Scientists have come up with their first weather report for a super-Earth -- a type of planet two to 10 times bigger than Earth that doesn't exist in our solar system, but which holds much promise in the search for extraterrestrial life.
No one expects life to exist on GJ 1214b, a hellish world 70 times closer to its parent star than Earth orbits the sun. But by a fortuitous alignment of geometry, the planet disappears behind its star relative to our view on Earth, giving astronomers an opportunity to study how its parent star's light changes as it passes through the planet's atmosphere.
"We're sure it has an atmosphere, because the size is not right for a purely solid body," astronomer Jacob Bean, with the Harvard-Smithsonian Center for Astrophysics, told Discovery News.
Comparing their findings with theoretical models of atmospheric conditions, two scenarios emerge: the skies above GJ 1214b are dense with steam, the result of a water world sizzling away in temperatures that surpass 1,000 degrees Fahrenheit.
"Sizzle" isn't exactly the right word. Depending on the pressures and temperature, water would transition into an exotic form of matter known as a supercritical molecular fluid, which, like a gas, has the ability to pass through solid matter.
Not that there would be much solid matter on GJ 1214b. If water dominates this extrasolar world, it might have a core, but there'd be no solid ice on its surface, says Bean.
The other possibility is that GJ 1214b has an atmosphere rich in hydrogen beneath a thick layer of clouds. In this case, the planet could be like a miniature Neptune, with a rocky or solid ice core that released gases during formation or during periods of volcanic activity.
It would be even hotter than a water world, with temperatures closer to 2,000 degrees Fahrenheit and pressure 100 times higher than Earth's at sea level.
Upcoming observations with the Hubble Space Telescope should clarify what conditions exist on GJ 1214b. The techniques are considered critical for identifying distant planets that may support life. Super-Earths are prime candidates, since these planets are big enough to hang on to their atmospheres without a crushing amount of gravity.
"If you're in halfway decent shape, you'd be able to walk on these things," astronomer Paul Butler, with the Carnegie Institution's Department of Terrestrial Magnetism, told Discovery News.
"Super-Earths could easily hold on to their atmospheres, which means they can have liquid water. In terms of habitability, super-Earths are extraordinarily exciting."
Bean's research appears in this week's Nature.