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With the news yesterday that asteroid 2002 NT7 has a chance of colliding with the Earth in 2019, there was much interest at the Meteoritical Society Meeting in talks today on forthcoming space missions to study asteroids.
Dr Chris Russell, from UCLA, announced details of the NASA Dawn Discovery mission that is due to be launched in 2006. Dawn Discovery is an ambitious mission that will rendezvous with and investigate two of the most significant asteroids in the main asteroid belt, 4 Vesta and 1 Ceres. Although both asteroids are very large, at more than five hundred kilometres across, they could not be more different and will provide us with important information on the origins of our Solar System.
Asteroid 4 Vesta is located in the inner asteroid belt, closest to the orbit of the planet Mars, and is thought to be completely melted since the spectrum of light and infrared it reflects is similar to terrestrial lavas known as basalts. Vesta is believed to be the source of a group of meteorites known as the HEDs, which comprise the Howardites, Eucrites and Diogenites since these have almost identical spectra to the asteroid. The Eucrites are lavas and thus the mission expects to find lava flows on the surface of the asteroid and even to be able to study its interior by examining the bottom of a large crater on the asteroid’s south pole.
Ceres is a very different asteroid all together. Even though 1 Ceres is larger than Vesta, at nearly 1000 km in diameter, the light reflected by the asteroid shows the presence of carbon and water at its surface suggesting that it has never melted. Like Vesta, Ceres is in the main asteroid belt and the Dawn Discovery team hope that by comparing the two asteroids we’ll find out why some asteroids melted 4.5 billion years ago and others did not.
Dawn Discovery will be the first space mission to put a probe into orbit around two asteroids and the mission team expect the information obtained to allow us to better understand how both asteroids and planets form.
Neither 1 Ceres or 4 Vesta have orbits that bring them close to the Earth since they are in more or less circular paths between Mars and Jupiter. Some of the smaller Near Earth Asteroids that do approach the Earth, however, are made from similar materials to these large main belt objects. The Dawn Discovery mission, therefore, will also help us investigate the nature of NEOs.
Matthew Genge
at the Meteoritical Society Meeting in Los Angeles
More info: The Meteoritical Society
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