Where Did Earth's Water Come From? New Exoplanetary Model Sheds Light

Tuesday - June 13 2023, 20:38 UTC - 1 year ago

Newly discovered exoplanets have helped shape a novel model for the origin of Earth's signature features such as its abundance of water, demonstrating that interactions between the magma ocean and a molecular hydrogen proto-atmosphere could have contributed to the planet's composition and overall oxidized state.

Newly discovered exoplanets contribute to the development of a novel model that offers potential explanations for the origin of some of Earth’s signature features, such as its abundance of water.

New research from Carnegie Science’s Anat Shahar, along with UCLA’s Edward Young and Hilke Schlichting, suggests that the water found on our planet may have originated from the interplay between the hydrogen-rich atmospheres and molten lava seas of the early planetary bodies that constituted the early stages of Earth’s formation. Their research, which could shed light on the origin of some of Earth’s defining characteristics, was recently published in the journal Nature.

Historically, our understanding of planetary formation was largely influenced by the example of our own Solar System. Even though the genesis of gas giants such as Jupiter and Saturn still sparks discussions among scientists, there is a broad consensus that Earth and other terrestrial planets were formed from the accumulation of dust and gas that once orbited around our Sun in its youth.

As increasingly larger objects crashed into each other, the baby planetesimals that eventually formed Earth grew both larger and hotter, melting into a vast magma ocean due to the heat of collisions and radioactive elements. Over time, as the planet cooled, the densest material sank inward, separating Earth into three distinct layers—the metallic core, and the rocky, silicate mantle and crust.

However, the explosion of exoplanet research over the past decade informed a new approach to modeling the Earth’s embryonic state.

"Exoplanet discoveries have given us a much greater appreciation of how common it is for just-formed planets to be surrounded by atmospheres that are rich in molecular hydrogen, H2, during their first several million years of growth," Shahar explained. "Eventually these hydrogen envelopes dissipate, but they leave their fingerprints on the young planet’s composition." .

Using this information, the researchers developed new models for Earth’s formation and evolution to see if our home planet’s distinct chemical traits could be replicated.

Using a newly developed model, the Carnegie and UCLA researchers were able to demonstrate that early in Earth’s existence, interactions between the magma ocean and a molecular hydrogen proto-atmosphere could have given rise to some of Earth’s signature features, such as its abundance of water and its overall oxidized state.

The researchers used mathematical modeling to explore the exchange of materials between molecular hydrogen atmospheres and magma oceans by looking at 25 different compounds and 18 different types of reactions—complex enough to yield valuable data about Earth’s possible formative history, but simple enough to interpret fully.

Interactions between the magma ocean and the atmosphere in their simulated baby Earth resulted in the movement of large masses of hydrogen into the metallic core, the oxidation of the mantle, and the production of large quantities of water.

Even if all of the rocky material that collided to form the growing planet was completely dry, these interactions between the molecula hydrogen atmosphere and the magma ocean could have been enough to create a significant amount of water that would later escape to the surface.