A bootprint made by Buzz Aldrin during the Apollo 11 mission. Image : NASA

Moon Week Moon Week As we approach the 50th anniversary of the U.S. landing on the Moon, we look back at the hopes, fears, and ingenuity inspired by our closest cosmic neighbor. Prev Next View All

Prior to the first Moon landing, scientists had good reason to believe the lunar surface was covered in a fine layer of dust. While this might not sound like a big deal, it presented a host of concerns to the Apollo mission planners.




In 1955, pioneering Cornell scientist Thomas Gold controversially theorized that the lunar surface was covered in a fine rocky power, the result of countless collisions with large and small meteorites and the effects of solar radiation breaking down surface materials. Many scientists objected, but NASA took this possibility very seriously, particularly during the planning stages of the Apollo program. For NASA, the presence of Moon dust, known as regolith, produced no shortage of potential problems.

First and foremost, and as proposed by Gold, the lunar dust might swallow astronauts like quicksand. Indeed, without any prior experience of standing on a celestial body aside from Earth, a concern emerged that the soft regolith on the Moon wasn’t compact enough to support the weight of the Lunar Module or astronauts out for a stroll. Nightmarish thoughts of astronauts getting swallowed up into the lunar dust prompted further investigation.


The threat was taken seriously enough that research into “lunar surface bearing strength” became a stated goal of NASA’s Surveyor program. Between 1966 and 1968, seven Surveyor probes were sent to the Moon (of which five survived the journey) to investigate various characteristics of the lunar surface—bearing strength included.

A Surveyor 3 footpad rests on the dusty lunar surface. The imprint was caused by the probe bouncing off the surface during landing. Image : NASA

Data from these missions suggested the surface was tough enough to support the weight of the astronauts, but as Buzz Aldrin later recounted in his book Return to Earth, trepidation about the prospect persisted right up until the landing:



The moon had been measured, compared with other planets, and poked at. One by one old misconceptions about it had died. In the seventeenth century, scientists believed there were creatures on the moon...More widely held was the suspicion that the moon’s surface was covered with dust so thick it would swallow a man or a spaceship like quicksand. These theories had been disproved one by one until the only concern about the dust remained. The unmanned Surveyor landings indicated a well-compacted surface which would more than adequately support the weight of the [Lunar Module]. So this, too, was a relatively minor concern. No one would know for sure, of course, until we were there.


As testament to this concern, the iconic photograph of Aldrin’s footprint was actually taken as part of the ongoing research into the soil mechanics of the lunar surface. Needless to say, no one got sucked up into the lunar regolith, and this fear was finally relegated to scientific dustbin of history.

Apollo 11 astronaut Buzz Aldrin standing next to a leg of the Eagle lunar module. Thankfully, no one sank through the soft lunar regolith. Image : NASA


Because the lunar dust was presumed to consist of tiny particles, a concern emerged about the regolith’s static potential. This turned out to be true, as “static cling” caused the dust to stick to the Apollo astronauts’ suits as they entered into the capsule after their moonwalks. That said, NASA didn’t predict the scale or worry too much about the static cling at first, and a brush wasn’t supplied until Apollo 13.



Instead, mission planners worried about the static effect during the landing. Writing in his 2009 book, Moonshot: The Inside Story of Mankind’s Greatest Adventure, Dan Parry writes that scientists feared “a charge of static electricity would attract so much dust that nobody would be able to see out of the windows.” But while the Apollo landings kicked up a considerable amount of dust, the feared static cling effect never happened.


In addition to predicting the presence of lunar dust, Gold also warned NASA that the lunar dust might be volatile. His specific concern was that the dust might combust when brought into the oxygen-rich cabin of the Lunar Module, causing a fire or even an explosion. In his new book One Giant Leap, author Charles Fishman describes the nervous efforts of Neil Armstrong and Buzz Aldrin, who had been forewarned of the possibility:



Armstrong and Aldrin did their own test. Just a moment after he became the first human being to step onto the Moon, Armstrong had scooped a bit of lunar dirt into a sample bag and put it in a pocket of his spacesuit—a contingency sample, in the event the astronauts had to leave suddenly without collecting rocks. Back inside the lunar module the duo opened the bag and spread the lunar soil on top of the ascent engine. As they repressurized the cabin, they watched to see if the dirt started to smolder. “If it did, we’d stop pressurization, open the hatch and toss it out,” Aldrin explained. “But nothing happened.”


Donald Bogard, Heritage Fellow at the Lunar Planetary Institute in Houston, Texas, told Space.com back in 2014 that Gold was “partly correct” when he warned NASA that the “lunar dust brought into the lunar module might spontaneously combust and produce a safety issue,” but while he had “realized the likely reactive nature of lunar material surfaces,” Gold “over-emphasized their reactive effects.”

A well-known concern about the Apollo mission was that the astronauts might bring back dangerous pathogens, and this extended to the return of potentially contaminated lunar materials.


In 1963, a special subcommittee of the National Academy of sciences gathered to discuss the unlikely, but grim, possibility of having to deal with Apollo crew members who contracted some sort of lunar disease, and how to handle potentially contaminated materials.

President Richard Nixon visiting the Apollo 11 crew in quarantine. Image : NASA


The notion that pathogens or toxic substances could exist on the Moon might seem outlandish, but scientists at the time simply had no way of knowing—and they refused to take chances. The subcommittee subsequently recommended that NASA “establish a quarantine program to ensure that the Earth and its ecology would be protected from any possible hazard associated with the return of lunar material,” according to a NASA report compiled after the Apollo 11 mission.



NASA established a Crew Microbiology Program prior to the mission “in recognition of the possibility of returning terrestrial contaminants in the lunar soil,” according to the agency’s report. A strict postflight quarantine program was put in place for returning Apollo crewmembers, along with protocols for handling possibly contaminated spacecraft, equipment, and lunar samples.


The returning astronauts were quickly quarantined after splashdown, but as Apollo crewmembers Michael Collins and Buzz Aldrin later admitted in the PBS documentary Chasing the Moon, it was a bit of a farce, as reported by Space.com:

“Look at it this way,” [Collins] added. “Suppose there were germs on the moon. There are germs on the moon, we come back, the command module is full of lunar germs. The command module lands in the Pacific Ocean, and what do they do? Open the hatch. You got to open the hatch! All the damn germs come out!” [...] “You have to laugh a little bit,” Aldrin said as archival footage showed the astronauts being disinfected inside a raft that floated beside the spacecraft. He recalled rescue personnel sponging him down, then throwing the used rag into the water beside them. “It takes all those germs to the bottom of the ocean,” he said, then paused to laugh. “I wonder if they’d survive down there?”


In any case, the trio had to wear Biological Isolation Garments during their transport to the lunar Receiving Laboratory (LRL) at NASA’s Lyndon B. Johnson Space Center. The astronauts were in quarantine for 21 days, while medical staff were ready in the event the astronauts suddenly got sick from some unknown contaminant. Thankfully that didn’t happen, and the crew were able to rejoin their friends and families.


That the lunar dust might be toxic proved to be correct, but not in the way NASA envisioned. Apollo astronauts complained of “lunar dust hay fever” inside the capsule, and during Apollo 12, lunar dust caused lung and eye irritation on the return trip. Studies done after the Apollo missions revealed the toxic effects of inhaling the tiny, razor-sharp particles.

“I think dust is probably one of our greatest inhibitors to a nominal operation on the Moon,” said NASA astronaut Gene Cernan during the Apollo 17 technical debrief. “I think we can overcome other physiological or physical or mechanical problems except dust.”


Similarly, a 2016 report issued by the International Agency Working Group’s Dust Mitigation Gap Assessment Team concluded that dust “is still a principal limiting factor in returning to the lunar surface for missions of any extended duration.”

So while many of NASA’s concerns proved to be unwarranted, history showed the space agency was wise to worry about all that pesky dust on the Moon.