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Comet samples arrive at Museum

14 February 2006

Comet dust particles, brought back to Earth by NASA's Stardust spacecraft, have arrived at the Natural History Museum.

The comet particles are the first ever collected directly from a comet. They are the only well-preserved extraterrestrial samples to be returned to Earth in thirty years.

Wild 2 comet

In January 2004 the Stardust probe reached within 240 kilometres of the nucleus of a comet named Wild 2. The journey took seven years and the spacecraft travelled 4.6 billion kilometres, landing safely in Utah on 15 January 2006.

The beginnings of our solar system

It is widely believed that comets contain material unchanged from more than four and a half billion years ago, before the creation of our solar system.

Over time much of this material would have been incorporated into asteroids and planets and we therefore lose these original building blocks.

However, the precious cometary samples from Stardust should let us discover much more about what was happening before, and at the origin, of our solar system.

Investigating the comet dust

An international team of scientists, including those from the Natural History Museum, the University of Kent, Imperial College, the University of Manchester and the Open University, will now be helping NASA to investigate the dust grains.

Cosmic dust grains have been caught in blocks of a light-weight material called silica aerogel and have also left impact craters on the aluminium foil surfaces of the spacecraft. These craters will have preserved a very good record of the size of the dust grains, important in detecting what the dust is made of.

Anton Kearsley, X-ray Microanalyst in the Department of Mineralogy at the Natural History Museum has been working with colleagues around the world to test a range of methods for analysing the Stardust samples.

'I think these are some of the most exciting samples we will ever have seen from space. I am used to looking at the remains of dust that has been splattered onto spacecraft in the Earth's orbit, where impacts can be very violent. However, because Stardust flew past the comet nucleus at a relatively low speed, about 6 kilometres per second, the dust should not be so damaged.'

Simulating dust impacts

Some of the work being carried out includes analytical scanning electron microscopy at the Natural History Museum and laboratory impact experiments at the University of Kent. These experiments have been used to simulate dust impacts on the spacecraft and will allow us to confirm the size of the cometary dust grains before they were collected by the spacecraft.

The results will be published in Meteoritics and Planetary Science in the spring of 2006.