Oh sure, there are all sorts of bacterial spores that just hang on for dear life in the harshest of environments. Who knows. I wouldn't put it past them to survive in space.
In my opinion, duration of the exposure to radiation would be the biggest hurdle. A few decades is one thing but billions of years is another thing altogether.
One of the later Apollo mission took a swab from a piece of equipment that had been left from one of the earliest Apollo missions. It had been exposed to unfiltered sunshine, solar wind, and cosmic rays for about 3 years. It cultured positive for stapholococcus. I have bugs in my nickel plating tank at PH 3.5 that would do just dandy in a hot spring on Mars. Life will find a way.