he researchers attached the baseball-size rock to the outside of the European Space Agency's Foton M3 spacecraft to test whether biological material could survive the round-trip journey.

Sculpted from stone from the Orkney Islands in northern Scotland, the rock contained fossilized microbes and the molecular signatures of microbes.

"In the bit of rock we got back, some biological compounds have survived,

Preliminary findings suggest that it's possible simple organisms could arrive via meteorites, he said.