Thanks so much for that link. I had been looking for a succinct article that explains the physical constraints on a Mars landing (for equipment only, say). It

Thanks so much for that link. I had been looking for a succinct article that explains the physical constraints on a Mars landing (for equipment only, say). It's safe to say nobody knows more about that problem than Rob Manning. The node in the discussion you refer to is: http://news.ycombinator.com/item?id=2479398 http://news.ycombinator.com/item?id=2479398 As with most threads on this subject, commenters not reading TFA believe that the retro rocket solution is straightforward. TFA explains why it's not.