Mawrth Vallis LSWG Hab/BiosigPres, Jen Eigenbrode/ NASA GSFC Mawrth Vallis – Considerations for Habitability and Biosignature Preservation July 28, 2010 SWOG Mawrth Vallis LSWG Hab/BiosigPres, Jen Eigenbrode/ NASA GSFC

Support for Biosignature FCP Evaluation of support for biosignature formation, concentration, and preservation (FCP) for impact-related rocks Impacts provide heat that can linger for 1000’s to 10,000’s years (more?) Water, chemical and thermal energy flux Support for Biosignature FCP Post-impact Strongly support for habitability, organic matter formation, clay mineral formation, and mineral precipitates that encourage biosignature preservation. impact-generated hydrothermal system (surface and subsurface) high Strong support for habitability, especially if chemical and thermal gradients are established. FCP are all supported and layered deposits would provide a stratigraphic framework for investigations. Pre-Impact Rocks (composition will influence post-impact habitability) impact-generated crater lake (could be a hot lake, Newsom, submitted; could freeze over) IMPACT high July 28, 2010 SWOG Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode

Support for Biosignature FCP Evaluation of support for biosignature formation, concentration, and preservation (FCP) for impact-related rocks Impacts provide heat that can linger for 1000’s to 10,000’s years (more?) Water, chemical and thermal energy flux Support for Biosignature FCP Post-impact impact-generated hydrothermal system (surface and subsurface) high impact-generated crater lake high Pre-Impact Rocks IMPACT impact-related fluvial environments low impact-independent sediments accumulated in catchment Dependent on depositional environment ? impact-independent diagenetic conditions (e.g. pedogenesis) low July 28, 2010 SWOG Mawrth Vallis LSWG SOWG Hab/BiosigPres, J. Eigenbrode/ NASA GSFC

Support for Biosignature FCP Evaluation of support for biosignature formation, concentration, and preservation (FCP) for impact-related rocks Impacts provide heat that can linger for 1000’s to 10,000’s years (more?) Water, chemical and thermal energy flux Do we have this at Mawrth in rover range? Support for Biosignature FCP Post-impact impact-generated hydrothermal system (surface and subsurface) high impact-generated crater lake high Pre-Impact Rocks IMPACT impact-related fluvial environments low impact-independent sediments accumulated in catchment Dependent on depositional environment ? impact-independent diagenetic conditions (e.g. pedogenesis) low Was this a significant process at Mawrth in the rover area? July 28, 2010 SWOG Mawrth Vallis LSWG SOWG Hab/BiosigPres, J. Eigenbrode/ NASA GSFC

Evaluation of support for biosignature formation, concentration, and preservation (FCP) for impact-related rocks Impact craters provide access to bedrock Post-impact Sedimentary record that supports biosignature FCP Biosignatures in sedimentary rock that are excavated from or proximal to impact craters are susceptible to alteration/destruction by: impact erosion, subsequent oxidation and weathering shock metamorphism* hydrothermal alteration* redistribution* overprinting by later life* Context for biosignatures in the pre-impact record is at best complicated and at worst lost. Framework for understanding past habitability at multiple scales may be lost. Difficulty in reconstructing depositional environment. Dependence on nature of impact: large vs. small, rock vs. ice, gassy?, wet, unconsolidated or lithified substrate? …smaller, recent craters are more likely to be less disruptive and may maintain the preservation window. optimism IMPACT Pre-Impact Rocks * As in Haughton Crater; Parnell, Lee, Osinski, Cockell, 2005, Metoeritics & Planetary Science July 28, 2010 SWOG Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode

Evaluation of support for biosignature formation, concentration, and preservation (FCP) for impact-related rocks Impact craters provide access to bedrock Post-impact Sedimentary record that supports biosignature FCP Biosignatures in sedimentary rock that are excavated from or proximal to impact craters are susceptible to alteration/destruction by: impact erosion, subsequent oxidation and weathering shock metamorphism* hydrothermal alteration* redistribution* overprinting by later life* Context for biosignatures in the pre-impact record is at best complicated and at worst lost. Framework for understanding past habitability at multiple scales may be lost. Difficulty in reconstructing depositional environment. Dependence on nature of impact: large vs. small, rock vs. ice, gassy?, wet, unconsolidated or lithified substrate? …smaller, recent craters are more likely to be less disruptive and may maintain the preservation window. optimism IMPACT Pre-Impact Rocks With respect to Mawrth… Searching for habitability features and biosignatures from the time of rock deposition is an option for a Mawrth MSL investigation, but risky given so many uncertainties * As in Haughton Crater; Parnell, Lee, Osinski, Cockell, 2005, Metoeritics & Planetary Science July 28, 2010 SWOG Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode

Evaluation of support for biosignature formation, concentration, and preservation (FCP) for impact-related rocks Impact craters provide access to bedrock Post-impact Sedimentary record that supports biosignature FCP Biosignatures in sedimentary rock that are excavated from or proximal to impact craters are susceptible to alteration/destruction by: impact erosion, subsequent oxidation and weathering shock metamorphism hydrothermal alteration redistribution overprinting by later life Context for biosignatures in the pre-impact record is at best complicated and at worst lost. Framework for understanding past habitability at multiple scales may be lost. Difficulty in reconstructing depositional environment. optimism IMPACT Pre-Impact Rocks Mafic rock/ lava (biosignature FCP unlikely) No pre-impact biosignatures to preserve Subsurface viable life Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode

Terrestrial drill hole analogy for martian impact craters with regards to subsurface viable life Depths that viable microbial life has been observed on Earth Depths of craters observed on Earth Cockell and Barlow, 2002 Many authors suggest possible detection of biosignatures for subsurface life Horneck et al. (2001) - Bacillus subtilis spores could survive a simulated impact (32 GPa, 250◦C) July 28, 2010 SWOG Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode

Terrestrial drill hole analogy for martian impact craters with regards to subsurface viable life Depths that viable microbial life has been observed on Earth Depths of craters observed on Earth … perhaps re-establishment of subsurface life in new surface environment important… i.e. a cycling of microbial niches driven by impactors… how might MSL detect post-impactor niches? What framework can we use to base MSL observations? ex. spatial correlation between textures and elemental ratios - Mineral and organic geothermometry Cockell and Barlow, 2002 Many authors suggest possible detection of biosignatures for subsurface life Horneck et al. (2001) - Bacillus subtilis spores could survive a simulated impact (32 GPa, 250◦C) July 28, 2010 SWOG Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode

Mineralogy on Biosignature Preservation Ferric iron oxides mixed directly with organic matter will react over geological time under most conditions (cryosphere may be an exception). High temperature pyrolysis under helium would ensure organic matter oxidation. Ferrous iron oxides may not have the same consequence. Jarosite formed under acidic conditions and in the presence of ferric iron oxides are poor conditions for organic matter preservation over geological time scales. Notably, other biosignatures may be preserved in the above sediments. Ca-sulfate and phyllosilicates are better agents for enhancing preservation by protecting organic matter and other biosignatures from oxidation and weathering. All phyllosilicates provide high surface area for organic matter adsorption and can compact to seal the sediments from destructive processes. However, smectites can also absorb small organic molecules, water, and cations into interlayers, and they can form weak chemical bonds with polar organics, water, and cations. This physiochemical relationship make smectites ideal minerals to assist in organic biosignature preservation. April 3, 2019 Mawrth Vallis LSWG Hab/BiosigPres Eigenbrode