The Curiosity rover has looked for methane on the Red Planet and has found none, disappointing hopes for finding life—Earth’s main source of methane—on Mars.
Researchers had good reasons to pin their hopes for Martian life on methane. On Earth, living things, such as methanogenic microbes, wetlands, and cattle, release vast quantities of the stuff. Researchers thought that any methane found on Mars might have come from a living thing, too. Plus, in Mars’ atmosphere, methane would dissipate quickly, so any that they did find was likely to be fresh and might even indicate that its Martian producer was still alive.
In the last few years, research teams have reported small concentrations of methane on Mars. One team reported that the European Space Agency’s Mars Express mission, from 2004, had detected low concentrations of the gas. Another group reported detecting plumes of Martian methane using telescopes on Earth. Yet Curiosity’s Tunable Laser Spectrometer, the rover’s methane detector, did not confirm those findings. As reported on November 2, the methane detector let some Martian air into a mirrored chamber and fired lasers at it to see which frequencies of light it absorbed, looking for methane-specific absorption patterns. The researchers reported that they are 95 percent confident that methane levels lie between 0 and 5 parts per billion; if they repeated the experiment 100 times, they would expect to get results within that range for 95 of them.
Researchers will continue to look for life on Mars. The Curiosity team plan to try again to detect methane with the Tunable Laser Spectrometer, this time first removing the carbon-dioxide from the sample in order to concentrate any methane. The European Space Agency is planning to send up an orbiter in 2016 that will examine the gases in Mars’ atmosphere and look for methane, using a sensor that can detect methane concentrations as low as 14 parts per trillion, below Curiosity’s radar of 100 parts per trillion. So Curiosity’s initial negative results are unlikely to be the end of the search for Martian methane and the life that might produce it.
Image courtesy of Malin Space Science Systems/JPL-Caltech/NASA