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I also know how unlikely this situation is, so please refrain. From telling me "it won't happen."

Jupiter is sent on a spiral into the inner Solar System. Both Earth and Mars enter orbit around the gas giant and extreme chaos is caused now by the unexpected tidal pull of Jupiter and the other moons. Jupiter settles into a stable elliptical orbit around the sun a little closer than our current position. We were amazingly lucky.

Now, how lucky are the nice people in the moon colonies? Is there a better chance that our moon became one of Jupiters' moons, switching from orbiting the Earth to orbiting Jupiter? Or is it more likely that the moon and the unfortunate scientists on it were swallowed up by Jupiter? What would be the timescale involved assuming the Moon stays within Earths orbit for a short period before being ejected from the Jupiter System? Assuming the moon people have technology fifteen years more advanced than modern tech, what is the maximum "point of no return" or the point at which they have no choice but to evacuate?

Extra information:

I have decided that the Earth will enter the orbit of Jupiter at 32,000 mph and maintain that orbital speed. The moon should be traveling at 4,800 mph roughly. I'm not sure if this helps or not.


I would prefer the moon entering a stable orbit for at least a short period of time (maybe a few months to a few years) and then what happens happens.

  • $\begingroup$ Under those circumstances, I'd be just as worried about Earth as the moon (or perhaps more so, as the Moon people are used to dealing with harsh conditions). $\endgroup$ Mar 19, 2015 at 14:14
  • $\begingroup$ Society is already virtually collapsed as much vital infrastructure has been destroyed by flooding and increased seismic activity caused by the pull of the other moons and Jupiter. There is still government but they are trying to cope. The story will take place on the moon first and then on the earth. This is for a series of short stories involving the same characters. $\endgroup$
    – Jax
    Mar 19, 2015 at 14:19
  • $\begingroup$ It would be possible, if improbable, for the Moon to be captured into a stable orbit, but it would be more likely that it was ejected in a series of interactions with the Earth-Jupiter system and the other bodies orbiting Jupiter. Hitting Jupiter itself is a real possibility as well. Putting numbers to these scenarios is difficult. I don't think that the Moon would remain in a stable orbit around Earth for long. $\endgroup$ Mar 19, 2015 at 14:20
  • $\begingroup$ @JasonPatterson That might still leave possibilities for this story, if he's planning to move from Moon to Earth anyway. Anything with orbits is going to happen on a fairly slow timescale, from the perspective of a set of characters in a story. So the real question might be, what is the progression and time-frame here? How long can they stay, and how long do they have to evacuate when they realize Moon is on a course toward being ejected/consumed. Even weeks could be enough for a good story. Months or years give plenty of leeway. $\endgroup$
    – Bryon
    Mar 19, 2015 at 14:30
  • $\begingroup$ Note that no matter how soon you start evacuating, you can't get everybody off of Earth. $\endgroup$ Mar 19, 2015 at 18:04

2 Answers 2


Everyone dies horribly.

First, because the tidal disruption kills everyone.

Second, because of the tidal disruption thousands of volcanoes blow up simultaneously, poisoning the air (killing everyone) and enveloping the earth in the mother of all winters (killing everyone).

Third, the insanely high radiation belts of Jupiter kill everyone.

Fourth, other satellites of Jupiter are destabilized by the Earth and eventually Barrel into the planet (killing everyone).

  • 1
    $\begingroup$ Ummm...the tidal disruption would not kill everyone directly. The atmosphere might screw us. Both ozone and magnetic field would probably stop the Van Allen belts from killing us. I also doubt that all 63 moons of Jupiter will fall into the planet because of the addition of a few satellites. I think you are exaggerating in your answer. $\endgroup$
    – Jax
    Mar 19, 2015 at 18:38
  • $\begingroup$ @DJMethaneMan He didn't say 'all other' - just 'other' - how many moons of Jupiter would it take to crash into the Earth to kill everyone? I'm gonna go with 1. $\endgroup$
    – corsiKa
    Jul 7, 2016 at 14:54

Well actually a 32,000 mph orbital speed means that the radius of the orbit of the earth around Jupiter is around 621 000km, which is less than the Roche Limit of Jupiter 900 000km. So the Earth gets crushed into pieces. The moon probably too.

  • $\begingroup$ This assumes that the orbit Earth enters into is circular, which seems unlikely. $\endgroup$
    – HDE 226868
    Mar 19, 2015 at 15:49
  • $\begingroup$ @HDE226868 I am not sure how the Roche Limit deals with eccentric orbits, but I don't think that the whole orbit needs to be inside in order for the satellite to be destroyed. $\endgroup$ Mar 19, 2015 at 16:02
  • $\begingroup$ True, but the orbital speed won't be constant in an elliptical orbit. I don't think that 32,000 is realistic given how fast Earth would have to be traveling, anyway. $\endgroup$
    – HDE 226868
    Mar 19, 2015 at 17:30
  • $\begingroup$ Actually, the moon will escape into space. At such a low speed, its orbital radius would be about 0.2 AU, and its period (the new "month") would be 2 and a half years! Jupiter's Hill radius is currently around 0.34 AU, but after moving to roughly Earth orbit, the hill radius would fall to 0.065 AU, or about 10M kilometers. Most of the existing moons of Jupiter would be pulled into solar orbit. $\endgroup$ Mar 19, 2015 at 17:58
  • $\begingroup$ @HDE226868 I simply took our actual orbital velocity and increased it a little. $\endgroup$
    – Jax
    Mar 19, 2015 at 18:41

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