The largest climate change in central North America since the age of the dinosaurs 65 million years ago, a temperature drop of nearly 15 degrees Fahrenheit, is documented within the fossilized teeth of horses and other plant-eating mammals, a new study reveals.

A heat-loving archaeon capable of fixing nitrogen at a surprisingly hot 92 degrees Celsius, or 198 Fahrenheit, may represent Earth's earliest lineages of organisms capable of nitrogen fixation, perhaps even preceding the kinds of bacteria today's plants and animals rely on to fix nitrogen.