Quadrant 46:
— Images and text provided by Howard Eskildsen
Lansberg to Mare Cognitum
This region features broad expanses of
basaltic lava plains interrupted by craters large
and small, fresh or ruined. Mountain peaks
punctuate the landscape here and there, and
rocky rubble litters the upper right margin of
this image. All tell stories, like the pages of a
book, of triumph and disaster on the moon.
Lansberg at the top of the image is well
preserved with all the features of a large
crater distinct, except for the absence of
rays radiating from its rim. Simple craters
such as Euclides, Eppinger, Kuiper and
Darney dot the landscape as well. Of the four
mentioned, only Euclides shows any hints of
rays suggesting that the others are more than a
billion years old, since space weathering tends
to eliminate rays within a billion years. This
is partly due to “gardening” from meteoroids
impacting and from the effects of solar wind
changing iron oxides into tiny flecks of iron
known as nanophase iron, which gives the
undisturbed lunar surface its characteristic color. Other
unlabeled craters also show some rays, revealing their
“youthful” Copernican age.
Mountains also punctuate the surface as isolated
peaks or as curious partial arcs, such as the Riphaeus
Mountains. Look closely and you will find other curving
ridges. They all hint at the primary cause of mountain
building on the moon: crater-forming impacts. They
were all at one time or another parts of crater rims, but
were subsequently partially buried or eroded into their
current forms. The burying is obviously from the lavas,
also known as mare basalts that pave much of the visible
surface in this image. But what could cause massive
erosion and scouring such as seen at Fra Mauro,
Bonpland and Parry?
The region labeled Imbrium Ejecta is similar to the
rough rubble 6VV