Newborn Earth-like planets could be easier to spot than earlier believed

Washington, Oct 17 : A new study has determined that newborn Earth-like planets that are hot may be easier to spot because they stay that way longer than astronomers have thought.

The study has been done by MIT (Massachusetts Institute of Technology) planetary scientist Linda Elkins-Tanton.

For a few million years after their initial formation, planets like Earth may maintain a hot surface of molten rock that would glow brightly enough to make them stand out as they orbit neighboring stars.

Elkins-Tanton, Mitsui Career Development Professor of Geology in the Department of Earth, Atmospheric and Planetary Sciences, said that the "magma ocean" stage for Earth-sized planets may last a few million years, much longer than previously estimated.

"That means we may actually see them elsewhere, as detection systems get better," she said.

The research shows that even after the surface magma solidifies, within about five million years, it could stay hot enough to glow brightly in infrared light for tens of millions of years, providing a relatively long window for detectability.

The big problem for astronomers hoping to detect planets around other stars is the vast difference in brightness between the star and the planet, which shines only by reflecting light from its parent star.

But, the difference in brightness in infrared wavelengths for a glowing, molten planetary surface would be much less, making the detection more feasible.

The long duration of the molten stage turns out to be the result of a two-stage process, Elkins-Tanton explained.

The initial heating, generated by a combination of radioactivity in the planet's interior and the heat generated by the collision of millions of chunks of rock crashing together to form the planet, actually is quite short-lived.

The planet's surface is expected to solidify quickly, within a few hundred thousand years, as originally thought.

But then, a secondary upheaval begins, in which heavier iron-rich material that has solidified at the surface begins to sink toward the core, causing other hotter material to rise to the surface.

This "overturn" process, it turns out, produces the much-longer-lived molten surface, lasting for millions of years.

Because the Earth's crust is so dynamic, there is no material left from that initial epoch that could be studied to test this modelling, but on other planets such as Mars or Mercury, there might be early remnant rocks that could be tested.

The analysis also leads to specific conclusions about the surface composition of planets, so detection of certain specific minerals on Mercury, for example, which the MESSENGER spacecraft may be able to carry out when it begins its study of the planet in 2011, might support the theory.

ANI