Imbrium does have radial structures extending in many directions, with tightly spaced
secondary crater chains prominent around the crater Ptolemaeas to the south.
To the west, Copernicus and its retinue of tiny
secondary crater pits were sharply rendered, and even the tiny, dark-haloed crater Copernicus H was easy to see.
This alignment of craters points back to the western side of the Imbrium Basin--so could these be a string of large
secondary craters like the ones radiating from the Orientale Basin on the lunar farside?
Close to the crater rim, this ejecta deposit forms a continuous blanket smothering the underlying terrain; further out, the ejecta lands as a scattered assortment of fine grained dust and larger bombs that may themselves form small
secondary craters. In addition to cratering the surface of the Earth, an impact event initiates several other processes that may have severe environmental consequences.
"Clusters of craters may also be created when a large impact ejects rock fragments with such force that they travel from a few kilometres to hundreds of kilometers before returning to the surface, creating new impacts called
secondary craters," ESA adds.
Other portraits show details of a surprisingly high number of
secondary craters, small pockmarks created during the formation of larger craters.
With your telescope, look closely at Copernicus's ray system in Mare Imbrium, near the crater Pytheas, and you can see where Copernicus's ejected material excavated numerous small
secondary craters.
Some of this includes coherent chunks large enough to create
secondary craters.
But some lettered craters are true
secondary craters, excavated by ejecta thrown out by the formation of their named crater.
Shoemaker noticed that the 59-km-wide crater Eratosthenes, which interrupts the Montes Apenninus, has small
secondary craters and faint rays visible at full Moon on the nearby plains of Mare Imbrium.
Studies of high-resolution spacecraft images demonstrate that at the meter scale, there are millions of
secondary craters for every large primary.