Earth Sun Trojan Asteroids

guest blogger john hare

Making use of off earth resources is a fairly constant topic of discussion. A recent Dennis Wingo comment made me think of a few paragraphs scattered through Mining The Sky by John Lewis. It is suggested that there are more asteroids in Jupiters’ Lagrange points than there are in the main asteroid belt. An asteroid has been found in a mars Lagrange orbit. Earth and Venus should be better collection points than mars. Earths’ L4-5 points are very difficult to see given the distance and sun angle. Lagrange points are actually volumes that could be millions of miles in diameter.

If I understood all the above correctly, it is possible that there are hundreds to thousands of asteroids in each earth sun L4-5 volume. They should be a cross section of types representing all known and unknown asteroid classes. This could represent one of the best possible concentrations of off earth wealth in the solar system for the next dozen generations. The points are at the same distance from the sun as the earth, so solar power and radiation are similar to that of the lunar surface.

If large numbers of asteroids of various types are semi-concentrated at 1 AU, a small probe could verify their existence with a flight path just sunward of the points. It could just miss the Lagrange focusing volume and keep going as an NEO spotter at distances well inside earths’ orbit if it turns out that the volumes are not worth exploring. The secondary mission of mapping NEOs that spend most of their time inside earths orbit would be worthy by itself. Those NEOs are exceptionally hard to spot from the earths’ surface. If the L4 or 5 volume is worth exploring though, a small burn could send the probe into the region for an extended survey of a concentrated resource base. The existence of the full spectrum of asteroid resources in one location would be of enormous value.

If a probe did locate large numbers of asteroids at the earth L points, a follow up sample return mission could visit dozens of bodies with quite modest propellant requirements. ISRU could possibly even occur at this early date if some available ice is located on one of the little bodies. A little bit of water could go a long way toward making the return trip more feasible. A small solar power system could crack it into H2 and O2 over a period of months, and be left behind for the next use. If hydrocarbons are located, then follow up missions could be even more efficient by using a small refinery to produce some cheaper form of fuel.

A serious manned prospecting mission could be more economically feasible than a mars mission, if enough resources are proved out in the robotic missions. It seems possible that metal rich bodies would be co-orbiting with volatile rich bodies and with enough other necessary ingredients to make an extended stay relatively self supporting. Water and minerals for a greenhouse, possibly Bigelow inflatable. Hydrocarbons as plastic and fuel feedstock. 24/7 solar power at earth normal concentration. Access to hundreds of locations that concentrated things with a mechanism totally different than terrestrial methods. Has it been proven that platinum must be parts per million mixed with something else? Is it possible that there is a process that concentrates precious metals to parts per hundred, or even pure chunks? I don’t know, and believe it possible that nobody else knows either for a definite fact.

If there is a serious material concentration at the earth sun L points, then a case can be made that a serious colony there would fare better than on mars. Both the raw materials and the zero gee for building SPS arrays would be at one basic volume of space at a constant distance from both the earth and sun. They could be drifted to GEO without going through the Van Allens, and provide power to the factory, moon, or solar sail of another vehicle by laser while in transit. The laser would be sent back to the factory for the next delivery with a microwave system installed for terrestrial power supply. Launch windows would be constant even though trip times would be fairly long. The two way supply pipeline could make constant use of whatever vehicles were tasked to the job.

Cyclers could be in constant use. I’m sure someone somewhere has worked the orbital numbers on a cycler with a one year elliptical orbit that arrived at both locations every year. It seems possible that there would be some special solar orbit that hit both L4 and L5 every year with earth access along the way, though I have no idea how to do it. Even though the trip times would be comparable to mars, the constant windows would allow a much higher usage rate of the ships involved. 

There are thousands of NEOs with less time and delta V to reach from earth than the Lagrange points. A major question to me is how many of them have a diversified material availability that seriously leverages exploitation. How much time and money is required to prospect a dozen of them in a dozen orbits? Do any of them lend themselves to the complete process of life support, manufacture, and transportation of useful exports? Precious metals, complete SPS farms, exploration fuel base, and so on. It seems possible that no one body has the diversity to support a real off earth colony that is financially self sufficient, especially compared to a hundred or a thousand bodies.

If this is all wrong, then we can laugh at it all with little lost time. If there is something here worth looking into, then step one is to find the studies that must have been done already and look them over. Just because I haven’t seen any reference to this idea doesn’t mean that it hasn’t been checked out.

The following two tabs change content below.


I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.

Latest posts by johnhare (see all)


About johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
This entry was posted in Uncategorized. Bookmark the permalink.

16 Responses to Earth Sun Trojan Asteroids

  1. Karl Hallowell says:

    The thing is though, we’ve only found a few asteroids anywhere near the Earth-Sun Lagrange points, 3753 Cruithne, which an Earth crosser is in a resonance orbit with Earth and probably could be shifted to L4/5 with relatively low delta v (inclination seems to be the biggest problem).

    There might be asteroids in the L4/5 points, but despite their relative nearness to the Sun from our point of view, we haven’t seen anything in orbit. That means whatever is there is rather small.

    The L4/5 of the Sun-Jupiter system are well observed. There’s no way the Trojan asteroids there have more mass than the asteroid belt. Having said that, I wouldn’t be surprised if the mass is more concentrated than in the main belt and relative velocities of the asteroids lower. Dynamics with Jupiter also make it relatively easy to sling stuff into the inner Solar System, I think.

  2. john hare says:

    I am going by a single dozen year old reference “Mining The Sky” which is a bit chancy. Trying to spot small dark bodies low in the sky at 93 million miles would tend to be a bit difficult. The distance from an observatory is only slightly less than the main belt asteroids and we are looking at crescent rather than full ‘moon’ reflections although they are closer to the sun and reflect more per unit area. It is my guess from your statement that any asteroid in the L4/5 locations would have to be smaller than half the diameter of the smallest known main belt asteroid to both be there and not yet discovered. The question is, what size is that, and how many may have accumulated at each point?

    Page 189 of the book suggests that there may be more mass in the Jupiter Trojans than the main belt. Since this is what triggered my thought process in this post, it would be interesting to know what the more up to date estimates are.

    Does anybody happen to know the trip times and deltaV requirements for Earth to L points and back offhand? Even if the right masses are there in dispersed form, the transportation has to work or it is a commercially useless concept.

  3. Rand Simberg says:

    I don’t know if John Lewis discussed this, but not all Trojan points are created equal. How stable and well defined they are is a function of the relative masses of the primary and secondary bodies — the closer they are in size, the more it is a point and not a vague region. Sun-Jupiter has much better defined Trojans than Sun-earth (which really can wander all over the place in a heliocentric orbit at earth radius). So finding stuff in the much more diffuse latter area is more problematic. As is keeping it there.

  4. I’ll have to side with Karl when it comes to the statement that there are more asteroids in Jupiter’s Lagrange points than in the entire asteroid belt.

    However, L4/L5 asteroids have been observed in Neptunian orbits, with a few scientists proposing (wildly if you ask me) that there are more asteroids there than in the entire asteroid belt.

    Gas planets aside, there may be a few valuable asteroids (i.e. metal rich) within Earth’s Lagrange points, but they may be very small compared to what Jupiter (and Neptune) has.

  5. john hare says:

    If the Sun-Earth Trojan points don’t cluster small bodies, then the whole idea goes out the window. Is it theoretically possible that the points are stable enough to be something of an orbital crossroads so that individual explorers can check out multiple asteroids on a single trip? If many asteroids traverse the points during the course of an orbit, it may be possible to use the individual bodies as cyclers to other targets.

    I won’t waste time defending the material mass at the Jupiter Lagrange points. One is that I only read it in a single reference, and two is that they are too far away to be useful anytime soon. The reference served as a trigger for an idea, along with the information that Mars had an asteroid at one of its’ points.

    Is there any way to get a good look at the Sun-Venus points? Are there any other locations where variegated resources might tend to accumulate?

  6. Habitat Hermit says:

    As far as I knew there are only very small and light dust clouds around ESLP4-5 and Cruithne orbits the Sun and is not locked to ESLP4/5.

  7. Rand Simberg says:

    I should also add that in addition to the Sun-earth mass ratio being very large, there are (relatively) major perturbations from (among others) Venus and Jupiter, because of the relative weakness of the earth’s gravity at that distance.

  8. Habitat Hermit says:

    I’d like to advocate retaining the general idea since it still holds as long as one has automated/unmanned collection. Just shift the storage area somewhere else (for example to an orbit higher than GEO).

    It’s a business plan that should close within the next half century (or maybe far earlier) at the current speed of development. One might scale initial operations down far enough that Google Lunar X-Prize winners/contestants could supply a foundation for solutions to capture and collect very small NEOs (if it utilizes solar sails or some kind of M2P2 or that Finnish “guntether” design it could keep working for a long time).

    Something to mull over: making low-tech reentry heatshields out of scrap NEO material (most likely glass or rock) for transporting high-value resources back to Earth.

  9. john hare says:

    I think we can safely call the idea busted. My interest was in locating a large collection of resources that nature (orbital mechanics) had already gathered together. My interest is in finding the buffalo herd rather than herding individual animals to the pen. If we are herding them to the pen though, HEO seems like a better one than L4/5.

    Maybe I’ll try a post on ideas for cheap herding. Should be good for target practice anyway.

  10. Pingback: Mining Asteroids Close To Home « The Four Part Land

  11. MG says:

    Perhaps Deimos or Phobos… not for returning resources to Earth, but for Mars settlement.

  12. PeterH says:

    >> Is it possible that there is a process that concentrates precious metals to parts per hundred, or even pure chunks?

    The metal-carbonyl process comes to mind, presuming the metal is already in metallic form. CO reacts with some metals to produce a gas that is then decomposed by raising the temperature a bit, depositing the metal. Very simple, but I’m uncertain with the processing speed possible.

  13. john hare says:

    I was referring to a natural process that concentrates desirable materials. I’m sure you can do a very good industrial concentrator rig on an asteroid when the opportunity arises, I’m greedy and want to find the gold nuggets instead of the work of placer mining. I believe it possible that when we begin visiting hundreds of the small bodies, some really unusual and valuable discoveries will be made. Discoveries that cannot be predicted with accuracy without on site prospecting.

  14. Scott says:

    Out of curiousity, is it possible to observe the Venusian L4/5 points? If there are large numbers of asteroids there it would at least lend some credence to the possibility that some might be found at the Earth L4/5?

    Sorry I’m a little late with this comment!

  15. Eric Collins says:

    NASA has two probes on their way to the SEL4/5 points. The STEREO A & B (Ahead and Behind) probes have just recently passed quadrature (90 degrees of separation). Unfortunately, the probes will be focused on solar observations, so it’s not clear how much they will be able to tell us about the L4/L5 environment.

  16. Eric Collins says:

    Here’s another article on the STEREO mission to the Lagrange points. This article delves into the possibility of using the probes to search for asteroids at the Lagrange points.

Leave a Reply

Your email address will not be published. Required fields are marked *