New techniques examining old rocks reveal the origins of the moon’s atmosphere. Meteorites that bombarded the lunar surface over billions of years are believed to have kicked up dust that forms the moon’s tenuous atmosphere. report In ~ Science advances.
Why Scientists Study Moon Rocks
A team of scientists analyzed moon rocks collected during the Apollo missions from 1968 to 1972. The samples had been previously studied.
“But back then, the equipment wasn’t that precise,” says Dr. Nicole Nieh, an MIT assistant professor and lead author of the study.
In 2013, NASA Lunar Atmosphere and Dust Environment Explorer It was to gather information about the thin atmosphere of the Moon. The mission provided two clues. First, the concentrations of potassium and rubidium in the Moon’s atmosphere increased during meteor showers. Second, the levels of these elements changed during lunar eclipses, which shielded the Moon from the Earth.
These findings suggested that two processes combined to form and continually replenish the lunar atmosphere. The researchers suspected that two space weathering processes, shock evaporation and ion sputtering, played a role in shaping the lunar atmosphere.
Read more: 7 Things You Didn’t Know About Moon Rocks
Space weathering process
Impact vaporization occurs when a meteorite hits a surface, essentially kicking up dust into the atmosphere. Ion sputtering occurs when the solar wind carries charged particles from the sun to the lunar surface and transfers energy to the soil, sputtering the atoms into the air.
That information pointed researchers in the right direction, but it didn’t provide definitive data on how much of the potassium and rubidium found in the lunar atmosphere came from evaporation and solar wind.
So Ni and her team took 10 samples from the Apollo rocks, each about the size of a raindrop. They crushed the samples into powder, dissolved the powder in acid, and separated it into separate solutions containing potassium and rubidium. They then analyzed the solutions with a mass spectrometer, measuring the different isotopes of potassium and rubidium in each sample.
Essential Isotopes
It was essential to determine the existence of isotopes. Isotopes of an element have the same number of protons but different amounts of neutrons.
Both potassium and rubidium are volatile, so sudden changes, such as shocks, can transform them into other isotopes. Measuring these atomic changes can not only tell us which elements from the lunar surface entered the atmosphere, but also provide a reasonable explanation for how they entered.
If the lunar atmosphere is made up of evaporated atoms floating in the air, the lighter isotopes would be more easily released into the atmosphere, while the heavier isotopes would more likely settle to the ground.
Also, shock evaporation and ion sputtering cause very different isotope ratios, so the specific ratio of light to heavy isotopes (both potassium and rubidium) remaining in the soil should reflect the processes contributing to the lunar atmosphere.
Read more: 50 years later, NASA hands scientists intact Apollo moon rock
The surface of the moon
According to scientists’ analysis, more than 70 percent of the lunar atmosphere was created by meteorite impacts, with the remainder being pushed by the solar wind.
Scientists weren’t surprised by these findings, since orbiters predicted the presence of these elements, but the study provides pretty convincing evidence that most of the atmospheric elements come from the surface.
“The surface is being bombarded by all sorts of things,” Nie said. “You would expect these things to release atoms into the atmosphere.”
She’s looking forward to seeing samples from the lunar rover. Artemis She will bring back soil samples from the moon’s south pole and dark side, where the concentrations of key elements can vary. She is also excited to see samples from one or both of Mars’ moons.
“Our framework includes techniques for analyzing samples from other planetary bodies,” Nies said.
Read more: Why we only see one side of the moon
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Before joining Discover Magazine, Paul Smaglik worked as a science journalist for more than 20 years, specializing in U.S. life science policy and global science career issues. He started his career in newspapers but transitioned to science magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
