Original URL: http://www.theregister.co.uk/2009/06/11/gliese_581_not_habitable_after_all/

Boffins: Bebo interstellar spam aliens don't exist after all

Gliese 581d 'too crusty' for civilisation to arise

By Lewis Page

Posted in Science, 11th June 2009 14:21 GMT

Astroplanet boffins in America say that humanity may not, as had been expected, soon be the target of an interstellar assault from alien civilisations unwisely enraged by Web-2.0 teenybopper portal Bebo. It appears that the planet Gliese 581d - which might have mounted an invasion of the Solar System as soon as 2049 - cannot after all support life.

Regular Reg readers will doubtless recall that the red dwarf star Gliese 581, located 20.3 lightyears off in the constellation Libra, is considered one of the closest known locations which might be home to an alien race of the same general type as humanity. This is because boffins have at different times assessed that either the third or fourth planet of the system lies at such a distance from its dim, red sun as to permit the existence of liquid water on its surface.

Liquid water is relatively rare stuff in the universe, most places being icy cold or steamy hot, but it is regarded among boffins as an essential prerequisite for the appearance of life along Earthly lines - the general class of possible life which would be of most interest to us humans. Hence the general boffinry preoccupation with liquid water off Earth, and the resulting interest in the Gliese 581 system.

So great has this interest been that last October, in a cunning publicity stunt, the powers behind Bebo decided to compile a large multimedia package composed by the site's userbase and beam it at Gliese 581 from a rented Ukrainian radiotelescope controlled by controversial "active SETI" proponent Alexander Zaitsev.

The interstellar Bebo spamgasm may prove embarrassing for the human race should it ever be picked up. As one might expect, it consists primarily of material related to the amusing antics of cats, boy crooners and other matters of interest only to mental cripples. There is also a large selection of text messages ("Hi im nicole, i would love to appear on the west end stage in a hit show.i also wouldnt mind doing a few television programs. anyway laters.Nicole x").

Indeed, as of April it appeared that the human race might suffer worse than just embarrassment as a result of the ill-judged interstellar missive. At that time, boffinry opinion held that Gliese 581d was actually an oceanic planet, possibly host to a ravening, self-mothered pseudohydrozoan immortal Dr Who jellyfish clone vampire blobomination horror-swarm of the type already found (in diminutive form, fortunately) in the oceans of Earth. Even if the jellies were actually peaceful, it seemed unlikely that they would remain so after the Bebo spam-blast struck their system in the year 2029.

Gliese 581: The Crustening

However it now seems that in fact Gliese 581d is liable to be lifeless after all. New boffinry suggests that there are other requirements for a life-bearing world than simply being in a star's liquid water zone.

Astro brains in America now say that there is also a requirement that plate tectonics must be taking place on such a world - that is, that the planetary crust must be broken up into mobile bits, causing a certain number of volcanoes, earthquakes and so on. Apparently this is necessary "to pull excess carbon from its atmosphere and confine it in rocks to prevent runaway greenhouse warming".

"If you have plate tectonics, then you can have long-term climate stability, which we think is a prerequisite for life," says Rory Barnes, astro boffin at the University of Washington.

Energy to drive the necessary tectonics can come from radioactive decay within a planet. However it is also driven by tidal forces exerted on a world by another body, as in the case of the tides generated on Earth by the Moon. Where an overly close star or giant planet such as Jupiter generates such forces, they don't merely cause water to slosh about - they also wrack and twist the very planetary crust itself, perhaps causing the place to be uninhabitably plagued by liquid hot molten magma, collapsing mountains and so forth. This happens on Jupiter's moon Io, for instance.

In the case of Gliese 581d, from which Bebo-outraged aliens might retaliate by extirpating the race which could emit such awfulness, it seems fortunately that the tidal forces are probably unsuitable for life.

"Our model predicts that tides may contribute only one-quarter of the heating required to make the planet habitable, so a lot of heat from decay of radioactive isotopes may be required to make up the difference," says Brian Jackson of Arizona Uni, a colleague of Barnes.

Provided that Gliese 581d isn't unusually radioactive, then, there shouldn't be any possibly-irritable aliens there. If it is, of course, we're looking at potentially ill-tempered radioactive mutated aliens who might also be superhumanly strong. (Surface gravity is liable to be a lot more than that of Earth, as Gliese 581d is 7 times Earth's mass.)

Truly, this Web-2.0 stuff is a very bad and dangerous thing. Will the human race realise in time?

There's more from the University of Washington here, including a free link to the relevant scholarly paper. ®