NASA’s robotic Dawn spacecraft drifted into orbit around Vesta on Saturday, starting a yearlong science campaign to map one of the solar system’s largest unexplored worlds sandwiched in the main asteroid belt between Mars and Jupiter.

Launched from Earth in September 2007, Dawn spiraled away from the sun with the help of a cutting edge ion propulsion system and a gravity boost from a flyby of Mars.

“Today, we celebrate an incredible exploration milestone as a spacecraft enters orbit around an object in the main asteroid belt for the first time,” said NASA Administrator Charlie Bolden. “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.”

After traveling 1.7 billion miles through space, Dawn approached Vesta this spring before being captured by the asteroid’s weak gravity Saturday. Engineers don’t know exactly when Dawn entered orbit yet because the spacecraft didn’t have to conduct a major maneuver like many other interplanetary missions.

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