Today we drove back out to the Cima Lava field. The goal for today was to explore desert soils and how desert pavements form. Desert pavements are the rocky surfaces that form in deserts. The original theory was that light soils were removed by the wind leaving the heavier rocks and pebbles behind. This process is called deflation and does occur in some areas. Over time, a layer of rocks and pebbles form a crust over the desert floor that looks like a gravel parking lot. New evidence shows that these pavements actually may be forming by a wetting, drying cycle. Instead of the wind removing light soils, the wind actually deposits dust over the lava fields. The dust works its way down into the spaces between the rocks. When rain occurs, it soaks down into the dust deposits causing them to expand and swell, lifting up the rocks around them. Over time the rocks and pebbles float to the surface and the soils build up below them. The older the desert pavement is, the deeper the soils will be below them.
Desert Pavements occur on Mars, so by understanding the processes here on Earth, we can get a better idea of how soils form on Mars. We tested the soils at lava flows of different ages for the amount of organic material they contained. The hypothesis being that the older the deposits the more organic material they would have. On Mars, a rover could dig a few inches below the desert pavement and test the deep soils for evidence of life.
We also tested the ancient soils below the lava flows. These had been capped by the lava and should give us a good idea of what the soils were like in the past.
The last thing we looked for was iron minerals in the soil. Iron has been found in the soils of Mars, but different minerals form under different conditions. Some iron minerals need water to form, such as hematite, others do not need water, but higher temperatures. By looking at the minerals in the soil around the lava flows and below the lava flows, scientists can get a better idea of how they form. These results can then be used on Mars to determine the conditions that may have been present there.
Our day had to end a little early. A very rare cold front came in with rain, dust storms and snow.
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