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Space Science

The Second Moons of Earth 92

Posted by samzenpus
from the that's-no-moon dept.
Hugh Pickens writes "Despite a large body of work on satellite capture by the gas giants, mainly Jupiter and Saturn, there has been little published about the Earth's natural satellites other than the moon. Now Scientific American reports that although the moon has been with us for billions of years, Earth has also had countless other satellite companions and probably has one right now. These 'second moons' are boulders from the large population of near-Earth asteroids that get snagged by our gravity, orbit the Earth for a few months, then escape and move on. Known as 'Temporarily-Captured Orbiters' (TCOs), the irregular natural satellites are hard to see but astronomers spotted one such transient satellite in 2006. Dubbed 2006 RH120, the asteroid was a few meters in diameter, was captured by Earth for about a year and made four Earth orbits before being ejected after its June 2007 perigee back to interplanetary space. But TCOs are not just of academic interest. 'Once TCOs can be reliably and frequently identified early enough in a capture event they create an opportunity for a low-cost low-delta-v meteoroid return mission. The scientific potential of being able to first remotely characterize a meteoroid and then visit and bring it back to Earth would be unprecedented (PDF).'"
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The Second Moons of Earth

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  • Re:Better ideas (Score:4, Informative)

    by Grishnakh (216268) on Monday January 02, 2012 @12:40PM (#38564478)

    I'd put a whole freaking base on it while its in earth orbit, then see where it goes. If not a manned base, at least a robot research station.

    Did you miss the part in the description that said the last such meteoroid was only a few meters across? Are you going to send Lilliputians up there to build a base on it?

    Should be pretty interesting to see where it ends up. At least a radio beacon?

    I'm sure they can calculate exactly where it'll go once they know enough about its position and velocity. Even if it makes it out of the Solar System, it's going to be rather slow; if you want to send a probe out of the solar system, it's probably a lot faster to just build one and send it out there with rockets. To be captured by Earth's gravity, these things can't be going very fast.

  • by Trepidity (597) <delirium-slashdot@@@hackish...org> on Monday January 02, 2012 @01:38PM (#38564920)

    If I understand the paper correctly, there are configurations where the zero-velocity surfaces [wikipedia.org] of the sun and a planet coincide at some points, so an object orbiting the sun can transfer to a planetary orbit at one of the intersections without any other energy input, and then transfer back out again at the same or another intersection, again without any other energy input. Figure 1 on page 8 of the PDF [arxiv.org] has an illustration of some cases.

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