After a journey of three and a half years, the Japan Aerospace Exploration Agency鈥檚 (JAXA) Hayabusa 2 spacecraft is sidling up to its destination, a small asteroid called Ryugu. The probe is now only around 45 kilometres away, slowing down to enter orbit and begin its survey of the asteroid.
The approach is a tricky one, says JAXA鈥檚 Elizabeth Tasker. 鈥淎 tiny mistake can mean you miss the target entirely,鈥� she says. 鈥淭he distances are equivalent to trying to hit a 6 centimetre target in Brazil from Japan.鈥�
Assuming everything goes to plan, Hayabusa 2 will drop off one big lander and three smaller ones on the surface of Ryugu to study the asteroid鈥檚 composition, geology, and temperature. It will also take samples of asteroid dust by shooting a bullet at the surface and then collecting the dust thrown up by the impact.
Advertisement
Bombs away
To collect fresher samples, the spacecraft will follow an even more violent procedure. It is carrying a 2.5 kilogram projectile loaded with high explosives, which will blast the projectile into Ryugu at a speed of 2 kilometres per second. It will then collect fresh dust that hasn鈥檛 been exposed directly to space from the resulting crater.
After deploying the landers, Hayabusa 2 will touch down on Ryugu three times to collect samples in late 2018 and 2019, and taking numerous observations from orbit. The spacecraft will head back home towards Earth at the end of 2019 to return the samples to researchers waiting to analyse their compositions.
Ryugu has an orbit that makes sample return particularly easy 鈥� it swings from just within Earth鈥檚 orbit to just beyond Mars. It鈥檚 a relatively small asteroid, less than a kilometre across, and it spins once every 7.6 hours.
Hayabusa 2鈥檚 first pictures of Ryugu showed an angular rock with a ridge circling its equator. There is a large boulder or cliff about 150 metres across sitting at its top, as well as other apparent clusters of rocks settled on its surface. It is riddled with small depressions that might be craters from collisions with other space rocks.
鈥淚t is generally believed that small asteroids that are less than 1 kilometre, such as Ryugu, were created fairly recently in the solar system鈥檚 history (within several hundred million years) during the fragmentation of a larger parent body,鈥� Hayabusa 2 team member Seiji Sujitaon wrote . 鈥淩yugu鈥檚 terrain will tell us about the division from the parent body and the asteroid鈥檚 subsequent evolution.鈥�
This is important because the parent bodies of asteroids were the building blocks of planets in the early solar system. Studying asteroids like Ryugu can tell us what those building blocks were made of, which may help us determine how certain materials 鈥� like water 鈥� came to be on Earth and other planets.
