Dawn, the first spacecraft to orbit 2 alien worlds, has gone silent

It’s dusk for Dawn.

The NASA spacecraft that was the first to orbit two worlds in one mission has sent its final messages back to Earth, mission managers announced November 1.

The spacecraft missed two check-ins with NASA’s Deep Space Network on October 31 and November 1, scientists say. That silence likely means Dawn ran out of the hydrazine that fuels its thrusters, which help the probe point its solar panels toward the sun and its antenna toward Earth. Dawn is the second NASA mission to end recently — the planet-hunting Kepler space telescope ran out of gas at the end of October (SN Online: 10/30/18).

Though the end of Dawn was expected, mission team members still expressed sadness.

“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,” mission director and chief engineer Marc Rayman of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. “The demands we put on Dawn were tremendous, but it met the challenge every time.”

Dawn launched in 2007 for the asteroid Vesta, the second-largest object in the asteroid belt between Mars and Jupiter. When the spacecraft arrived in July 2011, making it the first probe to orbit an asteroid belt object, Dawn found a world that seemed more like a planet than an asteroid (SN: 4/21/12, p. 9). The probe revealed that Vesta’s interior is probably divided into layers, like Earth’s, and it may have had a magnetic field. Scientists also found that two craters near Vesta’s south pole are the source of about 5 percent of all the meteorites found on Earth.

In September 2012, Dawn left Vesta on a treacherous 2½-year journey to dwarf planet Ceres, the largest object between Mars and Jupiter. Ceres proved to be a world shaped by water, with salt deposits from a possible underground ocean showing up as bright spots in its craters (SN: 1/9/16, p. 14). The dwarf planet also sports slouching icy volcanoes (SN: 10/13/18, p. 36) and homegrown organic compounds (SN: 3/18/17, p. 8).

Because of the possibility of life surviving on Ceres, NASA is not planning to crash Dawn into the dwarf planet’s surface. Instead, Dawn will remain in a silent orbit around Ceres for decades, if not longer (SN Online: 10/20/17).

“We’ve known she was going to die soon, and she completed all of her science goals and a lot more,” planetary scientist and mission engineer Keri Bean, also of NASA’s Jet Propulsion Laboratory, said in a Twitter message. “So I’m more proud than anything. Glad to have been a part of it.”

Dawn’s demise doesn’t end humanity’s exploration of the asteroid belt, though. Japan’s Hayabusa2 spacecraft and NASA’s OSIRIS-REx spacecraft will bring pieces of two asteroids back to Earth in the next few years. And in 2022, NASA will launch Psyche, named after the unique metal asteroid it aims to visit. Psyche the asteroid is thought to be a naked planetary core, giving scientists a chance to study a planet’s insides from the outside.