Source: The Guardian

It could so easily have turned out differently. About 4.5bn years ago the Earth is believed to have collided with another planet, Theia, resulting in the formation of the moon. A more glancing blow might have resulted in a “hit and run” and a moon-less Earth; while a head-on collision may have blasted away much of Earth’s mantle, leaving no atmosphere. Instead it seems to have been something in between, which eroded between 10 and 60% of Earth’s atmosphere, but also left us with the moon.

Jacob Kegerreis, from Durham University, and colleagues used a supercomputer to simulate over 300 different kinds of impact and explore the possible outcomes when two rocky planets bash into each other. Their findings, published in The Astrophysical Journal Letters, revealed the atmospheric loss associated with the most plausible moon-forming impact scenarios, ranging from a 10% loss associated with a Mars-sized planet having a grazing (45°) and relatively slow collision with early Earth, to a 60% loss with a faster and more direct collision between two planets of more equal mass. “We hope this will help us understand the history of Earth’s atmosphere and perhaps narrow down the different ways the moon might have formed,” says Kegerreis.

Source: The Guardian