re: Why are 'science people' preaching about climate change but cool with terraforming Mars?

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So, how could we jump start Mars’s magnetic field? First we would have to somehow liquefy the outer core of the planet. Then the planet’s own rotation would create a dynamo and generate a magnetic field like Earth’s. This could be done using an extremely large nuclear bomb which would be placed near the core of the planet. The bomb would have to release enough energy to liquify the core, that’s A LOT of energy! This is similar to the premise of the movie “The Core”. In that movie they were trying to get the molten core of the earth spinning to restart the dynamo where we would have to melt the core of Mars first. Another interesting idea is to run an electric current through the planet. The resistance of the core would cause it to heat up, similar to how a wire heats up when you short circuit a battery. Again, this would take a lot of energy but this way it would be delivered by electricity which could use solar or some other power source. Say we were to somehow terraform Mars for habitation. We could warm it up and give it an Earth like atmosphere and a magnetic field to protect it from solar wind, but would the atmosphere stick around?

My intuition tells me, unfortunately, no. Even with a magnetic field Mars is just not massive enough (1/10 the mass and ~0.4 the gravity of Earth) to hold on to an Earth-like atmosphere at Earth-like temperatures. Escape velocity for planets in the Solar System Escape velocity for planets in the Solar System vs. their surface temperatures. Credit: Cmglee, Source, license: CC BY-SA 3.0. You can see that on this plot of atmospheric temperature vs escape velocity, also reproduced on the right. The dots represent the planets (or moons) in our solar system and the lines show the temperature and velocity at which different gasses will escape. Any planet that lies under a line in this plot cannot hold on to that specific gas. If we were to warm Mars up to something like the temperature of Earth so that liquid water could exist on the surface, we would move the point on the plot horizontally so that it is under the earth. At this temperature, Mars could not hold on to water in its atmosphere, and nitrogen and oxygen would be very close to the limit. If we don’t care about the atmosphere being like Earth’s, then a magnetic field would definitely help protect a warmer CO2 atmosphere from solar wind, but this would be a drastically different atmosphere than Earth’s.

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