Could water ice deposits be lurking in Ceres' polar craters?
Using data collected by NASA's Dawn spacecraft, an international team of astronomers has created a Mapof the dwarf planet Ceres' northern hemisphere detailing regions thatexist in permanent shadow. According to the study, these dark zoneshouse conditions favorable to the existence of water ice.
The relatively low mass of Cerescompared to the fully fledged planets that make up our solar systemprevents it from maintaining any significant atmosphere when comparedto the potent protective shield hosted by Earth, or even the tenuousshell that clings to the Mars. However, Ceres' gravity is strongenough to prevent water particles from floating off into space.
Should these icy particles migrate to avery cold location on the surface of the planetoid, such as thebottom of a deep crater situated near one of Ceres' poles,the water would be unable to escape. These permanently-shadowedregions that are devoid of the Sun's warming influence all year roundare known as "cold traps."
Over time, enough of the tiny particlescould accumulate in the cold traps to form a shallow deposit of waterice. Cold traps, which have been discovered on solar system bodiessuch as Mercury and Earth's moon had been theorized to exist on Ceresfor some time, however planetary scientists were unable to isolatetheir potential locations until now.
A new study focused on the dwarf planet's northernhemisphere, as this was the region that experienced the mostillumination from the Sun during the period in which the images werecaptured.
The team created a detailed 3D model of the hemisphere compiled from data harvested by the Dawn spacecraft, and ran it through a series of complex computer simulations. The simulations, which were developed by scientists at NASA's Goddard Space Flight Center in Maryland, calculated the areas of Ceres' surface that received the least sunlight and solar radiation over the course of a year, which lasts 1,693 Earth days.
It was discovered that dozens of large areas comprising roughly 695 sq miles (1,800 sq km) of Ceres' northern hemisphere experience a state of perpetual shadow. This lack of direct sunlight, combined with Ceres distant orbit in relation to our star, result in a temperature that consistently stays below minus 240º F (-151º C) in the cold traps.
Each year on Ceres, it is estimated that 1 out of every 1,000 water molecules circulating the dwarf planet would become imprisoned in the shadowed regions. At these glacial rates, it takes around 100,000 years for the particles to coalesce into a thin layer of ice. However, as these deposits are estimated to be trapped for around a billion years at a time, it is possible that they still exist to this day, and that they would be detectable in follow up observations.
Earlier this month, NASA announced that the Dawn spacecraft would remain in orbit around Ceres, instead of making a planned transition to the main belt asteroid Adeona.
The NASA video below highlights the locations of the various ice deposits in the context of Ceres' northern hemisphere.
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