Washington, January 11 : A study led by Harvard University researchers has revealed that Earth is at the lower end of the size range needed for plate tectonics, which are believed to be vital for stabilizing temperatures enough for life.
Lead researcher Diana Valencia says that the new finding suggests that it would be better if astronomers searching for another habitable world in the universe started to look for rocky planets several times larger than Earth.
Tectonics, the continent-shifting forces that build mountains and fuel volcanoes, recycle Earth's crust by drawing it underground, where it melts and later re-emerges as magma. It helps keep carbon dioxide (CO2) levels in the atmosphere more or less stable by reacting with fresh rocks in a process called "weathering", and removing excess gas from the atmosphere.
Volcanic gases later release the CO2 back into the atmosphere.
"Plate tectonics is important for the carbon cycle to operate. Carbon cycling is the Earth's climate thermostat. Over time, it's kept the Earth's temperature around (that of) liquid water, allowing life to emerge," National Geographic quoted Valencia as saying.
While making a presentation at the American Astronomical Society's meeting in Austin, Texas, Valencia said that her team looked at factors that determine whether rocky planets experience tectonics.
Based on their observations, the researcher came to the conclusion that rocky worlds significantly larger than Earth, also known as "super-Earths", are more likely to have plate tectonics.
"It gives us hope (for finding habitable worlds). Finding an Earth analog is going to be hard. But finding super-Earths is easier," Valencia said.
Plate tectonics are caused by convection currents in a planet's mantle that cracks surfaces into plates, and these plates slide past one another.
Valencia that the movement process could be lubricated by the presence of water, which forms hydrated minerals. She further said that it might be a reason why plate tectonics do not exist on waterless Venus, which is otherwise very similar to Earth.
The researcher also pointed out that bigger rocky planets have more heat trapped in their interiors, and thus they producing more rapid convection currents.
"The bigger planets would not need water to have plate tectonics," she said.
Valencia also pointed out that super-Earths would be much more similar to Earth than other rocky planets in the solar system - viz., Mercury, Venus, and Mars.
She said that there might also be more earthquakes on a super-Earth, since the continental plates would be grinding past each other at a rate as much as ten times faster than Earth's.
"Humans living on such a planet might not be aware day-to-day, but ... it would be more active than Earth," she said.