Jim Oberg wrote:

At the impact speeds of the particle collection,
it would be self-sterilizing to the nth degree.


In a PBS (USA) report, it was stated that the particles would be
"gently" captured by a special semi transparent foam (Aerogel I think
it is called). The vehicle would have been going at roughly the same
speed as the comet.

On the CBC (CANADA) tonight, they mentioned that the recovered vehicle
was in fact placed in a sealed environment and carried to Houston where
it would be opened in a super clean room environment to prevent any
contamination.

With regards to meteorites, they do not have heat shields designed to
keep their contents intact during re-entry. And if comets contain water
and as some would suggest some "organic materials" (which I assume to
mean elements normally found in organic materials), then protecting the
earth from then and vice versa would be important.