Australasian Science: Australia's authority on science since 1938

Dawn Closes in on Ceres

By David Reneke

A spacecraft is about to enter the orbit of Ceres, and construction of the world’s biggest optical and infrared telescope has been approved.

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NASA’s Dawn spacecraft has commenced its approach to Ceres, a dwarf planet the size of NSW that has never been visited by a spacecraft. Dawn, launched in 2007, is scheduled to enter Ceres’ orbit on 6 March.

This is history in the making, for two reasons. Dawn’s arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets. Dawn previously explored the large asteroid Vesta in 2011, capturing detailed images and data about that body.

“Ceres is almost a complete mystery to us,” said Christopher Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. “Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised.”

The two planetary bodies are thought to be different in so many ways. Ceres may have formed later than Vesta, and have a cooler interior. Current evidence suggests that Vesta only retained a small amount of water because it formed earlier, when radio­active material was more abundant, which would have produced more heat. Ceres, in contrast, has a thick ice mantle and may even have an ocean beneath its icy crust.

Ceres, with an average diameter of 950 km, is the largest body in the asteroid belt between Mars and Jupiter. By comparison, Vesta has an average diameter of 525...

The full text of this article can be purchased from Informit.