On the other hand say the researchers, even if a small fraction of the stowaways survive on Mars, it's possible that they could rapidly "play the numbers," perhaps like their early Earth ancestors. Relying on quickly trying out a plethora of genetic mutations the bugs might come up with a new survival strategy in short order.
The makeover could be so extreme that it would really be a Genesis II, the origin of a new form of life on another world, say the researchers.
Ironically, I'd say that this line of reasoning leads inevitably to the conclusion that Mars must already be inhabited with native organisms that arose at the same time life appeared on Earth, and were genetically agile at adapting to a dying Red Planet.
Therefore, stranded Earth microbes might compete with Mars microbes for resources. We'd introduce a shadow biosphere on the Red Planet; where completely different form of life co-exists.
Contaminating Mars with Earth organisms, "might not be an experiment we ethically want to conduct, but it would be an unparalleled experimental result," the authors conclude.