Late Collision with Theia May Have Delivered Water, Making Earth Habitable
WASHINGTON – New research published in Science Advances suggests a late collision with a Mars-sized object named theia approximately 4.5 billion years ago was crucial in delivering water to Earth, transforming the planet from a dry, rocky world into one capable of supporting life. The study reframes understanding of planetary habitability, emphasizing the importance of timing and impact history alongside orbital location.
Scientists have long theorized that Earth formed rapidly from its initial building blocks, resulting in a “dry start.” earlier attempts to explain Earth’s water through additions from the inner solar system have proven inconsistent with measurements. The new research posits that a significant influx of volatiles – compounds like water – came later, perhaps through an impact with Theia.
Theia is believed to have collided with the young Earth, creating the Moon. If Theia originated in a colder, volatile-rich region of the solar system, the impact could have delivered a substantial amount of water and other essential elements. This scenario aligns with existing data showing a fast initial Earth formation followed by a later alteration of the planet’s surface environment.
“Timing, source regions, and impact histories determine whether a planet develops oceans and an atmosphere capable of supporting biology,” the research indicates. Habitability, thus, isn’t solely steadfast by a planet’s position within a star’s habitable zone, but also by how and when it acquires its volatiles.
Researchers acknowledge open questions remain regarding the giant impact event. Further modeling is needed to fully explain the physical and chemical properties of both Earth and the Moon, including their shared isotope signatures.
“So far, this collision event is insufficiently understood. Models are needed that can fully explain not only the physical properties of the Earth and moon, but also their chemical composition and isotope signatures,” concludes researcher Kruttasch.
The study underscores that even planets orbiting within habitable zones can remain inhospitable without a late delivery of water, highlighting the delicate balance of factors required for a planet to become “wet” and potentially harbor life.
