The Search for Life on Mars by Elizabeth Howell

The Search for Life on Mars by Elizabeth Howell

Author:Elizabeth Howell
Language: eng
Format: epub
ISBN: 9781950691661
Publisher: Arcade
Published: 2020-06-03T16:00:00+00:00

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One of the dominant processes during the early evolution on Mars was volcanism. With the Red Planet volcanically active in the ancient past, its surface would have been sprayed not just with lava but with a pervasive, acidic fog. Volcanoes would have belched out clouds of gas that tended to become acidic, thanks to the action of unfiltered ultraviolet radiation upon them. When these poisonous clouds descended to the surface, they would leach any carbonates away. Another important question is how long the water was actually active on the surface. How long did it have a chance to interact with the rocks?

“What you are faced with is an acidic or oxidizing environment by virtue of the volcanic gases that came out, which then get oxidized by the weird photochemistry of the Martian atmosphere,” says David Des Marais, a biochemist at NASA Ames. “This would tend to destroy any carbonates.”

Biologists like Des Marais are trying to assess the chemical effect that water has had on the surface. How have the rocks been chemically altered? In this process, not all water behaves uniformly. Its temperature, ice content, sulfate content, and other chemical properties such as acidity are important factors to consider. A deeper understanding of the water chemistry thus commends itself. “After all, life is a chemical phenomenon,” Des Marais explains. “A lot of what we talk about in terms of habitability of an environment deals with the chemical aspect.”

Carbonates themselves are weakly acidic. That means they, too, would tend to get caught up in the curious chemical cocktail that was the early Martian environment. Perhaps it is no wonder, then, that orbital spectrometers have yet to see them. These instruments don’t penetrate very deeply into the surface—a few microns of dust on the surface can block spectral readings completely. The tiniest layers of dust will cover everything. “The acidic fog would have been easily attainable and zap any of the carbonates right at the surface,” says Des Marais. “The volcanic environment would have made life miserable for any corresponding carbonates at the surface.”

Besides carbonates, the Spirit rover discovered soils and rocks rich in silicon oxides, most likely produced by hydrothermal activity. Such rocks require an interaction between the water and the crust of the nascent planet. Water plus volcanic crustal material produces the kind of rocks observed at various landing sites across Mars. “That makes it more consistent with what a habitable planet would get up to,” David Des Marais notes.


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