Most of the essential parts of the earth for life – including most of you carbon and nitrogen – probably came from another planet.
Earth probably got the bulk of its coal, nitrogen and other vital volatile elements from the planet collision that created the moon more than 4.4 billion years ago, according to a new study by Rice University Petrologists in the journal Science Advances .
"From studies of primitive meteorites, scientists have long known that the earth and other rocky planets in the inner solar system are volatile depleted," says study author Rajdeep Dasgupta. "But the timing and mechanism of volatile delivery have been discussed hotly. Our is the first scenario that can explain the timing and delivery in a manner consistent with any geochemical evidence. "The evidence was compiled from a combination of high temperature high pressure experiments in Dasguptas laboratory, which specializes in studying geochemical reactions that take place deep in a planet under intense heat and pressure.
In a series of experiments, study authors and graduate students Damanveer Grewal gathered evidence to test a long-lasting theory that the Earth's volatiles emerged from a collision with an embryonic planet that had a sulfur-rich nucleus. [1
"The core does not interact with the rest of the earth, but everything above it, m. , the crust, the hydrosphere and the atmosphere are all connected, "said Grewal r between them. "
A long-standing idea of how the Earth gained its volatile subjects was the" late veneer "theory that volatile rich meteorites, remaining pieces of primordial matter from the outer solar system, arrived after the Earth's nucleus was formed. And while the isotopic signatures of the Earth's volatile matter match these primordial objects, known as carbonaceous condoms, the elemental ratio of carbon to nitrogen is off. The Earth's non-core material, which geologists call the bulk silicate earth, has about 40 parts of carbon dioxide to each part of nitrogen, about twice as much as the 20-1 ratio seen in carbonaceous condoms.
Grewal's experiments, which simulated high pressures and temperatures during nucleation, tested the idea that a sulfur-rich planet nucleus may exclude carbon or nitrogen or both, and leave much larger fractions of these elements in the bulk silicate compared to the soil. In a series of tests at a number of temperatures and pressures, Grewal investigated how much carbon and nitrogen it did in the core in three scenarios: no sulfur, 10 percent sulfur and 25 percent sulfur.
"Nitrogen was largely unaffected," he said. "It remained soluble in the alloys relative to silicates and only began to be excluded from the core during the highest sulfur concentration."
On the other hand, coal was significantly less soluble in alloys with intermediate sulfur concentrations and sulfur-rich alloys took up about 10 times less carbon by weight than sulfur-free alloys.
Using this information, along with known conditions and concentrations of elements both on earth and in non-terrestrial bodies, Dasgupta, Grewal and Rice postdoctoral researcher Chenguang Sun designed a computer simulation to find the most likely scenario that created the Earth's fleeting substances. Finding the answer involved changing the starting conditions, running about 1 billion scenarios and comparing them to the known conditions in the solar system today.
"What we found is that all the evidence – isotopic signatures, the carbon-nitrogen ratio, and the total amounts of carbon, nitrogen and sulfur in the pulp silicate soil – are consistent with a multilayer impact involving a volatile bearing planet in Mars with a sulfur-rich nucleus," Grewal.
Dasgupta, the main researcher on a NASA-funded effort called CLEVER Planets, exploring how vital elements can get together on distant rocky planets, says better understanding of the essential elements of earth's life has consequences beyond our solar system.
This study suggests that a rocky, earth-like planet is more likely to acquire vital elements if it is formed and grows from large effects with planets that have assembled different building blocks, perhaps from different parts of a protoplanetic disk, Dasgupta says.
"This removes some limit conditions," he said. "It shows that vital refugees can reach the surface of the planet, even though they were produced on planetary bodies that underwent nuclear formation under very different conditions."
Dasgupta said that it does not seem like the earth's bulk silicate, on its own could have achieved the vital volatile budgets that produced our biosphere, atmosphere and hydrosphere.
"That means we can broaden our search for pathways leading to volatile elements coming together on a planet to support life as we know it."