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> The great majority of Jupiter's 69 known moons travel in retrograde orbits, meaning they travel in the direction opposite the planet's spin. Sketchy! I don't

> The great majority of Jupiter's 69 known moons travel in retrograde orbits, meaning they travel in the direction opposite the planet's spin. Sketchy! I don't suppose we have a prediction for the next anticipated lunar collision? Surely this system isn't stable. If two moons in opposite orbits collide, then there would presumably be an even more spectacular event when the majority of the combined mass of those moonlets fall straight down into Jupiter. Imagine a ~1km ball of magma zipping past the Roche limit and punching a hole right through the Jovian atmosphere.

eulo__ 9y ago
http://home.dtm.ciw.edu/users/sheppard/satellites/jupsatdata.html http://home.dtm.ciw.edu/users/sheppard/satellites/jupsatdata... Having a quick look at the data shows the inner moons travel in prograde, while the outer ones travel in retrograde. So although there may still be collisions in the future, unfortunately it looks like most of the collisions happened long long ago.
dogruck 9y ago
Great question. That would be spectacular. Have we ever observed such an event? Seems like, statistically, relatively close solar bodies would rarely collide.
- ldenneau 9y ago
  Comet Shoemaker-Levy 9 in 1994. The comet had been captured decades earlier after entering Jupiter's Roche limit and was actually in orbit around Jupiter. Collisions in the main asteroid belt have been observed, but only after impact. The signature is a puff of dust from the impact that fades after hours or days as the dust spreads. The statistics are imprecise, but collisions between kilometer-scale asteroids might have decades or hundreds of years between them. Impacts are rare though. There's a reason they call it space. If you were standing on an asteroid in the main belt, the nearest asteroid to you would be so far away that you could not see it.
askvictor 9y ago
Aren't Saturn's rings hypothesised to have come about from moons smashing or disintegrating?
- neuroid 9y ago
  There is another theory suggesting otherwise [1]: Saturn’s mid-sized moons are like the monsters in late-night horror movies. Smash them into tiny pieces, and they glue themselves back together as new versions of the old moons. This new finding contradicts a theory that Saturn’s rings were caused by moons colliding. [1]: https://www.newscientist.com/article/2132906-saturns-moons-could-reassemble-after-a-cosmic-smash-up/ https://www.newscientist.com/article/2132906-saturns-moons-c...

eulo__ 9y ago

http://home.dtm.ciw.edu/users/sheppard/satellites/jupsatdata.html http://home.dtm.ciw.edu/users/sheppard/satellites/jupsatdata... Having a quick look at the data shows the inner moons travel in prograde, while the outer ones travel in retrograde. So although there may still be collisions in the future, unfortunately it looks like most of the collisions happened long long ago.

dogruck 9y ago

Great question. That would be spectacular. Have we ever observed such an event? Seems like, statistically, relatively close solar bodies would rarely collide.

ldenneau 9y ago
Comet Shoemaker-Levy 9 in 1994. The comet had been captured decades earlier after entering Jupiter's Roche limit and was actually in orbit around Jupiter. Collisions in the main asteroid belt have been observed, but only after impact. The signature is a puff of dust from the impact that fades after hours or days as the dust spreads. The statistics are imprecise, but collisions between kilometer-scale asteroids might have decades or hundreds of years between them. Impacts are rare though. There's a reason they call it space. If you were standing on an asteroid in the main belt, the nearest asteroid to you would be so far away that you could not see it.

askvictor 9y ago

Aren't Saturn's rings hypothesised to have come about from moons smashing or disintegrating?

neuroid 9y ago
There is another theory suggesting otherwise [1]: Saturn’s mid-sized moons are like the monsters in late-night horror movies. Smash them into tiny pieces, and they glue themselves back together as new versions of the old moons. This new finding contradicts a theory that Saturn’s rings were caused by moons colliding. [1]: https://www.newscientist.com/article/2132906-saturns-moons-could-reassemble-after-a-cosmic-smash-up/ https://www.newscientist.com/article/2132906-saturns-moons-c...