South Pole–Aitken basin
Topographic map of the South Pole–Aitken basin based on Kaguya data. Red represents high elevation, purple represents low elevation. The purple and grey elliptical rings trace the inner and outer walls of the basin. (The black ring is an old artifact of the image.) | |
| Coordinates | 53°S 169°W / 53°S 169°W |
|---|---|
| Diameter | About 2,500 km (1,600 mi) |
| Depth | Between 6.2 and 8.2 km (3.9–5.1 mi) |
| Eponym | Lunar south pole Aitken (crater) |
The South Pole–Aitken basin (SPA Basin, /ˈeɪtkɪn/) 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 approximately 4.2 to 4.3 billion years ago, 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 Chang'e 4, a Chinese spacecraft, 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 aims to collect sample from this crater, specifically within the Apollo basin.