The Great Wall of China, built more than 2,000 years ago, stands as one of the monumental feats of ancient engineering. Stretching thousands of miles, it protected the newly unified country from foreign invaders.
But before the Great Wall, warring Chinese dynasties built many other walls for protection. An American archaeologist recently began surveying one of the biggest.
Antarctica is one of the best places on Earth to spot these fallen stars.
Each winter — which is summer in down south — a team of geologists camps out on an Antarctic glacier in the middle of nowhere, often where no human has ever tread. It's kind of like a space voyage, but a lot cheaper.
And it's the meteorite that's done most of the traveling.
It's not been a good year for Florida's citrus industry. The U.S. Department of Agriculture reports that, for the second year running, the orange crop is expected to be almost 10 percent lower than the previous year.
The culprit is citrus greening, a disease that has devastated Florida's oranges and grapefruits, and has now begun to spread in Texas and California.
The law that protects endangered species turns 40 tomorrow and perhaps the most controversial thing the government has done under the law is to reintroduce the gray wolf. Ranchers and hunters strongly opposed the move and now the federal government wants to take the gray wolf off the endangered species list. NPR's Elizabeth Shogren reports, this time, it is the scientists who are protesting loudly.
ELIZABETH SHOGREN, BYLINE: Ecologist Carlos Carroll is walking through the snow in a wide valley in Northern California.