South Pole–Aitken basin
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.[1] It is estimated that it was formed 4.2 to 4.3 billion years ago, during the Pre-Nectarian epoch.[2] 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
Discovery
The existence of a giant far side basin was suspected as early as 1962 based on early Soviet probe images (namely
Physical characteristics
The South Pole–Aitken basin is the largest, deepest and oldest basin recognized on the Moon.[1] The lowest elevations of the Moon (about −6000 m) are located within the South Pole–Aitken basin, and the highest peaks (about +8000 m) are found on this basin's north-eastern rim, which are sometimes called the Leibnitz Mountains.[10] Because of this basin's great size, the crust at this locale is expected to be thinner than typical as a result of the large amount of material that was excavated due to an impact. Crustal thickness maps constructed using the Moon's topography and gravity field imply a thickness of about 30 km beneath the floor of this basin, in comparison to 60–80 km around it and the global average of about 50 km.[11]
The composition of the basin, as estimated from the
Origin
Simulations of near vertical impacts show that the bolide ought to have excavated 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 (compare to the 10 km diameter Chicxulub impactor) 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.[13]
See also
References
- ^
- S2CID 53334293.
- ^ Lyons, Kate. "Chang'e 4 landing: China probe makes historic touchdown on far side of the moon". The Guardian. Retrieved 3 January 2019.
- ^ China's Journey to the Lunar Far Side: A Missed Opportunity? Paul D. Spudis, Air & Space Smithsonian. 14 June 2017.
- S2CID 134219155.
- ^ Griffin, Andrew (10 June 2019). "Huge, unexplained 'mass' spotted under the Moon". The Independent. Archived from the original on 2022-05-24. Retrieved 11 June 2019.
- ^ W. M. Kaula; G. Schubert; R. E. Lingenfelter; W. L. Sjogren; et al. (1974). "Apollo laser altimetry and inferences as to lunar structure". Proc. Lunar Planet. Sci. Conf. 5: 3049–3058.
- Bibcode:1978USGS...IM.1047S.
- ^ Taylor, G. Jeffrey (July 1998). "The Biggest Hole in the Solar System" (PDF). University of Hawaii. Retrieved February 5, 2023.
- ^ [Flashback Friday: "The Moon - So Far" in 1958]. Google Lunar X Price. Astiles, August 27, 2010.
- doi:10.1016/j.icarus.2012.05.032. Archived from the original(PDF) on December 21, 2014.
- .
- S2CID 28619676.
Further reading
- G. Jeffrey Taylor (1998). "The biggest hole in the Solar System". Planetary Science Research Discoveries.