You know how there are some beaches in the world where tons of sea glass or other random sea trash washes up, just because the currents and the shape of the land naturally collects it all there? I was wondering if something similar could happen out in space. Certain planets or solar systems where interstellar space trash is more likely to collect into asteroid belts, planetary rings, or just fall to earth. Completely naturally though, it's not being propelled by anything, it just floats there naturally over millions of years. How would that work? Could solar winds and gravity wells have a similar effect as tides and deep-sea currents in this sense?


Yes, absolutely. Every planet has 5 locations around it or near its orbit where the planet's and the star's gravity cancel each other out. These are called Lagrange Points. L1, L2, and L3 are unstable, an object in them is only balanced in a very specific location and a slight nudge will knock it out of the Lagrange Point. L4 and L5 however, are stable; it takes more than a slight nudge to knock them loose.

There's a lot of other situations that fit the bill a little less, but you might still count them. For example there's a large number of bodies, including Pluto, that have ended up in a few specific orbits, guided into them by the influence of Neptune. In short, gravity fields involving 2 or more bodies are really complicated, and you can certainly get situations that are somewhat analogous to currents.

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    $\begingroup$ In your second paragraph, you are talking about orbital resonances. $\endgroup$ – kingledion Sep 8 '18 at 23:59
  • $\begingroup$ Do i remember it right that Jupiter and Mars sustain an asteroid belt between them? $\endgroup$ – Bald Bear Sep 10 '18 at 19:54

Mostly no.

There are currents in liquids and winds in gases, but interplanetary space is very, very, very thin. Interstellar space is even thinner.

So subatomic particles, atoms, molecules, and particles tend to follow ballistic trajectories in outer space.

There are some exceptions. Stars emit "stellar winds" of particles which mostly radiate in straight lines in all directions from the stars.

If astronomical bodies like planets, moons, asteroids, comets, stars, neutron stars, black holes, nebulae, etc. have magnetic fields, those magnetic fields will alter the courses of any passing particles which are electrically charged.

Thus the Earth's magnetic field traps many charged particles in the "solar wind" and keeps them orbiting Earth in the Van Allen Belts, and similar things happen in the magnetic fields of other astronomical bodies.

And the gravity fields of various astronomical bodies can interact with passing particles or objects and bend their courses in various ways. Thus the gravity of large astronomical bodies produces zones that are relatively free of smaller objects, because they are pulled out of those zones over time, and zones that have higher concentration of smaller objects, because they are pulled into those zones over time.

Stars sometimes emit many times as many particles as in a normal stellar wind. The biggest such times are when a supernova explodes and expels a significant proportion of its mass, including heavy elements produced by the supernova, into space. The particles expelled travel outwards for thousands and millions and billions of years, and many collide with interstellar dust and gas particles and push them away from the supernova. Thus a expanding region of very thin interstellar matter is produced around the supernova. As expelled particles and the interstellar particles they hit move outward, the interstellar matter becomes denser at the edge of the wave of matter. And if that wave of matter density encounters another wave of matter density moving outward from another supernova, they may make a region of very dense interstellar matter that collapses under it s own gravity and forms stars and planets.

As for space flotsam ending up on space beaches, that is sort of true since there is very, very thin matter in space and every speck of space dust, asteroid, comet, moon, planet, or star can be considered a moving space beach.

Every object moving through space, be it a speck of space dust or a vast star, hits many smaller objects or particles as it moves through space. Those smaller objects or particles either bounce off or become part of the larger object due to chemical stickiness, magnetism, or gravity. So the object grows larger and larger over the eons as it moves through space, and leaves a tunnel of pure vacuum behind it, though that tunnel gradually becomes as dense as it was before as particles and objects pass through it.

Each day, Earth acquires many tons of space dust as it moves through space.

A micrometeorite is essentially a micrometeoroid that has survived entry through Earth's atmosphere. The size of such a particle ranges from 50 µm to 2 mm. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs).1

An estimated 30,000 ± 20,000 tonnes per year (t/yr)2 of cosmic dust enters the upper atmosphere each year of which less than 10% (2700 ± 1400 t/yr) is estimated to reach the surface as particles.[14] Therefore, the mass of micrometeorites deposited is roughly 50 times higher than that estimated for meteorites, which represent approximately 50 t/yr,[15] and the huge number of particles entering the atmosphere each year (~1017 > 10 µm) suggests that large MM collections contain particles from all dust producing objects in the Solar System including asteroids, comets, and fragments from our Moon and Mars.

Micrometeorites have been found on the seafloors and on land. Places on land to look for micrometeorites include:

Terrestrial sediments also contain micrometeorites. These have been found in samples that:

Have low sedimentation rates such as claystones[22] and hardgrounds[23][24]

Are easily dissolved such as salt deposits[25] and limestones[26]

Have been mass sorted such as heavy mineral concentrates found in deserts[27] and beach sands.[7

So a beach where you might find macroscopic terrestrial flotsam like driftwood can also be a cosmic beach where tiny micrometeorites can be found.

Amateur collectors may find micrometeorites in areas where dirt and dust from a large area has been concentrated, such as from a roof downspout.[28]



And of course Earth also acquires larger space rocks, up to the extremely rare asteroids and comets miles in diameter that could cause extinction events.

So space is mostly too thin a vacuum to have winds or currents in it, but there some situations vaguely resembling currents in space. And every astronomical object functions as a sort of a cosmic beach sweeping up cosmic flotsam.

And you might as well check out Isaac Asimov's novel The Currents of Space, which has an ingenious, though now obsolete, theory for the cause of novas.

It is the second story, by internal chronology, in the "empire" series The Stars Like Dust (1951), The currents of Space (1952), and Pebble in the Sky (1950).


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