Dawn
Full Name: Dawn
Phase: Operating
Launch Date: September 27, 2007
Mission Project Home Page: http://dawn.jpl.nasa.gov/
Program(s): Discovery
Dawn's goal is to characterize the conditions and processes of the solar system's earliest epoch by investigating in detail two of the largest protoplanets remaining intact since their formations. Ceres and Vesta reside in the extensive zone between Mars and Jupiter together with many other smaller bodies, called the asteroid belt. Each has followed a very different evolutionary path constrained by the diversity of processes that operated during the first few million years of solar system evolution.
The top level question that the mission addresses is the role of size and water content in determining the evolution of the planets. Ceres and Vesta are the right two bodies with which to address this question, as they are the most massive of the protoplanets, baby planets whose growth was interrupted by the formation of Jupiter. Ceres is very primitive and wet while Vesta is evolved and dry. The instrumentation to be flown is complete, flight- proven and similar to that used for Mercury, Mars, the Moon, Eros and comets. The science team consists of leading experts in the investigation of the rocky and icy planets using proven measurement and analysis techniques.
Dawn has the potential for making many paradigm-shifting discoveries. Ceres may have active hydrological processes leading to seasonal polar caps of water frost, altering our understanding of the interior of these bodies. Vesta may have rocks more strongly magnetized than on Mars, altering our ideas of how and when dynamos arise with important lessons for Mars, Earth and Mercury. Ceres may have a thin, permanent atmosphere distinguishing it from the other minor planets.
The three principal scientific drivers for the mission are first that it captures the earliest moments in the origin of the solar system enabling us to understand the conditions under which these objects formed. Second, Dawn determines the nature of the building blocks from which the terrestrial planets formed, improving our understanding of this formation. Finally, it contrasts the formation and evolution of two small planets that followed very different evolutionary paths so that we understand what controls that evolution.
Enabled by an ion propulsion system, Dawn will be the first mission ever to orbit a main belt asteroid and the first ever to orbit two targets. It also will be the first spacecraft to visit a dwarf planet. The spacecraft is in interplanetary cruise and will fly by Mars in February 2009. Launched: September 27, 2007. Vesta orbit: 2011-2012. Ceres orbit: 2015.