"Head and his team examined high-resolution images of the crater and its gullies taken by orbiting spacecraft and found evidence of features that suggested glaciers once covered the crater floor about 10 million to 20 million years ago."

I'm going to assume that Mars is approximately as old as Earth, about 4.3 billion years. And these people are saying there was surface ice in large quantities 10 to 20 million years ago. Therefore there must have been a lot of H2O on Mars for the vast majority of it's existence. (I realize comets may have added a significant amount after the formation of the planet.)

So for most of it's life Mars had great quantities of H2O in various forms on it's surface? And then it all left?

Seems odd.

Arf