Our planet's early gasses may have been knocked out of whack by a bombardment of tens of thousands of small space rocks, according to a new study published in the journal Icarus.
The Earth's first atmosphere wasn't like the one we have today: It's actually been destroyed and recreated at least twice in the past 4 billion years. But what went down when the atmosphere got the boot? Some have theorized that a single, massive impact might have done the trick. But now MIT researchers say that a large number of small impacts are more likely to have pushed the atmosphere out into space.
According to their mathematical analysis, the force of a single impact would have to be huge to displace Earth's atmosphere. The space body hurling into it would have to be nearly as large as the planet itself. In this scenario, a planet about the size of Mars could push a shock wave through Earth's interior, which would cause something like massive earthquakes all over the planet at the same time. The planet's violent jiggling would transfer out toward the atmosphere, and could push those gases into space.
But by working in tandem, little rocks may have had a more efficient go of it.
Much smaller space debris would cause explosions when they hit Earth, releasing plumes of gas. In some cases, these rocks might cause enough disturbance to push away the atmosphere directly above their impact site.
According to the research team's mathematical analysis, a real flurry of these small impacts -- tens of thousands of them during a short period of time -- could have completely ejected the atmosphere. And it's likely that Earth saw that kind of bombardment at the time the moon was formed, when many space rocks were colliding to form moons and planets.
“For sure, we did have all these smaller impactors back then,” study author Hilke Schlichting, an assistant professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences, said in a statement. “One small impact cannot get rid of most of the atmosphere, but collectively, they’re much more efficient than giant impacts, and could easily eject all the Earth’s atmosphere.”
And those tiny space rocks may have also solved another mystery: How the planet got its atmosphere back after losing it. Many of these rocks would have melted upon impact, releasing their own molecules back into the planet's atmosphere.