4-Billion-Year-Old Cosmic Secret Hides Right Where Artemis Astronauts Will Land On The Moon
The SPA basin, which spans roughly 1,600 miles (2,500 km) in diameter, is
the largest and oldest known impact crater in the solar system. For years, scientists believed the impactor approached from the south. However, the latest research by a team from the University of Arizona suggests that an asteroid struck with a glancing blow from the north. By comparing SPA's elongated, teardrop-like shape to other giant impact sites across the solar system, the researchers determined that the basin actually narrows in the down-range direction of the strike—which, in this case, is the south.
This directional correction could prove to be a game-changer for upcoming Artemis missions, which are targeting the southern rim of the basin. The new theory suggests the Artemis landing zone is the down-range area where the most significant amount of ejecta (material blasted from the Moon's deep interior) should have accumulated. Astronauts will essentially be landing on a massive, naturally deposited geological core sample, offering a unique opportunity to study the Moon’s evolution.
What the new evidence suggests is that the SPA impact created a window through the Moon's crust right at the boundary of a region where the last remnants of the KREEP-rich molten layer were concentrated. Specifically, the ejecta blanket on the basin’s western flank is rich in radioactive thorium, while the eastern flank is not.
Such asymmetry supports the theory that the Moon's crust is much thicker on the far side. As the crust solidified on the far side, the underlying magma (and its concentrated KREEP material) was effectively squeezed out like toothpaste toward the thinner, near side crust. The SPA impact, therefore, punched through a transitional zone, scattering that precious, deep material toward the south polar region where Artemis is set to land.
