Amsterdam, Feb 4 : The European Space Agency's (ESA's) COROT space mission has found the smallest terrestrial planet ever detected outside the Solar System, which has a surface to walk on.

The amazing planet is less than twice the size of Earth and orbits a Sun-like star. Its temperature is so high that it is possibly covered in lava or water vapor.

About 330 exoplanets have been discovered so far, most of which are gas giants with characteristics similar to Jupiter and Neptune.

But, the new find, named COROT-Exo-7b, is different.

Its diameter is less than twice that of Earth and it orbits its star once every 20 hours. It is located very close to its parent star, and has a high temperature, between 1000 and
1500 degrees Celsius.

Astronomers detected the new planet as it transited its parent star, dimming the light from the star as it passed in front of it.

The density of the planet is still under investigation.

It may be rocky like Earth and covered in liquid lava. It may also belong to a class of planets that are thought to be made up of water and rock in almost equal amounts.

Given the high temperatures measured, the planet would be a very hot and humid place.

"Finding such a small planet was not a complete surprise", said Daniel Rouan, researcher at the Observatoire de Paris Lesia, who coordinates the project with Alain Leger, from Institut d'Astrophysique Spatiale in Paris, France.

"COROT-Exo-7b belongs to a class of objects whose existence had been predicted for some time. COROT was designed precisely in the hope of discovering some of these objects," he added.

This discovery is significant because recent measurements have indicated the existence of planets of small masses but their size remained undetermined until now.

Scientists are particularly puzzled by the internal structure of COROT-exo-7b.

They are unsure whether it is an `ocean planet', a kind of planet whose existence has never been proved so far.

In theory, such planets would initially be covered partially in ice and they would later drift towards their star, with the ice melting to cover it in liquid.

"This discovery is a very important step on the road to understanding the formation and evolution of our planet," said Malcolm Fridlund, ESA's COROT Project Scientist.

"For the first time, we have unambiguously detected a planet that is `rocky' in the same sense as our own Earth. We now have to understand this object further to put it into context, and continue our search for smaller, more Earth-like objects with COROT," he added. (ANI)