20
$\begingroup$

I saw this picture on the BBC news website.

enter image description here

There appears to be a ring of craters in the center of the picture, aligned in an approximate sub vertical orientation.

Am I just seeing things or does this apparent ring of craters a feature and does it extend to the far side of the moon? If it does exist, what form of bombardment or gravitational attraction would have create such a ring?

$\endgroup$

1 Answer 1

45
$\begingroup$

Actually, most of the surface of the Moon is covered with craters like that. The exception are the large dark 'seas', which are in fact basaltic plains. The seas are mostly present on this side of the moon; the far side of the moon is almost entirely composed of craters.

The reason you see a ring near the terminator (the boundary between the illuminated and dark part) is that the shadows make the craters much more visible.

Due to the angle at which sunlight strikes this portion of the Moon, shadows cast by craters and other geological features are elongated, thereby making such features more apparent to the observer. This phenomenon is similar to the lengthening of shadows on Earth when the Sun is low in the sky.

$\endgroup$
3
  • 2
    $\begingroup$ Exactly. When observing the half-moon in a telescope, craters are easily visible near the terminator. They are much less visible far from the terminator, on both sides. You need long shadows to make visible features such as craters, mountains, etc. $\endgroup$ Commented May 26, 2019 at 22:32
  • 1
    $\begingroup$ The illlumination of the Moon in that image is very weird -- if the terminator is down the middle, then what is the highlight on the far left margin, making it look close to new at first glance? Seems some pretty heavy contrast adjustments have been made in postprocessing. $\endgroup$ Commented May 28, 2019 at 13:52
  • 1
    $\begingroup$ @HenningMakholm There is most definitely some significant post-processing at work here. In addition to the tweaked contrast between the dark and light sides, the background stars are too visible, and the "halo" looks... odd. $\endgroup$ Commented May 28, 2019 at 14:41

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .