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MARS - JANUARY 6: In this handout released by NASA, a portion of the first color image of Mars that was taken by the panoramic camera on the Mars Exploration Rover Spirit is seen January 6, 2003. The rover landed on Mars January 3 and sent it's first high resolution color image January 6. (Photo by NASA/Jet Propulsion Laboratory/ Cornell University via Getty Images)

Mars has intrigued us humans down here on Earth for centuries, and the Red Planet isn't out of surprises.

While much of the public focus is on Mars' water supply—present and prehistoric—this latest mystery doesn't hinge on a liquid, but a gas. Specifically: methane.

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