A Breath of Fresh Air

Soil samples gathered by Apollo astronauts have yielded a new discovery.

There’s an old joke about a guy who dines at a restaurant on the moon. “Great food,” he tells his friends, “but no atmosphere.”

Jokes aside, the moon does indeed have an atmosphere—albeit a meager one called an “exosphere,” which is so tenuous it eventually escapes into space or falls back to the lunar surface. Yet somehow, the exosphere is constantly replenished.

For decades, scientists have been puzzling over the origins of the moon’s exosphere. Now, thanks to a creative analysis of lunar soil samples collected by the Apollo missions more than 50 years ago, researchers at MIT and the University of Chicago have concluded that most of the moon’s exosphere is being generated and replenished by meteorite impacts. 

The scientists had two theories: Either the exosphere was being created by meteorites vaporizing material upon impact or by solar wind that bombards the surface with high-energy particles that send atoms aloft, a process called “isotope sputtering.” Scientists tested the theories by measuring isotopes of potassium and rubidium in the lunar soil. (Isotopes are variations of an element, which differ in the number of neutrons they contain.) If these elements were being bombarded by solar wind, then all sorts of isotopes would be lofted upward. But if the elements in the soil were being vaporized by meteorites, then the heavier isotopes would be more likely to settle back in the soil. 

Based on their isotope measurements of the Apollo samples, the researchers concluded that 70 percent of the moon’s exosphere is generated by meteorite impacts, while 30 percent is a result of solar wind. 

The Apollo samples are “national treasures,” says Cole Nypaver, a geologist at the National Air and Space Museum’s Center for Earth and Planetary Studies. “The isotopic analysis that led to the discovery of an impact-driven atmosphere was not possible when lunar samples were first returned to Earth in the 1960s and 1970s. However, many of the samples were preserved in anticipation of future, improved techniques that would allow for new discoveries and understandings.”

A recent episode of the AirSpace podcast explores how humans can interact with the moon from Earth through moon rocks returned by Apollo astronauts.

Tales of the Fab 5

On February 21, 2019, five female pilots assigned to the U.S. Coast Guard—known as the Fab 5—gathered at the Tuskegee Airmen National Historic Site to honor one of their own. Lieutenant Ronaqua Russell was awarded an Air Medal for her actions assisting with evacuation and supply deliveries during Hurricane Harvey. The ceremony—which was held at the same airfield where the first Black aviators in the U.S. military trained—was steeped in significance: Russell is the first Black woman aviator to receive the Air Medal, which is awarded for “single acts of heroism or meritorious achievements while participating in aerial flight.”

Supporting Russell that day were the other four members of the Fab 5—the first five Black women pilots in the Coast Guard. The Fab 5 includes Commander Jeanine Menze, the first Black woman pilot in the Coast Guard; Commander LaShanda Hawkins, the first Black woman to serve as a helicopter pilot in the Coast Guard; Lieutenant Angel Hughes, the second Black female fixed-wing aviator in Coast Guard history; and Commander Chanel Lee, the first Black woman to fly an MH-60 Seahawk helicopter.

Menze, Hawkins, and Lee will speak at the Steven F. Udvar-Hazy Center on October 10 at 8 p.m. ET for the Museum’s second Aviation Adventures lecture of the fall. The program, sponsored by GE Aerospace, will also be streamed live on YouTube. Learn more and register to attend.

How to Impersonate an Enemy Drone

A KestrelX JSX-2 microjet taxis during exercise Northern Strike 2024-2, at the Alpena Combat Readiness Training Center in Michigan on August 6, 2024. The U.S. Air Force uses the JSX-2, a small and agile aircraft, primarily for training purposes—particularly in simulating enemy unpiloted aerial systems, which are increasingly relevant in modern combat scenarios. The JSX-2 weighs just 500 pounds and is 16.5 feet long.

Read About “The Secret History of Drones”

This article is from the Fall 2024 issue of Air & Space Quarterly, the National Air and Space Museum's signature magazine that explores topics in aviation and space, from the earliest moments of flight to today. Explore the full issue.

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