Using data provided by Lunar Reconnaissance Orbiter spacecraft since 2009, NASA has published an amazing virtual Moon tour in 4K Ultra HD. In the image here, The South Pole-Aitken basin can be seen – a large lunar impact crater that lies on the far side of the Moon. At roughly 2,500 kilometers (1,600 mi) in diameter and 13 kilometers (8.1 mi) deep, it is one of the largest known impact craters in the Solar System and the largest, oldest, and deepest basin recognized on the Moon. It was named for two features on opposing sides: the crater Aitken (named for the American astronomer Robert Grant Aitken, December 31, 1864 – October 29, 1951) on the northern end and the lunar south pole at the other end. The outer rim of this basin can be seen from Earth as a huge chain of mountains located on the Moon’s southern limb, sometimes informally called “Leibnitz mountains”. Simulations of near vertical impacts show that this basin should have dug up vast amounts of mantle materials from depths as great as 200 km below the surface. However, observations thus far do not favor a mantle composition for this basin, and crustal thickness maps seem to indicate the presence of about 10 kilometers of crustal materials beneath this basin’s floor. This has suggested to some that the basin was not formed by a typical high-velocity impact, but may instead have been formed by a low-velocity projectile around 200 km in diameter that hit at a low angle (about 30 degrees or less), and hence did not dig very deeply into the Moon. Putative evidence for this comes from the high elevations north-east of the rim of the South Pole-Aitken basin that might represent ejecta from such an oblique impact. The impact theory would also account for magnetic anomalies on the moon.