1977 Viking orbiter image of Phobos. The large crater on the left is Stickney. (Viking Project, JPL, NASA, apod980531)

     A 1978 Viking orbiter image, showing a slightly different view of the same part of Phobos (Viking Project, JPL, NASA, Edwin Bell II, NSSDC)

     Phobos imaged by the Mars Global Surveyor. The darkest moon in the solar system, Phobos may be a captured asteroid made of a loose mixture of ice and dark rock.
(Malin Space Science Systems, MGS, JPL, NASA, apod030701)

     A color image of Phobos, taken by the Mars Express, shows the inner moon of Mars in exceptional detail. (G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA, apod061203)

Above, an image of Phobos near the limb of Mars, taken by the Mars Express. The surface features are distorted by foreshortening, and by the motion of the moon and the spacecraft's camera, as it followed the moon. The image clearly shows how much darker Phobos is than Mars. Phobos is the darkest moon in the solar system, and of great interest because its structure and composition may well be unique; and the hope that it will soon be a target for direct exploration by a lander. (Image Credits: ESA / DLR / FU Berlin (G. Neukum), Planetary.org)

Above, a closeup of Phobos even closer to the limb of Mars, taken by the Mars Express. (Image Credits: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA , apod100317)

Above, a portion of a Mars Express image of the region near Gusev Crater (the Spirit rover landing site) shows the river-like structure which led to hopes that the crater might contain evidence of ancient water flow, an ancient shield volcano to the north of the crater, and at the bottom, an elongated shadow cast on the surface of the planet by Phobos. Phobos can never totally eclipse the Sun, being far smaller than our Moon, and even as close to Mars as it is, never covering more than about half the solar disk. Despite that, as shown in this image (and the one below), the penumbral shadow on the moon is clearly visible on the Martian surface. In the image above, the shadow is elongated because of the shape of the Moon, the angle at which its shadow struck the surface, and the fact that the image was built up line by line, from left to right (or vice-versa), and during the time it took to form the image, the moon (and its shadow) moved relative to the surface. In the image below, which was taken in more nearly real-time, the shape of the shadow is not quite as distorted. (Image Credits: ESA / DLR / FU Berlin (G. Neukum) / Stuart Atkinson, Planetary.org)

Above, a 1999 Mars Global Surveyor photo of the shadow of Phobos on western Xanthe Terra. Refer to the caption for the previous image, for notes about the shape of the shadow. (Malin Space Science, MGS, JPL, NASA, apod030329)

Above, an animated view of Phobos transiting (passing in front of) the Sun, as seen from the surface of Mars by the Opportunity Rover on its 45th Martian day ("sol") after landing on Mars, in 2004. Despite its proximity to the planet, Phobos is too small to completely cover the Sun, but as shown in the previous images, the partial eclipse casts a noticeable shadow on the surface of the planet. A comparison of the images also shows that Phobos has its long axis aligned along its orbit, as its elongated shape is obvious both in the shape of its shadow, and in its appearance as it passes in front of the Sun. Note: The original animation shows the moon passing from left to right, presumably due to the orientation of the rover camera at the time the images were taken; however, on this page the direction is reversed, to show the view that a northern hemisphere observer would have as Phobos moves eastward across the face of the Sun (in other words, the image is oriented so that north is on top and east on the left). (Image Credits: NASA/JPL/Cornell, Planetary Photojournal)

A 2008 enhanced color image of Deimos taken by the HIRISE spacecraft. Note the double crater at top left, and the indentation on the limb to its right. Those same features are shown at top right on the image above. A comparison of their position on the two images shows that the HIRISE image shows a view of Deimos which is almost completely different than the portion of the moon shown on the Viking image. The portion shown here is the side of Deimos which always faces Mars (like most moons, it rotates synchronously, meaning it always keep the same face to its planet). Since the HIRISE spacecraft orbits Mars only about 200 miles above its surface, and Deimos is about 12 thousand miles away, the view from the spacecraft is the same as the view from the surface -- namely, the "near" side of the moon. (Image Credits: NASA/JPL/University of Arizona, LPL)