The other interesting news is that this water may have evaporated fairly recently in geological time. According to Space:

These opaline silicates . . . formed where liquid water altered materials created by volcanic activity or meteorite impacts on the Martian surface.

"This is an exciting discovery because it extends the time range for liquid water on Mars, and the places where it might have supported life," said CRISM principal investigator Scott Murchie of the Johns Hopkins Applied Physics Laboratory in Laurel, Md. "The identification of opaline silica tells us that water may have existed as recently as 2 billion years ago."

Assuming that water is a prerequisite for life, there might have been life forms on Mars as recently as a couple of billion years ago. That's long before homo sapiens evolved, of course, but it could mean that we might still find fossils from that life. Or even the descendents of it, living in urban hives beneath those opal beaches.

New Signs that Ancient Mars Was Wet [via Space.com]

Nobody seems to be asking the most important question: What exactly is the chemical composition of this so-called water? Partly this is because it was only yesterday that scientists got a big enough chunk of the stuff inside Phoenix's ovens, where it can melt the ice and figure out its molecular composition using a mass spectrometer. So we won't know the exact composition of Martian water for a while. But mostly calling the stuff "water ice" vagues out the truth, which is that this ice is only technically water. No creature on Earth could drink it. In fact, as planetary scientist Andrew Knoll said at the AAAS meeting earlier this year, water on Mars is probably so salty and acidic that it would be essentially poison.

So if you are totally freaking out about how all this water on Mars means we can set up colonies there right away, and meet the aliens who live on the stuff in vast underground aquifers, sorry. We're not going to be able to zoom up there and start ice mining to support our colonies. We'll need to pour a lot of resources into de-salinating the stuff, and sucking all the acid out, before it's potable.

One of the interesting side-effects of this water discovery, however, is that it may re-awaken the scientific community's interest in searching for extraterrestrial life. As Eric Sofge argues on Popular Mechanics, Water is usually considered a precursor for living things, and now that we know water exists under the ground on our close planetary neighbor, it's becomes more statistically likely that water could exist elsewhere too. Or that life could exist on Mars.

If you want the full story on Martian water as it's breaking, check out the excellent coverage on Popular Mechanics. But if you want some back story, check out what planetary geologist Bethany Ehlmann had to say on The Scientific Activist about her work on the Martian ice water. Image via NASA.