Is it difficult to retrieve an asteroid sample?
There are mainly two hardships. Firstly, the asteroid is far from Earth. Hayabusa2 had to land on the asteroid Ryugu, which was 300 million kilometres (190 million miles) away. Therefore it’s impossible to steer the spacecraft for landing from Earth. Instead the spacecraft has to think by itself to safely land on the ground and retrieve the sample – a high level of autonomy is mandatory.
Secondly, asteroids are so small that we cannot see their appearance unless we get there. The difficulty of sampling from asteroids is that we have to design a spacecraft and sampling mechanism way before we see them. The spacecraft has to be designed for an unknown asteroid environment, no matter how hard or bumpy the surface is and no matter how strong the gravity is.
Hayabusa2 successfully landed on Ryugu on 22 February 2019. Ryugu is covered by numerous rocks, and there was only a six-metre (16-foot) diameter safe area for the landing. This was quite challenging for the spacecraft.
It’s like throwing a tiny ball from London to make it fly though the hole of a needle in Tokyo.