Protecting-Earth-from-the-Europa-Strain.doc

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Protecting Earth from the 'Europa Strain'
When future space probes bring samples from Europa, Ganymede, and certain types of comets and asteroids back to Earth, scientists must handle them carefully to avoid contaminating our planet with potentially dangerous microorganisms, according to a recent report from the National Research Council (NRC). Samples from other bodies will require less stringent safeguards, or in some cases, none at all.
(Europa is one of the likeliest habitats for life in our solar system. Cracks and discolorations in its surface ice hint that an ocean of liquid water may lie beneath. )
Last year, an NRC task group recommended that any samples returned from Mars be placed in strict isolation while scientists examine them for signs of life. The new report, issued July 15 by the NRC Task Group on Sample Return from Small Solar System Bodies, urges the same level of precautions for Europa, Ganymede, and some asteroids and comets.
The task group concluded that the Martian moons Phobos and Deimos, Jupiter's moon Callisto, and other comets and asteroids are less likely abodes for life, but samples from these bodies should still be handled with care. Samples from our own Moon, Jupiter's volcanic moon Io, and the surface layers of some comets are so unlikely to contain any form of life that they will require no special isolation, the report says.
Apollo astronauts and their lunar samples were isolated for up to several weeks upon their return to Earth, but no life was found in any of the Moon rocks. Because the Moon has no atmosphere, it is subjected to intense radiation from the Sun, which sterilizes its surface.