In the video of the touchdown of Hayabusa 2 (https://www.engadget.com/2019/03/06/hayabusa2-probe-ryugu-touchdown-video/) no debris is visible until touchdown. After that, there is a lot of it (though the shadows cast by individual pieces may bloat that count) - as the 'video' has few individual frames, i am unclear on whether i am actually seeing the same pieces of debris for consecutive frames, but i got the impression that most are moving in a non-radial (from the point of touchdown) direction. Some seem to be falling off the probe as it ascends? In the reflection on the probe itself (upper right quadrant) we can see that there is debris above the probe? Additionally there is no debris visible in the lower left quadrant of the screen? Some of the debris gets 'blow' across the surface? (I am putting question marks behind those statements because i am not sure whether my observations are due to compression artifacts, weird lighting condidtions etc)
What is the debris (i.e. what event precipitated it), and why is it moving so peculiarly?
According to my calculations (input: density 1500kg/m³, radius 500m) the gravity on Ryugu should be about 0.00004g, so i am having a hard time comprehending/imagining what is happening.