'Air on Moon?': NASA scientists solve 50-year-old mystery, find...

NASA astronauts who explored the moon during the 1960s and 1970s found something surprising: the moon has a very thin atmosphere. New research based on soil samples from Apollo missions has revealed more about how this delicate lunar atmosphere is created.

The study, led by Nicole Nie from the Massachusetts Institute of Technology (MIT), focuses on soil samples from five different Apollo missions. The findings, published in Science Advances, suggest that meteorite impacts are the main reason the moon has an atmosphere.

When meteorites collide with the moon, they produce extremely high temperatures, ranging from 2,000 to 6,000 degrees Celsius. These intense temperatures melt and vaporize rocks on the moon’s surface, releasing atoms into the atmosphere.

The moon’s atmosphere is so thin that it is considered an exosphere. In an exosphere, the few atoms present do not collide with each other, unlike the dense atmosphere on Earth.

During the Apollo missions, astronauts used instruments to detect these atoms. More recently, in 2013, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft studied the moon's atmosphere. LADEE identified two key processes contributing to the lunar atmosphere: meteorite impacts and solar wind sputtering. Solar wind sputtering occurs when charged particles from the sun hit the moon and cause surface atoms to be ejected.

However, LADEE did not quantify the impact of these processes. The new research shows that meteorite impacts are responsible for over 70% of the lunar atmosphere, while solar wind sputtering contributes less than 30%.

The moon has been hit by meteorites for billions of years, from large impacts in its early history to smaller micrometeorites today. Some atoms released by these impacts escape into space, but others stay in the moon's atmosphere, which is continuously replenished by new meteorite collisions.

The lunar atmosphere includes elements like argon, helium, neon, potassium, and rubidium. It extends from the moon’s surface to about 62 miles (100 kilometers) above it, whereas Earth's atmosphere extends to about 6,200 miles (10,000 kilometers).

To study the moon's atmosphere, researchers analyzed lunar soil using mass spectrometry to examine the isotopic ratios of potassium and rubidium. Isotopes are variations of the same element with different masses. The interaction between the lunar soil and the exosphere leaves unique imprints on these isotopic ratios.

Study co-author Timo Hopp from the Max Planck Institute for Solar System Research in Germany noted that advances in technology since the 1970s have allowed scientists to measure these isotopic differences with much greater precision.

This research highlights the progress made in understanding the moon's atmosphere. Despite decades of study, scientists are still uncovering new details about the moon’s atmospheric processes. “Many important questions about the lunar atmosphere remain unanswered, and technological advancements are helping us address some of these questions,” said Nicole Nie.

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