Scientists in Switzerland are sending bacteria into space to find out whether life on Earth could have started on another planet.
Biologists in Lausanne will test the theory later this month when they send bacteria-filled rocks into orbit aboard a Russian satellite.
If the harmless spores of Bacillus subtilis survive re-entry into the Earth's atmosphere, the biologists say it will prove that life could have extraterrestrial origins.
Tests on Earth have already revealed that bacteria can survive many aspects of an interplanetary flight.
Dangers in space
It has long been suggested that living organisms could have travelled around the early solar system, ferried by rocks that were blown off one planet before landing on another.
A number of experiments have already been conducted in Lausanne to see if bacteria could have survived the dangers of space travel.
Hitching a ride on a meteorite would have exposed them to acceleration, deceleration, radioactivity, UV light, intense cold and shock waves.
"Every kind of danger which could happen in space has been tested in the past apart from re-entry," said microbiologist Claude-Alain Roten at Lausanne University, who is leader of the bacterial experiment.
"Just by using ballistic systems, we could see that bacteria are able to endure 100,000Gs, which is a huge acceleration.
"If they can survive that, they can survive the acceleration when a meteorite is launched from one planet to another one.
"With the Swiss defence department, we also measured bacteria's survival in an explosion."
The latest mission is scheduled to launch from Plesetsk, north of Moscow, on October 15.
Two hollowed-out stones attached to the exterior of the satellite will be carrying bacteria.
Roten admitted that analysing the bacteria - should it survive re-entry - would not be conclusive proof that life appeared on other planets.
However, it would confirm whether terrestrial life could have emerged in another part of the solar system or even in another part of the galaxy.
"We'll have our proof if we can get Martian samples in ten years and analyse them and see if they are holding bacteria fossils," he told swissinfo.
"If the fossils have the same kind of biochemistry as terrestrial biochemistry, it would be a full proof of the theory.
"Another way to see if the theory is correct would be to analyse the atmosphere of extra solar terrestrial planets.
"If we can find planets with an atmosphere similar to that of the Earth, it is a very strong signal that on these planets there must be something similar to life."
Dozens of experiments, devised by researchers from other countries, will also be performed during this mission.
Scientists will analyse the results of the experiments when the satellite returns to Earth after a fortnight.
swissinfo, Vincent Landon
Bacteria sent into orbit aboard Russian satellite.
Survival could confirm extraterrestrial origins of life.
Study devised by Lausanne scientists.