So what is it? The Jet Propulsion Laboratory has yet to respond officially to press requests (including ours) for some context here (Update: see NASA's best guess at what that light is below), but a few people who would know have weighed in already. As NBC News spotted, one JPL employee said that the light was probably a "cosmic ray hit," an explanation that Surrey Space Centre's Doug Ellison agrees with.

"Cosmic ray hits" are a kind of strange space phenomenon. Essentially, space is full of cosmic rays, or high-speed atom fragments. They constantly bombard the Earth, although we don't really see them. They're almost certainly responsible for flashes of light experienced by astronauts in space, most famously on the Apollo missions. As it turns out, those exposures are not great for long-term eye health. In the case of the light "flash" above, the going explanation posits, the cosmic ray impacted Curiosity as it took the image seen here.

So are aliens shining lights up from their secret underground lairs on Mars? Almost certainly not. But that doesn't mean NASA isn't in the middle of some cool projects to explore the possibility of life beyond Earth. There are even some exciting actual discoveries on Mars itself, like this recent evidence that there might currently be flowing water on our neighbor planet.

Update: The Jet Propulsion Laboratory's Justin Maki explained what NASA thinks is behind the mysterious light. "We think it's either a vent-hole light leak or a glinty rock," he said in an emailed statement to The Wire. Maki was the lead for the engineering on Curiosity's cameras. Here's his full explanation:

Bright spots appear in single images taken by the Navigation Camera on NASA's Curiosity Mars rover on April 2 and April 3. Each is in an image taken by this stereo camera's right-eye camera, but not in images taken within a second of each of those by the left-eye camera. In the two right-eye images, the spot is in different locations of the image frame and, in both cases, at the ground surface level in front of a crater rim on the horizon. 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. The rover science team is also looking at the possibility that the bright spots could be sunlight reaching the camera's CCD 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. We think it's either a vent-hole light leak or a glinty rock.

This article is from the archive of our partner The Wire.