Solar mass loss models
Hi Chris
There are early Sun mass-loss models which are compatible with the current solar structure revealed by helioseismological data and modelling. It's possible that the Sun was a lot hotter - BUT also the solar wind and UV was enhanced too, meaning atmosphere blew away easier on Mars.
It would be an irony that the warmth that made Mars 'habitable' also came at the price of stripping away its atmosphere.
Adam
