Meteorites falling to Earth could form continents, scientists say

(ORDO NEWS) — Scientists believe that roughly four billion years ago, the inner part of the solar system was destroyed by massive space rocks.

Earth is the only known planet to have continents, however, how exactly these distinct landmasses came into existence remains a mystery.

One of the most exciting theories suggests that a flurry of giant impacts on the young Earth led to the formation of stable continental pieces called cratons, and now researchers have provided the strongest evidence for this hypothesis.

“By examining tiny crystals of the mineral zircon in rocks from Western Australia’s Pilbara Craton, which is the best-preserved remnant of the Earth’s ancient crust, we found evidence of giant meteorite impacts,” said study author Dr. Tim Johnson.

“Studying the composition of oxygen isotopes in these zircon crystals revealed a ‘downward’ process, starting with the melting of rocks near the surface and moving deeper, which can be triggered by giant meteorite impacts.”

Previously, researchers have speculated that Earth’s cratons may have formed during the Late Heavy Bombardment, when the inner Solar System was hit by a disproportionate amount of asteroids.

Based on the age and distribution of craters on the Moon, scientists believe that the rate of fall decreased significantly between 3.9 and 3.5 billion years ago.

“The age of the oldest continental crust in most cratons also spans a time period of 3.9 to 3.5 [billion years ago].

The question arises whether this is a coincidence or there is a definite connection, ”the authors of the study write in the journal Nature.

The scientists were looking for changes in the density of a specific isotope of oxygen, called oxygen-18, in the Pilbara craton.

Previous studies of large impact craters have shown that such events cause massive melting of the shallow mantle, resulting in a decrease in oxygen-18 compared to lighter isotopes.

The analysis showed that the Pilbara crater formed in three stages, the first of which occurred between 3.6 and 3.4 billion years ago.

The zircon crystals found in this layer were isotopically light, indicating that they may have “crystallized after an initial giant impact that eventually formed the Pilbara Craton.”

According to the authors of the study, the collision that caused this event would have included a massive space rock measuring “from a few tens to hundreds of kilometers in diameter.”

It is noteworthy that a similar isotopic pattern can be seen in some other cratons on Earth, including the Yilgarn craton in Western Australia.

“Our study provides the first strong evidence that the processes that eventually formed the continents began with giant meteorite impacts similar to those that led to the extinction of the dinosaurs, but which happened billions of years earlier,” says Johnson.

“Data relating to other areas of ancient continental crust on Earth appear to show patterns similar to those found in Western Australia.

We would like to test our results on these ancient rocks to see how broadly applicable our model is.”


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