Release Images

Release No.: 2006-25
For Release: Thursday, September 14, 2006 - 6:00am

Astronomers Reveal First Alien I.D. Chart

Earth's early atmosphere

Earth's early atmosphere of nitrogen, methane and carbon dioxide was hostile to life as we know it, but friendly to the first methane-loving bacteria. Astronomers modeled the history of Earth's atmosphere to learn what fingerprints to seek on alien worlds. This artist's rendering shows Earth at 4 billion years ago, before continents had formed and while our planet still suffered bombardment from asteroids and comets left over from the solar system's formation.

David A. Aguilar (CfA)