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Jason Snell for Yahoo
November 6, 2015 2:57 PM PT
These days, our Mars rovers roll through water-carved flood channels and canyons that are now bone-dry. The evidence suggests that Mars was once a warm, wet world like Earth, but over billions of years it became the dry, inhospitable world it is today, with only tiny trickles of briny water appearing seasonally on the surface.
It turns out that it’s all the sun’s fault, according to new research from NASA’s MAVEN mission, which has a satellite orbiting Mars and analyzing its atmosphere.