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Fine slice of the Martian meteorite ALH-77005. Scientists have found evidence of microbial mediation in the fusion pocket, inside the rectangle. Image via Gyollai et al.
Has there ever been life on Mars? We are still waiting for a definitive answer to this longstanding question, although the evidence continues to show that there may well have been small critters – albeit most likely microscopic – inside or below of those distant red sands. Such a discovery would have profound implications for the search for life elsewhere in the solar system and on exoplanets orbiting other stars. Now, a research team in Hungary has discovered another interesting clue: mineralized and filiform organic matter encrusted in a Martian meteorite – ALH-77005 – in the Allan Hills area of Antarctica. The material in the meteorite is similar to that produced by iron-oxidizing microbes on Earth.
The peer-reviewed results were published online in the journal Open Astronomy March 28, 2019. According to the principal author Ildiko Gyollai of the Center for Research on Astronomy and Earth Sciences of the HAS in Budapest:
Our work is important for a wide audience because it integrates the sciences of planets, Earth, biology, chemistry and the environment and will interest many researchers in these fields. The research will also interest planetary scientists, meteorite and astrobiology experts, as well as researchers from the early life and the general public, as it offers an example of a new aspect of microbial mediation in mineral meteorites.
Another view of the same thin slice of the meteorite in polarized light. Image via Gyollai et al.
Martian meteorite ALH-77005, found at Allan Hills, Antarctica in 1977. Image via NASA / Johnson Space Center / Wikipedia.
The mission (1977-1978) of the Japanese National Institute of Polar Research discovered the meteorite ALH-77005 in the Allan Hills, in the Antarctic, in 1977. It is estimated that the meteorite dates from 175 million. # 39; years. It is a shergottite meteorite – composed of igneous rock – which takes its name from the Shergotty meteorite, fallen to Sherghati, India (formerly Shergotty), in 1865. About three quarters of the known Martian meteorites are shergottites.
How do we know that these meteorites came from Mars? Like other Martian meteorites, it is known that ALH-77005 originates from Mars because its composition is similar to that of rocks and atmospheric gases analyzed by the Mars satellite. The Curiosity rover confirmed the connection between Mars itself and these meteorites discovered on Earth in October 2013, after analyzing argon in the atmosphere of Mars. Argon has turned out to be the same as the traces of argon in meteorites.
For this new study, the researchers took a very fine cut sample of the meteorite and studied it using microscopy for microtextures – microscopic texture patterns – and FTIR-ATR microscopy. What they found is intriguing. They found embedded spherical and filiform structures, materials that represent possible biosignatures, that is, the mineralized remains of ancient microbes and their alteration of minerals in the rock. The possible biosignatures are found next to the opaque minerals and inside the pockets of melting shocks, resulting from the shock and fracturing resulting from the meeting of the meteorite with the Earth. As the paper also notes:
The other biogenicity signatures of ALH-77005 are the strong negative delta-c-13, enriching iron, manganese, phosphorus, and zinc in a shock-melt support scenario.
Our study proposes the presence of microbial mediation on Mars.
Overall, the underlined results of ALH-77005, as listed in the document, include:
– Possible oxidizing bacterium filamentous iron found in the pouch of shergottite in the molten state.
– Possible biosignatures determined by optical microscopy and by FTIR-ATR.
– Bioessential data and carbon isotopic data.
– Comparison of similar results from Mezö-Madaras, Mócs, Knyahinya, which all suggest a biogenicity on Mars, according to these authors.
The arrows indicate suspected microbial biosignatures in the ALH-77005 meteorite. Image via Gyollai et al.
This is not the first time that possible evidence of life has been found, or at least claimed, in Martian meteorites. An excellent example – in 1996, a team of scientists led by David S. McKay announced the discovery of experimental microbial fossils resembling bacteria in another Allan Hills meteorite – ALH-84001. It was widely reported and President Clinton delivered a speech about it at the time. Other studies conducted by other scientists, however, contradicted the interpretation of life, since possible non-biological explanations had been found for the formation of microscopic rod-shaped features.
Similar abiotic characteristics (not related to life) were created in the laboratory, although McKay insisted that these results were obtained with unrealistic raw materials as starting points and did not explain much of the characteristics found in ALH-84001. In 2010, another team of scientists, including McKay, said they found three times more original data than fossils, including more biomorphs (presumed fossils) in two other Martian meteorites, and more evidence at home. other places in the Allan Hills. meteorite itself.
The curious mineral formations of the ALH-77005 now join a growing list of provisional evidence of ancient life on Mars. If they can be confirmed, it will be one of the most exciting discoveries of planetary science, and in human history.
Some of the rod-like objects found in the Martian meteorite ALH-84001, seen by scanning electron microscopy, were announced in 1996. Image via McKay et al. / Lunar and Planetary Institute.
Conclusion: It remains to be seen whether these new results from Hungary will be examined further, but they are certainly intriguing and could help reinforce the previously announced discoveries of microbial fossils in Martian meteorites.
Source: Mineralized Biosignatures in ALH-77005 Shergottite – Martian Life Indices?
Via Phys.org
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