Mankind has maintained an enduring fascination with the moon. However, it was not until Galileo’s time that scientists began to really study it. Over nearly five centuries, researchers have come up with many highly controversial theories about the formation of the moon. Geochemists, cosmochemists and petrologists from ETH Zurich today shed new light on the history of the moon’s formation. In a study just published in the journal Science Advances, the research team reports results showing that the moon inherited the noble gases helium and neon from Earth’s mantle. The discovery adds to the already severe limitations of the currently favored “giant impact” theory, which hypothesizes that the moon was formed by a massive collision between Earth and another celestial body.
Meteorites from the moon to Antarctica
During her PhD at ETH Zurich, Patrizia Will analyzed six samples of lunar meteorites from an Antarctic collection that she received from NASA. Meteorites are made of basalt rock that formed when magma erupted from the moon’s interior and cooled rapidly. After their formation, they remained covered with additional layers of basalt, which protected the rock from cosmic rays and in particular from the solar wind. The cooling process led to the formation of lunar glass particles, along with other minerals found in the magma. Will and the team discovered that the glass particles contain the chemical fingerprints (isotopic signatures) of the sun’s gases: helium and neon from the moon’s interior. Their findings strongly support that the Moon inherited Earth’s native noble gases. “Finding solar gases for the first time in basaltic materials on the moon that are unrelated to lunar surface exposure was such an exciting result,” says Will.
Without the protection of an atmosphere, asteroids continuously bombard the lunar surface. It likely took a high-energy impact to eject the meteorites from the middle layers of the lava flow, similar to the vast plains known as the Lunar Mare. Eventually, the rock fragments made their way to earth in the form of meteorites. Many of these meteorite samples come from the deserts of North Africa, or in this case the “cold desert” of Antarctica, where they are easier to spot in the landscape.
Grateful Dead’s lyrics inspire Lab Instrument
In the noble gas laboratory at ETH Zurich there is a state-of-the-art noble gas mass spectrometer called “Tom Dooley” – sung in the Grateful Dead tune of the same name. The instrument owes its name to the fact that earlier researchers once hung the highly sensitive devices on the ceiling of the laboratory in order to avoid interference from everyday vibrations. Using the Tom Dooley instrument, the research team was able to measure submillimeter glass particles from meteorites and ruled out the solar wind as the source of the detected gases. The helium and neon they detected were in much greater abundance than expected.
So sensitive is the Tom Dooley that it is actually the only instrument in the world capable of detecting such tiny concentrations of helium and neon. These noble gases were thus detected in the 7 billion-year-old grains of the Murchison meteorite, the oldest solid known to date.
In search of the origins of life
Knowing where to look in NASA’s vast collection of some 70,000 approved meteorites is a major breakthrough. “I am firmly convinced that there will be a race to study heavy noble gases and isotopes in meteoritic materials,” says ETH Professor Henner Busemann, one of the world’s leading scientists in the field of geochemistry of extraterrestrial noble gases. He predicts that researchers will soon be looking for noble gases like xenon and krypton, which are harder to identify. They will also look for other volatile elements like hydrogen or halogens in lunar meteorites.
Busemann comments: “Although these gases are not essential to life, it would be interesting to know how some of these noble gases survived the brutal and violent formation of the moon. This knowledge could help geochemical and geophysical scientists create new models that show more generally how these more volatile elements can survive planet formation in our solar system and beyond. »
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Materials provided by ETH Zurich. Originally written by Marianne Lucien. Note: Content can be edited for style and length.