A dried, twisted old tree against a blue sky

"Methuselah," a bristlecone pine in California long considered to be the world's oldest tree. Image Credit: Yen Chao, Flickr

<p>Will a Patagonian cypress in Chile prove older than California’s most elderly bristlecone pine?</p>

The world’s oldest tree has competition

Perfectly round ball of brown ice cream on a spoon against white background

<p>Sixty years ago a teenager’s homemade ice cream raised a surprisingly complicated question: Can hot liquids freeze faster than cold ones?</p>

The ice cream that changed physics

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

<p>Footprints in New Mexico’s White Sands National Park challenge scientists’ timeline of when humans first came to North America.</p>

Human tracks may be earliest evidence of people in North America

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<p>NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology. Launched in 2012, we feature in-depth articles and commentaries from some of the most respected journalists, scientists, and engineers. NOVA Next explores the ideas that are changing the future, from the frontiers of synthetic biology to the politics of personalized medicine.</p><p>Let us know what you think. We’re listening on <a href="http://www.facebook.com/NOVAonline">Facebook</a>, <a href="http://twitter.com/novapbs">Twitter</a>, and email.</p><p>If you’re a journalist and have an idea for a story, send it our way.</p>

NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology.

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<p>NOVA Next is NOVA’s award-winning digital publication that provides answers from the cutting edge of science and technology.</p>

Silhouette of a spacecraft with panels extended against giant white moon, with Earth off in the distant night sky

An artist rendering of NASA's Orion spacecraft doing a lunar flyby during the Artemis 1 mission. Image credit: NASA/Liam Yanulis, Flickr

5 reasons why humans are going back to the Moon

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<p>Fifty years after the last <a href="/wgbh/nova/video/how-nasas-apollo-8-left-earths-orbit/">Apollo mission</a>, NASA is embarking on a new age of lunar exploration. With the <a href="https://www.pbs.org/wgbh/nova/article/artemis-launch-nasa-sls-orion-moon/">launch of Artemis 1</a>, the agency has begun testing technologies designed for this era, including the massive SLS moon rocket and the Orion spacecraft, which will carry crews on future missions. But why go back at all? NOVA’s “<a href="https://www.pbs.org/wgbh/nova/video/back-to-the-moon/">Back to the Moon</a>” explores five reasons scientists and entrepreneurs alike have their sights set on the Moon once again:</p><h3><b>To study its water </b></h3><p>Water is essential for life on Earth and a critical ingredient for outer space exploration. The Moon would be an ideal space pitstop to gather this resource, but for a long time it was unclear whether it had water at all. After researchers analyzed lunar samples from the Apollo mission, they concluded that the Earth and the Moon are formed from the same materials. This hypothesis raised an intriguing possibility: Might the Moon also have once been wet?</p>
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<h3><b>The Moon is a record of solar system history (5:20 - 7:45)</b></h3><p>The Moon preserves a complete geologic record that dates back nearly to the formation of the solar system. NASA’s moon-mapping spacecraft, the Lunar Reconnaissance Orbiter, has been orbiting the Moon since 2009. It was designed to gather new insight into the Moon’s geological record and scout the surface for future human exploration. </p>
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<h3><b>To harness resources to build lunar bases (7:45 - 11:23)</b></h3><p>After scientists uncovered the Moon’s mineral wealth, some suggested it could be harnessed to build bases on the Moon. Hauling materials from Earth to build on the Moon could cost billions of dollars. But if the raw materials are already available in space, then all kinds of construction activities become conceivable.</p>
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<h3><b>Lunar ice could be a fuel source (29:03 - 32:15)</b></h3><p>Water is made up of hydrogen and oxygen, and if those two atoms can be separated and stored, they can fuel a rocket. That’s because hydrogen and oxygen are highly flammable, and when they are burned together, they release a huge amount of energy–enough to propel a rocket. That means that, at least in theory, lunar ice could provide water to drink, air to breathe, and a source of propellant for spaceships to fuel up and head out.</p>
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<h3><b>Lava tubes could be lunar shelter (46:12 - 49:03)</b></h3><p>To live on the Moon, humans will need to shield themselves from radiation coming from the Sun and deep space. One way to do this might be to live <i>in</i> the Moon, inside lava tubes that formed billions of years ago. Scientists have yet to discover what’s inside them, but similar tubes on Earth might offer clues. </p>
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<p data-block-key="r5y64">Earth’s natural satellite could be a jumping-off point for future space exploration.</p>

A bright orange vertical flame and billows of steam against a black night sky

The Artemis I flight test mission begins as NASA’s Space Launch System rocket, carrying the Orion spacecraft, launches from Florida's Kennedy Space Center. Image Credit: NASA/Keegan Barber

NASA’s Artemis I moon rocket finally launches

<p>After months of delays, fuel leaks, and hurricanes, NASA launched the world’s most powerful rocket from Kennedy Space Center just before 2 a.m. This uncrewed mission, dubbed Artemis I, is designed to test the massive rocket and technologies aboard the new Orion spacecraft.</p>
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<p>“We rise together, back to the Moon and beyond,” said NASA launch commentator Derrol Nail as the rocket lifted off.</p><p>Minutes after launch, the rocket boosters and <a href="/wgbh/nova/video/how-do-you-get-a-rocket-to-land-back-on-earth/">core stage fell away</a>, and Orion continued on what will be a 25-day mission around the Moon and back. The spacecraft will travel roughly 1.3 million miles, at one point coming within 62 miles of the lunar surface, and splash down in the Pacific Ocean on December 11. </p><p>Artemis I is the first mission in the Artemis program, which aims to put <a href="/wgbh/nova/video/back-to-the-moon/">a crew on the Moon</a>, including the first woman and person of color, and pave the way for eventual <a href="/wgbh/nova/video/the-planets-mars/">exploration of Mars</a>.</p><p>To launch the Orion spacecraft, including a crew and payload in a single trip to the Moon, NASA and its collaborators designed the Space Launch System rocket. This SLS core stage alone stands 212 feet tall. In this first configuration, the rocket can produce 8.8 million pounds of thrust.</p><p>The mission will also test Orion’s large heat shield. NASA estimates that upon reentry the spacecraft will experience temperatures as high as 5,000 F, half as hot as the surface of the Sun.</p>
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<p>"The heat shield actually has to withstand the fastest and hottest reentry we’ve ever seen in human spaceflight,” NASA astronaut Kayla Barron said in a pre-launch broadcast.</p><p>When Orion splashes down, the heat shield tiles will absorb seawater, and engineers will need to change them out for the next mission. </p><p>Orion is also equipped to test radiation exposure, one of the hazards Artemis crews will face on future missions. Orion’s sensors will measure radiation as the craft transits to and from the Moon. The spacecraft is carrying mannequins dressed in radiation protection vests, and upon its return, scientists will measure the vests’ radiation damage to better understand what Artemis crews will need to endure. </p><p>The next mission is Artemis II, which currently aims to send four astronauts to the Moon in 2024, more than 50 years after the <a href="/wgbh/nova/video/apollos-daring-mission/">Apollo program</a> ended.</p><p>“Artemis is different than Apollo because we are returning to the Moon, but this time we are going to stay,” Barron said.</p>
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<p data-block-key="fzq82">NASA’s massive SLS rocket and Orion spacecraft kick off a series of missions to put humans back on the Moon.</p>

Aerial view of a stylized condor carved into a brown desert

A condor geoglyph in Nazca, Peru. Image Credit: Roger Canals, Wikimedia Commons

PHOTOS: Huge, ancient animals carved into Peru’s hills

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<p>Spread out over 200 square miles of the Peruvian desert lies a treasure of the ancient world: thousands of enormous “geoglyphs,” huge shapes made from rocks and earth. Most of these are lines—some continuing for miles—while others are geometric shapes and recognizable figures: a spider, a hummingbird, a cactus, a llama, a flower. Known as the Nazca lines, the geoglyphs have survived for many centuries thanks to the dry climate of Peru’s southern coast—long outlasting the civilization that made them.</p><p>The Nazca lines were rediscovered in the 1920s, as plane travel afforded a new perspective of the Peruvian desert. Today, new technologies, like AI and drones, help archaeologists uncover more geoglyphs and piece together clues about the people who built them. Feast your eyes on a few of the most striking of these wonders:</p>
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<img alt="Aerial view of a monkey carved into the beige desert landscape" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Nazca_monkey.width-990.jpg"/>
<figcaption><p>A monkey geoglyph in Nazca, Peru. Image Credit: PsamatheM, Wikimedia Commons</p>
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<p>The Nazca (Nasca) were fishermen and farmers who lived in oases along the arid southern coast of Peru between 100 BCE and 800 CE. The images and lines they carved into their desert home, like this monkey, are truly huge in scale. A <a href="https://www.pbs.org/wgbh/nova/article/birds-nazca-lines/">Nazca hummingbird</a> is some 300 feet long, while a condor measures about 450 feet. Archaeologists have long theorized that the Nazca created the geoglyphs as a way to pray to their gods for water and fertility in a forbidding climate. The glyphs’ intended audience couldn’t have been humans, the logic went, because the huge images could only be viewed in full from the sky.</p>
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<img alt="Aerial photo of a whale etched into flat, brown desert" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Nazca_whale.width-990.jpg"/>
<figcaption><p>A whale geoglyph in Nazca, Peru. Image courtesy of GBH/NOVA</p>
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<p>After the lines were rediscovered, studies focused on the giant images spread across the flatter plateaus. But more recently, archaeologists have identified a whole new type of glyph: one that’s not lying flat but instead sits slanted on the hillsides. These geoglyphs were partially covered over (and therefore harder to find) because their location makes them more vulnerable to erosion from wind and water.</p>
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<img alt="Aerial view of two human figures and two animals carved into a brown hillside" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/shepherd_geoglyph.width-990.png"/>
<figcaption><p>Geoglyphs on a hillside in southern Peru. Image courtesy of GBH/NOVA</p>
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<p>It’s not only their position on hillsides that makes this newly rediscovered type of geoglyph unusual. These images are also drawn in a different style than the monkey and whale above. Were they drawn by the same people? </p>
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<p>To answer that question, archaeologists have compared the style of imagery in the hillside drawings to textiles and ceramics from cultures that have historically lived in the area. They found similar elements in the work of the nearby Paracas culture, which means “sand falling like rain.” Like the hillside geoglyphs, Paracas textiles “show birds, cats and people that are easily comparable,” archaeologist Johnny Isla <a href="https://www.bbc.com/news/world-latin-america-54593295">told EFE News Agency</a>. The Paracas preceded the Nazca by several centuries, meaning these glyphs must be older than their larger, flatter counterparts.</p>
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<img alt="Aerial view of a cat carved into a brown hillside" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Nazca_pampa_cat.width-990.jpg"/>
<figcaption><p>A geoglyph of a pampas cat was identified on a hillside in Peru in 2020. Image courtesy of GBH/NOVA</p>
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<p>This geoglyph shows a <a href="https://www.theguardian.com/world/2020/oct/18/huge-cat-found-etched-desert-nazca-lines-peru">pampas cat</a>, a now endangered species that was more common in the time of the Paracas and Nazca. Isla believes it was drawn on this hillside during the late Paracas era, between 500 BCE and 200 CE. Finding geoglyphs drawn by the Paracas is a big deal because it has given archaeologists insight into where the Nazca, and their geoglyph tradition, came from. Isla and other archaeologists have been able to link the two cultures together using DNA and traditional arts like weaving and ceramics uncovered from Paracas temple complexes and around Nazca geoglyphs. That data suggests that the Paracas actually <i>became</i> the Nazca, sometime around the year 100 CE. </p>
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<img alt="Aerial view of two block-like human figures carved into brown hillside, among other hills an valleys" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Paracas_people_geoglyph.width-990.png"/>
<figcaption><p>Geoglyphs on a hillside in southern Peru. Image courtesy of GBH/NOVA</p>
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<p>In recent years, Isla and other archaeologists have <a href="https://www.livescience.com/62238-new-nazca-lines-discovered.html">used drones</a> to find 50 new Paracas hillside geoglyphs in Palpa, which neighbors Nazca. Before the age of drones, archaeologists relied on planes (which flew too high to see small or eroded earthworks) or even just standing on ladders. Being able to use drones has “totally changed the research” Isla told NOVA, since they can fly at low altitude and provide many new angles of perspective. </p>
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<img alt="An aerial shot of a bird and other small animals carved into a brown hillside" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/Nazca_owl_H43qAcv.width-990.png"/>
<figcaption><p>Animal geoglyphs on hillsides in southern Peru. Image courtesy of GBH/NOVA</p>
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<p>Isla and another Peruvian archaeologist, Luis Jaime Castillo, believe the hillside drawings show that the Paracas used geoglyphs for an entirely different purpose than their Nazca descendants later would. “Placing these geoglyphs on the slopes means that, in contrast with the Nazca Lines, you can see them if you are standing in the valley below where life and agriculture is taking place,” Castillo <a href="https://www.theguardian.com/science/2020/may/24/nazca-lines-drones-new-discoveries-peru">told The Guardian</a>. “If the Nazca Lines were made by humans for the gods, these figures were made by humans for humans.” Similarly, Isla believes the Paracas used their geoglyphs to mark territory or waypoints through the desert—the road signs of ancient Peru.</p><h4>Nazca Desert Mystery:</h4>
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<p data-block-key="20ntp">These are just a few of the geoglyphs in southern Peru, known as the Nazca lines, thought to be at least 2,000 years old.</p>

Side view of a lion fish against a black background, it's long spines splayed out

Two species of invasive lionfish have been spreading rapidly throughout the Caribbean, and along the Atlantic coasts of North and South America for nearly 40 years. Image Credit: Alt Eduard, Shutterstock

What to do with an invasive fish? Make leather

<p>It seems like an ordinary leather wallet, neatly stitched, with a slight sheen. “It looks like leather, smells like leather,” says Aarav Chavda, CEO and co-founder of Inversa Leathers. Twist or fold it, and you might notice it’s “wickedly” strong, thanks to a unique fiber structure. Look closer, and you might see the delicate lattice of ridgelines that once held scales in place. But it’s not made from lizard skin. And it’s certainly not cow hide. It’s lionfish.</p>
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<p>“We create leather from this horrible invasive species,” Chavda says. Inversa’s work is one attempt to solve an ecological crisis, albeit in an unexpected way. Or, as Chavda puts it, “Wait what, how does a handbag save the coral reefs?”</p><p>Lionfish look unlike anything else on the reef, with striking red-brown zebra stripes and huge venomous spines that fan out around them. Native to the Indo-Pacific region and the Red Sea, they’ve long been popular in home aquariums. But in the 1980s, a few individuals either escaped or were released off the coast of Florida. </p><p>Away from the creatures that normally control their populations, these invasive lionfish have become voracious top predators: <a href="https://manoa.hawaii.edu/biology/sites/manoa.hawaii.edu.biology/files/users/hixonm/albins_hixon_13_ebf.pdf">One study</a> found that lionfish can kill 79% of juvenile fish on a reef in just five weeks. And since many of those fish eat algae off corals, their disappearance can set off a domino effect that kills the reefs, as well. Over the past few decades, the swiftly reproducing lionfish have spread up and down the Atlantic coast and <a href="/wgbh/nova/article/blackinnature-tropical-paleontology/">throughout the Caribbean</a> with shocking speed. Now, having been introduced via the Suez Canal, they’re even taking over the Mediterranean. </p><h4>Watch: Ocean Invaders</h4>
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<p>Fishing may seem like an obvious solution, but traps and lines don’t fool lionfish. The best way to remove them from an area <a href="https://www.pbs.org/wgbh/nova/article/force-blue/">is by spearfishing</a>. So to stop this underwater disaster, coastal communities are trying to give divers a reason to go out and catch them. Some host lionfish derbies with cash prizes. Local restaurants have begun preparing lionfish meat in dishes like ceviche and fish tacos. Artisans make earrings out of the fish’s fearsome spines. And in 2020, Chavda and fellow scuba diver COO Roland Salatino founded Inversa. Now, they pay solo hunters and fishing collectives in a dozen countries around the Caribbean and Mediterranean to harvest the fish for their skin.</p><p>After starting with just a few divers, Inversa now works with a cast of thousands, promising reliable and prompt payment for their catch and teaching them how to deal with the risk of sting, which is painful but not lethal. Sometimes that means the company sponsors its own lionfish derbies; other times it means working with local governments to get exceptions to preservation laws. (“There’s a very good reason why people usually aren’t allowed to hunt on coral reefs,” Chavda says.)</p>
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<p>Considering how quickly invading lionfish can take over a new reef, haphazard, broad-focused hunting tends not to make a difference, Salatino says, comparing it to “weeding every fortieth weed.” Instead, Inversa encourages the communities it works with to focus on what it calls “management zones,” which divers can return to and comb over again and again. </p><p>“There’s a replenish rate,” Chavda adds. “You remove them on Monday, and then you have to come back in two or three months.”</p><p>A single hunter might snare 15 fish on a slow day or 70 if they find an especially hot lionfish spot. Inversa collects the take every week from docks in Nassau and South Florida. At a processing center in Tampa, a staffer skins the fish by hand, carefully removing the venomous spines. The meat goes to restaurants, and the skin is shipped to Inversa’s tanning facilities in Ohio. Everything else gets ground up for fish oil or bait.</p>
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<img alt="two hands stretch a triangle of bright blue, scaly leather. A piece of black leather is in the background" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/LiofishLeather.width-990.jpg"/>
<figcaption><p>A piece of Inversa's lionfish leather. Image courtesy of Inversa Leathers</p>
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<p>In Ohio, the lionfish skins undergo an intricate, 52-step tanning process. They’re bathed and rebathed in various solutions, with names like “deliming” and “pickling,” which manipulate their pH level. This process allows tanners to target the fibers of the fish skin, opening up the network of collagen that keeps the skin together, helping a chemical “tanning agent” bind to that network, and then locking it together again. The result is that the “overall structure of the skin is reinforced,” Salatino explains. “The oils and fats and all those bits get taken out. You’re left with the strong, reinforced leather.” The end result: handbags, wallets, belts, and sneakers with that distinctive scaly pattern, sold by exotic leather companies that otherwise might focus on shark, bison, or stingray.</p><p>From the start, Inversa leathers have been in high demand. “We’ve never not had a backlog,” Chavda says. They purchased hundreds of fish per week this past year from individual hunters and fishing collectives, the biggest two-day haul topping 7,000 fish. And they recently purchased new tanning drums that can handle seven times their previous maximum material.</p><p>Those drums won’t just hold lionfish. Inversa recently began expanding into other invasive species, including the pythons that have a literal chokehold on Florida’s Everglades. “They kill 99% of small mammalian life,” Chavda says. “There used to be otters around, squirrels, bunnies, songbirds, alligators.” The irony, he points out, is that python skin leather is actually in demand in parts of the world where the snakes are native and close to endangered. He and Salatino keep a running list of some 4,000 invasive species that Inversa might someday turn into products. Much like the lionfish, “We’d like to stop using the python where they’re becoming more and more endangered, instead using them from the areas where they’re actually decimating our life,” Salatino says. One handbag at a time.</p>
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<p data-block-key="c60sn">Venomous lionfish are taking over the Caribbean and the Mediterranean Sea, eating everything in their paths. One solution: handbags and belts.</p>

A light blue brain scan against a black background with two purple C-shaped regions highlighted in purple

A brain scan from Fred Barrett's lab with the location of the claustrum indicated in purple. Image Credit: GBH/NOVA

How do psychedelics work? This brain region may explain their effects

<p>Even if you’ve never used magic mushrooms, you may have heard what the experience can be like. People often hallucinate, seeing vivid colors or swirling patterns. And while not everyone has a positive experience, many users report feeling a deep sense of connection to the universe. </p><p>Now, medical researchers are exploring ways to harness magic mushrooms and other psychedelic substances to help treat mental health conditions like depression, addiction, and PTSD—sometimes with dramatic results. But what actually happens in the brain during a psychedelic experience? Fred Barrett, a neuroscientist at Johns Hopkins University, is one of the scientists trying to figure that out. His work suggests that “a brain region called the claustrum may be at the center of all of this,” <a href="https://www.pbs.org/wgbh/nova/video/can-psychedelics-cure/">he told NOVA.</a></p>
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<p>The claustrum is a set of two slight strips of gray matter–one tucked deep inside each brain hemisphere–that are connected to almost every other region of the brain. Francis Crick (of DNA fame) and neuroscientist Christof Koch suggested in 2005 that the calustrum’s position and connectedness made it a likely “conductor of consciousness.” Barrett compares it to a switchboard that tells other brain regions to turn on and off in response to changing stimuli.</p><p>Take, for example, receiving an email, he said. You might hear the telltale ding, and your claustrum would coordinate each step you take next. You would read the text using your visual cortex. Then your claustrum-as-switchboard would recruit your prefrontal cortex to decide whether to send a response. Once you make your choice, your claustrum would tell the decision-making regions in the prefrontal cortex to turn off and mobilize your language region and motor cortex so you can start typing words.</p><p>Knowing that the claustrum is crowded with receptors that psychedelics act on, Barrett and his colleagues wondered what happens to it when someone takes psilocybin, the hallucinogenic compound in magic mushrooms. In <a href="https://pubmed.ncbi.nlm.nih.gov/32454209/">a recent study</a>, he and his colleagues used a functional MRI machine to observe blood flow in the brain before and after 15 people took either psilocybin or a placebo. Neural activity in the claustra of study participants who took psilocybin was reduced by 15% to 30%, as if the switchboard operator had walked away.</p><p>With the big boss out to lunch, Barrett said, different regions of the brain can interact in radically different ways. “Networks that normally don’t turn on at the same time may turn on and stay on, and they begin to fight for control,” Barrett said. “And other brain networks that would normally be involved in emotions or memories are firing on and off in an unpredictable fashion.” </p><h4>Watch: How Psychedelics Change the Brain</h4>
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<p>With the claustrum turned down, Barrett said, his team has also noticed that a network of regions called the default mode network can go quiet as well. This network is active when we think about ourselves, so its dawdling may contribute to the feeling of egolessness that so many psychedelics users report. Research has shown that people who struggle with depression, anxiety, or other mental health conditions have difficulty recovering in part because their default mode networks are stuck in a rut—that “default” setting—which can include a powerful cycle of repetitive, negative thoughts and behaviors that only get stronger as they replay. </p><p>But the sudden upheaval wrought by the claustrum’s mushroom-induced coffee break seems to have the potential to jolt the brain out of this cycle. “It may be that in this state, the normal repetitive thoughts that are baked into some neural circuits after years and years of use become less strong,” Barrett said. That may leave room for other, usually quieter circuits to have a say.</p>
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<p>He compares the situation to a theater production in which the director suddenly leaves. The actors don’t know what to do, so they just keep saying their lines, sometimes all at once or out of order. “You may come out with a performance that is just completely disorganized,” he said. “Or you may come out with a performance that’s rearranged in a very interesting way that nobody had thought of before.” Barrett points to this dynamic as one reason psychedelic therapy may have so much potential to treat mental health conditions. In normal talk therapy, “you’re battling the circuitry that you’ve built up over a long period of time,” he says—instead of radically reorganizing it.</p><p>The profound transformations some study participants have experienced through psychedelic-assisted therapy may be possible because when the claustrum’s control is disrupted, the brain becomes more “plastic,” or flexible and open to change, Barrett said. Plasticity may be key to at least allowing that growth to happen, but it’s only the first step. </p><p>“Simply making the brain more plastic itself doesn’t necessarily always lead to a positive outcome,” he added. A controlled environment with trained therapists to guide and support the person during and after the experience is crucial to promoting that plasticity, “which can lead to learning, which can lead to healing and growth.” </p><h4>Watch: Can Psychedelics Cure?</h4>
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<p data-block-key="lqn01">The claustrum seems to act as a switchboard, telling different parts of the brain when to turn on and off. But what happens when the switchboard operator steps away?</p>

Four bright orange loops brand off of a dark blue blob

A transmission electron micrograph of HIV-1 virus particles (orange) replicating from the plasma membrane of an infected H9 T cell. Credit: NIAID, Flickr

How a select few people have been cured of HIV

<p>Over the past year, news of two new people cured of HIV grabbed headlines, stirring hopeful talk of what these scientific wonders might portend for the four-decade fight against the virus. </p><p>To researchers working in the HIV cure arena, these cases are inspiring because they prove it is in fact possible to eradicate this extraordinarily complex virus from the body. </p>
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<p>That said, such cures are the result of treatments too toxic to attempt on all but a select few. So while they provide a scientific roadmap toward success, they do not necessarily make researchers’ job any easier as they work to develop alternatives: safe, effective and, crucially, scalable therapies to cure HIV.</p><p>“HIV has been a tough nut to crack,” says Marshall Glesby, an infectious disease specialist at Weill Cornell Medicine in New York City and a coauthor of one of the recent HIV cure case studies. “But there is incremental progress being made in terms of our understanding of where the virus hides within the body and potential ways to purge it from those sites.”</p><p>The HIV cure research field is yet quite young. And it likely never would have ballooned as it has in recent years were it not for the very first successful cure—one that served as a catalyst and guiding light for scientists.  </p>
<h3><b>A transformative success</b></h3><p>During the late 1990s and early 2000s, the HIV research establishment focused the lion’s share of its energy and resources on treatment and prevention of the virus. Actually curing HIV was generally regarded as a distant dream, with only a small set of researchers pursuing such a goal. </p><p>Then, in 2008, German scientists <a href="https://www.nytimes.com/2008/11/14/health/14hiv.html">announced</a> the first case of what would ultimately be deemed a successful <a href="https://www.nejm.org/doi/full/10.1056/nejmoa0802905">cure of the virus</a>. This proof of concept ignited the field and sent financial investment soaring—to <a href="https://www.avac.org/sites/default/files/resource-files/Global_Investment_HIV_CureResearch_and_Development2020.pdf">$337 million</a> in non–pharmaceutical industry funding in 2020, according to the HIV nonprofit AVAC.</p><p>Clinicians were able to cure HIV in an American man living in Berlin named Timothy Ray Brown, by exploiting the fact that he had also been diagnosed with acute myeloid leukemia, or AML. This made Brown a candidate for a stem cell (bone marrow) transplant to treat his blood cancer. </p><p>Brown’s treatment team relied on the existence of a rare genetic abnormality found among people with northern European ancestry. Known as the CCR5-delta32 mutation, it gives rise to immune cells lacking a certain coreceptor called CCR5 on their surface. This is a hook to which HIV typically latches to begin the process of infecting an immune cell and hijacking its machinery to manufacture new copies of the virus. </p><p>The clinicians found a stem cell donor who was not only a good genetic match for Brown, but who also had the CCR5-delta32 mutation. First they destroyed Brown’s immune system with full-dose chemotherapy and full-body radiation. Then they effectively gave him the donor’s immune system through the stem cell transplant. This cured his HIV by ensuring that any remaining virus in his body was incapable of infecting his new immune cells.</p>
<h3><a href="/wgbh/nova/video/ending-hiv-in-america/">Ending HIV in America</a> (2022)</h3>
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<p></p><p>Variations of this method have yielded cures, or likely cures, in four other people during the years since. These cases provide researchers with increasing certainty that it is possible to achieve the ultimate goal: a sterilizing cure, in which the body has been rid of every last copy of virus capable of producing viable new copies of itself. </p><p>“It was not a given that if you completely replace the immune system, even with a purportedly non-susceptible immune system, that you would cure infection,” says Louis Picker, associate director of the Vaccine and Gene Therapy Institute at the Oregon Health &amp; Science University. “It was possible that HIV could be hiding in non-immune cells, like endothelial cells, and still find targets to infect.” </p><p>But the small cohort of people who have been cured or likely cured to date, Picker says, “show that’s not the case.”  </p><p>Nevertheless, these successes have not opened the door to a cure for HIV available to much more than a few of the estimated <a href="https://www.unaids.org/en/resources/fact-sheet">38 million people</a> living with the virus worldwide. Critically, it is unethical to provide such a dangerous and toxic treatment to anyone who does not already qualify for a stem cell transplant to treat blood cancer or another health condition. </p><p>Brown, for one, nearly died from his treatment. And a number of efforts to repeat his case <a href="https://www.nature.com/articles/nature.2013.14324">have failed</a>.</p>
<h3><b>Why is HIV so hard to cure?</b></h3><p>Highly effective treatment for HIV hit the market in 1996, transforming what was once a death sentence into a manageable health condition. Today, the therapy, a combination of drugs called antiretrovirals, is so safe, tolerable and effective, that it has extended recipients’ life expectancy to <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081355">near normal</a>. But despite the fact that these medications can inhibit viral replication to such a degree that it’s undetectable by standard tests, they cannot eradicate HIV from the body. </p><p>Standing in the way is what’s known as the HIV reservoir.</p><p>This <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4048589/">viral reservoir</a> is composed in large part of long-lived immune cells that enter a resting, or latent, state. Antiretrovirals only target cells that are actively producing new copies of the virus. So when HIV has infected a cell that is in a non-replicating state, the virus remains under the radar of these medications. Stop the treatment, and at any moment, any of these cells, which <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8537114/">clone themselves</a>, can restart their engines and repopulate the body with HIV.</p>
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<p>This phenomenon is why people with HIV typically experience a viral rebound within a few weeks of stopping their antiretrovirals. And it is the reason why, given the harm such viral replication causes the body, those living with HIV must remain on treatment for the virus indefinitely to mitigate the <a href="https://www.nejm.org/doi/full/10.1056/nejmoa062360">deleterious impacts</a> <a href="https://www.nejm.org/doi/full/10.1056/nejmoa1506816">of the infection</a>.</p><p>“A key new advance is the finding that those cells which harbor the virus seem resistant to dying, a problem with cancer cells,” HIV cure researcher Steven Deeks, a professor of medicine at University of California, San Francisco, says of the viral reservoir. “We will be leveraging new cancer therapies aimed at targeting these resilient, hard-to-kill cells.”</p>
<h3><b>Follow-up acts</b></h3><p>Brown stood alone on his pedestal for over a decade. </p><p>Then, at the 2019 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle, researchers announced two new case studies of men with blood cancer and HIV who had received treatments similar to Brown’s. The men, known as the <a href="https://www.croiconference.org/abstract/analytic-treatment-interruption-ati-after-allogeneic-ccr5-d32-hsct-aml-2013">Düsseldorf</a> and <a href="https://www.pbs.org/wgbh/nova/article/second-patient-has-entered-long-term-remission-hiv/">London patients</a>, were treated for Hodgkin lymphoma and AML, respectively. By the time of the conference, both had spent extended periods off of antiretroviral treatment without a viral rebound. </p><p>To this day, neither man has experienced a viral rebound—leading the authors of the London and Düsseldorf case studies recently to assert that they are “definitely” and “almost definitely” cured, respectively.</p><p>In February 2022, a team of researchers reported at CROI, held virtually, the first possible case of an HIV cure in a woman. The treatment she received for her leukemia represented an important scientific advance.</p><p>Called a <a href="https://pubmed.ncbi.nlm.nih.gov/27788764/">haplo-cord transplant</a>, this <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6595267/">cutting-edge approach</a> to treating blood cancer was developed to compensate for the difficulty of finding a close genetic match in the stem cell donor–which is traditionally needed to provide the best chance that the stem cell transplant will work properly. Such an effort is made even more challenging when attempting to cure HIV, because the CCR5-delta32 mutation is so rare. </p><p>The American woman received a transplant of umbilical cord blood from a baby, who had the genetic mutation, followed by a transplant of stem cells from an adult, who did not. While each donor was only a partial match, the combination of the two transplants was meant to compensate for this less-than-ideal scenario. The result was the successful blooming of a new, HIV-resistant immune system.</p><p>The authors of the woman’s case study, including Weill Cornell’s Marshall Glesby, estimate that this new method could expand the number of candidates for HIV cure treatment to about 50 per year. </p>
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<img alt="Close-up of green, purple, and red pills scattered on a countertop" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/HIV_antiretrovirals.width-990.jpg"/>
<figcaption><p>A variety of antiretroviral drugs used to treat HIV infection. Image Credit: NIAID, Flickr</p>
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<p>In July, at the International AIDS Conference in Montreal, researchers announced the case of a fifth person possibly cured of HIV. Diagnosed with the virus in 1988 and 63 years old at the time of his stem cell transplant three years ago, the American man is the oldest to have achieved potential success with such a treatment and the one living with the virus for the longest. Because of his age, he received reduced intensity chemotherapy to treat his AML. Promisingly, he still beat both the cancer and the virus. </p><p>The lead author of this man’s case study, Jana K. Dickter, an associate clinical professor of infectious disease at City of Hope in Duarte, California, says that such cases provide a guide for researchers. “If we are able to successfully modify the CCR5 receptors from T cells for people living with HIV,” she says, “then there is a possibility we can cure a person from their HIV infection.” </p><p>Scientists also know of two women whose own immune systems, in an extraordinary feat, appear to have cured them of HIV. Both are among the approximately 1 in 200 people with HIV, known as elite controllers, whose immune systems are able to suppress replication of the virus to low levels without antiretroviral treatment. </p><p><a href="https://www.acpjournals.org/doi/10.7326/L21-0297">Researchers believe</a> that these women’s immune systems managed to <a href="https://www.nature.com/articles/s41586-020-2651-8">preferentially eliminate</a> immune cells infected with viral DNA capable of producing viable new virus, ultimately succeeding in eradicating every last such copy.</p>
<h3><b>The search for the holy grail</b></h3><p>As they seek safer and more broadly applicable therapeutic options than the stem cell transplant approach, HIV cure researchers are pursuing a variety of avenues.</p><p>Some investigators are developing genetic treatments in which, for example, they attempt to edit an individual’s own immune cells to make them <a href="https://www.croiconference.org/abstract/delayed-viral-rebound-during-ati-after-infusion-ccr5-zfn-treated-cd4-t-cells/">lack the CCR5 coreceptor</a>. </p><p>“The science that I am particularly excited about and that we and others are working on is to make this treatment as an in vivo deliverable therapy that would not rely on transplant centers and could ultimately be given in an outpatient setting,” says Hans-Peter Kiem, director of the stem cell and gene therapy program at the Fred Hutchinson Cancer Center in Seattle.</p><p>Then there is what’s known as the <a href="https://www.science.org/doi/10.1126/scitranslmed.abl3836">“shock and kill”</a> method, in which drugs are used to flush the virus from the reservoir and other treatments are then used to kill off the infected cells. Conversely, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7019976/">“block and lock”</a> attempts to freeze the reservoir cells in a latent state for good. Researchers are also developing <a href="https://hivinfo.nih.gov/understanding-hiv/fact-sheets/what-therapeutic-hiv-vaccine">therapeutic vaccines</a> that would augment the immune response to the virus. </p><p>“Progress will be incremental and slow,” Picker predicts, “unless there is a discovery from left field—an unpredictable advance that revolutionizes the field. I do think it will happen. My personal goal is to be a very good left fielder.”</p><p><i>Correction: Dr. Glesby's quote in the fourth paragraph was initially published with a typo, saying "track" instead of "crack."</i></p><p><i>This reporting was supported by the Global Health Reporting Center.</i></p>
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<p data-block-key="cvcxv">Scientists have cured a handful of people of HIV by piggybacking on treatments they received for blood cancer. But does that bring a widespread cure any closer?</p>

A small spacecraft with outstretched solar panels approaches two large rocks

llustration of NASA’s DART spacecraft and the Italian Space Agency’s  LICIACube prior to impact at the Didymos binary system. Image Credit: NASA/Johns Hopkins APL/Steve Gribben

DART spacecraft slams into asteroid

<p>Tonight, around 6.8 million miles away from Earth, NASA slammed a spacecraft into an asteroid in a bid to change the rock’s trajectory. This is the agency’s first test of a technology designed to defend Earth against <a href="/wgbh/nova/article/asteroid-dust-ice-age/">asteroids or comets</a> that might one day threaten to collide with our planet. </p>
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<p>“Humans: one, asteroids: zero!” declared NASA communications strategist Tahira Allen amid celebration and cheering at Johns Hopkins University's Applied Physics Laboratory, over a NASA livestream.</p><p>From “Armageddon” to “Don’t Look Up,” Hollywood has long imagined how scientists could redirect an asteroid headed toward Earth. With lower stakes, NASA is testing its own theory with the <a href="https://www.pbs.org/wgbh/nova/video/can-humans-deflect-asteroid/">Double Asteroid Redirection Test (DART)</a>. The mission launched <a href="https://www.pbs.org/wgbh/nova/article/nasa-dart-deflect-hazardous-asteroid-didymos/">10 months ago</a>, carrying with it an autonomous guiding system called SMART Nav to help it maneuver and target an asteroid. </p><p>For the test, scientists chose Dimorphos, a 525-foot asteroid “moonlet” that circles a larger asteroid called Didymos. "We needed something with a moon that was small enough that we could move it with a strike from a spacecraft, but not so small that we would wreck the moon,” Andy Rivki, a scientist working on the DART mission said in a livestream leading up to the impact. (Neither Dimorphos nor Didymos poses any threat to Earth) </p>
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<p>The spacecraft itself had a camera that transmitted its approach live. As it blazed toward Dimorphos at 4 miles per second, the asteroid grew from a tiny white dot in the video feed to a detailed view of gray rocks and rubble that filled the screen. And then: nothing.</p><p>“We’ve made impact!” DART mission members shouted as the room erupted into cheers. </p><p>“Now is when the science starts,” said Lori Glaze, director of NASA's planetary science division, after the impact. It will be days before scientists can calculate if, and by how much, the asteroid’s trajectory was altered. As Dimorphos circles around, telescopes on Earth can help capture variation in its orbit, and hence, the success of the mission.</p><p>In the next 100 years, a scenario like the one in “Armageddon” is highly unlikely. But DART may be proof that if Earth were to be <a href="/wgbh/nova/video/day-the-dinosaurs-died/">threatened by an asteroid</a>, humans could do something about it. “We are embarking on a new era of humankind, an era in which we potentially have the capability to protect ourself from something like a dangerous, hazardous asteroid impact,” Glaze said.</p><p><i>Correction: An earlier version of this article attributed quotes from Lori Glaze to Laurie Leshin.</i></p>
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<p data-block-key="vqnhb">The mission is a test to see if NASA could knock an Earth-bound asteroid off its path, should we ever need to.</p>

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