Earth was hit by a Mercury-like body early in its history, study finds
Young planet's collision with a Mercury-like body may have led to creation of the magnetic field that protects life from the deadly radiation of space
A Mercury-like body smashed into a young earth and gave our planet's core the radioactive elements necessary to generate a magnetic field, two Oxford geochemists say.
Without that magnetic field, there would be no shield to protect us from the onslaught of radiation constantly bombarding earth from space, making the existence of life as we know it impossible, scientists say.
The study, published in the journal Nature, offers insight into how earth's magnetic field - and, perhaps, the moon - came to be.
Our planet was thought to have formed from small rocky bodies like the ones in the asteroid belt today, study co-author Bernard Wood, a geochemist at the University of Oxford in the UK, said. It was a theory that fitted quite well with what had been studied on earth, though it was not a perfect fit, he said.
"That sort of roughly works, but there are all kinds of little questions that don't quite work," Wood said, "and one of them is, what is the energy source that drives the earth's magnetic field?"
Here's the problem. To drive earth's magnetic field, you need radioactive elements such as potassium, thorium or uranium - elements that give off heat as they decay - to also be in the planet's churning iron core. Those elements love getting together with oxygen, making oxides - but oxides are really light and would float toward the planet's surface; they wouldn't be heavy enough to stay in the core. These elements also hate getting together with iron.