Asteroid Bombardment Delayed Earth's First Continents for 500 Million Years, Science Study Finds
Updated
Updated · ScienceAlert · Jun 25
Asteroid Bombardment Delayed Earth's First Continents for 500 Million Years, Science Study Finds
2 articles · Updated · ScienceAlert · Jun 25
Summary
A 500 million-year barrage of asteroids may have stopped Earth from forming stable continents during the Hadean eon, according to a new Science study led by Curtin University geologist Tim Johnson.
Modeling in the study suggests impact heat rivaled or even exceeded Earth's internal heat budget, leaving shallow crust partially molten and repeatedly remelting any early crust before it could stiffen into long-lived plates.
Lunar impact scars, along with records from Mercury, Mars, asteroids and meteorites, were used to reconstruct how heavily early Earth was hit and to estimate how that energy would have altered the crust and mantle.
The team argues crust could cool and thicken only after bombardment eased in the early Archean, potentially setting the stage for plate tectonics and offering an explanation for why rocks older than 4 billion years are so scarce.
Earth’s first 500 million years of rock are missing. Was our planet’s history erased by a cosmic bombardment?
Did the asteroid storms that melted Earth’s crust also create the perfect conditions for life to emerge?
The 500-Million-Year Delay: Asteroid Impacts, Continental Formation, and the Origins of Life on Early Earth
Overview
During the Hadean eon, Earth experienced intense asteroid bombardment that kept its early crust in a constant state of flux. As crustal fragments began to solidify, they were quickly remelted and recycled back into the planet’s hot interior. This process left the crust weak and partially molten, which prevented the long-term aggregation needed for stable continent formation. As a result, the emergence of Earth’s continents was significantly delayed—by up to 500 million years. This period, known as the Late Heavy Bombardment, played a crucial role in shaping the planet’s early geological evolution.