1. SEDIMENTARY ROCKS AND METHANE – SOUTHWEST ARABIA TERRA Carlton Allen and Dorothy Oehler NASA Johnson Space Center Houston, TX Elizabeth Venechuk Scripps College Claremont, CA

2. The MSL Scientific Objectives for exploring a site are to: 1) assess the biological potential, 2) characterize the geology and geochemistry, and 3) investigate planetary processes of relevance to past and present habitability. On Earth sedimentary rocks reveal the history of past environments and contain the physical, chemical, and isotopic biomarkers that provide evidence past life.

3. Edgett, 2005 800+ m of layered sedimentary rock in SW Arabia Terra and Sinus Meridiani

4. 0 10 20 0350 340 10 30 Proposed MSL landing sites

5. 0 10 20 0350 340 10 30 Our proposed landing site

6. Lat 6 N Long 356 Edgett, 2005

7. 55 km diameter 750 m deep Edgett, 2005

8. Crater embedded within, and partially exhumed from, sedimentary rock Edgett, 2005

9. 750 m vertical section 1 degree slope Edgett, 2005

10. Site 1 5.84 N 355.36 -1,696 m Explore the deepest sediments and the crater floor deposits Edgett, 2005

11. MOC M11-03134 1 km Eroded layers on crater floor

12. MOC S06-01229 1 km Eroded layers on crater floor

13. Site 2 6.59 N 355.08 -1,246 m Explore deposits on the crater rim and the upper sediments Edgett, 2005

14. Eroded layers in sediments 1 km MOC S06-01229

15. Eroded layers in sediments 1 km MOC S06-01229

16. Methane has been detected in the martian atmosphere at a concentration of ~ 10 ppb. The lifetime of methane against decomposition by solar radiation is around 300 years, strongly suggesting that methane is currently being released to the atmosphere.

17. By analogy to Earth, possible methane sources on Mars include: active volcanism or hot springs, ongoing serpentinization of basalt, thermally-matured sedimentary organics, and living microbes. The discovery of any one of these sources would revolutionize our understanding of Mars !

18. CH4

19. S A M: Detect and quantify methane << 1 ppb Detect and quantify heavier hydrocarbons ~ 1 ppb Determine carbon isotope ratios

20. Confirm or refute methane detection Address temporal and spatial variations in methane abundance Address the methane source – on Earth correlation of the ratio of methane / (ethane + propane + butane) with  13C distinguishes between microbial sources and abiogenic sources. (Allen, M. et al, 2005)

21. Enhanced methane concentrations have been measured by the Planetary Fourier Spectrometer on Mars Express.

22. These concentrations were reported above Arabia Terra, Elysium Planum, and Arcadia-Memnonia. Potential source areas ? Higher concentrations to analyze. Elysium Arabia Arcadia

23. MSL landing in SW Arabia Terra can address the past biological potential, geology, and geochemistry within 750 m of sedimentary rock and improve analyses addressing the detection, variations, and microbial vs. abiogenic source of gases currently being released from the martian crust.