Ever since humans first set eyes on it, the Moon has held a special allure for them. But it wasn’t until Galileo’s time that researchers started to take it seriously.
Over the past almost 500 years, scientists have come up with a lot of theories about how the Moon came to be.
Now, geochemists, cosmochemists, and petrologists at ETH Zurich have found new details about how the Moon formed.
The research team’s findings, which have just been reported in the journal Science Advances, demonstrate that the Moon acquired the native noble gases helium and neon from the Earth’s mantle.
The finding strengthens the already tight limitations on the widely accepted “Giant Impact” theory, which postulates that Earth and another celestial body collided violently to create the Moon.
Moon-to-Antarctica meteorites
Patrizia Will examined six lunar meteorite samples from a NASA Antarctic collection for her PhD thesis at ETH Zurich. The meteorites are made of basalt rock, which was created when magma welled up from the Moon’s interior and soon cooled.
After they formed, fresh layers of basalt continued to cover them, shielding the rock from cosmic rays and, in particular, the solar wind. As the magma cooled, moon glass particles formed among the other minerals present.
Will and the team found that the glass particles still have helium and neon chemical fingerprints (isotopic signatures) from the Moon’s interior.
Their results provide compelling evidence that the Moon inherited the Earth’s native noble gases.
“Finding solar gases, for the first time, in basaltic materials from the Moon that are unrelated to any exposure on the lunar surface was such an exciting result,” adds Will.
The Moon’s surface is constantly attacked by asteroids because it lacks an atmosphere. The meteorites were presumably ejected from the middle strata of the lava flow, which was similar to the huge plains known as the Lunar Mare, by a high-energy impact.
The rock shards eventually arrived on Earth in the form of meteorites. In this case, the “cold desert” of Antarctica, where they are easier to see in the landscape, many of these meteorite samples are found in the deserts of North Africa.
Dead lyrics inspire lab device
A high-tech noble gas mass spectrometer called “Tom Dooley” lives in the Noble Gas Laboratory at ETH Zurich. The Grateful Dead wrote a song with the same name.
The instrument got its name from the fact that sensitive equipment used to be hung from the ceiling of the lab so that it wouldn’t be affected by the vibrations of everyday life.
The study team was able to rule out solar wind as the source of the observed gases by measuring sub-millimeter glass particles from the meteorites using the Tom Dooley instrument.
They found far higher abundances of helium and neon than they had anticipated.
Because of its extreme sensitivity, the Tom Dooley is the only device in the world that can detect such trace amounts of helium and neon.
The grains of the 7 billion-year-old Murchison meteorite, which is the oldest known solid material to date, were examined to find these noble gases.
Looking for the source of life
A significant advancement is knowing where to seek among the roughly 70,000 recognized meteorites in NASA’s enormous collection.
One of the foremost researchers in the subject of extra-terrestrial noble gas geochemistry, Professor Henner Busemann of ETH Zurich, says, “I am strongly convinced that there will be a race to study heavy noble gases and isotopes in meteoritic materials.”
He believes that soon scientists would be seeking more difficult-to-identify noble gases like xenon and krypton. In the lunar meteorites, they will also be looking for additional volatile elements like hydrogen or halogens.
While these gases are not essential for life, Busemann observes that it would be intriguing to learn how some of these noble gases survived the terrible and violent genesis of the moon.
Such information might aid geochemists and geophysicists in developing new models that more broadly illustrate how these highly volatile elements might survive planet formation in the solar system and beyond.
Image Credit: Getty
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