The black and white photograph shows the desert landscape with high rocky hills in the background.
In front of the larger rock formations, a tiny elongated white blob appears to be streaking past.
Nasa has previously admitted to similar anomalies in pictures taken by the probe. This image was taken on 16 June, and while conspiracy theorists have said the photograph is evidence of extra-terrestrials on the Red Planet, it appears more likely to have been a cosmic ray, some kind of camera lens flare or sunlight reflecting on rocks.
The Curiosity rover landed on the surface of Mars in 2012, and is armed with 17 cameras. Since then it has roamed all over the planet, beaming back huge amounts of data along with vast quantities of photographs. Many other pictures it has captured have featured anomalous lights too.
The rover has two mounted “navcams” on its mast, which act as a stereo pair of cameras – a bit like eyes. The black and white images capture panoramic 3D imagery and each has a 45 degree field of view, giving ground control crews a detailed view of the planet’s terrain.
The image in question was taken by the right navcam. Unfortunately, the left camera wasn’t looking in the same direction, and photos from the same set and time show it having swivelled down to take some kind of space selfie, showing parts of the craft over rocks and dust on the ground.
The appearance and disappearance of the unidentified white blob appears to have been rapid, as photos taken immediately before and after don’t show the same unidentified phenomenon.
When another bright spot captured in pictures taken by the rover made headlines in 2014, people claimed it was “light from an alien hut”.
But Justin Maki, the leader of the team that built and operates Curiosity’s navcams rapidly put those theories to bed.
He said: “In the thousands of images we’ve received from Curiosity, we see ones with bright spots nearly every week.
“These can be caused by cosmic-ray hits or sunlight glinting from rock surfaces, as the most likely explanations.”
Cosmic rays are formed by highly charged atomic particles, often from outside our own solar system, which travel through space at almost the speed of light and can produce visual effects upon impact. They are more common on Mars than on Earth due to the thin atmosphere which doesn’t provide as effective a barrier to cosmic radiation.