[FPSPACE] Fw: ESA: Was Venus Once a Habitable Planet?

[LARRY KLAES]

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-----Original Message-----
From: "AAS Press Officer Dr. Rick Fienberg" <rick.fienberg at aas.org>
Date: Thu, 24 Jun 2010 11:54:50 
To: <Rick.Fienberg at aas.org>
Subject: ESA: Was Venus Once a Habitable Planet?

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 rick.fienberg at aas.org, +1 202-328-2010 x116.
 
 ** Contact data are at the end. **
 
 24 June 2010
 
 Article and images:
 http://www.esa.int/esaSC/SEMQ9OLZLAG_index_0.html
 
 WAS VENUS ONCE A HABITABLE PLANET?
 
 ESA's Venus Express is helping planetary scientists investigate
 whether Venus once had oceans. If it did, it may even have begun its
 existence as a habitable planet similar to Earth.
 
 These days, Earth and Venus seem completely different. Earth is a
 lush, clement world teeming with life, whilst Venus is hellish, its
 surface roasting at temperatures higher than those of a kitchen oven.
 
 But underneath it all the two planets share a number of striking
 similarities. They are nearly identical in size and now, thanks to
 ESA's Venus Express orbiter, planetary scientists are seeing other
 similarities too.
 
 "The basic composition of Venus and Earth is very similar," says Hakan
 Svedhem, ESA Venus Express Project Scientist. Just how similar
 planetary scientists from around the world will be discussing in
 Aussois, France, where they are gathering this week for a conference.
 
 One difference stands out: Venus has very little water. Were the
 contents of Earth's oceans to be spread evenly across the world, they
 would create a layer 3 km deep. If you were to condense the amount of
 water vapor in Venus's atmosphere onto its surface, it would create a
 global puddle just 3 cm deep.
 
 Yet there is another similarity here. Billions of years ago, Venus
 probably had much more water. Venus Express has certainly confirmed
 that the planet has lost a large quantity of water into space.
 
 It happens because ultraviolet radiation from the Sun streams into
 Venus's atmosphere and breaks up the water molecules into atoms: two
 hydrogens and one oxygen. These then escape to space.
 
 Venus Express has measured the rate of this escape and confirmed that
 roughly twice as much hydrogen is escaping as oxygen. It is therefore
 believed that water is the source of these escaping ions. It has also
 shown that a heavy form of hydrogen, called deuterium, is
 progressively enriched in the upper echelons of Venus's atmosphere,
 because the heavier hydrogen will find it less easy to escape the
 planet's grip.
 
 "Everything points to there being large amounts of water on Venus in
 the past," says Colin Wilson, Oxford University, UK. But that does not
 necessarily mean there were oceans on the planet's surface.
 
 Eric Chassefiere, Universite Paris-Sud, France, has developed a
 computer model that suggests the water was largely atmospheric and
 existed only during the very earliest times, when the surface of the
 planet was completely molten. As the water molecules were broken into
 atoms by sunlight and escaped into space, the subsequent drop in
 temperature probably triggered the solidification of the surface. In
 other words: no oceans.
 
 Although it is difficult to test this hypothesis it is a key question.
 If Venus ever did possess surface water, the planet may possibly have
 had an early habitable phase.
 
 Even if true, Chassefiere's model does not preclude the chance that
 colliding comets brought additional water to Venus after the surface
 crystallized, and these created bodies of standing water in which life
 may have been able to form.
 
 There are many open questions. "Much more extensive modeling of the
 magma ocean-atmosphere system and of its evolution is required to
 better understand the evolution of the young Venus," says Chassefiere.
 
 When creating those computer models, the data provided by Venus
 Express will prove crucial.
 
 ESA PIO Source:
 Markus Bauer
 ESA Communication and Knowledge Department
 +31 71 56 56799
 markus.bauer at esa.int
 
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