SCIENCE February 2021 special edition
National Geographic
THE BEST
INVESTIGATORS Nadia Drake Natasha Daly Liz Langley
Hostile Planet Explainer Reference & More
04 THE FUTURE OF SPACEFLIGHT
FROM ORBITAL VACATIONS TO HUMANS ON MARS
NASA aims to travel to the moon again—and beyond. Here’s a look at the 21st-century race to send humans into space.
06 ECHOLOCATION IS NATURE’S BUILT-IN SONAR. HERE’S HOW IT WORKS.
From beluga whales to bats and even to humans, many animals make sounds that bounce back from objects to help with navigation and hunting.
08 HOW THE OCEANS HAVE BECOME
HOSTILE FOR ANIMALS
Climate change and overfishing have rocked life in the ocean— but some species fare better than others.
THE FUTURE OF SPACEFLIGHT FROM ORBITAL VACATIONS TO HUMANS ON MARS NASA aims to travel to the moon again—and beyond. Here’s a look at the 21st-century race to send humans into space.
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elcome to the 21st-century space race, one that could potentially lead to 10-minute space vacations, orbiting space hotels, and humans on Mars. Now, instead of warring superpowers battling for dominance in orbit, private companies are competing to make space travel easier and more affordable. This year, SpaceX achieved a major milestone—launching humans to the International Space Station (ISS) from the United States—but additional goalposts are on the star-studded horizon. Private spaceflight Private spaceflight is not a new concept. In the United States, commercial compa-
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nies played a role in the aerospace industry right from the start: Since the 1960s, NASA has relied on private contractors to build spacecraft for every major human spaceflight program, starting with Project Mercury and continuing until the present. Today, NASA’s Commercial Crew Program is expanding on the agency’s relationship with private companies. Through it, NASA is relying on SpaceX and Boeing to build spacecraft capable of carrying humans into orbit. Once those vehicles are built, both companies retain ownership and control of the craft, and NASA can send astronauts into space for a fraction of the cost of a seat on Russia’s Soyuz spacecraft. SpaceX, which established
a new paradigm by developing reusable rockets, has been running regular cargo resupply missions to the International Space Station since 2012. And in May 2020, the company’s Crew Dragon spacecraft carried NASA astronauts Doug Hurley and Bob Behnken to the ISS, becoming the first crewed mission to launch from the United States in nearly a decade. The mission, called Demo-2, is scheduled to return to Earth in August. Boeing is currently developing its Starliner spacecraft and hopes to begin carrying astronauts to the ISS in 2021. Other companies, such as Blue Origin and Virgin Galactic, are specializing in sub-orbital space tourism. Test launch video from inside the cabin of Blue Origin’s
New Shepard shows off breathtaking views of our planet and a relatively calm journey for its first passenger, a test dummy cleverly dubbed “Mannequin Skywalker.” Virgin Galactic is running test flights on its sub-orbital spaceplane, which will offer paying customers roughly six minutes of weightlessness during its journey through Earth’s atmosphere. With these and other spacecraft in the pipeline, countless dreams of zero-gravity somersaults could soon become a reality—at least for passengers able to pay the hefty sums for the experience. A new era in spaceflight By moving into orbit with its Commercial Crew Program and partnering with private
companies to reach the lunar surface, NASA hopes to change the economics of spaceflight by increasing competition and driving down costs. If space travel truly does become cheaper and more accessible, it’s possible that private citizens will routinely visit space and gaze upon our blue, watery home world—either from space capsules, space stations, or even space hotels like the inflatable habitats Bigelow Aerospace intends to build. The United States isn’t the only country with its eyes on the sky. Russia regularly launches humans to the International Space Station aboard its Soyuz spacecraft. China is planning a large, multi-module space station capable of housing three taikonauts, and has already
launched two orbiting test vehicles—Tiangong-1 and Tiangong-2, both of which safely burned up in the Earth’s atmosphere after several years in space. Now, more than a dozen countries have the ability to launch rockets into Earth orbit. A half-dozen space agencies have designed spacecraft that shed the shackles of Earth’s gravity and traveled to the moon or Mars. And if all goes well, the United Arab Emirates will join that list in the summer of 2020 when its Hope spacecraft heads to the red planet. While there are no plans yet to send humans to Mars, these missions— and the discoveries that will come out of them—may help pave the way.
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ature’s own sonar system, echolocation occurs when an animal emits a sound wave that bounces off an object, returning an echo that provides information about the object’s distance and size.
Some people can also echolocate by clicking their tongues, a behavior shared by only a few other animals, including tenrecs, a shrew-like animal from Madagascar, and the Vietnamese pygmy dormouse, which is effectively blind.
Over a thousand species echolocate, including most bats, all toothed whales, and small mammals. Many are nocturnal, burrowing, and ocean-dwelling animals that rely on echolocation to find food in an environment with little to no light. Animals have several methods for echolocation, from vibrating their throats to flapping their wings.
Bat signals
Nocturnal oilbirds and some swiftlets, some of which hunt in dark cave environments, “produce short clicks with their syrinx, the vocal organ of birds,” Kate Allen, a postdoctoral fellow in the Department of Psychological and Brain Studies at John Hopkins University, says by email.
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Bats are the ultimate poster animal for echolocation, using their built-in sonar to pursue fast-flying prey at night. Most bats, such as the tiny Daubenton’s bat, contract their larynx muscles to make sounds above the range of human hearing—the batty equivalent of a shout, Allen says. Bat calls vary wildly among species, allowing them to distinguish their voices among other bats in the neighborhood. Their calls are also specific to a particular environment and prey type: The European bat “whispers” in the
presence of moths to avoid detection. Some moths, though, have evolved their own defenses against echolocating bats. The tiger moth flexes the tymbal organ on either side of its thorax to produce clicks, which jams bat sonar and keeps the predators at bay. As expert echolocators, some bats can zero in on objects as small as 0.007 inch, about the width of a human hair. Because insects are always on the move, bats have to click continuously, sometimes making 190 calls a second. Even with such difficult quarry, the predators can still eat half their weight in insects each night. Leaf-nosed bats make echolocation calls through their large, intricately folded noses, which helps focus sounds that bounces back. Some species can also rapidly change their ear shape to accurately pick up incoming signals. A few fruit bats, such as the South Asian lesser dawn bat, even make clicks by flapping their wings, a recent discovery. Ocean soundwaves Echolocation is a logical strategy in the ocean, where sound travels five times faster than in air. Dolphins and other toothed whales, such as the beluga, echolocate via a specialized organ called the dorsal bursae, which sits at the top of their head, close to the blowhole. (Read how whales have a “sonar beam” for targeting prey.)
Laboratory. Another fat deposit, stretching from a whale’s lower jaw up to its ear, clarifies the echo that returns from prey, such as fish or squid. Harbor porpoises, a favorite prey of orcas, make extremely speedy, high-frequency echolocation clicks that their predators can’t hear, allowing them to remain incognito. Most marine mammal echolocation sounds are too high for humans to hear, with the exception of sperm whales, orcas, and some dolphin species, Lee adds. Navigating by sound In addition to hunting or self-defense, some animals echolocate to navigate through their habitats. For instance, big brown bats, which are widespread throughout the Americas, use their sonar to weave their way through noisy environments, such as forests abuzz with other animal calls. Amazon river dolphins may also echolocate to move around tree branches and other obstacles created by seasonal flooding, Lee says. Most humans who echolocate are blind or vision-impaired and use the skill to go about their daily activities. Some make clicks, either with their tongues or an object, like a cane, and then navigate via the resulting echo. Brain scans of echolocating humans show the part of the brain that processes vision is employed during this process. (Read how blind people use sonar.) “Brains don’t like undeveloped real estate,” Allen says, so “it’s too metabolically expensive to maintain” echolocation in people who don’t need it. Even so, humans are remarkably adaptable, and research shows that, with patience, we can teach ourselves to echolocate.
A fat deposit in this area, called the melon, decreases impedance, or resistance to soundwaves, between the dolphin’s body and the water, making the sound clearer, says Wu-Jung Lee, a senior oceanographer at the University of Washington Applied Physics
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HOW THE OCEANS HAVE BECOME HOSTILE FOR ANIMALS Climate change and overfishing have rocked life in the ocean—but some species fare better than others.
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raditionally, the ocean wasn’t all that hostile of a place to live. The species that make the ocean their home have evolved over millennia to thrive in its depths.
What seems mind-boggling to us—a fish’s ability to live five miles under the sea, for instance—is just life for other animals. “That environment’s not hostile to them—its like us being in our living rooms,” says Matthew Savoca, a postdoctoral researcher at Stanford University’s Hopkins Marine Station, in Monterey. Swimming around with up to six male fish permanently fused to her body, for example, is just a normal part of life for a female anglerfish. A male digs his teeth into a female and every one of his organs, except his testes, withers away until he’s just a parasite hanging off her body. Nothing out of the ordinary—it’s just part of deep-sea living for an anglerfish. Although oceans do change over time, such as when Earth has cycled in and out of ice ages, those changes happen gradually, and species evolve to cope. “But humans hurt the [ocean] in a global way, whether through overfishing or plastics or whatever—and we do it very quickly,” Savoca says. “It’s a frequent, unabating, constant assault.” For many animals, evolution simply cannot keep up with human-driven change. Plastic, unsustainable fishing, ocean acidification, and warming waters, among other things, have all made the ocean a more hostile place for the animals that live there. (Read about the animals that thrive in hostile mountain conditions.) Long-living animals, like albatrosses and blue whales, evolve very slowly over thousands of years, because their generations are spaced so far apart. But plastic, for example, has only existed for 60 years—essentially the lifespan of a single animal. It could take 60,000 years for generations of these long-living species to begin to adapt to living with it, says Savoca. The ocean has essentially become a minefield of plastic. (Read about the pregnant whale
that died with 50 pounds of plastic in her stomach.) Animals that reproduce frequently and have short lifespans, like small fish and plankton, evolve more rapidly. “Their species might be saved by evolution,” says Savoca. How animals live in the ocean also influences their ability to adapt to change. Generally, animal species fall somewhere along a spectrum. At one end are the specialists, which are typically apex predators, such as orcas and sharks, that are evolved to thrive in a very particular environment and eat specific prey. Because their focus is so narrow, they’re pros at exploiting their habitat, but they’re terrible at adapting to change, Savoca says. As their environments change or their primary food source gets depleted, they’re thrown into unfamiliar circumstances they struggle to adapt to. Then there are the generalists—Atlantic cod and flounder, for instance—that are “jacks of all trades, master of none,” says Savoca. They’re able to thrive in many different environments and eat a varied diet. While generalists don’t dominate their surroundings like apex predators, they can do adapt when their environment becomes unpredictable. But advantages only go so far. Killing campaigns, such as centuries of cod fishing or whaling in the North Atlantic, affect generalist and specialist species equally. And this “slash and burn killing,” says Savoca, creates ripple effects throughout entire ecosystems and food chains. “We whaled out 95 percent of whales in less than 100 years, which is the most rapid loss of biomass in history,” says Savoca. “Humans are such efficient killing machines that [we’re capable] of removing entire species from our planet in less than a century.”
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“Live Curious”