Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Gully Analysis by the 2009 Mars Science Laboratory W. E. Dietrich, J. Schieber, B. Hallet, K. S. Edgett and M. C. Malin

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Gullies are located at Middle and Polar Latitudes and Might be Key Sites for Recent Water and Habitability Science

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June There’s a variety of morphologic expressions… ~3 km across, E , 41.8°S, 158.0°W

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June …more examples…

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June …and more examples.. ~ 3 km wide, S , 38.0°S, 167.2°W

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Banked channels Multiple flow events Not cratered …and another…

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June They Seem to Be Young Superimposed craters are uncommon. Some have dark floors; do not retain dust. Some cut or superpose eolian bedforms. Not all are young; some do have superposed craters or eolian bedforms; some have features cut by cracks or faults.

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June How Do They Form? HypothesisReferences H 2 O groundwater Malin and Edgett (2000) Mellon and Phillips (2001) Gilmore and Phillips (2002) Heldmann and Mellon (2004) H 2 O ground ice Costard et al. (2001) H 2 O ice pack, snowmelt, atmospheric precipitation Lee et al. (2001) Christensen (2003) Balme et al. (2006) CO 2 release Musselwhite et al. (2001) Hoffman (2002) No volatile is involved; dry granular flow Treiman (2003) Shinbrot et al. (2004)

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Malin/Edgett Still Favor Groundwater Hypothesis Bolstered by recent excellent evidence that fluids emerged from beneath the ground, rather than by melting of snow. Key examples include those at which gullies emerge at a fault, suggesting groundwater percolation along fault (image on far right).

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Can MSL Go to a Gully Site? D’oh! We recognize that Planetary Protection likely precludes landing at a gully site, but we feel it is important to have discussed this topic at the 1st Landing Site Workshop. It is critical to understand that, while MSL theoretically opens up a larger portion of Mars for landing than previous US surface missions, the design still precludes visiting certain key or critical targets.

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June The Search for Places That a 20 km Diameter Landing Ellipse Will Fit We examined every gully location known from MOC images, acquired through 30 May 2006, in both hemispheres to 60° latitude. MSL obviously can’t land on gullied slopes. MSL likely can’t drive down into craters with gullied walls. So we sought craters with gullies that are large enough to put a 20 km diameter ellipse on the crater floor, snuggled up as close as possible to gully apron material. Most craters with gullies are too small for a 20 km ellipse. Most craters large enough for 20 km ellipse do not have gullies. We found only 3 viable locations, with two craters at one of the three locations

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Candidate 1 & 2: South Terra Cimmeria 35.8°S, 204.4°W 35.2°S, 203.9°W elevations are ~ +0.4 km White boxes show existing MGS MOC coverage to 30 May 2006.

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Gullies in Candidate 1 Crater

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Floor of Candidate 1 Crater

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Candidate 3: Hale Crater (floor too rugged) White boxes show existing MGS MOC coverage to May 2006.

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Many, Many Terrific Gullies in Hale (example)

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June And in Hale’s Central Peak Area (example)

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June But Hale’s Floor is Pretty Rough

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Candidate 4: Wirtz Crater (probably the best) White boxes show existing MGS MOC coverage to 15 May 2006.

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Example Gullies on NW Wirtz Wall

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Example Gullies on SE Wirtz Wall

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Example of Wirtz Crater Floor

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Summary candidatename approx. lat/lonelevationcomments 1none36°S, 204°W+0.4 km ellipse just fits in crater; pretty good candidate 2none35°S, 204°W+0.4 km ellipse barely fits in crater; not much MOC or THEMIS coverage 3Hale36°S, 37°W–2.4 km many great gullies; floor is likely way too rugged 4Wirtz49°S, 26°W–0.6 km probably the best candidate; several places that an ellipse will fit; floor (thus far) doesn’t look too dangerous.

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June Recommendation Consider sending MSL to a gully site. Unfortunately, there are very few gully sites accessible with a 20 km landing ellipse. Recognizing that going to gullies may not be possible, for Planetary Protection reasons, means there is something wrong with the system— how can NASA have not designed a mission (and its feed-forwardness) that could go to the only known class of sites on Mars where liquid water may have been present in relatively recent times? Mmmmm, gullies!