Maven made this image within 186 miles (300 kilometers) from the surface of the satellite of Mars Phobos. Orange is the average ultraviolet sunlight reflected from the satellite's surface, and blue is the far ultraviolet light from the extended upper atmosphere of Mars.
This creepy portrait of the Martian moon Phobos in ultraviolet light was captured with the help of the NASA Maven orbiter when they were upholstered.
Phobos is the closest satellite of Mars compared to Deimos, but less studied. In the 1950s and 1960s, some scientists believed that its unusual orbit, spiraling inward, suggests that it could be a hollow, artificial body. The small moon has long shallow grooves located on the sides, and is probably caused by the force of gravity of Mars. NASA officials say that with every hundred years, the distance of a moving satellite relative to the Red Planet is about 6.6 feet (2 meters).
In fact, Phobos is the nearest moon to its planet in the entire Solar System, which revolves around Mars just 3,700 miles (6,000 kilometers) above its surface. It is so close that it rotates within the sphere of a fine Martian atmosphere. The blue pixels forming the new image background are ultraviolet light scattered from the gaseous expanded upper atmosphere of Mars. The orange color comes from the longer ultraviolet waves of sunlight reflected from the surface of the moon. The NASA Maven mission (this is short for Mars Atmosphere and Volatile Evolution) managed to catch a frame and received an image with an ultraviolet spectrograph in December 2015, when its orbit intersected with the orbit of Phobos. The researchers hope to determine what the moon is made of, how it appeared, and whether there are organic molecules on its surface. (Previous measurements made by the Mars Express spacecraft found evidence of these organic molecules.)
“The image will allow Maven scientists to better assess the composition of this mysterious object, whose origin is still unknown,” NASA officials said in a statement.