NASA declares Dawn, a mission to the two largest bodies in the Solar System’s main asteroid belt, Vesta and Ceres, over after the spacecraft depletes its hydrazine fuel and stops communicating with the agency’s Deep Space Network.
“Today, we celebrate the end of our Dawn mission — its incredible technical achievements, the vital science it gave us, and the entire team who enabled the spacecraft to make these discoveries,” said Dr. Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate.
“The astounding images and data that Dawn collected from Vesta and Ceres are critical to understanding the history and evolution of our Solar System.”
Part of NASA’s Discovery Program, Dawn launched in 2007 on a journey that put about 4.3 billion miles (6.9 billion km) on its odometer. Propelled by ion engines, the spacecraft achieved many firsts along the way.
Dawn orbited Vesta, the second largest world in the asteroid belt, for more than a year, from July 2011 to September 2012.
Its investigation confirmed that Vesta is the parent of the HED (howardites, eucrites, and diogenites) meteorites, which Dawn connected to Vesta’s large south polar basin, a priceless cosmic connection between samples in hand and a singular event on a small planet.
Vesta is small enough — about the same size as Saturn’s moon Enceladus — to have been deeply scarred by the Rheasilvia impact that launched the HEDs, but large enough to have differentiated into an iron core, silicate mantle, and igneous crust.
After its escape from Vesta and its journey onward, Dawn entered orbit around Ceres in March 2015.
The spacecraft discovered that the inner Solar System’s only dwarf planet was an ocean world where water and ammonia reacted with silicate rocks.
“The fact that my car’s license plate frame proclaims, ‘My other vehicle is in the main asteroid belt,’ shows how much pride I take in Dawn,” said Dawn mission director and chief engineer Dr. Marc Rayman, of NASA’s Jet Propulsion Laboratory.
“The demands we put on Dawn were tremendous, but it met the challenge every time. It’s hard to say goodbye to this amazing spaceship, but it’s time.”
“In many ways, Dawn’s legacy is just beginning,” said principal investigator Dr. Carol Raymond, also NASA’s Jet Propulsion Laboratory.
“Dawn’s data sets will be deeply mined by scientists working on how planets grow and differentiate, and when and where life could have formed in our Solar System. Ceres and Vesta are important to the study of distant planetary systems, too, as they provide a glimpse of the conditions that may exist around young stars.”
Dawn missed scheduled communications sessions with NASA’s Deep Space Network on Wednesday, October 31, and Thursday, November 1.
After the flight team eliminated other possible causes for the missed communications, mission managers concluded that the spacecraft finally ran out of hydrazine, the fuel that enables the spacecraft to control its pointing.
Dawn can no longer keep its antennae trained on Earth to communicate with mission control or turn its solar panels to the Sun to recharge.
Because Ceres has conditions of interest to scientists who study chemistry that leads to the development of life, NASA follows strict planetary protection protocols for the disposal of the spacecraft.
Dawn will remain in orbit for at least 20 years, and engineers have more than 99% confidence the orbit will last for at least 50 years.
So, while the mission plan doesn’t provide the closure of a final, fiery plunge — the way NASA’s Cassini spacecraft ended last year, for example — at least this is certain: Dawn spent every last drop of hydrazine making science observations of Ceres and radioing them back so we could learn more about the Solar System we call home.