[DouglasKC]

A photographic artifact of some kind...

[gibsonguy]

“A photographic artifact of some kind.”

Or marsh gas.

[rusty schucklefurd]

I agree. It Looks flat and one dimensional.

[KamperKen]

"A photographic artifact of some kind..."

I have seen a number of the rover photos with the luminous spots and if they were image processing artifacts I would assume they would appear in random positions on the photos, like on the rover itself. They all appear to be on the ground or near the horizon so their distribution across the pictures is not random as one would expect if they're artifacts.