IIUC, the proposal is to build a magnetic shield at a stable Lagrange point between Mars and the sun. Mars would be far away, in the "shade" created by the shie

IIUC, the proposal is to build a magnetic shield at a stable Lagrange point between Mars and the sun. Mars would be far away, in the "shade" created by the shield. So there's no magnetosphere around Mars. It's more like a magneto-cylinder. :) This image explains it better than I can: https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/2017/1-nasaproposes.jpg https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/2017... I don't think an approach like this would work for the moon, because there's no stable Lagrange point between the moon and the sun. (And even if we did build a magnetic shield for the moon somehow, I think it's still too small to accumulate an atmosphere.)