This is the Martian moon Phobos as observed by the MAVEN spacecraft’s Imaging Ultraviolet Spectrograph. Orange shows mid-ultraviolet (MUV) sunlight reflected from the surface of Phobos. Blue shows far ultraviolet light which is scattered off of hydrogen gas in the extended upper atmosphere of Mars. Phobos blocks the background far UV light, eclipsing the ultraviolet sky. Comparing MAVEN’s images and spectra of the surface of Phobos to similar data from asteroids and meteorites may provide clues to the moon’s origin–whether it is a captured asteroid or was formed in orbit around Mars. The MAVEN data will also help scientists look for organic molecules on the surface of Phobos. Evidence for such molecules has been reported by previous measurements from the ultraviolet spectrograph on the Mars Express spacecraft.
Image Credits: CU/LASP and NASA