What MAY have been found was fossils, a claim which is under intense debate in the astronomical community. As for a possible contamination of Mars by microbes carried by the Viking Lander in 1976, there is a small but finite chance that this is possible. In fact, this contamination issue is the main reason why we should NOT send humans to Mars until robotic scouts have confirmed that there is absolutely no indigenous life under the surface of Mars, in locals that some terrestrial micro organism might conceivably invade after humans leave. We now know that earth microbes live in boiling hot water near underwater geothermal vents, and deep inside the crust. bacteria seem to be phenomenally resourceful. If there is a source of energy, they will find ways to harness it, but whether terrestrial organisms could 'instantaneously' survive on Mars, to me, is an open book! But an easy one to test in terrestrial vacuum chambers.