Bringing Life From Mars

"If you can't bring a rock back you are not going to be able to bring people back. There's a real feeling that bringing samples back from Mars is absolutely essential if we are going to continue our Martian exploration programme."

The mission would involve the launch of two separate craft from Earth - a "lander composite" and an "orbiter composite". Both would make the trip to Mars, where the lander would touch down on the surface. It would then release a rover which would collect a variety of rock samples totalling around half a kilogram.

It would bring these back to the lander, where the rocks, plus a sample of Martian atmosphere, would be encased in a sealed pod within the so-called Mars Ascent Vehicle - part of the lander composite. This would then blast off from the surface and dock with the orbiter before transferring its precious cargo. The orbiter would then return to Earth, enter the atmosphere and land. At this point, scientists would rush in and transfer the samples to a top-level biosecurity lab, where they would be analysed for any possible signs of life.

"There's a big caveat when you start playing with Mars, and that's planetary protection. You have to be very careful not to bring anything back that might be harmful to Earth," he said. "Your mission has to be guaranteed, and I really mean guaranteed, to get into the Earth's atmosphere without damaging itself."

If Martian microbes do exist they must be extremely hardy, having survived the planet's freezing, desiccating surface and bombardment with UV radiation, so if the returning spacecraft blew up on re-entry scientists could not be sure that Martian life forms on board would be destroyed in the blast. It would also be impossible to know what they would do to life on Earth.