Feb. 24, 2005 -- For those who believe that Earth has been visited by extraterrestrial spacecraft, a remote New Mexico ranch is hallowed ground.
The believers say that in the summer of 1947, 75 miles outside Roswell, the holy grail of UFO-ology was found -- concrete evidence proving the existence of alien life.
The story begins when rancher Mack Brazel found some strange debris on his land. Maj. Jesse Marcel, the intelligence officer at the Army air base in Roswell, went to investigate and was convinced that the debris was "not of this Earth."
Marcel put the strange wreckage in his car and drove it back to the base. But on the way, he stopped home and showed his wife and 11-year-old son, Jesse Jr., what he had found.
Marcel died in 1986, but his son told ABC News in a recent interview that the memory of that day is still fresh in his mind. He said there were I-beams in the debris, "structural members with pinkish violet writing along the inside surface," he said. "It was more like geometric symbols. It was very impressive."
The debris arrived at the base early on July 8. By noon, the base commander, Col. William Blanchard, authorized a press release proclaiming that what Marcel found was the remains of a flying saucer.
"There was a tremendous public excitement," says UFO researcher Karl Pflock. "It was national news. It was a big deal. And people were very excited and very, you know, frightened, and everything else."
Truth or Dare
But the excitement was short-lived. The next day, Brig. Gen. Roger Ramey, commanding officer of the 8th Air Force, held a news conference in Ft. Worth, Texas, and said a flying saucer was not recovered. The debris that was found was nothing more than "a harmless, high-altitude weather balloon."
The public accepted the explanation. World War II had just passed, and "I think most people, basically, trusted the government," said Pflock. "There was very little skepticism about it, and it just kind of went away."
For 30 years, almost no one paid any attention to the events at Roswell. Marcel's story might still be forgotten were it not for a UFO-ologist named Stanton Friedman.
In the late 1970s, Friedman was at a television station in Baton Rouge, La., when the station manager suggested he get in touch with Marcel.
"Out of the blue, he says, 'you know, the guy you ought to talk to is Jesse Marcel. He handled the wreckage of one of those saucers you're interested in when he was in the military,' " Friedman told ABC News.
Friedman found Marcel in Houma, La. He had retired and was a TV repairman.
In one of the rare interviews filmed with him, Marcel described how the debris was spread over a large area and the unusual characteristics of it.
"We found a piece of metal about a foot and a half to two feet wide and you couldn't even bend it, you couldn't dent it, even with a sledgehammer it would bounce off of it. So it was not anything from this Earth. That I'm quite sure of," Marcel said.
Marcel's son told ABC News: "My dad finally came to the conclusion that this is a story that should not be contained or buried. He felt that it was time that people know the truth about this."
But the truth remains elusive. The wreckage hadn't been seen since 1947 so there has been no way to prove Marcel's claims. But Friedman and others pressed on with promoting Roswell.
The first Roswell book appeared in 1980. "The Roswell Incident" supported the idea that what crashed was a flying saucer, and the government was hiding it somewhere.
More publicity followed. Television shows like "In Search Of" and "Unsolved Mysteries" also told the story of Roswell's alien history. Friedman and his colleagues appeared on the talk show circuit, asserting there was a government cover-up -- "not only about this case, but lots of other UFO cases."
New witnesses came out of the woodwork with tales of secret government activity and alien bodies found in the wreckage.
In 1995, FOX television broadcast what it promoted as recently discovered film of an alien autopsy performed at Roswell. It was seen by more than 20 million viewers.
And then came the TV series "The X-Files," which wove Marcel's story into prime-time television.
Roswell became "an incredible story ... a best seller" said historian Robert Goldberg, author of "Enemies Within: The Culture of Conspiracy in Modern America."
The people promoting Roswell now had a financial interest in keeping the story alive, he said. "There is money to be made, but your book is only going to sell if your charges are more grandiose, more exaggerated, more powerful. So you have this ladder of escalation of sensationalism," said Goldberg.
Like Nothing Else on Earth
Decades after something fell from the sky outside Roswell, the New Mexico town is now a tourist destination, complete with UFO museums, gift shops and guided tours.
It doesn't matter that there isn't a shred of evidence to support the claim that a flying saucer crashed there. It doesn't matter that there are no credible witnesses to alien bodies. On the 50th anniversary of the alleged crash, 65 percent of Americans told a TIME magazine-CNN poll that they believed the story.
As for the strange debris itself, the Air Force has offered explanations saying "what was recovered near Roswell, New Mexico, in July 1947 was debris from a formerly top secret Army Air Force's research project, code name Mogul."
Project Mogul was so secret that it had the same security classification as the atomic bomb project. It consisted of high-altitude balloons and instrumentation arrays designed to detect Soviet nuclear tests. They were tremendous -- as long as 650 feet. And in 1947, nothing else on Earth looked like them.
Pflock has no doubt UFOs exist, but he buys the Mogul explanation. "When I began to look at the reports from that project and see the kinds of materials that were used and then I took a look at the descriptions of the genuine debris that was found. It all matched," he told ABC News.
"The irony of all of this is that the great Roswell mystery, the great Roswell cover-up arose from a real cover-up, but the intent was not to protect knowledge of a crashed flying saucer but to protect a very earthly project."
Roswell has become an article of faith, Pflock said. "I don't think the hardcore believers will ever give up on Roswell."