MICHELE NORRIS, Host:
From NPR News, this is All Things Considered. I'm Michele Norris.
MELISSA BLOCK, Host:
And I'm Melissa Block. For scientists, it's hard to think of a discovery that would be more exciting than finding life on Mars. Just to be clear, they aren't making that claim now. But scientists say the Red Planet is venting plumes of methane gas, which could be a sign of life, or maybe not. As NPR's Richard Harris reports, it's a puzzle that says, at the very least, Mars is not as dead as it might appear.
RICHARD HARRIS: Most methane on earth comes from living things, especially microbes, living in swamps, cows and termite guts, for example. So, scientists sat up and paid attention when astronomers found it on Mars a few years ago. Now, a study that Michael Mumma is publishing in Science magazine takes this business up a notch, a big notch.
MICHAEL MUMMA: We not only provided definitive detection of methane on Mars, but we also can quantify local sites where it is actively being released.
HARRIS: Methane isn't just circulating in trace amounts in the Martian air; it's actually burbling up from the ground, from a few specific locations.
MUMMA: And whether it's a single geyser or vent or an area of multiple vents, we really couldn't tell.
HARRIS: Mumma, who's at NASA's Goddard Space Flight Center, says, the methane is only coming out during the relatively warm summer months and only a tiny amount is emerging, about a pound of gas per second. That's more than enough for your stove but barely a wisp, when you think of being diluted in the entire Martian atmosphere. And the rock formation where it's emerging from is reminiscent of Earth's geology, which adds to the intrigue.
MUMMA: This is a very interesting region already because it suggests that conditions were right in early Mars at this site for biology to perhaps have originated, and now that we have found this to be a site of abundant methane release, this perhaps raises that possibility to a higher level.
HARRIS: The methane could conceivably be coming from microbes living below Mars' frozen surface. Or it could hypothetically be the Martian equivalent of fossil fuels laid down by Martian life forms millions of years ago, when the planet was more hospitable. But Mumma doesn't want to oversell these possibilities.
MUMMA: We must be extremely careful not to jump on a bandwagon of biology, exclusively for its production.
HARRIS: It's true that here on earth, methane is mostly the product of living organisms, but Christopher Oze says, it has other sources as well.
CHRISTOPHER OZE: I'd love to see life on Mars. I mean, everyone is just hoping to see life on Mars. But, you know, you have to go with what you know so far.
HARRIS: Oze is a geologist at Bryn Mawr College in Pennsylvania. He says, there are chemical reactions during mineral formation that can also generate methane gas. So, sure, it would be fantastic to prove that living organisms are the actual source.
OZE: But unless you find the bacteria doing something or some sort of fossil, you know, you just can't sort of play that card quite yet.
HARRIS: Whether the methane is coming from living organisms or from chemical reactions, Sushil Atreya, from the University of Michigan says, the findings suggest strongly that there is liquid water under the Martian surface.
SUSHIL ATREYA: Whether it's geology that's producing methane or it's biology - in either case, you require liquid water to do it. And that, I believe, in itself is a pretty exciting result.
HARRIS: Whatever the case, Mumma says, his findings suggest that there's stuff happening on Mars. If not actual life, well, at least some surprising and unexpected chemistry.
MUMMA: The idea of being able to actually sample the gases from the interior of an active planet other than Earth is actually extremely exciting.
HARRIS: A lander that's supposed to get to Mars in 2012 could solve the mystery, but only if it happens to touch down in a spot where the methane is actually burbling out from underground. Richard Harris, NPR News.