The primary goal of the Dawn mission is to explore asteroid 4 Vesta and dwarf planet 1 Ceres with the same complement of instruments on a single spacecraft. In-depth analysis and comparison of these two celestial bodies will provide insight into their origin and evolution -- and thus a better understanding of the conditions and processes that have acted upon them from their formation 4.56 billion years ago to the present.

An artist's concept of the Dawn mission. Credit: NASA

During its orbital studies, Dawn will investigate Vesta's and Ceres' internal structure, density and homogeneity by measuring their mass, shape, volume and spin state with radiometric tracking and imagery, and determine elemental and mineral composition. From this information scientists can determine the relationship between meteorites and their parent bodies, and the thermal histories of the bodies. From images of the surface, knowledge of their bombardment, tectonic and possibly volcanic history will be revealed.

In particular, the mission's scientific objectives are to:

• Investigate the internal structure, density and homogeneity of two complementary protoplanets, 1 Ceres and 4 Vesta, one wet and one dry.
  
  
• Determine surface morphology and cratering via near-global surface imagery in three colors at Vesta and in three at Ceres.
  
  
• Perform radio tracking to determine mass, gravity field, principal axes, rotational axis and moments of inertia of both Vesta and Ceres.
  
  
• Determine shape, size, composition and mass of both Vesta and Ceres.
  
  
• Determine thermal history and size of each body's core.
  
  
• Determine the spin axis of both Vesta and Ceres.
  
  
• Understand the role of water in controlling asteroid evolution.
  
  
• Test the prevailing scientific theory that Vesta is the parent body for a class of stony meteorites known as howardite, eucrite and diogenite, or "HED," meteorites; determine which, if any, meteorites come from Vesta.
  
  
• Provide a geologic context for HED meteorites.
  
  
• Obtain surface coverage with the mapping spectrometer from 0.25- to 5.0-micron wavelengths.
  
  
• Obtain neutron and gamma ray spectra to produce maps of the surface elemental composition of each object, including the abundance of major rock-forming elements (oxygen, magnesium, aluminum, silicon, calcium, titanium and iron), trace elements (gadolinium and samarium), and long-lived radioactive elements (potassium, thorium and uranium).