Martian Mysteries

As noted in an earlier post, I find newspaper reports of scientific discoveries irritating and baffling. Their writers must be either scientifically illiterate themselves, or forced to dumb down their writing so much that they can’t convey adequately exactly what has been discovered, and how.

For example? Ok. Consider this. News stories have appeared this week announcing new proof that Mars was at one time much wetter than it is now.

NASA scientists deduce the existence of such water from an accidental discovery. While moseying across the Martian landscape, the Mars rover Spirit dragged a broken wheel, like those on supermarket grocery carts, gouging out patches of bright soil (see photo). Spirit's instruments were sternly directed to perform their intended functions, i.e., to test these patches chemically and by spectrometer. They did so, and in due course found that the bright soil consisted of a surprisingly high 90 percent silica (SiO2). The silica was found to be non-crystalline, which means that it’s not quartz, the primary form in which silica appears in soils (or sand) on Earth.

Now, I have no background in geology. But when a newspaper writer tells us that we now have proof that water used to flow on Mars, because Spirit kicked up some white soil with a high silica content, I don't think he should expect us to just look at him with big sheep eyes, nodding our woolly heads. I really would like to understand how the NASA scientists reasoned from point A to point B.

Silica is a metallic oxide. It's a component of both igneous and metamorphic rocks, minerals formed by high heat and/or pressure. No water is required to produce silica. At least, so far as I know. For example, no one claims that water ever flowed on our own Moon. But lunar shield volcanoes are composed of silica-rich lava. (Otherwise, as I understand it, the lava wouldn't have had much starch and would've flattened out into basalt maria, as indeed can be seen to have happened on much of the lunar surface.) Likewise, the powdery surface soil ("regolith") in the lunar highlands is rich in both aluminum and silica. No one seems excited about the silica content in these areas on the Moon. What’s the difference between them and the patches newly discovered on Mars? Is it that there's a higher concentration of silica on Mars? Ninety percent, as opposed to, say, 60 or 70 percent? And if so, what does this have to do with water?

All the journalist could add for our edification was that the silica could have been formed by acid vapors interacting with water, or maybe by hot springs. Huh? Couldn’t we have been given at least a primitive discussion of the chemistry that would cause these vaguely described conditions to result in unusually silica-rich soil?

"You could hear people gasp in astonishment," said Steve Squyres, principal investigator for NASA's twin Spirit and Opportunity rovers at Cornell University in Ithaca, N.Y. "This is a remarkable discovery."

No doubt. But the news report should have provided us enough geological and chemical background to help us share in NASA’s astonishment.

I'm still not sure why 90 percent silica content proves the existence of water, even after a little snuffling around through interplanetary geological websites. Any geology buffs out there who’d like to weigh in with some expert insight?