Where does the water on Earth come from? Meteorite provides another puzzle piece

Updated on 11/17/2022 11:53 AM

  • Meteorites usually lie on Earth for a while before they are found.
  • But that changes their chemistry.
  • Now researchers have found and examined a very fresh specimen.

More about space

Meteorites can provide scientists with valuable information about the young solar system. The problem: After the impact, terrestrial influences quickly alter the rocks that fell from space, blurring the tracks. However, in early 2021, thanks to numerous camera recordings, a meteorite that fell in England could be detected within a few hours. This relatively pristine meteorite contains water and a large number of organic substances, including amino acids, an international team of researchers now reports in the journal Science Advances.

Composition of the Winchcombe meteorite almost unaffected by the terrestrial environment

“The composition of the meteorite is almost unaffected by the terrestrial environment,” Ashley King of the Natural History Museum in London and his colleagues explain the significance of the find. In addition, the researchers’ research shows that the meteorite has hardly been changed by cosmic rays – so it cannot have stayed in space too long. “It fell to Earth shortly after it split from its original body,” the scientists conclude. Such debris can enter the inner solar system from collisions in the asteroid belt between Mars and Jupiter – and sometimes enter Earth’s atmosphere.

At 21:54 local time on February 28, 2021, a bright shooting star crossed the sky of Gloucestershire in southwest England. The tracer of the rock from space was captured by 16 special cameras of a meteorite network, as well as numerous surveillance and dashboard cameras. More than a thousand eyewitness accounts were also received by observatories and other research institutions.

From all these photographs and observations, the fall of the meteorite could be reconstructed with great precision, and within a few hours it was actually tracked down: on a driveway in the town of Winchcombe, shattered into a pile of dark centimeter-to-millimetre-sized fragments with a total mass of 319.5 grams. Over the next few days, researchers found numerous other fragments, the largest, weighing 152 grams, in a field near Winchcombe.

The first pieces found are particularly valuable – because water is bound in the stone

The parts of the meteorite that were found first are particularly valuable because they were least exposed to the terrestrial environment. They were immediately packed in tightly sealed containers and taken to special laboratories for examination. As King’s team reports, the rock contains a large amount of silicates in which water is bound. This is an important clue that the rock was in contact with liquid water when it formed.

Water molecules consist of two hydrogen and one oxygen atom. Hydrogen is exciting for the researchers because it comes in three varieties – called isotopes by physicists: light, heavy and super-heavy hydrogen. The heavy isotopes are rare and their abundance in water allows conclusions to be drawn about their origin. “The nearly pure composition of the hydrogen isotopes in the Winchcombe meteorite is similar to that of Earth’s hydrosphere,” said King and his colleagues. This further confirms the claim that most of the water on Earth comes from asteroids.

In addition, the meteorite contains numerous complex chemical compounds based on the element carbon. Chemists call such substances organic because they were first found in living matter in the 19th century. Even amino acids are among them, which play an important role in terrestrial biology as components of proteins. “Prebiotic molecules such as these amino acids are critical components for the emergence of life,” the researchers point out. “Their presence in the pure Winchcombe meteorite indicates that this organic matter may have been brought to the young Earth by meteorites.”
© dpa

There are similar terms for alien objects. You can see what they mean and what the difference is in the video. (Photo: iStock-adventtr)

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