“Life on Mars” exclaimed the British tabloid the Sun in a headline this morning, reporting on the detection of seasonal methane gas in the atmosphere of Mars. The journal Science, in which atmospheric scientist Michael Mumma describes his discovery this week, then decried the Sun for nearly breaking an embargo on the news. “In the interests of supporting excellence in science communications,” an email from the journal’s publishing society states, “we urge all registered journalists in good standing to adhere to the Science embargo-release time, and refrain from validating this unfortunate tabloid teaser.”

Let’s slow down a bit, both of you. First off, methane doesn’t necessarily mean life. Yes, on Earth, atmospheric methane is mostly the work of cows, and microbes in the soil can also burp up the stuff. But on Mars, biology is not necessarily any more likely as a source of methane than geology, since water can create methane by breaking down certain volcanic minerals. What’s interesting about the methane discovery is that there could potentially be a lot of it. Mumma, of Goddard Space Flight Center in Greenbelt, Maryland, claims to have discovered variability in the methane concentrations in both space and time. Methane would normally mix and breakdown in the atmosphere over time. But Mumma, using Earth-based telescopes, spotted seasonal plumes of methane concentrated in hotspots: it implies the work of tens of thousands of cows, or their geological equivalent.

As far as the embargo break, in this case it’s a little silly to complain about it. Both Nature and Science try to enforce strict embargoes on their journal articles to create news events. But science is a slow process, with as many zigs and zags as eurekas. And Mumma has been talking about his methane work for years. In fact, I wrote about this methane discovery in October, after Mumma gave a talk at a conference at Cornell University.

For me, the more interesting question is: Will NASA switch its Mars exploration mantra from “follow the water” to “stalk the methane”? The Mars Science Laboratory, due for launch in 2011, is equipped with an instrument that can detect methane at levels of parts per trillion. But a potential landing site, in the same region as one of Mumma’s hotspots, was thrown out of consideration months ago. Time to reconsider? “Now we’ve got these little signposts saying: ‘Look, here I am. Come here!’” Mumma told me in October.

Image: USDA/Keith Weller