The Japanese mission Hayabusa-2 made its closest approach yet to the asteroid Ryugu on 7 August, the Japan Aerospace Exploration Agency (JAXA) says.

Mission control first manoeuvred the probe from its hovering position 20 kilometres above the space rock to an altitude of 6 kilometres. Then it let the probe free-fall down to just 851 metres above the surface to measure Ryugu’s gravitational pull, and therefore its mass.

Ryugu — a near-Earth object with a very dark surface — is a type of asteroid that is common in the Solar System but which has not been closely studied until now (mission operators compared its shape to that of a sweet Japanese dumpling as it came into view). The asteroid is about 1 kilometre in diameter and the newly released images show a mostly flat surface strewn with boulders of various sizes.

Hayabusa-2 launched at the end of 2014 and arrived at Ryugu in June . It is due to release several landers, and the science team aims to use photographic surveys of the surface to pick the best landing locations by 18 August. The probe itself will also touch down to collect samples, which it will return to Earth in 2020. JAXA’s probe Hayabusa, the predecessor to the current craft, became the first mission to return materials from an asteroid to Earth in 2010.