Shifting Ocean: Tipsy Mars may explain undulating shoreline
By Ron Cowen
By proposing that the Red Planet was tipped halfway over on its side several billion years ago, astronomers this week provide a new perspective on—and new support for—the long-standing notion that Mars once held a vast ocean.
Viking-spacecraft images of the northern lowlands of Mars, taken in the 1980s, showed what appeared to be two ancient shorelines, each several thousand kilometers long. The features resembled those found along coasts on Earth. Researchers suggested that the shorelines enclosed a basin that covered one-third of the planet and was filled with water a few billion years ago.