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

Updated on 11/17/2022 at 11:53 AM

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

More about space

Meteorites can provide scientists with valuable information about the young solar system. The problem: After the collision, ground effects quickly shift the stones that fell from space, thus blurring the tracks. However, at the beginning of 2021, thanks to several camera recordings, it was possible England He fell meteorites They can be found within a few hours. This relatively untouched meteorite contains water and a large number of organic materials, including amino acids, an international team of researchers reports now in the journal Science Advances.

The composition of the Winchcombe meteorite is almost not affected by the terrestrial environment

Ashley King of the Natural History Museum in London and colleagues explain the importance of the discovery: “The formation of the meteorite is almost not affected by the terrestrial environment.” Moreover, the researchers’ investigations showed that the meteorite hadn’t been altered much by cosmic radiation – so it couldn’t have stayed in space for a long time. The scientists concluded that it “fell to the ground shortly after being separated from its original body.” Such debris can enter the inner solar system through collisions in the asteroid belt between Mars and Jupiter – and sometimes even penetrate Earth’s atmosphere.

At 9:54 p.m. local time on February 28, 2021, a bright shooting star crossed the skies over Gloucestershire in southwest England. The rock tracker was captured from space by 16 special cameras from the Meteorite Network, as well as several surveillance and dashboard cameras. Observatories and other research institutions have also received more than a thousand eyewitness testimonies.

From all these images and scenes, the meteorite fall can be very accurately reconstructed and within a few hours it was actually tracked: on a walkway in the town of Winchcombe, it crashed into a heap of dark fragments one to two millimeters in size. a total mass of 319.5 grams. Over the next few days, researchers found many more fragments, the largest weighing 152 grams, in a field near Winchcombe.

The first pieces found are especially valuable – because water is bound to the stone

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

Water molecules consist of two hydrogen atoms and an oxygen atom. Hydrogen is exciting to researchers because it occurs in three types–physicists call isotopes: light, heavy, and superheavy hydrogen. Heavy isotopes are rare, and their abundance in water allows conclusions to be drawn about their origin. “The near-pure hydrogen isotopic composition of the Winkcomb meteorite is similar to that of Earth’s hydrosphere,” King and colleagues said. This once again confirms the hypothesis that the majority of water on Earth comes from asteroids.

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