Are all planets and satellites in our solar system just as likely to get hit by meteors?

Question

Controlling for surface area and surface age, one naively assumes that all bodies in the solar system share similar numbers of impacts *and* in a similar ratio of large to small impacts. E.g., any 2 bodies in the solar system (scaled to the same size and age) should have a similar number of large, medium, and small craters.

Looking at a list of the largest impact craters in the Solar System, one is tempted to conclude otherwise. It seems that the Moon, Mercury, and Mars bear the most & largest scars from impacts. The MOON in particular seems interesting: compared with similar-sized bodies with similar 'meteor defenses' (e.g. no atmosphere, low tectonics, no volcanism), the Moon seems much more likely to be hit by large meteors than Ganymede and Callisto. It certainly 'outpockmarks' Earth.

Is there some astrophysical phenomenon skewing probability of impact for different bodies in the SS? More to the point, could the Moon have somehow been 'taking all the big hits' for Earth?

Answer 1

No.  And in fact, you stated the answer yourself, at the very beginning of your question: "Controlling for...surface age."  The Earth's surface is considerably younger than that of the Moon, even though the two bodies are, on the whole, around the same age.  On the Earth, weathering and geological activity remove traces of nearly all the impacts, excepting only the most recent, such as Meteor Crater in Arizona.

Ganymede and Callisto are pretty well cratered, but perhaps their cratering rate is affected by the gravitational effect of massive Jupiter.  Also, they exist in a different part of the solar system.  The three bodies you mention are the only significant terrestrial bodies in the inner solar system with no  atmosphere to speak of.  (Phobos and Deimos would have been shattered by any significant impact; in fact, Stickney seems to have almost done the job on its own.)