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Searching for the 'real' waterworld (Forwarded)



 
 
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Old July 14th 03, 12:21 AM
Andrew Yee
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Default Searching for the 'real' waterworld (Forwarded)

ESA News
http://www.esa.int

9 July 2003

Searching for the 'real' waterworld

Science fiction writers and movie-makers have imagined a world completely
covered by an ocean, but what if one really existed? Would such a world support
life, and what would this life be like?

ESA could make science fiction become science fact when it finds such a world,
if the predictions of a group of European astronomers are correct. The ESA
mission Eddington, which is now in development, could be the key.

At the recent ESA co-sponsored 'Towards Other Earths' conference, nearly 250 of
the world's leading experts in planet detection discussed the strategy for
finding Earth-like worlds. Alain Léger and colleagues of the Institut
d'Astrophysique Spatiale, France, described a new class of planets that could be
awaiting discovery: 'waterworlds'.

According to Léger and his colleagues, these waterworlds would contain about six
times the mass of Earth, in a sphere twice as wide as our planet. They would
possess atmospheres and orbit their parent star at roughly the same distance
that the Earth is from the Sun. Most excitingly, an ocean of water entirely
covers each world and extends over 25 times deeper than the average depth of the
oceans on Earth.

A hundred kilometres deep

According to calculations, the internal structure of a waterworld would consist
of a metallic core with a radius of about 4000 kilometres. Then there would be a
rocky mantle region extending to a height of 3500 kilometres above the core's
surface, covered by a second mantle made of ice up to 5000 kilometres thick.
Finally, an ocean blankets the entire world to a depth of 100 kilometres, with
an atmosphere on top of this.

With twice the radius of the Earth, they will be easily spotted by the Eddington
spacecraft, which is designed to detect planets down to half the size of the
Earth. "A waterworld passing in front of a star, somewhat cooler than the Sun,
will cause a dimming in the stellar light by almost one part in a thousand.
That's almost ten times larger than the smallest variation Eddington is designed
to detect. So, waterworlds -- if they exist -- will be a very easy catch for
Eddington," says Fabio Favata, ESA's Eddington Project Scientist.

The CNES/ESA mission Corot, which is a smaller, precursor mission to Eddington
due for launch around 2005, may also be just able to glimpse them, if they are
close enough to their parent stars.

Origins of life

Scientists are now asking if such worlds could support life, and what would it
be like, especially since water is a prime ingredient for life on Earth. While
waterworlds seem to have everything to sustain life, there is a big question
mark over whether they could actually allow it to start in the first place.

One of the leading theories for life's origin in deep oceans is that it requires
hot springs on the ocean floor, heated by volcanic activity like the 'black
smokers' found here on Earth. On a waterworld however, 5000 kilometres of ice
separate the ocean floor from any possible smokers. On the other hand, a
water-surface origin may still be possible.

Perhaps the only way to know if anything lives on a waterworld will be to study
them with ESA's habitable-planet-finding mission, Darwin. When it launches in
around 2014, this flotilla of spacecraft will look for tell-tale signs of life
in the atmospheres of any planets, including waterworlds.

Related articles

* Eddington overview
http://www.esa.int/esaSC/120365_index_0_m.html
* Corot overview
http://www.esa.int/esaSC/120372_index_0_m.html
* Darwin overview
http://www.esa.int/esaSC/120382_index_0_m.html
* What is life, and how do we look for it?
http://www.esa.int/esaSC/SEM4TF9YFDD_index_0.html
* Looking for life of any shape or form
http://www.esa.int/esaSC/SEMS9BS1VED_exploring_0.html
* Chances of life are linked to water
http://www.esa.int/esaSC/SEMN3AR1VED_index_0.html
* How to find an extrasolar planet
http://www.esa.int/esaSC/SEMYZF9YFDD_index_0.html

IMAGE CAPTIONS:
[http://www.esa.int/export/esaSC/SEMR...xtreme_1.html]
Artist's impression of the surface of a waterworld. Credits: ESA - D.Neate

 




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