Joe Palca

Scientists working on NASA's six-wheeled rover on Mars have a problem. But it's a good problem.

They have some exciting new results from one of the rover's instruments. On the one hand, they'd like to tell everybody what they found, but on the other, they have to wait because they want to make sure their results are not just some fluke or error in their instrument.

Every time a storm brings flooding to a large metropolitan area, there are calls to improve the levee systems that are designed to prevent flooding.

But there's a major problem with doing that. "We don't know where all of our levees are," says Samantha Medlock with the Association of State Floodplain Managers.

Residents of Moonachie and Little Ferry, N.J., are beginning to clear the damage after their communities were inundated by floodwaters. The flooding occurred when a system of levees and berms was unable to control the storm surge pushed ashore by Superstorm Sandy.

Geologist Jeffrey Mount of the University of California, Davis, isn't surprised. "There really are only two kinds of levees," he says, "those that have failed, and those that will fail."

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