enter image description here

Starship Not-Enterprise exits hyperspace and looks at the planet filling up the window. Their jaws drop. The planet has a perfect geometric shape clearly visible from space, occupying the majority of the visible surface from their current vantage point.

Its astounding. Sharp boundaries, straight lines, perfect sharp corners, exact angles. Obviously this was created by a very intelligent alien life with large engineering capability and was perfectly planned. It looks like it was drawn in a CAD program.

However there is no mighty intelligent life on the planet and never was. There may be plant and animal life if it helps explain the creation of the shape. This perfect geometry was entirely created by natural processes. Somehow a natural process created something which which looks undisputedly artificial after one first glance.

If this is possible - how could a natural process can create a near-perfect geometric shape that's the most prominent feature on the planet?

Or, if not possible in the real world (which I suspect)…

What's the minimum handwaving one would need to do to get any near-perfect shape becoming the prominent feature on the planet by natural means?

The exact shape doesn't really matter - so long as a natural process can create it and it looks deceptively like an artificial process created it. Can be a Triangle. a Square. Letters or other simple glyphs. Any simple 2D shape. The exact design doesn't matter. It just needs to stand out as clearly artificial by way of being simple 2D geometry.

Am open to a curving shape, but a circle made by a conical volcano isn't going to cut it, the curve is unlikely to be a perfect circle, and the contrast against the surrounding land is going to be low.

With regards to projection any suitable map projection is fine. Straight lines on a sphere's surface bend in 3D space and can bend on maps, so this is open. It can be in true 3D space (eg 3 identical mountains with a perfect plane between their peaks that when viewed in 3D is a perfect equilateral triangle), or perspective to a point in space (that the not-enterprise happened to luckily intersect) so it looks perfect to the naked eye, or becomes a perfect shape when projected onto a standard, existing map projection, eg Mercator.

I have no idea of the best process to achieve this. It could be tectonics. Clouds. Erosion. Animal migration. Rainfall patterns. Shadows from other planets accumulating over time killing vegitation. Anything. That's why I'm asking. It can be transient but needs to be visible for at least a few weeks.

(If "perfect geometry" is considered opinionated for some reason. Any 2D shape from this list appearing prominently on a planet when viewed from space. Best answer is accuracy of shape, then simplicity of geometry.)

Edit: Changed "Perfect" to "Near perfect" - (a valid) quibble about perfection.

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    $\begingroup$ Maybe it's my English, but I find "solid 2D shape" an oxymoron: solid is used for 3D objects. $\endgroup$ – L.Dutch - Reinstate Monica Oct 24 '20 at 7:59
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    $\begingroup$ Are they looking at Saturn? $\endgroup$ – Cadence Oct 24 '20 at 8:15
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    $\begingroup$ A sphere is a pretty good geometric shape, isn't it? Most planets tend to have those as their most prominent feature, encompassing approximately 100% of the planet. :) $\endgroup$ – reirab Oct 25 '20 at 7:11
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    $\begingroup$ @RBarryYoung That's why I said "Best answer is accuracy of shape". Drawing a square in a CAD program and displaying it on screen will be inaccurate by up to 1 pixel width. Printing it will be inaccurate up to the printer resolution - but the more accurate, the better. $\endgroup$ – Ash Oct 25 '20 at 14:51
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    $\begingroup$ The term "Perfect Geometric Shape" has a exact meaning, that cannot exist in physical reality. If you didn't mean it then you shouldn't say it. if you meant something approximate then you should use approximate terms. $\endgroup$ – RBarryYoung Oct 25 '20 at 14:57

"The planet hasn't been tectonically active for nearly a billion years. Winds have blown the surface smooth and its many moons have protected it from large impacts. There are no oceans, but the atmosphere has ambient moisture.

Six hundred million years ago it was nothing but a moist sphere of red dust in a thin shell of carbon dioxide. Then the first meteorite slipped past the moons, presumably from someplace more diverse. Wedged into a crack in this rock was a lichen. The fungal component of this lichen could digest the iron oxide dust, and the plant component could photosynthesize--if slowly.

Nine thousand years ago the planet was completely covered in a thick mat of the lichen, then a green spheroid, still unremarkable. Whatever DNA the original lichen had for handling threats had long since been dropped in favor of more efficient replication. The lichen's growth had slowed by that point--it was choking on the waste oxygen that it had liberated from the soil and put into the atmosphere. Then the second meteorite struck.

The rock exploded upon reentry--probably into hundreds of pieces. It too had a fungal passenger, but only three spores survived the fall. That's what the white circles are: monokaryotic mycelium of the invading fungus, expanding radially. It could probably grow a couple centimeters each day in the oxygen rich atmosphere--unimpeded by the vast green canvas of lichen.

It's amazing Captain, it's like a third of the planet has transformed into a cotton ball. And it smells like the mushrooms you'd get in the grocery store back home. Anyhow, we estimate that by two thousand years ago, the three expanding circles had met each other. That's where the straight lines come from--the circles expanded at a steady rate, but where they met they formed crisp lines of dikaryotic mycelium which has been growing outward.

That's how mushroom sex works, sir. The monokaryotic mycelium doesn't have the genetic diversity to reproduce on its own, so it can only form mushrooms after it meets another patch of mycelium with a different genotype.

The brown Mercedes logo you're seeing on the side of this planet--it's actually three bands of little mushrooms, maybe six centimeters tall and a thousand kilometers wide. We think that they intersect at a spot in line with the meteorite's trajectory, before it exploded.

...or at least that's our best guess. Lieutenant Radagast claimed that he had seen this species before. He says it's psylocibe cubensis. Before we could stop him. Um. He ate one. He's been acting a little strange, but he recently informed us that he's now certain of his analysis.

I've attached an image from the archives. It turned up in the old Earth internet--someplace called the shroomery. Note the straight line formed at the interface between the two samples. You're seeing that, but with three samples, and at a planetary scale.

End of report."

note the straight line


Just how sharp do you need the shape to be? This Hexagon on Saturn is looking pretty artificial,

and it is 14 500km in diameter.

enter image description here

Not to mention the whole planet is a nice sphere, with a multitude of very neat circle forming a disk around it.

Craters can be very neat circles: enter image description here

And simple rock crystals can be quite geometric, although usually not so large as to be visible from space.

Like the Iron Pyrite image by another poster, or how about some Columns from the Giant's Causeway?enter image description here


A possible idea is a ridiculous large pyrite crystals, as they form sharp angles with geometric faces, specifically it forms cubes with metallic surfaces.enter image description here While highly unlikely (maybe why they are surprised to see it), but large crystals do form in space. So your planet may have a large pyrite crystal, mostly buried under the surface, but has a large metallic flat surface, protruding from the surface.

Or if Gold cubes isn't what you are after then maybe large magnetite (iron oxide) crystal, it is normally a metallic black colour. The crystal in the first image has a thin transparent film on its surface, giving the rainbow colours, but it has the right shape. The crystals in the second image show the natural colour.

enter image description here

It forms a octahedral crystals, so if one was half buried under the surface you would have a metallic black pyramid protruding from the surface of the planet.

  • $\begingroup$ A giant crystal at planetary scale would simply collapse under its own weight and turn into a sphere due to gravity. That's the precise reason rocky planets/dwarf planets over 1000km or so in diameter are all spherical, without exception. $\endgroup$ – March Ho Oct 26 '20 at 15:38
  • $\begingroup$ @MarchHo One could handwave it with low gravity composition of the planet and the high strength of the crystals. $\endgroup$ – jpa Oct 26 '20 at 16:38
  • $\begingroup$ a pyramidal crystal of magnetite on a planetoid the size of the mood, and has a base area approximately the size of the Copernicus crater, would cause a stress of about 384MPa at its base, this is below what i predicted for the compressive strength of magnetite (~1000MPa). so for smaller planets the crystal would be structural sound. $\endgroup$ – Nyra Oct 27 '20 at 2:05
  • $\begingroup$ The diamond you linked to at space.com is definitely spherical in shape. $\endgroup$ – cowlinator Nov 6 '20 at 2:57
  • $\begingroup$ @cowlinator that link was more to show that large crystal form, less about the shape of that specific crystal. $\endgroup$ – Nyra Nov 9 '20 at 3:24

Infinite possibilities

The universe gives us already many strange phenomena. Imagine a smiley face in a crater, with a curved mountain as the smile. Welcome to Mars.

Although many things in the universe are chaotic, it happens often enough that straight geometric forms form somewhere on different levels. The celestial bodies that are large enough are surprisingly round. Crystals with sharp corners. Solar systems that look like molecules. Some happen often, others not.

The universe is big [citation needed]. The amount of planets in just the milky way is estimated between 100 and 400 billion. The milky way is a galaxy. There's an estimated 100 billion galaxies observable with our current technology.

In this universe, it's not just likely, but a near certainty that some random stuff in the wild universe made such shapes. Although the size projected in your example is very large and makes it unlikely again. Possibly a tectonic plate is fractured and many shards are being pushed upwards all over by neighbouring plates. Then erosion through weather and plant life makes it a more or less flat surface. Or a weird anomaly in the gravity in the area is causing most meteors to land in the hexagonal area, much like our earth is protected from large chucks of meteor thanks to some large planets in our solar system.

But however unlikely it is, there is a certain possibility it currently exists. The chances of complex life was once calculated to be 0. Yet here we are. Compared to that, the chance of a visibly from space geometric shape in this big, big universe is very good.

  • $\begingroup$ A human seeing a face in naturally occurring rock is not surprising. A human measuring a mathematically precise human or animal face found in natural rock would be surprising. Likewise, seeing a geometric shape is not special, but a geometrically perfect shape would be. $\endgroup$ – cowlinator Nov 6 '20 at 3:00

I'd use an extrasolar diamond from another start system: An ancient star system had condensed a planet out of nearly pure diamond, and when a passing supermassive star disintegrated as a supernova, it stripped the ancient star system and blew the diamond planet's outer mantle into a geometric array of moon sized pieces of diamond, and one of the moon sized pieces of diamond landed on your planet. It can be any common mineral that we find on our planet : calcite, ruby, quartz, the point is that the planet cooled for 8 billion years on a first star, then passed near a fast young giant supernova and was exploded into moon sized pieces and landed on another planet 1 billion years later.


Saturn's moon Mimas has a natural circular crater almost 140 KM across, about 1/3 of the moon's diameter, with a natural mountain in the middle. I believe that may be the largest known near-perfect geometric shape completely visible on a spherical body in relation to the size of the body.

Mimas, a moon of Saturn

And yes, that is a moon.

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    $\begingroup$ This is not a "perfect" geometric shape. In fact it's pretty crude, as circles go. And the atmospheric bands of our gas giant planets are much larger and much closer to "perfect" circles. $\endgroup$ – RBarryYoung Oct 25 '20 at 15:11
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    $\begingroup$ You could argue that there exist no "perfect" geometric shapes in the universe. Here we have what is very clearly a circle, caused by natural processes which interestingly almost always cause a circle that is larger compared to the host body than any other basic geometric shape known to man. $\endgroup$ – dotancohen Oct 25 '20 at 15:21
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    $\begingroup$ Correct, there is no such thing as a perfect geometric shape in physical reality, so it is incorrect of you to claim that the above is a perfect circle. Further, it is not even close to "nearly perfect", it is clearly very crude. Also, as I already explained, it is NOT "larger compared to the host body than any other basic geometric shape known to man". Jupiter's equatorial band forms an actual near-perfect circle that is the size of Jupiter itself. So that's 100% the size of the host body. $\endgroup$ – RBarryYoung Oct 25 '20 at 15:28
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    $\begingroup$ That's not a moon. That's the spare Death Star from that movie set.. It seems to have gotten a bit rusty over time... ;-) (just kidding) $\endgroup$ – user79911 Oct 25 '20 at 21:51

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