NASA rewrites the history of life on Mars


He works two stories above the ground in an office at the NASA Ames Research Center, but mentally Dr. Chris McKay is really on another planet, especially lately.

"Mars was fooling us," he says.

It began 35 years ago when we put the Viking landers on Mars. Besides astounding us with the first images from the surface, they scooped soil and heated it, looking for common carbon compounds that might be the building blocks of life.

But much to their surprise...

"We didn't see what we expected to see," says McKay. "We didn't know why. We thought maybe it wasn't there."

Now they do know why -- the result of what was then a wrong assumption about the salty Martian surface, one that clarified after the Phoenix lander scooped more soil in 2008.

Phoenix found a chlorine chemical called perchlorate, and the stuff is pretty much everywhere on the surface. This is significant because when heated, perchlorate becomes a form of destructive bleach -- a lot like the stuff you would use to clean organic food stains from your shirts.

"The very procedure we used to sample the soil, which was heating it up, caused the perchlorate to react with the organics and destroy them," explains McKay.

As confirmation, McKay duplicated the experiment on Earth and came up with two other chlorine chemicals as byproducts. The same chemicals, it turns out, that Viking found, but which back then researches dismissed as earthly contamination.

"Now we think it really is something that was produced on Mars, in the oven, while we were heating the sample," he says.

It is not proof of life, but next year we should know more when NASA sends a new lander with more refined instruments.

Meantime, there is a lesson here for even the most brilliant of minds who make inaccurate assumptions.

"The lesson here is that Mars is another world because it's got different chemistry going on," says McKay.

Humble pie, from 30 million miles away.

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