This is one of the ongoing problems of an eventual discovery of Life on Mars.

It's been known for a generation that terrestrial microbes can survive under Martian surface conditions. Claims have been made that some of these microbes could flourish.

This flies in the face of those who insist that the surface of Mars is self-sterilizing what with all its susposed hyper-oxidants and fierce ultra-violet baths and so forth.

But the problem was recognized long ago: if terrerstrial organisims can survive under Martian conditions (they can -- although this story minimizes that idea), then unless all terrestrial landers are fully sterilized before launch, they run the risk of contaminating the Martian surface with terrestrial biology -- which then might be "discovered" and mis-identified as native Mars biology.

Terrestrial craft have been crashing into and landing on the Martian surface since the 1960's. Only the twin Viking Landers were sterilized, and some say it wasn't a thorough enough job.

Do we have any way at all to be sure any biology that is ever found on Mars is "native" Martian? If not, then the argument over origins will continue indefinitely, with one camp claiming a terrestrial origin, the other camp claiming a native Mars origin, and the mediators splitting the difference with an appeal to Panspermia.

More generations of Mars controversy! Whoo-hoo!