>>106493839
The Core of Earth is an exotic solid state of matter related to crystalized iron--it isn't liquid.
>>106493475
>>106493826
Nab one of the larger moons from Saturn or Jupiter and put it in orbit around Mars.
If you want to terraform: Venus has always the superior choice on every metric. Cook up some custom microbes to live in the atmosphere and eat their way down through the greenhouse gasses while working from blimps above the worst of the atmosphere.