I mean, there's frozen water on the moon. H2o and energy is really all that's required. And we can bring LOTS of energy (nuclear reactors are pretty tiny now). A great time to be alive boys.
If you define "freaky" as any fossil on Mars, I'd say closer to 100%. In not talking about even microbes, but even smaller - bacterial perhaps. We know there has been liquid water on the planet. Look at the crazy shit we've found on our own planet where we previously thought life couldn't exist. Specifically the bacterial and microbial life in completely anaerobic but aquatic systems around the thermal vents.