1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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