Various sulfate minerals exist on Mars; except for gypsum, they are understudied on Earth. Extremophiles have been documented in modern gypsum and halite and ancient halite, but other chemical sediments have not been evaluated for biosignatures. Here, we present the first observations and analysis of microorganisms and organic compounds in primary fluid inclusions in the Mars-analog mineral mirabilite, Na2SO4∙10H2O, from Great Salt Lake, Utah, USA. Microscopy by transmitted light and ultraviolet-visible (UV-vis) light, and Raman spectroscopy, show abundant bacteria and/or Archaea, algae, fungi, diatoms, protozoa, and organic compounds such as beta-carotene. This discovery expands our current knowledge of biological materials trapped in salt and aids the search for life on Mars, both for sample selection by rover and for analyses of return samples on Earth.

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<p>Experimental setup showing sample chamber used to prevent dehydration of mirabilite crystals and Raman signatures of mirabilite crystal, Great Salt Lake brine, and inclusion liquid. </p>

<p>Experimental setup showing sample chamber used to prevent dehydration of mirabilite crystals and Raman signatures of mirabilite crystal, Great Salt Lake brine, and inclusion liquid. </p>