When astronauts from the Artemis IV space program return to the Moon, the site of their historic landing will be the Moon’s far southern region — the South Pole–Aitken Basin. It is the largest and oldest impact crater on the far side of the Moon. Two new studies have revealed unexpected details about its origin, helping scientists understand what the first explorers may encounter in this uncharted territory.
Of the nine potential Artemis landing sites, several lie directly within this giant basin, including Nobile Rim 1, Nobile Rim 2, and Haworth, while others are located along its edges or nearby. The main reasons these sites were selected are two critically important resources: sunlight and water ice.
The region near the lunar south pole provides astronauts with long periods of sunlight and access to water ice, which is essential for crew survival. However, the scientific value of this area is just as significant. As William Bottke, Director of the Center for Lunar Origin and Evolution (CLOE), notes, the colossal impact of an ancient asteroid literally excavated material from the Moon’s deepest layers, including its mantle. This offers a unique opportunity to study the Moon’s earliest history.
A Protoplanet Impact
To reconstruct the catastrophe that created this basin, researchers used advanced computer simulations. Scientists led by Shigeru Wakita of Purdue University found that the cosmic body approached from the north and struck the surface at a sharp angle — which is why the crater has an elongated shape rather than a perfectly circular one.
The analysis showed that the impacting body was most likely not an ordinary asteroid. It was a protoplanet — a small planet in the process of formation — with its own core and an outer rocky shell. As a result of the extremely powerful collision, rock at the impact site melted, and enormous amounts of material from both the Moon’s crust and mantle were ejected into space.
Treasures from the Moon’s Depths
The researchers also wanted to determine exactly where this ejecta was deposited. A team from the University of Arizona, led by Gabriel Gowan, analyzed high-precision gravitational data. For a long time, scientists believed that the deepest mantle ejecta lay too far from the planned landing sites. However, the new modeling showed the opposite: the basin contains a significant amount of mantle rock mixed with rocky debris on the surface.
In addition, later and smaller impacts helped bring some of these deep materials even closer to the south polar region. This is excellent news for the Artemis mission, because astronauts may be able to collect samples of the Moon’s most ancient interior directly from the surface.
Unraveling the Mysteries of the Far Side
This region has long intrigued scientists. Back in 2019, an anomalously dense mass of metallic rock was discovered beneath the South Pole–Aitken Basin, covering an area five times larger than the Big Island of Hawaii. Research into this mysterious crater is already well underway: in the summer of 2024, China’s Chang’e-6 probe landed in the Apollo crater and successfully delivered soil samples back to Earth. Now it is the turn of the Artemis astronauts, who will be able to study these cosmic treasures directly on site.
Earlier, we explained how the Moon formed and why it is so unlike Earth.
According to earthsky.org
