Seventh in a series of posts inspired by ten topics in ‘Insights of the Decade’ from the December 17, 2010 special issue of Science Magazine The topics are: Inflammation, climatology, tricks of light, alien planets, the microbiome, cell reprogramming, Martian water, the DNA time machine, cosmology and epigenetics. The original articles are now behind a paywall; they won’t be reproduced here, but their gist is present. I’ll try to put them in context and also within the Impact Areas of SciTechStory.

Perhaps ‘fuss’ is the wrong word for describing the attention paid to water on Mars. Certainly the average citizen of Peoria (Illinois, USA) has heard of no such fuss, and probably wouldn’t consider it anything to fuss about even if they heard it. Astrobiologists fuss about it, of course. However, it’s not like they’re particularly attached to water, per se. They’re not astrochemists, most of them. No, there is one reason for the majority of fuss over water on Mars – life.

As far as science knows, which at the moment is limited to what’s been found on Earth, life is inextricably bound to water. Wherever life is found, it’s in water or has access to water. This does not mean wherever there is water, there is life. First and foremost, ice – which is water of another form – does not produce life (though it may preserve it). Neither does steam nor atmospheric water, so far as we know (there may be exceptions). So the water for life needs to be liquid at least some of the time. That’s where the great interest in water on Mars, liquid water, comes in.

Humans started centuries ago with imagining water on Mars. Using early telescopes, it was certain there were canals on Mars, probably made by alien creatures. Better telescopes showed there were no canals, no aliens, and Mars to be a very dry place indeed – no water to be seen. Finally, only a few decades ago, Earth began sending emissaries to Mars in the form of probes and orbiting surveyor satellites. First it became obvious from satellite pictures, though not directly provable, that there used to be water on Mars. The visual evidence was everywhere, from washout gullies to the shores of ancient seas.

Then came the decade or so of Mars rovers, some of the most intrepid machinery ever built. Named Sojourner, Spirit and Opportunity, they wandered around the surface of Mars poking their sensors and cameras into everything in range. At first it looked like while there once was plenty of water at the surface, it was all gone except for possible upwellings of brine (high salt solution).

It’s clear the surface of Mars is not hospitable to water, which makes it equally inhospitable to life. The surface temperatures average around -63 C (-81 F), so liquid water is unlikely, or its existence is very brief. Frozen water, however, is aplenty. That’s been known for sure since the orbiting observations within the last decade. At the Martian poles there are enormous glaciers of water ice, comparable to the Greenland ice-cap in size. Outside of the poles, it’s known that water exists below the surface of Mars, perhaps a great deal of water. Most or all of it is frozen, but we don’t know that for fact. There might be, embedded in soil or rock, pockets of liquid water.

Such ‘unfrozen oases’ present possibilities that have one overriding interest – where there is persistent liquid water, there could be life. At least that’s how it works on Earth. What tantalizes biologists about Mars is that because it at one time had a great deal of surface water, and may have subterranean water even now – it may not only have produced life, but it could have had an entirely different evolutionary path; or none at all; or the same as Earth. In fact, it’s long been speculated that Mars is the source of life on Earth, via material ejected from Mars billions of years ago.

That’s what all the fuss is about. Of all the places in the known universe (which admittedly isn’t really that many yet), Mars is the most likely place where scientists feel the conditions may have existed for the origination of life, and where conceivably life may still exist.

What would be the impact of finding life on Mars? Life elsewhere than on Earth is one of the things SciTechStory tracks, as an impact area “Exogenous Life.” It’s not because it will have any immediate practical effect on humanity. If life is discovered on Mars, it will be well before any human being is there to see it, much less use it. No, the impact of life on Mars – implying life existing anywhere in the universe – is the change in millennia of human thought and belief. I don’t think there will be a great deal of surprise, at least not among the cultures exposed to science fiction. But there will need to be adjustments to our thinking. Many religions will have difficulty with the idea, as the uniqueness of life on Earth and mankind in particular, has long been a core belief. Life on Mars would cast the pall of provinciality over such beliefs.

And if there is no life on Mars and never was? As usual, negative proof is never final proof – there could be life under other conditions elsewhere. Nevertheless, no life on Mars would mean that the conditions for the creation of life are more stringent and rare (at best) than currently supposed. That too would change our thinking, but not so dramatically.

The previous decade did a lot to whet the scientific appetite about Mars. It’s a wonderfully familiar yet strange planet. The next decade or two, money and will provided, could bring concrete evidence of life or no life.

Other SciTechStory posts on Mars and water:

Mars rover Spirit: Trapped but contributing to the water story
Don Juan Pond may teach us about Mars
Life on Mars, if it exists, is below the surface
Martian-lakes-may-have-lingered, life-more-likely