There have been proposals for an artificial magnetosphere for Mars to help with terraforming. http://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf http://www.ho

There have been proposals for an artificial magnetosphere for Mars to help with terraforming. http://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf http://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmo... If things truly get bad, we are not entirely out of options (though powering the aforementioned shield might be somewhat difficult).