Nitrogen Accretion Depends on Style of Planet Formation

May 12, 2021 | Daily Space, Exoplanets

Nitrogen Accretion Depends on Style of Planet Formation
IMAGE: Nitrogen-bearing, Earth-like planets can be formed if their feedstock material grows quickly to around moon- and Mars-sized planetary embryos before separating into core-mantle-crust-atmosphere, according to Rice University scientists. If metal-silicate differentiation is faster than the growth of planetary embryo-sized bodies, then solid reservoirs fail to retain much nitrogen and planets growing from such feedstock become extremely nitrogen-poor. CREDIT: Amrita P. Vyas

It’s not often that we get to talk about experimental research into exoplanets and astrobiology. In new research published in Nature Geoscience, researchers used the high-pressure lab at Rice University to understand how nitrogen is attracted to metallic planetary cores. Lead author Damanveer Grewal explains: We simulated high pressure-temperature conditions by subjecting a mixture of nitrogen-bearing metal and silicate powders to nearly 30,000 times the atmospheric pressure and heating them beyond their melting points. Small metallic blobs embedded in the silicate glasses of the recovered samples were the respective analogs of protoplanetary cores and mantles.

By analyzing the data, the team was able to model how nitrogen gets distributed between the atmosphere, mantle, and core. Grewal continues: We realized that fractionation of nitrogen between all these reservoirs is very sensitive to the size of the body. Using this idea, we could calculate how nitrogen would have separated between different reservoirs of protoplanetary bodies through time to finally build a habitable planet like Earth.

Basically, to get the amount of nitrogen we have here on Earth, which life here needs to survive, your planet needs to grow more quickly than it differentiates out into crust, mantle, and core. Following that path leads to the accretion of more nitrogen, which apparently loves the metallic liquid that forms the cores of rocky planets. This work, of course, can be applied to exoplanets as well, if we can figure out their composition.

More Information

Rice University press release

Rates of protoplanetary accretion and differentiation set nitrogen budget of rocky planets,” Damanveer S. Grewal, Rajdeep Dasgupta, Taylor Hough, and Alexandra Farnell, 2021 May 10,  Nature Geoscience


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