Hera Begins Close Study of NASA-Struck Asteroid Pair

Hera is studying Didymos and its small companion, Dimorphos, from about 25 to 30 kilometers away. The European Space Agency says the spacecraft reached the pair on November 4, after more than two years in space, and has now begun close observations of the impact site.

NASA’s DART spacecraft deliberately hit Dimorphos in 2022 to test whether a spacecraft could alter an asteroid’s course. The collision cut the time Dimorphos takes to circle Didymos by over 30 minutes and also shifted its path around the sun. The impact sent rocks and debris into space, with a trail stretching more than 10,000 kilometers.

Hera will move to within 20 kilometers of the system next month. It carries 25 scientific instruments and two small companion spacecraft, which are expected to make closer observations and attempt a landing on Dimorphos in January. One, Juventas, carries radar designed to probe the moonlet’s interior.

Scientists hope the mission will reveal how Dimorphos is built, how the collision changed it and whether material continues to move between the two bodies. The findings could improve understanding of binary asteroids and help shape future planetary-defense efforts. Dimorphos is about 151 meters across; Didymos measures roughly 780 meters.