DISAPPEARING PRAIRIES For thousands of years, people have been changing the world’s prairies. Now many prairies are in trouble. They are among the most threatened ecosystems on our planet. Will prairies survive?
COMETS AND METEORS Around 65 million years ago, something huge may have slammed into the earth. At about the same time the dinosaurs disappeared. Did their disappearance have something to do with a comet or a meteor?