Passing Gas on Mars

Methane gas is periodically detected in the atmosphere of Mars. This was once considered implausible and perplexing, but it is now widely accepted by planetary scientists. Why the methane is there is still a mystery. It could point to present-day Martian microbes living in the rocks below the surface.

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Scientists working with the ESA’s Mars Express orbiter reported that in the summer of 2013, the spacecraft detected methane within Gale Crater, a 96-mile-wide depression near the Martian equator.

In the same summer of 2013, NASA’s Curiosity rover also measured a marked rise of methane in the air that lasted over two months.

The presence of methane is significant because the gas decays quickly. Calculations indicate that sunlight and chemical reactions in the thin Martian atmosphere would break up the molecules within a few hundred years, so any methane detected must have been created recently.

It could have been created by a geological process known as serpentinization, which requires both heat and liquid water. Or it could be a product of life, specifically methanogens, microbes that release methane as a waste product. Methanogens thrive in places lacking oxygen, such as rocks deep underground and the digestive tracts of animals.

Even if the source of the methane turns out to be geological, the hydrothermal systems that produce the emissions would still be prime locations to search for signs of life.

A newer European Mars spacecraft, the Trace Gas Orbiter, which has a more sophisticated methane detector, has been in orbit since 2017, but no results have been reported as of yet.

New Clues for Life on Mars

NASA’s Curiosity rover detected a strange burst of methane gas in the atmosphere on Mars, along with other organic chemicals in rocks on the planet’s surface. These findings are raising new questions about the planet’s habitability today as well as in the past.

Using its onboard Sample Analysis at Mars (SAM) laboratory, the rover “sniffed” more than a dozen samples of the Martian atmosphere over a 20-month period. Grotzinger and his team found that methane levels shot up tenfold to an average of seven parts per billion over two months in late 2013 and early 2014, according to NASA.

The researchers aren’t sure what caused the burst, but they’ve offered two potential explanations: an interaction between water and rocks called serpentization, or methane-belching microbes. Anaerobic bacteria produce around 95 percent of the methane on Earth.

Curiosity found other organic (carbon-containing) molecules in powder collected from drilling into an ancient rock called Cumberland.

The researchers say this is the first definitive evidence of organics found on the surface of Mars. While the presence of organics doesn’t prove that life existed on ancient Mars, it suggests the planet may have had the ingredients required for life.

A paper describing the detection of methane was published online on Dec. 16 in the journal Science.