Extraterrestrial Life

We Found a Methane Spike on Mars That Could Be Life — or Something Else

Did the Curiosity rover find evidence of life? While we don't know for sure, what we can say is the rover did catch a spike of methane. That's a compound that's sometimes associated with things like rock-water interactions or volcanic eruptions — but here on Earth, it's also associated with microbial life.

Mars Methane's Measuring Mess

We know there are methane emissions on Mars already, but how much is a subject of considerable debate. Decades of observations of the Martian atmosphere have revealed wildly different measurements of methane from year to year and from spacecraft to spacecraft. After Curiosity landed, it was thought that perhaps the rover could get some "ground truth," but it's also finding some strange variations.

The latest measurement showed a volume of about 21 parts per billion units by volume (ppbv). A single ppbv means that in a given volume of air on Mars, a billionth of that volume is methane. It's a small amount by any standard, but it's the largest amount of methane that Curiosity has ever measured. It could be recent, or it could be old. It could be from biology, or it could be from geology. It will take a lot more dedicated work — and probably some help from other spacecraft — to learn more.

What we're learning is that measuring methane is complicated. There is some part of it that might be related to seasonal change on Mars, Curiosity found. But some of the measured methane seems to be spiking more randomly and in a different pattern than seasonal change. Nobody is sure how long these "transient plumes," as NASA calls the random methane spikes, last or why they're so different.

Could Mars Host Life?

This methane "problem" has an even more thorny root — can Mars actually host life? At first glance, there seems to be a difficult environment for microbes. Mars has a dusty surface with little water, unless you count ice at the poles and underwater reserves. It's baked by radiation and very cold, especially during the winter and at night.

But there could be pockets of life in unusual areas. As we mentioned, scientists have found hints of underground lakes that are sheltered from the surface, perhaps providing a small pocket for life. Another possibility is a strange feature known as recurring slope lineae, which are dark streaks that appear on the sides of craters — although later results suggested that they aren't water streaks, but dust.

We're not counting Mars out in terms of life, however. A forthcoming NASA mission called Mars 2020 is getting ready to pick up promising samples for a return to Earth at some point, while a European rover called Rosalind Franklin is expected to search in detail for organic materials (the compounds of life) on the surface. It won't be long before these missions get going, as both of them are launching next year. What they find could change our perception of Martian biology forever.

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Written by Elizabeth Howell June 26, 2019

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