Breaking up a rubble pile asteroid impacter

Frogwatch wrote:

This brings up another topic that interests me: Why do we see so few
impact features on the earth? The usual reason is weathering and
plate tectonics but even on Venus we see them and it has extreme
weathering. We see impact features on Europa with an extreme version
of plate tectonics with big plates of ice moving over an ocean
underneath.

Most of the objects that enter the Earth's atmosphere are fairly small
in size and break up before they hit the surface due to the rapid
deceleration they experience on the way down. In the case of a lot of
them they are so fragile to begin with that they break up into very
small pieces during entry so that almost nothing gets to the ground,
like in the Tunguska blast. Since crater size is a function of both the
mass of the impactor and its impact velocity, the small pieces slow down
in the atmosphere enough that they just fall out of the sky at their
terminal velocity, like you had tossed them out of an aircraft at high
altitude, rather than keeping any of the high velocity they had as they
traveled through space.
Venus has such a dense atmosphere that most objects break up before
impact and only the biggest chunks get through to make any crater on the
surface; the smallest single-impact crater spotted on Venus was 3 km in
diameter (smaller ones are sub-craters created by parts of a object that
had broken up on the way down).
Also, without water weathering from rain or rivers, frequent day-night
temperature extremes, and high surface winds, weathering moves very
slowly on Venus.
Article on Venus cratering he http://www.solarviews.com/eng/vencrate.htm

Pat