2000-01-13 | SCIENCE
Panspermia theoretically possible, say scientists
One the goals of astrobiology is to understand how life on Earth began. Astrobiologists are assessing a number of ideas, including the possibility that life originated elsewhere and migrated to Earth. This hypothetical process is known as panspermia.
Rocks from Mars have been hurled into space by asteroid impacts and eventually landed on Earth as meteorites. If single-celled organisms existed on ancient Mars, they might have survived within the rocks and colonized Earth. Conversely, asteroid impacts on Earth could have spread life to Mars.
As NASA states, one way to study whether meteorites from other planets "provide a mechanism for spreading life through the universe" is to calculate the amount of material that travels between planets over time (the mass transport rate).
Now, according to news reports from Yahoo!/Reuters and Yahoo!/AP a team of scientists has calculated that 5 trillion Martian rocks have arrived on Earth. They estimate that tons of material must have fallen on Earth, although only a few Martian meteorites have been found.
The researchers have also calculated the heat, radiation, pressure and acceleration that a microbe would have to survive as it traveled through space and entered the EarthÂs atmosphere. They conclude that at least two hardy species of Earth bacteria, Bacillus subtilisand Deinococcus radiodurans (nicknamed "Conan the Bacterium") could withstand the forces.
Extremophiles-- organisms that endure extremely harsh environments -- are a major focus of astrobiology.
The scientists conclude that single-celled organisms from Mars could theoretically have seeded the Earth with life, or vice versa. However, their calculations suggest that the transfer of microbes from one solar system to another is unlikely. If Earth life originated on another planet, it nevertheless began somewhere within our own solar system.
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from Yahoo!/AP, Jan 13, 2000
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