In the annals of American UFO history, few incidents have inspired as much fascination—and speculation—as the one in Roswell, New Mexico.

It began in the summer of 1947, at the dawn of the Cold War, when the U.S. Army Air Forces sent out a shocker of a press release, announcing they’d recovered a “flying disc” from a ranch near Roswell. More than 70 years later, the incident remains a defining aspect of the area’s identity: The town boasts a UFO museum and research center, a flying saucer-inspired McDonald’s, alien-themed streetlights, even an extraterrestrial “family” stranded in a broken-down UFO on the side of State Route 285, looking for a jump-start.

But behind all the UFO mania lies an uneasy truth. The events that transpired that summer are anything but clear-cut, with admitted coverups and conflicting explanations: It was a saucer! It was a spy craft! It was the Soviets!

And new ones are still emerging.

Sometime between mid-June and early July 1947, rancher W.W. “Mac” Brazel found the wreckage on his sizable property in Lincoln County, New Mexico, approximately 75 miles north of Roswell. Several “flying disc” and “flying saucer” stories had already appeared in the national press that summer, leading Brazel to believe the wreckage—which included rubber strips, tinfoil, and thick paper—might be something of that ilk. He brought some of the material to Sheriff George Wilcox of Roswell, who in turn brought it to the attention of Colonel William Blanchard, the commanding officer of the Roswell Army Air Field (RAAF).

The next day, the RAAF released a statement, writing that, “The many rumors regarding the flying disc became a reality yesterday when the intelligence office of the 509th Bomb Group of the Eighth Air Force, Roswell Army Air Field, was fortunate enough to gain possession of a disc through the cooperation of one of the local ranchers and the sheriff's office of Chaves County.”

According to that statement, Major Jesse Marcel, an intelligence officer, oversaw the RAAF’s investigation of the crash site and the recovered materials.

The following day, the Roswell Daily Record ran a story about the crash and the RAAF’s astonishing claim. But U.S. Army officials quickly reversed themselves on the “flying saucer” claim, stating that the found debris was actually from a weather balloon, releasing photographs of Major Marcel posing with pieces of the supposed weather balloon debris as proof.

For decades, many UFO researchers were skeptical of the government’s changed account, and in 1994, the U.S. Air Force released a report in which they conceded that the “weather balloon” story had been bogus. According to the 1994 explanation, the wreckage came from a spy device created for an until-then classified project called Project Mogul. The device—a connected string of high-altitude balloons equipped with microphones—was designed to float furtively over the USSR, detecting sound waves at a stealth distance. These balloons would ostensibly monitor the Soviet government’s attempts at testing their own atomic bomb. Because Project Mogul was a covert operation, the new report claimed, a false explanation of the crash was necessary to prevent giving away details of their spy work.

Other elements of the Roswell story—namely that some eyewitnesses claimed that there were alien bodies taken from the site—were explained as fallen parachute-test dummies in a more extensive follow-up report in 1997.

Roger Launius, a historian and retired curator for the Division of Space History at the Smithsonian National Air and Space Museum, says those two reports close most of the remaining questions about Roswell.

“This story has been resolved,” Launius says. “Has absolutely every question been answered? I can’t say that. But I’m not sure that there are significant holes.”

“You do not divulge state secrets in the context of national security… My surmise is they probably saw [the initial flying saucer explanation] as a useful cover story.”

Donald Schmitt, a UFO researcher who has spent nearly three decades investigating the Roswell incident and is the co-founder of the International UFO Museum and Research Center in Roswell, says that explanation makes little sense. The “flying saucer” story, he contends, was so ostentatious that it was bound to draw attention to the area, with its sensitive military operations at the time. Doing so would seem highly counter to the interests of the War Department.

“Two hours west of Roswell the first atomic bomb was detonated. You had ongoing atomic research at Los Alamos. You had all this testing of captured German V-2 rockets at White Sands. And at Roswell, you had the first atomic bomb squadron headquartered,” Schmitt says. “The thought that they would have intentionally set up any type of publicity as a distraction? If anything, they needed less attention.”

Another questionable theory—advanced by the book Area 51: An Uncensored History of America’s Top Secret Military Base—states that the crashed flying vehicle was neither extraterrestrial nor the work of U.S. spies. Rather, it was an unconventional plan to induce widespread American panic, implemented by Soviet strongman Joseph Stalin.

An unnamed source who worked as an engineer at Area 51 for the defense contractor EG&G told the book’s author Annie Jacobsen, a veteran national security journalist and Pulitzer Prize nominee, that the program had been designed by Nazi concentration camp doctor Josef Mengele. According to the source, adolescent children were deformed by the Soviets to resemble aliens and then deployed in an aircraft to fly over New Mexico. According to this book, Stalin’s “plan was for the children to climb out and be mistaken for visitors from Mars. Panic would ensue… [and] America’s early-warning radar system would be overwhelmed with sightings of other ‘UFOs.’”

That theory could go some way in explaining the wreckage described by Jesse Marcel, Jr., the son of the intelligence officer named in the initial press report. According to Marcel, Jr.’s book, The Roswell Legacy, his father brought some of the UFO wreckage home, allowing his son to handle the debated debris before he took it to his base.

Marcel Jr. wrote that the material was metallic and “I could see what looked like writing. At first, I thought of Egyptian hieroglyphics, but there were no animal outlines or figures. They weren’t mathematical figures either; they were more like geometric symbols—squares, circles, triangles, pyramids, and the like.”

Marcel Jr. was 11 years old at the time, and the Cold War only just beginning. Could the young boy have been reading the Cyrillic alphabet for the first time, allowing his imagination to do the rest?

On this, Schmitt and Launius agree: It’s not likely.

“There’s no evidence in any Soviet archives that there were such experiments as this,” says Launius. “And if the intent was to generate panic, it failed utterly miserably.”