There’s no denying the allure of alien artifacts. Science fiction is awash in the material remnants of extraterrestrial civilizations, which surface in everything from the classic books of Arthur C. Clarke to game franchises like Mass Effect and Outer Wilds.
The discovery of the first interstellar objects in the solar system within the past decade has sparked speculation that they could be alien artifacts or spaceships, though the scientific consensus remains that all three of these visitors have natural explanations.
That said, scientists have been anticipating the possibility of encountering alien artifacts since the dawn of the space age.
“In the history of technosignatures, the possibility that there could be artifacts in the solar system has been around for a long time,” says Adam Frank, a professor of astrophysics at the University of Rochester.
“We’ve been thinking about this for decades. We’ve been waiting for this to happen,” he continues. “But being responsible scientists means holding to the highest standards of evidence and also not crying wolf.”
That raises some tantalizing questions: What is the best way to search for alien artifacts? And what should we do if we actually identify one? Given that these technosignatures could run the gamut from tiny alloy flecks to hulking spaceships—or perhaps, some material that is unimaginable to Earthlings—it is difficult to know what to expect.
To meet this challenge, researchers are currently working on an array of techniques to search for signs of alien remnants across our solar system—including in orbit around Earth.
For example, Beatriz Villarroel, an assistant professor of astronomy at the Nordic Institute for Theoretical Physics, has focused on a largely untapped observational resource: historical images of the sky taken before the human space age.
By studying archival photographic observations captured by telescopes prior to the launch of Sputnik in 1957, Villarroel has produced a portrait of the sky before it was speckled with our satellites. As the lead of the Vanishing & Appearing Sources during a Century of Observations project (VASCO), she had initially been looking for any evidence that stars, or other natural objects, might vanish on these archival plates.
Instead Villarroel found inexplicable “transients” that look like artificial satellites in orbit around Earth, long before the launch of Sputnik, which she and her colleagues reported in 2021.
“That’s when I realized this is actually a fantastic archive, not for searching for vanishing stars, but for looking for artifacts,” she says.
Last year, Villarroel and her colleagues published three more studies about the search for near-Earth alien artifacts in The Publications of the Astronomy Society of the Pacific, Monthly Notices of the Royal Astronomical Society, and Scientific Reports that have generated spirited debate among scientists. Researchers have suggested a range of alternate explanations for the transients, which could involve instrumental errors, meteors, or debris from nuclear tests.
The mystery could potentially be resolved with a dedicated mission to search for artifacts in geosynchronous orbit, an environment about 22,000 miles above Earth. However, Villarroel doubts that such a mission would be green-lit by any federal space agency in the near term, due to the controversial nature of the topic.
“There’s so much taboo that nobody’s ever going to take such results seriously until you bring down such a probe,” she adds.
Frank says he agrees that the stigmatization of the search for otherworldly artifacts—and the search for alien life, more broadly—is counterproductive. But he sees the pushback over research into alien artifacts as a healthy and natural part of scientific inquiry.
