[dan_mctree]

I wonder if there'd be any good way to confirm or rule out an ancient Martian civilization. Would Martian surface structures be able to last a few billion years? Or would Martian processes be able to make all of them disappear? And how about underground structures?

[ethbr1]

I read somewhere that for geologic-scale signatures you need something that is:

   - Chemically inert
   - Recognizably artificial w/o context
   - Physically hardy
   - Planet-scale mass-produced

On Earth, apparently "panes of glass" are one of the few things that qualifies.