Study suggests Earth-like planets could be very different from Earth

Posted by David Eicher
on Friday, February 24, 2012

A revolutionary new study by a team of astronomers suggests that although the universe may be filled with planets similar to Earth, other Earth-like worlds may be quite different from our planet. Garik Israelian, an astronomer at the Institute for Astrophysics in the Canary Islands (AIC), alerted me to this fascinating study. He is one of the researchers involved, the others being Jonay González Hernández (also of the AIC); Jade C. Carter-Bond and David O’Brien of the Planetary Science Institute in Tucson, Arizona; and Elisa Delgado Mena and Nuno C. Santos of the University of Porto in Portugal.

ESO/M. Kornmesser
The astronomers and their students have been working on this project for some 10 years. Computer simulations produced by the teams show that because of varying elemental abundances in host stars, the planets in orbit about them could have a large range of terrestrial compositions. The mineralogy of these planets would vary greatly depending on the available elements, and two key ratios are especially important: the ratio of carbon to oxygen (which controls the distribution of silicon among carbonate and oxide minerals) and the ratio of magnesium to silicon (which yields information about silicate mineralogy).

In 2010, Carter-Bond and collaborators carried out computer simulations, including the chemical composition of protoplanetary clouds, and found that terrestrial planets formed with a wide variety of chemical compositions. Mena and collaborators carried out the first detailed study of carbon, oxygen, magnesium, and silicon abundances in 61 stars with detected exoplanets and 270 stars without detected planets from the HARPS spectrograph on the 3.6-meter telescope at the European Southern Observatory’s La Silla Observatory in Chile.  

The astronomers found ratios of minerals very different than those in the Sun, which demonstrates a wide variety of planetary systems must exist. Many stars with exoplanets in the HARPS sample have magnesium to silicon ratios of less than 1, meaning their planets would have abundant silicon, which would have significant implications for plate tectonics, volcanism, and atmospheric composition, as well as mineral species.

“There could be billions of Earth-like planets in the universe, but a great majority of them may have a totally different internal and atmospheric structure,” said Israelian. “Building planets in chemically non-solar environments may lead to the formation of strange worlds very different than Earth.”

Stay tuned for more developments from this amazing research.

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