Every few months, the document crops up on some corner of the Internet. The NSA has a document on its site that seems to confirm that, in 1969, an extraterrestrial transmission came in. The document, labelled "Key to The Extraterrestrial Messages," is a follow-on to two 1966 documents called "Extraterrestrial Intelligence" and "Communications with Extraterrestrial Intelligence."

"Communications" is more an assessment of how we might someday hear from aliens, including the idea of a "neutrino beam" rather than radio signals. It also demonstrates how we might try to reach out to any potential alien intelligence. Author Lambros D. Callimahos, a former U.S. Army codebreaker, suggests that advanced mathematical equations could provide a galactic "Rosetta stone" for future contact.

But the "Key to the Extraterrestrial Messages" assumes that, in three short years, we had already found that contact. It makes reference to the original NSA doc, which states, "Recently a series of radio messages was heard coming from outer space. The transmission was not continuous but was cut by pauses into pieces which could be taken as units, for they were repeated over and over again." The "Key to the Extraterrestrial Messages" was the solution to those problems.

Except there's also the fine print in "Extraterrestrial Intelligence": "In the most recent issue of the NSA Technical Journal- Vol. XI, No. 1- Mr. Lambros D. Callimahos discussed certain aspects of extraterrestrial intelligence and included several messages to test the reader's ingenuity." In other words, like much of the publications from the NSA Technical Journal, this was a cryptography exercise—not a smoking gun.

To be sure, the Journal dipped its toes in weirdness, like "The Voynich Manuscript Revisited," which attempts to decipher a famously hard to crack book with bizarre diagrams.

But there's one thing "Key" fails to do throughout its text: establish that the original article was simply a lighthearted exercise in decoding a seemingly "alien" code. And so it ended up with a sort of credulous whisper status among some online communities like Before It's News, a site whose contents veer into the conspiratorial.

But UFO site OpenMinds.tv had the right take in 2011: Yes, it was just a fake exercise and not real SETI results. But, article author and Mutual UFO Network investigator Alejandro Rojas says, Callimahos put forth the exercises under the belief that it provided better preparation if such an event came to pass.

In "UFO Hypothesis and Survival Questions," he suggests that we should be prepared for the UFO phenomenon, whether or not it's actual aliens. Part of his reasoning? Our Cold War enemies could use UFO like objects to intentionally fool Americans before an attack. After all, as Callimahos points out, the U.S. and Canada both tested flying saucer-shaped vehicles.

The NSA, in general, keeps a fairly hefty volume of documents about UFOs thanks to repeated FOIA requests into the matter. It even has a list of topics for which no documents come up, including SETI and Extraterrestrial Signals. In addition, even the barest hint of a potential signal is enough to rile up enthusiasts. In fact, at a panel talk in 2013 that I attended, lead SETI Institute scientist Seth Shostak relayed the time his organization thought they had a tantalizing signal ... and within a half hour, they also had a phone call from the New York Times. (The signal was a false positive.)

So in the end: yes, there's a document in the NSA's website about decoding alien signals. But the signals were just a practice run for when the real thing hits. And even then, we might be ill-prepared.

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