TY - JOUR
T1 - Biosignature preservation potential in playa evaporites
T2 - Impacts of diagenesis and implications for mars exploration
AU - Shkolyar, Svetlana
AU - Farmer, Jack
N1 - Funding Information:
We gratefully acknowledge the use of the Raman facility within ASU’s LeRoy Eyring Center for Solid State Science through the help of Emmanuel Soignard. Brian St. Clair, Natalya Zolotova, Gwyneth Gordon, and especially Candace Ashley (ASU) are thanked for help with TOC measurements. Philip Gopon (UW-Madison) is thanked for EPMA sample preparation and useful insights on EPMA methods. Axel Whittmann (ASU) is thanked for help with EPMA measurements. Christopher Haberle (ASU) is thanked for help with VNIR spectroscopy analyses. ASU’s NASA’s Mars Program and the NASA-SETI Astrobiology Institute are acknowledged for financial support. S.S. thanks ASU’s Graduate and Professional Student Association (GPSA) for conference travel and support of analytical equipment through ASU’s Graduate Education Graduate Research and Support Program (GRSP). The Postdoctoral Fellowship at Carnegie Institution for Science is acknowledged for support. Thanks are also given to two anonymous reviewers for their encouragement and reviews that improved this manuscript.
Publisher Copyright:
© Copyright 2018, Mary Ann Liebert, Inc., publishers.
PY - 2018/11
Y1 - 2018/11
N2 - Assessing biosignature preservation potential (BPP) in ancient habitable environments on Mars is a top NASA priority. We address this goal through the 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 visible to near-infrared (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 underwent 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 gray 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 gray 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 Mars sample return (MSR) missions.
AB - Assessing biosignature preservation potential (BPP) in ancient habitable environments on Mars is a top NASA priority. We address this goal through the 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 visible to near-infrared (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 underwent 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 gray 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 gray 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 Mars sample return (MSR) missions.
KW - Biosignature preservation potential (BPP)
KW - Diagenesis
KW - Evaporites
KW - Kerogen
KW - Mars sample return (MSR)
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U2 - 10.1089/ast.2018.1849
DO - 10.1089/ast.2018.1849
M3 - Article
C2 - 30124326
AN - SCOPUS:85055900072
SN - 1531-1074
VL - 18
SP - 1460
EP - 1478
JO - Astrobiology
JF - Astrobiology
IS - 11
ER -