After four years of spiraling out from Earth, the Dawn spacecraft closes in on its first target.
- By Tom Jones
- Air & Space magazine, July 2011
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After a year studying Vesta, Dawn will use its ion engine to spiral up and out of orbit, becoming the first spacecraft to orbit one solar system body, then leave to orbit another. It should reach Ceres in 2015, where it will confront another mystery. Orbiting almost three times Earth’s distance from the sun, Ceres probably incorporated large amounts of water ice during its formation. Ground-based observations still show water trapped inside clay minerals on the asteroid’s surface, and models suggest that Ceres harbors a layer of ice or even liquid water beneath its solid crust.
During this six-month phase of the mission, Dawn co-investigator Mark Sykes will be looking, he says, for “signs that interior water is escaping onto Ceres’ dark surface. If we find indications of a subsurface ocean, it may exhibit the right chemical and thermal conditions for life. And then Ceres becomes an astrobiological target for exploration.” In other words, a place to look for signs of life.
The notion of a watery Ceres raises one last intriguing possibility. We won’t be sending astronauts there anytime soon, but the object’s water-rich splinters—which roam the inner solar system as near-Earth asteroids—could furnish propellants for future astronaut and robot expeditions. Dawn’s first close look at Vesta and Ceres, says Sykes, “takes asteroids out of the ‘Chicken Little’ realm”—where they’re seen only as threats—and enables us to picture using them someday as resources that “can leverage our future beyond Earth.”
Former astronaut Tom Jones would still like to head an expedition to an asteroid, but takes comfort in the certainty that asteroids are surely coming to us.