Earth’s lack of chlorine traced to early planetary bombardment

Science News : Why Earth has so little chlorine has long puzzled scientists. The study of ancient meteorites has indicated that there should be 10 times as much chlorine on Earth as there is. Although it has been proposed that the bulk of Earth’s chlorine was drawn into its core by iron, nickel, and other metals, that theory has since been disproved by high-pressure and high-temperature experiments. According to a new study published in Earth and Planetary Science Letters, Zachary Sharp of the University of New Mexico in Albuquerque and David Draper of NASA’s Johnson Space Center in Houston propose that repeated collisions of giant planetary bodies with Earth billions of years ago blew most of the planet’s chlorine away into the cosmos. Earth’s dearth of chlorine kept its oceans from being too salty and allowed more precipitation, which may have optimized the conditions for complex life to evolve.