Using precise measurements of krypton isotopes, UC Davis researchers prove that volatile organic compounds were incorporated into the Earth earlier than they thought
By MONICA MANMADKAR — science@theaggie.org
According to a new study published in Nature by UC Davis researchers, krypton (Kr) isotopes provide better insight into how, when and where carbon, nitrogen and water were brought to Earth. The study of these volatile organic compounds is an extremely important component of understanding Earth’s history and, by extension, the history of other planets.
Pulling these isotopes together from the Galápagos Islands, researchers Sandrine Péron and Sujoy Mukhopadhyay analyzed these isotopes for chemical fingerprints. According to the study, since krypton is composed of both meteoritic and atmospheric isotopes, this element can tell us a lot about Earth’s history and how its volatile elements like carbon, nitrogen and water initially developed.
“This study will allow [researchers] to better understand how Earth came to be and more importantly when these volatile elements developed in Earth’s history,” said Sandrine Péron, the lead author of the study and a current Marie Skłodowska-Curie Actions Fellow at ETH Zürich in Switzerland.
Péron conducted the research at UC Davis as a postdoctoral fellow working with Professor in the Department of Earth and Planetary Sciences Sujoy Mukhopadhyay. She described how the deep mantle krypton remains unchanged from the moon’s formation, which is why the isotopes can be used to deduce when volatile compounds came to Earth. The volcanic spots at the Galápagos Islands pull magma from the mantle, which is near the Earth’s iron core. Collecting the lava plumes themselves, researchers can use this magma to extract krypton isotopes. However, even with the lava, researchers are only able to collect a few million atoms of the most abundant krypton isotopes.
“Since the process of deducing their impact poses a challenge, [Péron] was able to come up with a better method for measuring the mantle krypton with mass spectrometry,” Mukhopadhyay said. “[She] was able to concentrate the krypton from rock samples where the samples would be void of air contamination and separated from argon and xenon.”
Péron continued to explain how their study was the first one to exactly calculate all krypton isotopes, including the rarest krypton isotopes, Kr-78 and Kr-80. Using these isotopes like a fingerprint, the researchers hoped to find where the volatile elements and compounds initially arose from the asteroid belt, the inner solar system or somewhere else.
“These isotopes are basically acting as the DNA in terms of their lineage, [and are answering questions like] where did these elements come from and which bodies delivered these elements that are essential for life,” Mukhopadhyay said.
The researchers soon discovered that the isotopes’ fingerprints contained traces of primitive, carbon-rich meteorites which originated from very early in Earth’s history.
This reveals two novel discoveries, Péron said. Firstly, although the isotopes show that the volatile elements arose very early in Earth’s history, not all of the isotopes were accounted for in the known meteorites. Secondly, the researchers found that the ratio of deep mantle krypton doesn’t match the atmospheric krypton isotope levels, which means that some of the ones in the atmosphere were delivered during the moon formation. If not, then the ratio for the deep mantle krypton and the atmospheric one would be the same, Péron explained.
Keeping this research in mind, Mukhopadhyay’s lab hopes to continue answering questions about why the fingerprint of krypton in the Earth’s atmosphere is different from the deep mantle and how representative the study’s measurements are of the entire interior of the Earth’s mantle.
Written by: Monica Manmadkar — science@theaggie.org
