Much breathless anticipation from the American Geophysical Union that we might have finally figured out how to look for life on Mars. But also reports that the first time we went there, we might have accidentally killed the Martians. Only accidentally, though; honestly, nobody really knows. It was, after all, the '70s.
Truth is, we don't really know how to look for life. We know how to look for Earthlings. If Rumsfeld were in charge of NASA, he'd no doubt point out that exobiology—and most of cosmology and astroscience—is full of "unknown unknowns." Scientists don't like to hear that, and so often use the inaccessibility of control groups in space science to make it up as they go along. Think of it as ad astra, ad hoc, ad nauseam. Having only one universe or one solar system is like trying to manage psychology with only one personality to study.
But what's the alternative to our definitely ignorant and possibly lethal searches for extraterrestrial life? We can't build probes that will look for things we don't know we should be looking for. The blind leading the blind, with doctorates in blindness.