Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:
This phenomenon goes by several different names: polygon terrain, polygon patterned terrain, polygonal patterned ground formations… you get the idea. For the purposes of this blog, I’m making polygon terrain the official way to say it, because that matches up with other terrain-related terms we’ve seen, like chaos terrain or cantaloupe terrain.
Polygon terrain is a distinctive pattern of either cracks or ridges that draw polygonal shapes across the landscape. On Earth, these polygons tend to appear in arctic climates. They’re caused by the repeated freezing and thawing of underground glaciers.
When the ice thaws, the ground above it can sink down a little. Then when it refreezes, the ground is forced back up. Overtime, the surface starts to break and crack, producing a landscape that looks like this:
Polygon terrain seems to be uncannily common in Mars’s northern hemisphere, in regions such as Utopia Planitia. This suggests two things:
- There are large glaciers buried beneath the layers of surface dust and surface rock.
- Those glaciers periodically thaw and refreeze.
Thawing Martian glaciers might or might not produce liquid water. Instead, the ice may sublimate, skipping its liquid phase and turning directly into water vapor. But still, during warmer seasons, it’s possible we might find a trickle of liquid beneath these polygon terrain regions—perhaps even enough to sustain a few extremophile microorganisms.
In the future, human explorers on Mars may take a keen interest in Mars’s polygon terrain. This kind of surface geometrization may not have anything to do with advanced alien civilizations, but it’s still worth a look if you’re searching for simpler forms of alien life. Or at least, it’s a good place to check if your colony is in desperate need of liquid water.
P.S.: For a slightly more detailed (without being unintelligibly technical) discussion of polygon terrain, please check out this post from Planetary Geomorphology Image of the Month.