Are Phobos and Deimos tidally locked to Mars?

  1. The gravity of those moons is so low that when and if something "lands" on them it will be more like two spacecraft rendezvousing and docking than like a spacecraft landing on a world. And it hasn't been done yet.

  2. According to this list:


Deimos and Phobos are known to be tidally locked to Mars.

  1. Phobos and Deimos both orbit Mars in the same direction, prograde, at different distances from Mars. So it takes Deimos, the farther moon, longer to make one orbit around Mars than it takes Phobos, the closer moon.

So Phobos periodically passes in front of Deimos as seen from some places on the surface of Mars. Here is a link to a video of such an event:


And you could have researched that easily yourself.


  • $\begingroup$ To add some numbers to your response, the surface gravity of Phobos is ~.05% that of the surface gravity of earth, and Deimos is about .02% of the same. Phobos and Deimos are in a 4:1 resonance, so Phobos orbits 4 times for every one time that Deimos orbits $\endgroup$ Nov 3 '21 at 19:45

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