Field Museum meteorites help determine planetary core formation

Thu, 06/26/2014 - 10:49 -- pheck

A Field Museum research loan of iron meteorites that were made available to a group of researches in Germany led to the most accurate chronology to date of planetary core formation.

The group’s study finds that planetary cores formed very fast in geological terms, in about 1 million years after the first solids condensed in the solar system. For the first time the study finds also that cores of the parent bodies of different iron meteorites formed at different times. This was previously unknown and unresolvable because the analytical methods were not precise enough.

Cores in planets and asteroids formed while the interior was still very hot and partially molten. The dense metals sank to center by gravity and the lighter rocky material floated up and formed the mantle and crust. Besides the Earth, Mars and the other terrestrial planets, several asteroids where hot enough early in their existence to form cores. Iron meteorites are thought to be pieces of cores that got ejected into space after their parent asteroids broke up after violent collisions. The Field Museum has the largest collection of meteorites at a private research institution with iron meteorites particularly well represented. That’s why the group from the German University of Munster contacted the Field Museum’s curator of meteorites Dr. Philipp Heck (Robert A. Pritzker Associate Curator for Meteoritics and Polar Studies) to request samples of iron meteorites. The request as critically reviewed; and given the group’s excellent track record and the high scientific merit of the study the sample request was approved.

For high-precision chemical analyses like the ones performed in this study the samples are completely digested. Dr. Heck points out that, “the allocated meteorite samples are only a tiny fraction of the Field Museum’s holdings of a particular meteorite, usually less than a percent, and are therefore of no concern to the long term curation and retention of meteorites for future generations of scientists.”
“We are proud that meteorites from the Field Museum play such an important role cutting-edge science and knowledge generation.”

The study was published in the peer-reviewed high-impact journal Science and can be read at http://www.sciencemag.org/content/344/6188/1086.summary.