Earth’s oldest stromatolites and the search for life on Mars

The earliest morphological traces of life on Earth are sometimes extremely controversial, each as a result of non-biological processes can produce comparatively related constructions and since such fossils have usually been subjected to superior alteration and metamorphism.

Stromatolites, layered organo-sedimentary structures reflecting advanced interplays between microbial communities and their atmosphere, have lengthy been thought-about key macrofossils for all times detection in historic sedimentary rocks; nonetheless, the organic origin of historic stromatolites has incessantly been criticized.

An article launched Friday within the journal Geology makes use of a variety of superior two- and three-dimensional analytical strategies to ascertain the organic origins of Earth’s oldest stromatolites from the three.48-billion-year-old Dresser Formation, Pilbara, Western Australia.

Though these stromatolites have undergone extreme diagenesis and weathering and protect no natural supplies, a staff led by Dr. Keyron Hickman-Lewis of the Pure Historical past Museum, London, has used optical and electron microscopy, elemental geochemistry, Raman spectroscopy, and laboratory- and synchrotron-based tomography to establish quite a few traits indicative of a organic origin.

Along with performing laboratory tomography of 3D stromatolitic macrostructure, the staff was capable of obtain the primary sub-micron pixel and voxel sizes for imaging of Precambrian stromatolite microstructures through phase distinction imaging utilizing the SYRMEP beamline on the Elettra Synchrotron, Trieste, Italy. This enabled the identification of non-uniform layer morphologies, void areas arising from the degassing of decaying natural supplies, and pillar-like vertical constructions interpreted as microbial palisade construction, a typical indicator of phototrophic development.

The Dresser Formation stromatolites have been principally changed by hematite (iron oxide) resulting from latest weathering. Whereas this renders natural geochemical analyses unattainable, this composition is extremely related for the seek for life on Mars.

Sedimentary rocks on the floor of Mars have been subjected to related pervasive oxidation and likewise comprise principally iron oxides of their higher centimeters to meters. On this regard, the Dresser Formation stromatolites could also be uniquely related supplies to tell us of a exact fashion of biosignature preservation anticipated on Mars.

Because the Mars 2020 Perseverance rover continues its exploration of Jezero crater, we should always seek for morphological expressions of life resembling these recognized within the Dresser Formation and put together for superior multi-technique analyses when Martian samples are ultimately returned to Earth.