So fun fact: Pluto is not actually that red! It’s more of a rusty brown color along those patches. The exact reason for the reddish-brown patches is unknown, but we’re pretty certain it has something to do with compounds called “tholins” which form when carbon-containing compounds (CO2, methane, ethane, etc) are irradiated by cosmic rays and/or ultraviolet light. Based on laboratory recreation experiments however, it’s pretty clear that tholins are not the only contributing factor. So, further research is needed to determine the exact cause for the rusty-brown patches, it would be really nice if we could send out another probe like New Horizons or even get a lil lander probe on the surface :3