An artist's illustration of an Earth-like planet. The search for planets that are similar to Earth is one of NASA's main goals. Many planets have already been discovered orbiting other stars, but so far only larger planets (the size of Jupiter or larger) have been found. New missions are being planned by NASA which will be able to detect smaller Earth-sized planets. Some of these missions will also try to detect signs of life on these planets by studying emissions in their atmospheres.


Super-Earths will have plate tectonics

SOURCE: New Scientist
14 October 2007

"Super-Earths" - rocky planets up to 10 times the mass of Earth that orbit other stars - probably have similar structures to our world, with a solid inner core surrounded by a liquid mantle and then a crust. They may even have plate tectonics, which some argue is necessary for life to evolve.

Dimitar Sasselov of the Harvard-Smithsonian Center for Astrophysics and colleagues came to this conclusion after modelling geological processes on planets of various sizes. They found that as planetary mass increases, more heat is trapped and convection increases. As a result the shear stress within the crust increases too and plate thickness decreases. That means the plates are weaker and plate tectonics becomes "inevitable" ( Our own planet seems to lie at the threshold. If it were any less massive, it would probably not have plate tectonics.

Plate tectonics may boost biodiversity by recycling chemicals and minerals through the crust. "When it comes to habitability, super-Earths are our best destination," says Sasselov.

"The idea is right," says Jack Lissauer of NASA's Ames Research Center in Moffett Field, California. "Plate tectonics is more likely on more massive planets."

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