• NASA’s Dawn Mission will be the first to orbit a main belt asteroid, doing a detailed and extensive study of the two largest asteroids Ceres and Vesta

• Scientists will study their surface features and gain insights on their internal structureArtist’s concept of the Dawn spacecraft (NASA)

• Dawn is scheduled for launch on September 27th at the Cape Canaveral Air Force Station on a Delta II 7925H launch vehicle

• With a Mars gravity assist in February 2009, it will arrive at Vesta in October 2011

• It will depart Vesta in May 2012 and arrive at Ceres in August 2015

• The end of the mission is planned for January 2016

The instruments aboardthe spacecraft are:• A visible camera and an

infrared mapping spectrometer to reveal surface minerals

• A gamma ray and neutron spectrometer to determine the elements that make up the asteroids

• The spacecraft will also measure the gravity field of each asteroid

NASA technicians install the instrumentsaboard the Dawn spacecraft

• Dawn’s ion propulsion system allows it to undertake a mission that would have been unaffordable using other technologies

• Two large solar panels stretching 19.7 meters (65 feet) from tip to tip harness the Sun’s energy and power the ion engines

• The energy ionizes the onboard fuel (xenon), accelerates the ions, which in turn accelerate the spacecraft

Dawn spacecraft shown with Ceres (right) and Vesta (left)

in an artist’s image

• These asteroids were chosen because they are two contrasting planetesimals—Ceres is wet and icy and may have subsurface water. Vesta is dry and rocky and may have been formed by volcanoes

• Ceres is about 950 km in diameter and Vesta is about 530 km in diameter

• Both bodies formed early in the history of the solar system

Hubble Telescope images of Ceres (top) and Vesta (bottom)

• Exploring a new frontier, Dawn will journey “back in time,” so to speak, over 4.5 billion years to the beginning of our solar system

• Many thousands of bodies in the main asteroid belt between Mars and Jupiter formed at the same time and in similar environments as the rocky planets (Mercury, Venus, Earth, and Mars)

• Scientists theorize that asteroids were budding planets that were never given the chance to grow due to the gravitational effects of Jupiter

• By investigating these two asteroids, Dawn hopes to unlock some of the mysteries of planetary formation: the conditions and the building blocks under which they were formed

• Dawn will also contrast the formation and evolution of these two small planetesimals that followed very different evolutionary paths so we can understand what controls that evolution

• This can help us in our observation of exoplanets in other planetary systems

Artist’s concept of Dawn spacecraft (NASA)