The search for Hesperian organic matter on Mars: Pyrolysis studies of sediments rich in sulfur and iron
File(s)
Published version
Author(s)
Lewis, JMT
Najorka, J
Watson, JS
Sephton, MA
Type
Journal Article
Abstract
Jarosite on Mars is of significant geological and astrobiological interest as it forms in acidic aqueous conditions that are potentially habitable for acidophilic organisms. Jarosite can provide environmental context and may host organic matter. The most common analytical technique used to search for organic molecules on the surface of Mars is pyrolysis. However, thermal decomposition of jarosite produces oxygen, which degrades organic signals. At pH values greater than 3 and high water to rock ratios jarosite has a close association with goethite. Hematite can form by dehydration of goethite or directly from jarosite under certain aqueous conditions. Goethite and hematite are significantly more amenable for pyrolysis experiments searching for organic matter than jarosite. Analysis of the mineralogy and organic chemistry of samples from a natural acidic stream revealed a diverse response for organic compounds during pyrolysis of goethite-rich layers but a poor response for jarosite-rich or mixed jarosite-goethite units. Goethite units that are associated with jarosite but do not contain jarosite themselves should be targeted for organic detection pyrolysis experiments on Mars. These findings are extremely timely as future exploration targets for Mars Science Laboratory include Hematite Ridge, which may have formed from goethite precursors.
Date Issued
2018-04-01
Date Acceptance
2017-08-15
Citation
Astrobiology, 2018, 18 (4), pp.454-464
ISSN
1531-1074
Publisher
Mary Ann Liebert
Start Page
454
End Page
464
Journal / Book Title
Astrobiology
Volume
18
Issue
4
Copyright Statement
© James M.T. Lewis et al., 2018; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.
License URL
Sponsor
Science and Technology Facilities Council (STFC)
Science and Technology Facilities Council (STFC)
Grant Number
ST/J001260/1
ST/N000560/1
Subjects
Science & Technology
Physical Sciences
Life Sciences & Biomedicine
Astronomy & Astrophysics
Biology
Geosciences, Multidisciplinary
Life Sciences & Biomedicine - Other Topics
Geology
Mars
Pyrolysis
Jarosite
Goethite
Hematite
Biosignatures
SOLID-SOLUTION SERIES
GALE CRATER
RIO-TINTO
PRESERVATION
JAROSITE
SULFATE
SITE
LIFE
MOLECULES
CHEMISTRY
0201 Astronomical And Space Sciences
0402 Geochemistry
0403 Geology
Publication Status
Published
Date Publish Online
2018-01-03