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Cure or Carcinogen? CRISPR-Cas9 May Cause Cancer

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 A promising vehicle for gene therapies may have just popped a flat tire. Two new studies on the DNA editing tool CRISPR-Cas9 reveal that it may indirectly trigger new cancers—even when used to replace cancer-causing genes.
 

 The independent studies from Novartis and Sweden’s Karolinska Institute both appeared yesterday in the journal Nature Medicine and point a finger at the same cause, a switch that turns off cancer fighting molecular machinery. When this switch is off, gene therapies more readily take hold. But it also means that the potential for cancer is higher among tweaked cells.
 
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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/hela_cells_4.width-990_187FrBK.jpg"/>
<figcaption>A cell undergoing apoptosis, a form of self-destruction that can prevent cancer.
 
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 In normal cells, a cellular watchdog known as
 
 p53
 
 is on the lookout for DNA breakages like those caused by marauding UV radiation or, in this case, CRISPR-Cas9.
 
 p53
 
 calls to arms a range of tools that either repairs the DNA or causes the cell to self-destruct. In either case,
 
 p53
 
 stymies gene therapies.
 

 When
 
 p53
 
 is disabled or absent, gene therapies take hold, which means those cells are wildly over-represented at the end of the gene editing process. But it also means that those cells lack
 
 p53
 
 ’s cancer fighting skills.
 

 Experimental CRISPR therapies are already undergoing clinical trials, which means the potentially fatal flaw somehow slipped through rounds of testing in mice and human cells.
 
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 The new technology makes gene editing faster, cheaper, and easier than ever before. Here’s how.
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 Here’s Sharon Begley, reporting for Stat:
 
<blockquote>

 Karolinska’s Haapaniemi said the effect shows up in large-scale experiments like hers and Novartis’ “but can be missed in small-scale studies where people only focus on editing one gene in one cell type.” In speaking to other scientists, she said, “it seems that other teams have noticed the effect of p53 on editing,” but have not highlighted it.
 
</blockquote>

 Begley continues:
 
<blockquote>

 As for why no one has reported CRISPR’d mice getting cancer, Haapaniemi said, “This is a good question.” One reason might be that “laboratory mice are killed early,” perhaps leaving too little time for them to develop cancer.
 
</blockquote>

 The good news is that not all gene-editing therapies trigger
 
 p53
 
 and cause it to undo the therapy. When CRISPR is used only to remove problematic DNA rather than insert new code, the watchdog appears to stay quiet. Ditto when only individual letters of DNA code are changed without cutting both strands of DNA. These more limited techniques underpin treatments for a variety of genetic conditions, from sickle-cell anemia to cystic fibrosis.
 
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 A revolution in gene editing enables scientists to create and edit DNA like never before.
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 Still, numerous promising CRISPR gene therapies waiting in the wings may have to be sidelined until a solution to the
 
 p53
 
 problem can be found. These two studies also underscore just how far scientists are from fully understanding the tool that had promised to give us control of our own genetic destiny.
 
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 Image credit: NIH

One example of oceanic manta rays’ unusual spotting pattern

In a First, Scientists Discover Oceanic Manta Ray Nursery

Oceanic manta rays seem to glide forth from the depths as goliaths, fully formed. Marine biologists have struggled for years to identify where and when juveniles come of age.
 <a href="https://link.springer.com/article/10.1007/s00227-018-3364-5">
 A new study
 </a>
 published today by marine biologists from the Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration (NOAA) has, for the first time, identified a nursery for these 20-foot enigmas. This finding will buoy federal efforts to protect the species, which was recently listed as threatened under the Endangered Species Act.


 Mysteries abound about the movements and reproduction of oceanic mantas—researchers even recently suggested that what had long been considered a single species may in fact be two.


 But the new study manages to chip away at one of manta rays’ riddles. The discovery of the nursery seems to resolve why juvenile oceanic manta rays are rarely seen mixed in with adults, which is a common occurrence for their coastal cousins, the reef manta. It turns out that oceanic manta young have been squirreling themselves away in secret kindergartens. Fittingly, the one researchers have identified was hiding in plain sight.


 The nursery unmasked by the team lies in Flower Garden Banks Marine Sanctuary off the coast of the Texas-Louisiana border. Finding it was doubly serendipitous.


 The first bit of luck was that the site has long been frequented by NOAA biologists conducting a variety of biological surveys. Their meticulous notes and opportunistic photographs chronicled 357 different manta sightings dating back to 1993, forming a long-term dataset needed to conclusively prove the site is indeed a nursery. None of the researchers, however, typically worked on manta rays, and did not realize the importance of what they were seeing.


 Cue Joshua Stewart, the lead author of the paper and a manta specialist at Scripps. “I started working with the sanctuary on some other projects related to mantas. […] I was there to collect some tissue samples, and the very first manta I dived with at the banks looked a little small.” Upon further investigation he realized it was a male with “teenie-weenie” reproductive organs indicative of a juvenile. “I said ‘Woah’ because I had only seen two or three juveniles anywhere else in the world.”


 They came up from the dive and Stewart turned to the NOAA researchers to express his excitement, only to find their response blasé. According to Stewart, “They said ‘that’s pretty common for around here.’”


 The team then combed through the manta sighting records, an important step because the high abundance of juveniles only satisfies one criterion for qualifying as a salt-water nursery. The NOAA dataset, however, ticked the other two boxes; the area had been utilized in the same way across many years and individual juveniles did stick around for more than transitory period.


 They were able to establish the last point by pouring over their photo archive, which reveal the unique spotting pattern on each manta’s belly. Despite lacking hands, it turns out mantas have a fingerprint of sorts.

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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/manta-ray-2.width-990_zAa3Fox.png"/>
<figcaption>Another example of oceanic manta rays’ unusual spotting pattern
 
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 While the nursery may be the only one that has been conclusively identified, Dr. Andrea Marshall, co-founder of the Marine Megafauna Foundation and a scientist unaffiliated with the study, was quick to contextualize the finding. “It’s certainly not the only one known,” she said. Marshall has quite the credentials to back up the assertion.
 <a href="http://www.QueenOfMantas.com">
 Her personal website
 </a>
 points out she was the first person in the world to finish a doctorate on mantas.


 Marshall continued, “I know of about four other places where we are seeing small-sized oceanic mantas on a regular basis.” She also pointed out that “at some of the other places they I mentioned they are newborn-sized consistently.”


 Watch a video about the newly-discovered nursery.


 Stewart readily conceded that Flower Garden Banks is not entirely unique, but pushed back at the suggestion that newborns were not well-represented there. “The spread of sizes we see suggests to me that there is a range of juvenile ages represented at the banks.” He added more than a quarter of the sightings were animals with a wingspan less than 1.6 meters, which despite being the height of an adult human, falls well under the size that manta babies hit by their first birthday.


 Stewart and Marshall both agreed that this type of investigation fills dangerous gaps in our knowledge of the now imperiled species. As Marshall put it, “Understanding more about a very critical habitat for mantas is hugely important.”


 Internationally, oceanic manta rays are under threat from targeted fishing for the lucrative market for Chinese traditional medicines, the efficacy of which is not underpinned by medical evidence. In U.S. waters though, the biggest challenge is when the rays are caught as by-catch when fisherman use nets to target other species or when some types fishing gear disturb the sea floor.


 The paper stops short of explaining why Flower Garden Banks acts as a magnet for young mantas, but Stewart speculates that its location is critical. The Banks lay in close proximity to deep water feeding grounds but are also shallow protected reefs. That means that baby mantas can safely warm themselves in the sun after a feeding foray in the adjacent cold dark depths. Sunning directly above their deepwater snack bar could leave them exposed. Bite marks on the wings of some juvenile mantas at the site are a testament to the dangers of tiger sharks and other predators for the rays lacking their immense adult stature.

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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/manta-ray-bites.width-990_Q4InpTV.png"/>
<figcaption>Bite marks on the wings of a juvenile manta
 
 </figcaption>
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 The study will no doubt be a boon for NOAA. The agency is required to identify critical habitat and measures to protect the species now that oceanic mantas have been listed under the U.S. Endangered Species Act. As the authors of the paper posit, Flower Garden Banks may be a particularly important site to protect, because young mantas do not come around often. Manta moms carry their developing young for more than a year before giving live birth to just a single pup. They then go two to seven years before giving birth again.


 A manta ray giving birth


 The mysteries of the manta may never be fully unravelled, but Stewart’s study suggests another reason why Flower Garden Banks Marine Sanctuary may be a great place to start looking. It turns out the nursery is a multicultural manta kindergarten. Through DNA samples and photos, the authors are confident that both the original oceanic manta and the putative second species frequent the site.


 Images courtesy FGBNMS/G.P. Schmahl, Joshua Stewart

Carbonate found in many types of rocks could help suck carbon dioxide from the atmosphere at store it stably on the ocean floor.

Clever Chemistry Could Capture Carbon Dioxide While Producing Hydrogen Fuel

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 Keeping the planet cool looks like it will take more than just reducing our carbon emissions. Scientists now say that holding climate to less than 3.6˚ F warming worldwide—the threshold for dangerous warming—will almost certainly require sucking greenhouse gases out of the atmosphere. That’s usually a costly proposition.


 But yesterday, researchers painted a picture of how to do so and their scalable scheme has a doubly beautiful twist—they claim actually produces useful energy without breaking the bank. Perhaps it is possible to have your cake and eat it, too.


 The new method involves a well-established process wherein water is split into energy-rich hydrogen gas and sets of paired oxygen and hydrogen atoms called hydroxide ions. The latter is able to gobble up carbon dioxide from the air, but only up to a certain point. Hydroxide’s carbon appetite can be increased substantially, however, by adding a substance called carbonate that’s found in many sedimentary rocks like limestone. The carbonate reacts with the carbon dioxide to form a chemical called bicarbonate—one half of the compound that makes up baking soda.


 To be truly carbon negative, the process would work like this: use renewable energy to split sea water and capture the hydrogen gas for later use. Then take carbonate dug up from the ground, mix it with the remaining hydroxide-rich seawater, and release it into the ocean where it pulls carbon dioxide out of the air.


 This process is not the only way to produce energy while capturing carbon dioxide. Growing crops to turn them into biofuels would do the same, but it would also require huge tracts of land. The electrolysis-based strategy considered in this study can draw down ten times as much carbon as a biofuel approach at about the same cost, even after factoring in the energy needed to mine and crush large amounts of carbonate rock.

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 This approach has a much smaller land footprint than biofuels, according to the study, and therefore could suck more carbon dioxide from the atmosphere.


 However, the plan may have its own challenges.


 Here’s Scott Johnson at Ars Technica:

<blockquote>

 Quarrying rock has its own localized environmental impact, as could pumping all that extra bicarbonate into the ocean. But the researchers argue that the idea is worth studying much more closely. The more options for removing atmospheric CO 2 we work up, the more likely it is that one catches on when serious incentives finally arrive.

</blockquote>

 Another hiccup is that the plan assumes there will be a market for huge amounts of hydrogen gas, which can be tricky to transport and use. Transportation may not be as much of a concern, though, as hydrogen could be used to store energy produced by intermittent renewable sources, like wind turbines or solar panels, for later use. With the right incentives, this could be a missing ingredient for an electricity grid fully based on renewable energy.

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 Photo credit:
 <a href="https://commons.wikimedia.org/wiki/File:Tilted_Jurassic_Carbonate_Rock_Layers_at_Baleal_in_Portugal.jpg">
 Alessandro Righetti/Wikimedia Commons (CC BY)
 </a>

Scientists now say that holding climate to less than 3.6˚ F warming worldwide—the threshold for dangerous warming—will almost certainly require sucking greenhouse gases out of the atmosphere.

The Coral Reefs We Depend On Most May Fall First

Emily Kelly’s first experience with corals came at age 12 on the Great Barrier Reef in Australia. “There’s just a kaleidoscope of colors. There’s something happening everywhere.” To Kelly, reefs are like a bustling city—grunting fish chatter, snapping shrimp, and parrotfish rasping algae off of every surface. “There’s a lot of noise on that healthy coral reef system, just like New York.”


 Two decades later, as a full-fledged marine biologist, she has visited too many
 <a href="https://www.int-res.com/abstracts/meps/v516/p35-47/">
 silent reefs
 </a>
 . “You’re missing out on a lot of the sounds” on a degraded reef, Kelly says. She called them “abandoned cities,” describing the typical vista as “a brown, fuzzy carpet covering a lumpy bottom.” It was a far cry from the pink, blue, and green-hued chaos she’s seen at healthy reefs.


 As these marine metropolises have become ghost towns throughout much the world’s tropical seas, we’ve begun to understand what’s causing them
 <a href="http://www.pbs.org/wgbh/nova/next/earth/mass-coral-bleaching-devastates-great-barrier-reef-for-second-consecutive-year/">
 to fail
 </a>
 .


 Healthy coral reefs are self-repairing and punch above their weight in terms of benefits to humans and biodiversity. They buffer coastlines from the ravages of storms while also providing a home to a quarter of all marine species. They’re also an abundant source of food for many coastal communities.


 But their capacity to feed people is not limitless.


 Two weeks ago, a
 <a href='http://www.pnas.org/content/early/2018/06/12/1708001115"'>
 study
 </a>
 showed that coastal communities, like black holes, have a form of gravity, sucking up fish from nearby reefs. The research team analyzed surveys of 1,800 sites and found that just two bits of information could predict fish numbers on unprotected reefs: the proximity of human settlements and the population density of those settlements, which together they call “human gravity.”


 Higher human gravity means more fishing, which can be devastating to corals, says Kelly, who wasn’t involved in the research. Seaweed-eating fish give corals a competitive edge against their aquatic antagonists, and their loss puts corals at risk. “The number one thing that organisms are competing for on reefs is real estate. You have corals, you have other invertebrates, and you have seaweeds that live on the bottom, too,” Kelly says. “All of them are constantly in competition for space.”


 Most seaweeds are fast growing—some can double in size in a single day. Corals, in contrast, grow no more than a few inches per year. Some boulder corals can only manage a tenth that rate. Were it not for herbivorous fish, what Kelly calls “the lawnmowers of the reef,” seaweed would smother corals. They even chemically attack the colonies in their quest for elbow room. Large herbivores like the noisy parrotfish are a particularly important set of seaweed munchers.

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 Fishing typically drives down numbers of all fish, and co-author Nick Graham noted their previous work has shown that the abundance of herbivores typically tracks the total amount of fish on a reef. As fishing depresses their numbers, coral suffers. But, Kelly says, “Where you have a large number of herbivores and also large bodied herbivores, you end up having much lower amounts of seaweed and also much shorter seaweed.” Seaweeds’ losses are the reef’s gain.


 In other
 <a href="http://advances.sciencemag.org/content/4/5/eaao5493">
 studies
 </a>
 , juvenile corals were most abundant when there were more and bigger herbivorous fish. This relationship becomes even stronger after taking into account subtle differences between individual herbivores, like how long they wait between bites and the size of their dinner plates (i.e. the amount of reef surface area growing seaweeds). These coral tykes are the key to a healthy future for reefs.


 Hale and healthy herbivores even go as far as clearing sites for new construction. When allowed to work at full capacity, these maintenance crews help create something special.

<h2>
 Keeping Up with Sea-Level Rise
</h2>

 At Millennium Atoll, part of the Southern Line Islands a few hundred miles north of French Polynesia, Kelly said they found the reef to be in such good health that the uppermost corals were nearly breaking the surface of the water. They had grown so high, in fact, that baby sharks needed to ride waves to gain access to the labyrinthine hunting ground. “It was amazing,” she says of the expedition to the remote reefs. “Seeing that really put a lot together for me in terms of how a reef can function.”


 Millennium Atoll and other pristine sites in the Central Pacific should be able to keep pace with sea-level rise under all but the most pessimistic climate change forecasts. As coral colonies grow, they cement their calcium-carbonate skeletons on top of rocks and dead coral, raising the overall height of the reef in a process that physical geographer Chris Perry refers to as accretion. Perry and others calculate potential accretion by adding together the growth of coral and other calcifying organisms while subtracting loss from animals that eat or otherwise erode them.

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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/palmyra.width-990_AqtHmDy.jpg"/>
<figcaption>Reefs in the Southern Line Islands of the Central Pacific, like this one at Palmyra Atoll, are some of the most pristine in the world.
 
 </figcaption>
</figure>

 On many reefs, though, the ability of corals to grow is being hampered by overfishing, bleaching, and other threats, jeopardizing the entire reef. In fact, most reefs in the Caribbean and Indian Oceans are too beleaguered to keep pace with projected sea level rise, according to a
 <a href="https://www.nature.com/articles/s41586-018-0194-z">
 study
 </a>
 lead by Perry that was released last month. What’s more, this finding is optimistic, as the estimates they use for accretion can’t account for major events like storms that can level whole reefs.


 That spells trouble for nearby coastlines. Though the study’s authors did not measure the power of waves directly, they point out that when seas rise more than a couple feet above the crest of a reef, more energy from the surf makes its way to the shore. When ocean swells aren’t tempered by long tumbles over shallow reefs, they can reshape coastlines over time and increase the risk of flooding.


 Accretion rates on many reefs in the Caribbean Sea and the Indian Ocean are disconcertingly low, but for different reasons. “The Caribbean [has] a long period or history of reef degradation and that’s being driven by all sorts of different things,” Perry says, including overfishing, water pollution and runoff, and diseases. In the Indian Ocean, however, Perry said low accretion rates are largely driven by coral bleaching.


 Corals turn bone white when seawater temperatures rise too high and will die if the bleaching event lasts too long. Climate change-induced bleaching and loss of herbivores are interwoven threats for reefs, says Graham, also an author of the sea-level rise paper. “One of the drivers of a faster recovery rate [from coral bleaching events] is the biomass, or amount of herbivorous fish, on a reef.” Moreover, even when bleaching and herbivore losses are not severe enough to kill corals outright, they can stress them enough to suppress overall accretion rates.

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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/bleaching.width-990_8EdQkai.jpg"/>
<figcaption>When water temperatures rise too high, corals are forced to eject the colorful algae living inside them. Bleached corals die if the water temperatures do not drop quickly.
 
 </figcaption>
</figure>

 By keeping seaweed at bay, herbivorous fish give baby corals a leg up while also keeping adult corals clear of seaweed. But reefs near coastal populations are likely to have fewer herbivores, and thus are less likely to be able to keep up with sea-level rise. “It is the reefs near people that people depend on for shoreline protection, but also that are most compromised ecologically,” says Joshua Cinner, lead author of the human gravity paper.


 That means coastal communities face a double whammy when nearby reefs are overfished. By removing the marine maintenance team, communities risk losing the habitat that fosters the fish they harvest. They also expose themselves to destructive storm surges and erosive waves that break on the beach rather than the reef.

<h2>
 Protecting Herbivorous Fish
</h2>

 There is a ray of hope, though. The authors of the human gravity paper found that protected reefs may not help widely roaming top predators like sharks and tunas, but they could preserve seaweed-eating fish. Essentially, no-fishing zones do more to protect a reef that’s close to lots of people, even if they can’t fully protect all fish. Such local measures, when combined with global action on climate change, may give the underwater cities a fighting chance.


 One reef that gives Kelly hope is Kahekili on the Hawaiian island of Maui. Since June 2009, it has been classed as a Herbivore Fisheries Management Area, meaning it is off limits to the harvest of herbivores, but still open to other types of fishing. In a relatively short time, coral colonies have flourished, painting more of the ocean floor with their colorful hues.

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 Kahekili is a place where she can reliably find critically-endangered hawksbill sea turtles feeding in the shallows in the afternoons and where coral pinnacles were crowned with frogfish. “Every afternoon at four o’clock in the summer, the surgeonfish spawn, swimming up in these magical dances, intertwining with one another,” she said.


 Perry agrees. “When you see what those really healthy, thriving systems can look like and that they do still exist in places, that gives you hope.”

 

 
 Photo credits: Timothy Treuer, Cory Fuchs, USFWS-Pacific Region, NOAA, Caroline Rogers/USGS

An artist's rendering of a blazar, one of the most energetic entities in the universe

Blazar-Made Intergalactic 'Ghost' Heralds New Era in Astronomy

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 To begin unravelling a century-long mystery in cosmology, astronomers first had to catch a ghost.


 And recently, they did, detecting a single neutrino, a particle so small that it was historically treated as a dimensionless point without width or volume. The detection pointed researchers to a supermassive black hole in a distant galaxy, suggesting an intergalactic source for a variety of exotic and enigmatic cosmic rays that have puzzled the scientific community since the early 20th century.


 Elusive neutrinos are nicknamed “ghost particles”—their tiny size and lack of electrical charge mean they rarely interact with physical matter. But they’re everywhere. If you are tanning at noon, 65 billion neutrinos from the sun will pass through every square centimeter of you each second without any measurable interactions with the molecules of your body.


 Detecting them requires capturing evidence of rare moments when they crash into the cores of atoms.


 Higher energy neutrinos coming from other galaxies are easier to spot than those from our sun, said particle physicist Michelle Dolinski of Drexel University, because faster neutrinos are more likely to smash into things. They present their own challenges, though. “These very high energy neutrinos are more likely to interact” with matter, she said, “but they deposit so much energy in a detector that in order to contain and detect all that energy, the detector has to be very large.”

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 “It’s basically a new window on the universe.”

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 Such a detector is buried deep beneath the South Pole, encompassing 35 billion cubic feet of ice. Fittingly, it’s called IceCube. Its 3D grid of sensors embedded in the ice detected the neutrino when it smashed into the nucleus of a water molecule. The impact exploded the nucleus, blasting out a cone of rippling radiation, mostly in the form of light waves. Computers monitoring the sensors used these ripples to reconstruct the path of the neutrino. Within a minute, they had relayed a message to telescopes around and orbiting the globe to train their sights on a small patch of sky within the Orion constellation.


 There, 19 telescopes saw a distant galaxy occupied by a supermassive black hole called a blazar. It was actively flaring gamma rays, a signature of this type of black hole and a telling coincidence that it was the source of the neutrino.


 The blazar was almost certainly shooting out cosmic rays that pack an even bigger punch, too. Astronomers have long puzzled over the origin of rare but incredible high energy events where atomic nuclei travelling close to the speed of light come crashing into the Earth’s atmosphere. Some of these are called “Oh-My-God particles,” because a single particle can smash into the Earth with the force of a 50-plus mph baseball—an object that’s more than a trillion trillion times more massive.

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 Before now, tracing the origins of this type of cosmic ray has been impossible, Dolinski said, because most are charged particles. “They experience deflections from electric and magnetic fields, so they don’t necessarily point back to the astronomical objects they came from.”


 But these ultra-high-energy cosmic rays are also the only plausible source of the high-energy neutrinos, which fly true, even across intergalactic distances. This is why the teams rely on neutrinos to sniff out the origin of the other particles.


 The discovery also marks a turning point in astronomy. “It’s basically a new window on the universe,” Dolinski said. A decade ago we essentially could only use telescopes to see different waves of light. Then, with the detection of gravitational waves, we gained the ability to hear the universe too. Now, with IceCube recording the impacts of intergalactic neutrinos, we have a way to feel the cosmos.


 “It’s the beginning of a new channel in astronomy,” Dolinski said.

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 Image credit: University of Wisconsin

Detecting one of the cosmos&#x27; smallest particles now allows us to “feel” the universe.

YouTube comment sections are notoriously laced with trolls.

Female Science YouTube Hosts Really Do Get Nastier Comments

Sometimes putting numbers on a problem brings it into perspective.


 YouTube has a well-known problem with commenters. Now, a
 <a href="http://journals.sagepub.com/doi/abs/10.1177/0963662518786654?journalCode=pusa">
 new study
 </a>
 of science-themed YouTube channels shows just how extensive that problem can be if you’re a woman hosting a science show.


 Researchers found that female hosts were more than twice as likely to receive negative comments and twelve times as likely to be the target of sexist ones.

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 Women host just 32 of the 391 most popular YouTube channels with a science, engineering and mathematics focus. That’s a problem, according to the study authors, because distorted media representation of science and scientists may tacitly discourage young girls from picturing themselves in these professions.


 “I think the number one thing we should be doing is looking for ways to include other voices in communicating science,” said Will Grant, a senior lecturer at The Australian National University and co-author of the new study.


 Lead author Inoka Amarasekara examined 23,005 comments from 450 videos spread across 90 channels, sorting each comment into one of six categories, including “hostile,” “appearance-based,” positive, negative, sexist, and neutral.


 Amarasekara didn’t use automated tools to parse the comments. Instead, she assessed all 23,005 herself. Her immersion into the world of YouTube comments gave her new respect for female science communicators. “I can also only imagine how it must feel to be on the receiving end of certain kinds of hostility,” she said.


 Her results were not entirely bleak. Female hosts actually received slightly more positive comments than their male counterparts. Amarasekara said some of the positivity stood out to her as much as the negative comments. (Her prescription for proper commenting etiquette is simple: “Make positive feedback a habit.”)

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 The study struck a chord with female science channel hosts. Vanessa Hill, who hosts the YouTube channel
 <a href="https://www.youtube.com/channel/UCt_t6FwNsqr3WWoL6dFqG9w">
 BrainCraft
 </a>
 and is no stranger to gendered criticism. “In some ways, [the study] seems like it’s stating the obvious,” she said. “Of course, if you fall under any kind of minority group—whether that’s a woman in science, whether that’s a person of color—of course your comments are going to be worse…But having that data is something we’ve never had before.”


 For Hill, YouTube is the most important platform for teenagers to engage with science and scientists, and she thinks it’s still worth being on the platform, even with the toxic comments. “It’s the main place for entertainment, for video in general for 14- to 17-year-olds,” she said. At that age, representation on YouTube makes an impression. “If they’re going on and not seeing women communicating science,” she added, they might not connect women with science.


 “I think it’s really important that we represent ourselves on all different media platforms.”

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 Photo credit: public domain

One researcher traversed a version of hell, personally analyzing over 23,000 YouTube comments.

Miles of Water Found on Mars. Could It Support Life?

A team of scientists announced today that they found a large body of liquid water beneath the southern ice caps of Mars. The discovery is the result of a decade-long effort to find liquid water on Mars and one that may rewrite the odds of finding life on the Red Planet.


 The body of water is about 12.5 miles across and sequestered beneath nearly a mile of ice at the south pole. Its waters are likely so salty that they remain liquid despite the frigid -90˚ F conditions at the bottom. The discovery was reported in the journal
 
 Science
 
 .

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 If confirmed, this would be the most significant body of liquid water found on Mars to date. The only other evidence of liquid water on Mars has been of ancient bodies of water and transient seasonal flows. Finding a current stable body of water, similar to the subglacial lakes found under Antartica, sparks hope that we may be closer than ever to discovering life on our planetary cousin.


 “This lake on Mars, even if salty, is now the best site for finding extant life on Mars,” said Chris McKay, a senior scientist at NASA.


 John Priscu, a microbiologist at Montana State University, says that liquid water may be the missing ingredient for life on Mars. “We can show that there’s enough energy to drive chemotrophic life—life that doesn’t need sun, but lives on chemistry,” he said. “There’s enough energy, but the problem we ran into is we didn’t have a hydraulic system to keep it going.”



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 Not everyone is convinced, however. A NASA spacecraft with the same mission and similar technology hasn’t detected the body of water, suggesting that it may be transient and not the permanent source that life would need to survive.


 “It’s exciting and has super interesting implications if it’s validated,” says Jack Holt, a professor at the University of Arizona’s Lunar and Planetary Laboratory and an expert in the radar technology used to detect the liquid water. But, he cautions, “I’d say it’s not quite the smoking gun.”

<h2>
 Searching for Life
</h2>

 In recent years, planetary scientists and astrobiologists have been scouring the Red Planet for water, one of the main requirements for life as we know it. In their search, they’ve turned to the icy polar regions of the planet, which contain ice caps and CO 2 that may insulate lakes of liquid water underneath. Researchers are keenly interested in such reservoirs since they are reminiscent of Antarctica, where subglacial lakes teeming with microbial life have recently been discovered.

<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/wissard-antarctica-subglacial-lake-whillans-pe.width-990_HEFeQIq.jpg"/>
<figcaption>In Antarctica, scientists handle a core filled with sediments from the bottom of subglacial Lake Whillans.
 
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 Antarctica’s ice sheets were once considered a biological desert, particularly beneath its enormous volumes of ice, said Brent Christner, a microbiologist at the University of Florida. “Now, 30 years later, we know that Antarctica is essentially the largest wetland on the planet, and we view the subglacial environment as an oasis for life,” he said.


 Even if this new discovery is validated, experts are lukewarm about whether the body of water on Mars would be similarly suitable for life.


 “If there is microbial life operating there, it’s operating under conditions that would be at the very limits of what we know life operates under here on Earth,” said Christner.


 The location and depth of the finding suggests significantly harsher conditions than in Antarctica. For one, the site is closer to the frigid surface of Mars—just under a mile down versus two and a half miles below the surface for Lake Vosok, Antarctica’s largest known subglacial lake. For water to remain liquid at those temperatures, it would have to be incredibly briny.

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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/don-juan-pond.width-990_QQlouCL.jpg"/>
<figcaption>Don Juan Pond in Antarctica is so salty that it doesn't freeze until the temperature drops below -58˚ F.
 
 </figcaption>
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 “The estimated temperature, which is to be debated to some degree, at the depth at which this water is occurring is said to be 205 K [-90˚ F],” said Vlada Stamenković, a research scientist at NASA’s Jet Propulsion Laboratory. “If that were to be liquid water, it would be only feasible if there will be large concentrations of salts within it.”


 And high levels of salt and low temperatures do not usually bode well for microbial life. Antarctica has salty lakes, including Don Juan Pond, which is 18-times saltier than seawater, Priscu said. But in the two decades he’s spent studying it, he hasn’t been able to coax life from it. “I see cells in it, but it’s so briny that the cells—I can’t get them to metabolize,
 
 ”
 
 he said, referring to the chemical processes that all organisms undertake to survive.

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<h2>
 Scouring the Poles
</h2>

 To detect liquid water in the polar regions of Mars, researchers needed to be able to remotely penetrate sometimes miles-thick layers of ice.


 To do so, the team gathered data using a sophisticated radar sensor known as MARSIS aboard the
 
 Mars Express
 
 spacecraft. It took them three and a half years from May 2012 to December 2015—to acquire 29 radar profiles. That’s because the radar works best at night and when it’s within 500 miles of the planet’s surface. But the spacecraft’s eccentric orbit oscillates between distances of 220 miles and 6,200 miles from the Martian topography, giving the team relatively brief periods of time to probe beneath the ice.


 But in those 29 profiles, they found what they say are clear evidence of a stable body of water beneath Mars’ southern polar ice cap. And finding liquid water beneath the surface of Mars, specifically under ice sheets, is exactly what scientists and engineers had hoped MARSIS would do.


 The MARSIS instrument consists of a radar sounder coupled with a 40-foot antenna that sends and receive radar pulses that both bounce off the planet’s surface and penetrate up to three miles underground. It’s similar to other ground-penetrating radars used here on Earth to explore beneath the ice sheets of Greenland and Antarctica.


 Ground-penetrating radar works by measuring what’s known as permittivity, which describes the electrical properties of a material through which radar travels. Certain materials, like dry rocks or CO 2 , have low permittivity while others, like liquid water, produce high values. That’s because polarized materials like water—which has a positive charge on the hydrogen side and a negative charge on the oxygen side—change two parameters of each radar pulse, the amount that is reflected and the speed at which radar waves move through the material. For example, a radar wave that travels through rock will reflect the penetrating pulses back to the antenna more quickly than those that travel through water. The antenna on the spacecraft receives the radar waves returned by the rock before the pulse returned by the water. That difference in time gives scientists a clue about what type of matter the radar encountered.

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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/marssouthpole-01.width-990_TWhHfIB.png"/>
<figcaption>The liquid water is locked beneath nearly a mile of ice.
 
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 Mars Express
 
 scientists Roberto Orosei and his team found a 12.5 mile patch of Mars with high permittivity—so high that the numbers like that are almost always associated with liquid water, including lakes lurking under glaciers in Greenland and Antarctica. The data also ruled out liquid CO 2 , which is not polarized like water and thus has low permittivity.


 The
 
 Mars Express
 
 hasn’t been alone in its quest. The NASA
 
 Mars Reconnaissance Orbiter
 
 also has been pinging the Martian surface with radar waves looking for subsurface water. Its radar instrument, known as SHARAD, has not detected the bright batch of permittivity found by MARSIS.


 However, the SHARAD technology varies slightly from the MARSIS onboard the
 
 Mars Express
 
 . “The main difference between the two radars is the wavelength,” Holt said. MARSIS uses a wavelength that is over 300 feet and can penetrate deeper, whereas SHARAD’s is 50 feet and scours closer to the surface in more detail.


 Orosei doesn’t think that SHARAD can go deep enough to pick up the water, but Holt disagreed. “If there’s really liquid water at the base, it should be showing up in SHARAD,” Holt said.

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 A third eye in the Martian sky could clear up this disagreement. “The Chinese mission to Mars that will be launched in 2020 carries a radar sounder that will transmit at frequencies that are intermediate betwee those of MARSIS and SHARAD,” Orosei said. “Perhaps this experiment will be able to complement MARSIS observations and continue them after the end of the
 
 Mars Express
 
 mission.”


 Ultimately, confirming the findings, and detecting other sources for liquid water on Mars, may mean moving beyond radar technology, which is limited to detecting large quantities of water close to the surface.


 “Even with those limitations, we’ve now found some good evidence that there might be liquid water in the Martian subsurface” Stamenkovic said. “However, that also indicates that there might be much more liquid water in the Martian subsurface in other regions which we cannot detect easily with MARSIS and SHARAD.”


 Physically sampling the water would answer many outstanding questions. Drilling down to the reservoir would be a straightforward solution, but the technical challenges of drilling miles deep on a foreign planet are daunting.


 For example, to bore into the ice in Antarctica to reach the life below, Priscu said he had to truck in a million pounds of equipment and fuel. Sending such a payload to Mars would be prohibitively expensive.


 Still, those challenges don’t appear to discourage some scientists. “This is very big news for astrobiology on Mars,” said NASA’s McKay. “Drill, baby, drill!”



 Updated July 27, 2018: Added comment from Roberto Orosei.
 


 Image credits: NASA, U.S. Antarctic Program,
 <a href="https://www.flickr.com/photos/pierreroudier/24758281740/">
 Pierre Roudier/Flickr (CC BY)
 </a>
 , NASA JPL

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