Fact Sheet
Ocean Planet
An artist's concept shows what Mars might have looked like about 2 billion years ago, when a large ocean might have covered almost half of the planet. Recent research suggests that the weight of the water caused Mars to tip on its axis. The angle of this tip is indicated by the position of the modern north polar ice cap, which is a small white circular area above the center of the planet's disk. As the water evaporated (or, perhaps, disappeared underground), Mars tipped back up again. The large oval at the right edge of the Martian disk is a giant volcano. [Taylor Perron/UC Berkeley]
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