Chelyabinsk meteorite could have been involved in the collision that formed our moon

(ORDO NEWS) — A meteorite that exploded in the sky over Chelyabinsk in 2013 could also be involved in the collision of the Earth with a giant cosmic body that formed the Moon.

This discovery was made possible by a new way of dating rock collisions in space, based on microscopic analysis of minerals in meteorites. While further research is needed, this method could give us a new tool to understand the early history of the solar system and how it evolved into its current form.

“The age of the meteorite is often controversial,” said geologist Craig Walton of the University of Cambridge in the UK.

“Our work shows that we need to rely on multiple evidence to be more confident in the history of collisions – almost like investigating an ancient crime scene.”

Asteroids and meteorites are often studied as time capsules from the formation of the solar system about 4.5 billion years ago. This is because when the solar system formed from a disk of dust and gas orbiting the newborn Sun, the planets were formed as a result of repeated collisions of smaller rocks.

Here on Earth, as on other planets, this history is extremely difficult to trace, as it has been rewritten by geological and weather processes. Even large surface impacts can be hidden.

Asteroids, on the other hand, are inert and can float in space, remaining more or less unchanged until they are pulled into Earth’s gravity well and crash into the planet as a meteorite.

We have some means of dating ancient collisions of minerals found in meteorites. One of them is uranium-lead dating of zircon crystals.

When formed, zircon includes uranium but strongly rejects lead. Therefore, any lead found in zircon must be a radioactive decay product of uranium. We know how long it takes for uranium to decay, so we can infer the age of zircon from the lead component.

In addition, exposure can even partially or completely “reset” the radioisotope age of minerals. With this tool in hand, scientists had previously discovered that the Chelyabinsk meteorite had two collisions, one about 4.5 billion years ago and the other about 50 million years ago.

Walton and his colleagues wanted to confirm these dates by studying how the phosphate minerals in the meteorite were destroyed by successive collisions.

“Phosphates in most primitive meteorites are fantastic objects for dating the impact events experienced by meteorites on their parent bodies,” said geophysicist Sen Hu of the Chinese Academy.

Based on new uranium-lead dating, the researchers studied the microscopic details of the destruction of phosphate minerals and the effect of shock heating on the crystal structure.

They found that an earlier impact 4.5 billion years ago crushed the phosphate minerals into small pieces and exposed them to high temperatures. The later impact seemed smaller, with lower pressure and temperature. The team’s results indicate that this collision occurred less than 50 million years ago.

The earlier impact findings support previous evidence that much high-energy destruction of cosmic bodies occurred in space between 4.48 and 4.44 billion years ago.

This time frame is important because it may coincide with two separate major formation periods in the solar system’s history: the migration of giant planets, or an ancient collision that broke off a chunk of the young Earth to form the Moon .

In the scenario for the formation of the Moon, it is believed that a body the size of Mars crashed into the Earth about 4.5 billion years ago (give or take), throwing a bunch of material into space, which combined to form the Moon.

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