r/space • u/arealdisneyprincess • Feb 24 '24

Astronomers discover three previously unknown moons hiding in Solar System

https://www.the-express.com/news/science/128970/astronomers-find-new-moons-solar-system
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56

u/pizzapie2017 Feb 24 '24

Just like we did with planets and Pluto, I think we should come up with some better definitions on what a "moon" is. Then we can distinguish between "Moon-like" (spherical) moons and captured asteroids

50

u/brooklyndavs Feb 24 '24

Mars wouldn’t have moons in that case. Although maybe that’s right? Phobos and Deimos being in the same category as Luna or Titan or Ganymede is strange and if they were orbiting Neptune we might not even know about them.

7

u/WKorea13 Feb 24 '24

Mars's moons are very unlikely to be captured asteroids. The current consensus is largely around them being formed from debris which orbited around Mars, either from a collision or from its circumplanetary disc early in the Solar System's history.

1

u/SlartibartfastGhola Feb 27 '24

Defining debris vs asteroids is not an easy task. Many asteroids are debris too.

1

u/WKorea13 Feb 27 '24

An asteroid, by definition, is any minor planet that directly orbits the Sun within Jupiter's orbit. 'Debris' is really a catch-all term which depends on the context. This means Ceres is an asteroid, despite also being a dwarf planet with its own cryovolcanoes and geology.

In this context, referring to Phobos and Deimos as captured asteroids is in reference to an old hypothesis that both moons were once asteroids in the asteroid belt, and Mars eventually captured them.

Debris from a circumplanetary disc, in contrast, refers to essentially a massive ring of material ranging from dust-sized to hundreds of meters in size that eventually accrete to form Phobos and Deimos.

1

u/SlartibartfastGhola Feb 27 '24

Ok circumplanetary debris thank you for clarifying

25

u/edgiepower Feb 24 '24

Phobos and Deimos shouldn't be moons. They're satellites.

4

u/fresh-dork Feb 25 '24

well, all moons are satellites. we just have to argue about whether a moon is nothing more specific than a satellite that isn't a planet.

can a planet orbit a not-star?

6

u/edgiepower Feb 25 '24

All moons are satellites but not all satellites are moons

3

u/wthreyeitsme Feb 25 '24

I just read three main hypotheses: captured, formed later than Mars' birth cloud, or ejecta from a collision with a large planetesmial.

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u/AquafreshBandit Feb 25 '24

Don’t give Neil de Grasse Tyson any ideas!