> Do you dispute that those technologies exist

You're talking about rocket technology. I already said, "If the goal was simply to visit Mars, that might be viable." The question is a permanent, self-sustaining Mars colony, where the biggest problem is not "Methane engines" but rather breathing oxygen, drinking water, eating food, not getting irradiated, not getting poisoned, not having circulatory problems, reproducing, and surviving in general.

> people dreaming of colonising Mars

Interesting that you use the word "dreaming".