The ‘young’ Earth may have swallowed a Mercury-like planet billions of years ago, a collision which providing our planet’s layers and generate Earth’s magnetic field creating the perfect conditions required for life to flourish.
Current models suggests that our planet formed 4.6 billion years ago from a giant, rotating cloud of dust and gas. Scientists believe that the Earth and other rocky planets formed from smaller asteroid-sized bodies like the ones in the asteroid belt today, so, the meteorites are samples of Earth’s building blocks.
However, current models cannot explain why Earth’s crust and mantle contain a higher ratio of samarium (Sm) and neodymium (Nd) than seen in most meteorites.
Now, the new study suggests that if early Earth engulfed a sulfur-rich body like Mercury then this could explain the anomaly. The research could also help solve another mystery: how Earth’s protective magnetic shield has lasted for billions of years.
A Mercury-like body added to Earth during accretion would solve two important problems — that is, kill two birds with one stone.
Oxford University researchers Bernard Wood and the study co-author said.
We show here that addition of a reduced Mercury-like body (or, alternatively, an enstatite-chondrite-like body) rich in sulfur to the early Earth would generate a superchondritic Sm/Nd in the mantle and an 142Nd/144Nd anomaly of approximately +14 parts per million relative to chondrite. In addition, the sulfur-rich core would partition uranium strongly and thorium slightly, supplying a substantial part of the ‘missing’ heat source for the geodynamo.
Geochemist Richard Carlson said:
As with any new idea, there will be a lot of tests that it will need to pass first before it becomes convincing.
One of the strengths of modern geochemistry is that we have reasonably precise data for the abundance of almost every element in the periodic table, at least in Earth’s outer layers. If core formation under the reducing conditions explored by the Wohlers and Wood experiments can reproduce the whole pattern of element abundances in the silicate Earth, that would give the model more support.
Dr. Carlson wrote:
The energy source that drives the generation of the Earth’s magnetic field in the core has long been a topic of discussion.