A Million Wasted Years

From the BBC, "Earth could seed Titan with life":

Dr Gladman's team calculated that up to 20 terrestrial rocks from a large impact on Earth would reach Titan. These would strike Titan's upper atmosphere at 10-15 km/s. At this velocity, the cruise down to the surface might be comfortable enough for microbes to survive the journey.

But the news was more bleak for Europa. By contrast with the handful that hit Titan, about 100 terrestrial meteoroids hit the icy moon.

But Jupiter's gravity boosts their speed such that they strike Europa's surface at an average 25 km/s, with some hitting at 40 km/s. Dr Gladman said other scientists had investigated the survival of amino acids hitting a planetary surface at this speed and they were "not good".

"It's frustrating if you're a microbe that's been wandering the Universe for a million years to then die striking the surface of Europa," Dr Gladman said.

Asked after his presentation by one scientist whether he thought microbes would be able to survive Titan's freezing temperatures, Dr Gladman answered: "That's for you people to decide, I'm just the pizza delivery boy."

These are interesting theories and all, but the whole idea of microbes' surviving a massive planetary impact, then surviving a launch into interplanetary space, then surviving hundreds of thousands of years at near absolute zero, bathed in radiation, then surviving atmospheric reentry . . . doesn't it strain credibility just a tad? I know life is tenacious, but microbes could colonize a planet after that?