NASA: Neue Erkenntnisse darüber, wie der Mars unbewohnbar wurde

I thought this was settled science ages ago – planet has not enough gravity to hold onto a thick atmosphere, lack of magnetosphere causes the atmosphere to be lost too, much of water has gone, rest has frozen in the sub surface.

IMO no amount of terraforming will solve that. Some FAR FAR off hypothetical solutions have been proposed for some artificial magnetosphere at a Lagrange point but any short term efforts and gains will be a rapidly losing proposition because it will all leak away again.

Gravity not withstanding, to hold atmosphere,…., With enough plastic & duct tape …., like bubble boy, we could create bubble Mars. Or at least , like in some sci-fi shows, surface bubble domes. A series of them, connected, and keep adding more. It’s the old bio-dome idea, but with updated technology. Cities weren’t built in a day (except in China). Heck, even double insulated, so it’s easy & safe to fix cracks/breaks/dents.