Mission’s end

With the depletion of its hydrazine fuel, the Dawn spacecraft would have entered several safe modes as the onboard computer attempted to identify and rectify the issue. But there is no solution for a lack of fuel, and though the spacecraft would have shut down its systems and run off battery power, that battery cannot be recharged if the craft is unable to orient its solar panels toward the Sun. One of the systems it would have shut down is its radio, to be turned on only after power was restored — a situation that will not occur without the ability to point.In its 11 years, Dawn has traveled a total of 4.3 billion miles (6.9 billion kilometers) and accomplished a long list of firsts. Now, it will remain in orbit around Ceres for decades, circling the world for at least 20 to 50 years. That’s intentional, as Ceres has conditions that could be right for life, and engineers want to prevent contact between the spacecraft (and any potential Earth microbes it may carry) and the dwarf planet. Planetary protection protocols currently in place prohibit it from touching the surface for at least 20 years, which is enough time for a potential follow-up mission if the world is given a higher priority for protection.The end of the Dawn mission comes only two days after NASA’s Kepler space telescope was also retired due to a lack of fuel. Though both endings were expected losses, both have silver linings. Not only do these two amazing spacecraft leave behind an immense wealth of data, they are also succeeded by other projects. Hayabusa2, currently in orbit around the asteroid Ryugu, has sent several landers to its surface and will gather samples of the asteroid before returning to Earth in a few years. Comparing those samples to what researchers have learned about Vesta and Ceres will bring our picture of the solar system’s past and present into ever-sharper focus.