POSSIBLY UBIQUITOUS PRESERVATION OF MICROBES IN PERMIAN HALITE

Primary fluid inclusions in evaporite minerals, representing entrapment of the parent brine from which the mineral precipitated, have the potential to preserve microorganisms and genetic material for up to hundreds of millions of years. Previous workers have cultured microbes from ancient halite, indicating that the encapsulated microbes may remain viable; however, no studies extracting either genetic material or viable microorganisms from material older than 97 KY have visually documented microorganisms in situ within primary fluid inclusions using microscopy. This would not only confirm the authenticity of ancient microbes, but also provide stronger evidence that they are indeed the same age as the host crystal, thereby ruling out contamination. Here we show suspect microbes preserved within primary, unaltered fluid inclusions in Permian halite using in situ optical petrography, epifluorescence microscopy, and confocal laser scanning microscopy. Suspect microbes in Permian halite are typically sub-spherical, vary from colorless to dark red, and occur in two size ranges: ~1-2 microns, consistent with prokaryotes, and ~5-10 microns, interpreted as eukaryotes. Autofluorescence is common, and includes yellow, orange, and green. Yellowish-orange structures, possibly expelled and crystallized carotenoids, are commonly associated with suspect microbes. Fluid inclusion contents range from individual suspect microbes to clusters of numerous suspects and crystals. Raman spectroscopic analysis of Permian suspect microbes and possible organic crystals has so far been hindered by their much more intense fluorescence. Suspect microbes are seemingly ubiquitous in Permian halite, having been observed in a variety of halite samples from both North America and Europe. Additionally, distinct suites of suspect microbes, based on size and color, seem to be related to the general depositional setting of the halite, i.e., non-marine saline lake versus marginal-marine environments. Our use of in situ techniques to identify ancient microbes supports previous reports of viable Permian microbes preserved in halite and documents a simple yet effective method that could be utilized in the search for extraterrestrial life.