The inside of Apollo 17’s lunar module smelled of gunpowder. It was December 1972, the last of NASA’s manned moon missions, and astronauts Eugene Cernan and Harrison “Jack” Schmitt had just finished a successful survey of the Valley of Taurus-Littrow, a spot on the southeastern “coast” of the Moon’s Sea of Serenity. They had returned to the landing module with their spacesuits caked in moondust.

The men brushed themselves off and removed their helmets. Suddenly, Schmitt began having a sneezing fit. His eyes reddened. His throat itched. His sinuses clogged.

“I didn’t know I had lunar dust hay fever,” Schmitt said. Listening in, men stationed back on Earth began to bust Schmitt’s chops over the radio transmission. “It’s funny they don’t check for that,” said Joseph Allen at Mission Control. “Maybe that’s the trouble with the cheap noses, Jack.”

Schmitt, it turns out, was basically allergic to the Moon.

NASA

Of all the difficulties involved with putting a man on the Moon,

“the major issue the Apollo astronauts pointed out was dust, dust, dust,” Larry Taylor, director of the Planetary Geosciences Institute, said in an interview with the Soil Science Society of America. The Apollo 11 astronauts griped that the “particles covered everything and a stain remained even after our best attempts to brush it off.” An Apollo 12 crew member moaned that the lunar module “had so much dust that when I took my helmet off, I was almost blinded.”

Moondust may look soft and pillowy, but it’s actually sharp and abrasive, largely the detritus of micrometeorite impacts. With no wind or moving water on the Moon’s surface, moondust never erodes. Effectively, no natural process exists on the lunar surface that can round its edges. When astronauts inhale what is essentially finely powdered glass, it becomes a huge health hazard [PDF]: The powder is so jagged that a deep breath could cause it to lodge in the lungs and pierce the alveolar sacs and ducts [PDF], resulting in a lunar version of “stone-grinder’s disease,” or silicosis, a deadly condition that commonly killed coal miners (and still kills 100 Americans a year). To complicate matters, lunar dust also contains a lot of iron—and this iron-laden dust has recently been implicated in hypertension among Apollo astronauts [PDF].

Reports of moondust misadventures from previous Apollo missions never deterred Harrison Schmitt. After all, the Harvard-educated geologist had dedicated the better part of a decade to studying the Moon’s landscape. Working for the U.S. Geological Survey’s astrogeology department, he used telescope photos to map the Moon and planets. So when the NASA asked if any scientists were interested in visiting space, Schmitt hardly hesitated. “I thought about 10 seconds and raised my hand and volunteered,” he said in a 1999 oral history project with NASA.

No astronaut knew more about lunar geology than Schmitt. Previously, every other Apollo flyboy had had a background as a military pilot. Schmitt was the first, and only, professional scientist to walk on the Moon. As a result, the press didn’t romanticize or hype the geologist astronaut. The New York Times described the 37-year-old as a “quiet, serious bachelor who does not own a television set or a stereo.” As he trained to go to the Moon, completing a 53-week flight training course and logging 2100 hours of flying time, the scientist never imagined that he would wind up being allergic to the lunar dust and rocks he had spent years studying from afar.

Schmitt in the Lunar Roving Vehicle (LRV) during the third Apollo 17 extravehicular activity (EVA) at the Taurus-Littrow landing site. Image Credit: Getty Images

In December 1972, Schmitt landed in the Moon’s Valley of Taurus-Littrow, surrounded by mountains and endless stretches of moondust. During their first moonwalk, the lunar roving vehicle lost a fender. The tires spun, and the rover kicked up a cloud of dust.

The sediment got lodged in every wrinkle, fold, nook, and cranny of Schmitt’s spacesuit. The dust “gummed up the joints” of his suit so badly that he had trouble moving his arms. The powder chewed up his footwear, too. “The dust was so abrasive that it actually wore through three layers of Kevlar-like material on Jack’s boot,” Taylor said.

When the astronauts returned to the lunar module, it took forever to brush the dust off. Schmitt later complained [PDF] of “a lot of irritation to my sinuses and nostrils soon after taking the helmet off ... the dust really bothered my eyes and throat. I was tasting it and eating it.” The symptoms lasted for about two hours. His condition was consistent with the findings of Dr. Bill Carpentier, a NASA doctor who had evidence suggesting the dust could cause allergic responses [PDF].

Schmitt's pesky moon allergies couldn't stop his true grit. Thanks to his background as a geologist, Apollo 17 collected more rock samples than any other mission. One sample, the 4.2-billion-year-old hunk of rubble called “Troctolite 76535,” later helped unlock secrets of the Moon’s magnetic field [PDF].

Schmitt also discovered bright orange beads of volcanic glass on the Moon’s surface. Not only did these samples prove that the Moon was once volcanically active, they also provided evidence that it contained water. And before they packed for home, Schmitt and his fellow Apollo 17 astronauts snapped a photo of Earth. Today, it’s one of the most iconic photographs of our home: the Blue Marble.