Could Earth Capture a SECOND Satellite the size of the Moon?

  1. I'm doing a research paper based on mining asteroids or near earth objects.
    I was wondering, could we pull/move a relatively large asteroid About half as large as the moon could we use is as an anchor to launch missions?
    Thanks!
     
  2. jcsd
  3. Well I'm not sure if you already saw this link but
    http://www.universetoday.com/92022/earths-other-moons/

    Based on this article there have already been other natural satellites of the earth in the past. The question is whether it would be possible to keep the satellite in orbit for long enough to mine or launch missions from it.
     
  4. There are no asteroids half as large as the moon so that would be a big no.
     
    1 person likes this.
  5. True all the asteroids in the Asteroid Belt would not equal the size of our moon. I was taking the questions as a theoretical one.

    Why couldn't you have the missions launched from out moon itself instead?

    That would seem more feasible.
     
  6. Bandersnatch

    Bandersnatch 1,446
    Gold Member

  7. There are, since Pluto was demoted and branded with a number.
     
  8. Bandersnatch

    Bandersnatch 1,446
    Gold Member

    It was demoted to dwarf planet, not to asteroid, though.
     
  9. There aren't any such objects in the solar system but there may be such objects in interstellar space with trajectories that will bring them through our solar system at some time.
     
  10. TumblingDice

    TumblingDice 463
    Gold Member

    @Glappkaeft: Good point.

    @Mrspeedybob: Nearly 70% of the mass of the interstellar medium is made up of hydrogen atoms. The rest is mostly helium and heavier atoms, molecular clouds, and dust. Asteroids orbit the Sun, and most of them are inside the orbit of Jupiter.
     
  11. SteamKing

    SteamKing 9,591
    Staff Emeritus
    Science Advisor
    Homework Helper

  12. Correction. Most *known* asteriods are inside the orbit of Jupiter.

    Kuiper belt is quite farther out than Jupiter.

    While we detected many sub-kilometer object inside the orbit of Jupiter, in KB we only detected some of the largest stuff - and already we know about six objects larger than Ceres (>1000 km in diameter). It looks like in reality, "most asteriods are outside of orbit of Neptune".
     
  13. Thank you for posting important links! These are really helpful to know.

    Best Regards!
     
  14. You are right. :)
     
  15. TumblingDice

    TumblingDice 463
    Gold Member

    That doesn't make sense. If there were more *unknown* asteroids, how could you know?

    That's quite the opposite of what NASA/JPL indicates and Wiki clarifies
    Whatever the bodies outside of Neptune are called, most Kuiper belt bodies are made up of ices. Those wouldn't remain solid anywhere near Earth.
     
  16. Most of them are not massive enough to melt near Earth.
     
  17. When you ask, "Could Earth capture..." you have to add more about whether it is being guided with direct manipulations (meaning space tugs or whatever), or whether (at least in the final approach) it is allowed to try to insert into Earth orbit "hands off".

    With enough technology, I think it could be done with direct manipulation.

    But, another way of interpreting the question would be, could we manipulate the motion of a distant large object so that it naturally approaches the Earth and inserts into a stable orbit? This is similar to asking if a passing large body could enter the solar system, approach the Earth, and adopt a stable orbit.

    For these later cases of the object "passively" (at least for the final approach ) inserting into a stable orbit without direct additional manipulation, I'm not so sure... especially if the body is coming from higher than the Earth's orbit around the Sun.

    Imagine an object that is already in stable Earth orbit... now imagine how you would move it out of that orbit - you would have to apply an acceleration to do so. To me I think this means that the body had to decelerate in order to insert into the orbit...

    What would cause a body approaching the Earth and increasing attraction with approach to decelerate other than direct manipulation?
     
  18. Borek

    Staff: Mentor

    Large satellites orbiting planets have some interesting properties when it comes to the dynamics of the system. I believe I have read somewhere (possibly even on PF) that lack of other satellites of the Earth is due to the fact Moon interferes with their orbits, effectively ejecting them into space.

    IOW, it is not just a matter of putting something on the orbit, it is also a matter of keeping it in that orbit and not destroying the already existing system.
     
  19. This is what I understand to be a major "problem" in having a second large satellite in the Earth system. As moons go, our Moon is quite dense and massive, and simply inserting a large satellite into the system isn't going to fly. Small objects for mining and the like seem feasible, since they could possibly be constantly manipulated to keep them in orbit, but putting, say, Ceres into orbit, not even considering the energy required to do that, seems destined for failure over the long term. The interaction between the Earth, the moon, and the smaller, yet large satellite would, I think, end up with the smaller object getting booted out.
     
  20. tony873004

    tony873004 1,585
    Science Advisor
    Gold Member

    I think we have discussed this here before. I like simulating this stuff. There are no prograde orbits around Earth exterior to the Moon that are stable. Any object put in any prograde orbit exterior to the Moon gets ejected from the system in just a few orbits. Retrograde orbits exterior to the Moon are fine. But they're not too common in the solar system. Prograde orbits interior to the Moons are stable. But the Moon was once much closer to Earth. It would have swept that area (volume?) clear as it migrated to where it is now.
     
  21. I agree. Just out of curiosity, I created a simulation using the Sun, Earth, Moon, and Ceres. The only way I could keep Ceres in a stable orbit was by placing it in Earth-Moon Lagrange Points 3, 4, and 5. Everywhere else (including Earth-Moon Lagrange Points 1 and 2), Ceres either crashes into the Moon, or gets flung out of the Earth-Moon orbit.

    In absolutely every case (even with Ceres in the Earth-Moon Lagrange Points 3, 4, and 5), the extra mass was sufficient to slightly slow down the Earth's velocity around the Sun (from 29.8 km/s to 29.3 km/s), causing Earth's orbit to increase slightly (1.02 AU SMA) and increasing the length of a year (adding about 8.4 hours per year).

    The amount of energy required to move an object the size of Ceres would be huge. Well beyond all the energy of our combined nuclear weapons. However, once in either the Earth-Moon Lagrange Points 3, 4, or 5, no additional energy would be required to keep it in a stable orbit.
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?

0
Draft saved Draft deleted
Similar discussions for: Could Earth Capture a SECOND Satellite the size of the Moon?
Loading...