Dawn
This mission arrived at asteroid Vesta in July 2011, orbited the asteroid for a year and then left Vesta to travel to dwarf planet Ceres in July 2012. The top level question that the mission addresses is the role of size and water in determining the evolution of the planets.
Gravity Recovery and Interior Laboratory (GRAIL)
GRAIL's primary objectives are to help scientists determine the structure of the lunar interior, from crust to core, and to advance understanding of the Moon's thermal evolution. Though the spacecraft are no longer in orbit around the Moon, scientists are still learning from the data they sent back to Earth during their mission.
Mars Reconnaissance Orbiter (MRO)
This mission in orbit around the Red Planet is gathering data to characterize Mars' climate history.
Juno
Juno's principal goal is to understand the origin and evolution of Jupiter. This mission will study Jupiter's magnetic field and other details to help scientists model the interior processes that guide its evolution.
MESSENGER
This mission has been orbiting Mercury since March 2011. Mercury is an extreme among the terrestrial planets. The smallest planet, Mercury has the oldest surface and the largest daily variations in surface temperature. Mercury also is the least explored. Understanding this "end member" among the terrestrial planets is crucial to developing a better understanding of how the planets in our solar system formed and evolved.
