Carl Sagan, 1991, talk to the Association of Space Explorers
and the question is
"Who would have thought we would be talking about sulfuric acid on Mars?"
I am pretty certain his talk was videotaped.
As for the water source, look to the south of the landing site. Asteroid and comet impacts on Mars sometimes release water from deep below the subsurface, depending on the subsurface structure, and in this case you can see mud flows around those craters.
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