To the untrained eye, Photo 51 was simply a grainy black and white image of dark marks scattered in a rough cross shape. But to the eye of a trained scientist, it was a clear portrait of a DNA fiber taken with X-rays. And to young scientists James Watson and Francis Crick, it confirmed their guess of deoxyribonucleic acid's structure. In 1953 the pair was racing toward solving the mystery of DNA's structure before other scientists could beat them...

On the night of April 14, 1912, as it made its first voyage, the luxury steamship Titanic struck an iceberg. Then, a few hours after midnight on April 15, the ship sank thousands of feet before settling on the ocean floor. And that s where it stayed, whereabouts unknown, for the next 73 years until it was discovered by oceanographer Robert Ballard and his crew. The pictures and video Ballard brought back from the 1985 discovery helped stir new interest...

Weighing as much as a small car, a rover named Curiosity rolls quietly around Mars. Scientific instruments pack its body and cluster at the end of a mechanical arm. An arrangement of lenses and instruments tops its mast, like a face. To the many NASA workers involved in Curiosity s mission on Mars, the rover is not simply a robot, but an astronaut bravely exploring an alien place. Curiosity s instruments collect data and its cameras take images of...

The biggest oil spill in U.S. history that polluted the pristine waters of Alaska decades ago and killed thousands of birds, mammals, and fish, still haunts the people who are living with its aftermath. On Good Friday 1989, the huge oil tanker, Exxon Valdez, ran aground in Prince William Sound, spilling millions of gallons of crude oil into the water-oil that would eventually cover more than 1,000 miles of shoreline. Cleanup began immediately but...

Millions of tons of plastic slip into oceans every year. Some floats and travels slowly with the currents, endangering the health of marine animals. The rest is hardly visible but is far more dangerous. Tiny bits of plastic sprinkle the ocean's surface or mix into the sandy seafloor and beaches. It ends up inside birds, fish, and other animals, harming them-and ultimately humans. Experts struggle with fear and hope as they work to stop the flood of...