The grooves on Mars' moon Phobos could be produced by tidal forces – the mutual gravitational pull of the planet and the moon, says NASA. The theory is the latest explanation for grooves that were once thought to result from the massive impact that caused the Stickney crater (lower right). NASA/JPL-Caltech/University of Arizona hide caption

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Solar storms from the sun send charged particles streaming towards Mars. Research now shows those particles are stripping away the atmosphere. NASA/GSFC hide caption

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The Two-Way

Researchers Reveal How Climate Change Killed Mars

Mars used to be much warmer and wetter than it is today. Scientists are unraveling the mystery of why it dried out.

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Matt Damon portrays an astronaut who relies on science to survive on a hostile planet. Giles Keyte/EPKTV hide caption

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For several years, a satellite orbiting Mars has seen streaks flowing from Martian mountains during warm periods on the surface. Scientists have now confirmed that water is involved. NASA/JPL/University of Arizona hide caption

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Mars, anyone? Six researchers from the Mars Society sport their best space duds during this 2014 simulation of the conditions that explorers of the Red Planet might face. (From left) Ian Silversides, Anastasiya Stepanova, Alexandre Mangeot and Claude-Michel Laroche. Micke Sebastien/Paris Match via Getty Images hide caption

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Beemer, shown at the Mars Society's Mars Desert Research Station in Utah in 2011, is a candidate for both Mars One and the Mars Arctic 365 program. Max Fagin hide caption

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The Orion capsule is poised to make its first test flight Thursday. If all goes as planned, the unmanned vehicle will orbit Earth twice before splashing into the Pacific Ocean. Kim Shiflett/NASA hide caption

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The Two-Way

NASA Prepares To Test New Spacecraft (That You've Likely Never Heard Of)

The new vehicle, named Orion, is designed to carry humans into deep space. But most Americans aren't aware it exists.

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A member of the Indian security force keeps watch over a launch vehicle carrying the Mars Orbiter probe at the Indian Space Research Organization facility, in Sriharikota, in 2013. AFP/Getty Images hide caption

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In this artist concept provided by NASA, the MAVEN spacecraft approaches Mars on a mission to study its upper atmosphere. AP hide caption

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