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Collision between young Earth and Mars-sized planet might be why we’re all here today

Published Jan 23rd, 2019 7:06PM EST

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Humans have tamed (or utterly destroyed) much of the planet in our brief time here, but there’s still plenty we don’t know about Earth’s history. How the early Earth formed, how its abundance of various chemicals and elements got here, and what shaped its future are things scientists have been trying to explain for a long time, and a new theory has emerged that may finally fit.

In a new study published in Science Advances, researchers from Rice University propose a comprehensive theory that not only accounts for Earth’s incredible, life-giving resources, but even helps to explain how Earth’s moon formed. It all begins with a big crash.

One of the biggest challenges in explaining the early evolution of the Earth is figuring out where many of its elements came from. Our planet’s carbon, nitrogen, hydrogen, and other “volatiles” aren’t thought to have originated on Earth but were rather delivered here by some unknown force.

“From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted,” Rice University’s Rajdeep Dasgupta said in a statement. “But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence.”

The team tested various possible scenarios, including collisions between the Earth and other large worlds, or even storms of meteorites. Ultimately their simulations and calculations led them to the conclusion that the most likely series of events involved an impact between Earth and a sulfur-packed planet approximately the size of Mars.

“What we found is that all the evidence — isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulfur in the bulk silicate Earth — are consistent with a moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulfur-rich core,” Damanveer Grewal, lead author of the work, explains.

If such a collision did indeed occur billions of years ago in Earth’s history, that delivery of vital elements, in addition to ejecting enough mass to create the Moon, could have been a key to the eventual formation of life on the planet.

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