Alien World May Have Seas Like Earth

Space scientists have identified the first planet around another star that could have conditions making it a suitable home for alien life. The rocky world – which lies right in our cosmic backyard – may have an atmosphere, oceans, clouds and rainfall. 

Artist's impression of planets orbiting a red dwarf (ESO)

Astronomers say it appears warm and wet enough for life to exist. It lies in a so-called Goldilocks zone around its home sun that is not too hot and not too cold for liquid water.

The planet orbits a red dwarf star called Gliese 581 that is only 20 light-years away from Earth, making it one of the closest stars known. Any inhabitants would be bathed in a constant red twilight, says experts.

Scientists had already discovered up to six planets in orbit around Gliese 581 and given them letters to distinguish between them.

Last year they revealed that one, dubbed Gliese 581g, was a similar size to Earth and close to the habitable region. Since then, others have questioned whether that world even exists.

However they have no doubt about the esistence of the new candidate for a home for aliens, Gliese 581d.

It is around twice the size of Earth and around seven times as dense, according to British planetary scientist Dr Robin Wordsworth and his French science team.

They carried out computer modelling of the planet to test what sort of physical conditions could be found there and discovered it could have a dense carbon dioxide atmosphere that would store heat and allow seas and rivers to exist.

Though the air would be poisonous to humans, it might be breathable to alien lifeforms which had evolved differently to us.

Dr Wordsworth’s science team, based at the Institut Pierre Simon Laplace in Paris, said: “If Gliese 581d does turn out to be habitable, it would still be a pretty strange place to visit – the denser air and thick clouds would keep the surface in a perpetual murky red twilight, and its large mass means that surface gravity would be around double that on Earth.

“But the diversity of planetary climates in the galaxy is likely to be far wider than the few examples we are used to from the Solar System. In the long run, the most important implication of these results may be the idea that life-supporting planets do not in fact need to be particularly like the Earth at all.”

Rocky worlds have been identified in other planet hunts. NASA have said they believe more than half of stars in the Sun’s neighbourhood could have rocky planets. The scientists’ discovery is published in the journal The Astrophysical Letters.

Reporter: Paul Sutherland