"It all comes down to velocity." I did some Newtonian physics here. 1 gram object traveling at 5 x 10^5 cm/s = 1.25 x 10^11 erg/s in CGS units. That is 1.25 x 10^4 joule/s using SI. This 1 gram object is moving along at 5 km/s. It would pack quite a punch