South Pole–Aitken basin

The South Pole–Aitken basin (SPA Basin, ) is an immense impact crater on the far side of the Moon. At roughly 2,500 km (1,600 mi) in diameter and between 6.2 and 8.2 km (3.9–5.1 mi) deep, it is one of the largest known impact craters in the Solar System. It is the largest, oldest, and deepest basin recognized on the Moon. It is estimated that it was formed during the pre-Nectarian epoch, with radiometric dating of lunar zircons proposed to originate from the basin suggesting a precise age of 4.338 billion years. It was named for two features on opposite sides of the basin: the lunar South Pole at one end and the crater Aitken on the northern end. The outer rim of this basin can be seen from Earth as a huge mountain chain located on the Moon's southern limb, sometimes informally called "Leibnitz mountains".

On 3 January 2019, the Chinese spacecraft Chang'e 4 landed in the basin, specifically within a crater called Von Kármán. In May 2019, scientists announced that a large mass of material had been identified deep within the crater. Chang'e 6 collected a sample from this crater, specifically within the Apollo basin.