A photograph taken by Nasa's Curiosity rover on Mars captured a mysterious glow on a distant marsh from Mars.
Black and white photograph shows desert landscape with high rocky hills in the background.
In front of the larger rock formations, a small elongated white spot appears to be passing.
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Nasa has previously admitted similar anomalies in photos taken by the probe. This image was taken on June 16, and although conspiracy theorists have said that photography is evidence of extraterrestrials on the Red Planet, it seems more likely that it was a cosmic ray, some sort of camera lens or sunshine reflection reflecting on the rocks.
The Curiosity rover landed on the surface of Mars in 2012 and is armed with 17 cameras. Since then, it has traveled the entire planet, sending huge amounts of data along with vast amounts of photographs. Many other captured images also contained anomalous lights.
The rover has two "navcams" mounted on its mast, which function as a stereo pair of cameras – a bit like the eyes. Black and white images capture panoramic 3D images and each has a 45-degree field of view, giving soil control teams a detailed view of the planet's terrain.
The image in question was taken by the right navcam. Unfortunately, the left camera was not looking in the same direction, and photos of the same scene and time showed that it turned to take a space selfie, showing parts of the ship on stones and dust on the ground.
The appearance and disappearance of the unidentified white bubble appear to have been rapid, since photos taken immediately before and after do not show the same unidentified phenomenon.
When another bright spot captured in photos taken by the rover was headlined in 2014, people claimed that it was "light from an alien hut."
But Justin Maki, the team leader who built and operates the Curiosity spacecraft, quickly put these theories in bed.
He said: "In the thousands of images we get from Curiosity, we see those with bright spots almost every week.
"This can be caused by impacts from cosmic rays or the sunlight shining on rocky surfaces, like the most likely explanations."
Cosmic rays are made up of highly charged atomic particles, usually from outside our own solar system, that travel through space almost at the speed of light and can produce visual effects on impact. They are more common on Mars than on Earth due to the thin atmosphere that does not provide an effective barrier to cosmic radiation.