The mystery of how the moon’s thin atmosphere is produced has been solved, according to scientists studying lunar samples brought back by the Apollo missions.
The lunar atmosphere, discovered in the 1960s and 70s when NASA sent astronauts to the moon, is much thinner than Earth’s, and is thought to have resulted from space weathering of the moon’s surface.
Now, experts say they have teased out the relative contributions of such processes to the lunar atmosphere, revealing that meteorite impacts are the major player.
“Our findings provide a clearer picture of how the Moon’s surface and atmosphere interact over long time scales, [and] improve our understanding of space weathering processes,” said Dr Nicole Nie, the co-author of the new study based at MIT’s Department of Earth, Atmospheric and Planetary Sciences.
Write in the journal Science AdvancesNie and her colleagues describe how the lunar atmosphere must be constantly replenished because its atoms are constantly being lost to space, mainly due to the moon’s weak gravity, or trapped on the lunar surface.
Ultraviolet photons from the sun can release the latter again, but the researchers say the replenishment of the atmosphere is thought to depend on atoms released from inside lunar minerals – either through evaporation from meteorite impacts, or through solar wind sputtering, a process in which charged particles from the sun hits the moon and ejects atoms.
But which of the two factors dominated was unclear, with data from Nasa’s Lunar Atmosphere and Dust Environment Explorer, launched in 2013, suggesting both were at play.
Nie and colleagues unraveled the mystery by studying the different forms, or isotopes, of potassium and rubidium in 10 samples of lunar soil from the Apollo missions.
The team says meteorite impacts and solar wind splashes both favor the release of lighter forms of the elements, but that the actual ratio of heavy to light isotopes ending up in the lunar atmosphere and soil will vary depending on the process.
“After measuring the isotopic compositions of lunar soil, we built a mathematical model that took into account various space weathering processes, and resolved the contribution of each of them by fitting the measured isotopic compositions,” Nie said.
The results suggest that about 70% of the moon’s atmosphere is due to impact evaporation and 30% to solar wind splashes.
Dr Simeon Barber, a senior research fellow at the Open University who was not involved in the work, said the findings were another important piece in the puzzle of understanding how our moon works.
“Understanding how the thin atmosphere forms on moons and minor planets helps us understand how these bodies became so diverse,” he said, adding that the way forward was to explore new places with spacecraft. visit, take measurements there and then return samples. down to earth for analysis. “The moons of Mars, Phobos and Deimos, would be fascinating places to do this kind of study next,” he said.
