A new atmospheric model of Mars to explain the solution of the methane enigma


Figure: Illustration describing the possible processes by which methane could appear in the atmosphere of Mars (sources) and eliminated (sinks). ©NASA/JPL/SAM-GSFC/U. Michigan.


Researchers, led by the Centro de Astrobiología (CAB, CSIC-INTA), have compared data on the presence of methane in the Gale Mars crater obtained by NASA's Curiosity rover with model-based atmospheric transport experiments Martian atmospheric MRAMS. Its results are compatible with the detection of methane inside the crater provided that, in addition, there is a rapid, and for the moment unknown, mechanism of destruction of methane near the ground that explains that it is not detected by the probes in orbit.


The detection of methane in the Gale de Marte crater by the TLS-SAM (Tunable Laser Spectrometer - Sample Analysis at Mars) instrument, a laser spectrometer aboard NASA's Curiosity rover, was received at the time with great expectation, due, above all, to the implications that the presence of methane would have on the possible existence of Martian organisms.

The photochemical life of methane in the atmosphere is several hundred years. This time is much longer than the atmospheric mixing time scale, so it is considered that the gas should be well mixed, except when it is near a source or in short periods of time just after a timely release of methane. Although most measurements indicate low background levels, of 0.4 parts methane per billion atmospheric volume, the detected increases of various parts per billion (or even greater) and the subsequent return at the background level are difficult to explain.

A group of researchers, led by Jorge Pla-García, a researcher at the Centro de Astrobiología has compared data obtained with TLS-SAM with atmospheric transport experiments based on the Mars Regional Atmospheric System (MRAMS), a high-resolution model developed by Scot C. R. Rafkin, co-author of this study, and his team. The objective of this study, recently published in the Journal of Geophysical Research: Planets, has been to know the exact location of the emission zone, its spatial extent, how long the methane is being released and whether the models are consistent with the data obtained by TLS-SAM.

The most plausible scenario for reconciling TLS-SAM observations with MRAMS simulations is a continuous emission inside the Wales crater with the source located near the rover, but it would be necessary to process rapid destruction of methane near the ground that would prevent transport to the middle/high layers of the atmosphere (as the models predict). "That unknown methane destruction mechanism near the ground would reconcile Curiosity's measurements with our simulations and explain that ESA's TGO mission (in orbit on Mars) did not detect methane above 3km altitude," explains Jorge Pla-García.


Fuente: UCC-CAB

Fecha: 2019-08-19


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