Abstract
The ability to detect and map lipids, including potential lipid biomarkers, within a sedimentary matrix using mass spectrometry (MS) imaging may be critical to determine whether potential lipids detected in samples returned from Mars are indigenous to Mars or are contaminants. Here, we use gas chromatography-mass spectrometry (GC-MS) and time-of-flight-secondary ion mass spectrometry (ToF-SIMS) datasets collected from an organic-rich, thermally immature Jurassic geologic sample to constrain MS imaging analysis of indigenous lipid biomarkers in geologic samples. GC-MS data show that the extractable fractions are dominated by C27-C30 steranes and sterenes as well as isorenieratene derivatives. ToF-SIMS spectra from organic matter-rich laminae contain a strong, spatially restricted signal for ions m/z 370.3, m/z 372.3, and m/z 386.3, which we assign to C27 sterenes, cholestane (C27), and 4- or 24-methyl steranes (C28), respectively, as well as characteristic fragment ions of isorenieratene derivatives, including m/z 133.1, m/z 171.1, and m/z 237.1. We observed individual steroid spatial heterogeneity at the scale of tens to hundreds of microns. The fine-scale heterogeneity observed implies that indigenous lipid biomarkers concentrated within specific regions may be detectable via ToF-SIMS in samples with even low amounts of organic carbon, including in samples returned from Mars.
Original language | English |
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Pages (from-to) | 936-950 |
Number of pages | 15 |
Journal | Astrobiology |
Volume | 23 |
Issue number | 9 |
DOIs | |
State | Published - Sep 1 2023 |
Funding
All the authors thank the UIC Research Resources Center for access to the Electron Microcopy Core. ToF-SIMS characterization was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility, and using instrumentation within ORNLs Materials Characterization Core provided by UT-Battelle, LLC under contract number DE-AC05-00OR22725 with the U.S. Department of Energy.
Keywords
- GC-MS
- Geology
- Lipid biomarkers
- Mars sample return
- Mass spectrometry imaging
- Organic geochemistry
- Organic molecular biosignatures
- ToF-SIMS