Mary Roach - Packing for Mars

“You’re investigating a rather unusual aspect of spaceflight,” he said. He didn’t remember, but he did recall comments made by some of the Apollo hatch-openers. “They’d get a whiff of the inside of that spacecraft and it smelled…”—Lovell’s gentlemanly instincts intervened—“different than the fresh ocean breezes outside.”

Underarm sweat supplies both food and lodging for bacteria. Eccrine sweat is mostly water; it provides the moisture bacteria need to thrive. Protein-rich apocrine secretions are the twenty-four-hour diner. (Though eccrine sweat does contribute edible elements whose breakdown products are, as Leyden says, “part of the overall bouquet, if you will.” It’s a milder, lockerroomy smell.)

The armpit is not entirely the bacterial paradise it would seem to be. Sweat has natural antimicrobial properties. Though they don’t by any means render the skin sterile, there are limitations to what can grow there. That may be one reason why the Air Force boys’ odors hit a plateau, rather than growing ever worse as the weeks wore on. The technical report states that the men’s body odor reached its “maximum height” at seven to ten days, and then began to subside. Height is an odd attribute for smell, but it’s possible to imagine how in this case the odor could seem to be taking on physical proportions, growing taller, sprouting heads, limbs, quills.

Soviet space biologist V. N. Chernigovsky, in 1969, carried out a restricted-bathing experiment of his own, this one including bacteria colony counts. The bacteria populations in subjects’ armpits and groins plateaued somewhere between the second and third weeks. At which point there were roughly three times as many colonies as on freshly washed skin. (Except on the feet [62] Because of all the sweat and dead skin (calluses), the bottoms of the feet and the spaces between the toes are a Mecca for bacteria—high numbers, much more variety. One class of dead-skin-eating bacteria, L. brevis , excretes compounds that smell like ripe cheese. Though it may be technically more accurate to say that certain ripe cheeses smell like feet: Cheesemakers routinely inoculate certain of their creations with L. brevis . and buttocks, where there were seven to twelve times as many.) A Navy study turned up similar findings; here some subjects’ bacteria counts even began to drop after two weeks.

The other explanation for the odor plateau is that the men’s body odor had become so strong that it was impossible for whoever was judging it to detect incremental changes. Weber’s Law provides the explanation. The detection threshold for changes in a particular smell (or sound or sensation) varies according to the intensity of the background smell (or sound or sensation). Say you are in a noisy restaurant. If the noise level rises a few decibels, you can’t tell. Had the room been quiet, you could easily tell. If someone’s armpits have been shouting for a few days, it’s hard to tell when they’re shouting a little louder. Jim Leyden gives the example of his son, who was a rower in college. One year the team decided they were going to wear the same rowing outfits until they lost. “Well, they became national champions that year. You could not get near that boat. The smell may have plateaued, but as far as I was concerned, it was just constantly horrible.”

Eventually the mind stops registering the body’s smell. In Leyden’s words, “It’s going, ‘I don’t need to bother telling you this anymore.’” Unfortunately for a group of AMRL subjects in a twenty-day no-bathing Apollo simulation, this point didn’t arrive until day eight.

NASA would have done well to add body odor anosmia to its list of desired astronaut traits. Some people [63] And possibly deer. A 1994 issue of Crop Protection details the failed but entertaining efforts of botanists at the University of Pennsylvania to deter white-tailed deer by dousing an assortment of ornamental shrubbery with 3-methyl-2-hexanoic acid. Which raises the unusual marketing question, Will a homeowner abide a rhododendron that smells like BO? are genetically unable to smell (i.e., they’re anosmic to) one or both of the two BO heavies: 3-methyl-2-hexanoic acid and androstenone. “Have you ever been on an elevator with someone and wondered, ‘How can he come on here smelling like that?’ Well, he may be anosmic to his odor,” Leyden says. “And those of you who have never experienced that, you may be one of those people on the elevator that everyone’s wondering about.”

Aside from body odor, the most common contributor to what one researcher called “perceptions of personal dirtiness” is not dirt per se, but bodily emanations that have built up on the skin: grease, sweat, and scurf, [64] A.k.a., shed skin. Dorland’s Medical Dictionary defines scurf as “a branny substance of epidermic origin”—an evocative pairing of dander and breakfast cereal. Try new Kellogg’s Dandruff Flakes! to be specific. Where you have hair, you have sebaceous glands; that is to say, everywhere but your palms and the soles of your feet, where greasiness is a slip, trip, and fall hazard and thus a survival liability.

The 1969 Soviet restricted-hygiene experiments monitored the build-up of oils, or sebum, in male volunteers. (Here, in addition to not bathing, the subjects had to spend “most of their time sitting in an armchair.” The simulated astronaut of the sixties was a stinky guy watching TV in a dirty undershirt.) For the first week without bathing, the skin’s oiliness remained constant. Why didn’t it increase? Because clothes are surprisingly effective absorbers of sebum and sweat. The Soviet researchers collected wash water from the subjects’ skin in one basin, and wash water from their clothes in another. They compared the amounts of grease, sweat, and dander in the two tubs. Eighty-six to 93 percent of the skin’s emanations were in the water where the clothing had been. In other words, all but 7 to 14 percent of the men’s filth had been absorbed by the fabric of their clothing. This was true of cotton, cotton-rayon blend, and, to a lesser extent, wool.

The Soviet findings help explain the lackadaisical hygiene practices of the sixteenth and seventeenth centuries. Renaissance doctors discouraged washing with water. Removing the protective layer of oil from the skin, they believed, left the bather vulnerable to plagues, tuberculosis, and a host of other ills then believed to spread via “miasmas” that seeped into the body through the pores. Queen Elizabeth I, her era’s version of a clean freak, famously wrote, “I bathe once a month, whether I need it or not.” Many let it go a year.

But here’s the thing: Instead of showering once or twice a day, Renaissance men and women would change their undersmocks and chemises. The men of Gemini VII and the AMRL chamber, on the other hand, couldn’t change their underthings. The authors of the AMRL chamber study noted that the subjects’ clothes eventually began “sticking to the…groin and other body fold areas and were very odorous and starting to decompose,” a condition described as “very troublesome.” Lovell told me the Gemini VII long johns were in bad shape by the end of the mission. “They were,” he allowed, “pretty smudged around the crotch area”—even more so than those of the average person who didn’t bathe or change his underwear for two weeks, because the average person wasn’t testing a new NASA urine management system that “leaked considerably sometimes.” For instance, on the second day of the flight, when Lovell, reporting to Mission Control that he was ejecting urine from the spacecraft, noted, “Not too much of it; most of it’s in my underwear.”

At a certain point, clothes reach their saturation point, and sebum begins to accumulate on the skin. According to the Soviet researchers, who monitored oil levels on subjects’ chests and backs, it takes five to seven days for a cotton garment to reach this point. It is difficult to pinpoint the day when the Gemini VII astronauts began to notice the buildup on their skin. By day ten, they were “starting to itch” and “getting a little crummy” in the scalp and crotch. Here they are on day twelve: