In a groundbreaking study, researchers have discovered that ice on ancient asteroids, such as Ryugu, may have played a pivotal role in the development of life on Earth. By analyzing asteroid samples returned from the Japanese Space Agency’s (JAXA) Hayabusa2 mission, scientists found evidence that freeze-thaw cycles of ice within these asteroids could have been instrumental in delivering water and organic materials to Earth billions of years ago.
The Role of Water in Asteroid Evolution
Led by Dr. Matt Genge from Imperial College London’s Department of Earth Science and Engineering, in collaboration with the Natural History Museum, the University of Kent, and JAXA, the research team uncovered fractures in the rocks from asteroid Ryugu, which appear to have been caused by the repeated freezing and melting of ice. These freeze-thaw cycles not only fractured the asteroid’s structure but also delivered crucial water and minerals, potentially kickstarting the processes that led to the emergence of life on Earth.
The fractures were filled with clay and sulfide minerals, which are typically formed in the presence of water. This suggests that as the asteroid’s ice expanded and contracted, it fractured the rock, allowing water to permeate its core. These findings point to a crucial role played by water in altering the composition of asteroids, making them fertile carriers of life-enabling materials.
How Freeze-Thaw Cycles Led to Life on Earth
Dr. Genge explained: “Our findings suggest that the repeated melting and freezing of ice on asteroids may have helped life form on Earth. The pressure exerted by growing ice is enough to fracture asteroids to their core, allowing water to interact with minerals and create organic matter.”
This process would have allowed water and essential organic materials to spread throughout the asteroid, which later delivered these life-building blocks to Earth. As asteroids like Ryugu collided with early Earth, they potentially seeded the planet’s oceans and enriched it with the necessary components for life to emerge.
The team also concluded that while asteroid collisions can cause fracturing, the distinctive freeze-thaw fracture shapes seen in Ryugu samples indicate that this process, specifically driven by ice, played a more significant role in delivering these essential materials to Earth.
Deciphering Ryugu’s Tiny Fractures
To examine the asteroid’s samples, the researchers used X-ray Computed Tomography (XCT), a powerful imaging technique similar to medical CT scans but designed for analyzing rocks. This allowed the team to observe the 3D structure of millimeter-sized pieces of Ryugu and identify the thin fractures caused by the freeze-thaw cycles.
In addition to the fractures, they also found framboidal magnetite, spherical crystals of magnetic iron oxide, which further pointed to the presence of water. The curved shapes and cusps of these fractures led researchers to conclude that ice was the key driver behind Ryugu’s geological evolution.
Experiments with ice grains embedded in clay replicated these distinctive fracture patterns, confirming that it was the expansion and contraction of ice that broke apart the asteroid’s rocks and allowed water to play a transformative role in their composition.
The Implications for Life on Earth
Dr. Genge’s findings offer a fascinating glimpse into how life on Earth may have originated. “It is the fracturing of asteroids by freeze-thaw cycles that ensured asteroids were thoroughly altered by water. Without it, life-giving materials may have been far rarer,” said Genge.
The study proposes that these freeze-thaw processes on asteroids, combined with their collisions with Earth, may have seeded the planet with the organic and mineral-rich materials necessary for life. This discovery adds a new dimension to our understanding of how water and organic matter were delivered to Earth, making asteroids not just cosmic debris, but key players in the development of life.
Conclusion: Cosmic Ice, Key to Life’s Origins?
The research, published in Nature Astronomy, offers compelling evidence that ice on asteroids like Ryugu played a pivotal role in shaping the Solar System’s geology and delivering life-essential materials to Earth. As scientists continue to study these ancient space rocks, we gain a deeper understanding of the cosmic processes that may have led to the emergence of life on our planet.
Reference: “Evidence from 162173 Ryugu for the influence of freeze-thaw on the hydration of asteroids” by Matthew J. Genge et al., 26 September 2024, Nature Astronomy.
