That's bad too; so what does that mean regarding the subject of heating it up? Even more hopeless?
Let's take a stupid plan...and walk it out. I'm going to center this on Musk....because his ideas are a rehashing of decades old bad math.
The primary issues with Mars are the magnetosphere doesn't exist, the amount of solar radiation is much smaller than on Earth, and the atmosphere is much thinner. The proposal is to drop some nukes on where they can find large locked bodies of water, or material that will vaporize given enough energy. Think about those perchlorates...which are largely a substance that latches onto water molecules (it's a basic description...please forgive the over simplification).
What this does is generate a lot of heat, create a lot of atmospheric pressure by turning trapped solid water into gas, and with bad Musk math you could theoretically use those nuclear explosions to at least partially liquify the core of the planet and maybe get a magnetosphere going...again based off of virtually no reliable scientific data. All of this sounds great as a thought exercise...until you start doing some real thinking.
1) There's no real proof that liquefaction of a planetary core generates a magnetic field...and even less proof that we could do it. That's an enormous amount of nukes...that are hand waved away as somehow both huge and controllably small. This is where the theory breaks down against a cursory mathematical thought experiment...and a Jerry Breckheimer film (The Core) is proven to be a silly thing to claim as a realistic solution.
2) The amount of water and other light gasses that would need to be liberated for just about 49% of Earth's atmospheric pressure (to get the current 1% to 50%) would be 2.695 quadrillion tons. That's right...Earth's mass is about 1 millionth that of its atmosphere (
Britannica), at 5.5 quadrillion tons. This is oversimplification given that Mars is about 1/10th the mass of Earth...but it does a lot to illustrate the difference between "we just need a little extra gasses" and "we can have a comfy to breathe in atmosphere.
3) The last bit is that Mars is farther from Sol than Earth. This seems obvious...but the solar irradiance on Mars averages to 590 W/m^2 versus 1000 W/m^2 on Earth. Roughly 60% of the sun's energy doesn't sound like a deal breaker...until your atmosphere is basically incapable of storing heat because it's so thin. The proposal I've seen for this is to use the natural oxides in the soil to separate into metals and oxygen using electrolysis, sinter the metal into a foam to act as an insulative layer, and construct new buildings out of primarily iron and steel reinforcements combined with ceramics from local soil. If you can harvest solar energy constantly, even at a low level, the electrolysis provides some heat and a usable metal for construction...assuming you have infinite time. IE...it's time to do something like this with a drone years before we send people, so on day one they've got a ready made stockpile of insulation and construction materials. Lord knows that even a large solar array just won't have the juice to keep people warm on its own.
The TL;DR is that colonizing Mars is a pipedream. I know people want to pretend it's for the good of the species...but right now we just don't have the tech or an easy enough planet to terraform. I applaud that people want to protect humanity from extinction...but I don't see a huge amount of people lining up for the suicide mission. People who say otherwise are aspiring to a solution...but I've yet to see one introduce a concrete plan not made out of as many dreams as good science.
