The projectile was released on its collision path on Sunday. Essentially, the washing machine-sized object was pushed into the path of the mountainous block of ice, dust and rock.I guess I want to question the ice idea. This thing appears to be full of perfectly round craters. I don't think a block of ice would look like that if it were struck by some other object or objects.
ML/NJ
It also contains carbon compounds. It has all that would be needed to support life as we know it. On the moon, for example, where water still hasn't been found for sure, but where putting a colony would be a good idea otherwise.
The washing machine hit the pickle.
This object is actually big enough to have its own micro-gravity.
Ice that is moved around will, over time, do what water and glaciers do. It will flow, and fill up small holes.
Don't forget that it is a comet, and occasionally approaches the sun, a significant source of warmth.