Dawn Spacecraft Enters Orbit Around Asteroid Vesta
July 22, 2011
On July 16, the Dawn spacecraft became the first probe ever to enter orbit around an object in the main asteroid belt between Mars and Jupiter.
Dawn will study the asteroid, named Vesta, for a year before departing for a second destination, a dwarf planet named Ceres, in July 2012. Observations will provide unprecedented data to help scientists understand the earliest chapter of our solar system. The data also will help pave the way for future human space missions.
"Asteroids provide important clues to the very earliest history of the solar system. Vesta is special because it is the only large asteroid that had volcanic activity when it formed. Over the next year, Dawn's exploration of Vesta will help us to understand the processes that affected the history of this unique asteroid," said Walter Kiefer, staff scientist at the Lunar and Planetary Institute, who is a member of the Dawn mission science team.
NASA Administrator Charles Bolden called the Dawn mission’s successful orbital entry an incredible exploration milestone. He added, “Dawn’s study of the asteroid Vesta marks a major scientific accomplishment and also points the way to the future destinations where people will travel in the coming years. President Obama has directed NASA to send astronauts to an asteroid by 2025, and Dawn is gathering crucial data that will inform that mission.”
The spacecraft relayed information to confirm it entered Vesta’s orbit, but the precise time this milestone occurred was unknown at that time. The time of Dawn’s capture depended on Vesta’s mass and gravity, which only has been estimated until now. The asteroid’s mass determines the strength of its gravitational pull. If Vesta is more massive, its gravity is stronger, meaning it pulled Dawn into orbit sooner. If the asteroid is less massive, its gravity is weaker and it would have taken the spacecraft longer to achieve orbit. With Dawn now in orbit, the science team can take more accurate measurements of Vesta’s gravity and gather more accurate timeline information.
Dawn, which launched in September 2007, is on track to become the first spacecraft to orbit two solar system destinations beyond Earth. The mission to Vesta and Ceres is managed by NASA’s Jet Propulsion Laboratory, and is a project of NASA’s Discovery Program.
For information about the Dawn mission, visit
Last updated July 22, 2011