In the days of the comet

Posted by mjs76 at May 28, 2010 03:35 PM |
Eleven years ago, NASA launched Stardust, a mission to collect material from a comet and return it to Earth. And now some of that precious material is at the University of Leicester.

What are comets made of? Well, dust and ice mostly – hence the common description of a comet as a ‘dirty snowball’. But what sort of dust? And indeed, what sort of ice? Researchers in our Space Research Centre are finding out.

Stardust was launched in 1999 and orbited the sun twice before, in 2004, flying right through comet Wild 2*. Two years later, Stardust returned to Earth carrying the only material ever retrieved from a comet. A very few select labs around the world have been allowed to study these minute specks of dust, the value of which is incalculable because, frankly, we’re not likely to get hold of any more any time soon. And a few of those specks of dust came to Leicester.

A team led by Dr John Bridges have been examining a few tiny bits of comet using the massive Diamond Light Source synchrotron in Oxfordshire. The synchrotron is a particle accelerator which produced intensely focussed beams that can reveal the composition and structure of the comet particles.

This study revealed the presence of iron oxide grains – ‘rust’ to you and me – some of which formed at very low temperatures. Given that the comet originated way out in the Kuiper belt (around about the orbit of Pluto) this is not surprising, but other iron oxide grains seem to have formed at high temperature and this is a surprise. Further research, as the saying goes, is needed…

* Comets are named after their discoverer, in this case a Swiss astronomer named Paul Wild. His name – and hence the comet - is pronounced ‘vilt’.