What are the odds that one of the working orbiters could image some of the other Mars robots still in orbit, such as Mariner 9 and Viking 1 and 2 and maybe even the Mars 2, 3, and 5 probes, if they are still up there?

I know they had to remain in space for 50 years or so (at least the US ones) to knock off any microbes on them to keep from contaminating the surface. Which begs the next question: Could the average Earth microbes that likely hitched a ride on those probes actually survive on the Martian surface, assuming they even survive the atmosphere entry and crash landing?

On a related note, did the 1992 Mars Observer remains crash into Mars or sail on into solar orbit?