The Gale Crater Mound: A Candidate Landing Site for the 2009 Mars Science Laboratory

The Gale Crater Mound: A Candidate Landing Site for the 2009 Mars Science Laboratory Jim Bell1, Ken Edgett2, Scott Rowland3, Mike Malin2 Representing the MSL Mastcam/MAHLI/MARDI Science Team 1Cornell U.; 2Malin Space Science Systems; 3U. Hawaii First MSL Landing Site Workshop May 31, 2006

Outline • Scientific Justification: Why MSL to Gale? • Site information • Proposed Ellipse and Traverse Options • EDL and Trafficability • Summary

Gale Crater • Located at 5°S, 137.5°E (222.5°W) in the northeast Aeolis quadrangle, near the highlands/lowlands boundary • 140-172 km diameter, named after the Australian eclipse & transit astronomer Walter F. Gale (1865-1945) • MOLA Heights (Parker) • Plains/Plateau: -1.1 to 0.0 km • Floor: -4.5 km; Mound: +0.3 km 135°E 140°E 5°S

Science Case / MSL Relevance • Key previous studies: • Viking/Mariner imaging: Scott et al. (1978); Greeley & Guest (1987); Grin & Cabrol (1997); Kuzmin et al. (1998);Cabrol et al. (1999) • and MGS MOC, MOLA: Malin & Edgett (2000, 2001); Edgett & Malin (2001) • and MGS TES; ODY THEMIS: Pelkey & Jakosky (2002); Pelkey et al. (2004) • Complementary talk here by N. Bridges

Gale Crater Gale Crater Highest point exceeds rim by ~1 km 40-50 km wide central mound Highest point exceeds rim by ~1 km

Gale Crater Central Mound • Indurated, layered, possibly rocky materials partially covered by dust based on physiography, albedo, and color information • Compositional information ambiguous: significant dust & sand cover reduces spectral contrast in currently-available data • Distinct layering of outcrops suggests a sedimentary origin, although an igneous origin cannot be ruled out • Angular unconformities, filled and exhumed channels, & other buried and exhumed erosional surfaces record significant changes in the depositional and erosional regime of this region regardless of the rock type • Interpretation: Apparently, Gale and perhaps much of the surrounding region was completely buried and exhumed, at least once

500 m Unconformity; buried erosional surface (MOC M03-01521)

Evidence for channels cut into the layered rock, then subsequently buried and re-exposed (inverted) (MOC M03-01521)

Perspective view of exhumed channel 200 m

Science Case / MSL Relevance • Gale crater has had a complex history of erosion and deposition (likely sedimentary, but possibly volcanic?) • Mound is a remnant of a once-larger deposit that may have filled the entire crater (and more) • The mound consists of hundreds of thin (< 10 m) beds in distinct units of similar thickness and material properties • Partially-exhumed craters (erosional unconformities) in some units indicate significant time between some depositional epochs • Evidence for channels cut into the layered rock, then subsequently buried and re-exposed (inverted) • Evidence for deposition of younger, massive units of light-toned materials at the top of the sequence

One Gale history model... (Edgett & Malin, 2000)

Gale captures the essence of the larger, global picture: • The mound is a layered, cratered, channeled volume. • The story recorded there is rich and complex. • The crater itself was filled, buried, then exhumed (at least once, maybe more). Chinle Triassic Moenkopi) Kaibab Ls Permian Toroweap Coconino Ss Hermit Sh Muav Ls Cambrian Bright Angle Sh Tapeats Ss Edgett & Malin, 2001)

Proposed 20 km Ellipse • MOC mosaic, >30 images, 2/06 (Ken Edgett) • Ellipse is on a fan of material transported through a valley that cuts/runs down Gale’s wall in the northwest quadrant of the crater N

THEMIS-VIS mosaic of all Gale images as of Oct. 2005 • Initial version, for THEMIS science team • In false color where there is VIS color coverage • Ellipse is near 4.6°S, 222.65°W (137.35°E) ellipse near 4.6°S, 22.8°W 20 km Bell et al., 2005

5 km 5 km

THEMIS-VIS V11330001 (7/4/04) • 18 m/pixel • 16:55 LTST • Depositional fan fills about half the ellipse • Relatively smooth unit • Fan materials were transported through the valley in crater wall (upper left) 5 km

EDL and Trafficability/Traverse • Edgett considered all possible places for landing ellipse in Gale Crater; Northwest fan ellipse seems like best location • Landing might be challenging, but potential landing and traversing hazards appear (initially) no more problematic than at the MER-A site in Gusev Crater... • The fan is not the primary scientific goal, but appears to be a safe and interesting place to land • Fan could be a possible highlands “grab bag” site (also sampling ancient pre-Gale crust?) for initial scientific investigation; Possible lava on Gale floor, as well. • Trafficable routes into the mound identified in MOC images • But Gale is not JADPCL: • A proposed traverse from the ellipse to the mound would utilize the “Go-to” capabilities of MSL to access to some of the diverse, sedimentary rock section in the mound.

Possible Traverse Goal: “Grand Canyon” of the Gale Mound; 500-1000 m of exposed layered sedimentary rock, cross-section of lowest element of Gale stratigraphy; Canyon ~1 to 1.5 km wide. 3 km

Summary • Gale crater and its central mound of layered sedimentary rock represent an important enigma in our present understanding of Mars • Are the layers sedimentary? If so, how were they transported there? (wind? water?) Why is the central mound so “rhythmically” layered, and higher than the rim/plateau? • Outstanding place to test habitability of early Mars • We believe that the site meets the EDL, Trafficability, and Planetary Protection requirements of the MSL Project, although the most interesting geological areas will require a drive from a nearby landing site.

EXTRAS

Gale Crater topography • Transverse Mercator contour topo map from the MOLA 128ppd gridded data. • (Tim Parker)

The Gale Crater Mound: A Candidate Landing Site for the 2009 Mars Science Laboratory