(ORDO NEWS) — A space rock recovered just hours after entering Earth‘s atmosphere has shown that there can be no such thing as a “pristine” meteorite.
The Winchcombe meteorite hit Earth in February 2021 after a mid-air explosion over Gloucestershire, England, and several fragments were recovered from nearby fields and properties in the following days, the first of which was in the driveway just 12 hours later. after the fireball was seen.
However, this short period of time was enough for changes in the chemical composition of the rock to occur.
The analysis showed a significant and extensive contamination of the earth’s atmosphere and earth with salts and minerals that should have been formed in the sample after its arrival on our home planet.
In particular, the researchers found halite, calcite, and calcium sulfate minerals that were formed after a meteorite broke up in the Earth’s atmosphere.
This contamination is something that scientists will need to consider when studying meteorite fragments in the future.
On the other hand, the results could also help efforts to protect recently fallen meteorites from Earth changes, as well as geological samples brought home from space for example, samples of the asteroid Ryugu brought to Earth in 2020, or a planned delivery of samples from the surface of Mars.
The Winchcombe meteorite is often referred to as ‘pristine’. example of a CM chondrite meteorite, and it has already produced remarkable results,” says Earth scientist Laura Jenkins from the University of Glasgow in Scotland.
“However, this study has shown that there really is no such thing as a pristine meteorite – Earth changes start the moment it hits Earth’s atmosphere, and we can see that in these samples that we analyzed just a couple of months after meteorite fall.
The analysis showed Winchcombe. The 4.6 billion year old rock is known to be a rare type of meteorite known as a carbonaceous chondrite composed primarily of carbon and silicon.
We can learn a lot from such an ancient piece of space rock, but only if we correctly interpret what we are looking at.
Jenkins and her colleagues performed scanning electron microscopy, Raman spectroscopy, and transmission electron studies. microscopy of several samples.
These samples included one from the original driveway find and several from the sheep fields where they lay for several days before being discovered.
When an asteroid enters Earth’s atmosphere, it doesn’t just fall. As it falls, the air in front of it compresses and heats up, causing the outer part of the meteor to melt and be thrown off.
The next layer then melts and crumbles until it slows down enough that the air is no longer hot enough to melt the rock, leaving the final layer to cool and solidify into a thin crust.
This is called melting crust and is the main diagnostic feature that allows you to visually tell the difference between a meteorite and ordinary old earth rock.
Jenkins and her team did a thorough study and found that calcite and calcium sulfates – gypsum, bassanite and anhydrite – formed on the melt crust of the meteorite samples found in the sheep field.
Since this piece of meteorite had been there for six days, they concluded that the minerals probably precipitated from the humid environment.
On a sample in the driveway, they found halite, but only on the part of the sample that was polished after extraction in areas relatively rich in sodium.
They found that this was likely due to an interaction between the stone and the humid laboratory environment in which it had been stored for several months.
The discovery, the researchers say, suggests that meteorites should be stored with care. under inert conditions to try to minimize terrestrial pollution.
“This shows how reactive meteorites are to our atmosphere, and how careful we have to be in ensuring that we account for these kinds of Earth changes when we analyze meteorites,” explains Jenkins.
“Understanding which phases are extraterrestrial and which are terrestrial in meteorites like Winchcombe will not only help us understand their formation, but will also help link meteorites that have landed on Earth to samples returned by sample return missions.
It is possible to build a more complete picture of the asteroids in our solar system and their role in the evolution of the Earth.”
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