DEEP ULTRAVIOLET RAMAN SPECTROSCOPY OF NEOARCHEAN MICROBIALITES AS ANALOGS TO POSSIBLE MARS 2020 SAMPLES

The primary science goal of NASA’s Mars 2020 mission is to search for evidence of ancient microbial life on Mars. To achieve this goal, the Perseverance rover is exploring Jezero Crater (3.2–3.8 Ga), which was once a delta-lake system. Jezero was chosen as the target for this mission because of the high likelihood that it was habitable during Mars’ Noachian period, and because it is host to geological deposits with a high biosignature preservation potential. These include possible carbonate deposits at the crater rim, near a large river inlet and delta.

The rover’s science payload includes several cameras and instruments to facilitate the detection of evidence of past life that might be preserved in Jezero, such as organic matter, microbialites, or other biosignatures. One of these instruments is a UV Raman spectrometer called SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals). To allow for accurate interpretation of SHERLOC data, it is essential to build a library of Raman spectra collected from samples of Earth materials that are similar to the types of materials the Perseverance rover might encounter on Mars.

Here we present Raman spectra collected from diverse samples of Neoarchean microbialites from the Gamohaan Formation (Kaapvaal Craton, South Africa) using a SHERLOC-analogue UV-Raman spectrometer. The analysed samples contain abundant fossilized organic matter. Some of the samples formed through microbially induced carbonate precipitation. Of these, some were subsequently silicified and are now composed of chert. Other analysed samples composed of chert formed through early diagenetic silicification of microbial mats. The data from these samples could help scientists recognize analogous microbialites in Jezero Crater.