A genetic hack to make photosynthesis more efficient could be a boon for agricultural production, at least for some plants.

This feat of genetic engineering simplifies a complex, energy-expensive operation that many plants must perform during photosynthesis known as photorespiration. In field tests, genetically modifying tobacco in this way increased plant growth by over 40 percent. If it produces similar results in other crops, that could help farmers meet the food demands of a growing global population, researchers report in the Jan. 4 Science.
Streamlining photorespiration is “a great step forward in efforts to enhance photosynthesis,” says Spencer Whitney, a plant biochemist at Australian National University in Canberra not involved in the work.

Now that the agricultural industry has mostly optimized the use of yield-boosting tools like pesticides, fertilizers and irrigation, researchers are trying to micromanage and improve plant growth by designing ways to make photosynthesis more efficient (SN: 12/24/16, p. 6).

Photorespiration is a major roadblock to achieving such efficiency. It occurs in many plants, such as soybeans, rice and wheat, when an enzyme called Rubisco — whose main job is to help transform carbon dioxide from the atmosphere into sugars that fuel plant growth — accidentally snatches an oxygen molecule out of the atmosphere instead.

That Rubisco-oxygen interaction, which happens about 20 percent of the time, generates the toxic compound glycolate, which a plant must recycle into useful molecules through photorespiration. This process comprises a long chain of chemical reactions that span four compartments in a plant cell. All told, completing a cycle of photorespiration is like driving from Maine to Florida by way of California. That waste of energy can cut crop yields by 20 to 50 percent, depending on plant species and environmental conditions.Streamlining photorespiration is “a great step forward in efforts to enhance photosynthesis,” says Spencer Whitney, a plant biochemist at Australian National University in Canberra not involved in the work.

Now that the agricultural industry has mostly optimized the use of yield-boosting tools like pesticides, fertilizers and irrigation, researchers are trying to micromanage and improve plant growth by designing ways to make photosynthesis more efficient (SN: 12/24/16, p. 6).

Photorespiration is a major roadblock to achieving such efficiency. It occurs in many plants, such as soybeans, rice and wheat, when an enzyme called Rubisco — whose main job is to help transform carbon dioxide from the atmosphere into sugars that fuel plant growth — accidentally snatches an oxygen molecule out of the atmosphere instead.

That Rubisco-oxygen interaction, which happens about 20 percent of the time, generates the toxic compound glycolate, which a plant must recycle into useful molecules through photorespiration. This process comprises a long chain of chemical reactions that span four compartments in a plant cell. All told, completing a cycle of photorespiration is like driving from Maine to Florida by way of California. That waste of energy can cut crop yields by 20 to 50 percent, depending on plant species and environmental conditions.
Using genetic engineering, researchers have now designed a more direct chemical pathway for photorespiration that is confined to a single cell compartment — the cellular equivalent of a Maine-to-Florida road trip straight down the East Coast.

Paul South, a molecular biologist with the U.S. Department of Agriculture in Urbana, Ill., and colleagues embedded genetic directions for this shortcut, written on pieces of algae and pumpkin DNA, in tobacco plant cells. The researchers also genetically engineered the cells to not produce a chemical that allows glycolate to travel between cell compartments to prevent the glycolate from taking its normal route through the cell.
Unlike previous experiments with human-designed photorespiration pathways, South’s team tested its photorespiration detour in plants grown in fields under real-world farming conditions. Genetically altered tobacco produced 41 percent more biomass than tobacco that hadn’t been modified.
“It’s very exciting” to see how well this genetic tweak worked in tobacco, says Veronica Maurino, a plant physiologist at Heinrich Heine University Düsseldorf in Germany not involved in the research, but “you can’t say, ‘It’s functioning. Now it will function everywhere.’”

Experiments with different types of plants will reveal whether this photorespiration fix creates the same benefits for other crops as it does for tobacco. South’s team is currently running greenhouse experiments on potatoes with the new set of genetic modifications, and plans to do similar tests with soybeans, black-eyed peas and rice.

The vetting process for such genetic modifications to be approved for use on commercial farms, including more field testing, will probably take at least another five to 10 years, says Andreas Weber, a plant biochemist also at Heinrich Heine University Düsseldorf who coauthored a commentary on the study that appears in the same issue of Science. In the meantime, he expects that researchers will continue trying to design even more efficient photorespiration shortcuts, but South’s team “has now set a pretty high bar.”

Marathoners queuing up for a big race tend to go with the flow, surging toward the start line like a fluid.

Using footage of runners moving in groups toward the start of the Chicago Marathon, researchers developed a theory that treats the crowd like a liquid to explain its movement. The theory correctly predicted the motion of crowds of runners at marathons in two other locations, physicists report in the Jan. 4 Science.

Previous studies have devised rules for how individuals act within a crowd and used that behavior to describe crowd motion (SN: 1/10/15, p. 15). But to understand how wine swirls in a glass, you don’t need to know the behavior of each molecule. So physicists Nicolas Bain and Denis Bartolo of École Normale Supérieure de Lyon in France considered the crowd as a whole.

At the start of a marathon, runners arrange themselves into groups known as corrals, which individually advance to the starting line. Marathon staff members form a line in front of each corral, periodically holding participants back until there’s space to move forward. The researchers filmed this start-and-stop process at four marathons, including the Chicago Marathon in 2016 and 2017. The movements of the staff set off a change in crowd density and speed that traveled through the throng akin to waves produced when water is pushed, the team found. Similar effects occurred at marathons in Paris and Atlanta in 2017.

Marathon crowds are a special type in that everyone travels in the same direction. Eventually, this type of research could lead to new insight into other crowd formations, including those packed more tightly than marathon crowds, with pedestrians literally shoulder to shoulder. Such crowds sometimes result in deadly stampedes, such as the 2015 event at the hajj in Mecca, Saudi Arabia (SN: 4/7/07, p. 213). Better understanding of these crowd dynamics could help prevent similar tragedies.

THE WOODLANDS, Texas — Grains of dust from the edge of the solar system could be finding their way to Earth. And NASA may already have a handful of the debris, researchers report.

With an estimated 40,000 tons of space dust settling in Earth’s stratosphere every year, the U.S. space agency has been flying balloon and aircraft missions since the 1970s to collect samples. The particles, which can be just a few tens of micrometers wide, have long been thought to come mostly from comets and asteroids closer to the sun than Jupiter (SN Online: 3/19/19).

But it turns out that some of the particles may have come from the Kuiper Belt, a distant region of icy objects orbiting beyond Neptune, NASA planetary scientist Lindsay Keller said March 21 at the Lunar and Planetary Science Conference. Studying those particles could reveal what distant, mysterious objects in the Kuiper Belt are made of, and perhaps how they formed (SN Online: 3/18/19).

“We’re not going to get a mission out to a Kuiper Belt object to actually collect [dust] samples anytime soon,” Keller said. “But we have samples of these things in the stratospheric dust collections here at NASA.”
One way to find a dust grain’s home is to probe the particle for microscopic tracks where heavy charged particles from solar flares punched through. The more tracks a grain has, the longer it has wandered in space — and the more likely it originated far from Earth, says Keller, who works at the Johnson Space Center in Houston.

But to determine precisely how long a dust grain has spent traveling space, Keller first needed to know how many tracks a grain typically picks up per year. Measuring that rate required a sample with a known age and known track density — criteria met only by moon rocks brought back on the Apollo missions. But the last track-rate estimate was done in 1975 and with less precise instruments than are available today.
So Keller and planetary scientist George Flynn of SUNY Plattsburgh reexamined that same Apollo rock with a modern electron microscope. They found that the rate at which rocks pick up flare tracks was about 20 times lower than the previous study estimated.

That means it takes longer for dust flakes to pick up tracks than astronomers assumed. When Keller and Flynn counted the number of tracks in 14 atmospheric dust grains, the pair found that some of the particles must have spent millions of years out in space — far too long to have come just from between Mars and Jupiter.

Grains specifically from the Kuiper Belt would have wandered 10 million years to reach Earth’s stratosphere, the researchers calculated. That’s “pretty solid evidence that we’re collecting Kuiper Belt dust right here,” Keller says.
Four of the particles contained minerals that had to have formed through interactions with liquid water. That’s surprising; the Kuiper Belt is thought to be too cold for water to be liquid.

“Many of these particles, if they in fact are from the Kuiper Belt, tell you that some of the minerals in Kuiper Belt objects formed in the presence of liquid water,” Keller says. The water probably came from collisions between Kuiper Belt objects that produced enough heat to melt ice, he says.

“I think it’s incredible if Lindsay Keller has shown that he has pieces of Kuiper Belt dust in his lab,” says planetary scientist Carey Lisse of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. But more work needs to be done to confirm that the dust really came from the Kuiper Belt, he says, and wasn’t just sitting on an asteroid for millions of years. “Lindsay needs to get a lot more samples,” Lisse says. “But I do think he’s on to something.”

Lisse works on NASA’s New Horizons mission, which found plenty of dust in the outer solar system and measured its abundance near Pluto when the spacecraft flew past the dwarf planet in 2015. Based on those results, he finds it unsurprising that some of that dust has made it to Earth. But it is “really cool,” he says. “We can actually try to figure out what the Kuiper Belt is made of.”

Editor’s note: This story was updated April 8, 2019, to correct that the newly calculated flare track rate was about 20 times lower than the rate calculated in 1975, not two orders of a magnitude lower.

A drug that treats a rare form of cystic fibrosis may have even better results if given before birth, a study in ferrets suggests.

The drug, known by the generic name ivacaftor, can restore the function of a faulty version of the CFTR protein, called CFTRG551D. The normal CFTR protein controls the flow of charged atoms in cells that make mucus, sweat, saliva, tears and digestive enzymes. People who are missing the CFTR gene and its protein, or have two copies of a damaged version of the gene, develop the lung disease cystic fibrosis, as well as diabetes, digestive problems and male infertility.
Ivacaftor can reduce lung problems in patients with the G551D protein defect, with treatment usually starting when a patient is a year old. But if the results of the new animal study carry over to humans, an even earlier start date could prove more effective in preventing damage to multiple organs.

Researchers used ferret embryos with two copies of the G551D version of the CFTR gene. Giving the drug to mothers while the ferrets were in the womb and then continuing treatment of the babies after birth prevented male infertility, pancreas problems and lung disease in the baby ferrets, called kits, researchers report March 27 in Science Translational Medicine. The drug has to be used continuously to prevent organ damage — when the drug was discontinued, the kits’ pancreases began to fail and lung disease set in.

Cystic fibrosis affects about 30,000 people in the United States and 70,000 worldwide. But only up to 5 percent of patients have the G551D defect.

Other researchers are testing combinations of three drugs, including ivacaftor, aimed at helping the roughly 90 percent of cystic fibrosis patients afflicted by another genetic mutation that causes the CFTR protein to lack an amino acid (SN: 11/24/18, p. 11). Those drug combos, if proven effective, might also work better if administered early, cystic fibrosis researcher Thomas Ferkol of Washington University School of Medicine in St. Louis writes in a commentary published with the study.

Black holes are extremely camera shy. Supermassive black holes, ensconced in the centers of galaxies, make themselves visible by spewing bright jets of charged particles or by flinging away or ripping up nearby stars. Up close, these behemoths are surrounded by glowing accretion disks of infalling material. But because a black hole’s extreme gravity prevents light from escaping, the dark hearts of these cosmic heavy hitters remain entirely invisible.

Luckily, there’s a way to “see” a black hole without peering into the abyss itself. Telescopes can look instead for the silhouette of a black hole’s event horizon — the perimeter inside which nothing can be seen or escape — against its accretion disk. That’s what the Event Horizon Telescope, or EHT, did in April 2017, collecting data that has now yielded the first image of a supermassive black hole, the one inside the galaxy M87.

“There is nothing better than having an image,” says Harvard University astrophysicist Avi Loeb. Though scientists have collected plenty of indirect evidence for black holes over the last half century, “seeing is believing.”

Creating that first-ever portrait of a black hole was tricky, though. Black holes take up a minuscule sliver of sky and, from Earth, appear very faint. The project of imaging M87’s black hole required observatories across the globe working in tandem as one virtual Earth-sized radio dish with sharper vision than any single observatory could achieve on its own.
Putting the ‘solution’ in resolution
Weighing in around 6.5 billion times the mass of our sun, the supermassive black hole inside M87 is no small fry. But viewed from 55 million light-years away on Earth, the black hole is only about 42 microarcseconds across on the sky. That’s smaller than an orange on the moon would appear to someone on Earth. Still, besides the black hole at the center of our own galaxy, Sagittarius A* or Sgr A* — the EHT’s other imaging target — M87’s black hole is the largest black hole silhouette on the sky.
Only a telescope with unprecedented resolution could pick out something so tiny. (For comparison, the Hubble Space Telescope can distinguish objects only about as small as 50,000 microarcseconds.) A telescope’s resolution depends on its diameter: The bigger the dish, the clearer the view — and getting a crisp image of a supermassive black hole would require a planet-sized radio dish.
Even for radio astronomers, who are no strangers to building big dishes (SN Online: 9/29/17), “this seems a little too ambitious,” says Loeb, who was not involved in the black hole imaging project. “The trick is that you don’t cover the entire Earth with an observatory.”
Instead, a technique called very long baseline interferometry combines radio waves seen by many telescopes at once, so that the telescopes effectively work together like one giant dish. The diameter of that virtual dish is equal to the length of the longest distance, or baseline, between two telescopes in the network. For the EHT in 2017, that was the distance from the South Pole to Spain.

Telescopes, assemble!
The EHT was not always the hotshot array that it is today, though. In 2009, a network of just four observatories — in Arizona, California and Hawaii — got the first good look at the base of one of the plasma jets spewing from the center of M87’s black hole (SN: 11/3/12, p. 10). But the small telescope cohort didn’t yet have the magnifying power to reveal the black hole itself.

Over time, the EHT recruited new radio observatories. By 2017, there were eight observing stations in North America, Hawaii, Europe, South America and the South Pole. Among the newcomers was the Atacama Large Millimeter/submillimeter Array, or ALMA, located on a high plateau in northern Chile. With a combined dish area larger than an American football field, ALMA collects far more radio waves than other observatories.

“ALMA changed everything,” says Vincent Fish, an astronomer at MIT’s Haystack Observatory in Westford, Mass. “Anything that you were just barely struggling to detect before, you get really solid detections now.”
More than the sum of their parts
EHT observing campaigns are best run within about 10 days in late March or early April, when the weather at every observatory promises to be the most cooperative. Researchers’ biggest enemy is water in the atmosphere, like rain or snow, which can muddle with the millimeter-wavelength radio waves that the EHT’s telescopes are tuned to.

But planning for weather on several continents can be a logistical headache.

“Every morning, there’s a frenetic set of phone calls and analyses of weather data and telescope readiness, and then we make a go/no-go decision for the night’s observing,” says astronomer Geoffrey Bower of the Academia Sinica Institute of Astronomy and Astrophysics in Hilo, Hawaii. Early in the campaign, researches are picky about conditions. But toward the tail end of the run, they’ll take what they can get.

When the skies are clear enough to observe, researchers steer the telescopes at each EHT observatory toward the vicinity of a supermassive black hole and begin collecting radio waves. Since M87’s black hole and Sgr A* appear on the sky one at a time — each one about to rise just as the other sets — the EHT can switch back and forth between observing its two targets over the course of a single multi-day campaign. All eight observatories can track Sgr A*, but M87 is in the northern sky and beyond the South Pole station’s sight.

On their own, the data from each observing station look like nonsense. But taken together using the very long baseline interferometry technique, these data can reveal a black hole’s appearance.

Here’s how it works. Picture a pair of radio dishes aimed at a single target, in this case the ring-shaped silhouette of a black hole. The radio waves emanating from each bit of that ring must travel slightly different paths to reach each telescope. These radio waves can interfere with each other, sometimes reinforcing one another and sometimes canceling each other out. The interference pattern seen by each telescope depends on how the radio waves from different parts of the ring are interacting when they reach that telescope’s location.
For simple targets, such as individual stars, the radio wave patterns picked up by a single pair of telescopes provide enough information for researchers to work backward and figure out what distribution of light must have produced those data. But for a source with complex structure, like a black hole, there are too many possible solutions for what the image could be. Researchers need more data to work out how a black hole’s radio waves are interacting with each other, offering more clues about what the black hole looks like.

The ideal array has as many baselines of different lengths and orientations as possible. Telescope pairs that are farther apart can see finer details, because there’s a bigger difference between the pathways that radio waves take from the black hole to each telescope. The EHT includes telescope pairs with both north-south and east-west orientations, which change relative to the black hole as Earth rotates.

Pulling it all together
In order to braid together the observations from each observatory, researchers need to record times for their data with exquisite precision. For that, they use hydrogen maser atomic clocks, which lose about one second every 100 million years.

There are a lot of data to time stamp. “In our last experiment, we recorded data at a rate of 64 gigabits per second, which is about 1,000 times [faster than] your home internet connection,” Bower says.

These data are then transferred to MIT Haystack Observatory and the Max Planck Institute for Radio Astronomy in Bonn, Germany, for processing in a special kind of supercomputer called a correlator. But each telescope station amasses hundreds of terabytes of information during a single observing campaign — far too much to send over the internet. So the researchers use the next best option: snail mail. So far, there have been no major shipping mishaps, but Bower admits that mailing the disks is always a little nerve-wracking.

Though most of the EHT data reached Haystack and Max Planck within weeks of the 2017 observing campaign, there were no flights from South Pole until November. “We didn’t get the data back from the South Pole until mid-December,” says Fish, the MIT Haystack astronomer.

Filling in the blanks
Combining the EHT data still isn’t enough to render a vivid picture of a supermassive black hole. If M87’s black hole were a song, then imaging it using only the combined EHT data would be like listening to the piece played on a piano with a bunch of broken keys. The more working keys — or telescope baseline pairs — the easier it is to get the gist of the melody. “Even if you have some broken keys, if you’re playing all the rest of them correctly, you can figure out the tune, and that’s partly because we know what music sounds like,” Fish says. “The reason we can reconstruct images, even though we don’t have 100 percent of the information, is because we know what images look like” in general.
There are mathematical rules about how much randomness any given picture can contain, how bright it should be and how likely it is that neighboring pixels will look similar. Those basic guidelines can inform how software decides which potential images, or data interpretations, make the most sense.

Before the 2017 observing campaign, the EHT researchers held a series of imaging challenges to make sure their computer algorithms weren’t biased toward creating images to match expectations of what black holes should look like. One person would use a secret image to generate faux data of what telescopes would see if they were peering at that source. Then other researchers would try to reconstruct the original image.

“Sometimes the true image was not actually a black hole image,” Fish says, “so if your algorithm was trying to find a black hole shadow … you wouldn’t do well.” The practice runs helped the researchers refine the data processing techniques used to render the M87 image.

Black holes and beyond
So, the black hole inside M87 finally got its closeup. Now what?

The EHT’s black hole observations are expected to help answer questions like how some supermassive black holes, including M87’s, launch such bright plasma jets (SN Online: 3/29/19). Understanding how gas falls into and feeds black holes could also help solve the mystery of how some black holes grew so quickly in the early universe, Loeb says (SN Online: 3/16/18).

The EHT could also be used, Loeb suggests, to find pairs of supermassive black holes orbiting one another — similar to the two stellar mass black holes whose collision created gravitational waves detected in 2015 by the Advanced Laser Interferometer Gravitational-Wave Observatory, or Advanced LIGO (SN: 3/5/16, p. 6). Getting a census of these binaries may help researchers identify targets for the Laser Interferometer Space Antenna, or LISA, which will search from space for gravitational waves kicked up by the movement of objects like black holes (SN Online: 6/20/17).
The EHT doesn’t have many viable targets other than supermassive black holes, says astrophysicist Daniel Marrone, at the University of Arizona in Tucson. There are few other things in the universe that appear as tiny but luminous as the space surrounding a supermassive black hole. “You have to be able to get enough light out of the really tiny patches of sky that we can detect,” Marrone says. “In principle, we could be reading alien license plates or something,” but they’d need to be super bright.

Too bad for alien seekers. Still, even if the EHT is a one-trick pony, spying supermassive black holes is a pretty neat trick.

A new member of the human genus has been found in a cave in the Philippines, researchers report.

Fossils with distinctive features indicate that the hominid species inhabited the island now known as Luzon at least 50,000 years ago, according to a study in the April 11 Nature. That species, which the scientists have dubbed Homo luzonensis, lived at the same time that controversial half-sized hominids named Homo floresiensis and nicknamed hobbits were roaming an Indonesian island to the south called Flores (SN: 7/9/16, p. 6).
In shape and size, some of the fossils match those of corresponding bones from other Homo species. “But if you take the whole combination of features for H. luzonensis, no other Homo species is similar,” says study coauthor and paleoanthropologist Florent Détroit of the French National Museum of Natural History in Paris.

If the find holds up to further scientific scrutiny, it would add to recent fossil and DNA evidence indicating that several Homo lineages already occupied East Asia and Southeast Asian islands by the time Homo sapiens reached what’s now southern China between 80,000 and 120,000 years ago (SN: 11/14/15, p. 15). The result: an increasingly complicated picture of hominid evolution in Asia.

Excavations in 2007, 2011 and 2015 at Luzon’s Callao Cave yielded a dozen H. luzonensis fossils at first — seven isolated teeth (five from the same individual), two finger bones, two toe bones and an upper leg bone missing its ends, the scientists say. Analysis of the radioactive decay of uranium in one tooth suggested a minimum age of 50,000 years. Based on those fossils, a hominid foot bone found in 2007 in the same cave sediment was also identified as H. luzonensis. It dates to at least 67,000 years ago.
had molars that were especially small, even smaller than those of hobbits, with some features similar to modern humans’ molars. The hominid also had relatively large premolars that, surprisingly, had two or three roots rather than one. Hominids dating to several hundred thousand years ago or more, such as Homo erectus , typically had premolars with multiple roots. H. luzonensis finger and toe bones are curved, suggesting a tree-climbing ability comparable to hominids from 2 million years ago or more.
It’s unclear whether H. luzonensis was as small as hobbits, Détroit says. The best-preserved hobbit skeleton comes from a female who stood about a meter tall. Based on the length of the Callao Cave foot bone, Détroit’s team suspects that H. luzonensis was taller than that, although still smaller than most human adults today.

As with hobbits, H. luzonensis’ evolutionary origins are unknown. Scientists think that hobbits may have descended from seagoing H. erectus groups, and perhaps H. luzonensis did too, writes paleoanthropologist Matthew Tocheri of Lakehead University in Thunder Bay, Canada, in a commentary published with the new report. Evidence suggests that hominids reached Luzon by around 700,000 years ago (SN Online: 5/2/18). So H. erectus may have also crossed the sea from other Indonesian islands or mainland Asia to Luzon and then evolved into H. luzonensis with its smaller body and unusual skeletal traits, Détroit speculates, a process known as island dwarfing.

But some scientists not involved in the research say it’s too soon to declare the Luzon fossils a brand-new Homo species. Détroit’s group, so far, has been unable to extract ancient DNA from the fossils. So “all [evolutionary] possibilities must remain open,” says archaeologist Katerina Douka of the Max Planck Institute for the Science of Human History in Jena, Germany.

The mosaic of fossil features that the team interprets as distinctive, for instance, may have been a product of interbreeding between two or more earlier Homo species, creating hybrids, but not a new species.

Or perhaps a small population of, say, H. erectus that survived on an isolated island like Luzon for possibly hundreds of thousands of years simply acquired some skeletal features that its mainland peers lacked, rather than evolving into an entirely new species, says paleoanthropologist María Martinón-Torres.

Those questions make the new fossils “an exciting and puzzling discovery,” says Martinón-Torres, director of the National Research Centre on Human Evolution in Burgos, Spain.

If the unusual teeth and climbing-ready hand and foot bones found at Callao Cave occurred as a package among Luzon’s ancient Homo crowd, “then that combination is unique and unknown so far” among hominids, Martinón-Torres says. Only a more complete set of fossils, ideally complemented by ancient DNA, she adds, can illuminate whether such traits marked a new Homo member.

Look up at the moon and you’ll see roughly the same patterns of light and shadow that Plato saw about 2,500 years ago. But humankind’s understanding of Earth’s nearest neighbor has changed considerably since then, and so have the ways that scientists and others have visualized the moon.

To celebrate the 50th anniversary of the Apollo 11 moon landing, here are a collection of images that give a sense of how the moon has been depicted over time — from hand-drawn illustrations and maps, to early photographs, to highly detailed satellite images made possible by spacecraft such as NASA’s Lunar Reconnaissance Orbiter.
The images, compiled with help from Marcy Bidney, curator of the American Geographical Society Library at the University of Wisconsin–Milwaukee, show how developments in technology such as the telescope and camera drove ever more detailed views of Earth’s closest celestial companion.

1. Atlas Coelestis, Johann Gabriel Doppelmayr, 1742
   Ancient Greek philosophers like Plato thought the moon and other celestial bodies revolved around a fixed Earth. This 1742 diagram by German scientist Johann Gabriel Doppelmayr depicts that idea. The thinkers saw the moon as perfect and struggled to explain its dark marks. In 1935, one of the moon’s most conspicuous craters was named after Plato.
2. Astronomicum Caesareum, Michael Ostendorfer, 1540
   This hand-colored woodcut by German painter Michael Ostendorfer appears in Astronomicum Caesareum, a vast collection of astronomical knowledge compiled by the German author Petrus Apianus and published in 1540. The image is an example of how astronomers in this early Renaissance period began to stylize the moon by giving it a face, Bidney says.

The book also contains more than 20 exquisitely detailed moving paper instruments, or volvelles, that helped predict lunar eclipses, calculate the position of the stars and more.

3. De Mundo, William Gilbert, ca. 1600
   Created around 1600, this sketch is the oldest known lunar map, and was drawn using the naked eye. William Gilbert, physician to Queen Elizabeth I, imagined that the bright spots were seas and the dark spots land, and gave some features names, such as Regio Magna Orientalis, which translates as “Large Eastern Region” and roughly coincides with the vast lava plain known today as Mare Imbrium.
4. Sidereus Nuncius, Galileo, 1610
   The telescope made it far easier to see the moon’s topography. By Galileo, these 1610 lunar maps are some of the first published to rely on telescope views. His work supported the Copernican idea that the moon, Earth and other planets revolved around the sun.

Although Galileo’s moon drawings were not the first to rely on telescope observations — English astronomer Thomas Harriot created the first sketch in 1609 — Galileo’s were the first published. These images appeared in his astronomical treatise Sidereus Nuncius.

5. Selenographia, Johannes Hevelius, 1647
   In 1647, Polish astronomer Johannes Hevelius, published the first lunar atlas, Selenographia. The book contains more than 40 detailed drawings and engravings, including this one, that show the moon in all its phases. Hevelius also included a glossary of 275 named surface features.

To create his images, Hevelius, a wealthy brewer, constructed a rooftop observatory in Gdańsk and fitted it with a homemade telescope that magnified the moon 40 times. Hevelius is credited with founding the field of selenography, the study of the moon’s surface and physical features.

6. First known lunar photo, John William Draper, 1840
   Photography opened a new way to capture the moon. Taken around 1840 by British-born chemist and physician John William Draper, this daguerreotype is the first known lunar photo. Spots are from mold and water damage.
7. “Moon over Hastings”, Henry Draper, 1863
   Photos of the moon quickly improved. John William Draper’s son Henry, a physician like his father, also developed a passion for photographing the night sky. He shot this detailed image from his Hastings-on-Hudson observatory in New York in 1863, and went on to become a pioneer in astrophotography.
8. Lunar Reconnaissance Orbiter, NASA, 2018
   This 2018 image, from NASA’s Lunar Reconnaissance Orbiter, shows the moon’s familiar face in incredible detail. Now we know its marks are evidence of a violent past and include mountain ranges, deep craters and giant basins filled with hardened lava.
9. Lunar farside, Chang’e-4, 2019
   Countless images now exist of the moon’s illuminated face, but only relatively recently have astronomers managed to capture shots of the moon’s farside, using satellites. Then in February, China’s Chang’e-4 lander and rover became the first spacecraft to land there. This is the first image captured by the probe.

By mounting a water distillation system on the back of a solar cell, engineers have constructed a device that doubles as an energy generator and water purifier.

While the solar cell harvests sunlight for electricity, heat from the solar panel drives evaporation in the water distiller below. That vapor wafts through a porous polystyrene membrane that filters out salt and other contaminants, allowing clean water to condense on the other side. “It doesn’t affect the electricity production by the [solar cell]. And at the same time, it gives you bonus freshwater,” says study coauthor Peng Wang, an engineer at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia.
Solar farms that install these two-for-one machines could help meet the increasing global demand for freshwater while cranking out electricity, researchers report online July 9 in Nature Communications.

Using this kind of technology to tackle two big challenges at once “is a great idea,” says Jun Zhou, a materials scientist at Huazhong University of Science and Technology in Wuhan, China, not involved in the work.

In lab experiments under a lamp whose illumination mimics the sun, a prototype device converted about 11 percent of incoming light into electricity. That’s comparable to commercial solar cells, which usually transform some 10 to 20 percent of the sunlight they soak up into usable energy (SN: 8/5/17, p. 22). The researchers tested how well their prototype purified water by feeding saltwater and dirty water laced with heavy metals into the distiller. Based on those experiments, a device about a meter across is estimated to pump out about 1.7 kilograms of clean water per hour.

“It’s really good engineering work,” says George Ni, an engineer who worked on water distillation while a graduate student at MIT, but was not involved in the new study.
“The next step is, how are you going to deploy this?” Ni says. “Is it going to be on a roof? If so, how do you get a source of water to it? If it’s going to be [floating] in the ocean, how do you keep it steady” so that it isn’t toppled by waves? Such practical considerations would need to be hammered out for the device to enter real-world use.

The possibility of life … on other planets has stimulated many people’s i­maginations…. In the Feb. 9 Nature, James C. G. Walker of Yale University studies the possible parameters of such a search and comes to some pessimistic conclusions.

Update
Walker estimated it could take 1,400 to 14 million years to contact E.T. with the available technology. That’s way longer than researchers have spent listening for alien radio signals and scouring the sky with telescopes and satellites (SN: 11/21/20, p. 18).

Despite the silence, scientists have sent their own messages into the void. In 1974, Earth sent a string of binary code from the Arecibo Observatory in Puerto Rico. Years later, arguably the most famous message — the Golden Record — made its way to space aboard NASA spacecraft (SN: 8/20/77, p. 124).

If aliens ever reach out, they may send quantum dispatches, scientists say (SN: 8/13/22, p. 5). Even so, the aliens are likely so far from Earth that their civilization will have collapsed by the time we get the message (SN: 4/14/18, p. 9).

Antarctica’s most vulnerable climate hot spot is a remote and hostile place — a narrow sliver of seawater, beneath a slab of floating ice more than half a kilometer thick. Scientists have finally explored it, and uncovered something surprising.

“The melt rate is much weaker than we would have thought, given how warm the ocean is,” says Peter Davis, an oceanographer at the British Antarctic Survey in Cambridge who was part of the team that drilled a narrow hole into this nook and lowered instruments into it. The finding might seem like good news — but it isn’t, he says. “Despite those low melt rates, we’re still seeing rapid retreat” as the ice vanishes faster than it’s being replenished.
Davis and about 20 other scientists conducted this research at Thwaites Glacier, a massive conveyor belt of ice about 120 kilometers wide, which flows off the coastline of West Antarctica. Satellite measurements show that Thwaites is losing ice more quickly than at any time in the last few thousand years (SN: 6/9/22). It has accelerated its flow into the ocean by at least 30 percent since 2000, hemorrhaging over 1,000 cubic kilometers of ice — accounting for roughly half of the ice lost from all of Antarctica.

Much of the current ice loss is driven by warm, salty ocean currents that are destabilizing the glacier at its grounding zone — the crucial foothold, about 500 meters below sea level at the drilling location, where the ice lifts off its bed and floats (SN: 4/9/21).

Now, this first-ever look at the glacier’s underbelly near the grounding zone shows that the ocean is attacking it in previously unknown and troubling ways.
When the researchers sent a remote-operated vehicle, or ROV, down the borehole and into the water below, they found that much of the melting is concentrated in places where the glacier is already under mechanical stress — within massive cracks called basal crevasses. These openings slice up into the underside of the ice.

Even a small amount of melting at these weak spots could inflict a disproportionately large amount of structural damage on the glacier, the researchers report in two papers published February 15 in Nature.

These results are “a bit of a surprise,” says Ted Scambos, a glaciologist at the University of Colorado Boulder who was not part of the team. Thwaites and other glaciers are monitored mostly with satellites, which make it appear that thinning and melting happen uniformly under the ice.

As the world continues to warm due to human-caused climate change, the shrinking glacier itself has the potential to raise global sea level by 65 centimeters over a period of centuries. Its collapse would also destabilize the remainder of the West Antarctic Ice Sheet, triggering an eventual three meters of global sea level rise.

With these new results, Scambos says, “we’re seeing in much more detail processes that will be important for modeling” how the glacier responds to future warming, and how quickly sea level will rise.

A cold, thin layer shields parts of Thwaites Glacier’s underside
Simply getting these observations “is kind of like a moon shot, or even a Mars shot,” Scambos says. Thwaites, like most of the West Antarctic Ice Sheet, rests on a bed that is hundreds of meters below sea level. The floating front of the glacier, called an ice shelf, extends 15 kilometers out onto the ocean, creating a roof of ice that makes this spot almost entirely inaccessible to humans. “This might represent the pinnacle of exploration” in Antarctica, he says.

These new results stem from a $50 million effort — the International Thwaites Glacier Collaboration — conducted by the United States’ National Science Foundation and United Kingdom’s Natural Environment Research Council. The research team, one of eight funded by that collaboration, landed on the snowy, flat expanse of Thwaites in the final days of 2019.

The researchers used a hot water drill to melt a narrow hole, not much wider than a basketball, through more than 500 meters of ice. Below the ice sat a water column that was only 54 meters thick.

When Davis and his colleagues measured the temperature and salinity of that water, they found that most of it was about 2 degrees Celsius above freezing — potentially warm enough to melt 20 to 40 meters of ice per year. But the underside of the ice seems to be melting at a rate of only 5 meters per year, researchers report in one of the Nature papers. The team calculated the melt rate based on the water’s salinity, which reveals the ratio of seawater, which is salty, to glacial meltwater, which is fresh.

The reason for that slow melt quickly emerged: Just beneath the ice sat a layer of cold, buoyant water, only 2 meters thick, derived from melted ice. “There is pooling of much fresher water at the ice base,” says Davis, and this cold layer shields the ice from warmer water below.

Those measurements provided a snapshot right at the borehole. Several days after the hole was opened, the researchers began a broader exploration of the unmapped ocean cavity under the ice.

Workers winched a skinny, yellow and black cylinder down the borehole. This ROV, called Icefin, was developed over the last seven years by a team of engineers led by Britney Schmidt, a glaciologist at Cornell University.
Schmidt and her team piloted the craft from a nearby tent, monitoring instruments while she steered the craft with gentle nudges to the buttons of a PlayStation 4 controller. The smooth, mirrorlike ceiling of ice scrolled silently past on a computer monitor — the live video feed piped up through 3½ kilometers of fiber-optic cable.

As Schmidt guided Icefin about 1.6 kilometers upstream from the borehole, the water column gradually tapered, until less than a meter of water separated the ice from the seafloor below. A few fish and shrimplike crustaceans called amphipods flitted among otherwise barren piles of gravel.

This new section of seafloor — revealed as the ice thins, lifts and floats progressively farther inland — had been exposed “for less than a year,” Schmidt says.

Now and then, Icefin skimmed past a dark, gaping cleft in the icy ceiling, a basal crevasse. Schmidt steered the craft into several of these gaps — often over 100 meters wide — and there, she saw something striking.

Melting of Thwaites’ underbelly is concentrated in deep crevasses
The vertical walls of the crevasses were scalloped rather than smooth, suggesting a higher rate of melting than that of the flat icy ceiling. And in these places, the video became blurry as the light refracted through vigorously swirling eddies of salty water and freshwater. That turbulent swirling of warm ocean water and cold meltwater is breaking up the cold layer that insulates the ice, pulling warm, salty water into contact with it, the scientists think.

Schmidt’s team calculated that the walls of the crevasses are melting at rates of up to 43 meters per year, the researchers report in the second Nature paper. The researchers also found rapid melt in other places where the level ceiling of ice is punctuated by short, steep sections.

The greater turbulence and higher melt also appear driven by ocean currents within the crevasses. Each time Schmidt steered Icefin up into a crevasse, the ROV detected streams of water flowing through it, as though the crevasse were an upside-down ditch. These currents moved up to twice as fast as the currents outside of crevasses.

The fact that melting is concentrated in crevasses has huge implications, says Peter Washam, an oceanographer on Schmidt’s team at Cornell: “The ocean is widening these features by melting them faster.”

This could greatly accelerate the years-long process by which some of these cracks propagate hundreds of meters up through the ice until they break through at the top — calving off an iceberg that drifts away. It could cause the floating ice shelf, which presses against an undersea mountain and buttresses the ice behind it, to break apart more quickly than predicted. This, in turn, could cause the glacier to spill ice into the ocean more quickly (SN: 12/13/21). “It’s going to have an impact on the stability of the ice,” Washam says.
These new data will improve scientists’ ability to predict the future retreat of Thwaites and other Antarctic glaciers, says Eric Rignot, a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who assisted the team by providing satellite measurements of changes in the glacier. “You just cannot guess what the water structure might look like in these zones until you observe it,” he says.

But more work is needed to fully understand Thwaites and how it will further change as the world continues to warm. The glacier consists of two side-by-side fast-moving lanes of ice — one moving 3 kilometers per year, the other about 1 kilometer per year. Due to safety concerns, the team visited the slower lane — which still proved extremely challenging. Rignot says that scientists must eventually visit the fast lane, whose upper surface is more cracked up with crevasses — making it even harder to land aircraft and operate field camps.

The research reported today “is a very important step, but it needs to be followed by a second step,” the investigation of the glacier’s fast lane, he says. “It doesn’t matter how hard it is.”