The promising potential for observing Ceres in elliptical orbits from closer than ever before makes a second extended mission there extremely attractive. NASA and the panel of scientists and engineers convened to provide an independent, objective assessment concluded that further exploration of Ceres would be the most valuable assignment for the spacecraft. It is noteworthy that Dawn is the only spacecraft ever to orbit two extraterrestrial destinations and even now, having significantly exceeded its original objectives, has the capability to leave Ceres and pay a brief visit to a third (although it does not have enough xenon left to orbit a third), but the prospects for new discoveries at Ceres are too great to pass up.

Ceres is not only the largest object between Mars and Jupiter but also certainly one of the most intriguing. In fact, motivated by what Dawn has found, there is now great interest in the possibility of sending a lander there someday. Anything more Dawn can do to learn about Ceres or to help pave the way for a subsequent mission will be of great importance.

Ceres is just too fascinating to abandon! Dawn has already revealed the dwarf planet to be an exotic world of ice, rock and salt, with organic materials and other chemical constituents, and now we can look forward to more discoveries. After all, the benefit of having the capability to orbit a distant destination, rather than being limited to a quick glimpse during a fleeting flyby, is that we can linger to scrutinize it and uncover even more of the secrets it holds. (Some readers may also draw inspiration from Ceres' ingredients to concoct recipes for treats to give out to Halloween visitors.)

In addition to the possibility of observing Ceres from unprecedentedly close, there are other benefits to keeping our sophisticated probe at work there. For now, let's consider two of them, both related to how long it takes Ceres to complete its stately orbit around the sun. One Cerean year is 4.6 terrestrial years.

The dwarf planet carries its robotic moon with it as it follows its elliptical path around the sun. In fact, all orbits, including Earth’s, are ellipses. Ceres’ orbit is more elliptical than Earth’s but not as much as some of the other planets. The shape of Ceres’ orbit is between that of Saturn (which is more circular) and Mars (which is more elliptical). (Of course, Ceres’ orbit is larger than Mars’ and smaller than Saturn’s, but here we are considering how much each orbit deviates from a perfect circle, regardless of the size.)

When Dawn arrived at Ceres in March 2015, they were 2.87 AU from the sun. That was well before the dwarf planet's orbit carried them to the maximum solar distance of 2.98 AU in January 2016. Now, with the second extended mission, the spacecraft will still be operating when Ceres reaches its minimum solar distance of 2.56 AU in April 2018. Dawn will keep a sharp eye out for any changes caused by being somewhat closer to the sun.