Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June 2006 1 Gully...

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Mars Science Laboratory 1st Landing Site WorkshopPasadena, CA — 31 May – 2 June 2006

Gully Analysis by the 2009 Mars Science Laboratory

W. E. Dietrich, J. Schieber, B. Hallet,

K. S. Edgett and M. C. Malin

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Gullies are located at Middle and Polar Latitudes and Might be Key Sites for Recent

Water and Habitability Science

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There’s a variety of morphologic expressions…

~3 km across, E16-00043, 41.8°S, 158.0°W

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…more examples…

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…and more examples..

~ 3 km wide, S10-00964, 38.0°S, 167.2°W

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• Banked channels• Multiple flow events• Not cratered

…and another…

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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.

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How Do They Form?

Hypothesis References

H2O groundwater

Malin and Edgett (2000)

Mellon and Phillips (2001)

Gilmore and Phillips (2002)

Heldmann and Mellon (2004)

H2O ground ice Costard et al. (2001)

H2O ice pack, snowmelt, atmospheric precipitation

Lee et al. (2001)

Christensen (2003)

Balme et al. (2006)

CO2 release Musselwhite et al. (2001)

Hoffman (2002)

No volatile is involved; dry granular flow

Treiman (2003)

Shinbrot et al. (2004)

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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).

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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.

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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

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Candidate 1 & 2: South Terra Cimmeria

35.8°S, 204.4°W

35.2°S, 203.9°W

elevations are ~ +0.4 kmWhite boxes show existing MGS MOC coverage to 30 May 2006.

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Gullies in Candidate 1 Crater

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Floor of Candidate 1 Crater

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Candidate 3: Hale Crater (floor too rugged)White boxes show existing MGS MOC coverage to May 2006.

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Many, Many Terrific Gullies in Hale (example)

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And in Hale’s Central Peak Area (example)

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But Hale’s Floor is Pretty Rough

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Candidate 4: Wirtz Crater (probably the best)White boxes show existing MGS MOC coverage to 15 May 2006.

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Example Gullies on NW Wirtz Wall

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Example Gullies on SE Wirtz Wall

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Example of Wirtz Crater Floor

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Summary

candidate name approx. lat/lon elevation comments

1 none 36°S, 204°W +0.4 kmellipse just fits in crater; pretty good candidate

2 none 35°S, 204°W +0.4 kmellipse barely fits in crater; not much MOC or THEMIS coverage

3 Hale 36°S, 37°W –2.4 kmmany great gullies; floor is likely way too rugged

4 Wirtz 49°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.

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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!

Mars Science Laboratory 1st Landing Site Workshop Pasadena, CA — 31 May – 2 June 2006 1 Gully...

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