Eroica's question was

"What country has the greatest number of impact craters per unit area?"

In other words, which country has the greatest density of impact craters.

Australia has 26 impact craters (Thanks for the link, Eroica! Fascinating information.). It has an area of 7,741,220 km² or 2,988,888 sq mi, which is one impact crater every 297,739 km² or one impact crater every 114,957 sq mi.

Estonia has 4 impact craters. It has an area of 45,226 km² or 17,413 sq mi, which is one impact crater every 11306.5 km² or one impact crater every 4353 sq mi, a much higher density than Australia or apparently anywhere else.

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