The $980m, 12-year mission will explore more asteroids than ever before. If all goes according to plan, the spacecraft will reach its first flyby (an asteroid in the main asteroid belt) in April 2025, followed by seven Trojan asteroids beginning in August 2027. Its path will circle back to Earth three times for gravity assists before landing, making it the first spacecraft to return to Earth from the outer solar system.
The Trojan asteroids orbit the Sun in two elongated swarms: one group ahead of Jupiter in its path, the other behind it. These two regions contain approximately as many asteroids as the main asteroid belt. Observations of these asteroids have led to the suggestion that they may be coated in certain organic polymers formed by solar radiation, and that they may have been captured into their orbits during the early stages of the solar system’s formation.