Tuesday, May 25, 2010
Sunday, May 23, 2010
One way that geologists try to decipher how cells functioned as far back as 3 billion years is by studying modern microbial mats, or gooey layers of nutrient-exchanging bacteria that grow mostly on moist surfaces and collect dirt and minerals that crystallize over time. Eventually, the bacteria turn to stone just beneath the crystallized material, thereby recording their history within the crystalline skeletons. Known as stromatolites, the layered rock formations are considered to be the oldest fossils on Earth.