The European Space Agency’s Hera spacecraft has embarked on a two-year mission to study a small asteroid previously impacted by NASA’s Dart spacecraft. This mission marks the second phase of a planetary defense test aimed at preparing for potential threats from space rocks that could endanger Earth.

Launched aboard SpaceX’s Falcon rocket, Hera disappeared into late morning clouds on Monday as it set out on its historic voyage. An hour following launch, celebration erupted in Germany’s control center when the spacecraft successfully separated from the rocket’s upper stage and established communication with Earth.

“It’s an amazing day,” ESA’s director general, Josef Aschbacher, said, the Associated Press reported.

NASA’s Dart mission, conducted in 2022, demonstrated the possibility of altering an asteroid’s trajectory. By colliding with Dimorphos, a moonlet of the larger asteroid Didymos, Dart successfully shortened its orbit. The experiment showcased the potential to deflect a hazardous asteroid given ample warning time.

Scientists are particularly interested in studying the aftermath of the Dart impact to gauge its success and consider possible future adjustments. Key questions remain about whether Dart left a crater or significantly altered the form of the 500-foot asteroid.

The impact scattered debris, including boulders, creating a trail that extended more than 10,000 kilometers into space for months. Some of the debris might still surround the asteroid, potentially posing risks to Hera.

Described by European officials as a “crash scene investigation,” the $400 million mission aims to gather critical scientific and technical data. The project manager, Ian Carnelli, likened the mission to returning to a crime scene, stating, “Hera is going back to the crime site and getting all the scientific and technical information.”

Equipped with a dozen scientific instruments, Hera will swing by Mars in 2025 to gain a gravitational boost en route to Dimorphos. The asteroid pair, Didymos and Dimorphos, will be positioned 120 million miles from Earth when Hera arrives at the end of 2026.

Hera is expected to orbit the asteroid duo, gradually reducing its flyby distance to just 1 kilometer from 30 kilometers. Over six months, the spacecraft will conduct an extensive survey to ascertain Dimorphos’s mass, composition, and orbital relationship with Didymos.