COMETS colliding with Earth brought only a fraction of the water and other molecules needed for life to start, according to an analysis of where our atmosphere came from. They must have been there from the time the planet formed, says Nicolas Dauphas of the University of Chicago, Illinois.
The origin of the atmosphere has long been a puzzle. Scientists look for clues in the amounts of noble gases such as krypton and xenon, because these elements are extremely stable. They almost match the ratio seen in the sun, implying that the atmosphere formed from the same material – except…
