“But right after these impacts started to decrease is when the level of oxygen started to rise pretty quickly.” “Up until about 2.4 billion years ago, the abundance of oxygen in the atmosphere was relatively low,” said Drabon. As the impacts tapered off about 2.5 billion years ago, oxygen began building up.Īssistant professor of earth and planetary sciences at Harvard, co-authored the research. In fact, the impacts were frequent and significant enough that they effectively sucked oxygen out of the atmosphere, the study determined. The bolide that entered the atmosphere above Chelyabinsk, Russia, in 2013, and injured more than 1,000 people when it combusted miles above the ground measured just 20 meters wide.Īnd while by our standards 15 million years seems like an eternity, compared to Earth’s 4.5 billion year lifetime, those millions are mere blips. To put that into perspective, the asteroid believed to have wiped out the dinosaurs around 66 million years ago was 6 miles wide.
These were hulking bolides, ranging anywhere from 12 to 60 miles wide and hurtling into Earth at alarming speeds. Among the key findings: “large impact” asteroids collided with the Earth once every 15 million years, give or take. The research zeros in on the Archean eon - between 2.5 and 4 billion years ago - well before life could be supported here.
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