Meteorites From Before 466-Million-Year Old Space Collision Help Solve A Longstanding Mystery

Posted: Jan 24 2017, 12:06am CST | by , Updated: Jan 24 2017, 12:24am CST, in News | Latest Science News

 

Meteorites from Before 466-Million-Year Old Space Collision Help Solve a Longstanding Mystery
Artist's impression of space collision that is raining meteorites even today. Credit: Don Davis, Southwest Research Institute.
 

Meteorites we see today are different from the ones that have fallen before a massive space collision 466 million years ago

Thousands of fragments from space fall on Earth every year. These pieces, known as meteorites, are formed by collisions between two outer space objects such as comets and asteroids and have seen floating around in space. Since meteorites are created as result of a body smashing into another, there can be different types of meteorites.

Evidence suggests that a massive collision occurred in space some 466 million years ago. Some unknown body slammed into an asteroid and broke it apart, spraying out a large amount of debris into the space. Many of those fragmens also passed through the Earth’s atmosphere and are hitting the Earth even today. But what kind of meteorites were landing on Earth before the collision, it was a mystery until now.

To find out, researchers examined some of the rocky relics found on Earth. They discovered that most of the meteorites we see today are different from the ones that have fallen in the earliest times. The most common types of meteorites today were quite rare before while the rare ones were common before the collision.

“We knew almost nothing about the meteorite flux to Earth in geological deep time before this study," said co-author Birger Schmitz from Sweden's Lund University. "The conventional view is that the solar system has been very stable over the past 500 million years. So it is quite surprising that the meteorite flux at 467 million years ago was so different from the present.”

Researchers reconstructed the distribution of meteorites to indentify their different types falling on Earth before the catastrophe collision. For this purpose, researchers decided to analyze the meteorites both before and after the collision. However, it was not an easy task. 

Meteorites are difficult to recover under any circumstances. So, finding ones that have survived their journeys through Earth’s atmosphere and remained intact millions of years later is even harder. However, researchers found a way to obtain these ancient space rocks. They looked for the chrome-spirals that contained those early meteorites and retrieved those samples from an ancient seafloor exposed in a Russian river valley.

“Chrome-spinels, crystals that contain the mineral chromite, remain unchanged even after hundreds of millions of years," explains lead author, Philipp Heck of The Field Museum in Chicago. “Since they were unaltered by time, we could use these spinels to see what the original parent body that produced the micrometeorites was made of.”

Analysis of these tiny meteorites that are less than 2 mm across showed that they were different from the ones that hit the Earth after the collision 466 billion years ago. The micrometeorites also revealed a lot about the compositional makeup of their parent bodies. 34% of the pre-collision meteorites belong to a meteorite type called primitive achondrites. Only 0.45% of such meteorites fall today on Earth. Other ancient micrometeorites turned out to be pieces from Vesta, the brightest asteroid visible from Earth, which collided with another object a long time ago.

The latest findings can also help researchers better understand the formation and evolution of our solar system.

"Knowing more about the different kinds of meteorites that have fallen over time gives us a better understanding of how the Asteroid Belt evolved and how different collisions happened," said Heck. "Ultimately, we want to study more windows in time, not just the area before and after this collision during the Ordovician period, to deepen our knowledge of how different bodies in Solar System formed and interact with each other."

 

 

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Hira Bashir covers daily affairs around the world.

 

 

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