I think this post and many of comments here fail to grasp that a true full scale colonization mission of Mars would likely neccistate some sort of terraforming effort in the far future. Along really long timescales, you can even imagine the opposite effort to alter human biology. The major first step is simply getting there.
Another factor is that the civilization that is able to reach Mars is going to be the one that has achieved the capability to dominate Earth. The original purpose of the space race was war, and though people no longer think about it, mass produced planetary scale rocketry beats all other weapons.
>mass produced planetary scale rocketry beats all other weapons
if your goal is only destruction sure, the likes of ICBMs are great. for conventional warfare when you want to do things like topple regimes, annex resources, subjugate peoples, etc. not so much. it's exactly why Russia hasn't used nukes in the Ukrainian conflicts.
Right now we are looking at the effects of HIMARS rocket artillery in Ukraine. Each rocket costs over $50,000. Cruise missiles cost over $1 million. Many nations can produce rockets, but cannot produce them cheaply. Despite the US and Russia having global strike capabilities, this stuff doesn't come cheap. If they were cheap (say via continued investment in space exploration), you basically have a win button for any global conflict. There's literally no reason rocket artillery has to cost over 50 grand in the grand scheme of things. In a total war, we could probably get it down to less than $2000.
Another factor is that the civilization that is able to reach Mars is going to be the one that has achieved the capability to dominate Earth. The original purpose of the space race was war, and though people no longer think about it, mass produced planetary scale rocketry beats all other weapons.