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Jupiter gets up in Mercury's business - what happens next?

  1. Jan 6, 2015 #1
    I've been reading articles (from back in 2008) that speculate on what could happen if one day, billions of years from now, the gravity of Jupiter were to pull Mercury out of orbit.
    One of the possibilities discussed is that Mercury could be ejected from the solar system.
    If mankind were still around at that point, and they had - somehow - colonised Mercury, would they be able ride out on Mercury and see places outside the solar system?
    How long would it take Mercury to leave to solar system? Generations?

    How early would we be able to tell that Mercury had left its usual orbit, and when we did how soon would we be able to tell that Mercury was going to leave the solar system (as opposed to crashing into the sun or another planet)?
    Far-fetched I know, but it's a fun idea - to be able to hitch a lift out of the solar system on a colonised planet gone rogue.
    Many thanks,
  2. jcsd
  3. Jan 6, 2015 #2


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    Yes. Assuming the colony had enough power without the sun to keep from freezing.

    Entirely dependent on how close of an approach. But likelihood of a surviving colony would be inversely proportional. To get fast enough, the encounter would likely be so close as to cause massive quakes in Mercury.

    We could track Jupiter's movement, and thus Mercury's perturbation with increasing accuracy over time. Hard to say how long though. You'd get a cone of probability - like the kind you see then use when tracking hurricanes.
  4. Jan 6, 2015 #3
    Well, I'm not sure mankind would ever quite be interested in trying to terraform Mercury—in the first place. And even if it were colonized, I'd say that our descendants would, if advanced enough, already have the technology to explore outside of our solar system long before then—without the rare chance of planetary ejection.

    As for orbit changes and prediction times, I'm honestly not an expert on that stuff; someone with better knowledge of those dynamics will probably answer that more deeply for you. But even if civilization decided to stay on a planet like Mercury as it got ejected, they would have to wait a very, very long time to see anything too interesting, and they'd have to find a way to keep themselves warm as the planet retreated farther and farther out; interstellar space is simply too vast and empty, so seeing other star systems and physical objects will not be of an occurrence at all. There really shouldn't even be a point in people doing such a thing; they'll already, for sure, have likely colonized other systems by that time with other more reliable methods, if their technology was advanced to that point.

    Here may be a useful link for you to look over about interstellar travel: http://astronomy.nmsu.edu/tharriso/ast105/Interstellar.html
    Last edited: Jan 6, 2015
  5. Jan 6, 2015 #4


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    Good point. Exiting the solar system might happen in a reasonable time. Encountering anything after that would be for whatever organisms the descendants of Mercury evolved into - cause they wouldn't be definably human by that time.
  6. Jan 6, 2015 #5


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    If Jupiter is to kick Mercury out of the solar system, it would have to at least give it the escape velocity of ~70km/s. At this lower bound speed it would take it ~ a month to travel 1 AU. So if Mercury were traveling on an approximate straight line out of the solar system, it would take a few months to get out to where the outer planets are, and then something like a few years to leave "the solar system" and enter the kuiper belt. It would take much longer to exit the Oort cloud which is roughly 1Ly across (4000 years). The numbers here will be similar to the numbers for Voyager (order of magnitude). Of course, it's possible for Jupiter to give Mercury a much bigger kick, and it will then leave the solar system much quicker. Jupiter has enough energy to kick Mercury up to speeds in excess of 500km/s (although, a significant fraction its energy would have to be transferred to Mercury at that point), so you could have it going almost 10 times faster than the lower limit. Even then, though, it'd still take hundreds of years to exit the Oort cloud, and thousands of years to reach the nearest stellar neighbors.
  7. Jan 7, 2015 #6
    It is an amusing idea that is fun to speculate about, however not in our lifetimes, or the lifetime of the human race as we know it. This extract from the relevant paper

    The experiments yielded one evolution in which Mercury falls onto the Sun at 1.261Gyr from now, and another in which Mercury and Venus collide in 862Myr. In the latter solution, as a result of Mercury's unstable behavior, Mars was ejected from the Solar System at 822Myr.

    From: Batygin, K. and Laughlin, G. "On the Dynamical Stability of the Solar System"
    arXiv:0804.1946v1 [astro-ph] 11 Apr 2008

    Available here.
  8. Jan 9, 2015 #7
    I doubt the resulting velocity could be large enough to make this a feasible alternative of a seed ship just from a gravity interaction between planets.Mix in a double-star system and the black hole in the center of our galaxy, however, and:
    Not exactly safe for the "passengers" though.

    [On the off-chance that you are asking for a sci-fi plot, you do not have to wait until it happens naturally. We could perhaps give it a nudge.
    It could be better to do with the Earth itself though, taking the Moon along for the ride, as then tidal heating can even keep the surface almost habitable, as per the linked wiki page. Or we could dig in towards the core, I guess.
    But this discussion is more suited for the Science Fiction and Fantasy forum and not this one.]
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