This photograph was taken on May 19th, 2005 by NASA’s Mars Exploration Rover Spirit. It’s an image of sunset on Mars.
Click the image to see a higher resolution.
Via Mars TV:
This Panoramic Camera (Pancam) mosaic was taken around 6:07 in the evening of the rover’s 489th martian day, or sol. Spirit was commanded to stay awake briefly after sending that sol’s data to the Mars Odyssey orbiter just before sunset. This small panorama of the western sky was obtained using Pancam’s 750-nanometer, 530-nanometer and 430-nanometer color filters. This filter combination allows false color images to be generated that are similar to what a human would see, but with the colors slightly exaggerated…Because Mars is farther from the Sun than the Earth is, the Sun appears only about two-thirds the size that it appears in a sunset seen from the Earth.