The iridescent cloud reveals new clues about ice formation in the Martian atmosphere (no little green men, sorry).

Curiosity, a set of NASA 's robotic "eyes" on the Red Planet, recorded 16 minutes of so-called noctilucent clouds flying overhead on Jan. 17. These clouds, sometimes referred to as twilight clouds because they're too faint to see in daylight, appear iridescent by scattering light from the setting sun.

Red-and-green-tinted clouds drift through the Martian sky in a new set of images captured by NASA's Curiosity rover using its Mastcam—its main set of "eyes." Taken over 16 minutes on Jan. 17 (the 4,426th Martian day,