Image of the rocky surface of Ryugu

This image was taken as one of the landers was deployed by Hayabusa2 just 60 metres above Ryugu's surface © JAXA 

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Hayabusa2 lands two rovers on asteroid Ryugu

The Japanese space agency (JAXA) has landed two small robots on the surface of an asteroid, making history as the first mobile rovers ever to have done so.

It has taken over three and a half years for the spacecraft Hayabusa2 to make its 319 million kilometre journey to the asteroid Ryugu. Arriving at the asteroid in June, the spacecraft has spent the last few months surveying the small diamond-shaped rock from orbit, mapping its features and sending back images.

This weekend saw the start of the next phase of the mission. Hayabusa2 flew to within just 60 metres of the asteroid's surface, before successfully deploying two small robots. Both rovers appear to have landed safely on Ryugu, even snapping images as they descended onto the rocky body.    

Dr Ashley King, a researcher at the Museum studying the formation of the solar system, says, 'The successful landing of MINERVA-II1 is really exciting because it’s the first time anybody has put mobile rovers on the surface of asteroid.

'I was lucky enough to be in Japan when the Hayabusa-2 mission launched in 2014 and to now see it actually start to a reveal some of Ryugu’s secrets is amazing.'

This is the first time that rovers which can move about have been landed on an asteroid.

The grey rocky surface of the asteroid

This is the first time that moving rovers have landed on an asteroid © JAXA

Yuichi Tsuda, project manager for Hayabusa2, says, 'I cannot find words to express how happy I am that we were able to realise mobile exploration on the surface of an asteroid. I am proud that Hayabusa2 was able to contribute to the creation of this technology for a new method of space exploration by surface movement on small bodies.'

Touch down

The two small rovers are identically shaped squat cylinders, which were deployed from a container known as MINERVA-II1.

Weighing just a kilogramme each, they contain a range of technology to help better understand what the surface of Ryugu is actually like, including both wide-angle and stereo cameras, as well as sensors that will help measure the temperature. The most exciting part about them, however, is the fact that they can move.

Helena Bates is conducting a PhD at the Museum, exploring how water-rich asteroids like Ryugu formed in space.

'The rovers themselves can actually move around on the surface, which allows them to conduct experiments in multiple locations on the surface,' explains Helena. 'They essentially "hop" around which, for lack of a better word, is adorable.'

By taking advantage of the low gravity on Ryugu, the rovers will be able to bounce over the surface. They should be able to hop up to 15 metres, staying airborne for 15 minutes at a time. One of the rovers has been confirmed as already moving across Ryugu. 

The two small biscuit-tin shaped rovers

The two small rovers will 'hop' along the asteroid © JAXA

Origins of the solar system

Asteroids such as Ryugu are of such immense interest to scientists because they are made from the debris that was floating in the disc-shaped cloud of gas and dust known as the solar nebula, after the formation of the Sun.

'They are little snapshots of what the solar nebula looked like before there were planets,' explains Helena.  

The two rovers will be joined at the beginning of October by a third lander called MASCOT to measure the structure of the minerals, thermal behaviour and magnetic properties of the asteroid. Towards the end of the month, Hayabusa2 itself will descend and touch Ryugu to pick up its first sample.

The final part of the mission will fire an explosive copper projectile into the asteroid. This is expected to form a small impact crater exposing the subsurface material that has been shielded from billions of years of weathering. The spacecraft will then collect a second sample, before returning to Earth with its precious cargo.

'I just can't believe that I am lucky enough to be working in this field while these incredible things are happening,' says Helena. 'It's unbelievable.'