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NASA's Curiosity robot rocked the scientific community six years ago by apparently detecting traces of methane – a major life-related chemical – on Mars. The researchers could not confirm these results in the following years, but the situation has now changed thanks to a new analysis of the data collected in orbit.
A new study published today in Nature Geoscience confirms that NASA's Curiosity robot detected a methane spike on June 15, 2013, while it was exploring Gale Crater on Mars. The new paper, led by Marco Giuranna of the Institute of Space Astronomy and Space Planetology in Rome, Italy, does not explain how methane appeared on the red planet, but the independent confirmation is a potential sign that Mars has already presented conditions conducive to life during its ancient past. More radically, this suggests that microbial life once existed on Mars, producing the stinking gas that escapes from the intestines of the planet.
That methane can exist on Mars is a subject of considerable debate. Methane is an essential condition of habitability and perhaps even a signature of life itself. The problem with methane, however, is that it does not last long in the atmosphere. Any methane detected would have been rejected relatively recently. For Mars, this means that the gas probably escapes from the surface. In addition, the sporadic and intermittent nature of these apparent methane peaks suggests that methane is released at irregular intervals.
To prove that methane exists on Mars would be a huge problem. Scientists have therefore been very careful to avoid any missteps in this region. The 2013 Curiosity detection was intriguing, but as the observation could not be corroborated by other instruments, such as the satellites in orbit, it could not be confirmed definitively.
The measure of curiosity has now been confirmed thanks to a new analysis of data collected by the European Space Agency's Mars Express orbiter at the time. More specifically, the data collected by the satellite Fourier planetary spectrometer on June 16, 2013, above Gale Crater, are consistent with the measures taken by Curiosity the day before. This is the first time ground measurements have been confirmed by an orbiting spacecraft, according to a statement by ESA.
Giuranna and her colleagues confirmed Curiosity's observation by examining 20 months of data collected by Mars Express and developing a new technique allowing researchers to browse hundreds of measurements made on a single area. Interestingly, Mars Express did not detect any other methane spike during the observation period, with the exception of that detected by Curiosity.
"In general, we did not detect any methane, apart from a definitive detection of approximately 15 parts per billion of methane volume in the atmosphere, a day after Curiosity reported a rise about six parts per billion, "said Giuranna in a statement" Although the parts per billion usually represent a relatively small amount, they are quite remarkable for March. Our measurement is an average of about 46 tonnes of methane present in an area of 49,000 square kilometers observed from our orbit. . "
At the time of the Curiosity sighting, the scientists assumed that the methane came from the north of the rover and was transported to the Gale crater by the southerly winds. The new interpretation presented in the new study offers a different scenario. The amount of methane detected, as well as the geology of the area, suggest that the peak of methane has occurred in the crater Gale itself. Two independent analyzes were used to reach this conclusion, including computer simulations assessing the probability of methane emissions from the Martian surface and the identification of geological features in the Gale crater consistent with the associated methane peak. .
This kind of thing happens on Earth, usually along tectonic faults and natural gas deposits. Something similar can happen on Mars, in this case, along the faults of the region of Aeolis Mensae.
"We have identified tectonic faults that could extend below a proposed region to contain shallow ice," said study co-author Giuseppe Etiope of National Institute of Geophysics and Volcanology, in a statement from ESA. "Remarkably, we have seen that atmospheric simulation and geological evaluation, performed independently of one another, suggested the same source region of methane."
The researchers assume that the methane detected on Mars is caused by small transient geological events, rather than a process in which the gas is constantly replenished in the Martian atmosphere. However, much remains to be learned about this process, including how the gas is removed from the atmosphere and the nature of the Aeolis Mensae site.
It is important to note that the methods used in this new study could lead to the discovery of other sites producing methane on Mars, which could lead to spots that once, most likely, harbored life.
[Nature Geoscience]
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