Measuring around 2,500km (1,600 mi) in diameter and 13km (8.1 mi) deep the Moon's South Pole-Aitken Basin is one of the largest and deepest impact craters in the solar system. As you can see from the below topography taken by NASA's Clementine spacecraft, South Pole-Aitken Basin is the lowest elevation of the Moon.

This basin was named for two features on opposing sides: Aitken crater (imaged below) to the north and the Moon's south pole.

(Image Source: NASA/JSC/Arizona State University)

The size of the South Pole-Aitken Basin led scientists to believe that the impact should have exposed the lunar mantle and caused the basin to be full of mantle material. There is a slightly elevated amount of iron, titanium, and thorium in the basin and much more of some pyroxene minerals than is found at higher elevations. Despite this, scientists have determined that there is still 15km of crust below the basin's surface, which implies the impact did not break through to the mantle.

The origin of the South Pole-Aitken Basin's different composition is still controversial. It's unlikely we will know why the basin's composition differs from elsewhere on the Moon until we send a sample-return or manned mission.

The Moon is a fascinating place and the South Pole-Aitken Basin is one of it's many extraordinary features.

Be sure to follow @MyMoonLPI on Twitter if you are interested in the Moon!

by: David G.

Wednesday Dec-07-2011