SCIENCE!

mars had the top of its head shot off a long time ago. this is actual science.

the conundrum was that mars’ southern hemisphere is highlands, rough and crater scarred from millions of years of impacts and so on. whereas the northern hemi is smooth and low and doesn’t match up. one theory was that mars was one of many hard bodies in our solar system (and likely everywhere else too) where a gigantic impact crater on side a matches up with a vast lava upwelling on the far side.

but there was no candidate for the crater. now, they’re thinking that the impact basin’s shape itself suggests the impact. a comet or somesuch smacked into mars at an angle, and blew the crust off of the northern hemisphere, which cooled and resettled, lower and smoother than the original crust on the southern half.

a similar theory, the giant impact hypothesis of lunar formation posits that the earth was impacted at some point by a mars-sized body. a massive amount of debris was tossed out and eventually accreted into orbit and became the moon. meanwhile, the remnants of ‘theia’ and the proto-earth settled and became the earth we now know and love.

space is awesome. it’s nothing but things smashing into each other and blowing up. my favorite is galactic collisions which cause gravitational distortion and eventually a single new galaxy.