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Mystery of odd patterns of oxygen in solar system`s earliest rocks solved

Last Updated: Friday, October 25, 2013 - 16:25

Washington: A new research led by Indian origin cosmochemist has solved a long standing mystery in the formation of the solar system: Oxygen follows a strange, anomalous pattern in the oldest, most pristine rocks.

This anomalous pattern must result from a different chemical process than the well-understood reactions that form minerals containing oxygen on Earth.

"Whatever the source of the anomaly must be a major process in the formation of the solar system, but it has remained a matter of contention. Our experiments essentially recreate the early solar system in that they take gas phase molecules and make a solid, a silicate that is essentially the building block of planets," Mark Thiemens, dean of the University of California, San Diego`s division of physical sciences and professor of chemistry, said.

By re-creating conditions in the solar nebula, the swirl of gas that coalesced to form our star, the planets and the remnant rocky debris that circles the Sun as asteroids, the researchers demonstrated that a simple chemical reaction, governed by known physical principles, can generate silicate dust with oxygen anomalies that match those found in the oldest rocks in the solar system.

Scientists first noted the discrepancy forty years ago in a stony meteorite that exploded over Pueblito de Allende, Mexico, and it has been confirmed in other meteorites as well. These stony meteorites, asteroids that fell to Earth, are some of the oldest objects in the solar system, believed to have formed nearly 4.6 billion years ago with the solar nebula`s first million years.

Subrata Chakraborty , a project scientist in chemistry at UC San Diego and the lead author of the study, said that Oxygen isotopes in meteorites are hugely different from those of the terrestrial planets.

Chakraborty said with oxygen being the third most abundant element in the universe and one of the major rock forming elements, this variation among different solar system bodies is a puzzle that must be solved to understand how the solar system formed and evolved.

Oxygen isotopes usually sort out according to mass: oxygen-17, with just one extra neutron, is incorporated into molecules half as often as oxygen-18, with two extra neutrons.

In these stony meteorites though, the two heavier oxygen isotopes show up in equal proportions. The rates at which they are incorporated into minerals forming these earliest rocks was independent of their masses.

The study is published in journal Science.

First Published: Friday, October 25, 2013 - 16:25

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