Humanity has maintained an enduring fascination with the Moon. It wasn’t until Galileo’s time, however, that scientists really began to study it. Over nearly five centuries, researchers have advanced many highly controversial theories about the formation of the Moon. Today, geochemists, cosmochemists and petrologists at ETH Zurich shed new light on the story of the origin of the Moon. In a study just published in the journal, Scientists progress, the research team reports findings that show the Moon inherited the native noble gases helium and neon from Earth’s mantle. The discovery adds to already strong constraints on 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 doctoral research at ETH Zurich, Patrizia Will analyzed six samples of lunar meteorites from an Antarctic collection, obtained from NASA. Meteorites are made up of basalt rocks that formed when magma erupted from inside the Moon and cooled rapidly. They remained covered with additional layers of basalt after their formation, which protected the rock from cosmic rays and, in particular, from the solar wind. The cooling process resulted in the formation of moonglass particles among other minerals found in the magma. Will and the team discovered that the glass particles retain the chemical fingerprints (isotopic signatures) of solar gases: helium and neon from inside the Moon. Their findings strongly support that the Moon inherited Earth’s native noble gases. “Finding solar gases, for the first time, in basalt materials on the Moon that are not related to any exposure on the lunar surface was such an exciting result,” says Will.
Without the protection of an atmosphere, asteroids continuously bombard the Moon’s 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 Lunar Mare. Eventually, the rock fragments made their way to Earth in the form of meteorites. Many of these meteorite samples are collected 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 lyrics inspire lab instrument
In ETH Zurich’s Noble Gas Laboratory is a state-of-the-art noble gas mass spectrometer named “Tom Dooley” – sung in the Grateful Dead tune of the same name. The instrument takes its name from the fact that earlier researchers at one time hung the highly sensitive equipment from the ceiling of the laboratory to avoid interference from the vibrations of everyday life. Using the Tom Dooley instrument, the research team was able to measure sub-millimeter glass particles from meteorites and rule out the solar wind as the source of the detected gases. The helium and neon they detected were in much higher abundance than expected.
The Tom Dooley is so sensitive that it is, in fact, the only instrument in the world capable of detecting such minute concentrations of helium and neon. It was used to detect these noble gases in the 7 billion-year-old grains of the Murchison meteorite, the oldest solid matter 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 strongly believe that there will be a race to study heavy noble gases and isotopes in meteoritic materials,” says ETH Zurich professor Henner Busemann, one of the world’s leading scientists in the field of the geochemistry of extraterrestrial noble gases. He predicts that soon researchers will be looking for noble gases such as xenon and krypton which are harder to identify. They will also look for other volatile elements such as hydrogen or halogens in lunar meteorites.
Busemann comments: “Although these gases are not necessary for life, it would be interesting to know how some of these noble gases survived the brutal and violent formation of the moon. Such 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. Original written by Marianne Lucien. Note: Content may be edited for style and length.