47 years to the day (25 July), the 'Face on Mars' was born and some believe it to be the closest ever sign of alien life.
When NASA's Viking 1 spacecraft was circling the planet in 1976, it snapped photos of possible landing sites for its sister ship Viking 2.
However, what came back was an image, which NASA describe as a 'shadowy likeness of a human face'.
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"An enormous head nearly two miles from end to end seemed to be staring back at the cameras from a region of the Red Planet called Cydonia," its website states.
The shadows in the photo showed a 'huge rock formation, which resembles a human head, formed by shadows giving the illusion of eyes, nose and mouth'.
A few days after the discovery, the space company unmasked the image and showed it to the public and fascination was through the roof.
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NASA had hoped that the release of the picture would be 'a good way to engage the public and attract attention to Mars'.
"Some people think the Face is bona fide evidence of life on Mars - evidence that NASA would rather hide, say conspiracy theorists. Meanwhile, defenders of the NASA budget wish there was an ancient civilization on Mars," said NASA.
Almost half a century on, the 'Face on Mars' has featured, not only in a Hollywood film, but on merchandise, books and talk shows.
"We felt this was important to taxpayers," explained Jim Garvin, Chief Scientist for NASA's Mars Exploration Program, on NASA's website.
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"We photographed the Face as soon as we could get a good shot at it."
Later on 5 April, 1998, Mars Global Surveyor flew over Cydonia for the first time, where Michael Malin and his Mars Orbiter Camera (MOC) team snapped a picture ten times sharper than the original Viking photos.
"It's not easy to target Cydonia," Garvin said.
"In fact, it's hard work.
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"We just don't pass over the Face very often."
And then again, on 8 April, 2001, Mars Global Surveyor went in for a second look.
"We had to roll the spacecraft 25 degrees to center the Face in the field of view," Garvin explained.
"Malin's team captured an extraordinary photo using the camera's absolute maximum resolution."
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Each pixel in the 2001 image spans 1.56 meters, compared to 43 meters per pixel in the best 1976 Viking photo.
"As a rule of thumb, you can discern things in a digital image 3 times bigger than the pixel size," he added. "So, if there were objects in this picture like airplanes on the ground or Egyptian-style pyramids or even small shacks, you could see what they were!"
Sadly, the picture has got nothing to do with alien life, rather, it's the Martian equivalent of a butte or a mesa which are common landforms around the West of America.
Sorry guys.
"It reminds me most of Middle Butte in the Snake River Plain of Idaho," Garvin said.
"That's a lava dome that takes the form of an isolated mesa about the same height as the Face on Mars."