Chemistry In Pictures

Polymer shavings from a scintillation sphere (half-sphere shown at bottom right) emit blue light under an ultraviolet lamp. Kenneth Hanson of Florida State University and colleagues are modifying polymers such as polystyrene and polyvinyltoluene to increase the efficiency at which these materials convert gamma rays to visible light. The ability to detect gamma rays has a number of applications, including the detection of nuclear weapons.—Linda Wang

Yellowstone National Park’s Morning Glory Pool mesmerizes visitors with its rings of color produced by concentric colonies of varying bacteria and archaea that form a mat on the pool’s floor. Before the 1940s, the pool was a deep blue. But as tourists threw trash, coins, and other objects into the water, the debris sank and clogged a thermal vent at the bottom. As a result, the pool’s temperature has dropped nearly 15 ˚F over the past several decades. This cooling has created a temperature gradient from the middle of the pool to its edges. That temperature gradient—combined with existing variations in pH and light exposure—causes different regions of the pool to be ideal for supporting only certain species of microbe, each of which produces a different pigment and adds a new color to the water.—Manny Morone