According to the US NASA Jet Propulsion Lab, “System Exploring a new frontier, the Dawn mission will journey back in time over 4.5 billion years to the beginning of our Solar System. How is this “time travel” possible? Many thousands of small bodies orbit the Sun in the asteroid belt—a large region between the orbits of Mars and Jupiter.

They formed at the same time and in similar environments as the bodies that grew to be the rocky planets (Mercury, Venus, Earth, and Mars). Scientists theorize that the asteroids were budding planets and never given the opportunity to grow, due to gravitational stirring by massive Jupiter. Sometimes called minor planets, asteroids contain clues that reveal the conditions and processes acting at the Solar System’s earliest epoch. By investigating two very different asteroids, Ceres and Vesta, the Dawn mission seeks to unlock some of the mysteries of planetary formation.

Dawn’s journey to the asteroid belt, spanning about eight years from launch to completion of data return, is made possible by ion propulsion. Initially tested and proven successful on NASA’s Deep Space 1 mission, this innovative technology is now applied for the first time in

the design and implementation of a dedicated scientific space flight with the Dawn mission. Ion propulsion allows Dawn to undertake a bold and important mission that would be unaffordable—and even impossible—with a more conventional propulsion system. Two large solar panels, stretching approximately 19.7 meters (65 feet) from tip to tip, collect energy from the distant Sun. Within the ion engine, the energy then ionizes the onboard fuel, xenon, accelerating the ions—which, in turn, accelerate the spacecraft.”