- Who
- South Pole-Aitken Basin
- What
- 2,500 kilometre(s)
- Where
- Not Applicable ()
The largest confirmed impact basin in the Solar System is the South Pole-Aitken Basin, located on the Moon. This colossal impact structure is typically described as a broadly circular structure with a diameter of around 2,500 km (1,553 mi) and a maximum depth of around 13 km (8 miles).
The South Pole-Aitken Basin was likely created by a major impact around 3.9 billion years ago (during a period known as the late heavy bombardment). Its location on the far side of the Moon means that, despite having been present on our closest neighbour for the entirety of human history, the South Pole-Aitken Basin was totally unknown to science until the second half of the 20th century.
It was first glimpsed as a smudgy, indistinct feature on the grainy pictures returned by the Soviet Union's 1959 Luna 3 spacecraft, but wasn't photographed in enough detail to conclusively identify it as an impact basin until after the Lunar Orbiter missions mapped the Moon in 1966 and 1967.
The more detailed topographic data provided by NASA's Lunar Reconnaissance Orbiter (2009–present) and JAXA's SELENE probe (2007), have led some researchers to characterize the South Pole-Aitken Basin as an ellipsoid feature measuring around 2,400 km long and 2,050 km wide (1,491 x 1,273 miles). This revised geometry is consistent with the theory that it was created by a extremely large impactor that struck the moon at a sharply oblique angle.
Research published in June 2019 revealed the presence of a dense mass anomaly located just below the surface of the southern half of the basin. This anomaly, which has a mass of around 2.18 x 10^18 kg, may be the metallic core of the impactor that created the basin.
