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See the Martian moon Phobos fly over a dust storm (earthsky.org)

submitted 5 days ago by supersquirrel@sopuli.xyz to c/space@mander.xyz

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ESA’s Mars Express has been orbiting Mars since December 2003, and it still sends back sensational images, such as these shots of the Martian moon Phobos passing above the red planet’s surface. These images capture Mars and Phobos from June 2025, and ESA released the images in December 2025. The immensely talented Andrea Luck processed the images you see here

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[–] WoodScientist@lemmy.world 3 points 5 days ago (1 children)

Eh. I never liked calling tiny captured asteroids "moons." There doesn't seem to be any lower limit on what's required to be a moon. That's why they're always discovering new ones around the gas giants. Assumedly, the actual number of moons orbiting Jupiter is "infinite," as you can keep counting until you're calling individual orbiting dust grains "moons."

I think Mars has zero moons. It has zero moons and a few captured asteroids orbiting it. I think a moon, to be a moon, should have to be spherical under its own gravity. Anything else is just a natural satellite.

[–] Skua@kbin.earth 9 points 5 days ago

There isn't a lower limit, it's just the word for a natural satellite. We used to call all of those just "satellites", but the language shifted when we started making our own satellites

There are some terms for the kind of moon you describe, though! Planetary-mass moon, major moon, or satellite planet are apparently all options. I like major moon best, personally

Oddly enough we also don't actually know how Phobos and Deimos came to orbit Mars. They may well not be captured asteroids (though that doesn't change their non-roundness, of course)

If you ask me, we should keep calling all natural satellites "moons", if for no other reason, so that we can use the delightful term "moonmoon" if we ever find such a thing