Scientists solve mystery of odd patterns of oxygen in solar system's earliest rocks

Scientists solve mystery of odd patterns of oxygen in solar system's earliest rocks
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Cosmochemists have solved a long standing mystery in the formation of the solar system: Oxygen, the most abundant element in Earth's crust, follows a strange, anomalous pattern in the oldest, most pristine rocks, one that 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," said Mark Thiemens, dean of the University of California, San Diego's division of physical sciences and professor of chemistry. "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."

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, they report in the early online edition of Science October 24.

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. The mix between oxygen-16, the most abundant form with one neutron for each proton, and variants with an extra neutron or two, is strikingly different from that seen in terrestrial rocks from Earth, its moon and Mars.

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http://phys.org/news/2013-10-scientists-mystery-odd-patterns-oxygen.html#jCp