Hera captures first view of two separate asteroids

The European Space Agency’s Hera spacecraft has captured its first image resolving the asteroid pair Didymos and Dimorphos as two separate objects — an early milestone for a mission investigating the effects of a spacecraft deliberately crashing into an asteroid to test planetary defence.

Hera took the image on 18 October from 1,280 kilometres away. Dimorphos, the smaller asteroid, appears as a single pixel, clearly separated from Didymos. ESA says the pair had previously appeared to the spacecraft as one dot.

The image follows braking manoeuvres earlier in October that slowed Hera to 20 metres per second relative to the asteroids. The spacecraft is now approaching the pair, which ESA says was about 197 million kilometres from Earth when the image was taken.

Dimorphos is about 151 metres across and orbits the 780-metre Didymos at an average distance of 1.15 kilometres. NASA’s DART spacecraft struck Dimorphos on 26 September 2022, slowing its orbit by about 33 minutes and sending debris across space. The impact demonstrated that a spacecraft could alter an asteroid’s motion, but questions remain about how the collision changed Dimorphos itself.

ESA says Hera is due to take its first detailed images of Dimorphos on 25 November. Over the coming months, it will investigate the impact site using onboard instruments and two small CubeSats, which are intended to approach more closely and eventually land.