Scientists have long understood that Earth’s geological evolution is influenced by extraterrestrial factors. This includes the distribution of water, volatiles, and minerals from asteroids and comets within the Solar System, precious metals from nearby supernovae, and perturbances from passing stars. Basically, galactic events over the past few billion years have left their mark on Earth. According to new research from Curtin University, the structural evolution of the Milky Way galaxy also had an effect on the evolution of Earth’s crust, as evidenced by ancient crystals beneath the surface.
The research was conducted by Christopher L Kirkland, a Geology Professor and a member of the Timescales of Mineral Systems Group at Curtin University, and Patrick James Sutton, a Senior Lecturer in Astrophysics from the School of Engineering and Physical Sciences at the University of Lincoln. The study that details their findings was published yesterday (Sept. 19th, 2025) in the journal Physical Review Research. As they state in their paper, Earth’s crust was shaped by the impact of meteorites as it orbited the center of the Milky Way.
This challenges previous theories that held that Earth’s crust was shaped solely through internal processes. They further argue that the chemistry of zircon crystals may have captured the rhythm of these impacts, providing evidence that Earth’s ancient geological record is linked with the large-scale structure of the Milky Way. As Prof. Kirkland explained in a Curtin University release:
Tiny, durable minerals called zircon crystals provided a unique archive of Earth’s interaction with the galaxy. By looking at chemical changes in zircon crystals and comparing them with maps of gas in the Milky Way, we saw the changes line up with times that our Solar System passed through the galaxy’s spiral arms, which are densely packed with stars and gas. In these crowded regions, extra gravitational forces may have disturbed icy comets at the edge of our Solar System, knocking some onto paths that sent them crashing into Earth. The resulting impacts released enormous energy, melting parts of Earth’s surface and producing more complex magmas, especially when interacting with water-rich environments.
Their findings show that Earth’s geological evolution cannot be understood in isolation and suggest that astrophysical processes on a galactic scale have directly influenced geological history. They also hint at future opportunities for research where geology can be directly connected with astronomy. “It suggests that astrophysical processes on the scale of the Milky Way may have directly influenced the continents beneath our feet and the conditions that made life possible, ushering in a new era of astro-geological science,” concluded Prof. Kirkland.
Further Reading: Curtin University, Physical Review Research