Yeah, but also don't underestimate the power needed to get it there in the first place. Earth would have a fully fledged industrial complex, the ability to lob

Yeah, but also don't underestimate the power needed to get it there in the first place. Earth would have a fully fledged industrial complex, the ability to lob nukes across space. A burgeoning Mars colony would still be worrying about producing enough water to survive - launching boulders, or even carving chunks off phobos to fling back at earth - neither are easy prospects, and given that a nuke could make the journey in weeks (big rockets, don't care about slowing down), you wouldn't have much time to do anything other than hunker down and wait for fire.