The first landing of the Hayabusa2 spacecraft on the Ryugu asteroid is scheduled for this week. If successful, the craft will shoot a ball into the rock to capture samples to bring back to Earth.
The Japanese Aerospace Exploration Agency (JAXA) is preparing for the feel of the probe and recreated the asteroid and the bullet here on Earth to practice, according to a press release. This followed a delay on the expected touch, after the scientists realized that the composition of the asteroid was different from their expectations.
Japanese scientists expect to find a "powdered regolith" on the asteroid, according to the statement. But when the MASCOT and MINERVA-II1 tractors dropped by Hayabusa2 rode to the surface, they discovered that it was actually covered with gravel one centimeter in size. The team delayed touching the probe to ensure that its collection mechanism would still work with a larger grain.
The researchers' tests consisted of firing a similar 5 gram bullet made from the tantalum element into a pile of gravel in a vacuum chamber at 300 meters per second. Fortunately, these tests revealed that the ball would break and release enough material of the right size to allow Hayabusa2 to collect samples.
The JAXA version indicates that the team performed the Earth gravity tests and that more rocks would be released under the microgravity conditions of the asteroid.
Hayabusa2 was launched in 2014 to make appointments and collect samples of the Ryugu asteroid. He succeeds Hayabusa's challenging but ultimately successful mission and joins NASA's OSIRIS-REx as one of two missions currently exploring asteroids.
If successful, Hayabusa2 will take three samples from Ryugu's surface and return them to a capsule on Earth in December 2020.