Planetary Collision Seeded Elements for Life on Earth, Study Says

An artist's depiction of two planets colliding. Researchers believe that 4.4 billion years ago, the Earth was involved in a similar collision that seeded the chemical conditions necessary for life to form. (Photo: Pavel Gabzdyl/Shutterstock)

A fortuitous collision with a planetary body billions of years ago likely seeded the volatile elements necessary for life to rise on Earth. That's the conclusion from a group of Rice University researchers, who add that the celestial cataclysm was also directly responsible for the formation of Earth's moon.

"From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted," Rajdeep Dasgupta, co-author of the new study, said in a statement. "But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence."

An illustration showing the theorized collision between a Mars-sized planet and a young Earth.
An illustration showing the theorized collision between a Mars-sized planet and a young Earth. (Photo: Image courtesy of Rajdeep Dasgupta)

According to the researchers, a Mars-sized planet with a sulfur-rich core collided with our young Earth roughly 4.4 billion years ago, violently injecting mass quantities of carbon, nitrogen, sulfur, hydrogen and other life-essential elements into its crust. The vast debris thrown into orbit from this collision eventually coalesced to form the moon.

One billion simulations

To support their theory, the researchers ran a series of high temperature and pressure experiments mimicking impact conditions. From these results, they then crafted a computer simulation and ran 1 billion scenarios to find the most likely source of Earth's volatiles.

"What we found is that all the evidence — isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulfur in the bulk silicate Earth — are consistent with a moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulfur-rich core," lead study author Damanveer Grewal said.

While the conclusions reached by the study are insightful into the Earth's early transformation into a habitable world, they also shed light on how life might form elsewhere in the universe.

"This study suggests that a rocky, Earth-like planet gets more chances to acquire life-essential elements if it forms and grows from giant impacts with planets that have sampled different building blocks, perhaps from different parts of a protoplanetary disk," Dasgupta added.

In an interview with Gizmodo, the Rice University team says they'll next pursue steps to merge their geochemical models with new ones exploring the physical and dynamic processes of such a collision.

You can read the full study in the journal Science Advances.