Okay, so I'm working on a novel and I'd like to have a dense asteroid field, something akin to the old ESB Hoth field, though it doesn't need to match that exactly. The notion is there is an advanced civilization going into such a dense field to pull out desirable mine-able ores. I'm looking for a plausible explanation for how such a field could form, and persist for at least around 100 years.

So my rough parameters for such a field:

  1. Reasonably dense, with at least building size asteroids, up to city size would be good.
  2. Dense enough that collisions between the medium sized objects are not uncommon.
  3. Not dense enough to immediately form into a planetary body.
  4. It doesn't need to exist for an extended period of time, though 100 years or so would be good, event as short as 5-10 years would be ok

I was thinking something like a collision of dwarf planets or possibly small moons would create such a field, on a short time frame at least. Eventually, I would assume either form a ring, collapse into a moon, or dissipate entirely, but for a while it would be a dense area of debris that would be hazardous to navigate.

So would that be a plausible explanation, or can anyone suggest a way for such a dense asteroid field to exist, even if only for a limited time. Thanks!

Update/Clarification #1: First thanks for the answers so far.

Okay, I can see there being a bit of confusion here. What I'm looking for is a plausible explanation for a dense asteroid field similar to the one seen in the escape from Hoth in Empire Strikes Back. It need not be a long lived phenomenon in astronomical terms ( ie 10-100 years is good ), but would need to exist in such a condition for at least 10 years. It also doesn't need to be huge in terms of area, so something like a few thousand kilometers is fine, but with a minimal size of 10km in height / width / depth. The means of creating such a field can be natural or artificial. In the end I'm looking for a dense Asteroid field for use in a rough and tumble flight scene. Of course, if that is not possible, I can figure out some way to recreate the scene.

Thanks again.

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    $\begingroup$ Why mine asteroids? What resources do you expect that will be available on an asteroid that are not available elsewhere? $\endgroup$
    – Gimelist
    Mar 11, 2019 at 8:57
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    $\begingroup$ Why not? I'd be thinking asteroids would be a useful source of heavier metals, and for an interstellar capable race, gathering those resources outside of a major gravity well would save a fair bit of energy over trying to get them off a planet. Granted that doesn't necessitate going into a dangerous asteroid field, unless all of the easier to mine asteroids were already tapped out. $\endgroup$
    – Tov Versh
    Mar 11, 2019 at 14:06
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    $\begingroup$ "Reasonably dense" is a very relative term. "Dense" in astrophysics terms makes a finely made angel cake look like a solid rock by comparison. Density of Saturn's B-ring is estimated to be somewhere around 0.02g/cm^3. The asteroid belt for us weighs in at around 0.1g/km^3 (note: unit change there. 0.0000000000000001 g/km^3). I'm assuming you're looking somewhere inbetween? $\endgroup$
    – Cort Ammon
    Mar 11, 2019 at 15:34
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    $\begingroup$ Also, my expectation is that a society which is sufficiently advanced to take advantage of a major mining operation like this on a mere 10 year timescale would have little trouble avoiding collisions. They'd have more than enough propellant to spare. $\endgroup$
    – Cort Ammon
    Mar 11, 2019 at 15:36

5 Answers 5


You USE a planetary ring system for this. A planetary ring is stable across geological timescales by being well INSIDE the planet's Roche limit, therefore preventing itself from collapsing back into a moon. Planetary ring system, for example, Saturn's ring system, is almost dense enough so that you can see small chunks of ice from the size of sand grains all the way up the size of houses. Saturn and part of its ring

So if a gas giant large enough to have a large Roche limit radius, and one of its major moons fell inside such limit due to some reason like orbital perturbation or decay, it would disintegrate due to the main body's tidal forces, and the resulting ring system would be both thick enough for your average sci-fi asteroid thicket, and stable enough to last for GEOLOGICAL timescales--Saturn's ring is believed to have existed for more than 100 million years.

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    $\begingroup$ Note that if it is like Saturn, most fragments will be small: fragments twice as big are also twice as rare. $\endgroup$
    – Eth
    Mar 11, 2019 at 12:14
  • $\begingroup$ Thanks! I'll be a bit picky and say I'm looking for a sense of a dense asteroid field. A ring like Saturn's has width but not depth. So you could just ride above it in safety and pop in and snag anything useful. That is good and practical, but doesn't have the feel I'm going for. That said, if say we crashed two substantially sized moons together inside the roche limit, could we expect a dense asteroid field to exist for a period of time before a full ring would form? How long would it be reasonable to assume the density would last before evening out? $\endgroup$
    – Tov Versh
    Mar 11, 2019 at 14:15
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    $\begingroup$ Hi, John. Is this an actual picture taken from inside Saturn's rings, and if so, can you please attribute it to the original source? Thanks. $\endgroup$
    – HDE 226868
    Mar 11, 2019 at 15:00
  • $\begingroup$ Hm, if I steered my ship into a circular orbit within saturns rings, how many particles (of any size) would I see with my naked eye, in average? $\endgroup$
    – Karl
    Mar 12, 2019 at 21:46

Your civilization made the impact field. It is the advanced civilization equivalent of strip mining.

  1. Blow up planet using advanced tech (Death Star will do fine).

  2. Blown up planet exposes delectable planet guts. All that good stuff down deep.

  3. Collect good stuff

  4. Danger - it will be hot.

  5. Danger - it will be trying to coalesce back into a planet

This is a much hotter and more action packed asteroid field than the duddy old Kuiper belt or some ice collection ring. Good heavy globs of metal will be floating around, glowing hot. Plus when you make it there is the bonus sound, like millions of voices suddenly cried out in terror and were suddenly silenced.

  • $\begingroup$ Thanks, but not quite what I'm looking for, but let's play with it a little. Let's say we did Alderan some planetary body. We'd need to look for a sweet spot in energy used, too much and everything either vaporizes or gets blasted out faster than escape velocity, too little and it all collapses back into a planet almost immediately. If we were dealing with something around the size of a smallish moon, what would be the longest you could expect an asteroid field of debris to exist before collapsing back into a single mass? $\endgroup$
    – Tov Versh
    Mar 11, 2019 at 14:20
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    $\begingroup$ @TovVersh Not everything will have the same velocity. You'll have some distribution of velocities. The portion which is thrown out simply goes away, and what you are left with are the slower objects that meet your needs. $\endgroup$
    – Cort Ammon
    Mar 11, 2019 at 15:24
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    $\begingroup$ Also stuff might oscillate / unstably orbit around a common center or remnant core chunk. $\endgroup$
    – Willk
    Mar 11, 2019 at 19:10
  • $\begingroup$ Good points. I would assume that if this was done on a smaller mass, it may take a while for it to collapse back down into a single body, since there is less mass to pull everything back together quickly, though too little mass would mean more of it floating away. Perhaps a collision of two large asteroids would be good to cause this. If they collided such that they maintained two rotating centers of mass that would take more time to stabilize the whole mass into a single body. $\endgroup$
    – Tov Versh
    Mar 11, 2019 at 23:41

The Perfect Mining Prospect: Proto-Planetary Disks

A widely accepted theory of planetary formation called the nebular hypothesis states that during a star's first 100,000 years or so, the surrounding dust compresses into a disk and starts accumulating into clumps. Once these planetesimals grow to a few kilometers, they start directly gravitating together instead of just bumping into each other. As larger proto-planets form, lots of the planetesimals get ejected from the system.

A young star system transitioning from planetesimals to proto-planets would be the absolutely ideal place for interstellar mining. For thousands of years, all of the orbiting mass of the system would be in nice, soft, bite-sized pieces, and before much of it is lost to deep space. It would be at the tipping point between large, quick hauls and minimal gravity wells to escape.

Such a chaotic landscape would be highly varied; some areas could be more safely exploited, while some particularly dense regions would appeal to daredevil miners willing to take risks for a big payout.

If you have interstellar travel, proto-planetary disks are where you go to mine. They also happen to be the best place to find tons of cool rock chunks slamming into each other.

  • $\begingroup$ Oh, I like this one. That is certainly something I can work with. Good from the prospect of having things to mine, and an otherwise dangerous environment. Also not a friendly place, so you'd only want to have a basic mining station rather than a larger facility. All of that pulls together nicely with what I'm looking for. $\endgroup$
    – Tov Versh
    Mar 12, 2019 at 6:49

Beware of tightly packed asteroid belts, especially if they're mineral rich and safely floating by your home world's orbit within easy reach. They are traps! Lures to tempt you up into the darkness where your technology is more easily measured and threat assessed.

The Old Ones, who rule the inner spirals of our galaxy, know that we are out here. They know that intelligent life is the natural goal of the universe and that it erupts practically everywhere beyond their jealously guarded domain. They know that inevitably a greater intelligence will rise to threaten them. It is only the when and from where that is in question. The certainty that it will be is absolutely certain.

But as others here have explained, space is big and mostly empty. It is beyond even their vast power to monitor all that is. Deep time and deep space shroud us from their view. The fraction of a million years needed to rise from the caves to the stars is a blink compared to the galactic expanse which must be watched. From their point of view, the forest is too large and the prey too few.

So like any good hunter, the Old Ones lay traps full of tempting morsels.

It is child's play for them to cherry pick each solar system's oort cloud and assemble a mineral treasure trove as bait. Then with only a small exertion in stellar engineering, they set it all in motion. Through their design, the field can orbit the system's primary temptingly close to the potentially fertile worlds yet distant enough that those worlds' gravity wells neither disrupt nor steal from the asteroid field. The trap can then remain stable for the life of it's sun, serving as a lure to any star faring race which might rise from or even just visit the system's planets.

And deep in the heart of that treasure trove, on an asteroid which is obviously richer than all of the others combined, the trigger awaits to be sprung...

When the first gram of its riches are removed, the system's sun goes supernova... eliminating another threat to the Old One's rule.


Oort Cloud

Could it be that the civilization has a refinery orbiting a star while the actual mining happens in the Oort Cloud. Having the refinery in close to the center of the star system (at least not close to the edge of the Oort cloud) would mean that mining operations could happen anywhere in the Oort cloud would just head towards the center of the system to get it processed.

The Oort cloud could / would have as dense an asteroid belt as you want or as rich. Since not much is known about the Oort cloud currently you could hand waive a lot to fit your requirements.

The Oort cloud would be large enough to warrant the construction and maintenance of a processing facility (close to the sun maybe to use solar energy for refinement of ore).

As for collisions, I was told once (no actual proof behind it sorry) that some of the comets that come into the solar system were caused by collisions in the Oort cloud.

  • $\begingroup$ The farther you go from a parent body, the harder it is to have a dense field - due to the square-cube law. Oort clouds are so thin, hitting anything there by luck is harder than winning all lotteris on Earth combined. And comets are thrown into lower perigees due to gravitational pulls, not impacts. $\endgroup$ Mar 12, 2019 at 0:09
  • $\begingroup$ That would be my thought as well, consider how hard it was for the New Horizon team to find another object to flyby after Pluto. There may be a lot out in the Oort cloud but that is over an exceedingly large area. There is nothing approaching the level of density I'm looking for. $\endgroup$
    – Tov Versh
    Mar 12, 2019 at 0:20

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