TerryHancock, 
This is really very cool!
The DART mission was wildly successful at changing the trajectory of an asteroid.
It didn't split the asteroid. It didn't produce an ineffectual "puff" of light debris.
It blew away a nice ejecta stream of small particles that acted as reaction mass, converting impact energy to additional momentum. Just about optimal.
This is a big deal: it could be used to save civilization on Earth, someday.
