Mercury A to Z: Weird Terrain

Hello, friends!  We’re getting close to the end of this year’s A to Z Challenge, when the last few letters of the alphabet start forcing challenge participants to get weird.  My theme for this year’s challenge is the planet Mercury.  Fittingly, in today’s post, W is for:


Mountains, canyons, plateaus, glaciers, plains, hills, deserts… we already have names for these things.  But scientists sometimes discover landscapes on other worlds that we simply don’t have here on Earth, and they have to invent new words to describe them.  There’s the spider-like araneiform terrain on Mars, or the chaos terrain on Europa, or the cantaloupe terrain on Triton, which really does make parts of Triton look like the skin of a cantaloupe.  In 1974, scientists discovered a weird, new kind of terrain on Mercury.  They decided to call it weird terrain.

If you recall my post about Caloris Basin, then you know that just shy of four billion years ago a gigantic asteroid smashed into Mercury, giving Mercury a crater larger than the state of Texas.  Mercury’s weird terrain is on the exact opposite side of the planet.  This is almost certainly not a coincidence.

Three factors probably contributed to the formation of Mercury’s weird terrain.  Some people say that Mercury’s weird terrain looks almost like something tried to punch its way up through the planet’s crust, and that may be exactly what happened.  When that giant asteroid slammed into Mercury, the force of the impact went straight through the planet and ripped up the ground on the planet’s opposite side.

Additionally, the force of the impact would have sent tremendous seismic waves rippling through the planet’s crust.  When those seismic waves converged on the exact opposite side of the planet, they further disrupted the planet’s crust in that region.

And then there’s one more thing.  The impact event that created Caloris Basin would have sent debris flying all over the planet.  Clouds of flying debris probably converged on the opposite side of the planet.  When that happened, rocky debris started to rain down on that one badly disrupted patch of land.  That one patch of land would have looked weird enough already, so the extra rubble falling from above would have made it look even weirder.

Words like “jumbled” and “haphazard” are sometimes used to describe Mercury’s weird terrain.  In some images, the landscape reminds me a little of a stucco finish.  With the ground being ripped up from below and all that debris raining down from above, it’s little wonder that weird terrain looks the way it does. As far as I know, Mercury’s weird terrain is unique in the Solar System.  I feel like I could be wrong about that, though, so if anyone knows of something similar that’s happened anywhere else, I’d love to hear about it.


This article from the Planetary Society goes into a little more detail about how Mercury’s weird terrain was discovered and how it probably formed.

4 thoughts on “Mercury A to Z: Weird Terrain

    1. I would’ve thought the same. Maybe being on the other side of the planet, but a little off center, would be okay. Or relatively okay.

      Also, now I’m wondering if the Chicxulub impact did the same thing to Earth that the Caloris impact did to Mercury.

      Liked by 1 person

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