In Depth

NASA's asteroid explorer Dawn soon to go dark

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Science  19 Oct 2018:
Vol. 362, Issue 6412, pp. 275
DOI: 10.1126/science.362.6412.275

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Summary

After an 11-year journey to Vesta and Ceres, the asteroid belt's two largest members, NASA's Dawn spacecraft was expected to run out of thruster fuel within a few weeks, ending its mission. The robotic explorer, which gave a close-up view of how the presence or absence of water can shape asteroids, will remain tumbling in orbit around Ceres for decades before ultimately crashing into it. Launched in 2007, Dawn is the only NASA mission to orbit two planetary bodies, a feat made possible by its efficient ion thrusters. In 2011, it arrived at the egg-shaped Vesta, orbiting for a year before departing for Ceres, where it arrived in 2015. Dawn revealed Vesta to be parched, with a composition similar to the inner planets. Ceres proved more of a surprise, with Dawn unveiling a dwarf planet sculpted by a former frozen ocean, with salt-driven activity, including ice volcanoes, continuing to the present day.