Date
15 December 2017
NASA's Curiosity rover, which landed on Mars in August 2012, has detected short-lived spikes in methane levels over a 60-day period. Illustration: NASA Jet Propulsion Laboratory
NASA's Curiosity rover, which landed on Mars in August 2012, has detected short-lived spikes in methane levels over a 60-day period. Illustration: NASA Jet Propulsion Laboratory

Methane discovery: evidence of life on Mars?

NASA’s Curiosity rover has detected methane in the atmosphere of Mars, which could indicate life on the planet — either today or in the distant past.

The discovery, announced at the American Geophysical Union meeting in San Francisco on Tuesday, is quite intriguing.

On Earth, 95 percent of the gas comes from microbial organisms, according to BBC News. That implies that where there’s methane, there could life. (Methane’s chemical symbol is CH4, which stands for one atom of carbon and four atoms of hydrogen.)

But Space.com says that methane on the Red Planet could also have come from nonbiological sources such as comets, degradation of interplanetary dust particles by ultraviolet light, and interaction between water and rock.

But it could also have come from Martian bugs, the BBC says.

So far the Curiosity team has not detected the source of the methane on the planet.

The rover, which landed in Mars’ Gale Crater in August 2012, initially did not find any trace of methane in the region.

But it later detected short-lived spikes in methane levels over a 60-day period. During that time, the levels of methane in the planet’s atmosphere rose from 0.7 parts per billion up to 7 parts per billion, but the gas quickly faded to infinitesimal levels.

The rover’s weather station suggests that the gas is blowing in from the direction of the crater rim, and that could mean it is being released either within the crater or just outside.

Sushil Atreya, a member of the Curiosity research team, said it’s possible that “clathrates” are involved.

“These are molecular cages of water-ice in which methane gas is trapped. From time to time, these could be destabilized, perhaps by some mechanical or thermal stress, and the methane gas would be released to find its way up through cracks or fissures in the rock to enter the atmosphere,” the University of Michigan professor told BBC News.

The question, of course, is how methane entered the clathrate beds in the first place.

One way to know whether the methane on Mars has a biological or geological origin is to study the types, or isotopes, of carbon atom in the gas.

On Earth, life favors a lighter version of the element (carbon-12), over a heavier one (carbon-13), according to the BBC report.

If scientists could find similar evidence on Mars, that would buttress the idea of life on the planet.

However, the volumes of methane detected by Curiosity are just too small for researchers to be able to make this determination. They could wait for another one of those peaks in methane release to get a sufficient sample and enrich it.

Another major announcement by the Curiosity team in San Francisco is the detection of organic (carbon-rich) compounds in the rock samples it has been drilling.

It is the first definitive detection of organics in surface materials on Mars.

The discovery, by itself, doesn’t automatically point to life on the plant because there are plenty of nonbiological processes that can also produce complex carbon structures, says the BBC.

Still, says Curiosity project scientist Prof. John Grotzinger: “It’s a big day for us – it’s a kind of crowning moment of 10 years of hard work – where we report there is methane in the atmosphere and there are also organic molecules in abundance in the sub-surface.”

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CG

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