Asteroid Ryugu's dust reveals nitrogen's slow concentration into complex molecules

A team led by Toru Matsumoto at Kyoto University found nitrogen-bearing compounds in the sample returned from the asteroid Ryugu. The study, published in Nature Astronomy, revealed that the sample contained ammonium trapped inside clay minerals, molecules containing carbon-nitrogen bonds, and crystals of sodium nitrate. All of these nitrogen compounds clustered around sodium carbonate, a mineral formed as the last of the asteroid's salty water either froze or evaporated away. The arrangement suggested that these nitrogen compounds survived for millions of years while water moved through Ryugu's parent body, growing more concentrated as the water disappeared. This concentration could have driven the kind of chemistry needed to build larger, more complex molecules.

The research shows that nitrogen, which is a key ingredient in the biomolecules that form the building blocks of life, is slowly concentrated into complex molecules through the process of water movement and mineral formation. The findings suggest that asteroids like Ryugu acted as slow-cooking chemical reactors, gradually concentrating nitrogen over vast stretches of time before delivering it to newly forming planets. This process could have supplied the very first building blocks for what would become life on Earth.

The study is based on analysis of samples returned from the Hayabusa2 mission, which collected pristine material from Ryugu. The results are consistent with similar findings from the OSIRIS-REx mission on Bennu, lending weight to the broader pattern of nitrogen concentration in asteroids. The findings provide new insights into the chemical evolution of the solar system and the potential role of asteroids in the origin of life.

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