Planets without metallic cores may not be suitable for life

August 21st, 2008 - 12:52 pm ICT by ANI  

London, August 21 (ANI): A new study has suggested that some planets beyond our solar system might be rocky like Earth, but lack a metallic core and a magnetic field, which would make them inhospitable to life as we know it.

Rocky planets were once thought to consist of three main layers: a thin solid crust, a viscous, rocky mantle and a solid or molten iron core.

This layering, or differentiation, is thought to have occurred early in the solar systems history, when collisions between rocky bodies and the decay of radioactive isotopes melted the interiors of large objects, allowing dense material to settle towards their centres.

But exoplanet discoveries have revealed a menagerie of diverse worlds.

Now, according to a report in New Scientist, Linda Elkins-Tanton and Sara Seager of MIT describe how another planetary oddity might form: coreless rocky planets.

Such planets might differentiate into layers of different density but not form a core essentially making them giant silicate mantles.

One way this could happen is if the planet was born in a very water-rich environment, such as the icy regions at large orbital distances from Sun-like stars.

The iron could interact with water, forming iron oxide, faster than it would fall to the centre of the planet.

If the iron reacts with water, then it will be locked away with other minerals and wont reach the core as metallic iron, Seager told New Scientist.

According to Diana Valencia of Harvard University, studying the planets parent star may provide hints about the existence of its core.

If we look at the star, we will know the iron-silicate ratio and some of the chemistry that was present while these planets were forming, she told New Scientist.

One thing that is certain is that coreless planets will not have magnetic fields, which would make then unsuitable for life.

Earths magnetic field is generated by molten iron circulating in its core. It shields life on Earth from harmful charged particles from space called cosmic rays.

If we got nailed by cosmic rays, it would cause us a lot of (genetic) mutations, said Seager. (ANI)

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