When news from Mars filtered through the iron curtain, Safronov wasn't in the least bit surprised. If his theory of accretion was correct, then during the final stages of planetary formation the developing worlds would be gravitationally hoovering up the remnants of the dust disk.
Craters are the scars of that process.
When Mariner 10 visited Mercury a decade later it found a world more heavily cratered than our Moon. Craters on planets weren't the exception - they seemed to be the rule. Meteor crater in Arizona is almost a mile wide yet is tiny compared to the gigantic craters found on our planetary neighbours. The crater was made 40,000 years ago - a mere blink of an eye on a planet that's four and a half billion years old. Yet in our solar system there are even more recent evidence that the planets still haven't finished growing.