Re: What is the Martian Soil composition?

Area: Astronomy
Posted By: Sean Sherlock, Grad student Geology
Date: Sat Feb 8 22:15:15 1997
Message ID: 854110921.As

What is the Martian soil composition?

What we know of Martian soil composition comes from experiments carried aboard the Viking landers, and from spectral analysis of light reflected from dust storms in the Martian atmosphere. The Vikings detected iron-rich smectite clays, magnesium sulfate, iron oxides, and reactive oxidizing agents of unknown chemistry. They detected no organic compounds. Spectral analysis of the dust storms identified the smectite clay as montmorillonite. Smectites have the property of expanding when they contact water, and contracting when they dry. Silicate minerals, oxides (mostly iron), and some calcium carbonate were also found.

The greatest mystery may be the identity of the oxidizing agent or agents in the soil. There is some debate as to exactly what this substance may be. It is known to be a highly oxidizing substance that releases oxygen when it is wetted.

The greatest problems to be faced when trying to grow plants on the Martian surface will be: 1. the atmosphere is very thin, only about 1% as dense as on Earth; 2. the lack of microbes in the root zone soil; 3. the extreme dryness; 4. the intense ultraviolet light (Mars has no ozone layer to shield it); 5. the unknown oxidizing agent in the soil; and 6. the lack of nitrogen that terrestrial plants need (nitrogen is less than 3% of the Martian atmosphere).

Also keep in mind that we only have surface data from 2 locations on the planet. The composition of its soil could vary greatly from place to place. Soil in ancient river channels could be quite different from soil in the highlands, or in the polar regions.

You can find more information about Mars and its surface at: Mars, The Astronomy Cafe and the NASA Viking Fact Sheet.

I hope this helps.

---- Sean Sherlock

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