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Where in the World is Mars' Water? (axios.com)
An anonymous reader shares an Axios report: In the beginning, Mars was a water world. But at some point in Mars' distant past, much of that water disappeared, leaving behind polar ice caps and a complex geology. Figuring out just where it went has been a major priority for scientists -- life as we know it can't exist without water, and any future settlers would need a steady supply. A new study, published Wednesday in Nature, suggests that much of what remains might in inaccessible. Some went into space, but even more of it may have sunk into the ground like a sponge, only to become bound up in minerals deep within the planet. "Mars, by virtue of its chemistry, was doomed from the start," study author Jon Wade, of Oxford University, tells Axios.
Only 3% of Earth's water exists as fresh water that would have been consumable by humans in prehistoric times. Does that mean that Earth was not inhabitable? Humans don't need much water on a geological scale and there is plenty on Mars in ice at upper latitudes and in mineral salts everywhere.
As far as terraforming, the ability to hold surface water depends on atmospheric pressure and that depends on getting all that frozen CO2 and water vapor into the air.
"He took a duck in the face at 250 knots." -- William Gibson, Pattern Recognition
I have long thought that much of the "evidence" for water on Mars, that is, the sculpted features of the Martian landscape, were due simply to the action of the thin wind there over thousands and millions of years. Living in Canada and having over the decades often observed the sculpting of snow by the wind here, it seems to me the parallels are obvious. The wind does surprising things to snow, both light and heavy snow, and I see many similarities in the thought-to-be-water-sculpted features on Mars.
It ain't the long-gone water, it's the thin but ever-present wind.