Could the presence of methane gas signal life on Mars?
Credit: Newcastle University

 

Bursts of methane on Mars have been detected by NASA’s Curiosity rover and remote ground-based sensing observations.

Seasonal changes in methane background levels and “methane spikes” have been detected on the spot on Mars a few feet above the Martian surface. Larger methane plumes has been identified via ground-based remote sensing, however their origin have not yet been adequately explained.

Methane can be created over time through both geological and biological routes. Since its first detection in the Martian atmosphere in 2003, there has been speculation about the source of the gas.

Does the presence of this gas signal life on the Red Planet?

Selfie of Curiosity Mars rover on the prowl.
Credit: NASA/JPL-Caltech/MSSS

Rock erosion ruled out

New research by Newcastle University scientists in the UK appears to rule out that wind erosion of Mars rocks is eking trapped methane from fluid inclusions and fractures on the planet’s surface.

“Ultimately, what we’re trying to discover is if there’s the possibility of life existing on planets other than our own,” explains Emmal Safi, a postdoctoral researcher in the School of Natural and Environmental Sciences and lead author of the just-published research.

The new work – “Aeolian abrasion of rocks as a mechanism to produce methane in the Martian atmosphere” – appears in Scientific Reports.

June 2018 graphic relates that Curiosity rover detected seasonal changes in atmospheric methane in Gale Crater.
Credit: NASA/JPL

Different rock types

“The questions are – where is this methane coming from, and is the source biological? That’s a massive question and to get to the answer we need to rule out lots of other factors first,” said principal investigator, Jon Telling, a geochemist also based in the School of Natural and Environmental Sciences at Newcastle University.

The scientists realized that one potential source of the methane that people hadn’t really looked at in any detail before was wind erosion, releasing gases trapped within rocks.

High resolution imagery from Mars orbit over the last decade have shown that winds on the Red Planet can drive much higher local rates of sand movement, and hence potential rates of sand erosion, than previously recognized.

The research used new data alongside previously published data to consider the likely methane contents of different rock types and whether they have the capacity to produce measurable levels of methane when worn away.

Europe’s Mars Express orbiter matches methane spike measured by Curiosity
Credit: ESA/Giuranna et al (2019)

Unlikely scenario

The upshot: The team found that for wind erosion to be a viable mechanism to produce detectable methane in the Martian atmosphere, the methane content of any gases trapped within rocks would have to rival those of some of the richest hydrocarbon containing shales on Earth – a highly unlikely scenario, they found.

Funded by the UK Space Agency, the study concludes that the cause of methane spikes on Mars is still unknown.

“It’s still an open question. Our paper is just a little part of a much bigger story,” Safi says.

Other sources

“From the data put forward in this paper, we conclude that aeolian abrasion of basaltic or sedimentary rocks on the Martian surface is an unlikely mechanism to produce methane concentrations detected by in situ observations from the MSL [Mars Science Laboratory] Curiosity rover and remote ground-based sensing observations,” the research team explains.

Curiosity Front Hazcam Right B image taken on Sol 2429, June 7, 2019.
Credit: NASA/JPL-Caltech

 

 

“Hence, we suggest that other sources of methane gas must be inferred to explain both the seasonal variations in background atmospheric methane and higher concentration plumes detected on Mars,” the researchers conclude.

 

 

 

 

 

 

 

To read the entire research paper – “Aeolian abrasion of rocks as a mechanism to produce methane in the Martian atmosphere” – go to Scientific Reports, a Nature Research journal at:

https://www.nature.com/articles/s41598-019-44616-2

 

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