Question about the Lunar poles

[george7378]

Hi all,

I have just been looking at the Moon through my Grandad's telescope (really interesting!), and I have a question:

Why are the poles covered in a dense multitude of craters, but the ones nearer to the equator are much sparser in number?

 

[RisingFury]

http://upload.wikimedia.org/wikipedia/commons/d/de/MoonTopoGeoidUSGS.jpg

If you look at the topography of the Moon, you'll notice that this statement is true for the near side, but the far side only shows a little bit of difference.

My guess would be that the near side is shielded from impacts by Earth - imagine: It's roughly 25 times more likely for an object to hit Earth, then it is for it to hit the Moon. If an object on approach hits the Moon before it gets to Earth, then it will certainly hit the far side or the poles. But, if the object first has to pass by Earth and only then has the chance to hit the Moon.. well, it's likely that such approach will make it hit the Earth - or Earth's gravity will divert it.

Now... about the poles...

If the object comes from the far side of the Moon and is then then slung around by gravity, it might have more chance to hit the polar area... so the poles don't get "shielded" by Earth.

 

[george7378]

OK - thanks very much for the information. I can't wait to have another look!

 

[RisingFury]

Like I said, it's only a guess... but it sure is interesting to see the craters.

Also, next time you look through the scope, look for shadows. They'll give you an idea of depth...

Also, the topography around the poles seems to be more... interesting... then the rest

 

[Andy44]

My guess was that the near side of the moon actually took very large and heavy impacts, melting the rock and creating the seas and masscons. The masscons, in turn, became one end of the tidally-locked moon, which was a 50-50 chance. By the time the moon had become tidally locked and settled down the massive bombardments of the early solar system had passed.

Now, this is all just a hypothesis in my head, so take it all with a grain of salt. It's just for the sake of conversation.

---------- Post added at 10:17 PM ---------- Previous post was at 09:51 PM ----------

Actually, Rising Fury, after thinking about it your theory sounds better, especially if the moon started off as part of the earth and formed in a collison, which is a popular theory of lunar formation.

Reason being that the moon would have tidally locked right from the beginning, and would have spiralled away from the earth starting at a very low altitude, making the near side much better shielded than the far side, which took more meteor strikes as the moon spiralled out to higher and higher altitudes...

 

[Salamander]

it's a combination of all the above, and additionally there's a geometric reason as well. from our point of view, the center of the moon has the area spread out, while towards the visual edge the area gets compressed.

if you look at a golf ball from a distance for example, the little dents in it will apear to be denser towards the edge, though they are evenly spaced out over the surface of it.

 

[RisingFury]

it's a combination of all the above, and additionally there's a geometric reason as well. from our point of view, the center of the moon has the area spread out, while towards the visual edge the area gets compressed.

if you look at a golf ball from a distance for example, the little dents in it will apear to be denser towards the edge, though they are evenly spaced out over the surface of it.

That's very true and it probably adds to the illusion a bit, but the poles, edges and far side really do have more craters.

 

[george7378]

Yes - the satellite pictures show a dense multitude at the poles too.