The Arctic is a receptacle of the planet's air pollutants -- from forest fires to human-produced carbon dioxide emissions -- and a coordinated international effort is geared toward learning more about pollutants' effects at the top of the globe.

As scientists continue to explore the poles as part of the International Polar Year, hoping to better understand the Earth's most extreme environments, some researchers are looking for answers even farther off -- toward the north pole of Mars.

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