How Mars’ Moon Phobos captures our imaginations

For a small chunk of lumpy rock that barely reflects any light, the Martian moon Phobos attracts a lot of attention. Perhaps because it is one of only two moons orbiting the planet, and its origin is unclear. But part of the attention is probably because we have such great images of her.

Phobos is the larger of the two moons of Mars, the other being Deimos. Scientists are uncertain about their history. They could be a pair of captured main-belt asteroids, two lobes of what was once a binary asteroid until capture separated them, or a second-generation object formed after Mars had already formed. Or they may be fragments left over from an ancient collision between more massive objects.

Phobos is not very big. It is about 26 km × 23 km × 18 km and not so massive as to be rounded. Studies of its density indicate that it is a debris-heap body held loosely by its own gravity.

When ESA launched its Mars Express orbiter in 2003, its mission was to study Mars. One of its instruments is the High Resolution Stereo Camera, a German contribution that produces color images with a resolution of up to two meters. The instrument also has a black and white mode, and the original image of Phobos was black and white.

Andrea Luck is a skilled image processor from Glasgow, Scotland, with a healthy enthusiasm for space imagery. He decided that the original B&W image, which he describes as epic, needed to be updated in color. “I was a little tired of seeing this epic photo online in just black and white, so I decided to jazz it up with some color!” he wrote on his Flickr page.

It is interesting to note that it is a single image, not a composite.

Here is the original B&W image.

HRSC’s mission is to obtain stereographic images of the Martian surface, capturing geological and morphological details. The goal is to map as much surface as possible. But at the bottom of the target list are images of Phobos and Deimos.

Images of Phobos have helped scientists better understand the odd moon, but they are not enough to draw firm conclusions. Fortunately, a mission to Phobos and its sister Deimos will be launched in a few years.

JAXA, the Japanese Aerospace Exploration Agency, is launching the MMX mission in 2026. MMX stands for Martian Moon Exploration. His goal is to understand the origin of Phobos and Deimos. MMX will also return a sample from Phobos in 2031. Once in ground labs, those samples should reveal a lot.

But for now, we can enjoy this rendered image of Phobos, which captures its nature as a fast, debris-strewn moon of uncertain origin.