New images of Mars' largest moon, Phobos
The image shown above was taken on the 23rd March by a high-resolution camera on board the Mars Reconnaissance Orbiter, when it was just 6,800 km away. The most prominent feature in the image is the large crater Stickney in the lower right, which has is around 9 kms (5.6 miles) across and is the largest feature on Phobos. Mars' second moon, Deimos, is even smaller, at about 12 kms (7.5 miles) across. The very dark, tiny moons are thought to have been asteroids that were captured by Mars when they strayed a bit too far from the asteroid belt.
For more information about the Mars Reconnaissance Orbiter, click here.