5 Most Incredible Discoveries of the Week

A microbe that nearly made the Earth a dead zone and an intriguing ocean discovery on a moon of Saturn highlight the list:

• Villain That Nearly Killed All Life on Earth Is ... Tiny: Name your favorite culprit for the mass extinction that wiped out nearly every life form on Earth 250 million years ago. A spectacular asteroid, perhaps? Massive volcanic eruptions? A new study encourages sleuths of the Permian era to think much, much smaller. MIT scientists propose that a microbe called Methanosarcina proliferated in the ocean and wreaked havoc on land and sea.
• Saturn Moon Has Underground Ocean: Saturn's sixth-largest moon holds an underground ocean with at least as much water as Lake Superior, according to data from NASA's Cassini spacecraft. Big deal? Some scientists believe Enceladus is now the place in our solar system where we're most likely to find extraterrestrial life.
• Scientists: We've Found the Holy Grail: Historians claim that a goblet long identified as belonging to the daughter of an 11th-century Spanish king has actually housed the Holy Grail—and has been sitting in a basilica in the northwestern city of León for nearly a thousand years. A three-year quest that began at a Cairo University in 2011 led researchers to conclude that the onyx goblet is the one Jesus Christ used at his last supper.
• Morning Light Could Be Key to Weight Loss: Getting a good dose of early morning light on a regular basis appears to be a simple but remarkably effective way of maintaining a healthy weight. Researchers found that regardless of caloric intake, people who had more early light exposure were the most likely to have a low body mass index.
• President Harrison Didn't Die How We Thought: The history books tell us that William Henry Harrison died just a month after taking office in 1841 because he caught pneumonia while delivering his inaugural address in lousy weather. Now, modern epidemiology is revising the diagnosis. Two experts say Harrison's real killer seems to be a gastrointestinal illness called enteric fever. And for that, we can blame a marshy area of raw sewage near the White House.

Click for more discoveries, including one about why zebras have their stripes. (More discoveries stories.)