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

The Sun sets differently on Mars. Part of that is due to its distance from the star (an average of 142 million miles versus Earth’s roughly 93 million miles), but it also has to do with the planet’s atmosphere. A great example of the effects can be seen in the Red Planet’s noctilucent clouds.

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.