Exotic dust in comet trail

BY KEITH COOPER AND KULVINDER SINGH CHADHA

ASTRONOMY NOW

Posted: 22 April, 2009

Comets have been shown to possess materials that date back to before the Solar System was born. Image: NASA.

Comet dust caught in the upper reaches of Earth's atmosphere and scooped up by a NASA aircraft had been found to contain grains of dust dating back to before our Solar System formed. Dust like this is worth its weight in gold for telling us about the original conditions in the solar nebula that formed the planets, say researchers presenting their analysis today at the National Astronomy Meeting at the European Week of Astronomy and Space Science.

The dust is from comet 26P/Grigg-Skjellerup, which last passed through the inner Solar System in 2002. A year later, Earth itself passed through the trail of the comet, and the NASA aircraft climbed to catch the dust. It was then handed over to a consortium of UK, US and German astronomers who found various chemical treasure troves, including in one dust particle four grains of silicate material that date back to before the formation of the Sun. What makes these silicate grains especially unusual is that they harbour the chemical fingerprint of cooling gas in a supernova remnant; a supernova that may have exploded in the vicinity of the nascent Sun (see the article 'Tracing the Sun's Family Tree' in the May issue of 'Astronomy Now'). These pre-solar grains include olivine and carbon, and are coated in organic ices they were protected for four and a half billion years until they wound up on Earth.

The grains also contained a mineral called brownleeite, named after Donald Brownlee of the University of Washington, as well as unusual isotopes of deuterium (a 'heavy' version of hydrogen with an added neutron in its core) oxygen and nitrogen. The work was done by a team led by University of Manchester astronomer Dr Henner Busemann.

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