AAAG! I killed it:

Two NASA space probes that visited Mars 30 years ago may have found alien microbes on the Red Planet and inadvertently killed them, a scientist is theorizing.

The Viking space probes of 1976-77 were looking for the wrong kind of life, so they didn't recognize it, a geology professor at Washington State University said.

NASA's sending a new probe to Mars later this year, and they've already expressed interest in trying to test the predictions this guy is making about what Martian life actually looks like. Of course, since the probe is already built, they'll have to figure out a way using existing tools. Something to keep an eye on, if nothing else.