# Can there be a planet with no dust?

What restrictions this planet must have to make it possible?

Planet can have any size, be made of any material

A human must be able to land in it and observe it, dust added to the planet from the human's clothes or equipment may compromise the no-dust characteristic of the planet but it must be dust-less before then.

Edit: Dust in the definition of fine, dry powder consisting of tiny particles of earth or waste matter lying on the ground or on surfaces or carried in the air.

• How fanciful is your universe? Maybe the Interstellar Empire of Purity built a planet-sized air filtration system to remove all dust from the atmosphere. – user45623 Jan 24 '17 at 3:04
• a planet fully covered in water? or glassed by a series of nuclear explosions? A giant ball of iron that solidifed in one block? – njzk2 Jan 24 '17 at 3:29
• Dust isn't all man made... – user6760 Jan 24 '17 at 4:52
• What is the point of that restriction? What kind of story are you trying to write? It's kind of impossible to have a planet with no dust that you could land on, but maybe your story can work with a lesser restriction? – Luaan Jan 24 '17 at 9:34
• Please do not change the scope of your question - this is considered bad behavior on Stack Exchange. Of course, you can (and probably should) ask a follow-up question with your changed concept. I will roll back your last edit. You will still be able to access it via edit history and use to create new question. – Mołot Jan 24 '17 at 10:45

No, it's impossible under your requirements. Rocky planets either have atmosphere worth speaking of, or they don't.

If there is atmosphere, there will be some wind. With wind comes erosion. And with erosion comes dust.

Without atmosphere, look at our moon. Meteorite impacts can and do create a lot of dust all right.

The only exception would be an ocean planet (not necessarily water ocean) with no land at all. That's a bit of stretching "can land on it", but with no exposed rock to erode, and with meteorites sinking, you don't have material to create dust. Minuscule amounts from meteorites impacting ocean would sink anyway.

For a high spin rogue planet, it's hardly possible, either. Such planets have to come from somewhere. Probably star system, and that means dust. And if spinning is high enough to throw dust from surface into the space, it'll be high enough to throw away your astronauts, too. So no landing. And I doubt such planet could even exist, survive. So, the dust is here, and is going to stay.

For the amounts of dust, see answer by Cort Ammon.

• Comments are not for extended discussion; this conversation has been moved to chat. – Serban Tanasa Jan 24 '17 at 16:54
• "but with no exposed rock to erode, and with meteorites sinking, you don't have material to create dust." There will be sand at the bottom from the currents, though. This may or may not count as dust; I'd imagine some of it would be quite fine. – jpmc26 Jan 24 '17 at 19:13
• Would erosion still be possible on so-called "diamond planets"? – Trixie Wolf Jan 25 '17 at 12:11
• @TrixieWolf you only need one loose diamond rock to start erosion... Sooner or later, it will happen. Not all meteorites will burn in atmosphere. One hit and it'll go. – Mołot Jan 25 '17 at 12:57
• @TrixieWolf remember that diamond might be the hardest thing, it's not indestructible. At orbital velocities, a meteor of talc could do significant damage purely through mass and velocity edging out the strength of diamond. – Nick T Jan 26 '17 at 17:26

It's really not possible to not have dust. If you have an atmosphere, erosion will create dust. If you have no atmosphere, micrometeorite impacts will create dust, and being a planet, it will have enough gravity to pull some of that material back to the surface.

One solution might be a completely liquid-covered planet. The liquid could capture the dust, causing it to sink to the "ocean" floor.

Of course, the definition of "having dust" is tricky. That's why we have different grades of clean rooms, each having a slightly different definition of dust. An ISO 8 clean room (also known as a Class 100,000 clean room) is concerned with particles of .5μm or greater. As you go towards cleaner rooms, such as an ISO 3 (aka a Class 1 clean room), the definition shifts to particles greater than .1μm. Also worth noting is the number of particles. While an ISO 9 clean room (aka "room air," no special precautions) may have 35 million particles (0.5μm or greater) per cubic meter, a ISO 1 may only have 10 particles (0.1μm or greater).

These varying standards all share one thing in common: they recognize that particles are everywhere. There is no clean room standard for "no particles."

No.

Never mind erosion, there a constant flow of dust falling from space.

The Cosmic Dust in the Terrestrial Atmosphere (CODITA) project was set up to accurately measure just how much falls every day. Quoting that site:

Observations of the zodiacal cloud and measurements by a dust detector on a satellite indicate a daily input of 100 – 300 tons. These estimates agree with the accumulation rates of elements such as iridium and osmium in polar ice cores and deep-sea sediments (these elements are enhanced in cosmic dust compared to the earth’s crust). In contrast, measurements in the middle atmosphere indicate that the daily input is only 3 - 50 tonnes.

Unless your planetary system is vastly different from ours, there will be (doing the math averaging it over earth's entire surface) about 0.2 μg/m2 per day, or in understandable units, about 1mm deep every 10,000 (Earth) years.

Assuming the current rate for all of Earth's 4.5B year history, that's a cumulative total of 450 meters deep. Of course, the younger earth would have received a vastly higher rate that would diminish is it cleared its own orbital path of dust.

OK it's not much, but it's constant. Even a world glazed by extreme heat would still have dust.

• Nice answer! The "/day" is assuming 24-hour days though. Depending on the rotation speed of the planet, the tonnage can vary wildly. – Mathieu Guindon Jan 25 '17 at 3:00
• @Mat'sMug -- The rotation doesn't matter so much. If you divided earth's numbers by 86400 to get the per-second flux, or multiply it by the 365.2422, that would be relatively constant. If the rotation was locked to the revolution, like Mercury, perhaps the distribution of dust would be affected by the sweep along the orbit and the static weather patterns. – Dave X Jan 25 '17 at 16:06
• @DaveX huh, I counted 100-300 tons per 24-hour period. If a day on that planet is 240 hours, then wouldn't that make it 1000-3000 tons per [that planet's] day? My point was that "day" is an ambiguous measurement when you're talking about different planets. – Mathieu Guindon Jan 25 '17 at 16:09
• I agree. flux per unit time would be constant, but flux tonnage per day_{planet} would vary as the length of the day changes. – Dave X Jan 25 '17 at 19:19

How about a planet that is entirely covered by a single lifeform with the consistency of a super thick Jello?

Any meteor impacts would be absorbed into the lifeform (maybe it even feeds on these). Dust on the surface would be sensed by the lifeform because it would be blocking light and the lifeform would pull it away from it's surface.

I guess technically you would not be landing on the planet itself (as the planet surface would be several meters below the surface of the lifeform), but those landing wouldn't know that when they landed.

You could even add a tension point to the story when they realize their ship is slowly sinking.

• Solaris, hm? (but no, iirc it had at least one shore, and likely dust there - in the novel, at least :) – Michael Schumacher Jan 24 '17 at 20:57
• "Jello, World!" – Pierre Arlaud Jan 25 '17 at 15:28

Yes. Take Mercury, move it inwards to the point the surface is molten.

No dust.

Such a planet will not have the longest of lifespans, though.

• "A human must be able to land in it [...]" – Emilio M Bumachar Jan 24 '17 at 10:09
• You can float a pretty heavy boat in mercury. – aslum Jan 24 '17 at 14:06
• @EmilioMBumachar You can probably land in such a planet... once. – Miguel Bartelsman Jan 24 '17 at 22:53
• @SPavel Stuff will collect on the water but once it's in the water you wouldn't call it dust, especially if you use the OP definition of dust. – Loren Pechtel Jan 24 '17 at 23:09
• @EmilioMBumachar He didn't say an unprotected human. There's a surface, make the bottom of your craft a boat, built of materials that can take the heat. – Loren Pechtel Jan 24 '17 at 23:10

So start with a planet that is mostly made of a metal with a low melting point, say lead. It's set close enough to a star that during the day the surface becomes liquid, but it also has a low rotation speed so during the night it's cold enough that sufficient heat leaks out and it becomes a solid again. Any space dust or meteors that impact during the night get integrated into the surface when it melts, and are trapped when it solidifies again.

• I don’t think the lead would be found on the surface. Even if the planet were solid lead, the infalling dust would float on top. – JDługosz Jan 25 '17 at 2:49
• But that would be embedded in the solidified lead. In a sense, stone is 'solid lava trapping dust'. – cst1992 Jan 25 '17 at 13:16
• "Any space dust or meteors that impact during the night get integrated into the surface when it melts, and are trapped when it solidifies again." - I was under the impression that rock had lower density than lead. That is indeed the case. Your space dust would float on the surface, not sink to the middle. In fact, Earth is such a metal planet, with tons of molten dust on its surface, then some molten and frozen dust, then a tiny bit of dust that turned into actual dust in the meantime. – John Dvorak Jan 25 '17 at 15:39
• @JanDvorak I never suggested that it would sink to the center. If you take a piece of wood, float it on top of water, and then freeze the water, then the wood is pretty trapped. The idea is that the dust will land, float on the surface as long as it is less dense than lead, get trapped in the lead when it hardens again, and then it is no longer free floating dust. – AndyD273 Jan 25 '17 at 15:45
• It might be a good idea to place your metal ball into an environment that does this surface tearing away continuously – John Dvorak Jan 25 '17 at 16:01

It's certainly possible if you live on a mudball.

If the entire planet is constantly receiving rain, let's say 30 or 40% of the time, then I would expect any stray dust particles would very, very quickly be captured by all the free water moving around.

Now, in order to do this, you would have to have a very active rain cycle which would require a lot of energy. Thus I would expect this entire planet to be very hot and tropical and possibly only habitable away from the equator. It may even be that the energy required is simply too high to support life. I don't know how I would run the numbers on that. But it certainly seems plausible.

• I was thinking about perpetual rain, but then was considering whether clouds always require microscopic dust particles to form... – Michael Jan 25 '17 at 19:18

Naturally occurring, no. See the other excellent answers from Molot or Cort Ammon.

For non-natural, consider an airless world that is heated to molten and then cooled to remove all initial dust. Then orbit it with satellites that monitor for micrometeorite impacts. When one is detected, the satellites use heating lasers to melt the area.

There are myriad variations on this theme, with varying degrees of plausiblity.

• depending on the material, melting impacts may actually create some dust, so you have to melt the whole planet again. Cook it from orbit -- it's the only way to be sure :) – Florian Castellane Jan 24 '17 at 12:51

How about an ice planet with highly eccentric orbit. A bit like pluto, but a real planet and slightly closer to the sun so that the surface melts during summer time, while the surface freezes and atmosphere collapses during winter.

This could cause dust to settle quite quickly into the water and get contained in the ice. It would have a surface you can walk on when frozen.

The biology of a being adapted to live on such a planet could be quite interesting - for example, perhaps they reproduce in the liquid water during the brief summer, hibernate over the winter and live on the ice surface during spring. A human visit during the winter could leave dust pollution that the organisms have never seen before on the surface, even if they are used to dust in the water.

Of course this still has the drawbacks that there would be some dust falling from the sky, either from cosmic dust or meteorites. It would get absorbed during next summer, but in between the planet wouldn't be dustless.

A planet with no life and no friction helps eliminate the creation of dust. The planet would also have to dodge asteroids, comets, any other space matter, etc.

Plants must create pollen which is dust. So absolutely no plants. Without the photosynthesis of plants, there cannot be life of any kind. With no friction, objects rubbing against each other should not cause erosion and then dust.

• Obviously plants can evolve without pollen. It first appears in the Devonian; plants where around for quite a while before. – Antzi Jan 24 '17 at 8:33
• @PatrickTrentin Plants are what makes the CO2 we exhale into breathable oxygen. You could have factories that creates O2 from C02. But without an infinite power source, the factories eventually stop. – Just Someone Jan 24 '17 at 13:17
• @PatrickTrentin I stand corrected. – Just Someone Jan 24 '17 at 13:30
• The "without photosynthesis of the plants, there cannot be life of any kind" point is wrong. Cyanobacteria are responsible for the Great Oxygenation Event, 2.3 billion years ago - the first plants date some 470 million years, well into the Paleoproterozoic: both oxygen and life were there well before any plant was around. – Mathieu Guindon Jan 25 '17 at 2:49
• Hey, there may be life that survives on non-oxygen as well. Remember this is another world right? – NZKshatriya Jan 25 '17 at 18:26

A near-miss would be to have a natural satellite (moon) of a large planet, where the moon is just within the Roche limit of the larger body. The local gravity on the planet-facing side will slightly favor the planet, and so dust and pebbles will be pulled away. You can't have it very far inside this limit though, because the only thing holding the moon together at that point are electromagnetic bonds -- tidal forces are trying to tear it apart, albeit weakly if it's just barely within the limit.

## Ice Planet

Depending on what you actually define as dust you can always have an ice planet.
Any other kind of planet will create "dust" as it is hit by asteroids or its own crust moves.

Any planet needs to be geological active in its lifetime so that implies that any natural planet will have dust, but you can always have a smooth and geologically dead man-made planet that is protected from asteroids. Maybe some advanced species made this planet to prove it was possible.

• How about a Dyson sphere with external atmosphere, and androids with Dyson vacuums keeping the outside dustless? – NZKshatriya Jan 25 '17 at 18:25
• @NZKshatriya I don't know if that would count as a planet but it is more realistic than a man-made planet. :) – user31746 Jan 25 '17 at 18:56
• Well....planetoid? (shut up firefox, it is a word) – NZKshatriya Jan 25 '17 at 19:43
• Why wouldn't water dust AKA snow powder count as dust on the ice planet? – hyde Jan 25 '17 at 19:44
• @hyde Define dust: fine, dry powder consisting of tiny particles of earth or waste matter lying on the ground or on surfaces or carried in the air. Snow isn't dry, so depending on what OP actually wants an ice planet might or might not work for him. – user31746 Jan 26 '17 at 10:14

Dust in the definition of fine, dry powder consisting of tiny particles of earth or waste matter lying on the ground or on surfaces or carried in the air.

Well, if your planet is 100% covered with liquid (no dry particles on the ground) and have no atmosphere(no particles in air), by this definition there would be no dust.

• And does it add anything to answers posted by me or Cort Ammon about 8 hours ago? – Mołot Jan 24 '17 at 9:00
• How do you make a planet that's 100% covered with liquid with no atmosphere? That liquid is going to evaporate :) – Luaan Jan 24 '17 at 9:32
• 100% covered with freshwater seems to be sufficient. Water droplets (clouds) aren't dust. Earth's oceans have become salty because of the erosion of continents over geological time. On a planet where there is no dry ground, that won't happen. The water will stay fresh and not create significant salt dust when ocean spray evaporates. Of course this is not no dust just very low dust in the atmosphere. And probably plenty of sediment (= "dust" but in water). – nigel222 Jan 24 '17 at 11:05
• @nigel222 Water droplets aren't dust - but surely ice is. And the ocean floor still gets dusty without rivers - it's just that it's utterly dominated by erosion from the continents on Earth, so it's not very important here. But in a world without continents, you'd still get visible erosion just from the oceans over the ages. And if the planet is tectonically active, plenty more being injected from the volcanoes, hydrothermal vents, created at the interfaces of tectonic plates etc. The oceans of Earth are kept salty through erosion, but that only reclaims the salts captured in continents. – Luaan Jan 24 '17 at 13:22

The best bet for a planet with no dust that resembles a rock planet would be something with an absolutely outrageous magnetic field... When I say outrageous I mean something with a stronger magnetic field than stars - maybe black hole - by... I honestly don't know how much. The idea is that said planet would induce a charge on asteroids and simply push them away. All dust would either be pushed away from the planet or glued there. With proper magnetic shielding a human would probably last for a couple seconds there before dying. With this in mind it would be possible to get extremely unlucky and crash on this planet. perhaps with a bit of luck you wouldn't die on impact because magic?

That being said this is all a massive stretch and unless said planet turns out to be some sort of BS quantum super weapon no one will believe the set up. Simply put a planet without dust doesn't make sense.

Now a planet with special dust that doesn't exhibit dust like properties, that's just as dumb, but could be made "believable" using nano-bots or some other syfy hail marry. For example the dust could all be magnetic and simply not leave the ground at any point in time. Nano bots could just fix the dust. Maybe the atmosphere is definitely not magic and dissolves the dust because acid. Perhaps due to math the planet just doesn't have wind.

My poorly thought out point is that this could work, but not without some extreme effort; your dustless planet is going to be super special.

• Stars and black holes... are you mixing up magnetic field with gravity? If that's the case then it doesn't jive, because gravity is tied to mass; a black hole has massive gravity because it's, well, massive. So if the planet has the mass of a black hole, then it has the gravity of a black hole - and if that's the case... in my books that makes it a black hole, not a planet. So yeah, massive stretch ;-) – Mathieu Guindon Jan 25 '17 at 2:56
• @mat's mug no I mean magnetism. You see gravity is a pathetically weak force when compared to magnetism. In fact magnetism is why dust sticks to cars moving at 75mph. If you want to conquer dust with a planet with reasonable mass, you look to magnetism to do it for you. That being said the composition of the dust on the planet has to be right for this to work and the magnetic field produced by Said planet would have to be unreasonable to knock away meteors and the like - or turn most collisions near perfectly inelastic. That's why I mentioned that it might be a super weapon. – user32463 Jan 26 '17 at 4:21

Yes - if you made the planet resistant enough to retaining dust, you can then find a way to get rid of whatever dust begins to accumulate.

Let's start by constructing the planet from an Omniphobic material, or something fairly close to that caliber. Next, you have the options of:

• Drain away dust into the planet itself. Perhaps it's a conveniently mountainous planet where there are holes or burrows at the bottom of every valley, perhaps created by lifeforms. Perhaps it's a highly active planet which has regular earthquakes shaking all the dust down into the pits and valleys, where average conditions melt or otherwise absorb whatever dust collects.

• Blast away dust at regular intervals. Perhaps the planet passes through a region which blasts off or melts all its dust, or experiences a strong kind of solar wind which carries it away. Though the solar wind would need to have an opposite magnetic charge to the planet itself, and so ensure it really does just carry away all loose items without depositing anything. Or perhaps there's a sentient species living within the planet who is extremely dust-phobic, and regularly blasts away all particles from outside or within.

• Consume the loose dust. Perhaps there's a creature which actively searches out and eats dust particles, or else one or more vectors who gather it and consolidate it for some reason. Perhaps this is the extreme outcome of a micro-organism which uses the dust to build their own homes or even civilizations. Maybe there are periodic storms where water or some kind of acid absorbs or bonds with the dust.

• Spin the planet. Now here's a novel solution. Spin things until other stuff falls off. Of course you'd need an extreme spin to overcome gravity on every loose particle... or else if the planet happened to be manufactured by another species, perhaps they would have a means to move only the top 'skin' of the planet. For thirty seconds the entire surface accelerates in the opposite direction of the planet's spin, and then resumes its regular velocity. Implausible - yet possible.

A software planet can have no dust. I know this is hard to accept because we live in a supposed reality where everything is made of atoms.

There however is the possibility that there can be a planet in a universe across a black hole, where everything is not made of atoms. Everything is generated via something like a computer generated bits and bytes. Not necessarily with electricity, but with just energy. Such a planet can exist without any dust on it. [edit: A human can definitely land on such a planet. When you have forces like gravity, rays like X rays and have the earth floating on god-knows-what matter, why is it so hard to imagine a planet of energy where the forces are such that it can support the weight of a human and a spaceship and yet be dust free (until the human lands)?]

Another place our kind of planet can exist without dust, is in our imagination. Like the Matrix.

• "A human must be able to land on it." – Beanluc Jan 24 '17 at 18:47
• @Beanluc who's to say there aren't humans on the other side of the black hole too? – dejongbrent Jan 25 '17 at 3:34
• There’s not really any such thing as “just energy” in physics. For example, electromagnetic radiation might be considered “just energy,” but it can (more) accurately be conceptualized as massless particles. Can you be a little more rigorous about what particles (massless or otherwise) or such things would make up this “planet of energy”? – Obie 2.0 Jan 26 '17 at 11:19
• That's the physics you know of. I'm talking of what we don't know. I've always believed that anything we imagine is actually possible, because our imagination is only limited by the possibilities in the universe. If the OP is looking to write a story, the info I've given above should suffice. Heck, people are willing to believe particle-less spirits exist, without any details. How far fetched is a planet made of energy? The planet doesn't even have to be a sphere. Besides that, I've also mentioned the Matrix. – Nav Jan 26 '17 at 15:17

Can there be a planet with no dust?

No, depending on your definition of "dust" Space is not a sterile vacuum, it is full of stuff ranging from the sub atomic size, to the tremendously huge. And all this "stuff" is moving, some in a repetitive orderly fashion, and some just blowing around on the cosmic winds.

A planet, by definition, is going to have to be in a system, have an orbit, at least one sun, and be over a certain size, and has to be what ever the term is for "not just a compressed lump of gravel and or ice chunks"

You will not have anything like that, that will not be rained on but tons of material loosely referred to as "Dust"

It does not matter what you work out after the dust has landed, it did land and so the planet has dust, even if the planet is 100% covered in water, it has dust, which before landing on the water was floating in the atmosphere. The bottom of the ocean is covered in dust, we call it silt.

Having a mechanism to expel the dust is not an absence of dust, just like using some pledge and a rag at your house does not make the house dust free, it just cleans the build up, the dust is still raining down, you will need to dust again.

If you made an artificial planet, dust is still raining down on it. And even if we allowed it to be called a planet, after totally deviating what defines planet, and put the thing in a static position in deep space near nothing, dust moving through the universe from countless galaxies is still going to find it.

And nearly anything you can think of to build a planet out of eventually becomes dust on it's own. All things have a finite life before the7 break down.

# Yes it can!

It's a fast-spinning planet with atmospheric pressure around 1 Earth atmosphere, made of CO2 and average temperature of −78.5 °C (the sublimation temp of C02). Or some other light molecule so that most materials are denser that it, and it must not have liquid state at the atmospheric pressure.

Whatever dust is created by non-CO2 meteorites (impact or from burning in the atmosphere) is buried during the night, when a layer of C02 precipitates on the surface. And whatever CO2 is eroded, is evaporates during the day.

So technically there is transient dust from meteorites, but it is short-lived. It is also (somewhat) important that the atmosphere is relatively calm, so that whatever dust forms it is not carried around all the time, but is capable of settling down and being eventually frozen into CO2.

Look up meteoritic dust influx. You might remember the first moon landing. Even though they were about to run out of fuel they were commenting on the amount of dust being kicked up. You might also remember the huge pads on the landing gear. They were afraid that the lander would sink into the dust. There is constantly stuff hitting any atmosphere on every planet. It might be that such a planet has a surface that removes the dust such as the molten lead planet mentioned, but the dust will be delivered there by the natural processes of the universe.

However, if you can ever travel there and find that there is no dust then you can be assured that the inhabitants will be able to explain to you why there isn't any since they will speak English... at least that is how it is on Star Trek.