NASA’s Dawn spacecraft is approaching the final of phase of its mission to study the asteroid belt located between the orbits of Mars and Jupiter, providing us starry-eyed earthlings some of the best images of the region and the objects in it ever taken.
The asteroid belt is a much misunderstood part of our solar system, and is often depicted among bearded science fiction writers as a virtual maze of unnavigable rock that spells certain death and doom to any spacecraft that dares to enter. The reality, however, is far less frightening. In fact, the average distance between objects in the asteroid belt is approximately 600,000 miles.
Roughly 50% of the mass of the entire belt is contained within the four largest asteroids: Vesta, Pallas, Hygiea and the icy dwarf planet Ceres, which are also the very objects that have been the main focus of NASA’s Dawn spacecraft.
Dawn first approached Vesta in late 2011 and now comes close to fulfilling its mission as it nears Ceres, bringing us the most detailed images not only of the largest object in the asteroid belt, but also the only dwarf planet near the center of our solar system.
Dawn is the first spacecraft to utilize Ion thrusters for maneuvering in and out of orbits, and will be the first probe in human history to reach a dwarf planet. Dawn is also the first to map the entirety of Vesta, which it did in little over nine months in 2011-2012. This part of the mission has provided scientists several spectacular images and troves of data about Vesta’s surface geology, temperature activity and its internal structure. Now, Dawn turns its focus on the dwarf planet Ceres.
“Ceres is a ‘planet’ that you’ve probably never heard of. We’re excited to learn all about it with Dawn and share our discoveries with the world.” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Giuseppe Piazzi first discovered Ceres in 1801. Originally, Ceres was considered the ‘missing planet’ between Mars and Jupiter predicted by earlier astronomers. Ceres later lost its planetary status and was downgraded to an asteroid, but was reclassified yet again in 2006 as a ‘Dwarf Planet’. The impending encounter with Ceres is very exciting as Ceres has the distinction of being one of the few icy worlds in our solar system.
Animation of Ceres from several images taken by Dawn
The first set of images of Ceres is already inspiring intrigue and controversy. As seen in the animation above, a conspicuous white spot on the surface of Ceres has many speculating that it may be a water vapor plume. Last January, scientists using the European Space Agency’s Herschel Infrared Space Observatory recorded data that seems to verify the existence of plumes of water vapor surrounding Ceres. The nature of these plumes and the ice on Ceres itself have been the object of much scrutiny.
The source of the water vapor plumes remain a mystery. Are they the result of internal heat that’s producing volcanoes of ice or simply the result of sublimation during seasonal periods of warmth? If internal heat is the reason, then it is possible that Ceres has a frozen ocean that’s partially liquid, in which case it’s also possible that Ceres harbors life.
According to Carol Raymond, deputy principal investigator of the Dawn mission at JPL, “Data from this mission will revolutionize our understanding of this unique body. Ceres is showing us tantalizing features that are whetting our appetite for the detailed exploration to come.”