Archean on EARTH Magazine

Early Earth's atmosphere weighed half as much

Tue, 13 Sep 2016 14:05:12 -0400

Researchers analyzed lava flows on the banks of Australia's Beasley River. Gas bubbles that formed as the lava cooled, 2.7 billion years ago, have since filled with calcite and other minerals and appear as white spots. Credit: Sanjoy Som/University of Washington.

The conditions that prevailed on early Earth are, in many ways, as alien as those found on far off exoplanets. Some clues can be found in ancient rocks, but our understanding of the first few billion years of our planet’s history remains hazy. In a new study, a team reports evidence in 2.7-billion-year-old basalt that young Earth’s atmosphere was just half as heavy as today, an insight that may shed light on how marginal conditions found on exoplanets could still support life.

Ancient asteroids boiled Earth's oceans

Mon, 21 Sep 2015 11:28:06 -0400

Donald Lowe and Gary Byerly examine Archean rocks that preserve evidence of impacts in South Africa. Credit: Donald Lowe.

The asteroid that wiped out the remaining dinosaurs — save for the avian variety — 66 million years ago was roughly 10 kilometers wide. Long before that, however, early Earth was bombarded by many larger impactors, which pulverized Earth’s surface time and again. Now, a new study published in Geology suggests that two asteroids, dating to Archean times and estimated to be 50 to 100 kilometers in diameter, released enough energy to boil the oceans and reduce sea level by as much as 100 meters or more.

Giant bolide hit South Africa 2.5 billion years ago

Thu, 14 May 2015 12:05:43 -0400

Tiny spherules, like those seen in this rock found in Western Australia, form when vaporized rock from a meteorite impact condenses into small, round particles. Credit: Oberlin College photo/Bruce M. Simonson.

Some of the oldest scraps of continental crust on Earth cling to the southern tip of Africa and the western edge of Australia. In both places, geologists have found rock layers rich in tiny particles called spherules. Scientists think spherules form when meteorites strike the planet, vaporizing surface rocks that then condense into small droplets, blanketing the surrounding landscape. Now, research published in Geology confirms the extraterrestrial origin of a 2.5-billion-year-old layer of spherules in South Africa, which scientists say was produced by a bolide at least as large as the one that doomed the dinosaurs.