Micrometeorite study indicates an abundance of CO2 in early atmosphere

By Annika Prom

In a hunt to discover what the early Earth looked like, a team in the earth and space sciences department found clues right beneath their feet. A recent study involving micrometeorites suggests that the early Earth’s atmosphere may have been rich in carbon dioxide (CO2).

Graduate student Owen Lehmer, the lead researcher, said this work supports the idea that CO2 is a “driver for life and habitability.”

“I think that [people] should care because everyone wants to know: How does life form?” Lehmer said. “Is it something that’s special to Earth?”

He chose to study micrometeorites, which are small meteors that measure a few micrometers across, roughly as thick as a strand of hair.

Micrometeorites are often embedded and well-preserved in the limestone of lake beds, making them like scientific time capsules. Using a weak acid solution, Lehmer dissolved the surrounding rock, used a magnet to extract iron, then sifted through the sediment to find micrometeorites in perfect spheres.

“The only things that really exist from 3.8 billion years ago onward are rocks, which can record interactions with atmospheres and with water,” Lehmer said. “That’s sort of our ticket into discovering what the early Earth was like. These micrometeorites provide a novel opportunity to study what the atmosphere might have been like.”

Lehmer led this research by creating a computer model that simulated the chemical reactions that possibly occurred as micrometeorites descended to Earth.

With each trial, Lehmer edited the amount of CO2 in the virtual atmosphere until the model yielded a micrometeorite population similar to what Lehmer has actually observed.

From a big picture perspective, these numbers may bring researchers closer to figuring out how life came to be.

“CO2 is really important for the formation and evolution of life and controlling the habitability of Earth-like planets in general,” Lehmer said. “A better understanding of that could really improve our understanding of numerous other processes … and help inform future work that’s trying to figure out how life started on the planet.”

Lehmer’s work is a continuation of related research conducted by the Australian Synchrotron and Imperial College in London. In that project, the group claimed that, due to composition of micrometeorites, the early Earth’s atmosphere likely contained significant amounts of oxygen.

Thus, Lehmer decided to explore an adjacent explanation that could also support the same findings. The atmosphere, alternatively, could have been rich in CO2. Due to the greenhouse effect, the atmosphere likely contained an abundant amount of CO2 to warm the Earth a couple billion years ago.

In the future, Lehmer plans to refine his model to use more measured quantities than assumed ones, like the reaction rates of substances at several thousand degrees. His step forward, he says, may help inform scientists of the role of CO2 in the creation and evolution of life.

“In order to know where to look for life, we would need to know the conditions under which life can exist and form, and so a better understanding of CO2 really can make that a possibility,” Lehmer said.

This article appeared on The Daily (University of Washington) website at http://www.dailyuw.com/science/article_46a745cc-7a26-11ea-957d-9f5f8e369cad.html