With the movie “The Martian” coming out soon, and hearing Elon Musk talk about adding green house gases to the Martian atmosphere to warm the planet brings back thoughts I had when I was working on an FTL, far-future scifi novel where the main character was a native-born Martian. When the idea first came to mind I thought about the terraforming concept and concluded, at least for me, that the major hurtle to get over was the low gravity on Mars and the fact that gases quickly escape into space because there isn’t sufficient gravity to hold them in. Since my novel was set in the distant future, I just decided all the Martian settlements were established after we’d discovered how to control gravity and then it was simple to build gravity generators, increase the gravity on Mars to something more Earth-like, and problem solved. Since my novel didn’t take place on Mars, I didn’t need any further explanation. It was only character background info. For those actually considering colonization of Mars, I wonder how they will solve the problem of low gravity and the consequences it places on any atmosphere. As for warming the planet, a large array of mirrors strategically place in space to redirect enough sunlight should work just fine.