TORONTO – Another of our solar system’s mysterious bodies is about to get a visitor.
On Monday, NASA’s Dawn spacecraft entered the approach phase on its voyage to the dwarf planet Ceres. Of course, it’s still got a few kilometres to go: it’s about 640,000 km from Ceres, travelling at 725 km/h. It will arrive at Ceres on March 6, 2015.
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Ceres, the largest known body in our asteroid belt, was discovered in 1801. It was first classified as a planet, then as an asteroid, and then in 2006 was reclassified as a dwarf planet (in the same decision that demoted Pluto from a planet). It resides in our asteroid belt, a vast region of leftover rocky debris from the formation of our solar system.
This is the second leg of Dawn’s mission: it already orbited the second-largest body in the asteroid belt, Vesta, in 2011 and 2012.
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The best look we’ve managed to get of Ceres, with a diameter of just 950 km, has been with the Hubble Space Telescope.
“Ceres is almost a complete mystery to us,” said Christopher Russell, principal investigator for the Dawn mission. “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.”
Astronomers believe that Ceres formed later than Vesta, creating two very different bodies. Ceres is has a thick ice mantle and perhaps even an ocean beneath its icy crust. It’s believed that plumes of water vapour shoot up from time to time when parts of the icy surface are heated by the sun during its orbit around the sun.
Vesta, on the other hand, is thought to be comprised of frozen lava shortly after it formed about 4.5 billion years ago.
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