens of thousands of meters). For example, in 

question are the accuracies of unit assignments to 

outcrops, relative-age determinations of 

stratigraphic units and structures, and overall 

histories detailed by the mapping. While there have 

been numerous consistencies among existing 

geologic information (largely Viking-based) and 

diverse data sets recently acquired from the Mars 

Global Surveyor, Mars Odyssey, Mars Express, and 

Mars Reconnaissance spacecrafts (e.g., centers of 

tectonism correlate with MOLA-based topographic 

rises [3]), there has also been greater detail that has 

been unveiled, underappreciated during Viking-era 

mapping efforts (e.g., geologically recent and 

possibly currently active hydrologic activity [4,5]). 

The immense amount of new orbital- and field 

(lander and rover)-based information, which will 

add greater detail, and therefore ultimately improve 

upon the geologic maps and related interpretation, 

forms the basis for a new global mapping 

investigation of Mars currently underway [6, this 

meeting]. 

In order to optimize geologic mapping 

reconnaissance during this golden age of 

exploration and discovery, we have undertaken a 

timely investigation to assess remote planetary 

geologic mapping with grant support from the 

Mars Fundamental Research Program. We are 

using existing Mars-like terrestrial data sets 

(topography and visible and thermal infrared 

images at appropriate resolutions) to simulate 

Viking, Mars Global Surveyor, and Mars Odyssey 

data sets useful for performing remote mapping 

investigations of the test sites that can be 

evaluated through existing well-documented, 

field-based geologic information. Our team of 

planetary geologists is experienced in both 

terrestrial field mapping and remote mapping of 

planetary bodies including Mars. Our initial test 

focused on part of the San Francisco Volcanic 

Field of northern Arizona [7]. Below, we report 

on our second test. 

Geologic and Physiographic Setting of the 

Second Test Site: Part of the Lunar Crater 

Volcanic Field, Nye County, Nevada, was 

geologically mapped during the second test using 

an approach similar to that used for planetary 

bodies such as Mars [8,9], in order to test the 

feasibility and accuracy of planetary geologic 

mapping. The volcanic field (Figs. 1 and 2) 

provides a suitable test site, as many features have 

analogs on the Moon and Mars, vegetation is 

minimal, and satellite data is available that 

approximates the quality and resolution of those of 

Mars. The test site includes cinder cones, maars, 

and basalt flows of Tertiary (Oligocene and 

Miocene) and Quaternary age. Intervals of relative 

quiescence and erosion separate episodes of 

volcanism. Variations in morphology, degree of 

weathering, and superposition and cross-cutting 

relations among volcanic constructs, flows 

(volcanic, fluvial, and alluvial), drainages, and 

tectonic structures provide a basis for determining 

relative age. Basement structural control is 

indicated by vent (cones and craters) alignments 

and their associated lava flows emplaced along 

normal faults and fissures, as well as drainage 

patterns. Magmatic differentiation at depth, which 

is based on petrographic analysis of basalts and 

pyroclastics, produced subalkaline basalts, alkaliolivine basalts, and basanitoids, the latter of which 

comprise the youngest flows in the field [10]. 

1
Figure 1. Landsat TM false-color image mapping 

test area, part of the Lunar Crater Field, Nevada; 

~20 km wide; north at top. 

Figure 2. Color shaded-relief image of mapping 

test area; ~20 km wide; north at top.

Approach: We used image and topographic 

data that simulate those typically used to map the 

geology of Mars. Map units and stratigraphic 

relations are based primarily on morphology and 

superposition and cross-cutting relations, similar 

to the approach used for Mars [8,9]. Without prior 

knowledge of the volcanic field, each investigator 

mapped the test site separately and remotely. 

Summary: Quantifiable stratigraphic and 

structural mapping information for comparative 

analysis among the published field-based 

information and the results of each mapper 

included: (1) total number of polygons, (2) total 

length of a specific contact type (e.g., certain, 

uncertain), (3) total number of faults, (4) total fault 

length, (5) total number of polygons and total area 

of (a) stratigraphically young mantling materials, 

(b) stratigraphically young volcanic materials, and 

(c) stratigraphically old materials, (6) total area 

and number of features interpreted to be vent 

structures, and (7) fault-length density with 

respect to (i) mantling materials (e.g., alluvial and 

fluvial deposits), (ii) stratigraphically young 

volcanics, (iii) vent structures, and (iiii) 

stratigraphically old materials. Such an analysis 

provides us with useful information, including the 

reliability of identifying and interpreting map 

units, structure, and superposition relations among 

map units and structure. In addition, such 

information provides the basis for assessing the 

approaches and primary focuses of individual 

mappers. A significant variation in total number 

of mapped tectonic structures, for example, 

indicates that mapping emphasis and experience 

directly bears on mapping results (one mapper 

may focus on stratigraphy and resurfacing from 

fluvial activity while another on stratigraphy and 

tectonic deformation). Findings of this 

investigation, including consistencies and 

inconsistencies among the ground-truth and 

remote-based mapping information, lessons 

learned, and underlying implications on the 

overall utility of planetary geologic mapping, will 

be presented at the mappers’ meeting. 

References: [1] Scott, D.H., Tanaka, K.L. (1986) 

USGS Misc. Inv. Ser. Map, I-1802-A

(1:15,000,000). [2] Dohm J.M., et al. (2004) 

Planet. Space Sci. 2, 189-198. [3] Anderson, R.C., 

et al. (2001) J. Geophys. Res. 106, 20,563-20,585. 

[4] Ferris et al. (2002) Geophys. Res. Lett. 29, 

10.1029/2002GL014936. [5] Miyamoto, H., et al. 

(2004). J. Geophys. Res. 109, 

doi:10.1029/2003JE002234. [6] Tanaka et al. 

(2007) Abstracts, Seventh Intl. Conf. Mars. [7] 

Tanaka et al. (2004) Abstracts, PGM meeting. [8] 

Dohm, J.M., et al. (2001) USGS Map I-2650. [9] 

Tanaka, K.L., et al. (2005) USGS Map SIM-2888, 

scale 1:15,000,000. [10] Scott, D.H., Trask, N.J. 

(1971) USGS Prof. Pap. 599-1. 

2
GEOSCIENCE DATA VISUALIZATION SYSTEMS APPLIED TO PLANETARY GEOLOGICAL 

MAPPING. J. W. Head1, Prabhat2, A. S. Forsberg3, A. T. Basilevsky1,4, M. A. Ivanov1,4, J. L. Dickson1, C. I. Fassett1, J. S. 

Levy1, G. A. Morgan1, and P. Senthil Kumar1,5, 1Dept. of Geological Sciences, Brown University, Providence, RI 02912 

(james_head@brown.edu), 2Center for Computation and Visualization, Brown University, Providence, RI 02912, 3Dept. of Computer Science, Brown University, Providence, RI 02912, 4

Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, 

Moscow, Russia, 5National Geophysical Research Institute, Hyderabad 500007, India (senthilngri@yahoo.com).

Introduction and Background: Traditional methods of 

planetary geological mapping have relied on photographic 

hard copy and light-table tracing and mapping. In the last 

several decades this has given way to the availability and 

analysis of multiple digital data sets, and programs and platforms that permit the viewing and manipulation of multiple 

annotated layers of relevant information. This has revolutionized the ability to incorporate important new data into the 

planetary mapping process at all scales. 

We are currently investigating important new technological 

developments in computer visualization display in order to 

assess their importance and utility in planetary geological 

analysis and mapping [1,2]. At a fundamental level, there is a 

poor understanding of how computer visualization display 

qualities (e.g., level of immersion, stereoscopic vs. monoscopic viewing, field of view, large vs. small display size, etc.) 

influence performance on scientific analysis and geological 

mapping. We are exploring four different environments: 1) 

conventional desktops (DT), 2) semi-immersive Fishtank VR 

(FT) (i.e., a conventional desktop with head-tracked stereo and 

6DOF input), 3) tiled wall displays (TW), and 4) fully immersive virtual reality (IVR) (e.g., “Cave Automatic Virtual Environment”, or Cave system). While we have completed some 

formal studies demonstrating that fully immersive Cave environments are superior to desktop systems [e.g., 3], there is still 

much to learn and understand about how the varying degrees 

of immersive displays affect task performance. It is clear that 

the new availability of ultra-high-resolution datasets presents 

challenges in terms of handling and visualization. But due 

consideration must also be given to the final medium on which 

these phenomenal images are displayed. For example if a 

HiRISE image has 20Kx40K pixels, and the researcher is 

using a 1280x1024 desktop monitor to explore the image, the 

researcher will waste a lot of time in image zooming/panning 

to balance the analysis-driven need for both detail as well as 

context. If higher-resolution media, such as an IBM Bertha 

display 3840x2400 or a tiled wall with multiple projectors is 

used, we have found through four months of weekly meetings 

that they definitely improve the efficiency of analysis and 

mapping. 

ADVISER: System Description: We are developing 

ADVISER (ADvanced VIsualization for Solar system Exploration) [1,2] as a tool for taking planetary geologists virtually 

“into the field” in support of several scientific themes and are 

assessing its application to geological mapping. The project 

aims to create a field experience by integrating multiple data 

sources and presenting them as a unified environment to the 

scientist. Additionally, we are developing a virtual field kit, 

tailored to supporting research tasks dictated by scientific and 

mapping themes. Technically, ADVISER renders highresolution topographic datasets (8192x8192 samples) in stereo 

at interactive frame-rates (25+ frames-per-second). The system is based on a state-of-the-art terrain rendering system [4]. 

The system is highly interactive; for example, vertical exaggeration, lighting geometry and contour lines can be modified 

by the user in real time. High-resolution image data can be 

overlaid on the terrain and other data can be rendered in this 

context. A detailed description and case studies of ADVISER 

are available [1,2]. 

In our previous work we have exported many of the 

ADVISER functions to a desktop environment and made 

comparisons of the utility and productivity of the two media 

[1,2]. We are now beginning to explore the middle ground 

between Desktop displays (DT) and Cave displays (IVR) in 

terms of both 1) availability to a wide range of users, and 2) 

utility for scientific analysis and geological mapping. In our 

preliminary assessment we have found that the most effective 

capabilities in the middle range include the semi-immersive 

"fishtank display" (FT) and high-resolution tiled-wall displays 

(TW) and we are currently beginning to explore and evaluate 

this hardware spectrum "middle ground".

Application to Science Analysis and Mapping: 

ADVISER was originally designed for a Cave [1] because we 

believed the Cave’s large-scale stereo display was most appropriate for doing “virtual fieldwork”, but we are adapting its 

functionality to run on conventional desktop systems for two 

reasons: 1) to make it more generally accessible, and 2) to 

help us learn about the relative value of the information that 

can be gathered from both systems. While the Cave and desktop represent possibly two extreme ends of the VR spectrum, 

there are other intermediate systems, such as a Geowall (see 

http://www.geowall.org) which utilize a 1-wall stereo display. 

Such systems are less expensive than the Cave and are potentially better suited for wider deployment. 

The desktop system has a high-end nVidia graphics card; 

2GB RAM and a Pentium 4 processor. A video game controller (Logitech dual-action gamepad) is used to provide navigational input to the program. Our Cave system is an 8’x8’x8’ 

cube with four projection surfaces (three walls and the floor). 

Four linux machines (identical in performance to the desktop 

machine) provide data for the Cave. Users utilize a handheld 

3D tracked input device to navigate. Our 3D input device has 

a joystick and is simple to use. To navigate, the user simply 

points in the direction he/she wants to fly and pushes the joystick forward or backward to move relative to that direction. 

The user can push the joystick to the left and right to rotate 

his/her position in the virtual world. A collision detection 

algorithm is used to prevent the user from going underneath 

the surface. 

A 200 dpi IBM Bertha display at Brown enables us to conduct desktop-based exploration sessions and a 9-projector, 

active stereo, tiled-wall display with an effective resolution of 

2400x1800 is available next to the Cave in the Center for 

Computation and Visualization. In our past ADVISER geoscience research activities, we exclusively used the Cave and 

desktop environments for exploration. Recent commercial

demand for high-definition and high quality display has 

helped improve our capabilities in this area. While Caves in 

general provide for a better immersive experience, desktops 

are brighter and crisper than our current Cave, but their dis-
play area is relatively small. Our current tiled wall is a middle 

ground and has bright, crisp images on a large display surface. 

Fishtank VR is most similar to a regular desktop system, but 

adds head-tracked stereo viewing, and typically 3D tracked 

input devices. The effect is comparable to looking into a fishtank (its namesake) where objects appear in stereo, but the 

working volume is physically small, effectively producing a 

diorama-like "world in miniature." The exploration of this 

middle-ground has been shown to be very useful, particularly 

in terms of tiled displays for group discussion and analysis, 

and in geological mapping on Venus and on Mars.

Testing the Different Platforms: We are developing the 

ADVISER system primarily to assist graduate-level geoscience research, but its basic function of interactively navigating 3D terrains also serves as an educational tool. We have 

tested the desktop and Cave systems in Geological Sciences 5 

(Mars, Moon and the Earth), an introductory geosciences 

course at Brown University. Students learn about scientific 

study and analysis, how the Earth works, where the Earth fits 

into the solar system, the themes in the formation and evolution of planets, and how this information relates back to better 

understanding of the Earth. The course consists of lectures, 

reading assignments, homework, and laboratory exercises.

Students learn that geologists study the Earth and its evolution through field work and analysis of the geological record 

at various points on the Earth’s surface. Geologists then integrate these individual data points about the Earth’s surface by 

means of more synoptic analyses, often aided by the perspectives seen from image and topographic data acquired from 

Earth orbit. In contrast, planetary geoscientists commonly 

work in the reverse order, since the distances and times involved in acquiring data dictate that the first data from individual moons and planets comes from flybys and orbital 

spacecraft. Later, in some cases, more detail comes from the 

deployment of a few landers and rovers and, in the case of the 

Moon, human explorers. Consequently, there is a huge difference today between the local analysis of the Earth and the 

remote analysis of other planets. For example, while Earth 

geoscientists employ the 3D in-situ strategies described above 

in analyzing their data, most planetary geoscience analysis is 

done using either static or interactive 2D visualizations. 

To help do fieldwork in remote places, immersive virtual 

reality (IVR) systems let one or more people visit a computer 

generated world. Thanks in part to the video game industry 

and other new technologies, VR worlds can be explored interactively and contain amazing detail. The experience can be 

similar to an interactive stereo IMAX film, with wide field-ofview display and a strong sense of spatial relationships between visual features. Geoscientists use IVR to recreate and 

interact with distant places by using both remotely obtained 

data such as topography and images of the surface as well as 

simulated data (like atmospheric conditions varying with time) 

as a foundation of a visual world (Figs. 1-2). 

For three years, Geo 5 students have used ADVISER to 

complete a laboratory exercise about the geological history of 

Mars. In this exercise groups of three students first pose questions about the geology of Mars and subsequently “virtually” 

visit Mars’s surface using ADVISER. During their “visit” the 

students search for evidence pertaining to their questions. 

After three years of successfully running and customizing the 

lab, this past year we formally collected information from 

students about the educational experience [3]. In general students highly prefer a Cave-like system to a conventional desktop display for learning about geology and topography 

datasets. This preference is indicated by their ratings and 

choice of Cave as the preferred medium for future exploration. 

Both Cave and desktop media are preferred, however, to a 

standard 2D image-based investigation. Students report positively about the insights gained from the Lab exercise [4], an 

indication that 3D visualization is a valuable tool in teaching 

students about topographic and geologic datasets, and thus has 

a high potential in future applications to geological mapping.

Summary and Directions: We are striving for interdisciplinary collaborations that span the space science and computer science disciplines by 1) working very closely and iteratively with our computer science colleagues and collaborators, 

2) involving interdisciplinary science partners within space 

science and the NASA community (geosciences, atmospheres, 

multiple instruments, the international community), and 3) 

bringing the new technological developments to the attention 

of this entire spectrum. Planetary geological mapping is an 

important part of these applications. We have explored these 

capabilities and have tested them in classroom laboratory 

situations and in individual seminar sessions dedicated to geological mapping projects. We find that each of the platforms 

has unique capabilities and that science analysis and geological mapping are enhanced by their use. In the coming year we

are completing several test mapping cases on different planetary bodies and we will be tabulating and presenting the advantages and disadvantages of each of these media in scientific analysis and geological mapping. 

References: [1] Head, III, J.W. et al. (2005) Photogrammetric Engineering and Remote Sensing (PE&RS), Vol. 71:10. [2] Forsberg, A. 

et al. (2006) IEEE Computer Graphics and Applications, 26:4, pp. 46-

54. [3] Prabhat et al. (2007) Lunar and Planetary Science 38, #1297. 

[4] Hwa, L.M. et al. (2005) IEEE Transactions on Visualization and 

Computer Graphics, 11: 4, pp. 355-368. 

Fig. 1. Students explore Olympus Mons at a conventional desktop 

system. A videogame-like controller lets the students navigate around 

the volcano. A view from the top of the caldera is on the left, and a 

perspective view closer to the flanks of the volcano is on the right.

Fig. 2. Students fly through Valles Marineris in a Cave. A 3D wand 

input device lets the students interactively fly freely around the terrain 

in search of important geological features. 

Acknowledgments: The NASA Applied Information Systems Research Program and the NASA Planetary Geology and Geophysics 

Program are gratefully acknowledged.