Exobiology and Evolutionary Biology

Biosignatures in Volcanic Rocks - Microweathering of Olivine on Earth and Mars (2)

PI: Radu Popa

This work is guided by the NASA goal of identifying and investigating past and present habitable environments on Mars and determining if there ever was life on that planet. Volcanic rocks are capable of recording evidence of life on Earth dating back 3.8 billion years and to even earlier epochs on Mars. Currently there is an ongoing debate about the biogenicity of some oddly shaped features (such as curved and branching microchannels) that are present in glass and minerals from volcanic rocks from the Earth’s early Archaean Epoch (3.8 to 3.3 billion years), in modern volcanic rocks, and in a group of 1.3 billion years old Martian meteorites. The modern microchannels on Earth often contain DNA and other biologically important compounds; one interpretation of this is that microchannels may have been produced by microorganisms. However, the biological production of microchannels has never been demonstrated in experiments, and so in the absence of such verification, microchannels cannot be used as biosignatures of past life on Mars. We propose that some microchannels from olivine (a mineral common on both Earth and Mars) are produced by the activity of a physiological group of microbes known as iron-oxidizers, and that some rocks from Mars still retain such signatures if life ever existed on this planet.
OBJECTIVES. Our objective is to verify whether iron-oxidizing bacteria prefer living on olivine crystals, if their activity leaves specific fingerprints that are recognizable by microscopy, and to apply this knowledge to the study of terrestrial rocks and Martian meteorites.
METHODS. To achieve our goals we will study the environmental diversity of iron-oxidizers using molecular fingerprinting, isolate microbes and use them to colonize olivine crystals and study the weathering patterns they produce. We will apply this knowledge on Martian meteorites to verify if microchannels and other features consistent with microbial weathering are visible.
SIGNIFICANCE. This work will help establish fingerprints of microbial activity necessary in the search for past life on Mars. The optical resolution necessary for the observation of the microchannels in polished surfaces will be determined, to provide guidance for instrument development that could be used for the search for microchannels on the Martian surface.