How to craze the surface of a planet?

Question

I want to generate a world with a surface that has the same sort of patterning is seen in the surface of a dried lake bed when the mud cracks, but greatly scaled up. Each individual plate/fragment of mud being equivalent to an irregular slab of surface rocks 50 – 200 miles across on the planet’s surface with a canyon like gap all around. Ignore any curling up at the edges. The important feature is the fragmentation pattern.

How could a world with this sort of this topography evolve naturally? Is it even remotely possible?

I understand that the forces that cause mud to crack would not work at larger scales, but is there anything else that could produce a functionally similar effect a much larger scale?

The world is similar to earth. “Similar” means that humans must be able to live on the surface without the need of advanced technology to survive. Any of the earth’s physical parameters such as gravity, orbital distance and water content etc can be adjusted if that helps.

Answer 1

I thought that mud cracks and the crazing one sees in ceramics is governed by the microscopic character of the mud / clay and so will not scale up. But maybe it does.

Here are giant cracks on a dry lake bed on Mars. Same processes at work as on earth.
from https://www.space.com/7287-giant-cracks-mars-hint-ancient-lakes.html But still 3 orders of magnitude less than what you want.

I was not able to find cracks this big on earth. I thought maybe the Aral Sea but no. I think maybe the big ones on Mars are an artifact of Martian conditions. You could handwave up what those are and magnify them but I worry about your inhabitants - a difference between Mars and Earth but 100 times more starts getting iffy.

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There is a different way to make big cracks that result in adjacent irregular polygons. Ice.

http://ocean.si.edu/ocean-photos/antarctic-pack-ice

These shapes are made by the pressures of the ocean beneath. The ice is relatively thin. But what if the ice were phenomenally thick, covering the planet and the pressures from beneath were immense? Could you crack an ice layer kilometers thick into the giant blocks and crazed patterns you want?

https://www.nasa.gov/jpl/europas-stunning-surface

Europa's icy surface is covered with immense cracks many kilometers long. Maybe it is not tessellated enough for your purposes but you could make it more so. The topic of these cracks was addressed on the planetary science stack.

https://space.stackexchange.com/questions/2226/what-causes-the-cracks-on-europa-to-form

Stolen from that answer:

The exact nature behind formation of these younger cracks is still somewhat of a mystery, but most of the theories suggest a combination of interactions between Europa and Jupiter, such as tidal forces, effects of changes in strength of Jupiter's magnetosphere as the satellite orbits it, Jupiter as a source of radiation causing greenhouse effect on Europa's liquid subsurface with the surface isolating the heat within its shroud, and also difference in radial velocity of the liquid oceans compared to its surface and possible geological activity beneath them to keep this oceanic mass warm enough to remain liquid, forming surface cracks similar to those found in the polar regions on the Earth, and perhaps even warm enough at its bottom to sustain some forms of life.

Europa is still cracking. I think your planet will have to still be cracking too: the flexing produced by Jupiter is not something one can easily turn off.

I wonder if you had a smooth siliceous lava flow (maybe from an ancient impact?) covering the surface of a planetary body if it could be cracked in a similar way, by immense tidal forces flexing it?

Answer 2

That is a surface contraction pattern. When the mud dries the surface dries and contracts faster than the deeper layers.

This might happen if the surface temperature of the planet cools rapidly and significantly. I am not sure if there is a natural process that could do this and leave you with a habitable planet, but terraforming a Venus type planet that had a too high surface temperature might be sufficient.

The surface would cool hundreds of degrees (celsius or Kelvin) within geologically very short period of time. In fiction terraforming usually takes few decades or centuries. This would be too fast for the geology to "equalize" in any meaningful way, so the surface should contract in small separate pieces. Just like mud.

Whether this would really work and how the results would actually look like depends on the specifics of the terraforming process and oddly enough I do not know the details of rapidly terraforming Venus.

Answer 3

The planet Mercury has surface features on the scale of what you want:

The large scarps were formed as Mercury’s interior cooled, causing the planet to contract and the crust to break and thrust upward along faults making cliffs up to hundreds of miles long and some more than a mile (over one-and-a-half kilometers) high.

This results from the following properties:

• Mercury is small enough that its crust forms a single tectonic plate
• Mercury's iron core takes up most of its volume, and as it cools, its crust cracks and folds as it shrinks

Its pictures and topography surveys don't look very cracked, since it's been thoroughly cratered by impacts, but if you only need the ridges to prevent travel, a planet with a similar structure would work.

If you need the aesthetic effect, those impacts have got to go. Supposedly most are the fault of the Late Heavy Bombardment, so maybe your planet never suffered such a thing.

If you need the cracks to work exactly like a dried lake, so they have yawning canyons instead of upthrusting ridges, you would need the opposite effect: the surface cools/contracts faster than the core. Or maybe, the core heating up. I don't know of any examples of either, so maybe see if any of these are plausible enough for you:

• The core has enough radioactive material to overcome its natural planetary cooling
• The crust is made of materials that shrink faster than the core
• A driveby of another massive object stole (regularly steals?) mass from the crust, which redistributes over the surface eventually

These range from "violates core tenets of planet formation" to "hours of conversation at the planetary geology convention". Even if you found a reason you like, there is one more issue: any water would naturally flow into the cracks over time.