Early Earth gobbled up Mercury-like body

The early Earth absorbed a planetary body similar to Mercury, according to a new study that also helps explain how our planet's magnetic field has lasted for billions of years.
Scientists believe Earth formed around the same time as the Sun and the rest of the solar system about 4.6 billion years ago from a giant, rotating cloud of gas and dust.
Earth and the other rocky planets coalesced from smaller asteroid-sized bodies that stuck together to form ever-larger chunks of rock.
The meteorites that crash into Earth are usually thought to represent the building blocks that the planet grew from.

However, Earth's crust and mantle puzzlingly have a higher proportion of the element samarium to the element neodymium than seen in most meteorites.
New experiments suggest that the addition of a sulfur-rich Mercury-like body to the early Earth could explain this anomaly.

Bernard Wood, a geochemist at the University of Oxford and colleagues performed experiments with samples of material under conditions mimicking those at which Earth formed - temperatures between 1,400 and 1,640 degrees Celsius and pressures of 1.5 gigapascals.
The samples of material the scientists tested contained traces of elements such as samarium, neodymium, and uranium. These elements are normally chemically attracted to silicate rock, which makes up most of the Earth's crust and mantle.

They do not usually dissolve in iron sulfide, which makes up a significant fraction of Earth's outer core.
The scientists found that if the early Earth incorporated a rocky body like Mercury, which is high in sulfur, this could make samarium and neodymium dissolve better in iron sulfide.
This in turn would make samarium and neodymium more likely to sink down toward Earth's core, 'Space.Com' reported.
However, samarium is more attracted to silicate rock than neodymium is. This would have made samarium a bit less likely to sink downward, which could explain why there is a greater proportion of samarium to neodymium in Earth's crust and mantle.

The experiments could also help solve a mystery concerning Earth's magnetic field.
Earth's magnetic field results from churning metal in the planet's outer core, but it was uncertain how Earth's core could have remained molten for so long.
The new experiments found that if the early Earth engulfed a sulfur-rich Mercury-like body, uranium could have dissolved better in iron sulfide.
This in turn would help uranium sink toward Earth's core. Uranium is a radioactive element that generates heat, which could have kept Earth's core molten.