Top 5 Facts about Deimos

Added: 2026-05-23

[00:00:00]And today, the top five mysterious facts about Deimos, the forgotten moon of Mars. Coming in at number five, Deimos is tiny, even by moon standards, just 12 km across at its widest point, making it one of the smallest moons in the entire solar system.

[00:00:19]Unlike its heavily cratered sibling Phobos, Deimos has a surprisingly smooth surface.

[00:00:26]Scientists believe a thick blanket of loose dust and debris has filled in most of its craters over billions of years, giving it an almost eerily featureless appearance.

[00:00:37]Number four, while Phobos is spiraling toward Mars and doomed to be destroyed, Deimos is doing the exact opposite. It is slowly drifting away.

[00:00:48]Deimos orbits just beyond the distance where Mars's tidal forces would pull it inward.

[00:00:54]Instead, those same forces are gradually pushing it outward.

[00:00:58]And one day, in the distant future, Deimos may escape Mars entirely and drift off alone into the solar system.

[00:01:07]Number three, nobody is entirely sure where Deimos came from.

[00:01:11]The leading theory is that it is a captured asteroid, a wandering rock from the asteroid belt that strayed too close to Mars billions of years ago and was pulled into orbit.

[00:01:23]But the capture theory has problems.

[00:01:26]Captured asteroids typically end up in wild elongated orbits. Deimos orbits Mars in a nearly perfect circle.

[00:01:35]Something about its origin story doesn't quite add up and scientists are still debating it today. Number two, from the surface of Mars, Deimos barely looks like a moon at all. It is so small and so distant that it appears as little more than a bright star in the Martian sky.

[00:01:54]While Phobos races across the Martian sky twice a day. Deimos moves so slowly, it takes nearly 3 days to travel from one horizon to the other.

[00:02:04]Two moons of the same planet behaving in completely opposite ways. And the number one most mysterious fact about Deimos, it is the loneliest world in the solar system.

[00:02:15]And it is getting lonelier.

[00:02:18]As Deimos slowly spirals outward, Mars will gradually lose its grip.

[00:02:23]Eventually, in the far distant future, Deimos will break free entirely.

[00:02:28]Mars will be left with no moons at all.

[00:02:31]A planet alone in the dark.

[00:02:34]Two moons. One spiraling to its doom.

[00:02:37]One quietly drifting to freedom.

[00:02:40]Mars is the only planet in the solar system slowly losing everything.

[00:02:45]And it has no idea. That's our top five.

[00:02:48]If Deimos just won you over, smash that like button and subscribe for a new countdown every [music] week. Drop your next topic in the comments. I'll see you there.