Part of NASA’s Discovery Program, Dawn is a mission to the two oldest and most massive bodies in the asteroids belt – Vesta and Ceres, These diverse worlds offer scientific snapshots of the birth of our solar system 4.6 billion years ago. Asteroid Vesta is rocky, while dwarf planet Ceres appears to be icy. Together they bridge the rocky worlds of the inner solar system and the ice bodies far beyond Saturn. By using the same instruments to study diverse destinations, Dawn is uncovering new insight into the early solar system. Powered by an efficient ion engine, Dawn was the first mission to orbit a main belt asteroid. And it was the first to visit a dwarf planet and orbit two targets on a single mission.

Dawn delves into the unknown and achieves what's never been attempted before. A mission in NASA's Discovery Program, Dawn orbited and explored the giant protoplanet Vesta in 2011-2012, and now it is in orbit and exploring a second new world, dwarf planet Ceres.

Dawn's goal is to characterize the conditions and processes of its earliest history by investigating in detail two of the largest protoplanets remaining intact since their formation. Ceres and Vesta reside in the main asteroid belt, the extensive region between Mars and Jupiter, along with many other smaller bodies. Each followed a very different evolutionary path, constrained by the diversity of processes that operated during the first few million years of solar system evolution. When Dawn visited Ceres and Vesta, the spacecraft stepped us back in solar system time.

Major Engineering Achievements:

  • First space mission to orbit two worlds
  • Record-breaking use of solar-electric propulsion: 11km/s in space Δv, 2.5x any prior spacecraft and nearly equal to the impulse provided by Dawn’s Delta launch vehicle
  • Active powered flight 65% of the time, equivalent to 5.5 years of continuous thrust.

Mission Findings:

Dawn orbited Vesta for more than a year, from July 2011 to September 2012. Its investigation confirmed that Vesta is the parent of the HED meteorites: from a faraway but now-characterzed basin came a large collection of well-studied meteorites, a priceless cosmic connection between samples in hand and a singular event on a major planetesimal. Vesta is small enough) about the same size as Enceladus) to have been deeply scarred by the Rheasilivia impact that launched the HEDs; but large enough to have differentiated into iron core, silicate mantle, and igneous crust. Paradoxically, its surface also contains hydrated minerals.

After its unprecedented escape from Vesta and its onward journey, Dawn entered orbit around Ceres in March 2015. Dawn discovered that the inner solar system’s only dwarf planet, albeit never fully differentiated, was an ocean world where water and ammonia of unknown provenance reacted with silicate rocks. As the ocean world froze and sublimed into space, salts and other telltale minerals concentrated into deposits that are now exposed vividly in many locations across the surface, awaiting easy sampling by future missions. Ceres thus joins Mars as a small, accessible world where we can learn how ancient oceans may have existed.

Partners:

The Jet Propulsion Laboratory manages Dawn’s mission to Vesta and Ceres for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena. The Max Planck Institute provided the framing cameras for Solar System Research, Gottingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The visible and infrared mapping spectrometer was funded and coordinated by the Italian Space Agency and built by SELEX ES, with the scientific leadership of the Institute for Space Astrophysics and Planetology, Italian National Institute for Astrophysics, Italy, and is operated by the Institute for Space Astrophysics and Planetology, Rome, Italy. The gamma ray and neutron detector was built by Los Alamos National Laboratory, New Mexico, and is operated by the Planetary Science Institute, Tucson, Arizona.