The technology needed to send a robotic probe to another solar system is far in the future at best. But one scientist says it's not too soon to start thinking about how to avoid contaminating extrasolar planets with hitchhiking microbes from Earth.

Earth?s defences may need to be boosted against risk of potentially deadly microbes returning on space probes.

The author argues for the creation of an 'astroenvironmentalism' code that would guide our development of outer space resources to prevent space pollution.

The new era of \'sample return\' missions in space exploration has two downsides: \"back contamination\" - the risk that samples returned from other worlds such as Mars - just might - contain alien germs capable of turning into a worldwide plague, or at least wreaking havoc with the Earth\'s natural environment, and \"forward contamination\" - the possibility that spacecraft might contaminate the worlds they land on with Earth microbes, destroying scientifically priceless alien lifeforms before we even have a chance to study them.

Rocks and soil brought back to Earth from Mars by a future space mission should be handled as if they were chock full of deadly microbes, even though they will almost certainly prove lifeless, according to a panel of experts from the National Research Council.

A discussion of the policies and procedures NASA goes through to ensure that outgoing spacecraft do not contaminate planets with earth life.

NASA has had a long-standing effort underway in planetary protection. Not only is there an effort to make sure Earth biology isn?t clinging aboard spacecraft bound for such places as Mars. The space agency is also looking into ways to assure extraterrestrial samples don?t introduce any virulent and deadly alien life into our planet?s biosphere.

NASA is forming an internal 'planetary-protection' committee of about 15 people to determine the care and handling of extraterrestrial samples. They fear back-contamination by a Martian microbe that could create a true 'Andromeda Strain'.

Two strains of microbes from extreme environments on Earth appeared to survive a short flight through the vacuum and searing radiation of space, according to researchers at the University of Maryland. The experiment lends credence to the theory that primitive life might hitchhike between Earth and other worlds aboard debris from meteorite impacts.

Mautner, a senior research fellow at Lincoln University in Canterbury, New Zealand, advocates sending packets of freeze-dried microbial life cruising on solar sails through space, spreading the DNA of terrestrial life beyond Earth.