Crash testing bacteria for space travel

[Plazma Inferno!]

BYU Chemistry professor Daniel Austin and his graduate students are learning just how hard it can be to kill bacteria.
The research group, funded by NASA, is studying high velocity impact of bacterial spores. More specifically, the group is trying to find the speed limit above which bacteria won’t survive when they crash into a hard surface.
To test velocity, bacteria are loaded into a vacuum chamber and then launched by a blast of air at speeds nearing 300 meters per second.
Although the main focus of the research is answering the question of how much force the bacteria can withstand, NASA has funded the research because of the planetary protection implications of the study: if bacteria can survive the ejection from one planet and the impact of landing on another planet, there are potential concerns about cross contamination of bacteria between those planets. However, Austin is quick to acknowledge that there are other factors, like UV light, that may kill the bacteria in transition.

http://news.byu.edu/news/crash-testing-bacteria-byu-chemists-try-find-fatal-limit

 

[Q-reeus]

...if bacteria can survive the ejection from one planet and the impact of landing on another planet, there are potential concerns about cross contamination of bacteria between those planets...

Potential concerns? Implying what? That perhaps 'we' could somehow act in a preventative capacity? And this potential cross-contamination scenario has been in place across the universe for how many billion years? Doesn't qualify as natural? Slow news day in some parts I guess.
As far as killer impact velocities go, sorting out 'pure' impact in vacuum chambers from being debris caught up in an atmospheric shockwave front with all sorts of complicated fluid physics etc. going on seems like a lifetime long-haul project for some backroom nerds. Typical of certain 'applied science' academia.