An extra-solar object slightly larger than the Earth is pointing towards Jupiter, its trajectory briefly crossed the Solar system. But after a very close fly-by with Jupiter the object it is crushed to pieces by the gravitational field of the gas giant. Then some fragments escape the solar system and some remain lingering around. Fragments of unknown metamorphic materials, created under very high pressure start wandering around and on Earth the race to mine them quickly heaths up.

What I am wondering is how from Earth people can understand there is something really valuable there, elements like Gold or Platinum are rare, but it is still cheaper to mine them on Earth than in space. I am also wondering how can they detect and track these new asteroids. I though about new crystals so dense that they can scatter around the gamma radiation coming from the cosmic rays. I also thought about big explosions created by tiny asteroids falling on Mars showing how dense they are. What else?


The description of the trajectory of the object was modified to avoid off topic answers like the one of @John Dallman

Regarding the comments of @AlexP and @Sean OConnor It is true that when the pressure is released the cristalline structure is unstable, but materials like diamonds and marble can last for a very long time. Could there be other materials in the Earth core or close to it that are so heavy that the convective currents of the mantle cannot pull them up and we never saw them? We don't know.

Regarding @Tom answer. Who cares. Yes I know, thanks to the modern over-spectacularised journalism there will be a lot of people freaking out, mainly American journalists I guess. But after the event if there is money to be made you can bet that there will be people jumping at the opportunity, no matter what could be the looming danger. So what would happen before the fly-by is not meant to follow the plot of the usual hollywood style disaster movie.

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    $\begingroup$ You don't realize it, but this question is trivially answered with some research into astronomical spectroscopy, which is how we analyze the composition of everything from moons to stars. In other words, we already do this today. BTW, the help center specifically states, "To prevent your question from being flagged and possibly removed, avoid asking subjective questions where your answer is provided along with the question, and you expect more answers." $\endgroup$
    – JBH
    Commented May 29, 2022 at 20:10
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    $\begingroup$ I'm not missing a point. You didn't mention anything about needing to know the specific physical structure of the object in your question (I can't read your mind). In fact, your question is, as stated, "how from Earth people can understand there is something really valuable there?" Who cares what shape it takes or if it's filled with holes like swiss cheese? But, if that's important, then I give you deep space radar. All of this has already been solved. $\endgroup$
    – JBH
    Commented May 29, 2022 at 20:34
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    $\begingroup$ From the help center, "General guidelines for all questions: Should include research: What ideas have you considered, or what information have you already looked at or failed to find?" What I'm pointing out is that there are already answers easily found on Google. If you don't like them, you need to explain why they don't meet your needs. To hedge against a common response, "I want something new" and "it's not cool enough" aren't reasons to ask. $\endgroup$
    – JBH
    Commented May 29, 2022 at 20:38
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    $\begingroup$ BTW, if by "physical structure" you meant the molecular assembly of atoms and not the dimensions of the asteroid, that's IMO unimportant as it assumes, e.g., that an ultra-dense iron can actually exist that wouldn't be identified by spectrocopy. If you want an answer to that you need to specifically identify the chemical composition for us to work with. Finally, I removed the reality-check tag because you're not using it correctly (please read the tag wikis before using them). I added asteroids and detection because that's what you're asking about. $\endgroup$
    – JBH
    Commented May 29, 2022 at 20:40
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    $\begingroup$ "Fragments of unknown metamorphic materials, created under very high pressure"... and which by a miraculous miracle are also stable at normal pressures. $\endgroup$
    – AlexP
    Commented May 29, 2022 at 20:44

2 Answers 2


Holy sh!t -- a planet the size of Earth almost crashed into Jupiter!

Let's start by appealing to basic common sense: if an object the size of a planet enters our solar system, it will immediately have the attention of every human on Earth. The big question will be: is that thing going to hit the Earth and destroy all life, or cause some other kind of collision that will annihilate terrestrial life? Will we lose our Moon?! How will our own orbit be affected, and what will be the new length of a year? What will we name the new month, or which month will we give up? These are all very realistic possibilities when the object is the size of a planet.

Everything that can be used to observe a space object will be pointed directly at this rogue planet -- let's call it "Sidney"1 -- for the entirety of its voyage through our system. Teams of scientists will observe Sidney in shifts around the clock -- assuming that any of them can be pried away from the 'scope in the first place.

What will they be looking for? Most important will be clues about Sidney's mass, because its position, mass, and velocity are the unknown factors in the equations that tell us about Sidney's future movement. Sidney's interactions with other bodies in our system will help us refine our estimates of Sidney's mass and composition. By the time of Sidney's near-slap with Jupiter, we will probably have been studying the rogue planet for months.

You say that this near-miss somehow compresses Sidney while also breaking off chunks of material, and that Sidney continues out of our solar system while the chunks remain.

This near-miss will not be a surprise to anyone. If something the size of Earth is on a collision course with Jupiter, we will be able to predict that fact quite easily. Planets don't fly around like cars in a drive-by shooting, popping out the shadows for some quick action and then peeling off into the darkness. The distances in space are, well, astronomical, so unless Sidney is careening through space at relativistic speeds (which is almost certainly impossible), we will have weeks or months to recognize that there is a significant chance that Sidney will collide with Jupiter. If that were to happen, the radiation created by that impact would probably kill everyone on Earth and strip the atmosphere from our planet.

This means that everybody and their dog will be watching the near-miss live on TV when it happens, because everybody will know that a collision will kill everybody on Earth within something like 15 minutes.

Once it becomes clear that this event is a near-miss instead of a life-annihilating planetary explosion, everybody will let out a huge sigh of relief. Most of humanity will be psychologically incapacitated as they process the emotional fallout of avoiding immediate, permanent extinction.

The scientists, though, will barely blink, because they know the story is not over. These are the folks who will notice that Sidney has left us some gifts, in the form of big chunks of material that were ejected, presumably as a result of Jupiter's titanic tidal tyranny.

By analyzing the trajectories of these chunks, we will be able to estimate their mass. This is how we will know they are extra-massive. This interaction will also probably produce lots of information for the spectroscopy people, and I bet some of that will give us clues as to the chemical composition of these chunks. And remember: everybody on Earth has had their eyes glued to this near-miss for the duration because it had the potential to immediately end our civilization. So we can safely assume that we captured every iota of information that could be gleaned from this near-miss event.

That is how we will know these chunks are unusually valuable.

Oh, also: lots of human society may possibly have collapsed into anarchy when a large chunk of the population concluded that Sidney was, one way or another, going to end the story of Earth within a few weeks. So that will have an impact on how and when humanity confronts the practical question of how to mine Sidney's legacy. I almost hesitate to mention it.

1 After the late, great Sidney Poitier, who played the unexpected dinner guest in Guess Who's Coming to Dinner.


The detection is much less of a problem than the orbital dynamics, but those can be managed.

Interstellar object!

Interstellar objects are very, very interesting. There are huge amounts of theory about the formation of solar systems and planets, and getting to examine samples from other star systems could confirm or disprove a lot. So when one this big is spotted, it will be examined as much as possible. Unless space travel is highly developed in your setting, an expedition to land on it won't be practical, because it's fallen into the solar system from a long way off, and will be moving really fast.

You say that you want its core to escape the solar system, and that will require that it's moving faster than solar escape velocity. That means Jupiter, which is much lighter than the Sun, cannot capture it. But if its course takes it close to Jupiter, we can estimate its mass from the effect of its gravity on the orbits of Jupiter's moons. While preparing to observe that, astronomers notice that it will pass very close to Jupiter, within the Roche limit, and may thus disintegrate.

It does that, as per your scenario, and some of the fragments hit moons of Jupiter. The rest of them go flying out of the system, about as fast as they came in. Catching up to them will be hard.

Sample retrieval!

There are chunks of the interstellar object on one or more moons of Jupiter. Those will be hugely scientifically valuable, on at least two grounds:

  • Interstellar object!
  • Its effects on the orbits of Jupiter's moons has told us that the object had an implausibly high mass.

Plans will be made to get samples of the fragments ASAP. Pieces will be brought back to Earth. And if the metamaterials survived impact with a moon, your detection has succeeded.

Unworkable ideas

If the object comes in unexpectedly slowly, and gets captured into orbit around the Sun, or around Jupiter, there's no way to give it enough energy to escape the system later on, unless it has a seriously miraculous engine on board. If you want most of it to leave the system, it needs to stay above system escape velocity the whole time. That means that fragments of it won't stay in the system unless they hit something. Jupiter's moons are the obvious thing to use.

  • $\begingroup$ I definitely think it's impossible for OP's scenario to avoid destroying some of Jupiter's moons. Maybe that's how the chunks get thrown off -- collision with Io or somesuch. $\endgroup$
    – Tom
    Commented May 29, 2022 at 22:24

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