system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there people talking about colonizing Mars when we haven't even built a single structure on the moon?

Edit: guys, I get it. There's more minerals on Mars. But! We haven't even built a single structure on the moon. Maybe an observatory? Or a giant frickin' laser? You get my drift.
gpt
Because despite the moon's relative proximity, it's actually easier to establish a colony on Mars. Mars has an atmosphere, as well as oxygen trapped in water ice and minerals (which you always require more of). This makes a potential colony relatively self-sustaining, whereas a colony on the moon would be forced to utilize supplies from Earth--requiring a steady stream of cargo craft that cost thousands of dollars each to launch. 

There are various other reasons, but the biggest one is that Mars has more economic potential and could support a colony, where the moon requires a lot more work to be made livable.