Deimos

Lore & Background

While Phobos dominates the Martian sky with its rapid, rising-and-setting cycle, Deimos appears more like a bright star or a slow-moving planet, taking just over 30 hours to complete an orbit—longer than a single Martian day. Unlike the heavily cratered and jagged appearance of many small moons, Deimos possesses a surprisingly smooth surface. This is attributed to a thick layer of regolith that has buried much of its impact history, smoothing out the sharp edges of craters over billions of years. Its composition suggests it shares chemical similarities with carbonaceous chondrite asteroids, fueling the leading theory that it was once a wandering object from the asteroid belt captured by Mars's gravity. Future exploration missions aim to return samples from Deimos, as its low gravity and stable orbit make it an ideal staging ground for human expeditions to the Martian surface. It stands not just as a moon, but as a potential gateway to the Red Planet itself.

In Their Own Story

From the rust-colored dunes of Valles Marineris, the sky is dominated by the looming bulk of Phobos, racing across the horizon in a blur of gray rock. But turn your gaze to the opposite side, where the stars are beginning to pierce the thin atmosphere, and there it hangs: Deimos. It does not rush; it glides with a serene, deliberate slowness, a pale diamond suspended against the velvet black. A rover's camera pans across its face, capturing the subtle, dusty sheen of a world that has absorbed impacts for eons without breaking. Here, in the silence between two worlds, Deimos keeps its ancient watch, a quiet witness to the history of Mars.

Reader's Guide

Deimos stands as the smaller of Mars’s two moons, measuring approximately 12.4 kilometers in diameter with an irregular shape resembling a lumpy potato. This smoothing effect suggests a long history of micrometeoroid bombardment that has buried impact scars under layers of fine dust.

Did You Know?

• Deimos is so small that an astronaut could theoretically jump off its surface into space if they jumped hard enough.
• Unlike Phobos, which rises in the west and sets in the east, Deimos rises in the east and sets in the west for a Martian observer because it orbits slower than Mars rotates.
• The smoothness of Deimos's surface is so extreme that craters larger than 10 meters are virtually non-existent.
• Deimos takes about 30 hours to orbit Mars, which is slightly longer than a full Martian day (sol).