I assume that the investigating scientists familiar with the project have reasons to conclude that the bacterial fossils definitely originated from Mars, given that:<p>&#62; <i>The stones are known to be from Mars because gases trapped inside them match those in rocks examined by probes on the red planet. They were blasted out of its surface by asteroid impacts and then drifted around the solar system for millions of years before falling to earth.</i><p>I would tend to more conservatively conclude, "some meteorites resembling Martian rock have been found to contain fossil evidence of bacteria."<p>i.e., it is also possible that the rock was contaminated while in space, or that it didn't even originate from Mars, but from conditions which simulated Mars.<p>I'd love to hear definitive proof of life, or former life, on Mars.