Scientists are throwing cold water on yet another purported "alien" sighting by NASA's Mars rover Curiosity.

Though UFO enthusiasts may beg to differ, mission team members say a bright flash of light visible in Mars photos taken by the Curiosity rover on April 2 and April 3 almost certainly has a perfectly ordinary explanation.

"One possibility is that the light is the glint from a rock surface reflecting the sun. When these images were taken each day, the sun was in the same direction as the bright spot, west-northwest from the rover, and relatively low in the sky," Justin Maki, the lead for Curiosity's engineering cameras, told via email. [Mars Illusions: Photos of the "Face on Mars" and Other Martian Tricks]

"The rover science team is also looking at the possibility that the bright spots could be sunlight reaching the camera's CCD [charge-coupled device] directly through a vent hole in the camera housing, which has happened previously on other cameras on Curiosity and other Mars rovers when the geometry of the incoming sunlight relative to the camera is precisely aligned," added Maki, who is based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We think it's either a vent-hole light leak or a glinty rock."

The two black-and-white photos, which were snapped by Curiosity's right-side navigation camera, appear to show a small flash of light gleaming in the distance, in front of a crater rim that dominates the horizon. UFO buffs jumped on the images, touting them as possible evidence of advanced life on Mars.

"An artificial light source was seen this week in this NASA photo which shows light shining upward from...the ground," Scott Waring wrote at UFO Sightings Daily Monday, April 7. "This could indicate there there [sic] is intelligent life below the ground and uses light as we do."

Waring has found other peculiarities in Curiosity's photos. For example, back in December, he suggested that a panoramic picture snapped by the rover captured a "Mars rat" crouching between two rocks.

The supposed Mars rodent is an example of a psychological phenomenon called pareidolia, which refers to the tendency of the human brain to perceive familiar shapes in vague or random images, experts say. Another example of pareidolia is the famous "face on Mars" purported to be visible in pictures taken by NASA's Viking 1 orbiter in 1976.

The "Mars light" is something different, since it's not a product of anyone's imagination. But the odds are pretty slim that the light is a sign of Martian life, researchers say, especially since the flash is not visible in images of the same spot taken nearly simultaneously on April 2 and April 3 by Curiosity's left-side navigation camera. (The two navcams sit side-by-side on the rover's headlike "mast" and return images that help the mission team plan out Curiosity's routes.)

Other scientists have suggested that the flash may have resulted from a fast-moving cosmic ray striking the right-side navcam.

All of this is not to say that life has never existed on Mars, of course. Curiosity has already found evidence of an ancient stream-and-lake system, suggesting that the Red Planet could have supported microbial life billions of years ago.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on

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