1. Measurability – MSL payload instruments Based on definitive nature of the biosignature and its measurability by the MSL payload o diagnostic organic molecules o biogenic gases o organism morphologies (cells, body fossils, casts) o biofabrics (including microbial mats) o isotopic signatures o evidence of biomineralization and bioalteration o spatial patterns in chemistry Precedence is given to organic matter (OM) detection, though, where it occurs, there is a high probability that other biosignatures may also be present. from Table 1, Summons et al., submitted, Astrobiology Biosignatures Detection - depends on formation, concentration, preservation, and measurability

2. Formation - directly related to past habitability assuming past life existed on Mars. Water, energy sources (e.g., chemical gradients), nutrient supply, protection from extreme conditions (i.e., radiation and high heat) Concentration - Depositional environments that favored sedimentation of OM via retention and hydrodynamic concentration Same environments favor habitability Possibility of closely linked in situ biosignature generation and burial Preservation - Concentrations of sedimentary minerals that protect OM from ionizing radiation and chemical oxidation (e.g., phyllosilicates) Summons et al., submitted, Astrobiology Biosignatures Detection - depends on formation, concentration, preservation, and measurability

3. Potential early Mars sedimentary environments that would support organic C formation, concentration, and preservation Early Mars Environment Support for: Biotic (& abiotic) C org formationC org ConcentrationC org Preservation Aeolian sedimentslow Regional groundwater pore system low Alluvial Fanlow Fluvial channellow Fluvial floodplainlow-mod (low)lowmod Deltaic sedimentshigh (low)high Lacustrine (perennial)high (low)high Lacustrine evaporitic (Cl - )med (low)highhigh-very high Lacustrine evaporitic (SO 4 = )low (low)highhigh-very high from Table 3 of Summons et al., submitted, Astrobiology

4. Potential early Mars volcanic and hydrothermal environments that would support organic C formation, concentration, and preservation Early Mars Specific Cases Support for: Biotic (& abiotic) C org formationC org ConcentrationC org Preservation Pyroclastics – aqueous alteration (surface and subsurface) low mod-high Volcanic flows- aqueous altered surface low low-mod Volcanic flows- aqueous altered subsurface modlowlow-mod Volcanic flows- hydrothermal altered surface mod (low)lowmod Hydrothermal subsurface (<100 °C) modmod-lowmod Hydrothermal surface (<100 °C) high (low)mod-highmod Mafic and ultramafic subsurface (<100 °C) high (low)mod-highmod from Table 4 of Summons et al., submitted, Astrobiology

5. Habitability/Biosignature Preservation questions for MSL 1.Cyclic deposits. If there is any repeat patterning to the horizontally layered basin floor deposits or fan deposits and they contain clay-rich layers or salts, then perhaps there may be an opportunity for MSL to test for an ecological record, like that suggested for Gale. Alternatively, variations in lithofacies laterally and with respect to the fan system may be useful as a framework for investigating paleo-ecosystems. 2.Horizontally layered deposits on the basin floor. If these are lacustrine and fine grained, then they are an optimal place to search for both habitat features and preserved biosignatures. A stratigraphic framework of a lacustrine/deltaic system would be ideal for characterizing habitability and detecting biosignatures but it is not required. 3.Delta to basin correlation. If organic matter or biosignatures are present in deposits, can we use these to help correlate delta to basin strata?

6. Habitability/Biosignature Preservation questions for MSL 4.Most ancient fluvial deposits. Are there clay or salt deposits associated with the more ancient fluvial deposits underlying the horizontal layered units in the basin floor? If clay layers or salts are present, is there organic matter or are biosignatures present in them? Is the mineralogy or clast composition significantly different than younger deposits, differences that speak to different habitability? 5.Holden sediments. Do the sedimentary rocks in the Holden ejecta suggest differences in the habitability conditions of the Holden deposit? Are there biosignatures present? Do these rocks show alteration associated with the impact event (hydrothermal) or later aqueous alteration?

7. 6.Clays in Strata: Do the light toned layered units at the base of the scarp and in horizontal layered outcrops on the basin floor have clay-bearing units within them (i.e., siltstones/mudstones)? Or is the clay distributed within a more poorly sorted sediment? Milliken CRISM spectral parameters indicate that both swelling and non-swelling (mixed-layer) clay minerals may be present at Eberswalde – Can these different types of clay minerals be related to specific localities or deposits? Do they correlate to organic matter character and biosignatures? 7.Missing Salts. Is there a suite of salts present in various units? Are they associated with fine-grained deposits or clay minerals? Does the salt mineralogy tell us about evolution of the water chemistry of the lake during water level fluctuations? Has the salt been redistributed by post-depositional processes? Does the mineralogy of salts and clay correlate to organic matter character? 6.Carbon Cycle. Are their traces of carbonates present? If so, are there any isotopic, mineralogic, or other measurable variations over time (based on stratal relationships)? If so, do they relate to depositional changes? How do these values compare to atmospheric CO 2 and CH 4 C-isotopic compositions? 7.Outcropping characteristics for biosignature recovery. Does the outcropping of the basin floor layered rocks versus the light-toned layered rocks at the fan scarp offer any advantages in terms of more recent erosional exposure or protection from radiation. For example, partially shaded exposures or exposures recently exposed (e.g., mass wasting) may exhibit better preservation. Habitability/Biosignature Preservation questions for MSL: