This is John Batchel.

Colleague, Bob Zimmerman, comments on the question,

it did water flow on the surface of Mars?

There's reason to believe, yes, the left behind channels,

but there's a puzzle about the atmosphere.

Here, Bob explains it.

It remains a mystery until we get there.

We as in human beings, not robots.

Although, we'll see.

Bob Zimmerman.

Ample evidence that suggests water might have flown on,

flowed on the surface of Mars once liquid water but the

problem with that is has continued always to be that Mars atmosphere is too cold

and too thin for liquid water to exist if ice is on the surface and it starts to

get heated it will immediately sublimate into a gas. It will not

become a liquid and flow. It just doesn't, it can't happen with the atmosphere and the

temperatures on Mars. And there have been many, many models created to try to create the

situation where once Mars had a thicker, warmer, and climate that would allow water to flow.

But none of those models has really satisfied anybody.