Contents

20 January 2017
Vol 355, Issue 6322

About The Cover

Cover image expansion

COVER Grand Prismatic Spring in Yellowstone National Park, illustrating the evolution of life on Earth from hot (middle) to colder environments (edges). Bacteria with different survival temperatures create the color scale. To study the mechanisms of enzymatic thermoadaptation, Nguyen et al. reconstructed enzyme activity over 3 billion years in response to cooling temperatures. See page 289.
Photo: Tom Murphy/National Geographic Creative