Hayabusa 2 Photographs Dark Spot at Asteroid Landing Site

Japan’s Hayabusa 2 probe successfully met the surface of the asteroid Ryugu last week. While it was there, it fired a small bullet into the surface to (hopefully) collect a sample. The probed backed away after making its attack run, but it appears Ryugu has been changed by the encounter. A new image released by the Japan Aerospace Exploration Agency (JAXA) shows a mysterious dark blotch (next to the probe’s shadow) where Hayabusa 2 touched down.
Hayabusa 2 has been in orbit of Ryugu for several months as the JAXA team carefully planned last week’s operation. The original timeline called for Hayabusa 2 to collect its first sample late last year, but the surface of the asteroid was much more craggy than expected. JAXA had to find a place where the sample horn could get all the way down to the surface without running into any obstacles.
We don’t know for certain if Hayabusa 2 actually collected any material from Ryugu, but the tantalus metal slug fired. What we know of the gravity on Ryugu means at least some particles should have traveled up into the sample container. The force of that impact might be responsible for the disruption on the surface now.
Hayabusa 2 captured the above image when it was about 25 meters (82 feet) from the surface. So, that’s a substantial change — see below for a view of the same area before the landing. The impactor was intended to stir things up, so it’s reasonable to expect that it would leave some lasting impression. The team is also exploring the possibility that the spacecraft’s engines played a part in scuffing up the asteroid. It might also be something else entirely.

Hayabusa 2 will perform another sample retrieval late, so the team can look for a similar mark after departing from the new site. That might help nail down the cause, but it’s likely that the material just under the surface has different properties. It hasn’t been bombarded by solar radiation for billions of years, after all. That’s actually why JAXA equipped Hayabusa 2 with its most potent impactor, a 5.5 pound (2.5 kilograms) copper slug.
In April, Hayabusa 2 will use an explosive charge to launch the copper impactor into Ryugu to create a crater. That should allow the probe to descend and obtain a sample of subsurface material — perhaps the same particles that caused the dark splotch we’re looking at now. Hayabusa 2 will send its sample container back to Earth in late 2020. Only then will we find out how much of the asteroid lies inside.
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