Dawn was the first spacecraft to:
- Visit Ceres or Vesta.
- Orbit an object in the asteroid belt.
- Orbit 2 Solar System objects.
- Visit a dwarf planet.
The aim of the Dawn mission was to learn more about how rocky and icy objects in the Solar System formed. Ceres and Vesta were chosen because they are very different from each other. Ceres is icy and cold, Vesta is rocky. Dawn also tested a new method of powering spacecraft using ion propulsion engines.
Dawn orbited Vesta from July 2011 to September 2012. It found dark carbon-rich areas of the surface made by asteroid impacts. It also confirmed that some meteorites found on Earth had come from Vesta's South Pole.
Dawn orbited Ceres from March 2015 to October 2018. It discovered bright spots on the surface. Scientists think these come from salty water below the surface of Ceres. Part of the reason for visiting Ceres was that scientists thought it once had an ancient ocean which had since frozen. Thanks to Dawn, we know that parts of Ceres's ocean are still liquid. Dawn also found organic matter on Ceres. Organic materials are one of the ingredients for life.