Out in the Asteroid Belt there are a lot of rocks, obviously. There are two bodies out there that are truly large compared to all the rest. Ceres is considered a dwarf planet, and the other, Vesta, is the largest asteroid known in the Solar System. It makes up about about 9% of the total mass of the Asteroid Belt, and was big enough to be observed from Earth 200 years ago by Heinrich Olbers.
All that is pretty groovy stuff, but in June the Dawn probe from NASA decelerated into orbit around the mini-planet. Since then we have been getting more and more images. The picture above is one such. It is three large craters that overlap just enough to make them look like a snowman.
Now it would be awesome enough for the Dawn probe to just go to Vesta, after all we have not visited too many asteroids and none in the actual asteroid belt before; but this mission is a twofer, once a year of science has been done at Vesta, Dawn will move on to the other big object in the Asteroid Belt, Ceres.
It will take another three years before Dawn arrives at Ceres, but given the opportunity to examine two very different proto-planets, it is worth the wait. You see Ceres is thought to have a thin, but permanent atmosphere, which makes it unique among the small planetoids. It is significantly smaller than our moon so this poses some interesting questions as to what it is made of and where it is from. But probably most importantly, how does a body this small hang on to an atmosphere at all?
Vesta, on the other hand, is believed to have had a molten metal core like the Earth has, and Mars probably did at early points in its history. This is important because it could tell us a lot about how such dynamos are formed and what it looks like as they slow and stop. Just in case you were wondering why that is important, the spinning of the Earth’s metal core generates the magnetic fields that protect us from the fast moving particles of the solar wind from our local star. Some day the dynamo will run down and things will get quite challenging for anything living on our planet.
What makes this mission possible is the ion drive of the Dawn probe. Basically it uses electricity to produce ionized xenon and it can do it for very long periods of time. It is good that it can operate over long periods because it does not provide a lot of push. The thing is, in free fall a little push over a long time can really get you going pretty fast. Since it is electric in nature you can power with giant solar collectors. Even at the farthest distance this mission will travel, it can still produce 1kW. More than enough for it to motor around the Asteroid Belt.
The Dawn probe carries four science instruments: a high resolution framing camera; a visible light and infrared spectrometer; a gamma ray and neutron spectrometer (this will measure isotopes in the crust of both planetoids); and a gravity science instrument that will allow a very accurate mapping of the gravitational field of each body.
Just like all our Solar System explorations, we are likely to learn things we never thought about, prove things that everyone knows, and generate a raft of questions that will only be answered by further exploration.
So watch this space for the next year, Space Cadets! There are going to be tons of pictures and video and I will be your one-stop-shop for it all!
The floor is yours!