How often have we thought about the existence of life beyond Earth, and feared that if we ever encountered extraterrestrial beings, they might wreak all kinds of havoc on our planet, as shown in the movies.

But the pertinent question still remains, do aliens exist?

Some might think the only people who believe in aliens are "forum-dwelling internet conspiracy theorists," but several NASA astronauts believe extraterrestrials exist and have been in touch with humanity for a long period, reports said.

Data cruncher and blogger Sam Monfort in his blog on Feb. 21 said the number of unidentified flying objects (UFOs) sightings is currently at an all-time high. He wrote that one of the first recorded UFO sightings was in Portland in 1905, where a "buzzing sphere-shaped UFO descended from the clouds." 

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According to Monfort's report, there have been 104,947 reported sightings on record over the past 100-plus years. He used information from the National UFO Reporting Center (NUFORC), which collects and disseminates objective UFO data and keeps careful logs of all UFO sightings worldwide. 

Furthermore, there have been several astronauts such as Edgar Mitchell, Cady Coleman, Edwin Buzz Aldrin and Dr Brian O’Leary who have claimed to have seen UFOs. Aldrin, one of the first people to walk on the Moon, had shared his experience on board the Apollo 11, when he and fellow astronauts saw something flying alongside their spacecraft. Initially, they thought it was the final stage of a detached rocket, until mission control confirmed it was 6000 miles away from them.

Buzz Aldrin

Both Neil Armstrong and Aldrin saw UFOs shortly after their historic landing on the Moon in Apollo 11 on July 21, 1969, according to unconfirmed reports. NASA astronaut Armstrong believed aliens have a base on the Moon and  they apparently warned Armstrong and others to "get off and stay off the Moon."

During a Reddit "Ask Me Anything" session, Aldrin said the "first humans to set foot on Mars should never return to earth."

When one user asked Aldrin if he believed in aliens and asked him about the sightings he saw on board Apollo 11, the astronaut replied: "On Apollo 11 en route to the Moon, I observed a light out the window that appeared to be moving alongside us. There were many explanations of what that could be, other than another spacecraft from another country or another world - it was either the rocket we had separated from, or the 4 panels that moved away when we extracted the lander from the rocket and we were nose to nose with the two spacecraft."

Although Aldrin was reluctant to describe the sighting as an extraterrestrial craft, he believes there are other life forms in space. 

Edgar Dean Mitchell

In 1971, Mitchell became the sixth person to walk on the Moon, and the journey spiritually transformed his life in such a way that he devoted much of his time exploring "esoteric realms of science, psychic phenomena and the existence of extraterrestrial beings."

He was convinced after the journey to the Moon that "aliens have been observing us and have been here for some time." Mitchell once even claimed that "peace-loving" aliens had visited Earth to save humanity from nuclear war, and indicated the Vatican knew about the existence of extraterrestrials.

Mitchell, who had been outspoken about his belief in aliens, told Mirror Online that top-ranking military sources had spotted UFOs during weapons tests. He also said that strange crafts flying over missile bases at the White Sands facility have been spotted by military insiders. The facility is a government-owned rocket engine test site where the world's first ever nuclear bomb was detonated in 1945.

Gordon Cooper

Cooper was one of the seven astronauts who took part in Project Mercury, the first human spaceflight program of the U.S., which ran from 1958 to 1963. Cooper, the last American to fly in space alone, had said he spotted UFOs flying over Germany seven years before he went into space.

In 1963, when he shot into space in a Mercury capsule for a 22-orbit journey around the world, Cooper told the tracking station he could see a glowing, greenish object appearing in front of him and approaching his capsule. The UFO was reportedly "real and solid," because even the tracking radar had picked it up, according to syti.net.

According to a taped interview by author, J.L. Ferrando, Cooper revealed how he felt he was living with a secret,  which was imposed on all specialists in astronautics. "I can now reveal that every day, in the USA, our radar instruments capture objects of form and composition unknown to us. And there are thousands of witness reports and a quantity of documents to prove this, but nobody wants to make them public," he said. He added: "Because authority is afraid that people may think of God knows what kind of horrible invaders. So the password still is: We have to avoid panic by all means."

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Brian O’Leary

O'Leary, who was one of the 11 astronauts named for a possible NASA Mars mission in the 1960s, authored three books that spoke about our connection to UFOs. He had also lectured on the subject across the world.

Regarding crop circles that he first saw in 1991 in England, he said in an interview: "The Crop Circle phenomenon, besides the hoaxed ones, is a very real phenomenon created by some unknown, probably non-human intervention," according to UFO Evidence.

O’Leary is also reported to have said, "There is abundant evidence that we are being contacted. Civilizations have been monitoring us for a very long time and that their appearance is bizarre from any type of traditional materialistic western point of view.”