The Japanese probe Hayabusa 2 successfully met the surface of the asteroid Ryugu last week. When he was there, he shot a small bullet into the surface to collect (hopefully) a sample. The respondents recoiled after launching their attack, but it seems that Ryugu was changed by the meeting. A new image published by Japan Aerospace Exploration Agency (JAXA) shows a mysterious dark spot (near the shadow of the probe) where Hayabusa 2 hit the ground.
Hayabusa 2 has been in orbit around Ryugu for several months as the JAXA team carefully planned last week's operations. The initial schedule provided that Hayabusa 2 collected its first sample at the end of last year, but the surface of the asteroid was much steeper than expected. The JAXA had to find a place where the sampling horn could reach the surface without hitting any obstacle.
We do not know for sure whether Hayabusa 2 actually collected material from Ryugu, but the tantalum metal silt was returned. From what we know of the gravity on Ryugu, at least some particles should have gone back into the sample container. The strength of this impact could be responsible for the disturbance on the surface now.
Hayabusa 2 captured the image above while she was about 25 meters from the surface. So this is a big change – see below for a view of the same area before landing. The impactor was intended to confuse things, so it is reasonable to expect it to leave a lasting impression. The team is also studying the possibility that the engines of the spacecraft have helped eradicate the asteroid. It could also be something else.
Hayabusa 2 will perform another sample collection late so that the team can look for a similar mark after leaving the new site. This may help to determine the cause, but it is likely that the material just below the surface has different properties. It has not been bombarded with solar radiation for billions of years, after all. This is actually why the JAXA has equipped Hayabusa 2 with its most powerful impactor, a 5.5-pound (2.5 kg) copper slug.
In April, Hayabusa 2 will use an explosive charge to launch the copper impactor in Ryugu to create a crater. This should allow the probe to descend and obtain a sample of subsurface material – perhaps the same particles that caused the dark spot that we are currently examining. Hayabusa 2 will send its container of samples to Earth by the end of 2020. This is only while we will know how much of the asteroid is inside.