If the same side of the moon always faces the earth, then how did the moon come to have so many impact craters on it? That is to say, how do asteroids strike the moon on the "earth side" without hitting the earth first? Were these just odd, unlucky (for the moon) angles that narrowly missed us, or did the moon at one time rotate faster or slower?

Thanks in advance for any answers

the earth spins on it axis faster than the moon does, the moon revolves us slowly, so the moon revolves on it axis but the motion mean we only see the same side.

I know this, but how did it come to have craters on the earth side?

Well, let's think about it...

The Earth faces one hemisphere of the Moon, primarily (some far side surface comes into view every once in a while). However, the Earth is a relatively small ball of mass some 250,000 miles away. It doesn't shield the Earth facing surface of the Moon from impacts to any great degree at all.


During the crater forming epoch, certainly some impacts that may have impacted the Moon hit the Earth instead. We can't see them, of course, because climatological factors and tectonics have obliterated any evidence of them. But the majority of those on a collision course with the Moon made it there...near side or far side.

The same thing happens today, only on a small scale. We see frequent meteor showers, as the planet passes through cometary tail trails. None of these, for the most part, ever make it to the surface of the Earth...but those that make it to the Moon impact and produce new micro craters all the time...


Let's do a really terrible analogy.

There you stand, the Moon. You've got a shield. It's a disc about 20 feet in diameter. Now, there's a hundred guys out there, hundreds of yards away from you, all with high powered rifles and taking aim on you little 6 foot self. You've got this 20 foot diameter shield right?

However, that shield is 125 feet away from you, and the guys with the rifles are spread out 180 degrees.


How many bullets do you think that shield is going to protect you from at that distance?




That's why the Moon has craters on the near side, and why you're gonna be dead shortly...the shield is too far away to make much of a difference. Lots of bullets are gonna make to you, shield or not.


I know that's a terrible analogy, but hey...I'm trying!

Thanks for putting that in perspective.

Whilst MID is totally correct in his answer there is also another factor to take into account, many of the craters are very old indeed and the Moon wasn't always tidally locked.

when the soar-system was young, the moon used to be closer to earth, this means that the moons orbited the earth much quicker but it still orbited at the same speed, most of the impacts from comets,astroids etc have probably been there since the moon was young, because the moon orbited around the earth faster there was a different face of the moon facing the earth, but the one thing i still havent seen is the other side of the moon :S

Yes! That too!

Actually, the closer the orbit, the faster the orbital speed and the quicker the period...





Here's a look...

HA the near side looks worse! go figure

Dont meteors burn up in our atmosphere also?

Definitely, I wonder why - is it because Earth's gravity has been slinging rocks at it?

Or is it because ancient civilizations tried to blow it up and/or destroy alien bases facing the Earth?

The pictures aren't that great.

The near side is contrasting, certainly, because of the presence of extensive maria, which are smooth, darker benign areas. The aft side is cluttered with nasty terrain and cratering all over it's face.

For the most part, yes indeed they do.
That's one of the primary reasons why Earth doesn't look at all like the Moon!

These maria are lava filled basins. They were formed when the Moon still had molten magma below the surface. They are almost certainly the results of large impacts. The lava was released, filled the low lying areas and then solidified. The maria are more recent than the surrounding areas an so have far fewer impact craters. Why there are virtually none of these maria on the far side is one of the mysteries that remain about the Moon.


That and the presence of liquid water. The constant weathering of the Earth's surface ensures that the Earth has a young appearance. This, in the fact that the majority of the surface is covered in ocean, removes the evidence of the bombardment that Earth has suffered. With no similar weathering the Moon has an ancient surface and it's scars are there for all to see.

excelent question, I want to know also I am a new stargazer..

Very cool, new stargazer.

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