Mars question unanswered
SCIENCE Presence of water no guarantee of life

By Wayne Harris-Wyrick

Published: November 4, 2008

There is water on Mars. All that we know of it now is frozen as polar ice caps or permafrost below the surface. But there used to be a lot more water — liquid water — on Mars, and it hung around a long time.

The geological evidence of this past water looks a lot like the geology of water on Earth today. This has potential implications for life on Mars. On Earth today, where there’s water, there’s life, with almost no known exceptions.

Several lines of evidence support the past presence of water on Mars. Photographs show dried riverbeds and deltas where rivers once flowed into an ocean. Channels run down the sides of canyons and crater walls. Past studies led scientists to the conclusion that water came to the Martian surface suddenly in short-lived but massive floods.

However, according to a new study, the valley networks on Mars were carved by recurrent floods over a long period. Such features require periodic flooding separated by dry spells. This alternating wet/dry cycle on Mars may have lasted for hundreds of thousands of years.

The twin rovers Spirit and Opportunity found layered sedimentary rock with high levels of various salt compounds, indicative of surface water lasting for geologically long periods.

More recently, the Phoenix lander found ice below the surface, falling snow and frost. Two instruments have detected calcium carbonate and clays, minerals that form only underwater. The pH level of the soil is almost exactly the pH of ocean water on Earth.

So, could life have existed on Mars? Maybe, but current evidence neither supports nor denies that idea. Life first appeared on Earth 500 million years after our planet formed. That’s a far cry from the few hundred thousand years of a wet Mars.

But the situation may not be that simple. Mars has ice frozen as permafrost below the surface. Is there liquid water deeper down? Other evidence seem to indicate that all the subsurface water in Mars is frozen solid, making the possibility of current life on Mars very slim. But we just don’t know. It may not be until scientists drill deep holes on Mars or explore the recently discovered caves that we will finally know the answer.

Wayne Harris-Wyrick is director of Kirkpatrick Planetarium at Science Museum Oklahoma. Questions or comments may be e-mailed to wwyrick@scienceuseumok.org.

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