No trace of methane on Mars, the ‘mystery’ deepens

Mars research called ExoMars Trace Gas Orbiter by the European Space Agency (ESA) has not given results and has established new limits on the quantities of methane present together with ethane, ethylene and phosphine in the atmosphere of Mars, the four so.called “biomarker” gases, which are potential signs of life. The results were published in three articles in the journals Astronomy & Astrophysics and ScienceDirect.

Methane is a biomarker of key interest, as much of that found on Earth is produced by living things or geological activity, and so the same could be true for Mars as well.

“We used the Trace Gas Orbiter (TGO) to further refine the upper limit for methane on Mars, this time with data collection for more than 1.4 Martian years – 2.7 Earth years,” explains Franck Montmessin. , of the LATMOS laboratory of the University of Versailles Saint Quentin en Yvelines, co.principal investigator of the Atmospheric Chemistry Suite (ACS) of Trace Gas Orbiter and lead author of one of three new articles on Martian biomarkers.

“We have not found any sign of the gas, which suggests – says the researcher – that the amount of methane on Mars is probably even lower than previous estimates suggest”. The ‘mystery of methane’ on Mars has been going on for many years with contradictory results from missions including ESA’s Mars Express and NASA’s Curiosity rover, which capture sporadic peaks and bursts of gas in the atmosphere of Mars, fluctuations both in orbit and on the planet’s surface, gas signs that vary with the seasons or by not observing methane at all.

Previous estimates range from 0.2 to 30 parts per billion volume (ppbv), indicating up to 30 molecules of methane per billion molecules. For reference, methane is present in the earth’s atmosphere at nearly 2000 ppbv. The scientists also looked for signs of methane around Curiosity’s work area, the Gale crater, and found nothing, despite the rover reporting the presence of methane in that area.

“Curiosity measures right from the surface of Mars, while the orbiter makes measurements a few kilometers above, so the difference between these two results could be explained by any methane trapped in the lower atmosphere or in the immediate vicinity of the rover,” adds Franck. “We found no signs of methane on Mars and set an upper limit of 0.06 ppbv, which agrees with TGO’s initial results using ACS,” says lead study author Elise Wright Knutsen. , formerly at NASA’s Goddard Space Flight Center, in the United States, and now in LATMOS, France.

The search for life on Mars, or its persistent traces, is a central goal of the ExoMars program and the hunt for biomarkers in particular is a primary goal of the Trace Gas Orbiter. The next ExoMars “Rosalind Franklin” rover, scheduled to launch in 2022, will complete TGO’s hunt for biomarkers by digging into the Martian surface. Underground samples may be more likely to retain biomarkers, as the material is shielded from the harsh radiation environment of space.

By Editor

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