After leaving Vesta’s orbit in 2012, NASA’s Dawn spacecraft moved through the asteroid belt between the orbits of Mars and Jupiter, to head for the dwarf planet, Ceres. In the process, it became the first ever spacecraft to travel three hundred sixty degrees around two planets, and on March 6, it will make its second and final stop by entering Ceres’ orbit.
As a precursor for the event, Dawn has been sending out images of Ceres that are already stirring up questions, triggering the curiosity of the science community. One observation is that Ceres has a bright spot and an impact crater, features some scientists believe are caused by a mechanism called cryovolcanism, where sub-surface ice is forced at the surface. However, this conclusion is quickly beginning to seem more and more unlikely.
Putting cryovolcanism aside, researches are also especially ecstatic about the possible presence of water on the planet. Marc Rayman, Dawn mission director and chief engineer, expressed his enthusiasm on Discovery News saying, “One of the mysteries is that of liquid water, are there sub-surface reservoirs of water — ponds or lakes or oceans? I think that’s really exciting.”
There are strong indications that sub-surface reservoirs of water are present on the dwarf planet. Observations and theoretical models suggest that Ceres was a developing planet during the early epochs of the solar system. Conversely, if the planet did indeed have sub-surface liquid water reservoirs during its early stages, it is most likely that they are now long frozen, lest salts were produced through interactions in the minerals in the rocks to maintain a liquid state. This is because Ceres does not experience a tidal heating and thus only obtains a weak sunlight as its heat source, unlike the conditions of Saturn’s moon Enceladus or Jupiter’s moon Europa.
However, as Ceres came closer into focus, scientists were taken by surprise. What they expected to find was an ice-covered crust, but as it turns out, Ceres has an ancient cratered surface, “The ice should be close to the surface, it flows. So something else is going on. There’s lots of ideas as to how we can explain that, but we’re going to have to sharpen our pencils, do a lot of detailed models and we’re going to need a little more insight from high-resolution data (from Dawn),” stated a Dawn deputy project scientist.
Although more and more questions continue to baffle scientists, definite answers cannot be ascertained until Dawn is able to get a closer examination of the dwarf planet. In the meantime, excitement in the space community is building up as Dawn nears its final destination.