While people on Earth celebrated Halloween, NASA’s Dawn spacecraft quietly gave up the ghost.
The spacecraft, which explored two of the largest objects in the asteroid belt missed its last two check-ins, one on October 31st and another on November 1st. Without a signal from the spacecraft, NASA engineers concluded that Dawn had finally run out of fuel, officially ending its mission.
The people working on the project knew this day was coming. In June they put it into its closest orbit yet around the dwarf planet Ceres, knowing that it only had a few months of fuel left. Though it was anticipated, the end of the mission was still emotional.
“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,” Marc Rayman, the chief engineer on the Dawn Mission said in a press release. “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 August, Rayman wrote a detailed and heart-rending description of what researchers knew would happen to Dawn as it died. When it becomes unable to hold itself steady, the computer will run through a series of checks, trying to stay on course and continue its mission, but at that point, not even fumes will be left to power the craft’s thrusters.
“Dawn’s struggle will be brief, lasting only hours before the battery is exhausted. The seasoned adventurer will sink into unconsciousness. At some later time, as its stately rotation brings the solar arrays back into the light, it may well begin to revive, but the cycle will repeat.” Rayman wrote.
Dawn’s shell is still in that last orbit around the dwarf planet Ceres. Without fuel, it can’t hold itself steady enough to harvest energy from its solar panels or turn its transmitter back to Earth for a final goodbye. It will stay like that for at least 20 years, circling around the dwarf planet, silent and powerless.
This is the second time this week that NASA researchers have had to bid farewell to a mission. Earlier this week, the exoplanet-discovering Kepler Space Telescope also ran out of fuel, forcing its extended mission into retirement.
Dawn was two years older than Kepler, launching in 2007, with the mission to study Vesta and Ceres, the two largest objects in the asteroid belt. The asteroid belt, located between Jupiter and Mars, contains numerous rocky objects left over from the “dawn” of the Solar System, which is how the spacecraft got its name.
Dawn was the first spacecraft to orbit two targets in deep space. It found the two objects, Vesta and Ceres, were very different from each other. Vesta had an iron core and a pitted surface that boasted craters, including one with a mountain twice the size of Mount Everest at its center.
Ceres also had a peak, a towering mountain that researchers think was an ice volcano, driven by salty water and mud instead of magma. While Vesta was all rock and metal, Dawn found that Ceres had rock and ice, studded with bright spots that indicated the presence of salts or carbonates. It even had organic materials on its surface.
The fact that the two objects were so different gave researchers a better understanding of the dynamics of the early Solar System. Vesta is similar to the inner planets, and most likely formed near its present location. Ceres — or at least the icy, volatile materials on its surface — would have had to form farther away from the heat of the Sun in order to survive, and then move inward.
While Dawn is dead, the data it collected over the course of its 11-year mission will live on, and researchers here on Earth still have plenty of work to do to analyze the wealth of information sent back by the spacecraft.
“In many ways, Dawn’s legacy is just beginning,” Carol Raymond, principal investigator of the Dawn mission says.