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On February 18th, 2020, the Mars 2020 Perseverance rover landed on the surface of Mars. One of the main goals of this mission is to search for evidence of past life on Mars. Jezero crater, the landing site of the rover, was selected as an exciting astrobiological target because it is the site of an ancient river delta and lake that may once have been habitable. To determine if Mars was once inhabited, we will search for biosignatures, traces of life that are preserved in the rock record. On Earth, we study ancient biosignatures to understand what the ancient biosphere looked like and how it interacted with the planet. My research investigates ancient biosignatures from Earth with the goal of providing a framework that we may use to identify and interpret similar biosignatures in Jezero crater if they are present.
Microbes thrived on Earth from at least the early Archean to the present and similar organisms may have emerged on a warmer, wetter Mars in the past, as well. However, it is difficult to find evidence of past life and even more difficult to interpret it because microbes are composed of soft organic material that is often rapidly degraded before it can be preserved in the rock record. Still, some exceptional biosignatures were preserved by amorphous and microcrystalline materials like chert (microcrystalline silica) during the Archean and Proterozoic eons—time periods ranging from ~3.8 billion years ago to ~540 million years ago. These biosignatures and the minerals and processes that preserved them provide an important window into the ancient biosphere on Earth and may aid in the identification and interpretation of potential biosignatures in Jezero crater, the landing site of the Mars2020 rover. Here, I will describe the astrobiological goals of the mission, what we know about Jezero crater and its potential past habitability, and the instruments that we will use to search for ancient biosignatures. I will present new insights into organic matter preservation on the ancient Earth by chert and reveal that the organic matter is commonly associated with calcium-, magnesium-, and aluminum- rich phases. These results shed light on the interactions between the biosphere and geosphere on the early Earth and suggest that interactions among organic matter and major element cations in seawater may have promoted the preservation of organic matter by chert. Based on these results, we hope to search for similar chemical fingerprints using instruments onboard the Perseverance rover to identify potentially similar biosignatures in the silica deposits in Jezero crater. If such biosignatures exist, these results will also help us to interpret how organisms may have interacted with the martian environment in the past. |