Earth Bugs Keen on Space Travel
For the first time, millions of bacterial spores have been purposely exposed to space, to see how solar radiation affects them and the results supported the idea that no only could life have arrived on Earth on meteorites, but that considerable material has flowed between planets.
Gerda Horneck of the German Aerospace Centre in Cologne and her colleagues used the Russian Foton satellite for an experient.
They exposed 50 million unprotected spores of the bacterium Bacillus Subtilis outside the satellite. UV radiation from the Sun killed nearly all of the spores,and did so even when the spores were confined under quartz.
To test if meteorites might protect bacteria on their journey through space, Horneck and her colleagues mixed samples of 50 million spores with particles of clay, red sandstone, Martian meteorite or simulated Martian soil and made small lumps a centimetre across.
Between 10,000 and 100,000 spores of the original 50 million survived and when mixed with red sandstone, nearly all survived, suggesting that even meteorites a centimetre in diameter can carry life from one planet to another, if they completed the journey within a few years.
Had the rocks been a meter across, bacteria could survive a long trip indeed.
Another team team ran computer models of giant impacts like Chicxulub. In the simulations, millions of large boulders were ejected from the earth. About 30 boulders from each Earth impact even reached Titan, and they entered Titan's atmosphere slower than most meteors hit Earth's atmosphere. "Those reaching Titan can aerobrake and drop their fragments onto the surface," says Gladman. Big Rocks from Earth have no doubt reached Enceladus as well.
"That kind of entry should be no problem" agreed Allan Treiman of the Lunar and Planetary Institute in Houston,quoted in New Scientist. Bacteria were found in weckage of the shuttle Columbia when it re-entered Earth's atmosphere in 2003. And Earthly lichen survived when exposed to the harsh environment of space.
"Early in the history of Mars and Earth, there could have been exchange of biological material between the two planets," agrees Benton Clark, a specialist at Lockheed Martin in Colorado.
Its starting to look like the Planets, when they were young, swapped a lot of spit and that rocks from the Earth, kicked out of the solar system by Jupiters gravity are carrying earth bacteria to other solar systems.
New Scientist, 11 January 2002