Study suggests micrometeorites as key nitrogen source for primordial Earth

Study suggests micrometeorites as key nitrogen source for primordial Earth
by Riko Seibo
Kyoto, Japan (SPX) Dec 04, 2023

A recent study published in 'Nature Astronomy' reveals a novel understanding of how nitrogen, an essential component for life, may have been transported to Earth during its formative years. This research, involving an international team of scientists including members from the University of Hawai'i at Manoa, led by Kyoto University, points to micrometeorites as a likely source.

Micrometeorites, small extraterrestrial particles, are believed to originate from icy bodies in the outer Solar System. The study suggests that these micrometeorites could have played a crucial role in delivering nitrogen to the near-Earth region in the early days of the solar system. Nitrogen compounds, particularly ammonium salts, are known to be abundant in materials formed far from the sun. However, the mechanism of their transport to Earth's orbital region has remained unclear until now.

Hope Ishii, an affiliate faculty at the Hawai'i Institute of Geophysics and Planetology in the University of Hawai'i at Manoa's School of Ocean and Earth Science and Technology (SOEST) and a co-author of the study, remarked, "Our recent findings suggest the possibility that a greater amount of nitrogen compounds than previously recognized was transported near Earth, potentially serving as building blocks for life on our planet."

The research took a significant turn by examining samples from the asteroid Ryugu, brought back to Earth by the Japan Aerospace Exploration Agency's (JAXA) Hayabusa2 spacecraft in 2020. Ryugu, a small asteroid orbiting the sun, is notable for its carbon-rich composition and extensive space weathering due to micrometeorite impacts and solar ions.

Investigations into Ryugu samples using an electron microscope uncovered that the asteroid's surface is covered with iron nitride (Fe4N) minerals. Toru Matsumoto, the study's lead author and assistant professor at Kyoto University, explained, "We proposed that tiny meteorites, called micrometeorites, containing ammonia compounds were delivered from icy celestial bodies and collided with Ryugu. The micrometeorite collisions trigger chemical reactions on magnetite and lead to the formation of the iron nitride."

The formation of iron nitride on Ryugu's surface provided critical insights into the potential process of nitrogen transport to Earth. The iron nitride was observed on the surface of magnetite, a mineral made of iron and oxygen. The space environment, characterized by solar wind and micrometeorite impacts, causes oxygen loss from magnetite's surface, forming metallic iron, which then reacts with ammonia to synthesize iron nitride.

This discovery opens new avenues in understanding the early solar system's dynamics and the transportation of essential elements necessary for life. It underscores the importance of micrometeorites and their role in the chemical evolution of planets. As the research continues, it may further illuminate the origins of life on Earth and the potential for life-supporting conditions elsewhere in the universe.

Research Report:Influx of nitrogen-rich material from the outer Solar System indicated by iron nitride in Ryugu samples