Did a planetary collision make this possible?
Yes, it formed the Moon and gave Earth its volatile elements, scientists say. Samantha Page reports.
The third rock from the Sun would be a lot rockier and a lot less lively if a carbon- and nitrogen-bearing planet the size of Mars hadn’t smashed into Earth more than 4.4. billion years ago, scientists say in a new paper.
A research team from Rice University in Texas, US, finds that most of the volatile elements that make life on Earth possible most likely came from a planetary collision – the same collision that created the Moon.
"What we found is that all the evidence – isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulfur in the bulk silicate Earth – are consistent with a Moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulfur-rich core," says Damanveer Grewal, lead author of a paper published in the journal Science Advances.
Grewal and his colleagues conducted a series of experiments in a specially designed lab for studying geochemical reactions under high-temperature, high-pressure scenarios. They found that colliding with a planet with a sulfur-rich core would leave more carbon in what is known as the bulk silicate Earth, the non-core part of the planet.
Determining how the Earth got its volatile elements has long puzzled scientists. One theory, known as the late-veneer theory, is that meteorites called carbonaceous chondrites brought volatiles after the Earth’s core was formed.
But the bulk silicate Earth has 20 times more carbon to nitrogen than the carbonaceous chondrites, drawing that theory into question.
“From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted," says co-author Rajdeep Dasgupta.
"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 of the geochemical evidence.”