Saturday science subject: Rock rain

— 9:14 PM on October 3, 2009

Rain isn't a phenomenon exclusive to Earth-like planets. On Saturn's moon Titan, for instance, recent evidence suggests liquid methane rains down and forms lakes—and that's with a surface temperature of 94 K. But venturing beyond the solar system may reveal even stranger weather.

Artist's impression of Corot-7b. Source: ESO.

According to LiveScience, researchers have found a rocky exoplanet that not only orbits extremely close to its parent star, but is also gravitationally locked to it. That means one side of Corot-7b is a blistering 2,326°C, "hot enough to vaporize rock." Considering the planet's composition and its surface temperature, Bruce Fegley Jr. and his team at Washington University in St. Louis have worked out that solid rock rains down on the surface:

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."

Corot-7b is about twice as big as Earth and five times as massive, LiveScience says, but it sits 23 times closer to its star than Mercury does to our sun. According to Wikipedia, the star (Corot-7) lies 424-554 light years away from us.

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