The Second Moons of Earth

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Posted by samzenpus on Monday January 2, 2012 @05:31AM 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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metroid capture by Anonymous Coward · 2012-01-02 05:34 · Score: 4, Funny

not the best idea... (i think they're dangerous)
1. Re:metroid capture by flaming+error · 2012-01-02 06:44 · Score: 1
  
  Well, I think they're cute.
2. Re:metroid capture by superslacker87 · 2012-01-02 07:36 · Score: 2
  
  Tell that to Samus Aran.
  
  --
  I run Ubuntu skinned to look like a Mac on a PC. Go figure.
3. Re:metroid capture by rotorbudd · 2012-01-02 07:42 · Score: 1
  
  Tell that to the dinosaurs.
  
  --
  A bullet may have your name on it, but artillery is addressed to " Whom It May concern"
4. Re:metroid capture by metaforest · 2012-01-03 03:13 · Score: 1
  
  Ah... TCO..... Total Cost of Ownership.... (Pwnrship?)
  Gets kinda spendy... 65M years ago the population on this little blue rock dropped off dramatically. Could it have been a TCO that got too friendly?
5. Re:metroid capture by mcgrew · 2012-01-03 04:02 · Score: 1
  
  It wasn't a boulder a few meters wide that killed the dinasaurs, it was a rock the size of a large mountain. There is no way we could bring something that massive to earth.
  
  --
  Free Martian Whores!
Better ideas by vlm · 2012-01-02 05:36 · Score: 5, Interesting

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.

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

--
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
1. Re:Better ideas by Grishnakh · 2012-01-02 05:40 · Score: 3, Informative
  
  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.
2. Re:Better ideas by n5vb · 2012-01-02 05:43 · Score: 2
  
  Radio beacon with telemetry and a ranging transponder would be intriguing and probably not all that hard to deploy .. :)
3. Re:Better ideas by thue · 2012-01-02 05:47 · Score: 1
  
  > Should be pretty interesting to see where it ends up.
  This is Newtonian mechanics. We can calculate where it ends up pretty accurately.
4. Re:Better ideas by Hentes · 2012-01-02 05:57 · Score: 1
  
  Why do you need an asteroid for that? You can just put a probe in the same orbit whenever you like, it's not like an asteroid makes that any easier.
5. Re:Better ideas by Nyeerrmm · 2012-01-02 06:11 · Score: 5, Interesting
  
  Actually, trajectories of small bodies like that are quite interesting. Two things stand out to me (I did some of my graduate work looking at missions to small-ish asteroids like Apophis which is ~300 meters, so bigger than this but smaller than large asteroids).
  1. If this is loosely captured by Earth with multi-month orbits it is on the edges of the Earth's sphere of influence where the Earth and the Sun's gravity really interplay in weird ways and small uncertainties in its current state could turn into huge uncertainties later.
  2. For a very small asteroid, the surface-area-to-mass ratio is very high, meaning effects of solar pressure and the Yarkovsky effect will cause it to behave very differently. The ability to track an asteroid like this could greatly inform models of these effects.
  If you could find many of these and have a spacecraft able to rendezvous and deposit a tracker on new ones as we find them, it could greatly benefit studies of near-Earth objects. Of course, a mission to do that sounds extremely challenging (but very interesting to work on).
6. Re:Better ideas by Anonymous Coward · 2012-01-02 06:25 · Score: 3, Insightful
  
  What about the n-body problem?
7. Re:Better ideas by Toonol · 2012-01-02 06:28 · Score: 1
  
  The trouble is that if you can match courses with the object to drop a beacon, you can just dispense with the object and let the beacon follow the course on its own. It doesn't gain anything by being mounted on an asteroid... at least unless we make a beacon sophisticated enough it can somehow use the asteroid's resources.
8. Re:Better ideas by Nyeerrmm · 2012-01-02 06:30 · Score: 3, Interesting
  
  Understanding the effects for a small asteroid could inform our understanding of how larger asteroids would behave as well, thus serving to help us better predict contintent-killers like Apophis.
  Of course, I'd much rather bring them in closer and mine them, but that would be more difficult, so tracking would probably happen first (and be good practice for eventual capture missions).
  As far as allocation of resources go, that really depends. I'd have to see detailed studies on what a mission like this would cost.
9. Re:Better ideas by vlm · 2012-01-02 06:57 · Score: 1
  
  Doesn't this:
  
  It seems like it'd be more useful to capture them and exploit them for their mineral content.
  Depend directly on what you don't seem to like:
  
  This is interesting and all, but I have to ask, how useful is this knowledge?
  
  --
  "Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
10. Re:Better ideas by vlm · 2012-01-02 06:58 · Score: 1
  
  Not true, the asteroid is a bigger heatsink than the beacon, unless you're tracking something really small.
  
  --
  "Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
11. Re:Better ideas by dotancohen · 2012-01-02 07:05 · Score: 5, Interesting
  
  I'm sure they can calculate exactly where it'll go once they know enough about its position and velocity.
  No, all we know is that it is in a possibly-unstable orbit. If the orbit were simply enough that we could calculate it long term, then it would be stable enough to not be reejected. In fact, landing on the object in order to enjoy it's boost out of Earth orbit would require matching its orbit exactly, which would put the lander on an escape orbit itself. No chuck of iron necessary.
  If you didn't notice from the summary, one item made four orbits in a year, that is one orbit every three months. By Kepler's laws, that means that the object's distance from the Earth is twice the moon's distance. You would already be at escape velocity there, seeing as it just butts up against the Earth's Hill sphere. And all that is assuming a circular orbit, which is very unlikely. More likely, apogee is outside the Hill sphere and the only reason that the object stays in "orbit" is when the apogee is opposite the sun. As soon as the orbit rotates a bit, the object is lost.
  
  --
  It is dangerous to be right when the government is wrong.
12. Re:Better ideas by dotancohen · 2012-01-02 07:18 · Score: 2
  
  2. For a very small asteroid, the surface-area-to-mass ratio is very high, meaning effects of solar pressure and the Yarkovsky effect will cause it to behave very differently. The ability to track an asteroid like this could greatly inform models of these effects.
  That is interesting. Would you equate that to an analogue of a Reynolds number in fluids?
  
  --
  It is dangerous to be right when the government is wrong.
13. Re:Better ideas by Hentes · 2012-01-02 07:20 · Score: 1
  
  You don't need an asteroid to shoot a tracker into those orbits. The tracker being "on" the asteroid doesn't change anything, as its gravity is practically zero. It's not like you can "hitchhike" an asteroid, you have to match its speed before landing.
14. Re:Better ideas by Grishnakh · 2012-01-02 07:23 · Score: 1
  
  Not exactly. I was just saying that if you're going to mess around with a puny asteroid in the first place, it'd be better to just capture it and use it for mineral resources. But realistically, it probably isn't worth it unless the thing is 50% gold or something, and that isn't very likely. If you're going to mine asteroids, it'd be much more economically feasible to go after much larger asteroids rather than something that's the size of a car. Yes, to learn if these asteroids are filled with gold or platinum or iridium, you do need to send missions to go look at them in the first place, but the likelihood of them being all that valuable are small, so I was thinking it'd make more sense to send those missions after larger asteroids instead.
15. Re:Better ideas by Nyeerrmm · 2012-01-02 07:28 · Score: 1
  
  Actually it does.
  The second aspect of my statement focuses particularly on non-gravitational forces on the asteroid, which would not be measured by a free-floating beacon.
16. Re:Better ideas by Grishnakh · 2012-01-02 07:28 · Score: 2
  
  Ok, so we can't predict where it'll go very well. But even so, who cares where it'll go? It's so small that it really isn't useful for much, unless it's made of gold or platinum. A chunk of iron the size of a car isn't all that valuable. So what if it leaves Earth's orbit and travels to Alpha Centauri in 10k years? That's interesting and all, but it's not very useful. If we want to go to AC, we can just send a purpose-built probe there ourselves (although it'd still take a really long time). If we want to send probes to asteroids, it seems like we should be sending them to big ones like Apophis, both to see what they're made of and also to help predict their trajectories better so we can make sure we're not on a collision course.
17. Re:Better ideas by Anonymous Coward · 2012-01-02 08:37 · Score: 2, Insightful
  
  What about the n-body problem?
  Use numerical methods
18. Re:Better ideas by stevelinton · 2012-01-02 09:17 · Score: 1
  
  At the cost of slightly perturbing the orbits, couldn't you "harpoon" them with a transponder (or laser reflector) on a penetrator? Probably only needs to mass a few kg, could be launched from LEO by a modest solid fuel booster, and would just need a very small thrusters to make sure it hit point first. We can track the missile and the target with radar from here, aim for an impact velocity enough to lodge a hardened spike in rock.
  The much more difficult mission is to recover one. One approach would be to wrap the rock in some kind of ablative heat shield and then put it on a trajectory to impact in shallow water somewhere. If you don't mind waiting a few months or years for the impact it shouldn't need much delta-V. More challenging would be to try and capture it in LEO and then bring it down in a Dragon or Soyuz.
19. Re:Better ideas by HornWumpus · 2012-01-02 10:25 · Score: 2
  
  A chunk of nickle iron meteor would give us something to practice zero G refining techniques on. Obviously robotic missions. Building/inflating a parabolic mirror would be step 1. (Profit would not be till much later then step 4. If ever.)
  It would give us an excuse to start. I'd set an ambitious goal of blowing a small nickle-iron bubble.
  
  --
  John McAfee 'It was like that time I hired that Bangkok prostitute; to do my taxes, while I fucked my accountant'
20. Re:Better ideas by stevelinton · 2012-01-02 10:33 · Score: 1
  
  The attraction is the ability to study a steady stream of asteroidal rocks extremely cheaply. Bigger rocks either don't come along as often or don't come as close (close in the sense of the amount of fuel needed to reach them). The only exception is the Moon, which is (a) just one rock and (b) so big that you need significant fuel to land on it and take off again.
  Assuming you're talking unmanned, which seems likely, a mission to lurk somewhere suitable and study (and perhaps "tag" with a radar reflector) as many of these rocks as possible over say a 10-20 year period would cost comparatively little and we'd get to see a significant number of different samples of the local population of rocks. This would let us make reasonably solid deductions about the material the Earth formed from, which could have all kinds of applications.
  We'd also get a number of probes into the way things move around the complex Earth-sun-moon dynamics, which would be interesting and might also help plan future unmanned space missions, or divert future larger rocks.
21. Re:Better ideas by the+biologist · 2012-01-02 11:08 · Score: 1
  
  If we had tracking stations on these things, then we could use them to get a much better estimation of the distribution of mass in our solar system at any given time.
22. Re:Better ideas by ianare · 2012-01-02 11:28 · Score: 1
  
  Isn't being curious about the world enough of a reason ? Not everything has to apply to money or immediate use. Frankly, I'm disappointed to see this kind of position on a "geek" website.
23. Re:Better ideas by BJ_Covert_Action · 2012-01-02 15:32 · Score: 1
  
  Could give us some insight into unknown gravity field configurations throughout our solar system. That could prove to be pretty useful one day. Right now we mostly have only analytical models of our system's gravity field. If we could get some hard data of paths that we have not commonly traveled, we might find something useful.
  
  --
  Motorcycles, Robots, Space Gossip and More!
24. Re:Better ideas by Grishnakh · 2012-01-02 17:50 · Score: 1
  
  No, merely being curious is not enough of a reason: resources are limited, and there's a LOT of things out there to be curious about. So you need to pick carefully what you devote your research resources to. I am glad to see several other responses showing why this is a good thing to research (like the bit about these small asteroids being closer and more common than the big ones, so needing much less fuel to launch a probe to), but no, curiosity alone is never a good reason to investigate something.
  Just as an example, let's look at medical research. Let's say you had, at your disposal, a big team of medical researchers and sufficient funding to let them investigate and try to solve as many medical problems as you can in 10 years. What are you going to task them with? Solving some rare condition that only affects 10 people worldwide per year? Or curing Parkinson's Disease, or some common cancer, or heart disease, or something else like that that affects millions? Obviously, you'd pick the thing that affects lots of people (and is also something you think you can tackle in those 10 years of free funding), not something that affects only a few. Yeah, that sucks for the 10 people struck with that illness, but why should millions suffer or die with cancer so that 10 people can have a shot at a better life?
25. Re:Better ideas by lievendp · 2012-01-03 03:22 · Score: 1
  
  I would mount it with a small engine and remote control to have it do my bidding.
26. Re:Better ideas by mcgrew · 2012-01-03 05:02 · Score: 1
  
  Why would we go to the expense of mining asteroids when it's far cheaper, easier, and safer to mine here on Earth? I mean, until an asteroid made of unobtainium comes close.
  
  --
  Free Martian Whores!
27. Re:Better ideas by jc42 · 2012-01-03 06:27 · Score: 1
  
  As someone else pointed out here, numerical methods for our own probes give good results to roughly one month out, and they all need course correction every week or three to hit their targets. More precise measurements don't increase this much, because the basic problem isn't precision. A bigger problem is that we don't have very accurate maps of gravitational potential in most of the solar system. Tiny variations in gravity can have huge effects over the course of months and years. That's what chaos theory is all about. The projected error bars for a rock like this in an orbit like this, will grow indefinitely. This is why stories about whether a given rock will hit the Earth the next time around so often give a probability, not just "Yes" or "No".
  Also, the earlier comment that "This is Newtonian mechanics" is wrong for intervals past a few months. To get enough accuracy to predict whether it'll hit us in its next (or Nth) pass years from now, you need relativistic mechanics. After all, the GPS system requires relativity to get its meter-level accuracy, and it's dealing with things of known mass that are very close to the Earth.
  
  --
  Those who do study history are doomed to stand helplessly by while everyone else repeats it.
28. Re:Better ideas by mcgrew · 2012-01-03 08:41 · Score: 1
  
  Not everything has to apply to money or immediate use.
  Mammon worship demands that, and money is the US's predominant religion. There are far too many, even at slashdot, who equate "free" with "worthless" who don't realise that the one theing they need more than anything else is free (air). Those who equate "having more stuff" with "being a better person" ("How much are you worth?")
  These folks are flabberghasted by the likes of me, who are happy with a roof over their head, food, clothes, and transportation (and beer and electronics). I think those people are pitiful.
  
  --
  Free Martian Whores!
At the risk of being declared a space nut by Dexter+Herbivore · 2012-01-02 05:38 · Score: 4, Insightful

I really hope this does lead to capture of a metal rich meteoroid, it may cause havoc on the world metal markets but in the long run cheap minerals have to be good for the world economy.
1. Re:At the risk of being declared a space nut by Hentes · 2012-01-02 06:05 · Score: 1
  
  It's not cheap anymore if you have to go up for it.
2. Re:At the risk of being declared a space nut by TheDarkMaster · 2012-01-02 06:08 · Score: 2
  
  You are a space nut, and this is good. Yep, what more tempting target than an asteroid with hundreds of tons of metals difficult to achieve on Earth as rare earths, titanium, chromium, etc.? Maybe even silver and gold. The problem is that unfortunately many people think:
  
  1) can be transformed into a weapon?
  2) can be transformed into a weapon? (not repeated unintentionally, seriously)
  3) When will I profit from it in a month?
  
  --
  Religion: The greatest weapon of mass destruction of all time
3. Re:At the risk of being declared a space nut by jc42 · 2012-01-02 06:08 · Score: 1
  
  So do we have any credible estimates of the costs of capturing such near-Earth objects and mining them? Would it really be profitable with our current technology?
  I've read a few wide-eyed "sci-fi" suggestions about this, but nothing that would convince the management of any mining company to invest in it. Of course, I could have missed 99% of what's been written on the topic, and some of it might actually be accurate.
  
  --
  Those who do study history are doomed to stand helplessly by while everyone else repeats it.
4. Re:At the risk of being declared a space nut by daem0n1x · 2012-01-02 06:12 · Score: 3, Funny
  
  I think Heavy Metal is not allowed by the regime, because it's satanic and pollutes youth's minds.
5. Re:At the risk of being declared a space nut by khallow · 2012-01-02 06:12 · Score: 1
  
  They aren't that big. Would be an interesting source of materials for orbital activities, but the asteroid they spotted, if it were metal rich, would be a few dozen to few hundred tons, mostly iron and chromium.
6. Re:At the risk of being declared a space nut by Skapare · 2012-01-02 06:26 · Score: 2
  
  Hundreds of tons would not be worth it. But some of the objects out there probably have trillions of grams. That's a 't', the 20th letter of the English alphabet which implies a number with at least thirteen digits in decimal.
  
  --
  now we need to go OSS in diesel cars
7. Re:At the risk of being declared a space nut by gadget+junkie · 2012-01-02 06:50 · Score: 1
  
  You are a space nut, and this is good. Yep, what more tempting target than an asteroid with hundreds of tons of metals difficult to achieve on Earth as rare earths, titanium, chromium, etc.? Maybe even silver and gold. The problem is that unfortunately many people think: 1) can be transformed into a weapon?
  Yes, witness "the moon is a harsh mistress" by Robert Heinlein, circa 1966
  
  2) can be transformed into a weapon? (not repeated unintentionally, seriously)
  Ditto
  
  3) When will I profit from it in a month?
  the moment you'll find a technology to extract the reverse Delta-V to produce propellant.
  
  --
  "If a boss demands loyalty, give him integrity. But if he demands integrity, give him loyalty." (John Boyd, 1927-1997)
8. Re:At the risk of being declared a space nut by artor3 · 2012-01-02 06:50 · Score: 2
  
  Offtopic, but what is the point of the metric system if no one ever uses the prefixes? I have never once heard someone talk about teragrams or gigameters. It doesn't work that way in the other direction... people talk about nanometers or micrograms all the time. But in the large direction, people get to kilo and stop. In fact, they go out of their way to avoid the big prefixes, using phrases like "metric ton" instead of megagram.
  Just think how much clearer your post would be if the convention was to say "Hundreds of megagrams wouldn't be worth it, but some objects out there may have teragrams."
9. Re:At the risk of being declared a space nut by Anonymous Coward · 2012-01-02 06:57 · Score: 1
  
  I want to tell Astrologists about this, just to watch them panic.
10. Re:At the risk of being declared a space nut by garyebickford · 2012-01-02 08:20 · Score: 2
  
  Having looked into this a bit, it appears that most of the metals that might be found would probably not be economical to bring back to Earth for various reasons (we can't just toss them down as big, dangerous meteorites), but will be invaluable as raw materials for space development.
  
  --
  It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
11. Re:At the risk of being declared a space nut by rasmusbr · 2012-01-02 08:21 · Score: 1
  
  The SI unit of mass is actually the kilogram [kg]. If you want to be very anal, a gram is actually a millikilogram and a metric ton is a kilokilogram.
12. Re:At the risk of being declared a space nut by garyebickford · 2012-01-02 08:22 · Score: 1
  
  From my limited study of this, it appears unlikely to be cost-effective to bring back to the Earth's surface, but could be invaluable for building things in space.
  
  --
  It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
13. Re:At the risk of being declared a space nut by omfgnosis · 2012-01-02 08:48 · Score: 1
  
  I wish for the deaths of people I don't like! I'm different from them in some way, but I would be hard pressed to explain how!
14. Re:At the risk of being declared a space nut by Baron_Yam · 2012-01-02 14:23 · Score: 1
  
  I don't think we have the technology to make a profit on bringing a metal-rich rock to Earth, even if it is in orbit just a light second or two away.
  How were you planning on bringing it down without risking a huge impact crater where we don't want one?
And at least one .. by n5vb · 2012-01-02 05:47 · Score: 5, Interesting

.. is man-made .. :)
1. Re:And at least one .. by mrclisdue · 2012-01-02 06:04 · Score: 1
  
  And David Icke will tell you that the earth's moon is hollow, was placed there by aliens, etc.
  Certainly not man-made, but manufactured by a super species (not God.)
  cheers,
  me
2. Re:And at least one .. by Anonymous Coward · 2012-01-02 06:12 · Score: 1
  
  that's no moon.
Temporarily captured? by Hatta · 2012-01-02 06:12 · Score: 3

What causes these things to be only temporarily captured? If they escape orbit by their own momentum, they were never really in orbit in the first place. So either this is a misnomer, or there's some external force causing these objects to leave orbit. What is it? Tidal effects from the moon?

--
Give me Classic Slashdot or give me death!
1. Re:Temporarily captured? by dmgxmichael · 2012-01-02 06:31 · Score: 1
  
  Yeah, pretty much actually. I'm not an astrophysicist, so I'm sure one will give you the details, but for any object to have a stable orbit around the earth it's got to get into some harmonic resonance with the moon or else be kicked out by the moon's gravity eventually.
2. Re:Temporarily captured? by Trepidity · 2012-01-02 06:38 · Score: 4, Informative
  
  If I understand the paper correctly, there are configurations where the zero-velocity surfaces 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 has an illustration of some cases.
  
  --
  10 PRINT CHR$(205.5+RND(1)); : GOTO 10
3. Re:Temporarily captured? by thrich81 · 2012-01-02 06:41 · Score: 2
  
  I'm not an expert either but these objects are loosely "captured" by the Earth due to interactions mostly with the Sun I think. Even without the Moon this can happen. If the Earth were totally isolated then this couldn't happen via Newtonian mechanics but the presence of the Sun makes the whole system a three body problem with chaotic effects such as temporary captures. The definition of "temporary" depends on your timeframe -- not much in the Solar System is eternally stable due to multi-body gravitational effects anyway.
4. Re:Temporarily captured? by TubeSteak · 2012-01-02 06:50 · Score: 2
  
  If they escape orbit by their own momentum, they were never really in orbit in the first place.
  You're confusing "orbit" with "stable orbit"
  If it goes around [object] at least once, it was in orbit.
  If it stays in orbit around [object], it's in a stable orbit.
  If it leaves [object]'s orbit (either back into space or crashing into [object]) it was in an unstable orbit.
  
  --
  [Fuck Beta]
  o0t!
5. Re:Temporarily captured? by asjk · 2012-01-02 06:58 · Score: 2
  
  Great explanation. The relevent section is found in the PDF: 3.6 Orbit characteristics and residence-time distributions for temporarily-captured orbiters. Quoting in part "A geocentric two-body orbit is not adequate for describing the motion of TCOs even for relatively short time periods".
6. Re:Temporarily captured? by Anonymous Coward · 2012-01-02 10:15 · Score: 3, Funny
  
  That's exactly it. There's a very nice animated gif here of the old Saturn V third stage captured out of the blue a few years ago (mentioned by n5vb earlier in the thread). You can see that every time it gets near the moon, it gets either slowed down or sped up depending on if it comes before or after. On the final and sixth orbit, it comes just behind the moon which slingshots it away completely.
7. Re:Temporarily captured? by KenSeymour · 2012-01-02 15:37 · Score: 1
  
  From my college physics:
  Two bodies = stable elliptical orbits
  more bodies -> ejection possible if they get too close.
  The planets we have are the ones that are left. They don't cross paths much.
  Asteroids, comets, Oort-cloud objects can be ejected from the solar system.
  
  --
  "We can't solve problems by using the same kind of thinking we used when we created them." -- Albert Einstein
Obligatory by gestalt_n_pepper · 2012-01-02 06:18 · Score: 1, Funny

That's no moon....

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Please do not read this sig. Thank you.
Oblig xkcd by 16384 · 2012-01-02 06:22 · Score: 5, Funny

http://xkcd.com/307/
It would be neat to have a second moon by HangingChad · 2012-01-02 06:55 · Score: 1

I say we snag it, bag it and tag it.

--
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Notable exception by SteveFoerster · 2012-01-02 07:09 · Score: 1

1.21 gigawatts!

--
Space game using normal deck of cards: http://BattleCards.org
where were you people when the Iraq War by decora · 2012-01-02 08:50 · Score: 2

got started up in 2002? Where are you when we spend a trillion a year on boondoggles like Trailblazer or Turbulence? How about the VIPR teams - know how much we spent on those last year?
Answer: enough to hire a crapload of scientists to study rocks and tell us the future of the planet. you know, that big ball where we actually live, that gives us food and water and everything we need to survive.
For a year? by WindBourne · 2012-01-02 09:28 · Score: 1

That is interesting. That would give us enough time to put an ion engine on it or two and try to control it to keep it in orbit. It would not only be a simple way to capture an asteroid, but give us loads of practice at what it will take. A couple of meters in diameter is a bedroom sized item, so not that easy to control. But since it is here, if we can bring it down and then play with it, R&D it, that is great experience for going to large asteroids and mining them. Heck, if we are going to an asteroid around 2025, this makes great practice.

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I prefer the "u" in honour as it seems to be missing these days.
Re:the only reason gold is 'valuable' by Grishnakh · 2012-01-02 09:38 · Score: 2

Forget gold then, there's lots of other materials that are intrinsically valuable for their industrial uses. Even gold is highly useful for electrical applications due to its corrosion resistance, but copper would be a lot more useful.
Scientific research is nice and all, but finding ways of improving peoples' quality of life is better, and for that you need technology and materials and resources to build that technology.
Moon mining vs asteroid mining by Required+Snark · 2012-01-02 14:11 · Score: 1

How difficult is it to exploit this resource vs exploiting moon resources? I would think that the energy requirements would be smaller for a rock in orbit then going into the moon's gravity well and returning to earth. Of course any mining would require moving the body into a stable orbit.
I've read science fiction where solar reflectors are used to smelt nickel iron rocks in vacuum. Are there any technical studies about the feasibility of this? With automated processing, would it be economically feasible to just extract rare earths/precious metals and return them?
I've been rather cynical about private enterprise in space. Right now the only money making sectors are telecommunications and non-government imaging (SPOT, weather satellites). Everything else is government funded one way or another. Space tourism is just starting up, but still has to prove itself.
The only other near term economic reason to go is resources. As far as I know there have been no experiments with collecting solar energy and sending it to earth. Clearly energy extraction will take a large amount of fundamental R&D before we even know if it can work. These rocks could be an achievable goal for economically sustainable space exploration.

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Why is Snark Required?
Re:I hope they get their math right by Grishnakh · 2012-01-02 18:06 · Score: 1

I guess you also missed the bit about this rock being only a few meters wide.
Space elevator by Neil+Boekend · 2012-01-02 20:18 · Score: 1

Maybe, with some luck we can use one of them as a counterweight for a space elevator. Changing orbits is a hell of an energy drain, I know, but if it's already up there there are some slow but cool tricks to change it's orbit over a long period of time. Get it into a closer orbit (just outside geostationary) and get a cable to it. Since this is quite far from the moon the thing may remain stable for a long time (centuries) getting us time to get the tether up, devise a way to keep it outside geostationary but slow it down to 1 revolution per day (don't want to bind it down to earth with any delta-V. Your neighbours will dislike you for the rest of their (albeit short) lives and there will be a tether around the complete circumference of earth)

Ah, whishfull thinking.

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Well, I might have a way, but it only works on a semi spherical planet in a vacuum.