A canyon is a deep, narrow valley with steep sides. Here on Earth, canyons are typically formed by long-term erosion from rivers or tectonic activity. But on the moon, where there’s no atmosphere, there’s another way to create a canyon: through an impact.
Two such lunar canyons, Vallis Schrödinger and Vallis Planck, stretch over 270 km (168 miles) each, with depths of 2.7 km (1.7 miles) and 3.5 km (2.2 miles), respectively — comparable to Earth’s Grand Canyon. Now, researchers have pieced together the violent cosmic event that formed them.
The Schrödinger crater, located near the southern pole, is about 312 km (193 mile) wide and 4.5 kilometers (2.7 mile) deep. It was formed when an unknown object hit the Moon some four billion years ago. The impact formed a peak-ring basin — an inner ring of mountains produced by the collapse of an uplifted central peak. But that’s not all it formed.
Blink and a crater is formed
The immense energy of the impact launched massive streams of rock and debris outward at high velocities. These ejected materials followed ballistic trajectories before slamming back into the lunar surface, carving deep trenches in their wake. Vallis Schrödinger and Vallis Planck are two such trenches.
David Kring, Danielle Kallenborn, and Gareth Collins, researchers working with the Lunar and Planetary Institute and Imperial College London, wanted to look at the canyons in more detail.
They used multiple photographs of the Moon from different angles to generate complex maps. They examined high-resolution images and elevation data from NASA’s Lunar Reconnaissance Orbiter (LRO). Using tools like the Lunar Orbiter Laser Altimeter (LOLA) they precisely measured the depth, width, and extent of the canyons.
The researchers found 15 secondary craters along the length of Vallis Schrödinger, with diameters between 10 and 16 km. By identifying secondary craters along the canyon paths, they confirmed that these features formed through chains of high-energy impacts. They then used these maps to calculate ballistic trajectory equations and crater scaling laws to estimate the velocities and sizes of the impacting ejecta.
They found that the debris streams hit the surface at speeds between 0.95 and 1.28 km/s, excavating enormous trenches in under ten minutes. The study also showed that the impactor that created Schrödinger struck at a shallow angle, ejecting most of its debris away from the Moon’s south pole.
These canyons could be important for future missions
With NASA’s Artemis program preparing to send astronauts to the Moon’s south pole, understanding the Schrödinger impact basin is crucial. The study suggests that less ejecta from Schrödinger covers the Artemis exploration zone than previously thought. So, the Artemis astronauts will have an easier time accessing older lunar crust and impact melt deposits.
If the Schrödinger impact had ejected debris symmetrically, large portions of the south pole — including the Artemis exploration zone — would be buried under thick layers of ejecta, making it harder to access ancient lunar material. However, the study shows that the impact occurred at a shallow angle, directing most of its ejecta away from the south pole.
As Artemis astronauts set foot near the Schrödinger basin, they will not only explore a landscape sculpted by cataclysmic forces but also uncover clues to the history of our solar system.
Other bodies in the solar system without an atmosphere (like Mars or Mercury) may have similar craters formed by massive impacts.
The study “Grand canyons on the Moon” was published in Nature Communications https://doi.org/10.1038/s41467-024-55675-z.
