Drinking Water on Mars?

While the Colorado River no longer reaches the sea, and India’s water table drains away into our soft drinks bottled there, perhaps we’ll get a new source of drinking water–Mars?

Not unless you’re a microbe. Still, NASA finds evidence that drinkable water existed on Mars at one time–and might still, deep below the rock. The importance of this water is that it existed with clays that form at neutral pH, rather than the acidic minerals found by earlier NASA rovers. Water and clay are hypothesized to be the building blocks of life on Earth.

What would the earliest life have “eaten”? Without preexisting biomass, the microbes would have had to metabolize minerals such as sulfides. The point is to combine two minerals (such as sulfide plus carbonate)  in such a way that transferring electrons leads to a lower energy state. The energy yielded can be used to build RNA and proteins out of the carbonate (by “reducing” it; that is, adding electrons with hydrogen from the sulfide.) Eating sulfide may not sound appetizing, but plenty of bacteria do it on earth–some of them within the blood stream of invertebrate animals. Tube worms and giant clams live happily on their sulfidic bacterial blood, without needing to “eat” anything else.

It may be too much to hope for even invertebrate Martians, as we have yet to see any Martian bacteria yet. But there could yet be water trapped below in the rock, enough to support microbes. Like the vast majority of life “on” Earth–where the microbes below ground are believed to outnumber all the life forms “above.”