In “Could free-floating ‘nomad’ planets carry seeds of life in the universe?” (Christian Science Monitor , February 24, 2012), Pete Spotts reports,
A ‘nomad’ planet of the right mass, with the right atmosphere, and some source of heat – perhaps radioactive decay or tectonic activity – could allow for life either on the surface or underground.
While most of the nearly 800 planets discovered since the mid-Nineties orbit stars,
Since 2000, however, astronomers have discovered planets with no obvious stellar home. A group of Spanish astronomers reported that year discovering planets ranging from five to 15 times Jupiter’s mass free floating in a cluster of young stars in the constellation Orion. Last year, two groups of astronomers jointly announced the discovery of 10 Jupiter-class planets, the vast majority free of the grip of any host star. The results appeared last May in the journal Nature.
Researchers differ as to how these untethered planets got started, but some suggest that they could ferry life to other planets:
Collisions with other objects might knock off bacteria-laden chunks that could be available to land on some more-hospitable planet.
Sunless planets were in search of a headline until this thesis came along. It’s interesting for what it leaves out: How would life get started in such an unfavourable environment? Most theorists clash over favourable environments.
(It’s true that nematode worms survived the space shuttle blowup, but they already existed. No one expected them to get started that way.)
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