Chris McKitterick (mckitterick) wrote,
Chris McKitterick

Astro-Image of the Day: Why is the Moon's far side more heavily cratered?

I got a question about why the Moon's far side is positively loaded with craters compared to the side we can see. Check it out for yourself - here's a map of the far side:

Click the image to see the story.

Compare that to the near side:

Click the image to see the story.

For one, this variation in cratering is evidence that the Moon has been tidally locked with Earth for most of its life, billions of years. But it isn't the Earth that's shielding the Moon from intense cratering on our side, because the Earth presents only a tiny shield to cosmic cannonballs. Scientists have posed many theories as to why this is the case, but most likely it's because the near side has large basaltic flows (the maria), which are both tougher than the standard lunar regolith and likely covered up a lot of pre-existing craters.

/Astronomy lesson.

Tags: astronomy

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