A massive cosmic collision 4.4 billion years ago created the moon but also imparted Earth with most of the essential ingredients for life, researchers from Rice University in Texas found. Following a series of high-temperature, high-pressure experiments designed to mimic the conditions deep under the surface, the team of petrologists concluded a collision with a planet similar in size to Mars was probably responsible for the carbon and nitrogen on our planet. The study noted that Earth’s core does not have evidence of carbon, nitrogen and sulphur, leading scientists to believe that the elements arrive on Earth from an interstellar body.
Lead author Damanveer Grewal said: “What we found is that all the evidence – isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulphur in the bulk silicate Earth – are consistent with a moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulphur-rich core.”
The sulphur content of the donor planet’s core is important because of the puzzling array of experimental evidence about the carbon, nitrogen and sulphur that exist in all parts of the Earth other than the core.
Mr Grewal said: “The core doesn’t interact with the rest of Earth, but everything above it, the mantle, the crust, the hydrosphere and the atmosphere, are all connected.
“Material cycles between them.”
Co-author Rajdeep Dasgupta said: “From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted. 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 the geochemical evidence.”
The study was published in Science Advances.
Scientists have previously hypothesised that Earth is made up of material from two planets – the early Earth and a second, smaller planet dubbed Theia.
Initially it was believed that the Moon was formed when Theia skimmed the Earth and broke up.
But a 2016 study by the University of California found a smaller planet actually collided with the Earth shortly after it was formed 4.5 billion years ago.
The powerful collision as Theia crashed into the early Earth sent material flying into space which would later form into the Moon.
Researchers analysed the contents of Moon rocks brought back by the Apollo 12, 15 and 17 missions and compared them with volcanic rocks from the Earth.
They found oxygen isotopes trapped within the material were the same in both samples – meaning the material on both bodies had come from the same source.
Edward Young, lead author of the study, said: “We don’t see any difference between the Earth’s and the Moon’s oxygen isotopes; they’re indistinguishable.
“Theia was thoroughly mixed into both the Earth and the Moon, and evenly dispersed between them.
“This explains why we don’t see a different signature of Theia in the Moon versus the Earth.”