Biosignature Preservation Potential in a Playa Evaporite Mars Analog Field Site: Impacts of Diagenesis and Implications for Mars Exploration
Abstract
Assessing biosignature preservation potential (BPP) in ancient habitable environments on Mars is a top NASA priority. We address this goal through a Mars analog field study of Miocene-Pliocene evaporites of the Verde Formation (central Arizona). We assessed the effects of diagenesis on BPP, integrating outcrop-scale observations with six lab analyses: thin-section petrography; X-ray diffraction; Raman spectroscopy; Total Organic Carbon (TOC); electron probe microanalysis (EPMA); and VNIR reflectance spectroscopy. We recognized five facies and their diagenetic pathways. Two facies included mudstones, which contain clusters of displacive growth gypsum (DGG). Early DGG was altered during diagenesis by dissolution forming crystal cavities and later undergoing recrystallization, cation substitution, and sulfate dehydration. Another facies was identified by lenticular beds dominated by halite and late diagenetic thenardite (Na2SO4). These pods are overlain by a sequence of interbedded grey and red mudstones which record cyclic oxidation and Fe-oxide cementation. During the Pleistocene, a lacustrine environment developed, accompanied by magnesite cementation of playa mudstones. TOC analyses were used as a proxy for inferring the BPP in each facies. The highest BPP was associated with both red and grey mudstone facies. This study provides a taphonomic framework for playa environments on Earth that record the impacts of diagenesis on BPP, with potential applications to in situ biosignature searches and Mars sample return.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.P31F3756S
- Keywords:
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- 0406 Astrobiology and extraterrestrial materials;
- BIOGEOSCIENCESDE: 6225 Mars;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5419 Hydrology and fluvial processes;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS