KNOXVILLE—Some things are not always what they seem—even in space. For 30 years, scientists believed a large near-Earth object was an asteroid. Now, an international team including Joshua Emery, assistant professor of earth and planetary sciences at the University of Tennessee in Knoxville, has discovered it is actually a comet.

Called 3552 Don Quixote, the body is the third largest near-Earth object—mostly rocky bodies, or asteroids, that orbit the sun in the vicinity of Earth. About 5 percent of near-Earth objects are thought to be “dead” comets that have shed all the water and carbon dioxide in the form of ice that give them their coma—a cloud surrounding the comet nucleus—and tail. [Read more…]