Deflating, at least for now, hopes of microbial life forms inhabiting the soils of Mars, NASA's rover Curiosity has so far come up empty in its search for the gas methane. At a NASA news conference on Friday, scientists reported that the Mars rover's instruments had seen no signs of methane, which, had it been there, would have signaled that there might currently be methane-exhaling microorganisms on Mars that are similar to those found on Earth. In Martian air, methane molecules are broken down by sunlight and chemical reactions within a few hundred years. Thus, when three teams of scientists reported in 2004 that they had detected methane there, it raised the possibility that something on present-day Mars was creating methane, and the most exciting possibility was tiny life forms.
This article originally appeared in The New York Times.