<p>Seen by an orbiting satellite, layers in a Martian trough reveal patterns of long-term climate change on the red planet.</p><p>Over the past couple million years, variations in Mars's orbit have changed the distribution of water ice around the planet. That means ice and dust have built up at the poles in varying amounts over time. (See <a id="vj60" title="Mars pictures." href="http://science.nationalgeographic.com/science/photos/mars/">Mars pictures.</a>)</p><p>Looking at the walls of troughs in the polar deposit—like the one seen above in a picture from the Mars Reconnaissance Orbiter released yesterday—scientists can study changes in Martian climate the same way they use ice cores to track <a id="t.lk" title="climate change" href="http://environment.nationalgeographic.com/environment/global-warming/?source=NavEnvGlobal">climate change</a> on Earth.</p>

Martian Climate Record

Seen by an orbiting satellite, layers in a Martian trough reveal patterns of long-term climate change on the red planet.

Over the past couple million years, variations in Mars's orbit have changed the distribution of water ice around the planet. That means ice and dust have built up at the poles in varying amounts over time. (See Mars pictures.)

Looking at the walls of troughs in the polar deposit—like the one seen above in a picture from the Mars Reconnaissance Orbiter released yesterday—scientists can study changes in Martian climate the same way they use ice cores to track climate change on Earth.

Image courtesy NASA/JPL/University of Arizona

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