Researchers are exploring a theory that the planet “devoured” its moon

NEED TO KNOW

• A new study explores whether Venus may have once had a moon that eventually crashed into the planet
• Researchers found that Venus’ slow rotation could have caused a moon to gradually spiral toward the planet
• Scientists have not confirmed that Venus ever had a moon, but the study explores what could have happened if it did

Venus may be moonless today, but that doesn’t necessarily mean it always was.

A new study suggests that if Venus once had a moon, the planet’s unusually slow rotation could have eventually pulled the celestial body back toward its surface, potentially ending with a massive collision. After the collision, the fragments of the moon may have been “devoured,” Wired reported.

The research, titled Tidal Demise: The Evolution and Fate of a Hypothetical Venus Moon, explores what might happen if a moon orbited Venus under a range of different conditions. University of California, Riverside astrophysicist and Planetary Astrophysics professor Stephen Kane was one of the paper’s lead authors.

The study doesn’t confirm that Venus ever had a moon. Instead, the researchers wanted to see what could have happened if the planet once had one.

The researchers’ models showed that the hypothetical moon’s fate depended largely on how quickly Venus was spinning and how big the moon was. In some scenarios, a moon could stay in orbit for billions of years. In others, it would slowly spiral toward Venus and eventually be destroyed.

Kane said the results changed how he viewed the possible history of Venus.

“When I made this discovery, I was shocked,” Kane said in a press release. “I thought surely the broad range of scenarios I was exploring would lead to a variety of results. But it all went pretty much in the same direction.”

To test the idea, the researchers built computer models of a Venus-moon system. They first used Earth’s moon to test their model before changing Venus’ rotation speed and the size of the hypothetical moon. The simulations included moons ranging from half the mass of Earth’s moon to 10 times its mass.

In many of the scenarios, the hypothetical moon eventually crashed into Venus. Larger moons reached the planet more quickly in the simulations.

The mechanism that would make the moon crash possible has to do with how quickly Venus rotates.

Earth spins relatively quickly, completing one rotation in about 24 hours, Kane explained in the press release. That rotation helps push our moon gradually farther away from the planet. The moon currently moves away from Earth at roughly four centimeters per year, according to Kane.

Venus is a very different story. The planet takes 243 Earth days to rotate once. According to Kane, that slow rotation could cause a moon orbiting Venus to gradually move inward instead of drifting away.

“My study shows Venus didn’t require a catastrophe to arrive at what we can see today,” Kane said. “It turns out the gravity of the planet itself combined with the rate at which it spins naturally caused the moon to collapse on top of it.”

If a moon did crash into Venus, the collision would have transferred enormous amounts of energy and angular momentum to the planet, potentially changing its rotation, geology and climate, researchers said.

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The researchers also say the findings could be relevant to scientists studying planets around other stars, particularly slowly rotating worlds that could potentially form moons.

The question of whether a moon is necessary for a planet to support life is still being studied.

“My feeling is there are benefits to having a moon, but it isn’t required for habitability,” Kane said in the press release. “The moon has definitely changed the way Earth has evolved through time, but we don’t fully know how important that role is.”

PEOPLE has reached out to Stephen Kane for additional comment.

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