Typologie d'actualités: Group Exobiology

Raman spectroscopy for detecting biomolecules below surface of Mars

Chlorophyllin, beta-carotene, melanin, chitin, cellulose, naringenin and quercetin: these exotic-sounding compounds are biomolecules that allow certain organisms to live in extreme environments. They are thus prime targets for the search for life on Mars. In order to assess their resistance to Martian conditions, an experiment called BIOMEX, for BIOlogy and Mars EXperiment, was carried out on the exterioir of the International Space Station (ISS).

The molecules were mixed with Martian soil analogs before being exposed to solar radiation outside the ISS for 469 days. Back on Earth, they were   analyzed by Raman spectroscopy at the German Aerospace Center (DLR) in Berlin.

Raman spectroscopy analyses the molecular and mineralogical composition of a sample. Compatible with robotic space missions, it is one of the key techniques for searching for traces of life on Mars. NASA's Perseverance rover currently exploring Jezero Crater is equipped with two Raman spectrometers, and ESA's future ExoMars mission will also use one to aid detection of possible biosignatures on Mars in 2030.

The BIOMEX experiment involved many researchers, including members of the Exobiology team at CBM, Olréans. The results, published in the Science Advances, reveal that these biomolecules are resistant to Mars conditions because the minerals composing the Martian soil have a protective effect against UV. Most importantly, the study shows that these molecules could be identified without difficulty on Mars by Raman spectroscopy.

Biosignature stability in space enables their use for life detection on Mars
Mickael Baqué,Theresa Backhaus et al.
Science Advances, Vol 8 -DOI: 10.1126/sciadv.abn7412

Setting the geological scene for the origin of life and continuing open questions about its emergence

The origin of life is one of the most fundamental questions of humanity. It has been and is still being addressed by a wide range of researchers from different fields, with different approaches and ideas as to how it came about. However, what is missing from the prebiotic chemical experiments is precise information about the environment and the conditions reigning on the early Earth during the Hadean Era (4.5-4.0 Ga). In particular, there is a lack of understanding about the inorganic ingredients that were available, the stability and longevity of the various environments suggested as locations for the emergence of life, as well the kinetics and rates of the prebiotic steps leading to life.

This contribution reviews our current understanding of the geology of the early Earth at the time when life emerged. Having set the geological scenario, we evoke the still open questions about the origin of life: did life start organically or in mineralogical form? If organically, what was the origin of the organic constituents of life? What came first, metabolism or replication? What was the time-scale for the emergence of life? We conclude that the way forward for prebiotic chemistry is an approach merging geology and chemistry, i.e., far-from-equilibrium cycling of organic reactions occurring repeatedly and iteratively at mineral surfaces under hydrothermal-like conditions.

Setting the geological scene for the origin of life and continuing open questions about its emergence
Frances Westall1, André Brack, Alberto G. Fairén and Mitchell D. Schulte
Frontiers in Astronomy and Space Sciences - 05 January 2023 - Volume 9 - doi : 10.3389/fspas.2022.1095701 9:1095701

How the hydrothermal environment of Primeval Earth may have influenced the choice of sugar in DNA and RNA

CBM scientists give answers in a publication published in the Journal Nature Communications. Why is Furanose the only sugar found in the composition of DNA and RNA while this form of sugar is not the most stable, so not the most abundant, in temperature conditions and pressure we are currently experiencing? These are the hydrothermal sources, omnipresent on the surface of the primitive land, and their complex thermal influence, which could be at the origin of this selectivity. This study conducted by scientists from the Molecular Biophysics Center, which is the subject of an article in the Nature Communications journal, should make it possible to better understand why and how molecules come together to give life in a primitive geological context.

Reference

Avinash Vicholous Dass, Thomas Georgelin, Frances Westall, Frédéric Foucher, Paolo De Los Rios, Daniel Maria Busiello, Shiling Liand & Francesco Piazza
Equilibrium and non-equilibrium furanose selection in the ribose isomerisation network
Nature Communications, 12 2749 (2021) https://www.nature.com/articles/s41467-021-22818-5

See the news on the site of the Institute of Chemistry

 




Unveiling billion-year old life forms with X-ray vision

An international team of scientists from Brazil, France and Switzerland with financial support from the Serrapilheira Institute and Fapesp, has obtained the most detailed 3D views ever achieved of very ancient traces of life on Earth. The studied microfossils, from the Gunflint Formation, in Canada, are approximately 1.9 billion years old, and are the preserved remains of microorganisms similar to bacteria existing today, but from a period when only microscopic life existed on Earth. Using an advanced imaging method based on synchrotron light, unprecedented details of the shape, composition and preservation of these microfossils was attained. Moreover, in one locality, fossils previously termed “hematite-coated” are revealed to be composed of organic material – invisible in optical microscopy – coated with crystals of the iron oxide maghemite, instead of hematite. This finding challenges our understanding of past life and opens exciting perspectives for the study of even older fossils or future samples returned from Mars.

Maldanis, L., Hickman-Lewis, K., Verezhak, M. et al. Nanoscale 3D quantitative imaging of 1.88 Ga Gunflint microfossils reveals novel insights into taphonomic and biogenic characters. Scientific Reports 10, 8163 (2020). https://doi.org/10.1038/s41598-020-65176-w

Read the article

3D observation of microfossils

Metallomics in geological time: trace element biosignatures evidence the influence of ocean chemistry on Earth’s earliest ecosystems

We used a combination of techniques: microbeam particle-induced X-ray emission spectroscopy (PIXE), carbon isotope geochemistry and electron microscopy. This has allowed us to discover trace element signatures of life in 3.33 billion-year-old rocks from South Africa. These signatures support a long-standing hypothesis that biological dependency on trace elements results from the enrichment of these elements in the metal-rich, hydrothermally influenced habitats of early life.

We approached this challenge through the biological concept of the metallome, which refers to the entirety of the inorganic species (metal and metalloid) within a cell. Although the genome and proteome do not survive fossilisation over billions of years, it is probable that metal concentrations within carbonaceous materials could do so, and indeed we found this to be the case in numerous carbon-rich microstructures from the Josefsdal Chert.

We found that a range of elements crucial to anaerobic microbes, including Fe, V, Ni, As and Co, were enriched within carbonaceous material characterised by negative carbon isotope signatures indicating biological origins.

Palaeo-metallome compositions could be used to deduce the metabolic networks of Earth’s earliest ecosystems and, potentially, as a biosignature for the evaluation of organic materials found on Mars.

The article “Metallomics in deep time and the influence of ocean chemistry on the metabolic landscapes of Earth’s earliest ecosystems” released March 18th in Scientific Reports.

Contact: keyron.hickman-lewis@cnrs.fr; frances.westall@cnrs.fr