Are Alien Probes Hiding in Plain Sight in Our Solar System?

If there are alien probes hiding in our solar system, they probably don’t look like anything we saw in Independence Day. They might look like rocks.

That’s the argument from Alex Ellery, a mechanical and aerospace engineering professor at Carleton University, whose new paper suggests extraterrestrial probes could already be here. These self-replicating “von Neumann” machines, named after the 20th-century mathematician who first theorized them, could have been sneakily spreading through the galaxy for millions of years. 

His study, published on arXiv, claims they might have settled in places we rarely look, like inside lunar craters, drifting in the asteroid belt, or camouflaged among objects like Comet 3I/ATLAS, the oddly shaped interstellar visitor that has fueled online conspiracy theories about alien tech.

Are Alien Probes Watching Us From Space?

Ellery believes our search for life has been too narrow. Instead of listening for radio signals from distant stars, he says we should be examining the surfaces of nearby moons and asteroids for clues. “The Solar System is huge and mostly unexplored,” he told Universe Today. “There could be probes everywhere: in craters on the Moon, or lurkers in the Asteroid Belt and Kuiper Belt.”

His paper outlines how these theoretical probes would behave if they existed. They would mine asteroids for metals, build surveyors, replicate themselves, and eventually construct small bases to continue the process. Ellery suggests such activity might leave pieces of evidence behind, like unusual isotope ratios of uranium or thorium in lunar rocks. “If we have been visited,” he wrote, “a gift in return for mining of our resources may be hidden among those asteroidal metals.”

The theory isn’t about little green men; it’s about logic and efficiency. Machines don’t need air, food, or sleep. They could travel farther than any biological lifeform, copy themselves endlessly, and keep working long after their creators were gone. For an advanced civilization trying to preserve knowledge or scout the galaxy, that would be the simplest way to stay alive.

Most scientists see Ellery’s idea as a long shot, but even a long shot can make you think twice. If he’s right, the first evidence of alien intelligence might not come from a telescope or a radio signal. It could simply be a rock sitting on the Moon.