If you haven’t heard of Ceres, a planet that sits somewhere between Mars and Jupiter, you can be forgiven. It was originally classified as a true planet in the 1800s, then demoted to an asteroid and finally in 2006 promoted again as a “dwarf planet” — a status it now shares with Pluto.
But the icy Ceres, right through the changing nomenclature, has held a unique fascination for scientists: not least because it is thought to contain vast reserves of water. And so, when the sharpest image yet of the dwarf planet emerges, it is cause to celebrate. NASA’s Dawn spacecraft has sent back a picture of Ceres taken from a distance of 237,000 km. The image — although fairly blurry — is 30 per cent higher in resolution than those taken by NASA’s Hubble Space Telescope 10 years ago from 241 million kilometres away.
As the spacecraft moves closer to Ceres, the images sent back will get better. Dawn will enter into Ceres’ orbit on March 6 to capture detailed images and measure variations in reflected light to get insights into the planet's surface composition.
Last year, astronomers who studied data from ESA’sHerschel Space Observatory reported plumes of vapour emerging from Ceres’ surface, suggesting that it contained regions rich in water ice. Dawn will be the first spacecraft to visit any dwarf planet. At 950 km diameter Ceres is the smallest known dwarf planet, but the largest object in the asteroid belt between Mars and Jupiter.
