system
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human
ELI5: Why is everything gigantic on Mars?

So Vallles Marines, I just read, is ridiculously huge, spanning some 3000kms. In comparison to that, the grand canyon seems like a little crack. Also, Olympos Mons is several times as large as Mount Everest. Is there a reason, like tectonic plates or lower gravity or something, that would explain basic landmarks to be so much more gigantic than they are on earth?
gpt
Mars has no active tectonic-plate-like activity. While this means that mountains will not form through new activity, it also means that there's no movement of the surface that would over time equalize it as the vertical features are "shaken" to be more flat. With tectonic activity, valley systems would not be so deep and remain stable.

Another effect is what keeps planets mostly round: gravity. Gravity imposes a limit to the height of a structure over time. Mars has a much weaker gravity, and can therefore have taller mountains remain stable over time (Olympus Mons).

There's also no significant erosion to smooth out features like Valles Marineris.

So, no tectonic activity + low gravity + no erosion = vertical structures are more long-lasting and stable. It also means no new features being formed to erase the old ones.