In a surprising and probably killer blow to the possibility of finding microbial life on Mars, Curiosity has reported that there’s no methane in the Martian atmosphere. New findings from Curiosity strongly suggest that previous observations from Earth, which indicated that there was actually quite a lot of methane on Mars, were false. With no methane, it is very unlikely that there’s life on Mars — or life as we know it, anyway.
From October 2012 to June 2013, Curiosity used its Tunable Laser Spectrometer (TLS) six times to search for traces of methane in the Martian atmosphere. The TLS works by sucking Martian air into a measurement chamber (pictured below), whereupon two infrared lasers are beamed through the sample of air. Depending on how the laser light is absorbed, a detector can work out the composition of the gas. In all six cases, the TLS failed to find any methane. Using its default configuration, the TLS can detect concentrations as low as 1.3 parts per billion — so it’s still possible that there is some methane on Mars, but at almost infinitesimal concentrations. If methane is present on Mars, we’re talking about the production of just 10 or 20 tons per year — about 50 million times less than the methane produced by life on Earth.
The reason this finding is so shocking is that previous analysis of the Martian atmosphere — from Earth and from Mars orbit — had pegged the methane concentration at up to 45 parts per billion in some regions, strongly indicating that there might be some kind of biological source on Mars. There can be other sources of methane, such as geology and ultraviolet degradation of organic compounds, but it would seem that none of these occur on Mars.
Scientists aren’t entirely sure how these previous observations ended up being so wildly different from Curiosity’s findings. There’s no way, as far as we know, in which methane could’ve quickly escaped the Martian atmosphere. “Methane is persistent. It would last for hundreds of years in the Martian atmosphere,” said Sushil Atreya of the University of Michigan, co-author of the new research. “Without a way to take it out of the atmosphere quicker, our measurements indicate there cannot be much methane being put into the atmosphere by any mechanism, whether biology, geology, or by ultraviolet degradation of organics delivered by the fall of meteorites or interplanetary dust particles.”
The TLS is now being reconfigured to specifically detect methane, increasing its sensitivity to below one part per billion. If there’s any methane on Mars at all, the reconfigured TLS will detect it. At this point, though, it looks increasingly likely that there’s no life on Mars — or, if there is, it’s unlike any life here on Earth.
In other news, Curiosity is still trundling its way across Mars, en route to its final destination: Mount Sharp. Curiosity recently turned on its autonomous driving software, allowing it to cover more ground each day. The rover has also captured a bunch of cool photos, such as the Martian moon Phobos eclipsing the Sun.