The dwarf planet Ceres, photographed by NASA’s Dawn orbiter. False-color renderings highlight differences in its surface materials. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dwarf planet Ceres has salty water and appears geologically active

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<p>Ceres, the biggest asteroid in our solar system, now has another bragging right. According to new research, Ceres has water seeping onto its surface, suggesting the presence of an ancient <a href="https://www.pbs.org/wgbh/nova/article/pluto-ocean-giant-thermos/">underground ocean</a>.</p><p>The new findings, documented in seven studies published Monday in the journals Nature Astronomy, Nature Communications, and Nature Geoscience, suggest that, despite being cold and salty (and lacking an atmosphere), Ceres is geologically active.</p><p>Also known as a <a href="https://mass.pbslearningmedia.org/resource/nvcp-sci-studypluto/why-study-pluto-and-dwarf-planets/">dwarf planet</a>, Ceres dwells in the asteroid belt sandwiched between Mars and Jupiter. At about 588 miles across, it’s about the third of the width of our moon. <a href="https://solarsystem.nasa.gov/missions/dawn/overview/">NASA’s Dawn Orbiter</a> studied Ceres thoroughly from March 2015 to November 2018, getting within 22 miles of the asteroid in its final weeks before running out of fuel. During Dawn’s final year of orbit, it collected high-resolution images of Ceres, which a team of Italian researchers has now analyzed.</p><p>The images illustrate the briny liquid seeping out on Ceres’ surface, “as well as mounds and hills that formed when ice melted and refroze after an asteroid impact about 20 million years ago,” Michael Greshko <a href="https://www.nationalgeographic.com/science/2020/08/dwarf-planet-ceres-churns-briny-fluids-icy-volcanoes-nasa-dawn/">reports for National Geographic</a>. Researchers found that the liquid comes from an underground reservoir of saltwater 25 miles beneath Ceres’ Occator Crater. The reservoir may be hundreds of miles wide.</p><p>Occator is a 57-mile-wide impact crater that’s approximately 20 million years old and dappled with bright spots of salt. This week’s findings suggest that these salt deposits formed when cold underground brine oozed out onto the crater’s surface as recently as 1.2 million years ago.</p>
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<p>“Bulging mountains and hills also support the idea that Ceres experiences a kind of ice-cold cryovolcanism, with briny mud or slush acting like molten lava does on Earth,” Greshko writes. “In one region of Occator's crater floor, Dawn spotted hints that brines had dribbled out of ice volcanoes within the past few decades, if not more recently.”</p><p>“And the Dawn data shows that the dehydrated salts actually still have a bit of water in them,” Neel V. Patel <a href="https://www.technologyreview.com/2020/08/11/1006447/ceres-largest-asteroid-dwarf-planet-underground-ocean-salty-water/">reports for MIT Technology Review</a>. “That suggests whatever geological activity is encouraging these deposits might still be happening, which would mean Ceres is still an active world.”</p>
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<figcaption><p>A mosaic image of Ceres' Occator Crater using false color (in red) to highlight the recently exposed saltwater pushed up from a deep reservoir under the dwarf planet's crust. Image credit: NASA, JPL-Caltech, UCLA, MPS, DLR and IDA</p>
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<p>However, not all scientists are convinced that Ceres is home to a subsurface ocean. Jim Zimbelman, a Smithsonian Institution geologist who was not involved in the latest studies told Scientific American that he remains “pretty skeptical.” Water on the dwarf planet’s surface doesn’t entail the presence of an underground ocean but perhaps a smaller reservoir, some skeptics believe. Mikhail Zolotov of Arizona State University, who was consulted for one of the seven studies but was not directly involved in the work, “dismisses the conclusion that Ceres hosts a brine reservoir as ‘wishful thinking,’” Scott Hershberger <a href="https://www.scientificamerican.com/article/claims-of-lsquo-ocean-rsquo-inside-ceres-may-not-hold-water/">reports for Scientific American</a>. In a paper published in January, Zolotov expressed that the presence of water in the form of ice is not required to explain Ceres’ density and that the body’s shape and composition could be explained by organic matter, chondrites (stony, non-metallic meteorites), and a high surface porosity.</p><p>But many scientists agree that the possibility of a brine layer on Ceres is compelling and that the Dawn mission, which provided the discovery, was groundbreaking. Dawn was the first probe to orbit two objects beyond Earth’s immediate neighborhood, having visited asteroid Vesta before Ceres. Along with NASA’s <a href="https://www.pbs.org/wgbh/nova/video/new-horizons-makes-historic-flyby-on-new-years-day/">New Horizons spacecraft</a>, which <a href="https://www.pbs.org/wgbh/nova/video/pluto-and-beyond/">flew by Pluto</a> in 2015 and <a href="https://www.pbs.org/wgbh/nova/article/nasa-celebrates-most-distant-space-encounter/">space rock Arrokoth</a> on New Year’s Day of 2019, Dawn has “shown that small, icy bodies are far more active than once thought,” Greshko writes, “stretching how scientists imagine the geology of dozens of alien worlds.”</p>
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<p>High-resolution images from NASA’s Dawn Orbiter suggest our solar system’s largest asteroid may have an ancient underground ocean, but some scientists are skeptical.</p>

Depending on how you feel about squirrels, you might delight or despair to hear that we've got a lot in common with these woodland wunderkinds. Image Credit: Dgwildlife, iStock

The 10 most popular NOVA stories of 2019

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<h3>10. FDA approves first major new depression treatment in decades</h3><p>In March, the U.S. Food and Drug Administration approved a drug called esketamine, the first major new depression treatment to hit the market in decades. The drug is designed specifically for people suffering from the most extreme forms of treatment-resistant depression and is administered only in certified treatment centers via a nasal spray (rather than an oral pill). Esketamine is specifically for patients who have tried two other antidepressants with no success. </p><p>Janssen Research &amp; Development, the developer of the drug, hopes that by targeting the neurotransmitter glutamate, esketamine can offer rapid antidepressant effects, much like its cousin ketamine does. Experts’ opinions on the new drug, however, are split.</p><p><a href="https://www.pbs.org/wgbh/nova/article/fda-approves-first-major-new-depression-treatment-in-decades/">Read the full article</a>.</p><p></p>
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<figcaption><p>The Milky Way's population of Cepheid stars suggests that our galaxy is a twisted disk. Image Credit: J. Skowron / OGLE / Astronomical Observatory, University of Warsaw</p>
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<h3>9. A new 3D map of the Milky Way flaunts our galaxy’s warped shape</h3><p>If you ever thought the Milky Way was a flat, featureless pancake, think again. This summer, we learned that the Milky Way is bent out of shape. In fact, it seems to be warped into a wave much like a beach towel being shaken free of sand.</p><p>Finding definitive proof of the Milky Way’s warp was no simple task. While astronomers have gotten pretty good at snapshotting galaxies in more distant regions of the universe, here on Earth we don’t have the best vantage point to get a birds-eye view of the celestial structure that surrounds us: Just imagine trying to map a forest by being dropped down into its center.</p><p><a href="https://www.pbs.org/wgbh/nova/article/milky-way-3d-map-cepheids/?linkid=71919590">Read the full article.</a></p><p></p>
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<figcaption><p>Microwaving grapes is a surefire way to get your hands on some plasma—and an elevated risk of burning down your apartment. </p>
<div class="credit"><p>Image Credit: Hamza K. Khattak, Trent University; PNAS</p></div>
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<h3>8. How does microwaving grapes create plumes of plasma?</h3><p>If you’ve been tempted ever to create some plasma—and potentially burn down your home in the process—we learned this year that grapes and a microwave are the ticket. </p><p>Or, alternatively, you can turn to YouTube and (safely) watch researchers as they puzzle out the physics behind DIY plasma. Spoiler: The result is a swarm of subatomic particles that clash and collide, often emitting roiling blobs of light and heat that can resemble molten fire.</p><p><a href="https://www.pbs.org/wgbh/nova/article/how-does-microwaving-grapes-create-plumes-plasma/">Read the full article</a>. </p><p></p>
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<figcaption><p>European robins make harrowing, cross-continental migrations to escape harsh winters. To guide their way, these birds and others may use quantum entanglement to "read" Earth's magnetic field. Image Credit: Frank Vassen, flickr</p>
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<h3>7. A bird’s eye view of quantum entanglement</h3><p>Every year, billions of birds make harrowing, cross-continental migrations. But how do they know where to go?</p><p>Scientists have known for a while that Earth’s magnetic field lends a helping hand. But this year, some researchers gleaned insight into how, suggesting that at some point in history, avian evolution tapped into quantum mechanics.</p><p><a href="https://www.pbs.org/wgbh/nova/article/birds-quantum-entanglement/?linkid=69249680">Read the full article</a>.</p><p></p>
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<figcaption><p>An artistic three-dimensional representation cyclo[18]carbon, a ring of 18 carbon molecules. Image Credit: IBM Research</p>
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<h3>6. A new form of carbon is born—on a bed of salt</h3><p>In August, a new molecule called cyclo[18]carbon officially joined the carbon club. The creation, imaging, and analysis of cyclo[18]carbon helped settle decades of debate on the structure and properties of the molecule, which some researchers doubted could even be stably made in a laboratory setting.</p><p>Historically, researchers’ attempts to generate cyclocarbons in the lab resulted in volatile gas, too ephemeral to rigorously study. But the recent breakthrough shows that cyclocarbons can be generated by pruning carbon and oxygen atoms off a more complex molecule at extremely cold temperatures. Starting with a molecule made up of 24 carbons linked to six oxygens, researchers at IBM Research and Oxford University were able to generate a final structure of 18 carbons—the smallest possible ring of carbons predicted to be stable by theoretical models. </p><p><a href="https://www.pbs.org/wgbh/nova/article/cyclo18carbon/">Read the full article</a>.</p>
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<figcaption><p>A wild silver-backed chevrotain appeared! Image Credit: SIE/GWC/Leibniz-IZW/NCNP Copyright holder: Andrew Tilker</p>
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<h3>5. Feast your eyes on the first-ever photos of a silver-backed chevrotain in the wild</h3><p>Once upon a time, there was a fanged, cat-sized deer-like creature with a glossy silver back. Then, like many legendary beasts, it was “lost to science.”</p><p>Until this November, that is. Though Western researchers have known about the skittish silver-backed chevrotain for more than a century, they’ve only managed to collect five specimens, all corpses obtained from hunters in Vietnam. The last of these appeared nearly three decades ago. But this year, with the help of local knowledge and a cluster of well-placed camera traps, Global Wildlife Conservation biologist Andrew Tilker and his team snapped the first-ever photos and videos of the silver-backed chevrotain in the wild.</p><p><a href="https://www.pbs.org/wgbh/nova/article/silver-backed-chevrotain-rediscovered-vietnam/?linkid=76835332">Read the full article</a>.</p><p></p><p></p>
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<figcaption><p>As Alzheimer's disease progresses, communication between brain cells breaks down. New research suggests that one possible cause for this deterioration may be a brain infection by <i>Porphyromonas gingivalis, </i>a bacterium known for causing gum disease. Image Credit: National Institute on Aging/NIH, flickr</p>
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<h3>4. Could Alzheimer’s begin with bacteria that cause gum disease?</h3><p>In individuals affected by Alzheimer’s disease, communication between brain cells breaks down over time. Early this year, a study suggested one peculiar potential cause for this deterioration: a brain infection by a bacterium known for causing gum disease.</p><p>In January, researchers reported that the bacterium, <i>Porphyromonas gingivalis</i>, might be capable of traversing the path from mouth to brain, where it can trigger chemical changes that damage cognitive function. These findings suggest that some cases of Alzheimer’s might have an infectious cause—and a new drug that blocks this process is now in clinical trials.</p><p><a href="https://www.pbs.org/wgbh/nova/article/alzheimers-bacteria-gum-disease/?no-cache=&amp;linkid=62727014">Read the full article</a>.</p><p></p><p></p>
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<figcaption><p>A complex tangle of social factors may encourage girls to prioritize verbal skills from a young age. But being excellent at reading doesn’t make a person bad at math—no matter their gender. Image Credit: Imgorthand, iStock</p>
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<h3>3. Girls’ superb verbal skills may contribute to the gender gap in math</h3><p>Being excellent at reading doesn’t make a person bad at math—no matter their gender.</p><p>According to previous studies, including <a href="https://psycnet.apa.org/doiLanding?doi=10.1037%2Fa0021276">a meta-analysis</a> that probed gender differences in recent studies of mathematics performance, girls are just as good at math as boys are. But a complex amalgam of social factors may encourage girls to prioritize verbal skills from a young age, a study published in July suggests.</p><p>Drawing on data from more than 300,000 high school students from 64 countries, the study found that because girls’ verbal skills outshine their already high marks in math, many who do every bit as well as their male peers in mathematics still choose more humanities-centric careers.</p><p><a href="https://www.pbs.org/wgbh/nova/article/gender-gap-math-comparative-advantage/">Read the full article</a>.</p><p></p><h3>2. Six stupendous reasons to appreciate the heck out of squirrels</h3><p>Beady eyes, bushy tails, can’t lose: We’re talking squirrels. And whether you love these nut-crazed rodents or not, there’s no denying that despite being zany, squirrels are also aerodynamic and brainy.</p><p>On January 21, for Squirrel Appreciation Day, <i>NOVA</i> published a roundup of six squirrel facts—and it quickly became a fan favorite. So if you’re still in the dark about squirrel-induced electrical power outages, squirrels eating spring rolls, the power of squirrel memory, and how squirrels can give investment bankers a run for their money, here’s your ticket out.</p><p><a href="https://www.pbs.org/wgbh/nova/article/six-snippets-squirrel-science/">Read the full article</a>.</p><p></p><p></p>
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<figcaption><p>Now that's a purrfect pair. Image Credit: AkilinaWinner, iStock</p>
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<h3>1. Study finds kittens bond with their human caregivers like babies do</h3><p>Sorry, dogs: You may not be humans’ only faithful companions. Though cats have their critics, it turns out that they can be extremely social with other felines and humans alike.</p><p>In September, researchers revealed that much like human infants, cats are “attached” to their caretakers (and like babies, felines have different ways of expressing their attachment). When analyzing humans, dogs, and cats, the research team found that roughly 60 percent of infants or pets are “secure,” meaning they appear to use their caregivers as a safe base from which to explore their surroundings. Of the felines that seemed, well, insecure, fewer acted aloof or avoidant than one might expect.</p><p><a href="https://www.pbs.org/wgbh/nova/article/cats-secure-attachment/">Read the full article</a>.</p>
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<p>We’ve counted down our ten most-read articles of 2019 and found that health and medicine, physics—and of course animals—were fan-favorite topics this year.</p>

Researchers on Antarctica's Thwaites Glacier peer into a crevasse. Image Credit: Seth Campbell

Scientists find warm water beneath Antarctica’s most at-risk glacier

<p>Aurora Basinski crouches in a tent on a glacier jutting out from Antarctica, half a mile off solid land. She’s tinkering with a device called a VMP, which measures water temperature and salinity, when she starts cursing.</p><p>Thirty-six hours before, a storm moved off West Antarctica’s Thwaites Glacier, giving Basinski and her fellow investigators a tiny, critical window of time. They dug their equipment out of snow drifts as tall as themselves and on January 8 began hot-water drilling a 14-inch-wide hole down into the glacier. </p>
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<p>Basinski is one of about 50 researchers working on the eastern tongue of Thwaites Glacier as part of the International Thwaites Glacier Collaboration (<a href="https://thwaitesglacier.org/">ITGC</a>). The $50 million, five-year study is supported by the U.S. Antarctic Program and the British Antarctic Survey. The goal is to better understand how climate change is affecting Thwaites, nicknamed the “doomsday glacier” because it’s melting so quickly. Researchers will deploy all manner of scientific instruments across its surface. But to really understand what’s happening with Thwaites, they also need to send instruments into the water below it. </p><p>And that means drilling a hole through 2,000 feet of ice.</p><p>The team on the aptly named <a href="https://thwaitesglacier.org/projects/melt">MELT project</a> drills in shifts for 36 hours and by the time they hit water below the glacier, their borehole is twice as tall as the Eiffel Tower. Basinski and her advisor, New York University mathematician and ITGC Principal Investigator David Holland, immediately begin a “science shift,” trading in drilling tools for fine-tuned scientific instruments. It’s already the middle of the night, and when Basinski’s VMP acts up, she's forced to stay awake fiddling with the device for another 12 hours. </p><p>“You want to get good data,” she says. “You have one shot.”</p>
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<figcaption><p>Winds blow through the ITGC research camp where David Holland and Aurora Basinski conduct their work. Image Credit: David Holland and Aurora Basinski</p>
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<h3>Runaway Glacier</h3><p>Thwaites Glacier is a fragile piece of one of the most <a href="https://www.scientificamerican.com/article/antarctic-glacier-has-retreated-3-miles-in-22-years/">rapidly changing</a> places on Earth. That pace of change is what caught people’s attention about two decades ago, Holland says. Thwaites’ elevation falls by several feet every year. Scientists theorize that as the leading edge of a glacier retreats farther inland, the thicker ice above begins flowing down toward the sea faster. This creates a runaway effect of retreat, thinning, further retreat, and, ultimately, collapse.</p><p>“If a glacier collapse occurs in the next decade to century, or centuries, it will be here,” Holland says. “And it will be triggered by warm water and be unstoppable.” Thwaites could also trigger ice loss in connecting areas of West Antarctica, scientists believe. “Everything that we’ve seen, particularly from satellite and remote sensing in the last decade or so points to this area becoming more active,” says Paul Cutler, program director of glaciology, ice core science and geomorphology at the National Science Foundation. “And it’s not acting in isolation. If it starts rapidly retreating, it starts acting on the neighboring glaciers as well.”</p><p>The ice shelf that Basinski, Holland, and the rest of their team shared from mid-December to mid-January is like an ice cube in a glass of water. Because it’s over the ocean, it won’t directly contribute to sea level rise. But about half a mile away is what scientists call the grounding zone, where this “flowing” piece of Thwaites sitting on the water meets the “grounded” part attached to the seafloor.</p><p>It’s this ice atop solid ground—a massive ice cube on a countertop—that climatologists worry about. “The ice cube I’m standing on is holding [back] the ice cube on the kitchen counter,” Holland says from Thwaites’ eastern ice shelf. </p>
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<figcaption><p>Changing winds and currents carry warm water beneath Thwaites Glacier, accelerating ice melt on its underside. As the glacier loses its grip on the seafloor, the grounding line shifts back, hastening retreat. Image Credit: International Thwaites Glacier Collaboration</p>
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<p>Already, the melting of Thwaites Glacier, which is roughly the size of Florida, accounts for 4% of global <a href="https://climate.nasa.gov/news/2680/new-study-finds-sea-level-rise-accelerating/">sea level rise</a> on an ongoing basis. And the amount of ice flowing from it and its glacial neighbors has almost doubled in the last 30 years. Current mathematical models illustrate that if it were to collapse, which scientists believe will happen in the coming decades or centuries, much of western Antarctica’s remaining ice will become unstable. </p><p>If Antarctica were to lose only Thwaites, the Earth’s oceans would rise by about two to three feet or more, researchers believe. That’s enough to cause major flooding in New York City and <a href="https://coastal.climatecentral.org/map/9/12.5321/45.4564/?theme=water_level&amp;map_type=water_level_above_mhhw&amp;contiguous=true&amp;elevation_model=best_available&amp;water_level=3.0&amp;water_unit=ft">completely engulf</a> some low-lying cities like New Orleans and Venice, Italy, with seawater.</p><p>And if the loss of Thwaites triggered the collapse of the rest of the West Antarctic Ice Sheet, the global sea level could rise by more than 10 feet. “It can feel very far away,” Andra Garner, a climate scientist at Rowan University who is not part of the ITGC, says of melting glaciers. But “coastal sea rise is a problem for communities in itself,” she says. If the seas were to rise by 10 feet, Holland says, the effects on countries like Bangladesh, coastal states like Florida, and major cities like New York, London, and Shanghai will be “profound.” </p><p>Higher seas can also mean intensified storms. “On the East Coast we’re concerned because we already see sea level rise [playing out] in the background,” says Cutler, who’s based in Virginia. “Storms are able to encroach inland.” Even a minor hurricane, which wouldn’t cause intense flooding today, Garner says, could have a much worse effect in deeper coastal waters. </p><p>And to make matters worse, storms <i>themselves</i> seem to be growing. Garner’s <a href="https://www.pnas.org/content/114/45/11861">research shows</a> that from 850 to 1850, storms similar in size to Hurricane Sandy were likely to occur about once every 500 years in New York. Today, Hurricane Sandy is what she calls a “25-year storm,” meaning one that has a 1 in 25 chance of hitting in any given year. But if our current patterns of carbon dioxide emissions continue—and glacial melt along with them—Hurricane Sandy will be a 5-year storm in New York by 2100.</p><h3>Ground Truth</h3><p><a href="https://www.climate.gov/maps-data/primer/climate-models">Climate models</a> rely on mathematics to describe how energy and matter interact in the atmosphere, on land, and in the ocean. About 30 organizations around the world, Holland says, continuously develop them to better understand the complexities of the Earth’s past, current, and future climate. But these models are limited, unable to account for the day-by-day shifting of glaciers’ grounding lines, for example, or features yet to be discovered. This leaves sea-level-rise projections with “a big asterisk called ‘Thwaites,’” Holland says. “And Thwaites is gonna run the whole show.” </p><p>That’s where the ITGC comes in. </p><p>The location, shape, and behavior of Thwaites’ grounding line, a feature that is bound to play heavily into future climate models, was unknown a decade ago. But from 2011 to 2014, Pietro Milillo of NASA’s Jet Propulsion Laboratory and his team used satellite data to map out the grounding-line retreat of Thwaites and the neighboring Pine Island, Smith, and Kohler Glaciers. </p><p>Shortly after, a team of Seoul National University scientists used remote sensing data to show that the Thwaites Ice Shelf—the part of the glacier hanging over the ocean—is disintegrating quickly and its rate of shedding ice into the sea is accelerating. That made Thwaites a “top spot” for concern, Cutler says.</p><p>Then, in January 2019, Milillo’s team made <a href="https://www.jpl.nasa.gov/news/news.php?feature=7322">a startling discovery</a>. </p><p>Their remote sensing work revealed a Manhattan-sized cavity against the grounding zone on Thwaites’ western side, a place too crevassed for scientists to conduct on-the-ground research. The existence of such a cavity suggests that warm water below Thwaites licks at an already-unstable section of its ice shelf—a phenomenon that could hasten Thwaites’ retreat, but isn’t accounted for in models, Milillo says.</p><p>His team’s findings also revealed that Thwaites’ grounding line moves by a few miles with the tides—another feature that’s not taken into account by existing climate models.</p><p>Even the boundaries of Thwaites are hard to define, says Slawek Tulaczyk, a glaciologist at the University of California, Santa Cruz and a principal investigator of the ITGC. Whereas the boundary between glacier and rock are well-defined in places like Yosemite, he says, “in Antarctica, you more or less have a sheet of ice. Thwaites is a fast-flowing piece of ice on the sides, rubbing against slow-moving ice in the middle. There is no rock wall.”</p><p>About three decades of research show that these boundaries can shift over time as the glacier widens and narrows, or the grounding line shifts. “Models aren’t great at predicting that right now,” Tulaczyk says. “It’s much easier to write code where things are set and don’t change.”</p><p>Though they lack a layer of complexity, today’s climate models do offer a glimpse into what Earth’s future might look like. For comparison, imagine planning a road trip with only a globe. You’d be able to draw a line from your starting point to where you want to end up. Once you hit the road, with a globe in hand, you could hypothetically head in the proper direction. But to successfully end up in the state, town, and street of your destination (and get traffic reports along the way), you’ll likely want something more detailed. </p><p>Similarly, climate models need another layer of complexity to better assess Thwaites’ future and its potential effects on the planet: They’ll need to evolve from globes into Google Maps.</p>
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<h3>A Glimpse Beneath the Ice</h3><p>Back on the ice in Antarctica, after 12 hours of toying with the VMP, or vertical microstructure profiler, in a research tent, Basinski and Holland finally figure out what’s wrong with the highly sensitive probe: The noise from the generators surrounding them had created electrical interference strong enough to throw off the VMP’s readings. </p><p>Once fixed, Basinski lowers the VMP—a little probe on a long wire—down the 2,000-foot borehole and into the water below. The instrument soon gets a read on turbulence, the mixing of the colder surface water and warmer, saltier, water below, a phenomenon that can stoke further melting of the glacier potentially faster than warm air can. </p>
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<figcaption><p>The 2,000-foot borehole, referred to as a “Thwaites Glacier access point,” stays covered when scientists aren’t deploying their instruments. Image Credit: David Holland and Aurora Basinski</p>
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<p>“It’s really exciting to have it in the ocean and to see the data that is coming back,” Basinski says. “It all looked good and reliable.”</p><p>Sharing this corner of Thwaites is Britney Schmidt, an ITGC principal investigator and Georgia Tech astrobiologist, and her team, which is responsible for a 12-foot torpedo-like robot called Icefin. On January 10, Schmidt and her team lean over the borehole and pull on Icefin’s tether, guiding the yellow robot out of the water and ice after six hours of exploration, its third of four trips. Icefin carries data about the temperature and salinity of the water in Thwaites’ cavity as well as the <a href="https://www.youtube.com/watch?v=dTQWCCU8CpE">first-ever images</a> from the grounding zone. Unlike the researchers’ other instruments, Icefin can be guided away from the borehole using a remote control, allowing the researchers to capture readings over a wider area.</p><p>“Deploying a complex system is never straightforward, but the robot was a champ and we actually beat our personal bests in several ways,” Schmidt said in an email. Icefin completed its two longest trips ever, venturing over a mile out from the borehole. “We actually got to the end of our tether on our second dive out there,” Schmidt wrote.</p><p>Within a matter of days, the ITGC researchers receive their first readings.</p><p>The water beneath the borehole is about 160 feet deep. The top half of it is cold water, a few degrees above freezing, and the lower half is warmer, saltier water, Basinski finds. Based on this even splitting, it would seem that turbulence—the rapid mixing of warm and cold water—is low. That means the warm water isn’t readily able to heat up the cold water above it, which could be good news for Thwaites.</p><p>But the researchers aren’t celebrating yet.</p><p>We can’t ignore the fact that this warm water is there and touching the ice, Basinski says. This warm water, she adds, is from our active heating of the atmosphere. When the atmosphere warms, wind patterns change, which ultimately affects the shape of ocean currents. Scientists already know that changing currents, which now shepherd warm water to Greenland, are to blame for much of glacial melting in Earth’s Northern Hemisphere. The same might be happening in the South at Thwaites, they fear.</p><p>And, Holland adds, not all of Thwaites behaves the same: Under its heavily-crevassed, quick-moving western tongue, it’s very possible that warm and cold water are mixing. </p>
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Aurora_David.width-990_wV8GT4O.jpg"/>
<figcaption><p>Aurora Basinski and David Holland depart from West Antarctica. Image Credit: David Holland and Aurora Basinski</p>
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<p>Now that the ITGC researchers have returned home, they’ll pore over more data, much of which is being beamed to them by tools they’ve left on the ice. Some team members plan to return to Thwaites next year or the following, or will visit for the first time. Some, like Basinski, don’t wish to return at all. “Antarctica is a lot of fun. But [returning there] would mean a lot of digging,” she says, referring to unearthing tools from a year’s worth of snow —about 10 feet.</p><p>With the information they collect over the five years of the ITGC, they hope to map out the glacier in detail. </p><p>“By doing that, we help understand what the linch pins are in the system,” Schmidt wrote in an email. “We know from a whole host of data that the climate is warming, that the ocean is warming and that Thwaites is changing rapidly, but the rates of change under the ice are uncertain without these new data.”</p><p>These data “will help beat down the uncertainty in how the system is changing,” she wrote. And that will allow scientists to make better climate predictions and society to properly respond.</p><p>Thwaites has the power to rapidly split and shed, to raise the seas, to inundate coastal cities. “The future of our planet’s sea level is tied up almost certainly with what I’m standing on and what the folks behind me are working on,” Holland said from the glacier in January, gesturing to Schmidt’s team and Icefin behind him. “The impact, around the world, will be on tens or hundreds of millions of people. And the impact in dollars is huge.” </p><p>For now, that impact comes with uncertainty. And that uncertainty is hinged on the amount of carbon dioxide we emit into the air now and moving forward, says climate scientist Andra Garner. It can feel dire, she says, but the future of Thwaites and our planet is largely in humans’ hands. “That’s our source of hope,” she says, “that we have the chance to change things.”</p><p></p>
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<p><i>NOVA science correspondent Miles O'Brien assisted in reporting this article.</i></p><p></p><p><i>Correction: A previous version of this article incorrectly stated that underneath Thwaites Glacier, a layer of warm water is sitting above colder water. Cold water is in fact above the warm water.</i></p>

<p>Thwaites Glacier is melting fast. But to understand how climate change is driving its decline, scientists need to send instruments through 2,000 feet of ice into the water below.</p>

Ingenuity’s first black-and-white picture from the air. Image credit: NASA/JPL-Caltech

Victory! Ingenuity conducts its first powered flight on Mars

<p>When a diminutive 4-pound helicopter lifted off over a red landscape on Monday morning, it became the first craft to achieve controlled, powered flight on a planet beyond Earth.</p><p>At approximately 6:15 a.m. EDT on Monday, NASA’s Ingenuity Mars helicopter team—along with eager viewers from across the globe—watched live as data from the red planet arrived to Mission Control via a <a href="https://www.nasa.gov/directorates/heo/scan/services/networks/deep_space_network/about/">Deep Space Network antenna</a>. The data signified that Ingenuity’s flight, which occurred approximately four hours earlier, had been a success.</p><p>“Sometimes we have to do something just to show that we can do it,” NASA’s Associate Administrator for Science Thomas Zurbuchen said during <a href="https://www.youtube.com/watch?v=p1KolyCqICI">NASA’s livestream</a> of the event. “When the Wright brothers flew for the first time, they flew an experimental aircraft. And in the same way, the Mars helicopter is designed to show that we can fly a powered helicopter flight in the Martian atmosphere.”</p>
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<p><a href="https://www.pbs.org/wgbh/nova/article/nasa-ingenuity-mars-helicopter-first-flight/">Getting Ingenuity to fly</a>, Ingenuity Project Manager MiMi Aung added, “was the unwavering dream of our team since day one.”</p><p>On Monday, downlink lead Michael Starch, clad in an orange Ingenuity team polo, studied his computer screen in the helicopter control room. “This is downlink. Early indications,” he said, looking up from the monitor. “Data products look nominal.”</p><p>Sitting close by was Aung, who visibly grinned under her mask.</p><p>“This is downlink,” Starch repeated. “We’ve pulled in data products from Mars 2020.” He pauses for 39 seconds. The room was silent. “This is downlink,” he said again. “Confirming we received Mars 2020 telemetry. Confirming we received Mars 2020 event. Confirming we received helicopter data products.” Starch nodded his head up and down.</p><p>Silence once again fell over the control room. Aung twiddled her fingers. Some teammates nodded. Others glanced at their laptops and then back at their anxiously-awaiting colleagues.</p><p>“This is downlink,” Starch said. “Confirming we have helicopter data products, helicopter telemetry, helicopter event… battery data has been received.”</p>
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<img alt="NASA JPL's Ingenuity Mars helicopter team" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/25819_4-PIA24585-web.width-990_lltuX2v.jpg"/>
<figcaption><p>Members of NASA’s Ingenuity helicopter team, including MiMi Aung (front), in NASA JPL’s Space Flight Operations Facility prepare to receive the data downlink showing whether the helicopter completed its first flight on April 19, 2021. Image Credit: NASA/JPL-Caltech</p>
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<p>Starch handed it off to Flight Control, which gave its announcement: “Ingenuity is reporting having performed spin-up, takeoff, climb, hover, descent, landing, touchdown and spin-down.”</p><p>Aung gave two thumbs up and then waved her fists. The control room erupted with clapping, originating from both mask-wearing team members in person and those watching over Zoom.</p><p>“Altimeter data confirmed,” Flight Control said. Cheers exploded from the control room. The altimeter plot of the flight, mechanical engineer Taryn Bailey explained during NASA’s livestream, indicates a peak. It starts off with a flat line, showing that Ingenuity is grounded, has a steep incline, indicating that the helicopter has spun up and risen, a dwell, showing that Ingenuity is hovering, and then another steep decline to the ground representing Ingenuity’s touchdown.</p><p>“Confirmed that Ingenuity has performed its first flight of a powered aircraft on another planet,” Flight Control said.</p>
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<p>As the cheers and fist pumps continued, the team received its first picture from the mission: a black and white photo that Ingenuity snapped while hovering over the Martian surface, its shadow—four rotors, four legs, and a tissue box-like body—cast beneath it.</p><p>Getting Ingenuity to fly on Mars was no easy feat. This first flight, initially scheduled for Sunday, Apr. 11, was delayed after team engineers identified a potential problem. (The team decided to update Ingenuity’s flight control software before attempting a maiden flight.) And years of preparation back on Earth was necessary.</p><p>Starting in 2014, before testing Ingenuity, the team used helicopter models to simulate flight on Mars. These models were the precursors to Ingenuity and “went through extensive environmental and aerodynamic testing,” Bailey said.</p><p>To properly test these models and then Ingenuity beginning in 2019, “We had to simulate a Mars-like atmosphere,” which is 1% the density of Earth’s, Bailey explained. The team did this by using NASA’s Jet Propulsion Laboratory’s 25-foot space simulator thermal vacuum chamber, which allowed the team to control temperature and pressure to simulate Mars’ atmospheric density. The team also used a gravity off-load system to compensate for the difference in gravity between Earth and Mars, Bailey said.</p><p>After these tests “We said, ‘The next time we fly it’ll be on Mars,’” Aung said during a press conference on Apr. 9.</p>
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<img alt="The Ingenuity Mars helicopter, photographed by Perseverance" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/25816_PIA24550-1200.width-990_N22JFql.jpg"/>
<figcaption><p>The first flight of NASA’s Ingenuity Mars Helicopter was captured in this image from Mastcam-Z, a pair of zoomable cameras aboard NASA’s Perseverance Mars rover on April 19, 2021. Image Credit: NASA/JPL-Caltech</p>
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<p>At four pounds, Ingenuity was built to be both light and fast, bolstering its ability to soar in Mars’ incredibly thin atmosphere. Despite its small size, the helicopter’s wingspan is 4 feet tip-to-tip: “super large for something that’s essentially carrying [a vehicle] the size of a tissue box,” Bailey said.</p><p>Each of its four blades is made of a lightweight but strong composite material and weighs less than 2 ounces—the equivalent of four empty soda cans. To generate lift in an incredibly-thin atmosphere with few molecules to push around, Ingenuity’s blades move at an average speed of 2,500 rotations per minute. (Helicopters used on Earth typically operate at 450 to 500 rpm.)</p><p>While Ingenuity’s first flight was modest—a 10-foot hover above the red planet’s surface and a touchdown—its upcoming four flights will increase in technical difficulty. The team hopes to eventually explore parts of Mars’ terrain that it can’t navigate with terrestrial rovers like <a href="https://www.pbs.org/wgbh/nova/article/nasa-perseverance-mars-rover-landing-success/">Perseverance</a>. “The rover has to navigate around a lot of obstacles on the ground that the helicopter can fly around,” Bailey said.</p><p>“We’ve sent five rovers to Mars and now we have an aerial dimension, which...elevates the next stage of space exploration,” she added. Ingenuity and its eventual successors may also allow for more collaboration and eventually open the doorway for human exploration of other worlds, Bailey said.</p><p>Though the Ingenuity team already received still images of the helicopter’s maiden flight from both Ingenuity and Perseverance, it expects to get video footage and more high-resolution images in the next couple of days. You can view these on <a href="https://mars.nasa.gov/mars2020/multimedia/raw-images/">NASA’s website here</a>.</p>
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<p>The 4-pound helicopter just became the first craft to achieve controlled, powered flight on a planet beyond Earth.</p>

An illustration of the DART spacecraft approaching the binary asteroids Didymos and Dimorphos. Image Credit: NASA/Johns Hopkins APL

NASA launches mission to redirect an asteroid—by striking it with a spacecraft

<p>Today at 1:21 a.m. EST, NASA launched its Double Asteroid Redirection Test (DART) spacecraft in the first-ever “full-scale planetary defense test” to deflect an asteroid, the Agency reports. The craft, built and operated by Johns Hopkins Applied Physics Lab in Laurel, Maryland, is designed to autonomously target and intentionally crash into—at 14,400 miles per hour—an asteroid.</p><p>The hope is that by hitting an asteroid destined to collide with Earth, a successor to DART could redirect it away from our planet, preventing impact.</p><p>“Planetary defense is about making sure that a rock from space doesn’t send us back to the Stone Age,” DART Program Scientist Tom Statler said <a href="https://svs.gsfc.nasa.gov/13985">in a NASA interview</a>. “And the key parts of planetary defense are, first of all, finding the asteroids that are potentially hazardous to the Earth. And we understand where about 40% of those asteroids are.”</p>
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<p>One of those space rocks is Bennu. In October 2020, more than 200 million miles from Earth, a NASA spacecraft named OSIRIS-REx <a href="https://www.pbs.org/wgbh/nova/article/osiris-rex-bennu-asteroid-touchdown/">reached out</a> and grabbed a sample from the spinning-top-shaped asteroid, as scientists believe it may contain <a href="https://www.pbs.org/wgbh/nova/video/inside-osiris-rexs-mission-to-tag-asteroid-bennu/">essential ingredients</a> to our solar system’s planetary formation. Bennu, which is slightly wider than the Empire State Building is tall, is slowly—and steadily—getting closer to Earth.</p><p>At a NASA news conference in August, scientists said that there’s a 1-in-1,750 chance that Bennu will collide with Earth between now and the year 2300, a slight increase from scientists’ previous estimate of 1-in-2,700. (Despite the “now” in this prediction, you and your children, and most likely your grandchildren, will be gone before there’s any possibility of this collision happening, Kenneth Chang <a href="https://www.nytimes.com/2021/08/11/science/asteroid-bennu-earth-osiris-rex.html">reports for the New York Times</a>.)</p><p>Bennu isn’t alone. Though the chances of Earth getting hit by an asteroid like the one that <a href="https://www.pbs.org/wgbh/nova/video/fossil-discovery-could-offer-glimpse-into-day-the-dinos-died/">ended the era</a> of dinosaurs 66 million years ago are slim, fragments of asteroids, “from pebble-sized to person-sized,” hit Earth every day, <a href="https://svs.gsfc.nasa.gov/13985">NASA writes in a press release</a>. An asteroid larger than about 10 feet in diameter hits Earth about once every year, and there’s about a 1-in-50,000 chance of an asteroid larger than 3,200 feet across hitting Earth every 100 years, Bruce Betts <a href="https://www.planetary.org/articles/will-an-asteroid-hit-earth">reports for Planetary.org</a>. “This isn’t the sort of thing that we want to address at the last minute,” NASA program scientist Kelly Fast told NOVA in June.</p>
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<img alt="DART's November 2021 launch" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/DART_Launch.width-990_Ml8co1H.jpg"/>
<figcaption><p>Riding atop a SpaceX Falcon 9 rocket, DART took off Wednesday, November 24 from Space Launch Complex 4 East at Vandenberg Space Force Base in California. Image Credit: NASA/Bill Ingalls</p>
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<p>DART is headed to a binary asteroid system that will be within 6.8 million miles from Earth in September 2022. Its target is a 525-foot space rock named Dimorphos, meaning “two forms” in Greek, which orbits the half-mile-wide asteroid Didymos (meaning “twin”), NASA reports.</p><p>Because Didymos and its moon come “pretty close to Earth,” Johns Hopkins Applied Physics Lab Systems Engineer Elena Adams told NOVA in June, it’s technically “considered a potentially hazardous” system. But, like Bennu, its chances of striking our planet are incredibly slim. “There’s nothing that we could do to it that will make it a danger to the Earth,” Statler said. Hitting Didymos’ moon Dimorphos, for example, won’t change the trajectory of Didymos, Adams told NOVA.</p>
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<p>DART will try to push Dimorphos using a technique called kinetic impact deflection: intentionally crashing into the space rock in a bid to move it. Approximately four hours before impact, DART will become fully autonomous, directing itself toward the tiny moon 60,000 miles away. The goal isn’t to simply move Dimorphos. “The important thing isn’t how far we move the asteroid,” Statler said. “It’s how much we change its speed by.” To determine whether the strike was successful at altering Dimorphos’ velocity, scientists will analyze any changes to its orbit with telescopes back on Earth.</p><p>Kinetic impact deflection is one potential method—and the “most technologically mature”—of a few proposed techniques to redirect an object hurtling in space, NASA reports. As NASA scientists continue to investigate asteroid deflection strategies, research teams across the globe aim to discover asteroids that could be potentially hazardous to our planet. Ideally, they’ll identify any space rock “on a collision course with Earth” years in advance, Statler said in a NASA interview, buying time for scientists to redirect its path. The goal is never to destroy an asteroid, Statler said: “We probably wouldn’t be able to do that anyway.”</p><p>The chances of an asteroid large enough to cause damage to Earth, but small enough to avoid detection well in advance of its approach, are slim. But that doesn’t discredit DART’s mission, Statler suggested. “We take precautions about low-probability events all the time,” he said. If researchers do happen to spot a dangerous asteroid years in advance, “then a change to its velocity,” Statler said, “can make the difference between an impact on Earth and a safe miss.”</p>
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<p data-block-key="76aht">As the first-ever “full-scale planetary defense test” to deflect a space rock, the DART mission aims to show that protecting Earth from a hazardous asteroid is possible.</p>

Vaccine and band-aid on a tray in a doctor's office. Image credit: SELF Magazine

A third Covid-19 vaccine is effective and cheap. What happens next?

<p>On Monday, AstraZeneca announced that its coronavirus vaccine is up to 90% effective, according to late-stage trials. It’s also relatively cheap and easy to store, meaning it may become the choice vaccine for developing nations.</p><p>Though the vaccine’s efficacy was 90% in one of the dosing regimens its team tested, its average effectiveness was 70%. A vaccine’s efficacy is measured as the percent reduction in disease incidence among a vaccinated group of people compared to an unvaccinated or placebo group, according to the Canadian Center of Vaccinology. (The average <a href="https://www.pbs.org/wgbh/nova/video/does-the-flu-shot-work/">flu vaccine</a> is about 31-44% effective, <a href="https://www.cdc.gov/flu/vaccines-work/2019-2020.html#anchor_1573061303373">the CDC reports</a>.)</p><p>The team administered different vaccine regimens to different groups: One received two full doses, whereas another received a half dose followed by a full dose. The team expected that two high doses would set off the strongest immune response, Andrew Pollard, director of the Oxford University Vaccine Group and chief investigator for the trial, explained at a news conference. But the opposite occurred.</p>
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<p>For the subgroup that received two full doses of the AstraZeneca vaccine a month apart, it was only 62% effective. But in the group that was given half a dose followed by a full dose one month later, the vaccine was 90% effective.</p><p>Oxford scientists, who helped develop the new vaccine, are positing that a half dose followed by a full dose may prime the body to create a greater immune response to SARS-CoV-2, the virus that causes COVID-19. But they’re unsure why. The 90% efficacy rate, while comparable to 95% effectiveness reported last week by both <a href="https://www.pbs.org/wgbh/nova/article/pfizer-moderna-covid-vaccines-clinical-trials/">Moderna and Pfizer</a>, was recorded in a group of fewer than 3,000 people. Conversely, Moderna’s trial has involved 30,000 people, half of whom received its vaccine and half a placebo. Pfizer’s trial has enrolled more than 43,000 volunteers, 38,955 of whom have completed its vaccine regimen as of November 16 (with half receiving a vaccine and half a placebo).</p><p>AstraZeneca’s results reported Monday come from trials involving a total of 23,000 people in the U.K. and Brazil, 11,636 of whom were given the vaccine with the remaining receiving a placebo. Researchers said 131 Covid-19 cases were detected during the clinical trials and none of the study participants that fell ill required hospitalization. AstraZeneca has yet to release information on how many of these participants received the vaccine and how many received the placebo.</p><p>Unlike <a href="https://www.pbs.org/wgbh/nova/article/pfizer-moderna-covid-vaccines-clinical-trials/">Pfizer and Moderna’s mRNA vaccines</a>, which use synthetic genetic material to help the body produce one small component of the virus itself that the immune system can learn from—in this case, SARS-CoV-2’s iconic spike protein—the AstraZeneca vaccine uses a weakened version of a common cold virus that’s combined with genetic material for the spike protein, Danica Kirka <a href="https://apnews.com/article/astrazeneca-vaccine-third-cheaper-oxford-c99d26eb2946f6fde45a1edc002ff028">writes for the Associated Press</a>. “After vaccination, the spike protein primes the immune system to attack the virus if it later infects the body.”</p><p></p><p><b><i>Watch to learn more about mRNA vaccine technology:</i></b></p>
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<p>And while Moderna and Pfizer and BioNTech’s vaccines need to be stored at freezing temperatures, this new vaccine remains viable at 36 to 46 F. (Storing vaccines at their required temperature is one of the greatest challenges that developing countries face with routine immunization.)</p><p>“I think these are really exciting results,” Pollard said. “Because the vaccine can be stored at fridge temperatures, it can be distributed around the world using the normal immunization distribution system.”</p><p>It’s also cheaper. Pfizer and BioNTech, as part of their $1.95 billion contract with the federal government under <a href="https://www.hhs.gov/coronavirus/explaining-operation-warp-speed/index.html">Operation Warp Speed</a>, “have set the initial price at $19.50 a dose, which comes to $39 per patient (since each vaccine requires a two-dose regimen),” Katie Jennings <a href="https://www.forbes.com/sites/katiejennings/2020/11/17/how-much-will-a-covid-19-vaccine-cost/?sh=7c14e82f576d">writes for Forbes</a>. Moderna, which received nearly $1 billion from the Biomedical Advanced Research and Development Authority and has a $1.5 billion contract for 100 million doses, says its vaccine will cost approximately $25 a dose or $50 a patient, since it too requires a second dose.</p><p>Conversely, AstraZeneca’s vaccine will cost about $2.50 a dose.</p><p>AstraZeneca has pledged to not make a profit on the vaccine during the pandemic and having reached agreements with governments and health organizations, Kirka reports.</p><p>It plans to have more than 300 million full doses of its vaccine available globally by the end of March 2021. That number could increase by 50%, given the promising results of first administering a half dose to patients, followed by a full dose one month later. The company hopes to produce around 200 million doses a month, AstraZeneca’s Executive Vice President Pam Cheng said during a press event.</p>
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<p>The Pfizer, Moderna, and AstraZeneca vaccines will all need to be approved by regulators before they can be widely distributed. “AstraZeneca said it will immediately apply for early approval of the vaccine where possible, and it will seek an emergency use listing from the World Health Organization, so it can make the vaccine available in low-income countries,” Kirka writes.</p><p>Pfizer and Moderna plan to apply for FDA emergency use authorization this month. Moderna stated on November 16 that it expects to be able to ship about 20 million vaccine doses in the U.S. by the end of this year and another 500 million to 1 billion in 2021, if authorized to do so. Pfizer expects to produce up to 50 million vaccine doses in 2020, and 1.3 billion in 2021, if authorized.</p><p>These COVID-19 vaccine rollout plans raise the question: Who should—and ultimately will—get vaccinated the soonest?</p><p>Vaccine supplies will be limited at first, meaning the decisions about who gets those first doses could save tens of thousands of lives, Jill Neimark <a href="https://undark.org/2020/11/18/best-strategy-to-deploy-covid-19-vaccine/">writes for Undark Magazine</a>. “The consensus among most [disease] modelers is that if the main goal is to slash mortality rates, officials must prioritize vaccinating those who are older, and if they want to slow transmission, they must target younger adults,” she writes.</p><p>Many experts agree that the threat of superspreaders must not be ignored. “This is a pandemic defined by clusters,” Christopher Cox <a href="https://www.wired.com/story/covid-19-vaccine-super-spreaders/">writes for WIRED</a>. “Some cause deadly outbreaks in nursing homes, prisons, and meatpacking plants. Others overwhelm families and friend groups. Although the numbers vary from study to study, SARS-CoV-2 seems to follow the 80/20 rule: 80 percent of cases stem from just 20 percent of infected individuals.” Some network theorists believe that social butterflies, who are the most likely to become superspreaders, should be vaccinated first.</p><p>For now, it seems, the first doses of a COVID-19 vaccine will go to health care providers here in the U.S. and in the World Health Organization’s member countries, per its recommendation. But the CDC committee is grappling with a fundamental question, Cox writes: Do doctors first immunize the most vulnerable, and therefore protect individuals, or do they immunize the most social, and therefore reduce transmission and protect the population?</p><p>And then, of course, are the issues of trust and inequity, Neimark writes: “For instance, it’s widely acknowledged that Black people have experienced hospitalization and death at disproportionately high rates compared to White people.” And because of algorithmic bias, a recent study found, White patients are often <a href="https://www.pbs.org/wgbh/nova/article/racial-bias-medical-algorithm-black-patients/">prioritized over Black patients</a> in hospitals, even when Black patients are sicker than their White counterparts. “When ethicists begin to talk about prioritizing Black people for vaccines, it can be perceived as an intent to experiment on them by pushing them to the head of the line,” Neimark writes.</p><p>One thing is sure: Multiple vaccines will be necessary to help bring an end to the pandemic, which has to date sickened more than 12.5 million Americans and nearly 60 million people worldwide. And if there’s any silver lining to the surge of cases in the U.S. and worldwide, Rebecca Robbins <a href="https://www.nytimes.com/2020/11/18/business/covid-pandemic-speeding-vaccines.html?action=click&amp;module=RelatedLinks&amp;pgtype=Article">reports for the New York Times</a>, it’s that the uptick could make results from other closely watched vaccine trials available sooner and with greater statistical power, while also speeding up trials of COVID-19 treatments.</p>
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<p>The Pfizer, Moderna, and AstraZeneca vaccines are at least 90% effective, according to clinical trials. Here’s who may get vaccinated first.</p>

Human fossil footprints at White Sands National Park in New Mexico. Image Credit: Courtesy of the National Park Service

Human tracks may be earliest evidence of people in North America

<p>In southern New Mexico lies the Tularosa Basin, an oblong bowl that’s home to a natural sandbox: White Sands National Park.</p><p>In 2005, David Bustos came to White Sands to work as a National Park Service biologist. The following year, he took notice of odd animal footprints that would appear only when the ground was wet. (The first of these footprints was reported in the 1930s.) The markings, which would disappear as the earth dried up, became known as ghost tracks.</p><p>Then in 2009, Bustos came across tracks he thought belonged to ancient humans walking alongside mammoths. But few scientists agreed, he says, rebutting with “No, no, those are the prints of camels that were slipping in the mud,” referring to now-extinct North American camels. And the tracks would disappear with changes in the weather. Heavy rainfall drowned them; periods of drought dried them up. It would take more than a decade—and cooperative weather—for scientists to agree that the tracks belonged to humans. </p><p>Then, says U.S. Geological Survey (USGS) Research Geologist Kathleen Springer, “What everyone was asking is, ‘How old are these things, really?’”</p>
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<p>In September 2021, Bustos, Springer, and a group of other researchers published their findings in the journal Science: The team identified 61 human tracks within multiple levels of earth belowground, and between layers of these tracks were seeds from an ancient aquatic plant. Analyses of these seeds—and the footprints they were embedded within—are now challenging scientists’ understanding of when and how people arrived in the Americas.</p><p>Archaeologist Joe Watkins, who was not involved in the study, believes the findings have potentially massive implications. “I think, outside the next big migration of going to the Moon or Mars, the migration to the Americas was the last great migration humanity had,” he says. Upending the timeline of this journey could have implications for both science and Native American cultures, Watkins, who is a member of the Choctaw Nation of Oklahoma, believes.</p><h3>Visiting the tracks</h3><p>At first light on a cold January morning in 2020, Bustos set out with Springer and her USGS colleague Jeff Pigati on all-terrain vehicles to visit White Sands’ ancient tracks. The team wore parkas to keep warm amid a prevailing wind. Springer recalls the hour-and-a-half journey through the dunes being like a “Disney ride.” It was the “funnest thing in the world,” she says. “Just being out there is surreal.”</p><p>Eventually, after passing through a large swath of national park that borders the site of the first atomic bomb test, Springer, Pigati, and Bustos fell upon thousands of tracks. They belonged to packs of dire wolves, giant sloths, 13-foot-tall mammoths, and other animals. And, Springer says, “there’s a person track right smack dab in the middle of them.”</p>
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<img alt="White Sands National Park dunes" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/White_Sands_Dunes.width-990_kjxnoic.jpg"/>
<figcaption><p>Gypsum sand dunes at White Sands National Park, New Mexico. Image Credit: NOVA/GBH</p>
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<p>“When Dave showed us these things and we had our eyes trained on them, we were almost afraid to step down,” Pigati says. “It looks like a painting in some places.”</p><p>Bustos recalls the conditions that day being perfect for identifying tracks. The trio saw human footprints going underneath the sediment in places, illustrating that there was more than a surface layer of them. “We were seeing seed layers popping out all over the place,” Bustos says. To determine how old the footprints were, Springer and Pigati’s team would collect these ancient seeds from different layers of footprints. The overwhelming evidence of ancient plant life excited Bustos.</p><p>About 36,000 to 19,000 years ago, lakes filled the Tularosa Basin. The largest of these was Lake Otero, which fluctuated in size and activity based on rainfall. Plants like spiral ditchgrass (<i>Ruppia cirrhosa</i>), whose seeds are now embedded in layers of earth, grew along Otero’s edges. About 23,000 years ago, the southwestern U.S. became drier and the lake shrank. This exposed a large area of land that was once underwater, whose clays and silts became overtopped by gypsum sand and silt. People began walking around these surfaces, which “were kind of squishy in some areas,” Springer explains. And the people weren’t alone: The impressions from mammoths, ground sloths, and camels, sit alongside—and sometimes right on top of—human prints. </p><p>“This can only happen if they are in the area at the same time,” Pigati said in an email. “Exactly how they may have interacted in the vicinity of our [research site] is unknown, but there is definitive evidence that humans were harassing or stalking a giant ground sloth on the west side of the basin.”</p><p>In many other cases, interactions between humans and animals seem peaceful. “What’s interesting to me,” Bustos says, “is it’s not just a mammoth and a hunter. It’s families. You see a baby mammoth turning around and spinning. We have the juvenile and adult megafauna prints with the babies and adult [humans].”</p>
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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Sloth_Footprint.width-990_j4t67Wp.jpg"/>
<figcaption><p>A footprint from a Harlan's ground sloth at White Sands National Park. Image Credit: Courtesy of the National Parks Service</p>
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<p>Having about 10 hours of daylight, the team got to work “trenching” the human footprints, Springer says. With ground-penetrating radar, they were able to determine that footprints were present within layers of sediment. They then dug a trench to view the layers in cross-section. If Springer and Pigati’s cross-section was a sandwich, the footprints would be the filling and the dateable material around the footprints would be the bread. </p><p>Dating tracks only at the surface would yield inaccurate results, Pigati explains. “You can look in every direction and there are trackways everywhere in every horizon,” he says. But if you calculate the age of these footprints on the surface layer of earth only, you’ll just find that they’re younger than the ground they’re upon, he says. By looking at layers of sediment below the surface, the team set out to document how many layers contained footprints and find datable material above and below each layer. Each of these layers would contain footprints from a unique time period, the team posited. “The footprints are imprinted at the top of a given layer of sediment—they don’t really pass through the layers,” Pigati wrote in an email.</p><p>As the sun rose higher in the sky, the white sand reflected a near-blinding light, and the day quickly grew warm. The researchers shedded their parkas and worked in t-shirts until the January sun fizzled and it was time to ride back through the dunes, chunks of sediment layers in hand.</p><p>The team later extracted 40 to 60 ditchgrass seeds from every level of footprints in every sample. In a USGS lab in Golden, Colorado, they cleaned each set of seeds with a chemical treatment and began combusting them.  </p><p>The combustion process, automated by a machine in the lab, didn’t obliterate the seeds but turned them into a gas. From this gas, a machine turned the once-seeds back into solids: graphite pellets about the size of a pencil tip. This technology of making “graphite targets” dates back to the 80s, Pigati says. “Every lab does it the same way in the world.”</p><p>The team then took these pellets, tapped them down into cartridges, and sent them off to a lab to measure the amount of a radioactive isotope of carbon, called carbon-14, they contained. Then they waited for results.</p><h3>What the tracks mean</h3><p>Months later, they came. The seeds revealed that the footprints they were embedded within are between 21,000 and 23,000 years old—thousands of years older than what scientists generally consider to be the earliest evidence of people in the Americas.</p><p>“For forever, people thought Clovis were the first people to cross over [the Bering Strait] about 13,000 years ago,” Pigati says, referring to the commonly-held view among archaeologists. As the story goes, ice sheets in what is now Canada blocked passage between what is now Alaska and the rest of the Americas. Once these ice sheets began retreating, people came south through an ice-free corridor, Pigati explains. His team’s findings now challenge this belief. Carbon dating of the seeds within the White Sands footprints suggest that people were in the Americas while ice sheets still covered much of northern North America. “A lot earlier” than previously thought, Pigati says. </p><p>“When we got the final dates back, it was very…” Springer pauses over Zoom, choosing her words carefully. “The arrows were going to start flying. We knew we needed an [evidence-supported] explanation why these findings were really robust.”</p>
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<p>Archaeologist Joe Watkins says that if the dating of the seeds, and therefore footprints, is correct, “it puts us at 20% older than the dates we have from the rest of America.” Therefore, ages of other important archaeological sites like Meadowcroft Rockshelter in Pennsylvania, where scientists have found 16,000-year-old evidence of human life, may need to be reconsidered. (In 2014, Nikhil Swaminathan <a href="https://www.archaeology.org/issues/145-1409/features/2369-peopling-the-americas-meadowcroft-rockshelter">wrote for Archaeology Magazine</a> that Meadowcroft Rockshelter is “the longest-occupied site in the Americas.”)</p><p>Watkins first heard about the White Sands tracks years ago while working in Washington D.C. as the chief of the Tribal Relations and American Cultures Program of the National Park Service. But he didn’t see them until after he’d retired, visiting White Sands during a NOVA shoot for the film “<a href="https://www.pbs.org/wgbh/nova/video/ice-age-footprints/">Ice Age Footprints</a>.” Seeing human footprints intermingling with those of ground sloths was overwhelming and “tremendously exhilarating,” he says.</p>
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<img alt="Archaeologist Joe Watkins holds a clovis point" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Joe_Watkins.width-990_4i0j7w4.jpg"/>
<figcaption><p>Watkins pictured with a replica Clovis point. His interest in archaeology was piqued at 10 years old when he found an archaic point on his family’s Oklahoma homestead. Watkins, who’s now 71, showed the point to his grandmother. The artifact didn’t come from modern Choctaw, but was much older, she explained in her native language. From that moment, Watkins became “more interested in looking into the unwritten past,” and, with his grandmother’s support, began pursuing a career in archaeology, a field he recognizes isn’t always “in advantage to the Native American community,” he says. Image Credit: NOVA/GBH</p>
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<p>But Watkins cautions that, with no other aspects of culture present but footprints, scientists like him can only speculate how ancient humans were using the land. “Were they just walking? Were they hunting? Did they have a camp nearby?” he asks. Archaeology may not hold all the answers to these questions: “I do think it’s important for American Indians to be involved so they can offer their insights so we can better understand who these people were,” Watkins says, reflecting on his own Choctaw roots.</p><p>As Native American identity is tied to the land, Watkins believes, “the Native peoples will say we’ve always been here,” he says. “I usually say [the first Americans] weren’t Native Americans. They weren’t Siberians. They were whatever they called themselves.” Combining this philosophy with science is a way to integrate belief systems, he says.</p>
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<p>The White Sands findings, Watkins says, “forced us to reconsider the most cherished ideas of the people of North America.”</p>
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<p>Watkins recites his people’s story about two stiff-legged bears that meet in a black-loam prairie and have a battle. Only one survives; it becomes the last of its species. “Some Choctaw interpret ‘stiff-legged bear’ as being a mammoth,” Watkins says. If humans did once walk alongside mammoths in New Mexico’s Tularosa Basin 20,000 years ago, he adds, there’s a chance these people gave birth “to any number of tribal people across the U.S.” </p><h3>Racing against time</h3><p>Bustos, Springer, Pigati, and fellow researchers visited the ghost tracks again in January and April 2022. They extended their trench, identifying more footprints from potentially before and after the original set they excavated. To bolster their findings, Bustos explains, the team won’t rely solely on dating seeds. They’ll date pollen, too. “This work is not done,” Pigati says. “We have a window from 21,000 to 23,000 [years]. We don’t know if people were here before then.” </p><p>But the clock is ticking. Erosion in White Sands is exposing and destroying the tracks, Springer says. Though the Tularosa Basin has been eroding for nearly 12,000 years, climate change is likely exacerbating erosion today, she explains. “The layers, they’re finite,” Bustos adds. “We’re losing thousands of tracks to erosion. It’s a race to document them before they’re gone.”</p><p>Already, some tracks reveal clues about ancient daily life in the Tularosa Basin.</p><p>“There’s something about the children,” Bustos says. “You see these toddlers running and jumping, and the story really comes alive.” Watkins agrees. “When we look at the tracks of children playing in perhaps puddled water surrounded by ground sloths,” he says, “it takes us back to childhood memories of children playing in puddles all around the world.”</p>
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<p data-block-key="arqov">Footprints in New Mexico’s White Sands National Park challenge scientists’ timeline of when humans first came to North America.</p>

Sukee Bennett

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