Off a gravel road at the edge of a college campus — next door to the town’s holding pen for stray dogs — is a busy test site for the newest technologies in drinking water treatment.

In the large shed-turned-laboratory, University of Massachusetts Amherst engineer David Reckhow has started a movement. More people want to use his lab to test new water treatment technologies than the building has space for.

The lab is a revitalization success story. In the 1970s, when the Clean Water Act put new restrictions on water pollution, the diminutive grey building in Amherst, Mass. was a place to test those pollution-control measures. But funding was fickle, and over the years, the building fell into disrepair. In 2015, Reckhow brought the site back to life. He and a team of researchers cleaned out the junk, whacked the weeds that engulfed the building and installed hundreds of thousands of dollars worth of monitoring equipment, much of it donated or bought secondhand.

“We recognized that there’s a lot of need for drinking water technology,” Reckhow says. Researchers, students and start-up companies all want access to test ways to disinfect drinking water, filter out contaminants or detect water-quality slipups. On a Monday afternoon in October, the lab is busy. Students crunch data around a big table in the main room. Small-scale tests of technology that uses electrochemistry to clean water chug along, hooked up to monitors that track water quality. On a lab bench sits a graduate student’s low-cost replica of an expensive piece of monitoring equipment. The device alerts water treatment plants when the by-products of disinfection chemicals in a water supply are reaching dangerous levels. In an attached garage, two startup companies are running larger-scale tests of new kinds of membranes that filter out contaminants.
Parked behind the shed is the almost-ready-to-roll newcomer. Starting in 2019, the Mobile Water Innovation Laboratory will take promising new and affordable technologies to local communities for testing. That’s important, says Reckhow, because there’s so much variety in the quality of water that comes into drinking water treatment plants. On-site testing is the only way to know whether a new approach is effective, he says, especially for newer technologies without long-term track records.

The facility’s popularity reflects a persistent concern in the United States: how to ensure affordable access to clean, safe drinking water. Although U.S. drinking water is heavily regulated and pretty clean overall, recent high-profile contamination cases, such as the 2014 lead crisis in Flint, Mich. (SN: 3/19/16, p. 8), have exposed weaknesses in the system and shaken people’s trust in their tap water.
Tapped out
In 2013 and 2014, 42 drinking water–associated outbreaks resulted in more than 1,000 illnesses and 13 deaths, based on reports to the U.S. Centers for Disease Control and Prevention. The top culprits were Legionella bacteria and some form of chemical, toxin or parasite, according to data published in November 2017.

Those numbers tell only part of the story, however. Many of the contaminants that the U.S. Environmental Protection Agency regulates through the 1974 Safe Drinking Water Act cause problems only when exposure happens over time; the effects of contaminants like lead don’t appear immediately after exposure. Records of EPA rule violations note that in 2015, 21 million people were served by drinking water systems that didn’t meet standards, researchers reported in a February study in the Proceedings of the National Academy of Sciences. That report tracked trends in drinking water violations from 1982 to 2015.
Current technology can remove most contaminants, says David Sedlak, an environmental engineer at the University of California, Berkeley. Those include microbes, arsenic, nitrates and lead. “And then there are some that are very difficult to degrade or transform,” such as industrial chemicals called PFAS.

Smaller communities, especially, can’t always afford top-of-the-line equipment or infrastructure overhauls to, for example, replace lead pipes. So Reckhow’s facility is testing approaches to help communities address water-quality issues in affordable ways.
Some researchers are adding technologies to deal with new, potentially harmful contaminants. Others are designing approaches that work with existing water infrastructure or clean up contaminants at their source.

How is your water treated?
A typical drinking water treatment plant sends water through a series of steps.

First, coagulants are added to the water. These chemicals clump together sediments, which can cloud water or make it taste funny, so they are bigger and easier to remove. A gentle shaking or spinning of the water, called flocculation, helps those clumps form (1). Next, the water flows into big tanks to sit for a while so the sediments can fall to the bottom (2). The cleaner water then moves through membranes that filter out smaller contaminants (3). Disinfection, via chemicals or ultraviolet light, kills harmful bacteria and viruses (4). Then the water is ready for distribution (5).
There’s a lot of room for variation within that basic water treatment process. Chemicals added at different stages can trigger reactions that break down chunky, toxic organic molecules into less harmful bits. Ion-exchange systems that separate contaminants by their electric charge can remove ions like magnesium or calcium that make water “hard,” as well as heavy metals, such as lead and arsenic, and nitrates from fertilizer runoff. Cities mix and match these strategies, adjusting chemicals and prioritizing treatment components, based on the precise chemical qualities of the local water supply.

Some water utilities are streamlining the treatment process by installing technologies like reverse osmosis, which removes nearly everything from the water by forcing the water molecules through a selectively permeable membrane with extremely tiny holes. Reverse osmosis can replace a number of steps in the water treatment process or reduce the number of chemicals added to water. But it’s expensive to install and operate, keeping it out of reach for many cities.

Fourteen percent of U.S. residents get water from wells and other private sources that aren’t regulated by the Safe Drinking Water Act. These people face the same contamination challenges as municipal water systems, but without the regulatory oversight, community support or funding.

“When it comes to lead in private wells … you’re on your own. Nobody is going to help you,” says Marc Edwards, the Virginia Tech engineer who helped uncover the Flint water crisis. Edwards and Virginia Tech colleague Kelsey Pieper collected water-quality data from over 2,000 wells across Virginia in 2012 and 2013. Some were fine, but others had lead levels of more than 100 parts per billion. When levels are higher than its 15 ppb threshold, the EPA mandates that cities take steps to control corrosion and notify the public about the contamination. The researchers reported those findings in 2015 in the Journal of Water and Health.

To remove lead and other contaminants, well users often rely on point-of-use treatments. A filter on the tap removes most, but not all, contaminants. Some people spring for costly reverse osmosis systems.
New tech solutions
These three new water-cleaning approaches wouldn’t require costly infrastructure overhauls.

Ferrate to cover many bases
Reckhow’s team at UMass Amherst is testing ferrate, an ion of iron, as a replacement for several water treatment steps. First, ferrate kills bacteria in the water. Next, it breaks down carbon-based chemical contaminants into smaller, less harmful molecules. Finally, it makes ions like manganese less soluble in water so they are easier to filter out, Reckhow and colleagues reported in 2016 in Journal–American Water Association. With its multifaceted effects, ferrate could potentially streamline the drinking water treatment process or reduce the use of chemicals, such as chlorine, that can yield dangerous by-products, says Joseph Goodwill, an environmental engineer at the University of Rhode Island in Kingston.

Ferrate could be a useful disinfectant for smaller drinking water systems that don’t have the infrastructure, expertise or money to implement something like ozone treatment, an approach that uses ozone gas to break down contaminants, Reckhow says.

Early next year, in the maiden voyage of his mobile water treatment lab, Reckhow plans to test the ferrate approach in the small Massachusetts town of Gloucester.
In the 36-foot trailer is a squeaky-clean array of plastic pipes and holding tanks. The setup routes incoming water through the same series of steps — purifying, filtering and disinfecting — that one would find in a standard drinking water treatment plant. With two sets of everything, scientists can run side-by-side experiments, comparing a new technology’s performance against the standard approach. That way researchers can see whether a new technology works better than existing options, says Patrick Wittbold, the UMass Amherst research engineer who headed up the trailer’s design.

Charged membranes
Filtering membranes tend to get clogged with small particles. “That’s been the Achilles’ heel of membrane treatment,” says Brian Chaplin, an engineer at the University of Illinois at Chicago. Unclogging the filter wastes energy and increases costs. Electricity might solve that problem and offer some side benefits, Chaplin suggests.

His team tested an electrochemical membrane made of titanium oxide or titanium dioxide that both filters water and acts as an electrode. Chemical reactions happening on the electrically charged membranes can turn nitrates into nitrogen gas or split water molecules, generating reactive ions that can oxidize contaminants in the water. The reactions also prevent particles from sticking to the membrane. Large carbon-based molecules like benzene become smaller and less harmful.
In lab tests, the membranes effectively filtered and destroyed contaminants, Chaplin says. In one test, a membrane transformed 67 percent of the nitrates in a solution into other molecules. The finished water was below the EPA’s regulatory nitrate limit of 10 parts per million, he and colleagues reported in July in Environmental Science and Technology. Chaplin expects to move the membrane into pilot tests within the next two years.

Obliterate the PFAS
The industrial chemicals known as PFAS present two challenges. Only the larger ones are effectively removed by granular activated carbon, the active material in many household water filters. The smaller PFAS remain in the water, says Christopher Higgins, an environmental engineer at the Colorado School of Mines in Golden. Plus, filtering isn’t enough because the chunky chemicals are hard to break down for safe disposal.

Higgins and colleague Timothy Strathmann, also at the Colorado School of Mines, are working on a process to destroy PFAS. First, a specialized filter with tiny holes grabs the molecules out of the water. Then, sulfite is added to the concentrated mixture of contaminants. When hit with ultraviolet light, the sulfite generates reactive electrons that break down the tough carbon-fluorine bonds in the PFAS molecules. Within 30 minutes, the combination of UV radiation and sulfites almost completely destroyed one type of PFAS, other researchers reported in 2016 in Environmental Science and Technology.

Soon, Higgins and Strathmann will test the process at Peterson Air Force Base in Colorado, one of nearly 200 U.S. sites known to have groundwater contaminated by PFAS. Cleaning up those sites would remove the pollutants from groundwater that may also feed wells or city water systems.

A physicist, a gamer and two editors walk into a bar. No, this isn’t the setup for some joke. After work one night, a few Science News staffers tried out a new board game, Subatomic. This deck-building game combines chemistry and particle physics for an enjoyable — and educational — time.

Subatomic is simple to grasp: Players use quark and photon cards to build protons, neutrons and electrons. With those three particles, players then construct chemical elements to score points. Scientists are the wild cards: Joseph J. Thomson, Maria Goeppert-Mayer, Marie Curie and other Nobel laureates who discovered important things related to the atom provide special abilities or help thwart other players.
The game doesn’t shy away from difficult or unfamiliar concepts. Many players might be unfamiliar with quarks, a group of elementary particles. But after a few rounds, it’s ingrained in your brain that, for example, two up quarks and one down quark create a proton. And Subatomic includes a handy booklet that explains in easy-to-understand terms the science behind the game. The physicist in our group vouched for the game’s accuracy but had one qualm: Subatomic claims that two photons, or particles of light, can create an electron. That’s theoretically possible, but scientists have yet to confirm it in the lab.

The mastermind behind Subatomic is John Coveyou, who has a master’s degree in energy, environmental and chemical engineering. As the founder and CEO of Genius Games
, he has created six other games, including Ion ( SN: 5/30/15, p. 29 ) and Linkage ( SN: 12/27/14, p. 32 ). Next year, he’ll add a periodic table game to the list . Because Science News has reviewed several of his games, we decided to talk with Coveyou about where he gets his inspiration and how he includes real science in his products. The following discussion has been edited for length and clarity.
SN: When did you get interested in science?

Coveyou: My mom was mentally and physically disabled, and my dad was in and out of prison and mental institutions. So early on, things were very different for me. I ended up leaving home when I was in high school, hopscotching around from 12 different homes throughout my junior and senior year. I almost dropped out, but I had a lot of teachers who were amazing mentors. I didn’t know what else to do, so I joined the army. While I was in Iraq, I had a bunch of science textbooks shipped to me, and I read them in my free time. They took me out of the environments I was in and became extremely therapeutic. A lot of the issues we face as a society can be worked on by the next generation having a command of the sciences. So I’m very passionate about teaching people the sciences and helping people find joy in them.

SN: Why did you start creating science games?

Coveyou: I was teaching chemistry at a community college, and I noticed that my students were really intimidated by the chemistry concepts before they even came into the classroom. They really struggled with a lot of the basic terminology. At the same time, I’ve been a board gamer pretty much my whole life. And it kind of hit me like, “Whoa, wait a second. What if I made some games that taught some of the concepts that I’m trying to teach my chemistry students?” So I just took a shot at it. The first couple of games were terrible. I didn’t really know what I was doing, but I kept at it.

SN: How do you test the games?

Coveyou: We first test with other gamers. Once we’re ready to get feedback from the general public, we go to middle school or high school students. Once we test a game with people face-to-face, we will send it across the world to about 100 to 200 different play testers, and those vary from your hard-core gamers to homeschool families to science teachers, who try it in the classroom.

SN: How do you incorporate real science into your games?

Coveyou: I pretty much always start with a science concept in mind and think about how can we create a game that best reflects the science that we want to communicate. For all of our upcoming games, we include a booklet about the science. That document is not created by Genius Games. We have about 20 to 30 Ph.D.s and doctors across the globe who write the content and edit each other. That’s been a real treat to actually show players how the game is accurate. We’ve had so many scientists and teachers who are just astonished that we created something like this that was accurate, but also fun to play.

Voyager 2 has entered interstellar space. The spacecraft slipped out of the huge bubble of particles that encircles the solar system on November 5, becoming the second ever human-made craft to cross the heliosphere, or the boundary between the sun and the stars.

Coming in second place is no mean achievement. Voyager 1 became the first spacecraft to exit the solar system in 2012. But that craft’s plasma instrument stopped working in 1980, leaving scientists without a direct view of the solar wind, hot charged particles constantly streaming from the sun (SN Online: 9/12/13). Voyager 2’s plasma sensors are still working, providing unprecedented views of the space between stars.

“We’ve been waiting with bated breath for the last couple of months for us to be able to see this,” NASA solar physicist Nicola Fox said at a Dec. 10 news conference at the American Geophysical Union meeting in Washington, D.C.

NASA launched the twin Voyager spacecraft in 1977 on a grand tour of the solar system’s planets (SN: 8/19/17, p. 26). After that initial tour was over, both spacecraft continued travelling through the bubble of plasma that originates at the sun.
“When Voyager was launched, we didn’t know how large the bubble was, how long it would take to get [to its edge] and whether the spacecraft could last long enough to get there,” said Voyager project scientist Edward Stone of Caltech.

For most of Voyager 2’s journey, the spacecraft’s Plasma Science Experiment measured the speed, density, temperature, pressure and other properties of the solar wind. But on November 5, the experiment saw a sharp drop in the speed and the number of solar wind particles that hit the detector each second. At the same time, another detector started picking up more high-energy particles called cosmic rays that originate elsewhere in the galaxy.
Those measurements suggest that Voyager 2 has reached the region where the solar wind slams into the colder, denser population of particles that fill the space between stars. Voyager 2 is now a little more than 18 billion kilometers from the sun.

Intriguingly, Voyager 2’s measurements of cosmic rays and magnetic fields — which Voyager 1 could still make when it crossed the boundary — did not exactly match up with Voyager 1’s observations.
“That’s what makes it interesting,” Stone said. The variations are probably from the fact that the two spacecraft exited the heliosphere in different places, and that the sun is at a different part of its 11-year activity cycle than it was in 2012. “We would have been amazed if they had looked the same.”

The Voyagers probably have between five and 10 years left to continue exploring interstellar space, said Voyager project manager Suzanne Dodd from NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

“Both spacecraft are very healthy if you consider them senior citizens,” Dodd said. The biggest concern is how much power they have left and how cold they are — Voyager 2 is currently about 3.6° Celsius, close to the freezing point of its hydrazine fuel. In the near future, the team will have to turn off some of the spacecraft’s instruments to keep the craft operating and sending data back to Earth.

“We do have difficult decisions ahead,” Dodd said. She added that her personal goal is to see the spacecraft last until 2027, for a total of 50 years in space. “That would be fantastic.”

As the asteroid Bennu comes into sharper focus, planetary scientists are seeing signs of water locked up in the asteroid’s rocks, NASA team members announced December 10.

“It’s one of the things we were hoping to find,” team member Amy Simon of NASA’s Goddard Space Flight Center in Greenbelt, Md., said in a news conference at the American Geophysical Union meeting in Washington, D.C. “This is evidence of liquid water in Bennu’s past. This is really big news.”
NASA’s OSIRIS-REx spacecraft just arrived at Bennu on December 3 (SN Online: 12/3/18). Over the next year, the team will search for the perfect spot on the asteroid to grab a handful of dust and return it to Earth. “Very early in the mission, we’ve found out Bennu is going to provide the type of material we want to return,” said principal investigator Dante Lauretta of the University of Arizona in Tucson. “It definitely looks like we’ve gone to the right place.”

OSIRIS-REx’s onboard spectrometers measure the chemical signatures of various minerals based on the wavelengths of light they emit and absorb. The instruments were able to see signs of hydrated minerals on Bennu’s surface about a month before the spacecraft arrived at the asteroid, and the signal has remained strong all over the asteroid’s surface as the spacecraft approached, Simon said. Those minerals can form only in the presence of liquid water, and suggest that Bennu had a hydrothermal system in its past.

Bennu’s surface is also covered in more boulders and craters than the team had expected based on observations of the asteroid taken from Earth. Remote observations led the team to expect a few large boulders, about 10 meters wide. Instead they see hundreds, some of them up to 50 meters wide.

“It’s a little more rugged of an environment,” Lauretta said. But that rough surface can reveal details of Bennu’s internal structure and history.
If Bennu were one solid mass, for instance, a major impact could crack or shatter its entire surface. The fact that it has large craters means it has survived impacts intact. It may be more of a rubble pile loosely held together by its own gravity.
The asteroid’s density supports the rubble pile idea. OSIRIS-REx’s first estimate of Bennu’s density shows it is about 1,200 kilograms per cubic meter, Lauretta said. The average rock is about 3,000 kilograms per cubic meter. The hydrated minerals go some way towards lowering the asteroid’s density, since water is less dense than rock. But up to 40 percent of the asteroid may be full of caves and voids as well, Lauretta said.

Some of the rocks on the surface appear to be fractured in a spindly pattern. “If you drop a dinner plate on the ground, you get a spider web of fractures,” says team member Kevin Walsh of the Southwest Research Institute in Boulder, Colo. “We’re seeing this in some boulders.”

The boulders may have cracked in response to the drastic change in temperatures they experience as the asteroid spins. Studying those fracture patterns in more detail will reveal the properties of the rocks.

The OSIRIS-REx team also needs to know how many boulders of various sizes are strewn across the asteroid’s surface. Any rock larger than about 20 centimeters across would pose a hazard to the spacecraft’s sampling arm, says Keara Burke of the University of Arizona. Burke, an undergraduate engineering student, is heading up a boulder mapping project.
“My primary goal is safety,” she says. “If it looks like a boulder to me, within reasonable guidelines, then I mark it as a boulder. We can’t sample anything if we’re going to crash.”

The team also needs to know where the smallest grains of rock and dust are, as OSIRIS-REx’s sampling arm can pick up grains only about 2 centimeters across. One way to find the small rocks is to measure how well the asteroid’s surface retains heat. Bigger rocks are slower to heat up and slower to cool down, so they’ll radiate heat out into space even on the asteroid’s night side. Smaller grains of dust heat up and cool down much more quickly.

“It’s exactly like a beach,” Walsh says. “During the day it’s scalding hot, but then it’s instantly cold when the sun sets.”

Measurements of the asteroid’s heat storage so far suggest that there are regions with grains as small as 1 or 2 centimeters across, Lauretta said, though it is still too early to be certain.

“I am confident that we’ll find some fine-grained regions,” Lauretta said. Some may be located inside craters. The challenge will be finding an area wide enough that the spacecraft’s navigation system can steer to it accurately.

A new soft, wireless implant may someday help people who suffer from overactive bladder get through the day with fewer bathroom breaks.

The implant harnesses a technique for controlling cells with light, known as optogenetics, to regulate nerve cells in the bladder. In experiments in rats with medication-induced overactive bladders, the device alleviated animals’ frequent need to pee, researchers report online January 2 in Nature.

Although optogenetics has traditionally been used for manipulating brain cells to study how the mind works, the new implant is part of a recent push to use the technique to tame nerve cells throughout the body (SN: 1/30/10, p. 18). Similar optogenetic implants could help treat disease and dysfunction in other organs, too.
“I was very happy to see this,” says Bozhi Tian, a materials scientist at the University of Chicago not involved in the work. An estimated 33 million people in the United States have overactive bladders. One available treatment is an implant that uses electric currents to regulate bladder nerve cells. But those implants “will stimulate a lot of nerves, not just the nerves that control the bladder,” Tian says. That can interfere with the function of neighboring organs, and continuous electrical stimulation can be uncomfortable.

The new optogenetic approach, however, targets specific nerves in only one organ and only when necessary. To control nerve cells with light, researchers injected a harmless virus carrying genetic instructions for bladder nerve cells to produce a light-activated protein called archaerhodopsin 3.0, or Arch. A stretchy sensor wrapped around the bladder tracks the wearer’s urination habits, and the implant wirelessly sends that information to a program on a tablet computer.
If the program detects the user heeding nature’s call at least three times per hour, it tells the implant to turn on a pair of tiny LEDs. The green glow of these micro light-emitting diodes activates the light-sensitive Arch proteins in the bladder’s nerve cells, preventing the cells from sending so many full-bladder alerts to the brain.
John Rogers, a materials scientist and bioengineer at Northwestern University in Evanston, Ill., and colleagues tested their implants by injecting rats with the overactive bladder–causing drug cyclophosphamide. Over the next several hours, the implants successfully detected when rats were passing water too frequently, and lit up green to bring the animals’ urination patterns back to normal.

Shriya Srinivasan, a medical engineer at MIT not involved in the work, is impressed with the short-term effectiveness of the implant. But, she says, longer-term studies may reveal complications with the treatment.

For instance, a patient might develop an immune reaction to the foreign Arch protein, which would cripple the protein’s ability to block signals from bladder nerves to the brain. But if proven safe and effective in the long term, similar optogenetic implants that sense and respond to organ motion may also help treat heart, lung or muscle tissue problems, she says.

Optogenetic implants could also monitor other bodily goings-on, says study coauthor Robert Gereau, a neuroscientist at Washington University in St. Louis. Hormone levels and tissue oxygenation or hydration, for example, could be tracked and used to trigger nerve-altering LEDs for medical treatment, he says.

The results are in: Ultima Thule, the distant Kuiper Belt object that got a close visit from the New Horizons spacecraft on New Year’s Day, looks like two balls stuck together.

“What you are seeing is the first contact binary ever explored by a spacecraft, two separate objects that are now joined together,” principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colo., said January 2 in a news conference held at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

“It’s a snowman, if it’s anything at all,” Stern said. (Twitter was quick to supply another analogy: the rolling BB-8 droid from Star Wars.)

That shape is enough to lend credence to the idea that planetary bodies grow up by the slow clumping of small rocks. Ultima Thule, whose official name is 2014 MU69, is thought to be among the oldest and least-altered objects in the solar system, so knowing how it formed can reveal how planets formed in general (SN Online: 12/18/18).
“Think of New Horizons as a time machine … that has brought us back to the very beginning of solar system history, to a place where we can observe the most primordial building blocks of the planets,” said Jeff Moore of NASA’s Ames Research Center in Moffett Field, Calif., who leads New Horizons’ geology team. “It’s gratifying to see these perfectly formed contact binaries in their native habitat. Our ideas of how these things form seem to be somewhat vindicated by these observations.”

The view from about 28,000 kilometers away shows that MU69 is about 33 kilometers long and has two spherical lobes, one about three times the size of the other. The spheres are connected by a narrow “neck” that appears brighter than much of the rest of the surface.
That could be explained by small grains of surface material rolling downhill to settle in the neck, because small grains tend to reflect more light than large ones, said New Horizons deputy project scientist Cathy Olkin of the Southwest Research Institute. Even the brightest areas reflected only about 13 percent of the sunlight that hit them, though. The darkest reflected just 6 percent, about the same brightness as potting soil.

Measurements also show that MU69 rotates once every 15 hours, give or take one hour. That’s a Goldilocks rotation speed, Olkin said. If it spun too fast, MU69 would break apart; too slow would be hard to explain for such a small body. Fifteen hours is just right.

The lobes’ spherical shape is best explained by collections of small rocks glomming together to form larger rocks, Moore said. The collisions between the rocks happened at extremely slow speeds, so the rocks accreted rather than breaking each other apart. The final collision was between the two spheres, which the team dubbed “Ultima” (the bigger one) and “Thule” (the smaller one).
That collision probably happened at no more than a few kilometers per hour, “the speed at which you might park your car in a parking space,” Moore said. “If you had a collision with another car at those speeds, you may not even bother to fill out the insurance forms.”

New Horizons also picked up MU69’s reddish color. The science team thinks the rusty hue comes from radiation altering exotic ice, frozen material like methane or nitrogen rather than water, although they don’t know exactly what that ice is made of yet.

The spacecraft is still sending data back to Earth, and will continue transmitting details of the flyby for the next 18 months. Even as the New Horizons team members shared the first pictures from the spacecraft’s flyby, data was arriving that will reveal details of MU69’s surface composition.

“The real excitement today is going to be in the composition team room,” Olkin said. “There’s no way to make anything like this type of observation without having a spacecraft there.”

Just a few powerful storms in Antarctica can have an outsized effect on how much snow parts of the southernmost continent get. Those ephemeral storms, preserved in ice cores, might give a skewed view of how quickly the continent’s ice sheet has grown or shrunk over time.

Relatively rare extreme precipitation events are responsible for more than 40 percent of the total annual snowfall across most of the continent — and in some places, as much as 60 percent, researchers report March 22 in Geophysical Research Letters.
Climatologist John Turner of the British Antarctic Survey in Cambridge and his colleagues used regional climate simulations to estimate daily precipitation across the continent from 1979 to 2016. Then, the team zoomed in on 10 locations — representing different climates from the dry interior desert to the often snowy coasts and the open ocean — to determine regional differences in snowfall.

While snowfall amounts vary greatly by location, extreme events packed the biggest wallop along Antarctica’s coasts, especially on the floating ice shelves, the researchers found. For instance, the Amery ice shelf in East Antarctica gets roughly half of its annual precipitation — which typically totals about half a meter of snow — in just 10 days, on average. In 1994, the ice shelf got 44 percent of its entire annual precipitation on a single day in September.

Ice cores aren’t just a window into the past; they are also used to predict the continent’s future in a warming world. So characterizing these coastal regions is crucial for understanding Antarctica’s ice sheet — and its potential future contribution to sea level rise.
Editor’s note: This story was updated April 5, 2019, to correct that the results were reported March 22 (not March 25).

Editor’s note: On April 10, the Event Horizon Telescope collaboration released a picture of the supermassive black hole at the center of galaxy M87. Read the full story here.

We’re about to see the first close-up of a black hole.

The Event Horizon Telescope, a network of eight radio observatories spanning the globe, has set its sights on a pair of behemoths: Sagittarius A*, the supermassive black hole at the Milky Way’s center, and an even more massive black hole 53.5 million light-years away in galaxy M87 (SN Online: 4/5/17).
In April 2017, the observatories teamed up to observe the black holes’ event horizons, the boundary beyond which gravity is so extreme that even light can’t escape (SN: 5/31/14, p. 16). After almost two years of rendering the data, scientists are gearing up to release the first images in April.

Here’s what scientists hope those images can tell us.

What does a black hole really look like?
Black holes live up to their names: The great gravitational beasts emit no light in any part of the electromagnetic spectrum, so they themselves don’t look like much.

But astronomers know the objects are there because of a black hole’s entourage. As a black hole’s gravity pulls in gas and dust, matter settles into an orbiting disk, with atoms jostling one another at extreme speeds. All that activity heats the matter white-hot, so it emits X-rays and other high-energy radiation. The most voraciously feeding black holes in the universe have disks that outshine all the stars in their galaxies (SN Online: 3/16/18).
The EHT’s image of the Milky Way’s Sagittarius A, also called SgrA, is expected to capture the black hole’s shadow on its accompanying disk of bright material. Computer simulations and the laws of gravitational physics give astronomers a pretty good idea of what to expect. Because of the intense gravity near a black hole, the disk’s light will be warped around the event horizon in a ring, so even the material behind the black hole will be visible.
And the image will probably look asymmetrical: Gravity will bend light from the inner part of the disk toward Earth more strongly than the outer part, making one side appear brighter in a lopsided ring.

Does general relativity hold up close to a black hole?
The exact shape of the ring may help break one of the most frustrating stalemates in theoretical physics.

The twin pillars of physics are Einstein’s theory of general relativity, which governs massive and gravitationally rich things like black holes, and quantum mechanics, which governs the weird world of subatomic particles. Each works precisely in its own domain. But they can’t work together.

“General relativity as it is and quantum mechanics as it is are incompatible with each other,” says physicist Lia Medeiros of the University of Arizona in Tucson. “Rock, hard place. Something has to give.” If general relativity buckles at a black hole’s boundary, it may point the way forward for theorists.

Since black holes are the most extreme gravitational environments in the universe, they’re the best environment to crash test theories of gravity. It’s like throwing theories at a wall and seeing whether — or how — they break. If general relativity does hold up, scientists expect that the black hole will have a particular shadow and thus ring shape; if Einstein’s theory of gravity breaks down, a different shadow.

Medeiros and her colleagues ran computer simulations of 12,000 different black hole shadows that could differ from Einstein’s predictions. “If it’s anything different, [alternative theories of gravity] just got a Christmas present,” says Medeiros, who presented the simulation results in January in Seattle at the American Astronomical Society meeting. Even slight deviations from general relativity could create different enough shadows for EHT to probe, allowing astronomers to quantify how different what they see is from what they expect.
Do stellar corpses called pulsars surround the Milky Way’s black hole?
Another way to test general relativity around black holes is to watch how stars careen around them. As light flees the extreme gravity in a black hole’s vicinity, its waves get stretched out, making the light appear redder. This process, called gravitational redshift, is predicted by general relativity and was observed near SgrA* last year (SN: 8/18/18, p. 12). So far, so good for Einstein.

An even better way to do the same test would be with a pulsar, a rapidly spinning stellar corpse that sweeps the sky with a beam of radiation in a regular cadence that makes it appear to pulse (SN: 3/17/18, p. 4). Gravitational redshift would mess up the pulsars’ metronomic pacing, potentially giving a far more precise test of general relativity.

“The dream for most people who are trying to do SgrA* science, in general, is to try to find a pulsar or pulsars orbiting” the black hole, says astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va. “There are a lot of quite interesting and quite deep tests of [general relativity] that pulsars can provide, that EHT [alone] won’t.”

Despite careful searches, no pulsars have been found near enough to SgrA* yet, partly because gas and dust in the galactic center scatters their beams and makes them difficult to spot. But EHT is taking the best look yet at that center in radio wavelengths, so Ransom and colleagues hope it might be able to spot some.

“It’s a fishing expedition, and the chances of catching a whopper are really small,” Ransom says. “But if we do, it’s totally worth it.”
How do some black holes make jets?
Some black holes are ravenous gluttons, pulling in massive amounts of gas and dust, while others are picky eaters. No one knows why. SgrA* seems to be one of the fussy ones, with a surprisingly dim accretion disk despite its 4 million solar mass heft. EHT’s other target, the black hole in galaxy M87, is a voracious eater, weighing in at between about 3.5 billion and 7.22 billion solar masses. And it doesn’t just amass a bright accretion disk. It also launches a bright, fast jet of charged subatomic particles that stretches for about 5,000 light-years.

“It’s a little bit counterintuitive to think a black hole spills out something,” says astrophysicist Thomas Krichbaum of the Max Planck Institute for Radio Astronomy in Bonn, Germany. “Usually people think it only swallows something.”

Many other black holes produce jets that are longer and wider than entire galaxies and can extend billions of light-years from the black hole. “The natural question arises: What is so powerful to launch these jets to such large distances?” Krichbaum says. “Now with the EHT, we can for the first time trace what is happening.”

EHT’s measurements of M87’s black hole will help estimate the strength of its magnetic field, which astronomers think is related to the jet-launching mechanism. And measurements of the jet’s properties when it’s close to the black hole will help determine where the jet originates — in the innermost part of the accretion disk, farther out in the disk or from the black hole itself. Those observations might also reveal whether the jet is launched by something about the black hole itself or by the fast-flowing material in the accretion disk.

Since jets can carry material out of the galactic center and into the regions between galaxies, they can influence how galaxies grow and evolve, and even where stars and planets form (SN: 7/21/18, p. 16).

“It is important to understanding the evolution of galaxies, from the early formation of black holes to the formation of stars and later to the formation of life,” Krichbaum says. “This is a big, big story. We are just contributing with our studies of black hole jets a little bit to the bigger puzzle.”

Editor’s note: This story was updated April 1, 2019, to correct the mass of M87’s black hole; the entire galaxy’s mass is 2.4 trillion solar masses, but the black hole itself weighs in at several billion solar masses. In addition, the black hole simulation is an example of one that uphold’s Einstein’s theory of general relativity, not one that deviates from it.

We live in a sea of neutrinos. Every second, trillions of them pass through our bodies. They come from the sun, nuclear reactors, collisions of cosmic rays hitting Earth’s atmosphere, even the Big Bang. Among fundamental particles, only photons are more numerous. Yet because neutrinos barely interact with matter, they are notoriously difficult to detect.

The existence of the neutrino was first proposed in the 1930s and then verified in the 1950s (SN: 2/13/54). Decades later, much about the neutrino — named in part because it has no electric charge — remains a mystery, including how many varieties of neutrinos exist, how much mass they have, where that mass comes from and whether they have any magnetic properties.
These mysteries are at the heart of Ghost Particle by physicist Alan Chodos and science journalist James Riordon. The book is an informative, easy-to-follow introduction to the perplexing particle. Chodos and Riordon guide readers through how the neutrino was discovered, what we know — and don’t know — about it, and the ongoing and future experiments that (fingers crossed) will provide the answers.

It’s not just neutrino physicists who await those answers. Neutrinos, Riordon says, “are incredibly important both for understanding the universe and our existence in it.” Unmasking the neutrino could be key to unlocking the nature of dark matter, for instance. Or it could clear up the universe’s matter conundrum: The Big Bang should have produced equal amounts of matter and antimatter, the oppositely charged counterparts of electrons, protons and so on. When matter and antimatter come into contact, they annihilate each other. So in theory, the universe today should be empty — yet it’s not (SN: 9/22/22). It’s filled with matter and, for some reason, very little antimatter.

Science News spoke with Riordon, a frequent contributor to the magazine, about these puzzles and how neutrinos could act as a tool to observe the cosmos or even see into our own planet. The following conversation has been edited for length and clarity.

SN: In the first chapter, you list eight unanswered questions about neutrinos. Which is the most pressing to answer?

Riordon: Whether they’re their own antiparticles is probably one of the grandest. The proposal that neutrinos are their own antiparticles is an elegant solution to all sorts of problems, including the existence of this residue of matter we live in. Another one is figuring out how neutrinos fit in the standard model [of particle physics]. It’s one of the most successful theories there is, but it can’t explain the fact that neutrinos have mass.
SN: Why is now a good time to write a book about neutrinos?

Riordon: All of these questions about neutrinos are sort of coming to a head right now — the hints that neutrinos may be their own antiparticles, the issues of neutrinos not quite fitting the standard model, whether there are sterile neutrinos [a hypothetical neutrino that is a candidate for dark matter]. In the next few years, a decade or so, there will be a lot of experiments that will [help answer these questions,] and the resolution either way will be exciting.

SN: Neutrinos could also be used to help scientists observe a range of phenomena. What are some of the most interesting questions neutrinos could help with?

Riordon: There are some observations that simply have to be done with neutrinos, that there are no other technological alternatives for. There’s a problem with using light-based telescopes to look back in history. We have this really amazing James Webb Space Telescope that can see really far back in history. But at some point, when you go far enough back, the universe is basically opaque to light; you can’t see into it. Once we narrow down how to detect and how to measure the cosmic neutrino background [neutrinos that formed less than a second after the Big Bang], it will be a way to look back at the very beginning. Other than with gravitational waves, you can’t see back that far with anything else. So it’ll give us sort of a telescope back to the beginning of the universe.

The other thing is, when a supernova happens, all kinds of really cool stuff happens inside, and you can see it with neutrinos because neutrinos come out immediately in a burst. We call it the “cosmic neutrino bomb,” but you can track the supernova as it’s going along. With light, it takes a while for it to get out [of the stellar explosion]. We’re due for a [nearby] supernova. We haven’t had one since 1987. It was the last visible supernova in the sky and was a boon for research. Now that we have neutrino detectors around the world, this next one is going to be even better [for research], even more exciting.

And if we develop better instrumentation, we could use neutrinos to understand what’s going on in the center of the Earth. There’s no other way that you could probe the center of the Earth. We use seismic waves, but the resolution is really low. So we could resolve a lot of questions about what the planet is made of with neutrinos.

SN: Do you have a favorite “character” in the story of neutrinos?

Riordon: I’m certainly very fond of my grandfather Clyde Cowan [he and Frederick Reines were the first physicists to detect neutrinos]. But Reines is a riveting character. He was poetic. He was a singer. He really was this creative force. I mentioned [in the book] that they put this “SNEWS” sign on their detector for “supernova early warning system,” which sort of echoed the ballistic missile early warning systems at the time [during the Cold War]. That’s so ripe.

For the first time, astronomers have caught a glimpse of shock waves rippling along strands of the cosmic web — the enormous tangle of galaxies, gas and dark matter that fills the observable universe.

Combining hundreds of thousands of radio telescope images revealed the faint glow cast as shock waves send charged particles flying through the magnetic fields that run along the cosmic web. Spotting these shock waves could give astronomers a better look at these large-scale magnetic fields, whose properties and origins are largely mysterious, researchers report in the Feb. 17 Science Advances.
Finally, astronomers “can confirm what so far has only been predicted by simulations — that these shock waves exist,” says astrophysicist Marcus Brüggen of the University of Hamburg in Germany, who was not involved in the new study.

At its grandest scale, our universe looks something like Swiss cheese. Galaxies aren’t distributed evenly through space but rather are clumped together in enormous clusters connected by ropy filaments of dilute gas, galaxies and dark matter and separated by not-quite-empty voids (SN: 10/3/19).

Tugged by gravity, galaxy clusters merge, filaments collide, and gas from the voids falls onto filaments and clusters. In simulations of the cosmic web, all that action consistently sets off enormous shock waves in and along filaments.

Filaments make up most of the cosmic web but are much harder to spot than galaxies (SN: 1/20/14). While scientists have observed shock waves around galaxy clusters before, shocks in filaments “have never been really seen,” says astronomer Reinout van Weeren of Leiden University in the Netherlands, who was not involved in the study. “But they should be basically all around the cosmic web.”

Shock waves around filaments would accelerate charged particles through the magnetic fields that suffuse the cosmic web (SN: 6/6/19). When that happens, the particles emit light at wavelengths that radio telescopes can detect — though the signals are very weak.
A single shock wave in a filament “would look like nothing, it’d look like noise,” says radio astronomer Tessa Vernstrom of the International Centre for Radio Astronomy Research in Crawley, Australia.

Instead of looking for individual shock waves, Vernstrom and her colleagues combined radio images of more than 600,000 pairs of galaxy clusters close enough to be connected by filaments to create a single “stacked” image. This amplified weak signals and revealed that, on average, there is a faint radio glow from the filaments between clusters.

“When you can dig below the noise and still actually get a result — to me, that’s personally exciting,” Vernstrom says.

The faint signal is highly polarized, meaning that the radio waves are mostly aligned with one another. Highly polarized light is unusual in the cosmos, but it is expected from radio light cast by shock waves, van Weeren says. “So that’s really, I think, very good evidence for the fact that the shocks are likely indeed present.”
The discovery goes beyond confirming the predictions of cosmic web simulations. The polarized radio emissions also offer a rare peek at the magnetic fields that permeate the cosmic web, if only indirectly.

“These shocks,” Brüggen says, “are really able to show that there are large-scale magnetic fields that form [something] like a sheath around these filaments.”

He, van Weeren and Vernstrom all note that it’s still an open question how cosmic magnetic fields arose in the first place. The role these fields play in shaping the cosmic web is equally mysterious.

“It’s one of the four fundamental forces of nature, right? Magnetism,” Vernstrom says. “But at least on these large scales, we don’t really know how important it is.”