MARS


I’m most excited about Mars. Like on Earth today, water once gushed there. T e data tell us that. T e rover Curiosity recently scooped up and analyzed some soil. It’s not just dry dirt. Chemicals in it tell us it’s 2 percent water. Other data show us that Mars once had


even more water. It had rivers and streams. In fact, images collected by a spacecraſt orbiting Mars reveal a familiar landform. It’s a delta. On Earth, rivers can form deltas. T e Volga River in Russia, for example, flows to the sea. As it does, the water picks up and carries bits of sediment. Near the sea, the river fans out into a maze of smaller streams. T e water slows. Sediment settles and piles up. A delta forms. Our space images show the same kind of


landform on Mars. Data from one camera even let us analyze what’s in the soil. We think ancient rivers picked up bits of clay, and then dumped them in a big lake. T e water is long gone, but the outlines of the delta remain.


The green on this image of a delta on Mars shows where water deposited bits of clay.


Now, weathering and erosion have shrunk this crater in Canada to 70 km wide.


This image of Earth’s Volga Delta shows the river splitting into smaller channels.


SEPTEMBER 2014 15


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