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Re:Two New Satellites for Jupiter by devrandomguy on Tuesday June 06, 2017 @11:28PM (#14503521)
> 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.

Re:Two New Satellites for Jupiter by eulo__ on Wednesday June 07, 2017 @12:10AM (#14503700)
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.

Re:Two New Satellites for Jupiter by askvictor on Wednesday June 07, 2017 @07:11AM (#14505194)
Aren't Saturn's rings hypothesised to have come about from moons smashing or disintegrating?
Re:Two New Satellites for Jupiter by neuroid on Wednesday June 07, 2017 @07:40AM (#14505391)
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-c...

Re:Two New Satellites for Jupiter by dogruck on Wednesday June 07, 2017 @02:01AM (#14504046)
Great question. That would be spectacular. Have we ever observed such an event? Seems like, statistically, relatively close solar bodies would rarely collide.
Re:Two New Satellites for Jupiter by ldenneau on Wednesday June 07, 2017 @03:09AM (#14504280)
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.