Abstract EANA2026-66

The rock record on Earth contains information about the geological history of the planet and the evolution of life. Life history can be traced back through fossils, macro and micro. However, the latter could be artefacts of abiotic processes that mimic biological morphologies (biomorphs), rather than remains of microorganisms (true microfossils). This results in a lack of clarity on how to assess the biogenicity of microstructures in the rock record. Earth is not the only planet in the solar system whose rock record can be investigated. Mars has long been one of the most intriguing bodies outside of Earth for the search for potential extant or extinct life. Ongoing and future missions including Mars 2020 (NASA) and ExoMars (ESA/NASA), are and will sample in Jezero Crater and Oxia Planum, respectively. Both sites are ancient Martian terrains containing rocks from the Noachian (ca. 4.1-3.8 Ga), partially overlapping with Earth’s late Hadean (ca. 4.5-4.0 Ga)  and early Archean (ca. 4.0-2.5 Ga) Eons. Through these missions, we might find similar microstructures to those we observe on Earth and must be prepared to determine their biogenicity.

On Mars, most of the mineral diversity is represented by clays and carbonates, products of water-rock interactions, which could derive from hydrothermal activity. A hydrothermal context would also allow for the presence of simple organic molecules, e.g. single chain amphiphiles (SCAs). SCAs under mild temperature (~70°C) and alkaline pH self-assemble into protocells which once preserved in a mineral matrix may form biomorphs that can resemble life’s morphologies in different ways.

Here we investigate the synthesis of protocells and their entombment in lab-made Martian analogues. Protocells were formed from SCAs in alkaline solution at 70°C and entombed in mineral matrices reflecting those of the two Martian sites mentioned above. Matrices with organics underwent artificial diagenesis consisting of varying temperatures (from 50-250°C, with an increment of 50°C) and different temporal ranges (1, 5, and 10 days). Analysis was performed using Fourier-transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), and pyrolysis-gas chromatography mass spectrometry (py-GC-MS). These data reflect some of which could be obtained in-situ during rover missions.

 

This experimental framework, providing both morphological and chemical data, will help us to understand potential abiotic microstructures present in Martian samples, avoiding false positives in the search for signs of past life.