[UCANSEE2]

I think Mars is what is left of the collision between a planet and a large rock where the asteroid belt currently is.

If only there were some sign of a collision on Mars.

[going hot]

That's a large fissure.

If no tectonic shifting, then one hell of an impact.

Would be interesting to compare the composition of a few random asteroids many degrees apart along their plane of orbit.

[Windflier]

Here’s a short video which presents a novel, but well founded theory about the formation of Valles Marineris, Olympus Mons, and other Martian features:

https://www.youtube.com/watch?v=TM3WvEeDpAc

[piasa]

Just a flesh wound