Look: Chinese rover spots a "Moon Cube," and opens a new lunar mystery

An image has tantalized the internet: an enigmatic cube-shaped object on the far side of the Moon.

But “strange cube” conjures up a few images: an alien Starbucks. A secret Russian Moonbase. Gene Ray’s Time Cube instantiated. A time-traveling porta-pot from a 1932 skyscraper construction site.

In November, the Chinese lunar rover Yutu-2 spotted the cube in the distance from the far side of the Moon. The rover has since been making its way toward the mysterious object, investigating its origins. And unfortunately for the overly imaginative, it’s unlikely to be aliens or something metaphysical.

As Paul Byrne, a professor in Earth and Planetary Sciences at Washington University in St. Louis, sees it, he knows exactly what it is: the more mundane confluence of rocks, light, and shadow.

“The object in that image is almost definitely, categorically, absolutely a boulder,” Byrne tells Inverse. “There's pretty much nothing else I can think it might be — my potential lack of imagination notwithstanding.”

It may not fire the imagination like an alien origin, but the boulder will help scientists better understand the history and composition of the Moon, and provide a picture of what could form other strange outcroppings on the surface of our nearest neighbor. Byrne says that better understanding the Moon could help astronauts better learn how to better “live off the land” and utilize lunar resources as part of lunar outposts.

The Moon cubes cometh — but we’ll be building them ourselves.

What is the mysterious Moon Cube?

China’s robotic Yutu-2 lunar rover spotted a remarkably square-looking gray object on the horizon on its 36th lunar day, according to reporting by Space.com, which translated an entry in a rover mission diary from the Chinese language website Our Space.

Taken from around 260 feet away, the “mystery hut,” or “mystery house,” as Our Space put it, appears like a tiny cube the same color as the lunar regolith, but with a black rectangle in the center. Almost like a door … or a Kubrick-esque monolith.

Zoom on the picture, and it becomes significantly blurry, but the overall impression of something with disconcertingly square proportions remains.

But while human craftsmanship tends to result in square angles and straight lines, not all square angles and straight lines result from human, or alien, handiwork. Byrne guides Inverse through a few scenarios:

1. It could be an illusion: “Why might it appear square or cubic? First, the image looks to have a pretty low resolution of features at or beyond the horizon, so it might not actually be square,” Byrne says.
2. It might have just been forged that way by natural causes: Even if it is square, “lots of boulders are blocky, squarish, or cubic/cuboidal because rocks commonly develop fracture sets that result in blocks,” Byrne says, and there are lots of boulders on the Moon.
3. The most likely outcome is that as the rover gets closer to the object, it will become apparent that it’s a boulder or multiple boulders that only appear square due to light, shadow, and distance. And really, that would make it one of the more minor instances of extraplanetary pareidolia, that is, seeing patterns that don’t exist.

In 1976, the Viking 1 orbiter took a photo of a rock in the Cydonia region of Mars that looked an awful lot like a face. Humans are neurologically primed to see faces, reading faces being pretty crucial for human survival, so it’s not surprising some people would see a face somewhere on Mars. It was still just rocks, light, and shadow.

“The ‘Face on Mars’ is a perfect example of pareidolia,” Byrne says, but there are other examples, including what some people say looks like Han Solo encased in carbonite on Mercury or a giant tick on Venus.

Where is the Moon cube?

Whatever the Moon cube might be, it’s currently about a football field away from the Yutu-2 rover, which is the first rover to explore the far side of the Moon. Both the rover and the mysterious object sit in the Von Kármán crater, a 110-mile diameter impact crater in the southern polar region of the Moon.

Meteor or comet impacts are a good way to generate and disperse boulders on the Moon without weather or water, and the Moon cube and Yutu-2 sit in a double crater — the Von Kármán crater is one of many in much, much larger South Pole-Aitken Basin, which measures nearly 1,600 miles across.

What is the Chinese Yutu-2 Rover?

CNSA launched the Yutu-2 rover in December 2018 as part of China’s Chang’e 4 lunar mission. The Chang’e 4 lander made the first soft landing on the Moon’s dark side on January 3, 2019, and deployed the rover.

Yutu-2 has since traversed more than 2,700 feet of the lunar surface, using its ground-penetrating radar and spectrograph instruments to study the surface composition and deeper structure of the Moon.

Powered by solar panels, Yutu-2 powers down during the two-week-long lunar night when the dark side of the Moon faces away from the Sun. But the Chinese rover has nevertheless beat the longevity record of the Soviet Lunokhod 1 rover. The Soviet machine roved the Moon for 321 Earth days in 1971, but Yutu-2 has been going strong for more than 1,068 Earth days.

What does the Moon Cube tell us about lunar geology?

Lunar boulders are interesting, Byrne says, because they tell scientists about the energies involved in the impacts that created them and give scientists access to material from deeper inside the Moon. “But for the time being, I have no reason to think that this particular boulder is any more special than any other of the billions and billions on the Moon,” he adds.

More exciting is what the Yutu-2 rover may learn on its way to examining this mystery object.

“We still have a lot to learn about the Moon scientifically: its interior structure, the level of geological activity there today, and the composition of a variety of different parts of the Moon,” Byrne says. “Anything we learn about a place we’ve only visited with humans a handful of times will be useful!”

How soon will we learn what the mysterious Moon Cube really is?

Yutu-2 is an impressive instrument, but it’s not built for speed. While Chinese scientists plan to investigate the Moon Cube/ “Mystery Hut,” it will likely take two to three months — with intervening periods of inactivity during the lunar night — for the rover to get to the site of the mystery.