Category Archives: Datelines

Credit: Daniel Romero

Wild bees: Lone rangers

In a green field outside Madrid, at the foot of the snow-covered Guadarrama mountain range, lies a sun-faded snail shell. Its opening sealed with a cap of dried mud, the shell contains the larva of a wild, solitary bee, together with its first meal of bee bread — a mixture of pollen and nectar. Entomology graduate student Daniel Romero picks up the shell and, concluding that it contains the nest of a mason bee, stores it in a clear plastic tube, labels the red cap with a marker, and closes it.

Back at the Complutense University of Madrid, Romero sets ten tubes of the nesting bees he collected on his professor’s desk. They are just a fraction of the hundreds of samples that he and his colleagues will gather during a four-year Spanish government-funded study of how artificial chemicals are affecting the biodiversity of wild pollinators and their immune and reproductive systems. In the warmth of the office, some of the young adults twitch and scratch at their now-crumbly mud doors. Researchers watch the young adult bees slowly emerge into their new world. When the air cools and the humans leave the room, the bees return to their pollen pillows. Unlike honeybees, solitary bees buzz to their own drum. Continue reading

Credit: Ian Joughin, CC BY-NC-SA 3.0

Building a Better Glacial Speedometer

Greenland is the land of escaping lakes. In the summer, when soot lands on the ice sheet’s snowy surface and the Sun begins to melt the snow, bright blue lakes form on top of the ice. Just as on land, the water seeks a way down.

Sometimes, instead of carving surface channels, water trickles into the ice sheet through crevasses and vertical shafts called moulins. In the most dramatic cases, a lake can burst through a kilometer-thick ice sheet and rush to the bottom of the glacier in a forceful waterfall. There, under high pressure, water may help the glacier glide a little faster over the rock below.

Just how fast, however, is the subject of an ongoing debate.

More Ice Sheet Lakes, Farther Inland

Geoscientist Kate Briggs of the University of Leeds predicted that such lakes will advance from around 50 to more than 100 kilometers inland on Greenland over the next few decades. She presented evidence for this, based on a study she and her colleagues published earlier this year in Nature Climate Change, during a session at the 2015 European Geosciences Union (EGU) meeting in Vienna, Austria.

If such lakes begin to cover more of the Greenland ice sheet, they could play a growing role in the speed with which it moves, Briggs said.

However, there may be natural brakes built into the system. Physical geographer Jonathan Bamber of the University of Bristol commented during the session that lakes forming on the even thicker ice sheet in the middle of Greenland may not be able to escape all the way to the rock bed below the glacier. The deepest ice is under even more pressure and may resist the hydraulic fracturing that enables surface lakes to break through the ice sheet closer to Greenland’s edge.

Briggs and her colleagues assumed in their model that the water did eventually reach the rock bed and that the additional pressure helped it speed up the ice sheet’s motion. Nonetheless, the net effect of how glacial lakes affect ice flow is “still very much an open question,” Briggs said.

Many Methods, Many Answers

Other scientists installed GPS sensors for short periods deep inside the ice sheet to examine how it moves. They found a caterpillar-like movement in fits and starts, according to research reported earlier this year in the Journal of Geophysical Research: Earth Surface.

It is useful information, but generalizing any local observation about the ice sheet is difficult: Greenland spans 18° of latitude and hosts differing microclimates, and its ice sheet encounters chaotic mountains and sea conditions at its edge. The ice sheet’s interaction with the Earth’s climate is complex, session speakers noted.

Still, tracking its speed is a good place to start, explained ice sheet researcher Twila Moon of the University of Colorado Boulder. “Understanding ice velocity is fundamental to understanding how much ice we’re going to lose,” she told Eos.

During the same EGU session as Briggs’s talk, Moon presented preliminary data from the Landsat 8 series. Some of Moon’s previous work shows that the ice sheet’s velocity changes over the course of the seasons and varies by location. Landsat 8 offers more frequent sampling than previous satellite ice sheet mapping: up to every 16 days. That means she will be able to create maps of the ice sheet’s speed with unprecedented time coverage.

“Her data will add a lot,” said applied mathematician Ian Hewitt of the University of Oxford in the United Kingdom. Hewitt creates computational models of how water, glaciers, and the rock bed interact, as seen in this video:

Perhaps, over the course of the season, Hewitt explained, water carves out channels below the ice sheet, and over time, more of the glacier’s weight settles onto the rock bed between the channels. That might explain why researchers have detected both speedups and slowdowns of the ice sheet after surface lake disappearances. The new density of time sampling will enable him and other modelers to put better limits on their models.

More Data, More Modelling

Briggs and others also examine the ice sheet’s topography using radar from CryoSat-2. She presented some preliminary data on ice sheet thickness during her talk, including more evidence that some of the Greenland ice sheet is thinning in ways not captured by existing regional climate models. Similar to the GPS and optical data, the radar data raise more questions.

It is tempting to argue that the growing density of aerial coverage could mean there is less need for slow, expensive GPS surveys, Moon told Eos. However, some of the finer movement, as shown by the GPS surveys, occurs on time scales too short for satellites to reliably detect.

“We would need subdaily resolution to capture the sudden fits and starts,” Hewitt told Eos. “We won’t get that from satellites.” Instead, it may take a lively combination of more on-the-ground instrumentation, more remote sensing, and more modeling to see into the future of Greenland’s ice sheet and its disappearing lakes.

Hewitt explained, “To really work out what’s going on, we’ll have to integrate subglacial processes into those models and then run them long term.”

First published by Eos: [html] [pdf].


How Nicaraguan Villagers Built Their Own Electric Grid

On a dirt road high in Nicaragua’s northern mountains, a small knot of men and two precocious young boys uncoil electrical cable from the back of a pickup truck. Other workers swing machetes at overhanging tree branches. Along the cleared shoulder of the road, another crew tightens a cable on a freshly planted utility pole.

Verdant coffee plantations line the steep road, punctuated by wooden shacks where pigs orbit stakes in the mud. Placards on outhouses proclaim the names of aid organizations. Cinder-block evangelical churches mark even the tiniest clusters of homes.

This extension of the power grid will serve about 30 families in the San Ramón valley, about 200 kilometers northeast of Managua. “We’ve always lived in the dark here,” says Salvador Gonzáles, a resident of the valley and one of the men volunteering on the line crew. For him, the arrival of electricity means a refrigerator and a leap in quality of life. “I’ll have my soda cold, some chicken, some meat, a Popsicle,” he says.

Rural electrification swept through the Western Hemisphere decades ago, but Nicaragua missed out: Electricity reaches barely a third of rural Nicaraguans like Gonzáles. The country’s overall electrification rate of around 74 percent puts it ahead of Haiti and behind every other country in the hemisphere.05OLNicElectriccoffeeberries-1429130209663

There is no physical reason for this impoverishment. Nicaragua is wet, windy, mountainous, volcanic, and tropical, meaning it is an excellent candidate for hydroelectric, wind, geothermal, and solar power. Estimates of its geothermal potential alone have put the figure at several thousand megawatts [PDF]; for reference, the country’s entire installed capacity is about 1,410 megawatts.

In recent years, investments in renewable energy projects have soared, thanks to generous tax breaks. But imported oil still accounts for half of the country’s electricity generation.

The government in Managua, under the idiosyncratic rule of Daniel Ortega, the Sandinista who also led the country in the 1980s, has a plan to raise the electrification rate to 85 percent by 2016. But Nicaraguans in and around the San Ramón valley are tired of waiting. With the help of a local nonprofit group, the inhabitants are taking the electrification of their homes into their own hands. The electricity that Gonzáles will soon enjoy comes from a small hydroelectric plant in the nearby town of El Cuá. And that plant is part of a rich legacy that encompasses a small act of war, some stubborn and idealistic engineers, and a rare unity among fierce, independent people.

It’s hard to picture now, but 30 years ago Nicaragua was an international hotbed of revolution and a Cold War proxy battleground between the United States and the Soviet Union. Many Nicaraguans sympathized with the socialist Sandinista National Liberation Front, which came to power in 1979 after toppling the U.S.-backed Somoza family. These tropical northern highlands saw some of the heaviest fighting between U.S.-backed contra guerrillas and Nicaraguan forces. Over the course of the decadelong war, tens of thousands of Nicaraguans died.05OLNicBoceyDam-1429193667784

At the edge of the regional capital of Matagalpa, a road leads to the modest administrative office of the Association of Rural Development Workers—Benjamin Linder (known by its Spanish acronym, ATDER-BL). Benjamin Linder was a young American engineer who sympathized with the Sandinista movement and came to Nicaragua in 1983 to work on engineering projects. The first project he completed was a 100-kilowatt hydroelectric plant near El Cuá.

Hardworking, idealistic, and playful, Linder entertained the locals by riding his unicycle through town while juggling, sometimes dressed as a clown. At the time, El Cuá was a town of 2,000 that lacked electricity, running water, and sanitation. Despite the logistical challenges of operating in a war zone—contra guerrillas mined the road to El Cuá and sprang frequent ambushes—Linder supervised the completion of the El Cuá plant in 1985 and soon began work on another.

Then, on 28 April 1987, contra soldiers attacked and killed Linder and two Nicaraguans named Sergio Hernández and Pablo Rosales as they worked at the site of the new plant near the town of San José de Bocay. Linder, the only American civilian to be killed by the contras, was 27 years old. In 1988, the IEEE Society on Social Implications of Technology posthumously awarded Linder the Carl Barus Award for Outstanding Service in the Public Interest, in recognition of his “courageous and altruistic efforts to create human good by applying his technical abilities.”

Other hands took up Linder’s work. Shortly after he died, his family and friends began raising funds to complete the plant, and Bocay residents volunteered their labor. A colleague of Linder’s named Rebecca Leaf was working at the time for the Nicaraguan Energy Institute in Managua. The MIT-educated engineer gave up her government job to lead the design and construction of the Bocay plant.

At times, progress ground to a halt, hampered by a U.S. trade embargo that limited the availability of parts. Even after the 1990 peace settlements, guerrilla groups continued to threaten the area. Still, Leaf and her team completed the 185-kW hydroelectric plant in 1994, and today the turbines in Bocay and El Cuá continue to generate electricity.

05NicRedBlueTurbines-1429194936550And 21 years later, Leaf is still here. These days, she is the director of ATDER-BL, which she founded after Linder’s death, and she lives in El Cuá, working from the group’s operations office here. Sunlight bathes the blue one-story building, which is set behind a chain-link fence just off the town’s only paved road. Flocks of birds in nearby trees twitter and shriek, and a metallic screech rings out from the adjacent machine shop, one of the first buildings to get electricity. Visitors wander in, clutching electric bills.

Leaf emerges from her office with an armful of maps and spreadsheets that document the association’s work. She speaks quietly despite the din. The Bocay project “left us with partially trained machinists, welders, masons, surveying crew, pipeline installation experts, and electricians,” she recalls. The workers could have returned to their day jobs—farming, cutting hair, maintaining the town’s fleet of Soviet jeeps and American school buses. Leaf, too, could have found work elsewhere.

But people from nearby communities “came looking for us, saying that they had a river and they wanted to have a hydro plant, too,” she explains. And so she began canvassing international donors for funding. The money was there—but for drinking water systems, not hydroelectric plants. And so for several years, the team switched to constructing potable water systems, the basic piping of which wasn’t too different from that of the hydropower plants they’d been building. “That was our bread-and-butter income,” Leaf says.

As word of ATDER-BL’s work spread, the group returned to building hydropower plants, ranging in size from pico-plants that generate just enough juice to charge a car battery and light a school, to microplants of 3 to 8 kW that local farmers can operate themselves, to one plant that’s nearly a megawatt and now powers about 4,000 homes. In total the group, which now has a full-time staff of 40, has installed about 30 small hydroelectric plants throughout the region. It has consulted for Nicaragua’s Ministry of Mines and Energy and the United Nations Development Programme on dozens more.05OLNicElectricElBote-1429195151318

“ATDER-BL’s work has improved the quality of life for thousands of Nicaraguans, from schoolchildren to farmers, with the support and help of local communities,” says Laurie Guevara-Stone of the Rocky Mountain Institute, in Snowmass, Colo., who has worked on renewable energy in Nicaragua and other Central American countries. “Their approach could really serve as a model for rural electrification in other parts of the world.”

Despite its international reputation, ATDER-BL has never lost its local focus. Just as the group had done in El Cuá and Bocay, it still leans heavily on local workers for the construction of each new hydroelectric plant, explains electrical engineer Abner Talen. The association asks each household to provide a volunteer to do the less technical work: branch clearing, pole hoisting, cable laying, concrete pouring. ATDER-BL’s crew does the rest.

“The people have to be willing to work,” Talen says. “They have to take on the project as their own.” Countless other well-meaning development efforts don’t follow that approach—and they fail, he adds. “There are lots of experiences where the population was given everything and then they don’t take care of it like they should.”

One of the smallest of ATDER-BL’s hydropower plants is a 2-kW system owned and operated by a coffee grower named Martín Rivera and his neighbors. His house is nestled on a lush slope surrounded by bushes heavy with red, ripening coffee berries. Several years ago ATDER-BL advised him and his neighbors when they installed their plant. Now the generator hums in a closet-size shed downhill from Rivera’s farm. Upstream, a tiny dam hidden in the thick forest captures the water to drive the small Pelton wheel turbine.05OLNicNewLine-1429195277351

Twenty years ago, Rivera would have never worked with a group like ATDER-BL. He fought on the side of the contras, and during the worst of the fighting, he sent his son Álvaro to the lowlands to study. When the war ended, Rivera returned to farming. And his son, who’d gotten an agricultural engineering degree, came home and began working for ATDER-BL.

Microhydroelectric systems like Rivera’s run at full capacity only when there’s enough rain. At drier times, they generate less power or none at all. But the bigger, newer sites need to operate continuously and sell their excess power to the grid to recoup their up-front cost, says Leaf. The cost of raw materials like copper has soared, and the increasing automation of the plants’ control systems, which rely on more expensive components and software, has also driven up costs.

Ensuring a steady supply of water for its hydropower plants has been a challenge for ATDER-BL, and it has pushed its engineers into an unexpected new sideline: watershed conservation. In this regard, the association’s biggest project to date, located at the foot of a steep rocky stream near the tiny town of El Bote, presented a thorny challenge.

The 930-kW plant was completed in 2008 and financed in part with a US $1.3 million loan from the World Bank and $400,000 from the nonprofit Green Empowerment, based in Portland, Ore. (Green Empowerment, founded by friends and neighbors of Ben Linder’s family, has provided ATDER-BL with technical, organizational, and financial assistance since 1997.)  The El Bote plant now generates about 5.8 gigawatt-hours per year, enough to power around 6,000 homes in the region. And the local community is thriving. “El Bote is a town of only 95 houses,” Leaf says, “but as soon as there was electricity available, they started increasing the years of schooling…and they graduated the first class of high school students about three years ago.”

But even as construction of the power plant got under way in 2002, the surrounding area was rapidly changing—for the worse. On Leaf’s first visit to the Bosawás Biosphere Reserve, northeast of El Bote, she recalls, “It looked like a place for a Tarzan movie, with vines dangling down from the trees along the side of the river and flocks of red parrots flying overhead, the monkeys calling from the trees nearby, throwing things at you.” But at the forest’s edges, she says, “we saw the virgin forest smoldering. It was the slash and burn of poor people needing to establish agriculture.”

Such wholesale land clearing is bad for hydroelectricity. Fields of corn and beans, which the poorest farmers plant because they offer a quick return on investment, are prone to soil erosion. During the rainy season, the sediment washes from deforested farmland, clogs streams, disrupts dams, and hobbles the hydropower generators. And without the shade of trees overhead, streambeds dry up.

Someone had to ensure the region has enough water to feed its hydropower plants, and that person turned out to be Boanerge Rocha Moreno. The agricultural engineer stands at the intersection of two dirt roads, where one-room wooden houses sport rooftop satellite dishes. He wears a Boston Red Sox cap, a spotless white polo shirt, jeans, and rubber boots.

“When I came for the first time to El Bote, this was naked earth. There were no trees,” he says, as he hops into the association’s shiny new Toyota Hilux. The truck dodges puddles and fords streams, and Rocha points to the roadside, which has been planted with a yellow-green grass that helps hold the soil. Growing coffee also helps, he says. Although it takes longer to mature than corn or beans, coffee can grow in the shade of trees that better protect the watershed’s soil. And because coffee sells at higher prices, growers can afford to leave forested patches on their land. ATDER-BL has bought about 800 hectares of forest upstream from the El Bote and Bocay plants and has overseen the planting of thousands of trees.

“We try to inform people that we have to take care of the forest, that the water depends on the forest, and that water is life,” Rocha says.

That message is trickling down to the farmers, who have embraced it with varying degrees of enthusiasm. One of the more passionate is Luís Euxebio Irías Calderón. He farms in a valley so steep that horses move faster than motor vehicles, and he is also the part-time operator of a nearby microhydropower plant. Irías’s smile gleams gold as he offers to sing a song he composed for the plant’s recent inauguration in the Valley of the Olivas.05El Chevo-1429196431830

“The song is kind of raw since we don’t have a guitar,” Irías says, before belting out the ballad: “The engineer Rosales / Hatched the plan / To bring the project / To the Valley of the Olivas.” Midway through, he gets to “Got to plant trees / All over the range / So that tomorrow / We aren’t unprepared.”

The engineer in Irías’s song is Félix Rosales, ATDER-BL’s energetic young project manager and Leaf’s protégé. Standing nearby, Rosales smiles as Irías croons. A graduate of the National University of Engineering in Managua, Rosales talks of the powerful ripples that emanate from electrification projects: The availability of electricity draws skilled workers to the region—high school teachers, doctors, merchants, all of whom have the disposable income to pay more for goods and services.

That is what happened in the mountain towns that ATDER-BL has helped electrify. No longer places from which parents send their children away, these towns are growing, and the people, having endured years of deprivation and violence, are hopeful.

But there is still work to do, Leaf says. Interconnecting El Cuá’s regional power grid to the national grid has posed technical challenges. “The nearest point for the intertie was a decrepit rural circuit of Nicaragua’s northern utility, Disnorte, with patched conductor wires and fissured porcelain insulators,” Leaf says. The line’s unreliable voltage frequently forces the hydro plants’ generators to trip off-line, damaging the generators’ main circuit breakers and the transformers’ power interrupters. At its own expense, ATDER-BL installed a supervisory control and data acquisition (SCADA) system to help manage the problem and get the plants back on line faster after each trip event.

“For Disnorte, it’s just another low-income rural circuit,” says Leaf. “For us, it’s fundamental to everything that we’re doing.”

Meanwhile, in San José de Bocay, the population has been growing by about 8 percent a year. “There’s a big demand for electrical service and basic services,” says José Luís Olivas Flores, whom Leaf recruited to lead Aprodelbo, a nonprofit there that operates the plant and the local grid. “Now we have cellphones, cybercafés, cable TV. We could say the window has opened to the world due to having electricity.” The 185-kW hydro plant that ATDER-BL completed in 1994 can no longer supply the 1,500 homes, farms, small businesses, schools, churches, gas stations, and municipal government office. Now there’s talk of building an 820-kW hydroelectric plant, he says.

ATDER-BL must also contend with federal electricity regulations that allow Disnorte to charge the association retail rates for its electricity but to buy electricity from ATDER-BL at the lower wholesale rates. Nicaragua is in the process of reforming its renewable energy laws, and Leaf and her team are lobbying legislators for a more equitable arrangement.

Leaf may speak softly, but she has helped an entire region to speak for itself. And to sing. Irías laughs as he reaches the end of his song: “And with this I’ll leave / Forgive the bad singing / Got to take care of the project / Which has cost us so much.”

This feature first appeared in IEEE Spectrum Magazine in May 2015: [html] [pdf].

See and hear also the accompanying radio feature for IEEE Spectrum’s partner show, NPR’s Here & Now: [html] [mp3].


Finding Debris Clouds Around Asteroids Headed Our Way

Small spikes in the magnetic field in our solar system may reveal dust and debris, including some on a collision path with Earth, according to a researcher at the European Geosciences Union (EGU) General Assembly in Vienna, Austria.

The solar wind, which consists of charged particles flowing at high speed from the Sun, creates a magnetic field detectable from interplanetary space probes. Planetary scientist Christopher Russell of the University of California in Los Angeles and his colleagues have been examining small wrinkles in that magnetic field called interplanetary field enhancements (IFEs) since the 1980s. At an EGU session on 13 April, Russell presented the latest evidence that it might be possible to use IFEs to detect asteroid-orbiting clouds of dust and rock, including some that threaten Earth.

“The dust is sort of a warning signal. It’s the smoke telling you where the fire is,” he told Eos.

A Focus on Near-Earth Objects

The explosion of a meteor in the sky near the city of Chelyabinsk, Russia, in 2013 focused attention on the need for such signals. The event shook buildings, broke windows, and caused minor injuries, including cuts and sunburns, according to a report in Science.

In response, the U.S. Congress doubled NASA’s near-Earth object (NEO) search budget to roughly $40 million a year. In addition, the private B612 Foundation in Menlo Park, Calif., is also planning its own mission, dubbed Sentinel, to detect more NEOs. The Sentinel team is promoting 30 June 2015 as Asteroid Day, Eos reported late last year.

NASA claims that it has detected and is tracking the majority of NEOs larger than 1 kilometer in size. In addition, it aims to detect 90% of objects down to 140 meters. Objects smaller than that are probably much more common than earlier estimates, according to a slew of new studies last year. The studies indicate that these small NEOs can still cause major damage.

Seeing into the Shadows

Today’s detection efforts rely on radar and optical telescopes. However, optical methods depend on light reflected from very dark objects, and for radar and optical instruments the smaller targets are more difficult to detect.

Russell pointed out during his talk that known NEOs may be co-orbited by debris large enough to cause damage on Earth even if the host objects miss Earth. For example, one estimate put the Chelyabinsk meteor at only 17 meters. An object that size could be difficult to detect via conventional methods if it were hiding in the shadow of a much larger asteroid.

However, because such objects are likely the result of recent collisions, Russell says they are likely to be accompanied by smaller debris and fine dust. This dust may be the key to identifying these small objects co-orbiting with NEOs.

A New Method

Russell argued during his presentation that nanoscale particles from such collisions pick up charges and interact in a detectable way with the solar wind. Earlier this year his team published a paper in Geophysical Research Letters that used magnetometer data from five spacecraft to document momentum transfer from the solar wind to a dust cloud. The multiple perspectives from all those spacecraft made it possible to triangulate the location of the IFEs and put some boundaries on their three-dimensional structure.

At the EGU meeting, Russell reported that the team has associated two specific IFEs with two different objects: asteroid 2201 Oljato and the potentially hazardous asteroid 138175. Asteroid 2201 Oljato does not threaten Earth yet, but asteroid 138175 is on NASA’s watch list.

“We want to quantify the size of the cloud of dust,” Russell says. Getting a handle on the dust cloud size will help researchers predict the mass and distribution of matter within and surrounding NEOs. That could help guide targeted observations with higher-resolution optical telescopes to determine whether the dust cloud is hosting any potentially hazardous co-orbiting objects, Russell explained.

If the researchers can establish the relationship between the strength of magnetic disturbances and dust cloud size, the magnetometer data already pouring back from many interplanetary missions could be a rich source of information for fine-tuning Earth’s planetary defense.

More Perspectives on IFEs Link to Asteroids

Geraint H. Jones of Imperial College London in the United Kingdom has also examined IFEs in data from the Ulysses spacecraft. In 2003, he and colleagues reported in Icarus that IFEs trailed comets, not asteroids. The charges that modified the solar wind’s magnetic field probably came from ions the comet emitted, Jones says.

If IFEs only trail comets–which are larger, easier to detect, and cross Earth’s path less frequently than asteroids–they may be less useful for planetary defense. However, in the case that Russell and colleagues reported, “charged dust essentially behaves like a very, very heavy ion,” Jones told Eos.

Jones said Russell’s study with “the multiple points of view from five spacecraft: that’s made a big difference. It does appear that dust has an effect on the solar wind and it’s, I think, larger than people would have expected otherwise.” That said, he says he would next like to see a model of the physics of asteroid impacts, dust clouds, and IFEs that predicts the observations.

Russell says he wants to obtain multiple detections of an IFE associated with an asteroid to conclude that the signal is coming from dust activity and to repeat the observation for multiple objects. He says the team is now selecting likely targets for observation on the basis of their paths and orbital periods. Then they will conduct simulations of how such debris clouds form around NEOs in the first place.

The method is also limited by the fact that detecting IFEs is possible only when the object passes between the Sun and a space-based magnetometer. Because most asteroids orbit beyond Mars, surveying them would require very far-flung spacecraft.

However, if Russell’s team can make a convincing link between IFEs and the halos of debris around NEOs, the next logical step, Russell says, is “just going down the list of asteroids” to see which known NEOs have potentially dangerous orbiting debris clouds.

First published by the  American Geophysical Union’s Eos: [html] [pdf].