In 2003, three independent groups reported detecting methane in the atmosphere of Mars. Whether the reported methane is from microbes eking out a living beneath the surface or from deep stirrings of the geologically moribund planet, no one can say. Either prospect would excite scientists, but only martian biology could rejuvenate a troubled NASA Mars program. The first group reported that they had detected a few tens of parts per billion by volume of martian methane. They found it by reading the squiggly lines of infrared spectra recorded by ground-based telescopes. Two other independent groups backed up that work with their own reported spectroscopic detections. But some planetary scientists now see no credible signs that there ever was any methane on Mars.