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Health & Science

Space travel’s dark cloud; Tasting what you breathe; How the leopard got its spots; Shaken (not stirred) fur

Space travel’s dark cloudSpace tourism is heating up, but will it scorch the planet too? Within three years, New Mexico’s Spaceport America, which opened its first runway in October, expects to launch two flights a day into suborbital space for citizens and researchers with a hankering for high-altitude travel. But increased rocket exhaust from such trips could alter the climate, a new study warns. The problem is twofold: First, the rockets spew black carbon, which absorbs sunlight and warms the atmosphere; second, the heat-trapping rocket exhaust is injected directly into the stratosphere, where it lingers for years, accumulating with each additional space trip. The study estimates that the emissions produced by 1,000 suborbital flights a year—the likely traffic in 2020—would produce a black cloud that could alter wind patterns, raise temperatures at the poles, and accelerate the melting of sea ice. More research is needed, but the study clearly identifies a potential problem for the industry, Martin Ross, a researcher at the Aerospace Corporation and the study’s author, tells Nature News. “There are fundamental limits to how much material human beings can put into orbit without having a significant impact.”

Tasting what you breatheYou don’t need a mouth to taste. Scientists have found that proteins capable of tasting bitterness, which were thought to be confined to taste buds in the mouth (along with those for sweet, sour, salty, and savory), are also located in the lungs. “Finding these receptors in a place where they weren’t supposed to be was pretty exciting,” study author Stephen Liggett, a pulmonologist at the University of Maryland, tells Livescience.com. The researchers had set out to study how the smooth muscles of the lungs relax and contract; the discovery of taste proteins “was so unexpected that we were at first quite skeptical.” The lung proteins aren’t clustered together, as they are in the mouth; nor do they send direct signals to the brain, as taste buds do. But on detecting bitter airborne molecules, they prompt the airway to open “more profoundly than any known drug” used for treating asthma, Liggett says. Indeed, the discovery could lead to new asthma drugs, as researchers hunt for bitter compounds that can be turned into aerosols and inhaled.

How the leopard got its spotsRudyard Kipling got it half right. As it happens, the leopard didn’t get its spots from a human handprint (as Kipling’s Just So Stories suggested). But the spots do seem to be an adaptation resulting from life spent in Kipling’s “trees and bushes and stripy, speckly, patchy-blatchy shadows.” Intrigued by the dramatically different coat patterns among closely related cat species, including lions, tigers, leopards, and jaguars, researchers at the University of Bristol in the U.K. classified 35 cat species according to the size, shape, and direction of their markings. Then they compared the coats to photo images of the cats’ habitats. The process revealed that coat patterns offer camouflage that corresponds with remarkable specificity to the habitat in which a cat lives and hunts. Spotted cats are at home in trees and dappled forests, whereas cats of the open plains—lions—are, well, openly plain. This feline camouflage evolves over a short period of time, allowing cats to adapt relatively quickly to environment. The only real anomaly is the cheetah, a spotted cat of the open savannah. However, the cheetah’s hunting strategy doesn’t much rely on camouflage, study author William Allen tells New Scientist. For the cheetah, securing dinner is purely a function of speed.

Shaken (not stirred) furThe next time a wet dog shakes itself dry all over your living room, give it credit: It’s drying itself with optimal efficiency, physicists say. Water clings to an animal’s hair by surface tension; to eject the liquid, the animal must generate an even greater centripetal force, by shaking. The process fits a fairly simple mathematical model, which indicates that smaller animals need to shake faster to produce the necessary force. To confirm the math, researchers at the Georgia Institute of Technology videotaped 40 wet, hairy animals—lab rats, dogs, even a tiger from the zoo—as they shook themselves dry. The scientists found that bigger animals indeed shake more slowly: While a mouse gyrates back and forth 27 times per second (27 hertz) to get itself dry, a grizzly bear does so only four times per second (4 hertz). “The animals are shaking at optimal frequencies,” team member David Hu tells Science News. “I think it’s pretty amazing they can do that.” It’s also a lifesaver; if an animal didn’t shake the water free, “it would have to use 25 percent of its daily calories to heat its body to get rid of the water,” says Hu. “Every time they got wet they would get hypothermia and die.”

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