And was the wreckage taken back to the mysterious "Area 51" military base in the Nevada desert?
As CNET Executive Editor Molly Wood reported on "The Early Show" Monday, a new book takes a look at Area 51, rekindles debate over both questions - and introduces a Nazi connection to the mix.
Area 51 is about 80 miles northwest of Las Vegas and is, Wood says, "the most talked-about top secret military base in America."
For six decades, it operated in total secrecy; the government denied it even existed.
But it wound up at the center of conspiracy theories involving aliens, flying saucers, and high-level cover-ups.
Newly-declassified documents finally give a glimpse into the mysterious place, and its essential role in the space race and the Cold War.
"Area 51 was set up to push military, science and technology faster and further than any other nation," explains journalist Annie Jacobsen, author of "Area 51: An Uncensored History of America's Top Secret Military Base," who went through thousands of those documents.
The book chronicles what happened on that base in the 1940s, '50s and '60s -- she spent years interviewing those who worked there.
"They're kind of a fraternity of formerly secret spies and scientists and spy pilots and engineers, all of whom know one another," Jacobsen observes.
They spent most of their lives hiding what they did at work every day.
Now, these veterans are finally able to talk about what went on inside the base.
TD Barnes, an Area 51 radar specialist, says, "We went by code names. I was 'Thunder.' ... We were dealing with Navy, Air Force, Tactical Air Command, SAC (Strategic Air Command). ... We had one common goal: We had an urgency of doing our job, because lives and our military depend on what we were doing there."
On a dry lake bed, the CIA and later, the Air Force, developed groundbreaking technologies for espionage and warfare still used by the military today.
"When you look at the drones that fight the War on Terror," Jacobsen says, "you can see the lineage goes directly back to the early spy platforms at Area 51. The U2 (spy plane) was developed there; the A12 Oxcart was developed there."
Area 51 scientists were also involved in the U.S. nuclear weapons program.
"There were over 100 atmospheric atomic bomb tests at Area 51's nearest neighbor," Jacobsen says, "which is called the Nevada Test Site, starting in the 1950s. Many of the men in my book worked on those bomb tests."
But to most of the world, Area 51 is famously known for the alien conspiracy theory involving a supposed UFO crash in Roswell.
Jacobsen cites an anonymous source who gave her a surprising explanation.
"A flying disc really did crash in New Mexico," she says, " ... and then it did wind up at Area 51. ... It did not come from Mars. It came from Russia."
Jacobsen's source claims there were human pilots in that flying disc -- not aliens, but Russians.
"This," she told CBS News, "is information that came to me from the source, who I absolutely believe (and) stand by. I've spoken with him since the book has been published ... and what he said was that the child-sized aviators had been the byproduct of this horrific human experimentation program by Stalin, in collaboration with the doctor from Auschwitz, Dr. Joseph Mengele.
" ... Eventually, my source told me ... 'We chose to do the same thing' -- and that upsets a lot of people -- this idea that the United States government ... could have experimented on humans."
The CIA hasn't commented on the allegations.
But for those who worked on the military base, they can't conceive of it having happened.
"We don't know," says TD Barnes. "We can't -- its just personal opinion; everybody's got their own opinion about certain things."
Jim Freedman who, like Barnes, was an Area 51 field coordinator, remarked to CBS News he "just can't picture it (human experimentation by the U.S.), because I would then be forced to say I don't want to be part of it."
For now, these men are the only link we have to what truly went on inside Area 51. With their stories and declassified documents, we are learning more about what really happened inside the gates.
But most of it will likely always remain a mystery.
And Jacobsen's claims that there was a flying saucer, and that the Russians and the U.S. were doing human experiments, have drawn fire from various quarters.
Barnes, who's president of Roadrunners Internationale, a group of former Area 51 workers. told CBS News he disagrees with Jacobsen going public with her assertions.
"When Annie and her publisher at Little Brown locked onto a sensational twist (invented scoop), they put blinders on to avoid learning the truth,' He said in an e-mail."They embargoed the book where no one, even within Little Brown, had advance knowledge of what was going to print. ... Annie refused to even correct misstatements on her website though presented with the facts."
He goes on to say he introduced Annie to people who refuted her stories -- but she did not listen.