The 2022 Dart impact shortened the moonlet’s orbit around Didymos
The European Space Agency’s Hera spacecraft has begun close inspections of the asteroid that NASA rammed four years ago in a planetary defense test. ESA announced Wednesday that Hera is now studying the asteroid Didymos and its moonlet Dimorphos from just 15 miles to 18 miles (25 to 30 kilometers) away.
Dimorphos is an estimated 500 feet (151 meters) in diameter, while Didymos measures roughly 2,560 feet (780 meters) across.
NASA’s Dart spacecraft — short for Double Asteroid Redirection Test — deliberately slammed into little Dimorphos in 2022 to see whether such a defensive move might help save Earth from a killer space rock one day.
The impact shortened the moonlet’s orbit around Didymos. More importantly, it nudged Dimorphos into a slightly different path around the sun.
The collision also sent rubble and even boulders flying off Dimorphos, giving the strike an extra kick of momentum. The debris trail extended thousands of miles — more than 10,000 kilometers — into space for months, and scientists say some of it could still be in the vicinity.
ESA officials consider the work a “crash site investigation” worthy of the agency’s finest robotic detective.
Hera, a small car-sized spacecraft launched in 2024, will venture even closer next month, to within 12 miles (20 kilometers).
The spacecraft is carrying 25 science instruments for the survey.
Hera also holds a pair of shoebox-sized Cubesats, which will examine Dimorphos even more closely and attempt to land on it.