Abstract
AbstractSurface mineral crusts on Earth are highly diverse and usually, contain microbial life. Crusts constitute an attractive target to search for life: they require water for their formation, they efficiently entrap organic matter and are relatively easy to sample and process. They hold a record of life in the form of microbial remains, biomolecules and carbon isotope composition. A miniaturized Raman spectrometer is included in the ExoMars 2020 payload as it is sensitive to a range of photosynthetic pigments. Samples from the Haughton Impact Structure, Canadian High Arctic and others, shows the preservation of pigments in a range of crust types, especially supra-permafrost carbonate crusts and cryptogamic crusts. The Raman spectral signatures of these crusts are shown along with biomarker analysis to showcase these techniques prior to the ExoMars 2020 mission. Carotenoids and other photoprotective microbial pigments are identified in the Haughton surface crusts using Raman spectroscopy. Gas chromatography-mass spectrometry analyses show a distribution of fatty acids which are most likely from a cyanobacterial source. The successful demonstration of these analyses in the Haughton Impact structure shows the biosignature of surface mineral crusts can be easily extracted and provides an excellent target for sampling evidence of life on Mars.
Highlights
Mineral crusts are a widely developed feature at the rock or sediment surface, wherever there is a flux of water. They occur in all climatic zones on Earth, from tropical to polar desert, their chemistry and morphology vary with surface hydrology, temperature and substrate
We address eight types of crust that have been proposed as candidate environments in the search for life on Mars
Raman spectra were obtained using a Renishaw InVia H36031 confocal Raman microscope operating at a wavelength of 514.5 nm green monochromatic laser light, which is similar to the 2020 ExoMars flight instrument wavelength of 532 nm. 5% power (1.5 mW) was used with 10 accumulation and 2 s exposure time, giving a good signal-to-noise ratio
Summary
Mineral crusts are a widely developed feature at the rock or sediment surface, wherever there is a flux of water They occur in all climatic zones on Earth, from tropical to polar desert, their chemistry and morphology vary with surface hydrology, temperature and substrate. The range of deposits includes duricrusts (calcrete, silcrete, gypcrete, ferricrete-laterite), rock (desert) varnish, crusts above permafrost and salt crusts This list is much greater if mineral precipitates from flowing fluids are included, such as speleothems, travertine and other hot spring deposits, tufa, sea spray deposits and chemosynthetic deposits. Even in the Precambrian, crusts have been identified of duricrust (Watanabe et al 2000; Beukes et al 2002) and hot spring (Melezhik & Fallick 2001) origin This discussion will focus on precipitates associated with surface moisture
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
