Obviously there was the kinetic energy transfer but the impact ejacted some of the asteroids mass opposite to it's trajectory further increasing it's trajectory change.
Cool demonstration, hopefully not needed one day.
Rockets are using mass loss but there's more going on with the rapidly expanding gas causing the increased impulse.
Mandatory sharing of Ben Afleck commentary speaking for all of us.
Instead of pointing out that exact measurements finally came in (of long term movement change), journalist instead focused on the obvious outcome that everyone expects and knows
Captain Obvious strikes again. Is school so low quality, that someone has to write a news article about it and somebody else thinks this is worth posting on a technical forum ?
However, the most efficient method would be actually land (I know - maybe even impossible?) on it, and use propellers to change its trajectory. We don't have too much throwaway high-tech to crash it on asteroids...