NASA’s Dawn started orbiting the dwarf planet Ceres last Friday, making it the first spacecraft to ever orbit a dwarf planet. After a seven and a half year, 3.1 billion mile journey, Dawn reached the small, icy protoplanet that orbits the Sun in the asteroid belt between Mars and Jupiter.
Ceres has been a bit of a headache since its discovery in 1801 as it hasn’t easily fallen into a category. First it was a planet, then labeled an asteroid, and now has been declared a dwarf planet, like our old friend Pluto. Characteristically, this confusion makes sense. It’s small, about the size of Texas, but too big for an asteroid as it’s about a third the mass of the whole asteroid belt. And it’s round like a planet, not misshapen and lumpy like an asteroid. But again, super small. Astronomers believe it is a leftover piece from planetary building blocks that formed the solar system some four and a half billion years ago.
Dawn has a lot of work to do before its fuel runs out. The craft will make a world map of the tiny planet, and then a survey orbit, and then a mapping orbit, and then a picture taking orbit, and then a mapping of the elements orbit. Astronomers are looking forward to finding out if Ceres has ice or mineral salt deposits, or maybe even reservoirs of liquid seawater.
What a rush (…of water, maybe. We’ll see).