A massive asteroid with an iron core and rocky mantle struck the Moon at a shallow angle, creating its largest impact basin.
The Origin of the Moon's Largest Basin
A new study reveals that the Moon's South Pole-Aitken (SPA) basin, the largest and oldest impact feature on the lunar surface, was likely created by a differentiated asteroid—one with a dense iron core and a rocky mantle.
Key findings from the research:
- The basin's unique tapered-ellipse shape is best explained by a 160-mile-wide impactor.
- The asteroid struck at a shallow 30-degree angle at a speed of about 8 miles per second.
A Two-Stage Impact
High-resolution 3D simulations show that this particular trajectory caused the impactor's upper layers to shear off while its dense iron core continued to plunge into the Moon. This two-stage process is what carved the basin's distinctive, elongated shape.
"The impact would have ejected material from the Moon's mantle toward the south pole."
Implications for NASA's Artemis Missions
This finding has direct implications for NASA's upcoming Artemis missions, which plan to land near the Moon's south pole. Samples collected from that region could contain debris from the Moon's deep interior, ejected by this ancient impact.
By analyzing those samples, scientists hope to:
- Determine the precise age of the SPA basin.
- Reveal the composition of the Moon's mantle—material normally buried far below the surface.
This research provides a critical link between the Moon's visible surface features and its hidden, deep geological history.