Schrödinger’s Grand Canyons of the Moon

Erwin Schrödinger is best known to the modern layperson for his eponymous, feline thought experiment.

Schrödinger’s cat was designed during a conversation he had with Albert Einstein, about potential paradoxes that arise with certain interpretations of quantum mechanics. Inside a box is a kitty, a vial of poison, a radioactive source, a hammer, and a Geiger counter. If the counter detects a single atom decaying from the source, it’s set up to unleash the hammer upon the vial, which would kill the cat. Radioactive decay is a random event, so, at any given time, the cat could still be alive or dead. Because this experiment happens in a box, the viewer does not know. Based on the Copenhagen interpretation, the cat is simultaneously alive and dead in the box, thanks to the phenomenon of quantum superposition. Even if the cat ends up dead, Schrödinger’s cat has lived many more than nine lives as a mainstay in quantum physics.

Though this touchstone is certainly Schrödinger’s most famous contribution, the bloke was a veritable powerhouse in physics. How many scientists have multiple foundational precepts named after them? He won the Nobel Prize in physics in 1933 for developing the Schrödinger equation that calculates the wave function. He forged the idea and term of “quantum entanglement.” He was among the first to consider the many-worlds interpretation, which is now relatively mainstream. He “dabbled” in just about any field you could imagine in the early 1900s, including statistical mechanics, dielectrics, thermodynamics, color theory, relativity, and cosmology.

So, it’s not surprising that this dude has a lunar crater named in his honor. Behold Schrödinger and Schrödinger crater:

Situated on the far side of the Moon and near its South Pole, Schrödinger is a fantastic example of a peak-ring basin. The outer rim starkly oversees a gorgeous central plateau. The crater is enormous, featuring a 193-mile diameter.

The basin was formed by the impact of a 15.5-mile-wide (25-kilometer) asteroid, meteor, or comet about 3.8 billion years ago. That’s likely bigger than the asteroid that wiped out the dinosaurs.

The geometries and contrasts of the Moon’s pockmarked surface are fascinating. Our satellite looks simultaneously alien and familiar, almost like a cosmological version of Schrödinger’s cat. She is what we could have looked like with no atmosphere, pummeled by the slings and arrows of the solar system.

If we zoom out a bit from Schrödinger’s basin, we’ll notice something a bit odd:

Projecting like scars from the circular basin are two seemingly straight lines!

These lines are known as Vallis Schrödinger (left) and Vallis Planck (right), named for another Nobel Prize winner, Max Planck. Latin for “valley,” these valles are incredible surface features.

The valleys are huge. Grand Canyon-esque, quite literally. The always enthralling jewel of Earth is about a mile deep, 277 miles long, and reaches up to 18 miles wide. The odd lines on the Moon aren’t quite as long – just under 200 miles – but they are deeper, over two miles!

How on Moon did these gargantuan straight lines form?

The valleys are examples of ejecta rays, phenomena that sometimes transpire after an impact. When the body slammed into the moon, it sent rocks into the air, away from the site in a straight line. They fell to the surface with such force that they carved canyons!

The Colorado River has worked its erosional magic on the Grand Canyon for 5 million years, slowly sculpting one of the greatest sights a human can behold. It’s a place where the eternity of rock and the influence of time coalesce.

How long did it take Vallis Schrödinger and Vallis Planck to form?

Armed with the latest visual evidence from the basin, researchers produced a simulation of the impact to detail how the event might have transpired. They were shocked when the computers believed these Grand Canyons of the Moon were created in under 10 minutes!

The evidence also points to another intriguing inference.

Though the crater is largely circular, the impactor did not land in the center.

Based on the geometry of the valleys, the space rock hit the basin toward the southern portion. This layout suggests that the invading object did not hit the Moon straight-on but from an angle that suggests it zoomed by the South Pole. When it hit, the ejecta moved away from the pole, forming the valleys.

This information actually provides some tangible benefits to our upcoming lunar exploration program. Artemis will land astronauts near the South Pole, partially to probe the geological makeup of this point on the satellite. If spray from the Schrödinger basin had headed south instead of north, it would have covered some of the ground they hope to study, complicating the process. Instead, knowing the trajectory likely limits the “contamination” to mostly points north.

In the far future, will humans have the opportunity to walk rim-to-rim at Vallis Schrödinger? If they do, they will experience the work not of millions of years of erosion but 10 minutes of explosive sculpting!