NASA astronauts who initially landed on the moon in the 1960s and 1970s discovered a fragile atmosphere. The soil samples they collected are now indicating the primary physical process creating this environment.
Researchers discovered that the lunar atmosphere was produced and is sustained mostly by the effects of large and small meteorites striking the moon’s surface by examining the forms of two elements – potassium and rubidium – found in nine microscopic soil samples from five Apollo missions.
“Meteorite strikes produce high temperatures ranging from 2,000 to 6,000 degrees Celsius (3,600 to 10,800 degrees Fahrenheit). These extreme temperatures melt and vaporize rocks on the lunar surface in the same way that heat vaporizes water, releasing atoms into the atmosphere,” said Massachusetts Institute of Technology planetary scientist and cosmochemist Nicole Nie, lead author of the study published on Friday in Science Advances.
The lunar atmosphere is exceedingly thin and formally defined as an exosphere, which means that atoms do not collide since their numbers are so sparse, as opposed to Earth’s substantial and stable atmosphere.
“The Apollo missions carried instruments to the lunar surface which detected atoms in the air,” Nie informed the audience.
In 2013, NASA launched the robotic LADEE (Lunar Atmosphere and Dust conditions Explorer) spacecraft to research the moon’s atmosphere and surface conditions. It found two mechanisms at work, known as space weathering: meteorite strikes and solar wind sputtering.
“Solar wind transports high-energy charged particles, primarily protons, through space. “When these particles hit the moon, they transfer their energy to lunar surface atoms, causing them to be ejected from the surface,” Nie explained.
LADEE did not calculate the relative contributions of these two processes to the lunar atmosphere. The latest study found that impacts account for more than 70% of its composition, while solar wind sputtering contributes less than 30%.
Meteorites have pounded the moon throughout its history, beginning with enormous ones that gashed the gaping craters visible on the lunar surface and progressing to smaller ones, including dust-sized micrometeorites. Some of the atoms ejected by these impacts fly into space. The rest remain suspended above the surface in an atmosphere that is renewed on a regular basis as new meteorites land.
The lunar atmosphere is mostly composed of argon, helium, and neon, with potassium and rubidium and potentially other elements present at lower concentrations. It rises from the moon’s surface to a height of around 62 miles (100 kilometers). The Earth’s atmosphere spans for around 6,200 miles (10,000 kilometers).
Instead of studying the real atoms in the lunar atmosphere, the researchers employed lunar dirt, or regolith, as a proxy. They utilized a mass spectrometer to evaluate the potassium and rubidium isotope ratios in the soil. Isotopes are atoms of the same element that have slightly varied masses due to variations in the amount of subatomic particles known as neutrons.
“This is possible because the lunar surface soil has been interacting with the exosphere since the formation of the moon, and the different processes leave distinct imprints on the isotopic composition of the lunar soil,” said planetary scientist and study co-author Timo Hopp of the Max Planck Institute for Solar System Research in Germany.
There are three isotopes of potassium and two isotopes of rubidium.
After decades of studying the moon, scientists are still learning about some of its fundamental processes.
“Many critical concerns about the lunar atmosphere are unanswered. “We can now answer some of these questions thanks to technological advancements,” Nie said. “When Apollo samples returned from the moon in the 1970s, mass spectrometers were used to analyze the isotopic compositions of potassium and rubidium in lunar soils. However, at the time, no isotopic changes were detected. Today’s mass spectrometers provide far more precision.”
NASA astronauts who initially landed on the moon in the 1960s and 1970s discovered a fragile atmosphere. The soil samples they collected are now indicating the primary physical process creating this environment.
Researchers discovered that the lunar atmosphere was produced and is sustained mostly by the effects of large and small meteorites striking the moon’s surface by examining the forms of two elements – potassium and rubidium – found in nine microscopic soil samples from five Apollo missions.
“Meteorite strikes produce high temperatures ranging from 2,000 to 6,000 degrees Celsius (3,600 to 10,800 degrees Fahrenheit). These extreme temperatures melt and vaporize rocks on the lunar surface in the same way that heat vaporizes water, releasing atoms into the atmosphere,” said Massachusetts Institute of Technology planetary scientist and cosmochemist Nicole Nie, lead author of the study published on Friday in Science Advances.
The lunar atmosphere is exceedingly thin and formally defined as an exosphere, which means that atoms do not collide since their numbers are so sparse, as opposed to Earth’s substantial and stable atmosphere.
“The Apollo missions carried instruments to the lunar surface which detected atoms in the air,” Nie informed the audience.
In 2013, NASA launched the robotic LADEE (Lunar Atmosphere and Dust conditions Explorer) spacecraft to research the moon’s atmosphere and surface conditions. It found two mechanisms at work, known as space weathering: meteorite strikes and solar wind sputtering.
“Solar wind transports high-energy charged particles, primarily protons, through space. “When these particles hit the moon, they transfer their energy to lunar surface atoms, causing them to be ejected from the surface,” Nie explained.
LADEE did not calculate the relative contributions of these two processes to the lunar atmosphere. The latest study found that impacts account for more than 70% of its composition, while solar wind sputtering contributes less than 30%.
Meteorites have pounded the moon throughout its history, beginning with enormous ones that gashed the gaping craters visible on the lunar surface and progressing to smaller ones, including dust-sized micrometeorites. Some of the atoms ejected by these impacts fly into space. The rest remain suspended above the surface in an atmosphere that is renewed on a regular basis as new meteorites land.
The lunar atmosphere is mostly composed of argon, helium, and neon, with potassium and rubidium and potentially other elements present at lower concentrations. It rises from the moon’s surface to a height of around 62 miles (100 kilometers). The Earth’s atmosphere spans for around 6,200 miles (10,000 kilometers).
Instead of studying the real atoms in the lunar atmosphere, the researchers employed lunar dirt, or regolith, as a proxy. They utilized a mass spectrometer to evaluate the potassium and rubidium isotope ratios in the soil. Isotopes are atoms of the same element that have slightly varied masses due to variations in the amount of subatomic particles known as neutrons.
“This is possible because the lunar surface soil has been interacting with the exosphere since the formation of the moon, and the different processes leave distinct imprints on the isotopic composition of the lunar soil,” said planetary scientist and study co-author Timo Hopp of the Max Planck Institute for Solar System Research in Germany.
There are three isotopes of potassium and two isotopes of rubidium.
After decades of studying the moon, scientists are still learning about some of its fundamental processes.
“Many critical concerns about the lunar atmosphere are unanswered. “We can now answer some of these questions thanks to technological advancements,” Nie said. “When Apollo samples returned from the moon in the 1970s, mass spectrometers were used to analyze the isotopic compositions of potassium and rubidium in lunar soils. However, at the time, no isotopic changes were detected. Today’s mass spectrometers provide far more precision.”
