Remember last month when I posted that incredible super-hi-res image of the Moon’s near side? A lot of folks asked if an image of the far side were coming soon.

Ask, and ye shall receive.

Holy Selene! Click to enlunanate.

This amazing mosaic is from the Lunar Reconnaissance Orbiter, circling the Moon from a height of a mere 50 km (30 miles) and mapping that entire world. This image is comprised of a whopping 15,000 images from the Wide Angle Camera — yegads! — and shows the side of the Moon we can never see from home.

It looks really different than the near side, doesn’t it? It’s almost entirely craters, while the side we see is dominated by huge lava filled basins called maria (Latin for "seas"). Why is that? Well, it’s known that the crust on the near side is thinner, so it’s easier for big impacts to have punched holes in the crust and allowed magma to bubble up (this was billions of years ago when the inner Moon was still molten).

But why does one side have a thick crust and the ...