M87 in 3D: New view of galaxy helps pin down mass of the black hole at its core

Seen from Earth, the giant elliptical galaxy M87 is just a two-dimensional blob, though one that appears perfectly symmetrical and thus a favored target of amateur astronomers.

Yet, a new, highly detailed analysis of the motion of stars around its central supermassive black hole — the first black hole to be imaged by the Event Horizon Telescope (EHT) in 2019 — reveals that it's not as perfect as it looks.

In fact, M87 is highly asymmetrical, like a russet potato. The galaxy's shortest axis is about three-fourths (72.2%) the length of its long axis, while the intermediate axis is about seven-eighths (84.5%) that of the long axis.

Knowing this, University of California, Berkeley, astronomers were able to determine the mass of the supermassive black hole at the galaxy's core to a high precision, estimating it at 5.37 billion times the mass of the sun. By comparison, our own Milky Way has at its center a massive black hole only 4 million times the mass of the sun.

They also were able to measure the rotation of the galaxy, which is a relatively sedate 25 kilometers per second. Interestingly, it is not rotating around any of the galaxy's major axes, but instead about an axis that is 40 degrees away from the long axis of its 2D image as observed by the Hubble Space Telescope.

The stereo reconstruction of the M87 galaxy and the more precise figure for the mass of the central black hole could help astrophysicists learn about a characteristic of the black hole they've had no way to determine before for any black hole: its spin.

"Now that we know the direction of the net rotation of stars in M87 and have an updated mass of the black hole, we can combine this information with the amazing data from the EHT team to constrain the spin," said Chung-Pei Ma, a UC Berkeley professor of astronomy and of physics who led the research. "This may point toward a certain direction and range of spin for the black hole, which would be remarkable. We are working on this.”

Further analyses to determine the true shape of giant elliptical galaxies — the galaxies with the largest black holes at their cores — will help astronomers understand better how large galaxies and large black holes form and could help astronomers better interpret gravitational wave signals. Ma leads a long-term study of supermassive black holes that is dubbed MASSIVE.

The results were published online March 15 in The Astrophysical Journal Letters (ApJ Letters).

Determining a galaxy's 3D shape

While spiral galaxies tend to be small, rotate quickly and have a well-recognized pancake shape, giant elliptical galaxies rotate slowly and have a blobby appearance, their 3D shape difficult to discern. Like M87, the largest galaxy in the massive Virgo Cluster of galaxies, giant elliptical galaxies have grown from the merger of many other galaxies. That's likely the reason M87's central black hole is so large — it assimilated the central black holes of all the galaxies it swallowed. In all, the galaxy contains about 100 billion stars, 10 times larger than the Milky Way.

Ma, UC Berkeley graduate student and lead author Emily Liepold, and Jonelle Walsh at Texas A&M University in College Station were able to determine the 3D shape of M87 thanks to a relatively new precision instrument mounted on the Keck II Telescope, one of the twin 10-meter Keck telescopes atop Mauna Kea, a volcano in Hawai'i. Called the Keck Cosmic Web Imager (KCWI), the integral field spectrometer allowed Ma and her team to measure the spectra of stars in the center of the galaxy.

They pointed the telescope at 62 adjacent locations in the galaxy, completely covering a region about 70,000 light-years across, and recorded the spectra of stars within that region. The observations span the central region — about 3,000 light-years across — where gravity is largely dominated by the supermassive black hole, as well as the outer part dominated by dark matter. Though the telescope cannot resolve individual stars — M87 lies about 53 million light- years from Earth — the spectra can reveal the range of velocities within each pixel of each image, enough information to calculate the gravitational mass they're orbiting.

"It's sort of like looking at a swarm of 100 billion bees that are going around in their own happy orbits," said Ma, the Judy Chandler Webb Professor in the Physical Sciences. "Though we are looking at them from a distance and can’t discern individual bees, we are getting very detailed information about their collective velocities. It's really the superb sensitivity of this spectrograph that allowed us to map out M87 so comprehensively."

This is the first time KCWI has been used to reconstruct the geometry of a distant galaxy, and M87 is one of only a handful of giant elliptical galaxies whose 3D structure has been determined. Ma’s team had previously determined the 3D structure of two other giant elliptical galaxies, NGC 1453 and NGC 2693, both harboring smaller black holes than M87.

The researchers took the data obtained during four nights of Keck observations between 2020 and 2022, along with earlier photometric data for M87 from NASA's Hubble Space Telescope, and compared them to computer model predictions of how stars move around the center of a triaxial galaxy. The best fit to the data — axial ratios of 1 to 0.84 to 0.72 — then allowed them to calculate the black hole mass.

"The Keck data are so good that we can measure the intrinsic shape of M87 along with the black hole at the same time," Ma said. "We made the first measurement of the actual 3D shape of the galaxy. And since we allowed the swarm of bees to have a more general shape than just a sphere or disk, we have a more robust dynamical measurement of the mass of the central black hole that is governing the bees’ orbiting velocities."

The authors dedicated their manuscript to the late astronomer Wallace "Wal" Sargent, who first suggested that a supermassive black hole lurked at the center of M87 and calculated its mass to be about 5 billion solar masses.

"His number is a twiddle with our error bars, which is very interesting to see after decades of work," said Ma, who credits Sargent with being a mentor when she was a postdoctoral fellow at the California Institute of Technology.

The previous estimate of the mass of the supermassive black hole in M87, published in 2011, was based on a similar analysis of the dynamical movement of stars around the black hole, though that study assumed the galaxy was axisymmetric. The number, 6.14 billion solar masses, is within error bars of the new, more precise estimate. When imaging the black hole four years ago, the EHT scientists estimated the black hole mass to be 6.5 billion solar masses, 21% higher than the new number.

Interestingly, the dark matter within the volume of the galaxy they analyzed is much higher than that of the black hole — about 388 billion solar masses, or 67% of the entire mass of M87. Though the identity of dark matter is still a mystery, it makes up about 85% of the mass of the universe.

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James Webb Space Telescope images challenge theories of how universe evolved

The James Webb Space Telescope (JWST) appears to be finding multiple galaxies that grew too massive too soon after the Big Bang, if the standard model of cosmology is to be believed.

In a study published in Nature Astronomy, Mike Boylan-Kolchin, an associate professor of astronomy at The University of Texas at Austin, finds that six of the earliest and most massive galaxy candidates observed by JWST so far stand to contradict the prevailing thinking in cosmology. That's because other researchers estimate that each galaxy is seen from between 500 and 700 million years after the Big Bang, yet measures more than 10 billion times as massive as our sun. One of the galaxies even appears to be more massive than the Milky Way, despite that our own galaxy had billions of more years to form and grow.

"If the masses are right, then we are in uncharted territory," Boylan-Kolchin said. "We'll require something very new about galaxy formation or a modification to cosmology. One of the most extreme possibilities is that the universe was expanding faster shortly after the Big Bang than we predict, which might require new forces and particles."

For galaxies to form so fast at such a size, they also would need to be converting nearly 100% of their available gas into stars.

"We typically see a maximum of 10% of gas converted into stars," Boylan-Kolchin said. "So while 100% conversion of gas into stars is technically right at the edge of what is theoretically possible, it's really the case that this would require something to be very different from what we expect."

For all of the breathless excitement it evokes, JWST has presented astronomers with an unsettling dilemma. If the masses and time since the Big Bang are confirmed for these galaxies, fundamental changes to the reigning model of cosmology -- what's called the dark energy + cold dark matter (ΛCDM) paradigm, which has guided cosmology since the late 1990s -- could be needed. If there are other, faster ways to form galaxies than ΛCDM allows, or if more matter actually was available for forming stars and galaxies in the early universe than was previously understood, astronomers would need to shift their prevailing thinking.

The six galaxies' times and masses are initial estimates and will need follow-up confirmation with spectroscopy -- a method that splits the light into a spectrum and analyzes the brightness of different colors. Such analysis might suggest that central supermassive black holes, which could heat up the surrounding gas, may be making the galaxies brighter so that they look more massive than they really are. Or perhaps the galaxies are actually seen at a time much later than originally estimated due to dust that causes the color of the light from the galaxy to shift redder, giving the illusion of being more lightyears away and, thus, further back in time.

The galaxy data came from the Cosmic Evolution Early Release Science Survey (CEERS), a multi-institution JWST initiative led by UT Austin astronomer Steven Finkelstein.

Another ongoing collaborative JWST project, COSMOS-Web, co-led by UT Austin's Caitlin Casey, may be involved with spectroscopy and shedding more light on the findings to help resolve the dilemma. COSMOS-Web is covering an area roughly 50 times larger than CEERS and is expected to discover thousands of galaxies.

"It will be ideal for discovering the rarest, most massive galaxies at early times, which will tell us how the biggest galaxies and black holes in the early universe arose so quickly," Boylan-Kolchin said.

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New look at climate data shows substantially wetter rain and snow days ahead

A key source of information underpinning the upcoming National Climate Assessment suggests that heavy precipitation days historically experienced once in a century by Americans could in the future be experienced on several occasions in a lifetime.

Scientists at Scripps Institution of Oceanography at UC San Diego and the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) report that extremely intense days of rain or snow will be more frequent by the end of this century than previously thought -- as often as once every 30 or 40 years in the Pacific Northwest and southeastern United States.

The conclusions come from analyzing a 30-terabyte data set that models temperature and precipitation at scales roughly the size of urban ZIP codes: six kilometers (3.9 miles). Researchers developed the data set, called Localized Constructed Analogs Version 2 (LOCA2), to provide climate information that is useful for local planners. In contrast, most of the existing advanced climate models look at regions that range from 50 to 250 kilometers (30 to 400 miles).

"With this data set, we're able to look at the impacts of actual weather pattern changes across the United States at an extremely granular level," said Dan Feldman, staff scientist at Berkeley Lab and the project's principal investigator. "We see that there is a lot more extreme weather that is likely to happen in the future -- and by looking at actual weather patterns, we show that changes in extreme precipitation will actually be more extreme than previously estimated. Land use managers and planners should expect more extremes, but location matters."

The LOCA2 data set updates a similar analysis conducted in 2016 in advance of the Fourth National Climate Assessment (NCA), which was released in 2018 by the U.S. Global Change Research Program. The NCA is intended to assist the U.S. government with planning for, mitigating, and adapting to changes in climate that will affect the country. The Fifth NCA is expected to be issued later this year.

LOCA2 projections cover the lower 48 states of the United States, southern Canada, and northern Mexico. The data set draws on more than 70 years of weather data and incorporates 27 updated climate models from the Coupled Model Intercomparison Project (CMIP6), the latest iteration of an international effort to simulate climate that includes the "coupling" of natural systems such as the ocean and atmosphere to understand how they will act in concert as climate changes.

"We've spent a lot of effort improving the representation of extreme wet days, which is important for understanding both the likelihood of flooding and the availability of water for agricultural, commercial, and residential use," said David Pierce, a scientist at Scripps Oceanography and the developer of LOCA and LOCA2.

The LOCA2 climate projections are available through the end of the century down to the daily level, and for three different greenhouse gas emissions scenarios known as SSPs, or Shared Socioeconomic Pathways. The three scenarios are a medium level of emissions that is slightly less than current levels (SSP 245), medium-high (SSP 370), and high, where emissions greatly increase (SSP 585). The data set is freely available for planners and decision makers to use.

The projection reinforces what climate scientists have long predicted: Future weather events will become more extreme in a warming world. LOCA2 finds that the heaviest days of rain and snowfall across much of North America will likely release 20 to 30 percent more moisture than they do now. Much of the increased precipitation will occur in winter, potentially exacerbating flooding in regions such as the upper Midwest and the west coast.

"The big picture is clear: it's getting warmer and wetter," Feldman said. "This research translates that bigger picture into more practical data for infrastructure and operations planning. With this more detailed look at local impacts, we can help local officials make better-informed decisions, such as how long to make an airport runway, how much resilience to include for constructing buildings or bridges, or where to put crops or culverts."

The improved set of LOCA2 data was created by better identifying and preserving extreme weather events in the past, training models to more accurately reflect extremes in simulations of the future.

"We undertook a Herculean effort of personnel and computer time not just to produce a bunch of numbers, but to produce local projections that are relevant and useful," Feldman said. "We do so by recognizing how heat waves and storms have occurred and will occur at the local level, and projecting those forward."

Seasonal and regional predictions

While the data varies at the local level, researchers found substantial trends across the area covered by LOCA2 at the end of the century.

Across most seasons, a major part of North America will see roughly the same or fewer number of days with precipitation, roughly the same or fewer number of days with light and medium amounts of precipitation, and a large increase in the number of days with the most extreme precipitation (the top 1 percent and 0.1 percent of storms).

"People will be more affected by the really rare and most extreme events, because those are showing the biggest increase," said Pierce, who is the lead author of the paper on extreme precipitation published in the Journal of Hydrometeorology. "The wettest day you would expect to see in five years, or 50 years, or 500 years -- those extreme events are going to be substantially wetter, and that's a really big issue, because it has implications for flooding and run-off."

Southern Canada and most of the United States will see increases in extreme precipitation days that occur primarily in winter. The wettest days of precipitation will increase by 20-30 percent, depending on the emissions scenario and how extreme the storm is.

Arizona, New Mexico, and northern Mexico can expect increases in extreme precipitation days that occur primarily in autumn. The wettest days of precipitation increase by 10-30 percent, depending on which emissions scenarios come to be and how extreme the storms are. While the region becomes drier overall, the number of days with extreme precipitation events still goes up, meaning the precipitation that does come will often do so in larger storms.

"It's quite interesting that you see the same kind of pattern of fewer low- and medium- precipitation days and more extreme precipitation days across pretty much the entire country," Pierce said. Knowing the changing character of precipitation and the frequency of extreme events is useful in two ways, Pierce added. "One is for building new infrastructure in the future, and one is for understanding impacts upon existing facilities already there."

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Apes may have evolved upright stature for leaves, not fruit, in open woodland habitats

Anthropologists have long thought that our ape ancestors evolved an upright torso in order to pick fruit in forests, but new research from the University of Michigan suggests a life in open woodlands and a diet that included leaves drove apes' upright stature.

The finding sheds light on ape origins and pushes back the origin of grassy woodlands from between 7 million and 10 million years ago to 21 million years ago, during the Early Miocene.

Fruit grows on the spindly peripheries of trees. To reach it, large apes need to distribute their weight on branches stemming from the trunk, then reach out with their hands toward their prize. This is much easier if an ape is upright because it can more easily grab onto different branches with its hands and feet. If its back is horizontal, then its hands and feet are generally underneath the body, making it much harder to move outward to the smaller branches of a tree -- especially if the ape is large bodied.

This is how modern day apes reach fruit, and, it's been theorized, that's why apes evolved to be upright, according to U-M researchers Laura MacLatchy and John Kingston.

But new research centered around a 21-million-year-old fossil ape called Morotopithecus and led by MacLatchy suggests this might not be the case. Instead, researchers think early apes ate leaves and lived in a seasonal woodland with a broken canopy and open, grassy areas. The researchers suggest this landscape, instead of fruit in closed canopy forests, drove apes' upright stature.

Their results are published in Science and are bolstered by a companion paper examining these paleo grassy woodland habitats, published in the same issue of the journal.

"The expectation was: We have this ape with an upright back. It must be living in forests and it must be eating fruit. But as more and more bits of information became available, the first surprising thing we found was that the ape was eating leaves. The second surprise was that it was living in woodlands," said MacLatchy, a paleoanthropologist and professor in the U-M Department of Anthropology.

The two papers grew out of a U.S. National Science Foundation-funded collaboration of international paleontologists, collectively known as the Research on Eastern African Catarrhine and Hominoid Evolution project or REACHE, each of whom focus on different aspects of early ape paleoenvironments. The study led by MacLatchy focuses on a 21-million-year-old site called the Moroto site in eastern Uganda.

There, the group, which included U-M researchers William Sanders and Miranda Cosman, examined fossils found in a single stratigraphic layer, including fossils of the oldest, clearly documented ape, Morotopithecus. Also within this layer were fossils of other mammals, ancient soils called paleosols, and tiny silica particles from plants called phytoliths. The researchers used these lines of evidence to recreate the ancient environment of Morotopithecus.

MacLatchy and Kingston discovered that the plants living in this landscape were what's called "water stressed," meaning they lived through seasonal periods of rain and of aridity. This also means that at least part of the year, apes had to rely on something other than fruit to survive. Together, these findings indicate that Morotopithecus lived in an open woodland punctuated by broken canopy forests composed of trees and shrubs.

"These open environments have been invoked to explain human origins, and it was thought that you started to get these more open, seasonal environments between 10 and 7 million years ago," MacLatchy said. "Such an environmental shift is thought to have been selected for terrestrial bipedalism -- our ancestors started striding around on the ground because the trees were further apart.

"Now that we've shown that such environments were present at least 10 million years before bipedalism evolved, we need to really rethink human origins, too."

The first clue that these ancient apes were eating leaves was in the apes' molars. The molars were very "cresty": they were craggy, with peaks and valleys. Molars like this are used for tearing fibrous leaves apart, while molars used for eating fruit are typically more rounded, MacLatchy said.

The researchers also examined the apes' dental enamel, as well as the dental enamel of other mammals found in the same stratigraphic layer. They found that isotopic ratios -- the abundance of two isotopes of the same element -- in their dental enamel showed that the apes and other mammals had been eating water stressed C3 plants that are more common in open woodland or grassy woodland environments today. C3 plants are primarily woody shrubs and trees while C4 plants are arid-adapted grasses.

"Putting together the locomotion, the diet and the environment, we basically discovered a new model for ape origins," MacLatchy said. "In anthropology, we care a lot about ape evolution because humans are closely related to apes and features like lower back stability represent an arboreal adaptation that may have ultimately given rise to bipedal humans."

Early Miocene C4 grasses and open woodlands

Previously, researchers believed equatorial Africa during the Early Miocene was thickly carpeted with forest, and that open seasonal woodlands and grasslands evolved only between 7 million and 10 million years ago.

But the second paper uses a set of environmental proxies to reconstruct the vegetation structure from nine fossil ape sites across Africa, including the Moroto site, during the Early Miocene. These proxies revealed that C4 grasses were "everywhere" during that time period, said Kingston, a biological anthropologist and associate professor in the U-M Department of Anthropology.

"This paper looks at all these sites, pulls all this data together, and says, 'Look, no matter how you evaluate the data, there's no way you can escape the fact that all these proxies are converging on the same place -- namely, that these environments are open, and they're open with C4 grasses," he said.

"For the first time, we're showing that these grasses are widespread, and it's this general context of open seasonal woodland ecosystems that were integral in shaping the evolution of different mammalian lineages, including and especially in our case, how different ape lineages evolved."

The nine sites are scattered across eastern equatorial Africa, enough to develop a "regional picture" of what the sites' landscapes looked like in the Early Miocene, Kingston said. During this time, the East African Rift was forming. Earth was pulling apart. As a result, the entire region was uplifted, causing huge variation in topography, and therefore, regional climate and vegetation.

"There's mountains and volcanoes, there's cliffs and escarpments and valleys," Kingston said. "The landscape is just physically highly variable, and that, no doubt, is related to the vegetation heterogeneity."

To reconstruct the paleoenvironment at each location, the researchers used carbon isotope analyses of ancient soil organic matter, plant wax biomarkers and phytoliths found at each site. The carbon isotope analyses revealed that a wide range of plants lived in the grasslands, ranging from those that comprise closed canopy to wooded grasslands.

The wax biomarkers -- left over from the waxy material that protects leaves -- also indicate a large variety of shrubs and trees as well as grasses. Phytoliths -- microscopic biosilica bodies that give plants their structure as well as a defense against being eaten -- can tell the researchers the proportion of C4 grasses at a given site and provide further evidence for abundant C4 grasses.

After using these proxies to rebuild the paleoenvironments at these nine sites, the researchers found that C4 grasses were abundant across eastern equatorial Africa, and were a key part of the landscape's heterogeneous habitats. Their data also pushes back the oldest evidence of C4 grass-dominated habitats in Africa and globally by more than 10 million years.

"The findings have transformed what we thought we knew about early apes, and the origin for where, when and why they navigate through the trees and on the ground in multiple different ways," said Robin Bernstein, program director for biological anthropology at the National Science Foundation.

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Humans need Earth-like ecosystem for deep-space living

Can humans endure long-term living in deep space? The answer is a lukewarm maybe, according to a new theory describing the complexity of maintaining gravity and oxygen, obtaining water, developing agriculture and handling waste far from Earth.

Dubbed the Pancosmorio theory -- a word coined to mean "all world limit" -- it was described in a paper published in Frontiers in Astronomy and Space Sciences.

"For humans to sustain themselves and all of their technology, infrastructure and society in space, they need a self-restoring, Earth-like, natural ecosystem to back them up," said co-author Morgan Irons, a doctoral student conducting research with Johannes Lehmann, professor in the School of Integrative Plant Science at Cornell University. Her work focuses on soil organic carbon persistence under Earth's gravity and varying gravity conditions. "Without these kinds of systems, the mission fails."

The first key is gravity, which Earth life needs to function properly, said co-author Lee Irons, Morgan Irons' father and executive director of the Norfolk Institute, a group that aims to solve problems of human resilience on Earth and in space.

"Gravity induces a gradient in the fluid pressure within the body of the living thing to which the autonomic functions of the life form are attuned," he said. "An example of gravity imbalance would be the negative affect on the eyesight of humans in Earth orbit, where they don't experience the weight necessary to induce the pressure gradient."

Morgan Irons said that it would be unwise to spend billions of dollars to set up a space settlement only to see it fail, because even with all other systems in place, you need gravity.

Humans and all Earth life have evolved within the context of 1G of gravity. "Our bodies, our natural ecosystems, all the energy movement and the way we utilize energy is all fundamentally based upon 1G of gravity being present," she said. "There is just no other place in space where there is 1G of gravity; that just doesn't exist anywhere else in our solar system. That's one of the first problems we must solve."

Oxygen is another key factor. Earth's ecosystem generates oxygen for humans and other life forms. If a technologically advanced primary and a back-up system failed to provide oxygen for the moon base, for example, it would mean instant doom for the astronauts. "A reserve exists everywhere in Earth's nature," Lee Irons said. "Think of the hundreds of thousands of species of plants that generate oxygen. That's the kind of system reserve we need to replicate to be truly sustainable."

Such an ecological system of an outpost would need an enormous amount energy from the sun. The more distant planets and moons from the sun in our own solar system get decreased amounts of energy.

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Lightning strike creates phosphorus material

After lightning struck a tree in a New Port Richey neighborhood, a University of South Florida professor discovered the strike led to the formation of a new phosphorus material. It was found in a rock -- the first time in solid form on Earth -- and could represent a member of a new mineral group.

"We have never seen this material occur naturally on Earth -- minerals similar to it can be found in meteorites and space, but we've never seen this exact material anywhere," said geoscientist Matthew Pasek.

In a recent study published in Communications Earth & Environment, Pasek examines how high-energy events, such as lightning, can cause unique chemical reactions, and in this instance, result in a new material -- one that is transitional between space minerals and minerals found on Earth.

"When lightning strikes a tree, the ground typically explodes out and the surrounding grass dies, forming a scar and sending electric discharge through nearby rock, soil and sand, forming fulgurites, also known as 'fossilized lightning'," Pasek said.

When the New Port Richey homeowners discovered the 'lightning scar', they found a fulgurite and decided to sell it, assuming it had value. Pasek purchased it, and later began a collaboration with Luca Bindi, a professor of mineralogy and crystallography at the University of Florence in Italy.

Together, the team set out to investigate unusual minerals that bear the element phosphorus, especially those formed by lightning, to better understand high-energy phenomena.

"It's important to understand how much energy lightning has because then we know how much damage a lightning strike can cause on average and how dangerous it is," Pasek said. "Florida is the lightning capital of the world and lightning safety is important -- if lightning is strong enough to melt rock, it can certainly melt people too."

In wet environments, such as in Florida, Pasek says iron will often accumulate and encrust tree roots. In this case, not only did the lightning strike combust the iron on the tree roots, but it combusted the naturally occurring carbon in the tree as well. The two elements led to a chemical reaction that created a fulgurite that looked like a metal 'glob.'

Inside the fulgurite, a colorful, crystal-like matter revealed a material never before discovered.

Co-principal investigator Tian Feng, a graduate of USF's geology program, attempted to remake the material in a lab. The experiment was unsuccessful and indicates the material likely forms quickly under precise conditions, and if heated too long, will turn into the mineral found in meteorites.

"Previous researchers indicate that lightning reduction of phosphate to have been a widespread phenomenon on the early Earth," Feng said. "However, there is an environmental phosphite reservoir issue in Earth that these solid phosphite materials are hard to restore."

Feng says this research may reveal other forms of reduced minerals are plausible and many could have been important in the development of life on Earth.

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Increased droughts are disrupting carbon-capturing soil microbes, concerning ecologists

Soil stores more carbon than plants and the atmosphere combined, and soil microbes are largely responsible for putting it there. However, the increasing frequency and severity of drought, such as those that have been impacting California, could disrupt this delicate ecosystem. In a perspective publishing in the journal Trends in Microbiology on April 12, microbial ecologist Steven Allison warns that soil health and future greenhouse gas levels could be impacted if soil microbes adapt to drought faster than plants do. He argues that we need to better understand how microbes respond to drought so that we can manage the situation in both agricultural and natural settings.

"Soil microbes are beneficial, and we couldn't live without their cycling of carbon and nutrients, but climate change and drought can tweak that balance, and we have to be aware of how it's changing," says Allison of the University of California, Irvine.

Some soil microbes take carbon from decomposing plants and store it in the soil, while others release plant carbon back into the atmosphere. The carbon that ends up in the soil is beneficial in multiple ways. "The carbon in the soil has these reverberating effects out to the rest of the world in terms of the infrastructure in our natural and managed ecosystems," says Allison. "Carbon-rich soils hold more nutrients, so plants growing in those soils tend to be more productive, and the carbon changes the physical properties of the soil, which prevents erosion."

"In California now, we have this system where the droughts are more intense, and then the rainfall is more intense," he says. "So, if you're losing your soil carbon, when it rains really hard it could carry away your soil and cause erosion, landslides, mudslides, sediments, and all kinds of problems that we're actually seeing right now."

The carbon that is released back into the atmosphere is another story. "From a climate mitigation standpoint, what we want is for more carbon to be in plants and soils and less carbon to be in the atmosphere, so the more carbon we can absorb into plants through photosynthesis and the more we can transfer and keep in the soil, the better off we're going to be in terms of climate change," says Allison. "That's why it's really important to know how the balance of incoming versus outflowing carbon changes with drought, or warming, or any other climate factor."

Plants and microbes will both be impacted by the increasing frequency of drought, but Allison suspects that microbes will be able to bounce back faster. "Microbes are really adaptable -- they can change their physiology, they can change their abundances so that more drought-adapted microbes take over, and they can potentially evolve -- so we expect that they are going to resist or bounce back from drought," says Allison. "All those different processes can happen pretty quickly with microbes, and much more quickly than with plants."

If more carbon-releasing microbes survive than carbon-sequestering microbes, we could end up with carbon-depleted soils, which would have serious negative implications for plant productivity and future greenhouse gas levels.

We may be able to nudge the balance in the right direction, Allison says, but more research is needed first. "There's still a lot to be done. Right now, we have data that suggests that when we have drought, something changes that results in carbon loss, but we don't understand exactly how or why that's happening, whether drought's changing the abundance of beneficial plant associated microbes versus the carbon releasing microbes, or if it's causing the evolution of one of the microbe groups, or if it's more determined by changes to their immediate physiology," says Allison.

Some microbes could actually help plants cope with drought. If we knew which microbes were most beneficial to plants, and most likely to retain carbon in soil, we could try to tip the balance in their favor.

"There's a lot of potential for us to manage or engineer soil microbes," says Allison. "In agricultural systems, we can look into manipulating the soil or adding beneficial microbes back in. In more natural systems, management would probably be on the plant side: soil microbes are often closely intertwined with plants, so managing the plants can also benefit the microbial part of the ecosystem."

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Your baby's gut is crawling with unknown viruses

Babies tumble about with more than 200 previously unknown viral families within their intestines. This large number comes as a surprise to researchers from the University of Copenhagen and COPSAC, who closely studied the diapers of 647 Danish babies and made the first mapping of its kind. These viruses most likely play an important role in protecting children from chronic diseases.

Viruses are usually associated with illness. But our bodies are full of both bacteria and viruses that constantly proliferate and interact with each other in our gastrointestinal tract. While we have known for decades that gut bacteria in young children are vital to protect them from chronic diseases later on in life, our knowledge about the many viruses found there is minimal.

A few years back, this gave University of Copenhagen professor Dennis Sandris Nielsen the idea to delve more deeply into this question. As a result, a team of researchers from COPSAC (Copenhagen Prospective Studies on Asthma in Childhood) and the Department of Food Science at UCPH, among others, spent five years studying and mapping the diaper contents of 647 healthy Danish one-year-olds.

"We found an exceptional number of unknown viruses in the faeces of these babies. Not just thousands of new virus species -- but to our surprise, the viruses represented more than 200 families of yet to be described viruses. This means that, from early on in life, healthy children are tumbling about with an extreme diversity of gut viruses, which probably have a major impact on whether they develop various diseases later on in life," says Professor Dennis Sandris Nielsen of the Department of Food Science, senior author of the research paper about the study, now published in Nature Microbiology.

The researchers found and mapped a total of 10,000 viral species in the children's faeces -- a number ten times larger than the number of bacterial species in the same children. These viral species are distributed across 248 different viral families, of which only 16 were previously known. The researchers named the remaining 232 unknown viral families after the children whose diapers made the study possible. As a result, new viral families include names like Sylvesterviridae, Rigmorviridae and Tristanviridae.

Bacterial viruses are our allies

"This is the first time that such a systematic an overview of gut viral diversity has been compiled. It provides an entirely new basis for discovering the importance of viruses for our microbiome and immune system development. Our hypothesis is that, because the immune system has not yet learned to separate the wheat from the chaff at the age of one, an extraordinarily high species richness of gut viruses emerges, and is likely needed to protect against chronic diseases like asthma and diabetes later on in life," states Shiraz Shah, first author and a senior researcher at COPSAC.

Ninety percent of the viruses found by the researchers are bacterial viruses -- known as bacteriophages. These viruses have bacteria as their hosts and do not attack the children's own cells, meaning that they do not cause disease. The hypothesis is that bacteriophages primarily serve as allies:

"We work from the assumption that bacteriophages are largely responsible for shaping bacterial communities and their function in our intestinal system. Some bacteriophages can provide their host bacterium with properties that make it more competitive by integrating its own genome into the genome of the bacterium. When this occurs, a bacteriophage can then increase a bacterium's ability to absorb e.g. various carbohydrates, thereby allowing the bacterium to metabolise more things," explains Dennis Sandris Nielsen, who continues:

"It also seems like bacteriophages help keep the gut microbiome balanced by keeping individual bacterial populations in check, which ensures that there are not too many of a single bacterial species in the ecosystem. It's a bit like lion and gazelle populations on the savannah."

Shiraz Shah adds:

"Previously, the research community mostly focused on the role of bacteria in relation to health and disease. But viruses are the third leg of the stool and we need to learn more about them. Viruses, bacteria and the immune system most likely interact and affect each other in some type of balance. Any imbalance in this relationship most likely increases the risk of chronic disease."

The remaining ten percent of viruses found in the children are eukaryotic -- that is, they use human cells as hosts. These can be both friends and foes for us:

"It is thought-provoking that all children run around with 10-20 of these virus types that infect human cells. So, there is a constant viral infection taking place, which apparently doesn't make them sick. We just know very little about what's really at play. My guess is that they're important for training our immune system to recognise infections later. But it may also be that they are a risk factor for diseases that we have yet to discover," says Dennis Sandris Nielsen.

Could play an important role in inflammatory diseases

The researchers have yet to discover where the many viruses in the one-year-olds come from. Their best answer thus far is the environment:

"Our gut is sterile until we are born. During birth, we are exposed to bacteria from the mother and environment. It is likely that some of the first viruses come along with these initial bacteria, while many others are introduced later via dirty fingers, pets, dirt that kids put in their mouths and other things in the environment," says Dennis Sandris Nielsen.

As Shiraz Shah points out, the entire field of research speaks to a huge global health problem:

"A lot of research suggests that the majority of chronic diseases that we're familiar with -- from arthritis to depression -- have an inflammatory component. That is, the immune system is not working as it ought to -- which might be because it wasn't trained properly. So, if we learn more about the role that bacteria and viruses play in a well-trained immune system, it can hopefully lead us to being able to avoid many of the chronic diseases that afflict so many people today."

The research groups have begun investigating the role of gut viruses in relation to a number of different diseases that occur in childhood, such as asthma and ADHD.

Read more at Science Daily

Webb reveals never-before-seen details in Cassiopeia A

The explosion of a star is a dramatic event, but the remains the star leaves behind can be even more dramatic. A new mid-infrared image from NASA's James Webb Space Telescope provides one stunning example. It shows the supernova remnant Cassiopeia A (Cas A), created by a stellar explosion seen from Earth 340 years ago. Cas A is the youngest known remnant from an exploding, massive star in our galaxy, which makes it a unique opportunity to learn more about how such supernovae occur.

"Cas A represents our best opportunity to look at the debris field of an exploded star and run a kind of stellar autopsy to understand what type of star was there beforehand and how that star exploded," said Danny Milisavljevic of Purdue University in West Lafayette, Indiana, principal investigator of the Webb program that captured these observations.

"Compared to previous infrared images, we see incredible detail that we haven't been able to access before," added Tea Temim of Princeton University in Princeton, New Jersey, a co-investigator on the program.

Cassiopeia A is a prototypical supernova remnant that has been widely studied by a number of ground-based and space-based observatories, including NASA's Chandra X-ray Observatory. The multi-wavelength observations can be combined to provide scientists with a more comprehensive understanding of the remnant.

Dissecting the Image

The striking colors of the new Cas A image, in which infrared light is translated into visible-light wavelengths, hold a wealth of scientific information the team is just beginning to tease out. On the bubble's exterior, particularly at the top and left, lie curtains of material appearing orange and red due to emission from warm dust. This marks where ejected material from the exploded star is ramming into surrounding circumstellar gas and dust.

Interior to this outer shell lie mottled filaments of bright pink studded with clumps and knots. This represents material from the star itself, which is shining due to a mix of various heavy elements, such as oxygen, argon, and neon, as well as dust emission.

"We're still trying to disentangle all these sources of emission," said Ilse De Looze of Ghent University in Belgium, another co-investigator on the program.

The stellar material can also be seen as fainter wisps near the cavity's interior.

Perhaps most prominently, a loop represented in green extends across the right side of the central cavity. "We've nicknamed it the Green Monster in honor of Fenway Park in Boston. If you look closely, you'll notice that it's pockmarked with what look like mini-bubbles," said Milisavljevic. "The shape and complexity are unexpected and challenging to understand."

Origins of Cosmic Dust -- and Us

Among the science questions that Cas A may help answer is: Where does cosmic dust come from? Observations have found that even very young galaxies in the early universe are suffused with massive quantities of dust. It's difficult to explain the origins of this dust without invoking supernovae, which spew large quantities of heavy elements (the building blocks of dust) across space.

However, existing observations of supernovae have been unable to conclusively explain the amount of dust we see in those early galaxies. By studying Cas A with Webb, astronomers hope to gain a better understanding of its dust content, which can help inform our understanding of where the building blocks of planets and ourselves are created.

"In Cas A, we can spatially resolve regions that have different gas compositions and look at what types of dust were formed in those regions," explained Temim.

Supernovae like the one that formed Cas A are crucial for life as we know it. They spread elements like the calcium we find in our bones and the iron in our blood across interstellar space, seeding new generations of stars and planets.

"By understanding the process of exploding stars, we're reading our own origin story," said Milisavljevic. "I'm going to spend the rest of my career trying to understand what's in this data set."

Read more at Science Daily

Better understanding the physics of our universe

For the last six years, Indiana University researchers and collaborators from around the world have sought to answer important questions about the most basic laws of physics that govern our universe. Their experiment, the Majorana Demonstrator, has helped to push the horizons on research concerning one of the fundamental building blocks of the universe: neutrinos.

The experiment's final report was published in Physical Review Letters in February.

Neutrinos -- subatomic particles similar to an electron but that have no electric charge -- are the second most abundant particles in the universe after light. However, they are some of the hardest particles to measure because they do not interact the way other particles do.

"Neutrinos have a profound impact on the universe and physics at every imaginable scale, surprising us down at the particle interaction level and having broad impact up through the cosmic scales," said Walter Pettus, an assistant professor of physics in the IU College of Arts and Sciences. "But they are also the most frustrating to study because we know so much about them, yet we have so many gaps."

The Majorana Demonstrator, a collaboration of 60 researchers from 24 institutions, was designed to fill many of those gaps at the same time, probing into the most fundamental properties of neutrinos.

One aspect they hoped to observe was whether the neutrino could be its own antiparticle -- a subatomic particle of the same mass but with the opposite electric charge. Since the neutrino is uncharged, it is the only particle in the universe that could be its own antiparticle. Understanding that would provide insight into why the neutrino has mass in the first place -- information which would have wide-spread impacts in understanding how the universe was formed.

To determine if the neutrino is its own antiparticle, the researchers needed to observe a rare occurrence called neutrinoless double-beta decay. However, this process takes a single atom at least 1026 years -- significantly longer than the age of the universe. Instead, they chose to observe nearly 1026 atoms over the course of six years.

To observe this incredibly rare decay, the researchers needed the perfect environment. In the Sanford Underground Research Facility in the Black Hills of South Dakota, located a mile underground, they built one of the cleanest and quietest environments on Earth. Extremely sensitive detectors were made of a high-purity germanium and were packed in a 50-ton lead shield and surrounded by materials of unprecedented cleanliness. Even the copper used was grown underground in their lab with impurity levels so low they couldn't be measured.

Pettus and a team of IU students were responsible primarily for analyzing data from the experiment. Graduate student Nafis Fuad, undergraduate senior Isaac Baker, sophomore Abby Kickbush and Jennifer James, a student with the Research Experiences for Undergraduates Program, have been involved in the project. Their focus has been on understanding the stability of the experiment, analyzing details of the recorded waveforms and characterizing backgrounds.

"It's like looking for a tiny needle in a very, very, very big haystack -- you have to carefully get rid of all the hays (a.k.a. backgrounds) possible, and you don't even know if there's actually a needle in there in the first place or not," Fuad said. "It's very exciting to be a part of that search."

While the researchers ultimately did not observe the decay they hoped for, they did discover that the neutrino's scale for decay is longer than the limit they placed on it, which they will test further during the next phase of the experiment. In addition, they recorded other scientific results -- ranging from dark matter to quantum mechanics -- that helps provide a better understanding of the universe.

Through the project, the researchers proved that the techniques they utilized could be used at a much larger scale in a potentially game-changing search that could help explain the existence of matter in the universe.

"We didn't see the decay we were looking for, but we have raised the bar on where to look for the physics we're going after," Pettus said. "True to its name, the Demonstrator advanced critical technologies that we are already leveraging for the next phase of the experiment in Italy. We may not have broken our picture of physics yet, but we've certainly pushed the horizons, and I am very excited about what we have accomplished."

The next phase of the project, called LEGEND-200, has already begun taking data in Italy, with plans to run over the next five years. Researchers aim to observe the decay happening at a magnitude higher sensitivity than the Majorana Demonstrator. Beyond that, thanks to support from the U.S. Department of Energy, the team is already designing the successor experiment, LEGEND-1000.

Pettus is excited about the future of this work and looks forward to involving more students on the project, both in data analysis and hardware development for LEGEND-1000.

"If we discover the neutrino is its own antiparticle, there will still be ground under our feet and stars in the sky, and our understanding of physics doesn't change the reality of the physical laws that always have and continue to govern our universe," Pettus said. "But knowing what's down there at the most fundamental level and how the universe works gives us a richer, more beautiful world to live in -- or possibly just weirder -- and that pursuit is fundamentally human."

Read more at Science Daily

Light pollution may extend mosquitoes' biting season

A new study's finding that urban light pollution may disrupt the winter dormancy period for mosquitoes that transmit West Nile virus could be considered both good news and bad news.

The good news is that the disease-carrying pests may not survive the winter if their plans to fatten up are foiled. The bad news is their dormancy period, known as diapause, may simply be delayed -- meaning they're biting humans and animals longer into the fall.

"We see the highest levels of West Nile virus transmission in the late summer and early fall in Ohio. If you have mosquitoes postponing or delaying diapause and continuing to be active longer in the year, that's at a time when the mosquitoes are most likely to be infected with West Nile virus and people could be at greatest risk of contracting it," said Megan Meuti, senior author of the study and an assistant professor of entomology at The Ohio State University.

This study and earlier findings by Meuti and her colleagues are among the first to show that artificial light at night could have a significant impact on mosquito behavior -- including effects that aren't necessarily predictable.

"We're finding that the same urban light at night can have very different effects under different seasonal contexts," she said.

Meuti conducted the study with first author Matthew Wolkoff and Lydia Fyie, both PhD candidates in entomology at Ohio State. The research was published recently in the journal Insects.

Diapause for female Northern house mosquitoes (Culex pipiens) is not quite a winter slumber, but rather a period of dormancy when the insects live in caves, culverts, sheds and other semi-protected locations. Prior to winter's arrival, mosquitoes convert sugary sources, such as plant nectar, into fat. As days get longer, females begin foraging for blood meals to enable egg production. Some get infected with West Nile virus by feeding on infected birds, and later transmit the virus when they feed on people, horses and other mammals.

This study builds upon two previous findings from Meuti's lab: For her dissertation, Meuti found that circadian clock genes differ between diapausing and non-diapausing mosquitoes, strongly suggesting that day length dictates when diapause should start. And more recent work led by Fyie found that female mosquitoes exposed to dim light at night averted diapause and became reproductively active -- even when short days indicated they should be dormant.

In the current study authored by Wolkoff, the researchers pursued both lines of inquiry, comparing daily activity and nutrient accumulation by mosquitoes reared in two lab conditions -- long days mimicking the insects' active season and short days that induced dormancy -- with and without exposure to artificial light at night.

The study provided more evidence associated with a circadian pattern to mosquito behavior, showing that insects' activity decreases during diapause, but the circadian rhythmicity of that activity is sustained even during this dormant period.

The introduction of artificial light at night was found to affect those activity patterns and to influence mosquitoes' acquisition of nutrient reserves needed for fattening up and weathering winter temperatures.

Exposure to light pollution suppressed the amount of water-soluble carbohydrates -- sugars that are an essential food source during winter -- that were accumulated by mosquitoes in both long- and short-day conditions. Patterns of accumulation of the sugar glycogen were reversed by exposure to artificial light at night: Under normal conditions, non-dormant mosquitoes had lots of glycogen in their bodies but diapausing bugs did not -- but in mosquitoes subjected to light pollution, the long-day mosquitoes didn't accumulate much glycogen and short-day mosquitoes showed an increase in glycogen accumulation.

The researchers observed consistent trends in activity-related effects of light at night, with slight increased activity among the dormant mosquitoes and slightly suppressed activity among long-day mosquitoes expected to be busy looking for food. Though the findings weren't statistically significant, Wolkoff said the combined observations suggest light pollution causes mosquitoes to ward off diapause -- perhaps by scrambling signals from their circadian clock.

"This could be bad for mammals in the short term because mosquitoes are potentially biting us later in the season, but it could also be bad for mosquitoes in the long term because they might be failing to fully engage in preparatory activities they need to survive the winter during diapause, and that might reduce their survival rate," Wolkoff said.

Read more at Science Daily

Male yellow crazy ants are real-life chimeras

The yellow crazy ant, or Anoplolepis gracilipes, has the infamous distinction of being among the worst invasive species in the world. However, this is not the reason for which this particular ant is studied by a team of international researchers. What interests them is how the insects reproduce, because males of this ant have long perplexed scientists. "The results of previous genetic analyses of the yellow crazy ant have shown that the males of this species have two copies of each chromosome. This was highly unexpected, as males usually develop from unfertilized eggs in ants, bees, and wasps -- and thus should only have one maternal copy of each chromosome," explained Dr. Hugo Darras, Assistant Professor at Johannes Gutenberg University Mainz (JGU) and lead author of the corresponding article recently published in Science. "With this in view, we decided to investigate this puzzling phenomenon with subsequent experiments."

Two genomes in different cell clusters

The results were quite extraordinary. It had been assumed to date that the males of the yellow crazy ant carried the same two sets of chromosomes in all cells of their body. However, the team was able to demonstrate that this premise was anything but correct. "We discovered that the male ants have maternal and paternal genomes in different cells of their body and are thus chimeras. To put it another way, all males have two genomes, but each cell of their bodies contains only one or the other of the two genomes," summarized Darras. Normally, in a multicellular life form -- be this a human, a dog, or a bat -- all cells contain identical genetic material.

The research team concludes that male yellow crazy ants are chimeras: they develop from fertilized eggs in which the two parental gametes do not actually fuse. Instead, the maternal and paternal nuclei divide separately within the same egg, meaning that the resultant adult males have both parental DNA sequences but in different body cells. When the gametes do fuse, either a queen or a worker develops from the egg, depending on the genetic information carried by the sperm. It is yet unknown what mechanisms determine whether fusion of the parental gametes takes place or not.

Chimerism and the yellow crazy ant: A mode of reproduction previously unknown to science

Chimeras are individuals whose cells contain different genetic materials. They naturally occur in certain species, such as corals and angler fish, in which separate individuals can merge to become one. Chimerism can also be found in humans and other placenta mammals. During gestation, mother and fetus can exchange a small number of cells so the offspring usually has a few cells that contain the same genetic material as the mother. Such small-scale exchanges also occur between twins in the womb. "In contrast to these known cases, chimerism in the yellow crazy ant does not result from the fusion of two separate individuals or an exchange of cells between them. Instead, this process has its origin within a single fertilized egg. This is unique," concluded Darras. Hence, the development of the male yellow crazy ant appears to contravene one of the fundamental laws of biological inheritance in which all cells of an individual should contain the same genome.

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New findings that map the universe's cosmic growth support Einstein's theory of gravity

For millennia, humans have been fascinated by the mysteries of the cosmos.

Unlike ancient philosophers imagining the universe's origins, modern cosmologists use quantitative tools to gain insights into the universe's evolution and structure. Modern cosmology dates back to the early 20th century, with the development of Albert Einstein's theory of general relativity.

Now, researchers from the Atacama Cosmology Telescope (ACT) collaboration have created a groundbreaking new image that reveals the most detailed map of dark matter distributed across a quarter of the entire sky, extending deep into the cosmos. What's more, it confirms Einstein's theory of how massive structures grow and bend light, over the entire 14-billion-year life span of the universe.

"We have mapped the invisible dark matter across the sky to the largest distances, and clearly see features of this invisible world that are hundreds of millions of light-years across, says Blake Sherwin, professor of cosmology at the University of Cambridge, where he leads a group of ACT researchers. "It looks just as our theories predict."

Despite making up 85% of the universe and influencing its evolution, dark matter has been hard to detect because it doesn't interact with light or other forms of electromagnetic radiation. As far as we know dark matter only interacts with gravity.

To track it down, the more than 160 collaborators who have built and gathered data from the National Science Foundation's Atacama Cosmology Telescope in the high Chilean Andes observe light emanating following the dawn of the universe's formation, the Big Bang -- when the universe was only 380,000 years old. Cosmologists often refer to this diffuse light that fills our entire universe as the "baby picture of the universe," but formally, it is known as the cosmic microwave background radiation (CMB).

The team tracks how the gravitational pull of large, heavy structures including dark matter warps the CMB on its 14-billion-year journey to us, like how a magnifying glass bends light as it passes through its lens.

"We've made a new mass map using distortions of light left over from the Big Bang," says Mathew Madhavacheril, assistant professor in the Department of Physics and Astronomy at the University of Pennsylvania. "Remarkably, it provides measurements that show that both the 'lumpiness' of the universe, and the rate at which it is growing after 14 billion years of evolution, are just what you'd expect from our standard model of cosmology based on Einstein's theory of gravity."

Sherwin adds, "our results also provide new insights into an ongoing debate some have called 'The Crisis in Cosmology,'"explaining that this crisis stems from recent measurements that use a different background light, one emitted from stars in galaxies rather than the CMB. These have produced results that suggest the dark matter was not lumpy enough under the standard model of cosmology and led to concerns that the model may be broken. However, the team's latest results from ACT were able to precisely assess that the vast lumps seen in this image are the exact right size.

"When I first saw them, our measurements were in such good agreement with the underlying theory that it took me a moment to process the results," says Cambridge Ph.D. student Frank Qu, part of the research team. "It will be interesting to see how this possible discrepancy between different measurements will be resolved."

"The CMB lensing data rivals more conventional surveys of the visible light from galaxies in their ability to trace the sum of what is out there," says Suzanne Staggs, director of ACT and Henry DeWolf Smyth Professor of Physics at Princeton University. "Together, the CMB lensing and the best optical surveys are clarifying the evolution of all the mass in the universe."

"When we proposed this experiment in 2003, we had no idea the full extent of information that could be extracted from our telescope," says Mark Devlin, the Reese Flower Professor of Astronomy at the University of Pennsylvania and the deputy director of ACT. "We owe this to the cleverness of the theorists, the many people who built new instruments to make our telescope more sensitive, and the new analysis techniques our team came up with."

Read more at Science Daily

What is it good for? Absolutely one thing: Luna moths use their tails solely for bat evasion

In a pair of complementary studies, researchers took a close look at Luna moth (Actias luna) tails through the eyes of birds and female moths to test the tails' role in predation and sexual selection. Scientists have known for about a decade that Luna moths -- and other related silkmoths -- use their long, trailing tails to misdirect bat attacks.

"They have projections off the back of the hindwing that end in twisted, cupped paddles," said Juliette Rubin, a doctoral student at the Florida Museum of Natural History and lead author of both studies. "From experimental work with bats and moths in a flight room, we've found that these structures seem to reflect bat sonar in such a way that bats often aim their attacks at the tails instead of the main body."

Traits that evolve for one specific function can often be co-opted by natural selection for another, and Rubin wondered whether the twisted tails of Luna moths might come with any additional benefits or hidden costs.

Male Luna moths doff their tails, retain their charm

Silkmoths have independently evolved tails on multiple occasions across three continents, and the appendages can vary significantly in length. Hind wings in some species can extend to more than twice the size of the moth's wingspan, and the longer the tail, the more likely a moth will successfully thwart a prowling bat.

But far from being drab, utilitarian decoys meant only for sonar-sensing bats, silkmoth tails are often visually stunning, like decorative streamers trailing behind a kite. Across the animal and plant kingdoms, many of the most colorful and alluring structures are used to attract mates or pollinators, and scientists suspected the same might be true of silkmoth tails.

This type of dual function for a single trait isn't without precedent. The vivid colors of strawberry poison dart frogs (Oophaga pumilio) both deter predators and help males attract mates; male deer and other ungulates use their antlers to fight off rivals and signal their vigor to females; and moths that use clicks or chirruping sounds to disrupt bat echolocation can compose duets using the same sounds during courtship.

Luna moths have neither mouths to produce sound nor ears to hear it, but they do have sensitive eyes and powerful scent-detecting antennae. When female Luna moths are ready to mate, they perch in one place and emit a pheromone, a single molecule of which is enough to trigger a male antenna. The males of closely related Indian moon moths (Actias selene) can find females from more than six miles away by following the pheromone plume to its source.

"We don't know how many males are traveling to a female each night," Rubin said. "It's entirely possible she's able to call in multiple suitors and potentially have her pick."

Rubin put this idea to the test, setting up mating experiments in which a female Luna moth was enclosed in a flight box with two males: one with normal hind wings, and one with its tails removed.

Initially, the data seemed to suggest that females preferred males whose wings remained intact, but additional controlled experiments demonstrated that this was more likely an incidental effect of the tail removal. During trials in which both males had their wings clipped, and one had the tails glued back on, there was no difference in their mating success.

Do tails make Luna moths invisible to bats but conspicuous to birds?

Having demonstrated tail wings likely weren't conferring any additional benefits beyond survival, Rubin wanted to see whether they had any obvious drawbacks. Their long tails effectively throw off pursuing bats by creating a decoy target, but bats aren't the only adversaries Luna moths have to avoid. Their electric green tails with bright, pink parfait borders might make Luna moths noticeable to birds and other visually oriented predators that hunt during the day.

Other organisms contend with similar tradeoffs. The bioluminescent displays of fireflies make it easier for males to locate potential mates, but it also makes them stand out to nocturnal frogs and geckoes.

Luna moths live incredibly short lives, during which they can afford to lose a tail or two. Once they emerge from their cocoons, the moths have about a week to find a mate and reproduce before dying. "This creates a very intense period of adulthood, where surviving the night is of the utmost importance," Rubin said.

Luna moths are mostly inactive during the day, reducing their chances of being nabbed midair. If they don't do a good enough job concealing themselves, however, they run the risk of not surviving to nightfall.

Rubin wanted to know if their visually elaborate tails put Luna moths at a disadvantage in this high-stakes game of hide-and-seek. To find out, she and her colleagues wrapped mealworms in pastry dough in the shape and size of Luna moth bodies, to which they attached real wings, half of which had tails. They partially hid these moth replicas among branches and leaves in an aviary, then introduced a succession of Carolina wrens (Thryothorus ludovicianus), recording how many of the snacks the birds located and ate.

The results conclusively indicate that the tails had no effect on the birds' ability to locate the fake moths. This might seem odd to us, Rubin said, because we're such visually oriented animals. But there's evidence that suggests birds might rely on search images when trying to distinguish food items from patterns in the background.

Humans do this too. When trying to complete a Where's Waldo puzzle, people often look for the characteristic red, horizontal lines of Waldo's shirt while scanning across the page. It's possible that Luna moth tails don't match the typical moth and butterfly mold that birds expect to see while foraging, the equivalent of Waldo wearing a solid red shirt rather than his signature stripes.

While not indicative of all silkmoths, the studies suggest that these stunning and complex structures evolved for a single function in Luna moths.

"When we see these really obvious physical features in animals, we're often drawn into stories we've heard about them," Rubin said. "One is that conspicuous traits are for attracting mates or competing with rivals, and another is that these very showy traits must come with a cost. Both of these studies show it's really important to test those assumptions. A trait that's obvious to us, as visual creatures, might not stand out to the predators that hunt them, and the traits that we think are dynamic and alluring might not seem that way to a potential mate."

Read more at Science Daily

Cities will need more resilient electricity networks to cope with extreme weather

Dense urban areas amplify the effects of higher temperatures, due to the phenomenon of heat islands in cities. This makes cities more vulnerable to extreme climate events. Large investments in the electricity network will be necessary to cool us down during heatwaves and keep us warm during cold snaps, according to a new study led by Lund University in Sweden.

"Unless we account for extreme climate events and continued urbanisation, the reliability of electricity supply will fall by up to 30%. An additional outlay of 20-60 per cent will be required during the energy transition in order to guarantee that cities can cope with different kinds of climate," says Vahid Nik, Professor of Building Physics at Lund University and one of the authors of the article in Nature Energy.

The study presents a modelling platform that ties together climate, building and energy system models in order to facilitate simulation and evaluation of cities' energy transition. The aim is to secure the cities' resilience against future climate changes at the same time as densification of urban areas is taking place. In particular, researchers have looked closely at extreme weather events (e.g. heatwaves and cold snaps) by producing simulations of urban microclimates.

"Our results show that high density areas give rise to a phenomenon called urban heat islands, which make cities more vulnerable to the effects of extreme climate events, particularly in southern Europe. For example, the outdoor temperature can rise by 17% while the wind speed falls by 61%. Urban densification -- a recommended development strategy in order to reach the UN's energy and climate goals -- could make the electricity network more vulnerable. This must be taken into consideration when designing urban energy systems, says Kavan Javanroodi, Assistant Professor in Building and Urban Physics.

"The framework we have developed connects future climate models to buildings and energy systems at city level, taking the urban microclimate into account. For the first time, we are getting to grips with several challenges around the issues of future climate uncertainty and extreme weather situations, focussing in particular on what are known as 'HILP' or High Impact Low Probability events," says Vahid Nik.

There is still a large gap between future climate modelling and building and energy analyses and their links to one another. According to Vahid Nik, the model now being developed makes a great contribution to closing that gap.

"Our results answer questions like 'how big an effect will extreme weather events have in the future, given the predicted pace of urbanisation and several different future climate scenarios?', 'how do we take them and the connections between them into account?' and 'how does the nature of urban development contribute to exacerbating or mitigating the effects of extreme events at regional and municipal level?' "

The results show that the peaks in demand in the energy system increase more than previously thought when extreme microclimates are taken into account, for example with an increase in cooling demand for 68% in Stockholm and 43% in Madrid on the hottest day of the year. Not considering this can lead to incorrect estimates of cities' energy requirements, which can turn into power shortage and even blackouts.

"There is a marked deviation between the heat and cooling requirements shown in today's urban climate models, compared to the outcomes of our calculations when urban morphology, the physical design of the city, is more complex. For example, if we fail to take into account the urban climate in Madrid, we could underestimate the need for cooling by around 28%," says Kavan Javanroodi.

Vahid Nik explains that an increasing number of countries have become interested in extreme weather events, energy issues and the impact on public health. At the same time, there are no methods of quantifying the effects of climate change and planning for adapting to them, especially when it comes to extreme weather events and climate variations across space and time.

Read more at Science Daily

Shutting down nuclear power could increase air pollution

Nearly 20 percent of today's electricity in the United States comes from nuclear power. The U.S. has the largest nuclear fleet in the world, with 92 reactors scattered around the country. Many of these power plants have run for more than half a century and are approaching the end of their expected lifetimes.

Policymakers are debating whether to retire the aging reactors or reinforce their structures to continue producing nuclear energy, which many consider a low-carbon alternative to climate-warming coal, oil, and natural gas.

Now, MIT researchers say there's another factor to consider in weighing the future of nuclear power: air quality. In addition to being a low carbon-emitting source, nuclear power is relatively clean in terms of the air pollution it generates. Without nuclear power, how would the pattern of air pollution shift, and who would feel its effects?

The MIT team took on these questions in a new study appearing in Nature Energy. They lay out a scenario in which every nuclear power plant in the country has shut down, and consider how other sources such as coal, natural gas, and renewable energy would fill the resulting energy needs throughout an entire year.

Their analysis reveals that indeed, air pollution would increase, as coal, gas, and oil sources ramp up to compensate for nuclear power's absence. This in itself may not be surprising, but the team has put numbers to the prediction, estimating that the increase in air pollution would have serious health effects, resulting in an additional 5,200 pollution-related deaths over a single year.

If, however, more renewable energy sources become available to supply the energy grid, as they are expected to by the year 2030, air pollution would be curtailed, though not entirely. The team found that even under this heartier renewable scenario, there is still a slight increase in air pollution in some parts of the country, resulting in a total of 260 pollution-related deaths over one year.

When they looked at the populations directly affected by the increased pollution, they found that Black or African American communities -- a disproportionate number of whom live near fossil-fuel plants -- experienced the greatest exposure.

"This adds one more layer to the environmental health and social impacts equation when you're thinking about nuclear shutdowns, where the conversation often focuses on local risks due to accidents and mining or long-term climate impacts," says lead author Lyssa Freese, a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS).

"In the debate over keeping nuclear power plants open, air quality has not been a focus of that discussion," adds study author Noelle Selin, a professor in MIT's Institute for Data, Systems, and Society (IDSS) and EAPS. "What we found was that air pollution from fossil fuel plants is so damaging, that anything that increases it, such as a nuclear shutdown, is going to have substantial impacts, and for some people more than others."

The study's MIT-affiliated co-authors also include Principal Research Scientist Sebastian Eastham and Guillaume Chossière SM '17, PhD '20, along with Alan Jenn of the University of California at Davis.

Future phase-outs

When nuclear power plants have closed in the past, fossil fuel use increased in response. In 1985, the closure of reactors in Tennessee Valley prompted a spike in coal use, while the 2012 shutdown of a plant in California led to an increase in natural gas. In Germany, where nuclear power has almost completely been phased out, coal-fired power increased initially to fill the gap.

Noting these trends, the MIT team wondered how the U.S. energy grid would respond if nuclear power were completely phased out.

"We wanted to think about what future changes were expected in the energy grid," Freese says. "We knew that coal use was declining, and there was a lot of work already looking at the impact of what that would have on air quality. But no one had looked at air quality and nuclear power, which we also noticed was on the decline."

In the new study, the team used an energy grid dispatch model developed by Jenn to assess how the U.S. energy system would respond to a shutdown of nuclear power. The model simulates the production of every power plant in the country and runs continuously to estimate, hour by hour, the energy demands in 64 regions across the country.

Much like the way the actual energy market operates, the model chooses to turn a plant's production up or down based on cost: Plants producing the cheapest energy at any given time are given priority to supply the grid over more costly energy sources.

The team fed the model available data on each plant's changing emissions and energy costs throughout an entire year. They then ran the model under different scenarios, including: an energy grid with no nuclear power, a baseline grid similar to today's that includes nuclear power, and a grid with no nuclear power that also incorporates the additional renewable sources that are expected to be added by 2030.

They combined each simulation with an atmospheric chemistry model to simulate how each plant's various emissions travel around the country and to overlay these tracks onto maps of population density. For populations in the path of pollution, they calculated the risk of premature death based on their degree of exposure.

System response

Their analysis showed a clear pattern: Without nuclear power, air pollution worsened in general, mainly affecting regions in the East Coast, where nuclear power plants are mostly concentrated. Without those plants, the team observed an uptick in production from coal and gas plants, resulting in 5,200 pollution-related deaths across the country, compared to the baseline scenario.

They also calculated that more people are also likely to die prematurely due to climate impacts from the increase in carbon dioxide emissions, as the grid compensates for nuclear power's absence. The climate-related effects from this additional influx of carbon dioxide could lead to 160,000 additional deaths over the next century.

"We need to be thoughtful about how we're retiring nuclear power plants if we are trying to think about them as part of an energy system," Freese says. "Shutting down something that doesn't have direct emissions itself can still lead to increases in emissions, because the grid system will respond."

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Scientists map gusty winds in a far-off neutron star system

An accretion disk is a colossal whirlpool of gas and dust that gathers around a black hole or a neutron star like cotton candy as it pulls in material from a nearby star. As the disk spins, it whips up powerful winds that push and pull on the sprawling, rotating plasma. These massive outflows can affect the surroundings of black holes by heating and blowing away the gas and dust around them.

At immense scales, "disk winds" can offer clues to how supermassive black holes shape entire galaxies. Astronomers have observed signs of disk winds in many systems, including accreting black holes and neutron stars. But to date, they've only ever glimpsed a very narrow view of this phenomenon.

Now, MIT astronomers have observed a wider swath of winds, in Hercules X-1, a system in which a neutron star is drawing material away from a sun-like star. This neutron star's accretion disk is unique in that it wobbles, or "precesses," as it rotates. By taking advantage of this wobble, the astronomers have captured varying perspectives of the rotating disk and created a two-dimensional map of its winds, for the first time.

The new map reveals the wind's vertical shape and structure, as well as its velocity -- around hundreds of kilometers per second, or about a million miles per hour, which is on the milder end of what accretion disks can spin up.

If astronomers can spot more wobbling systems in the future, the team's mapping technique could help determine how disk winds influence the formation and evolution of stellar systems, and even entire galaxies.

"In the future, we could map disk winds in a range of objects and determine how wind properties change, for instance, with the mass of a black hole, or with how much material it is accreting," says Peter Kosec, a postdoc in MIT's Kavli Institute for Astrophysics and Space Research. "That will help determine how black holes and neutron stars influence our universe."

Kosec is the lead author of a study appearing in Nature Astronomy. His MIT co-authors include Erin Kara, Daniele Rogantini, and Claude Canizares, along with collaborators from multiple institutions, including the Institute of Astronomy in Cambridge, U.K.

Fixed sight

Disk winds have most often been observed in X-ray binaries -- systems in which a black hole or a neutron star is pulling material from a less dense object and generating a white-hot disk of inspiraling matter, along with outflowing wind. Exactly how winds are launched from these systems is unclear. Some theories propose that magnetic fields could shred the disk and expel some of the material outward as wind. Others posit that the neutron star's radiation could heat and evaporate the disk's surface in white-hot gusts.

Clues to a wind's origins may be deduced from its structure, but the shape and extent of disk winds has been difficult to resolve. Most binaries produce accretion disks that are relatively even in shape, like thin donuts of gas that spins in a single plane. Astronomers who study these disks from far-off satellites or telescopes can only observe the effects of disk winds within a fixed and narrow range, relative to their rotating disk. Any wind that astronomers manage to detect is therefore a small sliver of its larger structure.

"We can only probe the wind properties at a single point, and we're completely blind to everything around that point," Kosec notes.

In 2020, he and his colleagues realized that one binary system could offer a wider view of disk winds. Hercules X-1 has stood out from most known X-ray binaries for its warped accretion disk, which wobbles as it rotates around the system's central neutron star.

"The disk is really wobbling over time every 35 days, and the winds are originating somewhere in the disk and crossing our line of sight at different heights above the disk with time," Kosec explains. "That's a very unique property of this system which allows us to better understand its vertical wind properties."

A warped wobble

In the new study, the researchers observed Hercules X-1 using two X-ray telescopes -- the European Space Agency's XMM Newton and NASA's Chandra Observatory.

"What we measure is an X-ray spectrum, which means the amount of X-ray photons that arrive at our detectors, versus their energy. We measure the absorption lines, or the lack of X-ray light at very specific energies," Kosec says. "From the ratio of how strong the different lines are, we can determine the temperature, velocity, and the amount of plasma within the disk wind."

With Hercules X-1's warped disk, astronomers were able to see the line of the disk moving up and down as it wobbled and rotated, similar to the way a warped record appears to oscillate when seen from edge-on. The effect was such that the researchers could observe signs of disk winds at changing heights with respect to the disk, rather than at a single, fixed height above a uniformly rotating disk.

By measuring X-ray emissions and the absorption lines as the disk wobbled and rotated over time, the researchers could scan properties such as the temperature and density of winds at various heights with respect to its disk and construct a two-dimensional map of the wind's vertical structure.

"What we see is that the wind rises from the disk, at an angle of about 12 degrees with respect to the disk as it expands in space," Kosec says. "It's also getting colder and more clumpy, and weaker at greater heights above the disk."

The team plans to compare their observations with theoretical simulations of various wind-launching mechanisms, to see which could best explain the wind's origins. Further out, they hope to discover more warped and wobbling systems, and map their disk wind structures. Then, scientists could have a broader view of disk winds, and how such outflows influence their surroundings -- particularly at much larger scales.

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Scientists show how we can anticipate rather than react to extinction in mammals

Most conservation efforts are reactive. Typically, a species must reach threatened status before action is taken to prevent extinction, such as establishing protected areas. A new study published in the journal Current Biology on April 10 shows that we can use existing conservation data to predict which currently unthreatened species could become threatened and take proactive action to prevent their decline before it is too late.

"Conservation funding is really limited," says lead author Marcel Cardillo of Australian National University. "Ideally, what we need is some way of anticipating species that may not be threatened at the moment but have a high chance of becoming threatened in the future. Prevention is better than cure."

To predict "over-the-horizon" extinction risk, Cardillo and colleagues looked at three aspects of global change -- climate change, human population growth, and the rate of change in land use -- together with intrinsic biological features that could make some species more vulnerable. The team predicts that up to 20% of land mammals will have a combination of two or more of these risk factors by the year 2100.

"Globally, the percentage of terrestrial mammal species that our models predict will have at least one of the four future risk factors by 2100 ranges from 40% under a middle-of-the-road emissions scenario with broad species dispersal to 58% under a fossil-fueled development scenario with no dispersal," say the authors.

"There's a congruence of multiple future risk factors in Sub-Saharan African and southeastern Australia: climate change (which is expected to be particularly severe in Africa), human population growth, and changes in land use," says Cardillo. "And there are a lot of large mammal species that are likely to be more sensitive to these things. It's pretty much the perfect storm."

Larger mammals in particular, like elephants, rhinos, giraffes, and kangaroos, are often more susceptible to population decline since their reproductive patterns influence how quickly their populations can bounce back from disturbances. Compared to smaller mammals, such as rodents, which reproduce quickly and in larger numbers, bigger mammals, such as elephants, have long gestational periods and produce fewer offspring at a time.

"Traditionally, conservation has relied heavily on declaring protected areas," says Cardillo. "The basic idea is that you remove or mitigate what is causing the species to become threatened."

"But increasingly, it's being recognized that that's very much a Western view of conservation because it dictates separating people from nature," says Cardillo. "It's a sort of view of nature where humans don't play a role, and that's something that doesn't sit well with a lot of cultures in many parts of the world."

In preventing animal extinction, the researchers say we must also be aware of how conservation impacts Indigenous communities. Sub-Saharan Africa is home to many Indigenous populations, and Western ideas of conservation, although well-intended, may have negative impacts.

Australia has already begun tackling this issue by establishing Indigenous Protected Areas (IPAs), which are owned by Indigenous peoples and operate with the help of rangers from local communities. In these regions, humans and animals can coexist, as established through collaboration between governments and private landowners outside of these protected areas.

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Early crop plants were more easily 'tamed'

The story of how ancient wolves came to claim a place near the campfire as humanity's best friend is a familiar tale (even if scientists are still working out some of the specifics). In order to be domesticated, a wild animal must be tamable -- capable of living in close proximity to people without exhibiting dangerous aggression or debilitating fear. Taming was the necessary first step in animal domestication, and it is widely known that some animals are easier to tame than others.

But did humans also favor certain wild plants for domestication because they were more easily "tamed"? Research from Washington University in St. Louis calls for a reappraisal of the process of plant domestication, based on almost a decade of observations and experiments. The behavior of erect knotweed, a buckwheat relative, has WashU paleoethnobotanists completely reassessing our understanding of plant domestication.

"We have no equivalent term for tameness in plants," said Natalie Mueller, assistant professor of archaeology in Arts & Sciences at Washington University. "But plants are capable of responding to people. They have a developmental capacity to be tamed."

Her work with early indigenous North American crops shows that some wild plants respond quickly to clearing, fertilizing, weeding or thinning. Plants that respond in ways that make cultivation easier or more productive could be considered more easily tamed than those that cannot.

"If plants responded rapidly in ways that were beneficial to early cultivators -- for example by producing higher yields, larger seeds, seeds that were easier to sprout, or a second crop in a single growing season -- this would have encouraged humans to continue investing in the co-evolutionary relationship," she said.

This capacity to express different traits and characteristics in response to the environment is called plasticity, and not all species are equally plastic.

"Some plants respond quickly and obviously to cultivation and care," Mueller said. "I think ancient people would have noticed that they could double their yields just by thinning out dense stands of plants. This is one of the simplest and most common gardening techniques, but it has many important effects on the development of plants."

What would an early farmer do?

Mueller's study, published April 7 in PLOS ONE, focuses on work with a plant called erect knotweed, a member of the buckwheat family that was domesticated by indigenous farmers in eastern North America. The domesticated sub-species is now extinct; humans don't eat it anymore. But Mueller and others have previously uncovered caches of seeds stored in caves, charred plant remnants in ancient hearths, and even the seeds of erect knotweed in human feces, clear evidence that this species was once consumed as a staple food.

Mueller, who studies lost crops, has spent years growing erect knotweed and other crop progenitors in experimental gardens, including at Washington University's environmental field station, Tyson Research Center. She hasn't always been successful with growing the plants she collects in the wild. In that way, Mueller can relate to the early farmers who similarly experimented with plants to discover their potential.

Her efforts have often been stymied by seed dormancy, a common feature among wild plants.

Unlike seeds you buy at the garden store, the seeds of most wild plants will not germinate if you simply sprinkle some water on them. Their requirements for germination are diverse and shaped by their evolutionary history. For example, if a plant has evolved in a place with a winter, like the Midwest, its seeds may not germinate unless they experience a long cold period. This prevents them from germinating too soon in the wild -- they are waiting for spring. Domesticated plants have lost their diverse germination requirements.

The loss of germination inhibitors has presented a paradox to theorists of domestication. Many of the selective pressures that could have favored the evolution of this trait derive from planting seeds. But why would ancient people have started planting seeds if none of them germinated?

With erect knotweed, Mueller experienced a breakthrough of sorts. Based on four seasons of observations, Mueller determined that growing wild plants in the low-density conditions typical of a cultivated garden (i.e. spaced out and weeded) triggers plants to produce seeds that germinate more easily. This makes the harvests easier to plant successfully the next time around, eliminating a key barrier to further selection.

"Our results show that erect knotweed grown in low-density agroecosystems spontaneously 'act domesticated' in a single growing season, before any selection has occurred," Mueller said.

Think of it as the plant equivalent to that first wolf who, though still a wild animal, sat down with its human friend around the fire. This is a behavioral shift, rather than an evolutionary one, but it allows new evolutionary pathways to open up.

A role for plant behavior

Mueller believes there is a bias in domestication studies toward viewing this changeability, or plasticity, as noise that is getting in the way of attempts to explain evolutionary change. Instead, this paper argues that we need to understand the development and behavior of wild crop relatives in order to explain the evolutionary process of domestication.

"Because we lack the practical experience with crop progenitors that ancient people had, these effects of the environment on plant development have gone mostly unnoticed and understudied," Mueller said.

Her findings could have applications for developing new food crops: there is no reason why we have to be limited to the plants that our ancestors domesticated thousands of years ago.

Some researchers have been calling for de novo domestication -- selecting wild plants with desirable characteristics and intentionally domesticating them. It may make sense to start looking to wild plants that are easily tamed as potential crops that could be developed for the future, Mueller said.

This paper also contributes to a growing awareness that plants are responsive and communicative beings. Though this idea is cutting-edge and hotly debated in biology and ecology, it is widespread in indigenous North American philosophies and probably would have been held by the people who domesticated erect knotweed and other plants thousands of years ago.

Recent research has shown how plants warn relatives about herbivores using chemical signaling, share resources through mycorrhizal networks and even emit noises when they are injured or stressed.

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