Yes, humans can colonize Mars, but there are some issues that we would need to get around. Let's say you launch a rocket into earth-orbit, then from there, fired your engines to put yourself on a trajectory to rendezvous with Mars sometime within the next few months. Sure, you can arrive at Mars, and land, as long as you have a heat shield to survive atmospheric entry and engines that you can start up to touch down safely, but you need a way to get back to Earth, and you also need a way to communicate with Earth.
Moments ago, Starship SN10 attempted a flight to 10km, to then orient itself into a unique horizontal bellyflop position, flip itself upright after it has descended to about 1km, deploy the landing legs, and touch down on the landing pad softly. This vehicle, Starship Number 10, uses Liquid CH4 (methane) and Liquid Oxygen aka LOX/LO2, used by its 3 powerful Raptor engines. Today, SpaceX started their official stream for the Starship SN10 Flight. SpaceX have privated the stream replay, so we cannot replay it. In case you want the link: https://www.youtube.com/watch?v=DDEgFsefrGw&t=541s The vehicle began fueling up with Methane and LOX, and then shortly after, it started the engine chill process, which is the process of chilling the engines down in preparation for engine ignition, so the engine material does not crack or get damaged from sudden shock. The vehicle attempted to start up its 3 Raptor engines, by opening the fuel & oxidizer valves, starting up the turbopumps, sho