Asteroids hit Earth ten times earlier than thought
The early Earth collided with many asteroids 3.5-2.5 billion years ago, during this period the number of collisions could have been ten times higher than previously thought, an international research team found that such a large number of collisions is slower than the accumulation of oxygen in the atmosphere .
The authors of the study, described in the scientific journal Nature Geoscience, examined ancient asteroid remnants and modeled their impacts. These new models will help scientists understand more accurately when our planet began to turn into Earth as we know it today, read the PhysOrg science knowledge news portal.
“Unbound oxygen in the atmosphere is vital for all living things that produce energy by breathing. We probably wouldn’t exist,” said Nadia Drapon, a Harvard University researcher in Earth and Planetary Sciences.
The higher collision number indicates a planet colliding with an asteroid approximately every 15 million years.
The researchers analyzed ancient evidence, called impact balls, that formed when a large asteroid or comet collided with the planet. The energy released by the collision melted and the crustal rocks evaporated. Small balls of molten rock re-anchored, returned to Earth as sand-sized particles, and re-incorporated into the Earth’s crust. These ancient features are hard to find because they form very narrow layers in the rocks. However, over the past few years, we’ve found evidence of a number of effects that we didn’t know about before.
These new collision domains have increased the number of early Earth collisions known to date. This allowed the researchers to update their collision models and discover that they had reduced the number of asteroid collisions. Then they modeled how the effects would affect the atmosphere.
It has been found that the cumulative effect of a collision with a celestial body greater than nine kilometers results in a reduction in oxygen as it removes most of the oxygen from the atmosphere.Their results are consistent with geological records showing that while oxygen levels in the atmosphere changed, they were relatively low in antiquity. Most of the oldest rocks on the Earth’s surface come from antiquity (four billion to two and a half billion years ago). These rocks are known from Greenland, the Canadian Shield, Western Australia, and South Africa. The first continents also developed in the shadow of antiquity. (MTI)