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The exoplanet, COROT-7b, was discovered in February by the COROT space telescope launched by the French and European space agencies. Last month this planet became the first one outside our solar system to be confirmed as a rocky body — most other known exoplanets are gas giants.

It is nearly twice the size of Earth and about five times the mass of our world. Calculations have indicated it has a density about that of Earth's, which means it is likely made up of silicate rocks, just as Earth's crust is.

The planet is likely much less hospitable to life though, as it is only about 1.6 million miles (2.6 million km) away from its parent star — 23 times closer than Mercury sits to the sun.

To find out what COROT-7b's atmosphere might be like, Fegley and his colleagues modeled it. They found that COROT-7b's atmosphere is made up of the ingredients of rocks and when "a front moves in," pebbles condense out of the air and rain into lakes of molten lava below.

"Sodium, potassium, silicon monoxide and then oxygen — either atomic or molecular oxygen — make up most of the atmosphere," Fegley said. But there are also smaller amounts of the other elements found in silicate rock, such as magnesium, aluminum, calcium and iron.

The rock rains form similarly to Earth's watery weather: "As you go higher the atmosphere gets cooler and eventually you get saturated with different types of 'rock' the way you get saturated with water in the atmosphere of Earth," Fegley explained. "But instead of a water cloud forming and then raining water droplets, you get a 'rock cloud' forming and it starts raining out little pebbles of different types of rock."

Observers have recently spotted sodium in the atmospheres of two other exoplanets.

Source livescience.com