London, Oct 22 : The recent discovery of a handful of rocky planets orbiting stars outside our Solar System has led scientists wondering whether these planets are as suitable as Earth for sustaining life.

The movement of tectonic plates, which on our own planet created the Himalayas and moved the continents to their current positions, is thought to be important for moderating a planet’s temperature and recycling materials that may nourish life.

But whether 'super-Earths' – solid planets with a mass up to ten times greater than Earth too have a similar geology is something still unknown.

Now, new research by Diana Valencia at Harvard has shown that tectonic plates form inevitably as rocky planets get bigger.

As size increases, so does the amount of heat flowing up from the planet’s radioactive core through the viscous mantle.

This strikes the planet’s crusty lid with increasing force, eventually breaking it into plates.

Valencia supports her logic on the basis of the limited trend available in the Solar System.

“Mars, Mercury and rocky moons lack plate tectonics. Venus, the second largest rocky planet, may have had active plates in the past. The biggest, Earth, is the only one with plate tectonics. It might not be a coincidence,” says Valencia.

However, not everyone is convinced.

Craig O’Neill, a planetary scientist at Macquarie University in Sydney, Australia, says that Earth might be an anomaly, and the trend might not extend to bigger rocky planets.

O’Neill and his group have published a study in the Geophysical Research Letters that shows that as a planet gets bigger, the increasing force of gravity squeezes crustal rocks together into a solid lid, making it more difficult for forces from below to crack it into plates.

According to their study, a large, capped-lid planet could be like Venus, with a hellish atmosphere and runaway greenhouse effect or it could be cold and dead like Earth's Moon.

“Or, if fed by internal heat from the core, it could vent that heat through massive bouts of volcanism, as on Io, a moon of Jupiter. That doesn't necessarily rule out life, but it might make it difficult,” said O’Neill.

Valencia’s study is scheduled for publication in the Astrophysical Journal Letters. (ANI)