WASHINGTON (Reuters) - Sudden, tremendous gushes of water from underground most likely carved out unusual fan-shaped geological formations with steps like a staircase long ago on the surface of Mars, scientists said on Wednesday. The Martian surface boasts perhaps 200 large basins that have formations resembling fans. About 10 of them are terraced, with what looks like steps into the basin. Since they were first seen three years ago, scientists have debated how these formations, some of them 9 miles wide, were created. Dutch and U.S. researchers simulated on Earth on a vastly smaller scale the conditions that might have...