James D. Watson, whose co-discovery of the twisted-ladder structure of DNA in 1953 helped light the long fuse on a revolution in medicine, crimefighting, genealogy and ethics, has died, according to his former research lab. He was 97.The breakthrough —...

Studying winds on Mars is very difficult. On Earth, we can easily use weather balloons or satellite tools to measure wind directly. But on Mars, there are very few places where scientists can put instruments — and the air on Mars is extremely thin....