How Young is the Lunar Crater Giordano Bruno? Is it possible that people witnessed the impact event that made this crater in the year 1178 or did it form long, long ago? Small craters on its ejecta blanket were counted to derive a formation age of Giordano Bruno.

How Young is the Lunar Crater Giordano Bruno? On the left chart, the crater size-frequency distribution for small craters counted on the ejecta blanket of Giordano Bruno falls between 1 to 10 million years, not younger. On the right, Giordano Bruno plots at 4 million years on this lunar cratering chronology.

How Young is the Lunar Crater Giordano Bruno? Complication: Some or all of the small craters could be secondary craters formed by the Giordano Bruno event. Counting secondaries leads to an overestimate of the age. But is Giordano Bruno 2 million or 832 years old? Example of cluster of secondary craters on the farside of the Moon 150 m