Ingenuity is still flying on Mars. Here’s what the helicopter is up to

The Ingenuity Mars helicopter was never supposed to last this long. NASA engineers built and tested the first self-powered aircraft to fly on another planet to answer a simple question: Could the helicopter fly at all? The goal was to take five flights in 30 Martian days or break the aircraft trying.

But more than 120 Martian days past that experiment window, Ingenuity is still flying and doing things no one ever expected. The helicopter, which took its first flight on April 19, is breaking its own records for distance and speed (SN: 4/19/21). It’s helping the Perseverance rover explore Jezero crater, near an ancient river delta that may hold signs of past Martian life (SN: 2/17/21). And Ingenuity is coping with changing seasons and navigating over rough terrain, two things that the flier wasn’t designed to do.

“It’s gotten into a good groove,” says Ingenuity’s original chief engineer Bob Balaram NASA’s Jet Propulsion Lab in Pasadena, Calif. “It’s in its element and having fun.”

Here’s what Ingenuity has been up to on Mars.
Testing the limits
Ingenuity is flying farther, faster and higher than it did in its first few flights. The helicopter has lifted itself a maximum of 12 meters above the Martian surface, zipped along at up to five meters per second (about half as fast as record-setting sprinter Florence Griffith-Joyner) and covered 625 meters (about a third the length of the Kentucky Derby) in a single flight. These extremes give engineers valuable information about the limits of flying on Mars.

“We are still trying to learn lessons,” says JPL robotics engineer Teddy Tzanetos, a team leader for the Ingenuity mission. “Flight after flight, we’re learning the boundaries of performance.”
Early on, Ingenuity tested its limits in a way that the flight team really didn’t plan for. During its sixth flight on May 22, the helicopter’s navigation system suffered a glitch that made it roll and sway alarmingly.

The helicopter’s navigation software keeps track of the craft’s position by taking an image, reading the time stamp on that image and predicting what the camera should see next based on landmarks from previous photos that Ingenuity took. If the next image doesn’t match that prediction, the software corrects the helicopter’s position and velocity to match up better.

Less than a minute into the May 22 flight, a single image got lost on its way from Ingenuity’s cameras to its onboard computer. That meant that the time stamps on all subsequent images were a little off. In trying to correct what it perceived as errors, Ingenuity “went on a wild joyride,” Balaram says.

Luckily, the helicopter touched down safely within five meters of its intended landing spot. The anomaly was a blessing in disguise, Balaram says. It put the helicopter through extremes of movement — “how aggressively you can move the joystick, if you will” — that the engineers would not have asked it to do on purpose, and did perfectly fine, he says.

“It’s a serendipitous thing that we got that flight experience under our belt,” Balaram says. “We have much more confidence in the vehicle.”

Doing science
Originally, the helicopter team wanted to push the vehicle until it broke. But now the researchers are flying more cautiously and less often. That’s because the helicopter is currently supporting the Perseverance rover in doing science (SN: 4/30/21).

“We’re no longer in the Month of Ingenuity,” Tzanetos says. “We’re a small part of a much larger team.”

The helicopter has already proven its worth by telling the rover where not to go. Ingenuity’s ninth flight, on July 5, took the helicopter over a dune field called South Séítah that would have been difficult for the rover to drive through safely. Then, Ingenuity photographed some rock outcrops and raised ridges in South Séítah that had looked interesting in images taken from an orbiting spacecraft. Scientists thought those ridges could record some of the deepest water environments in the lake that filled the crater long ago.
In 3-D images from the helicopter, it turned out that those ridges did not show the layers that would have indicated that the rocks formed in deep water. The rover team decided to move on, saving Perseverance a long, arduous and potentially dangerous drive.

“They didn’t have to send the rover all the way to this particular target, and then realize, hey, this may not be the highest priority thing,” Balaram says.

Scouting for the rover has also taken Ingenuity over terrain that the helicopter wasn’t designed to understand. Ingenuity’s navigation software was programmed to assume that the ground beneath it is always flat because that was the type of terrain selected for that experimental first month of flight demonstrations.

“It was a perfectly reasonable simplification for a technology demonstration,” Balaram says. “But it was baked in. And now you’re stuck with a system with a flat ground assumption.”

When the helicopter is flying over a sloped surface, some features seem to move faster in its view than they would if the ground were flat, giving the helicopter a false sense of its motion. “The onboard navigation has no way of explaining it, except for thinking maybe I’m turning or spinning a bit,” Balaram says. The helicopter ends up veering to the side.

The team has come up with some work-arounds, such as choosing large enough landing zones that a precision landing isn’t necessary and slowing down when flying over rough terrain.

Coping with seasons
The air on Mars is notoriously thin (SN: 7/14/20). But since mid-September, the atmosphere in Jezero crater has been getting even thinner. As that part of Mars shifts from spring to summer, the air density has gone from about 1.5 percent of Earth’s at sea level, to about 1 percent.

That doesn’t sound like a big difference, but it’s enough that Ingenuity has had to spin its rotor blades faster to stay aloft. In October, the helicopter increased its rotor speed to 2,700 revolutions per minute, compared with a previous maximum of 2,537 rpm.
At that faster spin speed, the helicopter can fly for only 130 seconds at a time instead of the 170 seconds it managed before, without running the risk of the motors overheating.

That would be fine if the helicopter was just going to hang around the rover in one area, Tzanetos says. But the Mars duo’s next task is a race to the long-dry river delta at the mouth of Jezero crater. The Perseverance team hopes to cover hundreds of meters each Martian day. The farthest Ingenuity has covered in a day is 625 meters, and that was with the lower spin speed.

“It’ll be challenging to keep up,” Tzanetos says.

There’s no technical reason why Ingenuity can’t make it, though, Balaram says. “It’s certainly possible that one day it just won’t wake up. Or a landing will be a failure and we’ll never hear from it again because it tipped over,” he admits. “Those are rolls of the dice, there’s nothing inevitable about those. Barring that, it should keep working for many months.”

Inspiring future fliers
Meanwhile, engineers are already dreaming of the next Martian aircraft.

“Ingenuity is very exciting, we’re breaking a lot of ground,” Tzanetos says. “The whole point of it is to be that foundation. The important thing is what comes next.”

Current blueprints include a scaled-up version of Ingenuity that could carry more equipment and work alone or with a rover, and a large hexacopter, with six rotors arranged around a central ring. A craft like that could cover more ground more quickly than a rover, traveling distances that could take Perseverance multiple years in just a few months.

A white paper submitted to the 2023–2032 planetary science and astrobiology decadal survey — a once-a-decade review of the fields’ goals and priorities — suggests several possible missions for a Mars Science Helicopter. In one, the craft could take samples of clay minerals at a site like Mawrth Vallis, a channel thought to be carved by a long-ago flood.
Mawrth was a finalist for the last two Mars rover landing sites and is a contender for the European Space Agency’s Rosalind Franklin rover, set to launch in 2022. Clays can preserve organic material on Earth, so a mission to Mawrth could search for signs of life.

A helicopter could also explore craters with water ice deposits with slopes too steep for rover wheels. And by taking measurements at several different altitudes, the helicopter could help figure out how the atmosphere exchanges gases with the ground, which could help solve the mystery of when and how Mars lost its liquid water (SN: 11/12/20). Or a helicopter could map the magnetic field of large swaths of the Martian surface, revealing when and how the Red Planet lost its molten core (SN: 2/24/20).

And whenever astronauts get around to visiting Mars, “it might be useful to have fleets of drones zipping around the skies, carrying loads or scouting ahead,” Tzanetos says. “That’s the exciting future I’m looking forward to.”

2021 research reinforced that mating across groups drove human evolution

Evidence that cross-continental Stone Age networking events powered human evolution ramped up in 2021.

A long-standing argument that Homo sapiens originated in East Africa before moving elsewhere and replacing Eurasian Homo species such as Neandertals has come under increasing fire over the last decade. Research this year supported an alternative scenario in which H. sapiens evolved across vast geographic expanses, first within Africa and later outside it.

The process would have worked as follows: Many Homo groups lived during a period known as the Middle Pleistocene, about 789,000 to 130,000 years ago, and were too closely related to have been distinct species. These groups would have occasionally mated with each other while traveling through Africa, Asia and Europe. A variety of skeletal variations on a human theme emerged among far-flung communities. Human anatomy and DNA today include remnants of that complex networking legacy, proponents of this scenario say.

It’s not clear precisely how often or when during this period groups may have mixed and mingled. But in this framework, no clear genetic or physical dividing line separated Middle Pleistocene folks usually classed as H. sapiens from Neandertals, Denisovans and other ancient Homo populations.
“Middle Pleistocene Homo groups were humans,” says paleoanthropologist John Hawks of the University of Wisconsin–Madison. “Today’s humans are a remix of those ancient ancestors.”

New fossil evidence in line with that idea came from Israel. Braincase pieces and a lower jaw containing a molar tooth unearthed at a site called Nesher Ramla date to between about 140,000 and 120,000 years ago. These finds’ features suggest that a previously unknown Eurasian Homo population lived at the site (SN Online: 6/24/21), a team led by paleoanthropologist Israel Hershkovitz of Tel Aviv University reported. The fossils were found with stone tools that look like those fashioned around the same time by Middle Easterners typically classified as H. sapiens, suggesting that the two groups culturally mingled and possibly mated.

Interactions like these may have facilitated enough mating among mobile Homo populations to prevent Nesher Ramla inhabitants and other Eurasian groups from evolving into separate species, Hershkovitz proposed.

But another report provided a reminder that opinions still vary about whether Middle Pleistocene Homo evolution featured related populations that all belonged to the same species or distinct species. Researchers studying the unusual mix of features of a roughly 146,000-year-old Chinese skull dubbed it a new species, Homo longi (SN Online: 6/25/21). After reviewing that claim, however, another investigator grouped the skull, nicknamed Dragon Man, with several other Middle Pleistocene Homo fossils from northern China.

If so, Dragon Man — like Nesher Ramla Homo — may hail from one of many closely related Homo lines that occasionally mated with each other as some groups moved through Asia, Africa and Europe. From this perspective, Middle Pleistocene Homo groups evolved unique traits during periods of isolation and shared features as a result of crossing paths and mating.
Back-and-forth migrations by Homo groups between Africa and Asia started at least 400,000 years ago, discoveries in Saudi Arabia suggest (SN: 10/9/21 & 10/23/21, p. 7). Monsoon rains periodically turned what’s now desert into a green passageway covered by lakes, wetlands and rivers, reported archaeologist Huw Groucutt of the Max Planck Institute for the Science of Human History in Jena, Germany, and colleagues. Each of five ancient lake beds identified at a Saudi site once hosted hunter-gatherers who left behind stone tools.

Occupations occurred intermittently between about 400,000 and 55,000 years ago. By about 200,000 years ago, stone tools at one of the lake beds resembled those made around the same time by H. sapiens in northeastern Africa. Some of those Africans may have stopped for a bit in a green Arabia before trekking into southwestern Asia, Groucutt suggests.

Either H. sapiens or Neandertals made stone tools unearthed in the youngest lake bed. Neandertals inhabited parts of the Middle East by around 70,000 years ago and could have reached a well-watered Arabia by 55,000 years ago. If that’s what happened, Neandertals may have mated with H. sapiens already there, Groucutt speculates.

Although Arabian hookups have yet to be detected in ancient DNA, European Neandertals and H. sapiens mated surprisingly often around 45,000 years ago (SN: 5/8/21 & 5/22/21, p. 7), other scientists reported. DNA extracted from H. sapiens fossils of that age found in Bulgaria and the Czech Republic indicates that these ancient individuals possessed between about 2 percent and 4 percent Neandertal ancestry, a large amount considering H. sapiens migrants had only recently arrived in Europe.

So even after the Middle Pleistocene, networking among ancient Homo groups may have helped make us who we are today.

The cosmic ‘Cow’ may have produced a new neutron star or black hole

A cosmic flare-up called the Cow seems to have left behind a black hole or neutron star.

When the flash was spotted in June 2018, astronomers debated its origins. Now, astrophysicist DJ Pasham of MIT and colleagues have seen the first direct evidence of what the Cow left behind. “We may be seeing the birth of a black hole or neutron star,” Pasham says.

The burst’s official, random designation is AT2018cow, but astronomers affectionately dubbed it the Cow. The light originated about 200 million light-years away and was 10 times as bright as an ordinary supernova, the explosion that marks the death of a massive star.

Astronomers thought the flare-up could have been from an unusual star being eaten by a black hole or from a weird sort of supernova that left behind a black hole or neutron star (SN: 6/21/19).

So Pasham and colleagues checked the Cow for flickering X-rays, which are typically produced close to a compact object, possibly in a disk of hot material around a black hole or on the surface of a neutron star.

Flickers in these X-rays can reveal the size of their source. The Cow’s X-rays flicker roughly every 4 milliseconds, meaning the object that produces them must be no more than 1,000 kilometers wide. Only a neutron star or a black hole fits the bill, Pasham and colleagues report December 13 in Nature Astronomy.

Because the Cow’s flash was from the explosion that produced either of these objects, a preexisting black hole was probably not responsible for the burst. Pasham admits he was hoping for a black hole eating an exotic star. “I was a little bit disappointed,” he says. “But I’m more blown away that this could be direct evidence of the birth of a black hole. This is an even cooler result.”

Australian fires in 2019–2020 had even more global reach than previously thought

The severe, devastating wildfires that raged across southeastern Australia in late 2019 and early 2020 packed a powerful punch that extended far beyond the country, two new studies find.

The blazes injected at least twice as much carbon dioxide into the atmosphere as was previously thought, one team’s satellite-derived estimates revealed. The fires also sent up vast clouds of smoke and ash that wafted far to the east over the Southern Ocean, fertilizing the waters with nutrients and triggering widespread blooms of microscopic marine algae called phytoplankton, another team found. Both studies were published online September 15 in Nature.

Meteorologist Ivar van der Velde of the SRON Netherlands Institute for Space Research in Leiden and colleagues first examined carbon monoxide data collected over southeastern Australia by the satellite-based instrument TROPOMI from November 2019 to January 2020, during the worst of the fires. Then, to get new estimates of the carbon dioxide emissions attributable to the fires, the team used previously determined ratios of carbon monoxide to carbon dioxide emitted by the region’s eucalyptus forests — the predominant type of forest that was scorched in the blazes — during earlier wildfires and prescribed burns.

Van der Velde’s team estimates that the fires released from 517 trillion to 867 trillion grams of carbon dioxide to the atmosphere. “The sheer magnitude of CO2 that was emitted to the atmosphere … was much larger than what we initially thought it would be,” van der Velde says. The emissions “from this single event were significantly higher than what all Australians normally emit with the combustion of fossil fuels in an entire year.”
Previous assessments of CO2 emissions from the fires, based on estimations of burned area and biomass consumed by the blazes, calculated an average of about 275 trillion grams. Using the satellite-derived carbon monoxide data, the researchers say, dramatically improves the ability to distinguish actual emissions from the fires from other background sources of the gases, giving a more accurate assessment.

That finding has worrisome implications. The fires swiftly cut a swath through southeastern Australia’s eucalyptus forests, devastating the forests to a degree that made their rapid recovery more difficult — which in turn affects how much carbon the trees can sequester, van der Velde says (SN: 3/9/21). Fires in northern and central Australia’s dry, grassy savannas are seen as more climate neutral because the grasses can regrow more quickly, he says.

And severe fire seasons are likely to become more common in southeastern Australia with ongoing climate change. Climate change has already increased the likelihood of severe fire events such as the 2019–2020 fire season by at least 30 percent (SN: 3/4/20).

The smoke and ash from the fires also packed a powerful punch. Scientists watched in awe as the fires created a “super outbreak” of towering thunderclouds from December 29 to December 31 in 2019 (SN: 12/15/20). These clouds spewed tiny aerosol particles of ash and smoke high into the stratosphere.

Aerosols from the fires also traveled eastward through the lower atmosphere, ultimately reaching the Southern Ocean where they triggered blooms of phytoplankton in its iron-starved waters. Geochemist Weiyi Tang, now at Princeton University, and colleagues analyzed aerosols from the fires and found the particles to be rich in iron, an important nutrient for the algae. By tracing the atmospheric paths of the cloud of ash and smoke across the ocean, the team was able to link the observed blooms — huge patches of chlorophyll detected by satellite — to the fires.
Researchers have long thought that fires can trigger ocean blooms, particularly in the Southern Ocean, under the right conditions, says marine biogeochemist Joan Llort, now at the Barcelona Supercomputing Center and a coauthor on the study. But this research marks the most direct observation ever made of such an event — in part because it was such a massive one, Llort says.

Large ocean blooms are “yet another process which is potentially being modified by climate change,” says biogeochemist Nicolas Cassar of Duke University, also a coauthor on the study.

One of the big questions to emerge from the study, Cassar adds, is just how much carbon these phytoplankton may have ultimately removed from the atmosphere as they bloomed. Some of the carbon that the algae draw out of the air through photosynthesis sinks with them to the seafloor as they die. But some of it is quickly respired back to the atmosphere, muting any mitigating effect that the blooms might have on the wildfire emissions. To really assess what role the algae play, he says, would require a rapid-response team aboard an ocean vessel that could measure these chemical processes as they are happening.

The sheer size of this wildfire-triggered bloom — “larger than Australia itself” — shows that “wildfires have the potential to increase marine productivity by very large amounts,” says Douglas Hamilton, a climate scientist at Cornell University who was not connected with the study.

“The impact of fires on society is not straightforward,” Hamilton adds. The same smoke that can cause severe health impacts when inhaled “is also supplying nutrients to ecosystems and helping support marine food webs.” What this study demonstrates, he adds, is that to understand how future increases in fire activity might help shape the future of marine productivity “it is crucial that we monitor the impacts closely now.”

Rice feeds half the world. Climate change’s droughts and floods put it at risk

under a midday summer sun in California’s Sacramento Valley, rice farmer Peter Rystrom walks across a dusty, barren plot of land, parched soil crunching beneath each step.

In a typical year, he’d be sloshing through inches of water amid lush, green rice plants. But today the soil lies naked and baking in the 35˚ Celsius (95˚ Fahrenheit) heat during a devastating drought that has hit most of the western United States. The drought started in early 2020, and conditions have become progressively drier.

Low water levels in reservoirs and rivers have forced farmers like Rystrom, whose family has been growing rice on this land for four generations, to slash their water use.

Rystrom stops and looks around. “We’ve had to cut back between 25 and 50 percent.” He’s relatively lucky. In some parts of the Sacramento Valley, depending on water rights, he says, farmers received no water this season.

California is the second-largest U.S. producer of rice, after Arkansas, and over 95 percent of California’s rice is grown within about 160 kilometers of Sacramento. To the city’s east rise the peaks of the Sierra Nevada, which means “snowy mountains” in Spanish. Rice growers in the valley below count on the range to live up to its name each winter. In spring, melting snowpack flows into rivers and reservoirs, and then through an intricate network of canals and drainages to rice fields that farmers irrigate in a shallow inundation from April or May to September or October.

If too little snow falls in those mountains, farmers like Rystrom are forced to leave fields unplanted. On April 1 this year, the date when California’s snowpack is usually at its deepest, it held about 40 percent less water than average, according to the California Department of Water Resources. On August 4, Lake Oroville, which supplies Rystrom and other local rice farmers with irrigation water, was at its lowest level on record.
Not too long ago, the opposite — too much rain — stopped Rystrom and others from planting. “In 2017 and 2019, we were leaving ground out because of flood. We couldn’t plant,” he says. Tractors couldn’t move through the muddy, clay-rich soil to prepare the fields for seeding.

Climate change is expected to worsen the state’s extreme swings in precipitation, researchers reported in 2018 in Nature Climate Change. This “climate whiplash” looms over Rystrom and the other 2,500 or so rice producers in the Golden State. “They’re talking about less and less snowpack, and more concentrated bursts of rain,” Rystrom says. “It’s really concerning.”

Farmers in China, India, Bangladesh, Indonesia, Vietnam — the biggest rice-growing countries — as well as in Nigeria, Africa’s largest rice producer — also worry about the damage climate change will do to rice production. More than 3.5 billion people get 20 percent or more of their calories from the fluffy grains. And demand is increasing in Asia, Latin America and especially in Africa.

To save and even boost production, rice growers, engineers and researchers have turned to water-saving irrigation routines and rice gene banks that store hundreds of thousands of varieties ready to be distributed or bred into new, climate-resilient forms. With climate change accelerating, and researchers raising the alarm about related threats, such as arsenic contamination and bacterial diseases, the demand for innovation grows.

“If we lose our rice crop, we’re not going to be eating,” says plant geneticist Pamela Ronald of the University of California, Davis. Climate change is already threatening rice-growing regions around the world, says Ronald, who identifies genes in rice that help the plant withstand disease and floods. “This is not a future problem. This is happening now.”
Saltwater woes
Most rice plants are grown in fields, or paddies, that are typically filled with around 10 centimeters of water. This constant, shallow inundation helps stave off weeds and pests. But if water levels suddenly get too high, such as during a flash flood, the rice plants can die.

Striking the right balance between too much and too little water can be a struggle for many rice farmers, especially in Asia, where over 90 percent of the world’s rice is produced. Large river deltas in South and Southeast Asia, such as the Mekong River Delta in Vietnam, offer flat, fertile land that is ideal for farming rice. But these low-lying areas are sensitive to swings in the water cycle. And because deltas sit on the coast, drought brings another threat: salt.

Salt’s impact is glaringly apparent in the Mekong River Delta. When the river runs low, saltwater from the South China Sea encroaches upstream into the delta, where it can creep into the soils and irrigation canals of the delta’s rice fields.

“If you irrigate rice with water that’s too salty, especially at certain [growing] stages, you are at risk of losing 100 percent of the crop,” says Bjoern Sander, a climate change specialist at the International Rice Research Institute, or IRRI, who is based in Vietnam.

In a 2015 and 2016 drought, saltwater reached up to 90 kilometers inland, destroying 405,000 hectares of rice paddies. In 2019 and 2020, drought and saltwater intrusion returned, damaging 58,000 hectares of rice. With regional temperatures on the rise, these conditions in Southeast Asia are expected to intensify and become more widespread, according to a 2020 report by the Economic and Social Commission for Asia and the Pacific.

Then comes the whiplash: Each year from around April to October, the summer monsoon turns on the faucet over swaths of South and Southeast Asia. About 80 percent of South Asia’s rainfall is dumped during this season and can cause destructive flash floods.

Bangladesh is one of the most flood-prone rice producers in the region, as it sits at the mouths of the Ganges, Brahmaputra and Meghna rivers. In June 2020, monsoon rains flooded about 37 percent of the country, damaging about 83,000 hectares of rice fields, according to Bangladesh’s Ministry of Agriculture. And the future holds little relief; South Asia’s monsoon rainfall is expected to intensify with climate change, researchers reported June 4 in Science Advances.
A hot mess
Water highs and lows aren’t the entire story. Rice generally grows best in places with hot days and cooler nights. But in many rice-growing regions, temperatures are getting too hot. Rice plants become most vulnerable to heat stress during the middle phase of their growth, before they begin building up the meat in their grains. Extreme heat, above 35˚ C, can diminish grain counts in just weeks, or even days. In April in Bangladesh, two consecutive days of 36˚ C destroyed thousands of hectares of rice.

In South and Southeast Asia, such extreme heat events are expected to become common with climate change, researchers reported in July in Earth’s Future. And there are other, less obvious, consequences for rice in a warming world.

One of the greatest threats is bacterial blight, a fatal plant disease caused by the bacterium Xanthomonas oryzae pv. oryzae. The disease, most prevalent in Southeast Asia and rising in Africa, has been reported to have cut rice yields by up to 70 percent in a single season.

“We know that with higher temperature, the disease becomes worse,” says Jan Leach, a plant pathologist at Colorado State University in Fort Collins. Most of the genes that help rice combat bacterial blight seem to become less effective when temperatures rise, she explains.

And as the world warms, new frontiers may open for rice pathogens. An August study in Nature Climate Change suggests that as global temperatures rise, rice plants (and many other crops) at northern latitudes, such as those in China and the United States, will be at higher risk of pathogen infection.

Meanwhile, rising temperatures may bring a double-edged arsenic problem. In a 2019 study in Nature Communications, E. Marie Muehe, a biogeochemist at the Helmholtz Centre for Environmental Research in Leipzig, Germany, who was then at Stanford University, showed that under future climate conditions, more arsenic will infiltrate rice plants. High arsenic levels boost the health risk of eating the rice and impair plant growth.
Arsenic naturally occurs in soils, though in most regions the toxic element is present at very low levels. Rice, however, is particularly susceptible to arsenic contamination, because it is grown in flooded conditions. Paddy soils lack oxygen, and the microbes that thrive in this anoxic environment liberate arsenic from the soil. Once the arsenic is in the water, rice plants can draw it in through their roots. From there, the element is distributed throughout the plants’ tissues and grains.

Muehe and her team grew a Californian variety of rice in a local low-arsenic soil inside climate-controlled greenhouses. Increasing the temperature and carbon dioxide levels to match future climate scenarios enhanced the activity of the microbes living in the rice paddy soils and increased the amount of arsenic in the grains, Muehe says. And importantly, rice yields diminished. In the low-arsenic Californian soil under future climate conditions, rice yield dropped 16 percent.

According to the researchers, models that forecast the future production of rice don’t account for the impact of arsenic on harvest yields. What that means, Muehe says, is that current projections are overestimating how much rice will be produced in the future.

Managing rice’s thirst
From atop an embankment that edges one of his fields, Rystrom watches water gush from a pipe, flooding a paddy packed with rice plants. “On a year like this, we decided to pump,” he says.

Able to tap into groundwater, Rystrom left only about 10 percent of his fields unplanted this growing season. “If everybody was pumping from the ground to farm rice every year,” he admits, it would be unsustainable.

One widely studied, drought-friendly method is “alternate wetting and drying,” or intermittent flooding, which involves flooding and draining rice paddies on one- to 10-day cycles, as opposed to maintaining a constant inundation. This practice can cut water use by up to 38 percent without sacrificing yields. It also stabilizes the soil for harvesting and lowers arsenic levels in rice by bringing more oxygen into the soils, disrupting the arsenic-releasing microbes. If tuned just right, it may even slightly improve crop yields.

But the water-saving benefits of this method are greatest when it is used on highly permeable soils, such as those in Arkansas and other parts of the U.S. South, which normally require lots of water to keep flooded, says Bruce Linquist, a rice specialist at the University of California Cooperative Extension. The Sacramento Valley’s clay-rich soils don’t drain well, so the water savings where Rystrom farms are minimal; he doesn’t use the method.

Building embankments, canal systems and reservoirs can also help farmers dampen the volatility of the water cycle. But for some, the solution to rice’s climate-related problems lies in enhancing the plant itself.
Better breeds
The world’s largest collection of rice is stored near the southern rim of Laguna de Bay in the Philippines, in the city of Los Baños. There, the International Rice Genebank, managed by IRRI, holds over 132,000 varieties of rice seeds from farms around the globe.

Upon arrival in Los Baños, those seeds are dried and processed, placed in paper bags and moved into two storage facilities — one cooled to 2˚ to 4˚ C from which seeds can be readily withdrawn, and another chilled to –20˚ C for long-term storage. To be extra safe, backup seeds are kept at the National Center for Genetic Resources Preservation in Fort Collins, Colo., and the Svalbard Global Seed Vault tucked inside a mountain in Norway.

All this is done to protect the biodiversity of rice and amass a trove of genetic material that can be used to breed future generations of rice. Farmers no longer use many of the stored varieties, instead opting for new higher-yield or sturdier breeds. Nevertheless, solutions to climate-related problems may be hidden in the DNA of those older strains. “Scientists are always looking through that collection to see if genes can be discovered that aren’t being used right now,” says Ronald, of UC Davis. “That’s how Sub1 was discovered.”
The Sub1 gene enables rice plants to endure prolonged periods completely submerged underwater. It was discovered in 1996 in a traditional variety of rice grown in the Indian state of Orissa, and through breeding has been incorporated into varieties cultivated in flood-prone regions of South and Southeast Asia. Sub1-wielding varieties, called “scuba rice,” can survive for over two weeks entirely submerged, a boon for farmers whose fields are vulnerable to flash floods.

Some researchers are looking beyond the genetic variability preserved in rice gene banks, searching instead for useful genes from other species, including plants and bacteria. But inserting genes from one species into another, or genetic modification, remains controversial. The most famous example of genetically modified rice is Golden Rice, which was intended as a partial solution to childhood malnutrition. Golden Rice grains are enriched in beta-carotene, a precursor to vitamin A. To create the rice, researchers spliced a gene from a daffodil and another from a bacterium into an Asian variety of rice.

Three decades have passed since its initial development, and only a handful of countries have deemed Golden Rice safe for consumption. On July 23, the Philippines became the first country to approve the commercial production of Golden Rice. Abdelbagi Ismail, principal scientist at IRRI, blames the slow acceptance on public perception and commercial interests opposed to genetically modified organisms, or GMOs (SN: 2/6/16, p. 22).

Looking ahead, it will be crucial for countries to embrace GM rice, Ismail says. Developing nations, particularly those in Africa that are becoming more dependent on the crop, would benefit greatly from the technology, which could produce new varieties faster than breeding and may allow researchers to incorporate traits into rice plants that conventional breeding cannot. If Golden Rice were to gain worldwide acceptance, it could open the door for new genetically modified climate- and disease-resilient varieties, Ismail says. “It will take time,” he says. “But it will happen.”

Climate change is a many-headed beast, and each rice-growing region will face its own particular set of problems. Solving those problems will require collaboration between local farmers, government officials and the international community of researchers.

“I want my kids to be able to have a shot at this,” Rystrom says. “You have to do a lot more than just farm rice. You have to think generations ahead.”

Cold plasma could transform the sustainable farms of the future

Physicist Stephan Reuter of Polytechnique Montréal spends most days using his expertise in energy and matter to improve medical technologies. Recently though, he stood in a sea of green to consider how a shower of charged particles might affect lettuce.

He had been invited to one of the largest commercial greenhouses in Quebec to help the growers rethink the energy of agriculture. Inside the building, encased by glass walls and covering more ground than four soccer fields, thousands upon thousands of lettuce plants floated on polystyrene mats in a hydroponic, or no-soil, growing system. The crop was nearly ready to be picked, packaged and shipped. Reuter’s task was to use physics to help the company, Hydroserre Inc. in Mirabel, reduce its carbon footprint.

To that end, the company is interested in finding new ways to fight pathogens and to deliver fertilizer to the growing plants. Many fertilizers contain ammonia, which is produced from nitrogen (necessary for plant growth) and hydrogen using a chemical reaction called the Haber-Bosch process. This process revolutionized agriculture in the early 20th century by making mass production of fertilizer possible. However, the process yields hundreds of millions of metric tons of carbon dioxide each year.

“Ideally, we want a fertilizer that’s renewable,” Reuter says. And to make it truly green, it should be created at the farm, making transport, another carbon emitter, unnecessary. Reuter and a growing number of chemists, physicists and engineers think they can see how to make that happen. These researchers are working toward future farms that are truly sustainable, where the energy from renewable sources like wind or solar is harnessed to make an efficient fertilizer on-site. They hope to realize this vision by exploiting plasma.
Reuter might seem an unlikely consultant for an agricultural challenge. After all, his expertise is in the physics of plasma, one of the four fundamental states of matter, along with solids, liquids and gases.

Plasma is remarkably common. In fact, most matter seen in the known universe — more than 99.9 percent, according to astrophysicists — is in a plasma state. Lightning produces plasma. So do those inexpensive novelty lamps in museum gift shops. Switch on the power, and an electrode at the sphere’s center produces a high voltage that interacts with the gas sealed inside the glass to form tendrils of colored plasma that radiate outward. Touch the glass, and the plasma tendrils seem to reach toward your fingers.

The sun is a ball of plasma and gas. The solar wind is a stream of plasma that peels off the sun (SN: 12/21/19 & 1/4/20, p. 6). When that wind collides with the protective, plasma-rich magnetic cushion that envelopes Earth, the interactions produce rivers of light seen in the aurora borealis and aurora australis.

Plasma is also a workhorse of modern technology. Engineers use it to etch the millions of tiny transistors found on the chips in today’s computers, cars and musical birthday cards. The pixels in plasma televisions contain gas that forms a plasma, sealed inside tiny cells sandwiched between two glass plates, and neon signs and fluorescent lights glow because of plasma. Some former astronauts even predict that plasma engines will someday propel us to Mars.

But what exactly is plasma? It’s a soup of electrons with their negative charges, positive ions and neutral atoms that also produces electromagnetic fields and ultraviolet and infrared radiation. Plasma comes about when gas gets super energized — by heat or an electric current, for example — and electrons are freed from atoms.

Plasmas occur naturally or can be human-made. When produced by high temperatures, such as in the sun, it’s called “hot plasma,” while the plasma created in a plasma ball and other room-temperature, low-pressure environments is called “cold plasma.” Plasma balls make it easy to see: They’re filled with a gaseous mixture that includes one of the very stable, noble gases, like argon, xenon, neon or krypton. Plasma makes up those glowing tendrils that reach out from the center. The high-frequency current excites electrons that then separate from the atoms of gas. Many agricultural experiments include a mix of noble gases and air to yield ions of nitrogen and oxygen.
Scientists have long been interested in plasma’s biological implications. In the late 19th century, the Finnish physicist Karl Selim Lemström observed that the width of growth rings in fir trees near the Arctic Circle followed the cycle of the aurora borealis, widening when the northern lights were strongest. He hypothesized that the light show somehow encouraged plant growth. To artificially emulate the northern lights, he placed a metal wire net over growing plants and ran a current through it. Under the right conditions, he reported, the treatment produced larger vegetable yields.

For decades, scientists have known that exposure to plasma can safely kill pathogenic bacteria, fungi and viruses. Small studies in animals also suggest that plasma can prompt the growth of blood vessels in skin. In his research, Reuter studies ways to harness these properties to inhibit new infections in wounds and expedite healing or treat other skin conditions. But more recently, he and other physicists have been working on ways to use the power of plasma to improve food production.

Experiments conducted in the last decade or so have tested a mix of ways to apply plasma to seeds, seedlings, crops and fields. These include plasma generated using noble gases, as well as plasma generated from air. In some cases, plasma is directly applied through plasma “jets” that stream over the seeds or plants. Another approach uses plasma-treated water that can do double duty: irrigation and fertilization. Some studies have reported a range of benefits, from helping plants grow faster and bigger to resisting pests.

“Even in this very, very early stage of research that we’re at with plasma, which has really only come into its own in the last 10 to 15 years, we’re seeing very promising data,” says plant pathologist Brendan Niemira at the Food Safety and Intervention Technologies Research unit at the U.S. Department of Agriculture’s Eastern Regional Research Center in Wyndmoor, Pa. He’s a fan of the approach: On Zoom, Niemira’s avatar shows an almond basking in an eerie, purple plasma glow.

The challenge now, he says, is to figure out whether plasma can deliver at the level of hectares of crops. “Can we make it work in a field environment [to] deliver an advantage that can be integrated into grow systems in the future?”

Nested within that challenge are many others, including finding a way to deliver plasma to plants on a large scale, confirming benefits reported in lab studies and showing that plasma is better than current methods. And, finally, figuring out what the charged soup of plasma is actually doing to plants.

Recent advances became possible, Niemira says, largely because in the 1990s and early 2000s, scientists developed efficient and cost-effective ways to generate cold plasmas by streaming high-energy electrons into a gas. Those electrons would collide with gas molecules, knocking off electrons and producing charged particles. Since then, he says, there’s been something of a rush to test plasma on plants at all stages of growth and with a range of strategies.
Surface changes
One of the most appealing uses of plasma, according to Reuter, is as a fertilizer alternative to ammonia. His plan for the Mirabel greenhouse project, which he helped launch in spring 2021 with scientists from the Quebec-based nonprofit IRDA, or Research and Development Institute for the Agri-Environment, goes something like this: The plasma is generated by sending an electric current through a gas that, ideally, is just air. That process creates a mix of charged and neutral particles, including electrons and ions, that can produce reactive species of nitrogen and oxygen. In tabletop experiments and then in the greenhouse, Reuter and his colleagues will enrich water with plasma, then study whether it can reduce pathogens and affect the growing plants.

Reactive species, as the name implies, are ready to react with atoms and molecules, including in living things, and are biologically available to plants. When the plasma is added to the water, those reactive species dissolve. The resulting plasma-infused water, with its biologically available nitrogen, will then be used to irrigate the plants. It will do the same job as ammonia: Nitrogen, which plants require for growth, is delivered as ions, excited molecules and compounds in the water. While heavy doses of reactive species can harm plant cells or DNA, the amount in plasma-treated water has been shown to be safe for the plant, Reuter says.
Experiments led by biochemist Alexander Volkov of Oakwood University in Huntsville, Ala., offer another example of the kind of research going on in plasma agriculture. Volkov studies the ways in which plants and electromagnetism interact. For example, he’s shown how an electric stimulus can trigger the closing mechanism on a Venus flytrap.

Recently, Volkov set out to study how plasma would affect 20 seeds of dragon’s-tongue, a cultivar of the bush bean Phaseolus vulgaris. The experiment was low-tech. He and colleagues balanced the seeds on a plasma ball for one minute each, then incubated the seeds in water for seven hours. Two days later, the scientists found that in plasma-treated seeds, the radicle — the little protrusion of root that makes a seed a seedling — measured 2.7 centimeters, compared with 1.8 centimeters in untreated seeds, a gain of 50 percent. The team reported the results in Functional Plant Biology in February 2021.
Less than a centimeter of extra growth may seem modest, but Volkov was encouraged. The benefit couldn’t have come from the reactive species of nitrogen and oxygen because they can’t exit the glass sphere, but somehow, the treated seeds seemed to take up more water to grow faster.

To investigate that idea, he and colleagues studied the seeds using an atomic force microscope and magnetic resonance imaging, which reveals how tissues take up water. At the micrometer-level view of the atomic force microscope, Volkov saw that exposure had roughed up the surface of the seeds. The images looked like carved mountain ranges. Those ridges gave the water more surface area to glom on to, and more openings through which to soak the inside of the seeds, he hypothesized. MRI images of treated beans showed larger swaths of white — indicating more water inside — than untreated beans.

“When we use the plasma balls or lamps, the water can penetrate easily through the pores and accelerate germination,” he says.
Growing evidence
Physicist Nevena Puač of the Institute of Physics Belgrade in Serbia has performed dozens of studies testing plasma on plants and has been working in the field for decades. She says most studies — successful or not — have tested two ideas: plasma as a disinfectant or as a growth instigator.

On the disinfecting front, plasma jet treatments of less than a minute on foods including apples, cherry tomatoes and lettuce can reduce disease-causing bacteria, such as Escherichia coli, Salmonella and Listeria. Some studies have looked at higher exposure times as well: In a 2008 study, five minutes of plasma treatment inactivated 90 percent of pathogenic Aspergillus parasiticus fungi on hazelnuts, peanuts and pistachios.

This is the research branch that Niemira works on as well. In May 2019 in LWT–Food Science and Technology, he and colleagues showed that plasma treatment combined with an existing sanitizer killed 99.9 percent of Listeria on apples in under four minutes. Working alone, the sanitizer achieved comparable results after an hour. The combination works much better than either one could possibly work alone, he says.

Investigations on seed germination and plant growth are similarly promising. Researchers at the Chinese Academy of Sciences in Nanjing exposed soybean seeds to plasma. Seven days after exposure, the roots were up to 27 percent heavier than roots from untreated seeds, the team reported in 2014. The same year, researchers in Romania reported similar gains for radish roots and sprouts.

At last year’s Gaseous Electronics Conference, hosted online by the American Physical Society, researchers from Japan presented results from a study of young seedlings treated directly with plasma and with plasma-treated water in a rice paddy in the Aichi prefecture. Plants treated directly with plasma early in the growth process had up to a 15 percent higher yield than untreated plants. But treating plants late in the growth process lowered the yield. Timing matters, Puač says. So does the application method: In some cases in the experiments in Japan, plasma-treated water actually lowered the yield.

“To my knowledge this was the first study where plants were treated directly,” rather than as seeds or after harvest for disinfection, says engineer Katharina Stapelmann of North Carolina State University in Raleigh, who organized the session.

Studies have connected plasma treatment to a range of benefits, Puač says, from growth rate to yield. But other studies suggest that plasma won’t ever be a one-size-fits-all technology.

Researchers in South Korea reported in the Journal of Physics D: Applied Physics in 2020, for example, that while a six-minute plasma exposure boosted germination rates of barley sprouts, an 18-minute exposure, over three days, produced no benefit in growth and lowered total plant weight. Experimental results published in 2000 looked at the effects of direct plasma jets on peas, corn and radishes and found detrimental effects that varied by the gas used in the plasma. The seeds were exposed for two to 20 minutes, and seeds with prolonged exposure were slower to germinate than untreated seeds.
What the research shows, Reuter says, is that before plasma becomes a staple on farms around the world, scientists need to better understand the myriad ways that the fourth state of matter could affect plants.

For instance, successful outcomes for plants might be due in part to the UV radiation produced by plasma; UV radiation has long been used as a disinfectant. The reactive nitrogen and oxygen species, which can be helpful or harmful to living cells depending on how they’re used, probably help as nutrients and disinfectants, as well. Plasma also produces electric and magnetic fields and infrared and visible light. Their impact on plants also hasn’t been fully explored. Even though researchers know what’s in the plasma, and can see how the plants respond, they don’t have the details mapped out, Volkov says.

Gardens big and small
Projects are under way around the world to test plasma on large scales and in different settings. Dutch scientists working in Uganda have developed portable “reactors” that use plasma to generate fertilizers from the air. They hope this invention can meet the need for fertilizers in places where farmers often can’t get ammonia. Early in 2022, Reuter hopes to report his first results from desktop experiments. The hydroponic growing system at Hydroserre will provide him with the opportunity to refine his method.

With any luck, he says, the project will show a way for future farms to replace ammonia and reduce carbon emissions.

While researchers and growers await those results, citizen scientists, amateur physicists and experimental gardeners have been known to make space in the shed for a plasma ball next to their rakes and shovels, to run their own experiments at home.

Volkov has jumped in. When the pandemic shut down his lab last year, he took his work — and his plasma balls — home. He bathed the vegetable seeds for his garden for a minute in the lamp’s rich, purplish glow, and then planted them.

“It was cucumber, tomatoes, eggplants, cabbage,” he says. A backyard test run isn’t proof of anything, Volkov readily acknowledges, and any gardener can attest that a finicky combination of variables can make or break a garden.

But he did see an astounding harvest last fall. By late October, he was still picking big, ripe tomatoes from the vines grown from plasma-treated seeds, at a time when the plants from untreated seeds have often withered. The cucumbers were bigger and juicier. The cabbages, planted in a friend’s nursery, were heavier and more delicious, he says. “I got a fantastic amount of everything.”

Dog DNA reveals ancient trade network connecting the Arctic to the outside world

Ancient Arctic communities traded with the outside world as early as 7,000 years ago, DNA from the remains of Siberian dogs suggests.

Analysis of the DNA shows that Arctic pups thousands of years ago were interbreeding with other dogs from Europe and the Near East, even while they and their owners were living in one of the most remote places on Earth. Along with previous archaeological finds, these results suggest that Siberians long ago were connected to a vast trade network that may have extended as far as the Mediterranean and the Caspian Sea, researchers report in the Sept. 28 Proceedings of the National Academy of Sciences.

Dogs have been valuable commodities in the Arctic for the last 9,500 years and have been used for sledding, hunting, herding reindeer, clothing and food. Because the region is remote, scientists thought local dogs — and their owners — had been completely isolated from the rest of the world for much of that time, an idea supported by the fact that ancient Siberians didn’t exchange much DNA with people outside of the region, says Tatiana Feuerborn, an archaeologist at the University of Copenhagen.

But previous archaeological evidence — including the discovery of glass beads and other foreign goods entombed alongside 2,000-year-old dogs near the Yamal Peninsula in Russia — suggested that these communities were trading with other cultures beyond the Arctic.
After reading about the archaeological evidence in the news, Feuerborn wanted to see if she could use remains from the 2,000-year-old dogs and others from around Siberia to reveal whether an ancient trade network existed.

Dogs rarely wander far from their humans, meaning researchers can “use dogs to understand human movement, like migrations and even trade interactions,” says Kelsey Witt, a geneticist at Brown University in Providence, R.I., who was not involved in the study. For instance, archaeologists have used ancient dog DNA to push back the arrival date of people in the Americas (SN: 3/1/21).
In the new study, Feuerborn and colleagues analyzed DNA from the remains of 49 Siberian dogs, ranging from 11,000-year-old bone fragments to fur hoods used by Arctic explorers at the turn of the 20th century. The team found that Siberian dogs — unlike their owners — began mixing with other dog populations from the Eurasian steppes, the Near East and even Europe as far back as 7,000 years ago.

The result suggests that Siberians did bring in dogs from the outside world, Feuerborn says. This trade network could have helped transmit new ideas and technologies, such as metalworking, to the Arctic, and may have facilitated Siberian society’s transition from foraging to reindeer herding in the last 2,000 years.

“Dogs are a piece of our past,” Feuerborn says. “By looking at them, we can learn something about ourselves.”

Astrophysicist writes about the stars for Spanish speakers

Paula Jofré
Astrophysicist
Universidad Diego Portales

Paula Jofré, featured in 2018, used the chemical composition of stars across the Milky Way like DNA to map the stars’ family tree. She recently filled in some details of the tree — and is filling a gap in the publishing world by writing a book about stars in Spanish.

What progress have you made on your stellar family tree?
In the first paper, the tree had three main branches. There was one that we could associate with a young thin disk, which is one of the populations in the Milky Way. Another was associated with an old, thick disk, which was the older component of the Milky Way. And then we had something in between…. Now, because we had more stars and more chemical elements and we made a better selection of which chemical elements to include, we could find that this strange population was actually an ancestor population of the thin disk. And one of the interpretations we had in the second paper [published in January in the Monthly Notices of the Royal Astronomical Society] was that they were produced all very quickly.

Other groups have found striking evidence of a galaxy that was merged into the Milky Way [billions of years ago]. And that [merging and mixing of gas] could have triggered what is called a star formation burst — lots of stars [forming] at the same time. So, it’s kind of exciting that we find in the tree a feature that could be attributed to a star formation burst … a few gigayears after the [merger of these two galaxies] that we know happened.

You’re also writing a popular book on stars. Can you tell me more about the book, Fósiles del cosmos: descifrando la historia de la Vía Láctea, or Fossils of the Cosmos: Deciphering the History of the Milky Way, and why you decided to write it?
It’s going to be published in November [in Chile]. It’s a book in Spanish for the public. I am teaching a class about stars in the Milky Way, a general astronomy class. And I’ve been finding that there is no proper literature in Spanish for the students.… The level is sometimes way too basic or too complex. So I wanted to write something for their level.

[The book] explains how stars create the chemical elements, what’s the role of Gaia [a satellite mission to map the galaxy], what’s the role of the Milky Way Mapper [another survey using Earth-based telescopes], about all these big surveys, why we care, what’s going on.

When I started writing it, of course, I started reading other books…. In all these general astronomy books, women are never highlighted. In my book, I have lots of quotes from 40 different women all around the world, working in my field.… I want to make the point that you can be a woman, you can be clever, you can dedicate yourself to something that is mentally challenging. You can be like any of these 40 women.

What’s the greatest challenge that you’ve faced since 2018?
The biggest challenge has been to promote hiring more women at the faculty level. Chile’s a very small country and they love new figures, young figures being highlighted by the United States. The moment I was in Science News,I became very popular [in Chile] very quickly. They needed the inspirational woman. And I kept saying, “I don’t want to be the only one. I want more women.”

I don’t know if you were aware of this collective Las Tesis; they made a dance for the social unrest that we had in Chile before the pandemic. It was a feminist movement that resonated for so many people in the world. The movement [says]: We want to be treated with respect, we want the same salary, we want the same opportunities, we want to feel safe on the streets.… But then, when you are fewer in academia, you’re not going to start jumping on the table and dancing, right? You have to argue … it’s difficult.

— Interview by Ashley Braun

50 years ago, corporate greenwashing was well under way

Environmental advertising: A question of integrity— Science News, November 27, 1971

A new report published by the Council on Economic Priorities clearly outlines facts showing that much corporate advertising on environmental themes is irrelevant or even deceptive.… A large percentage of the environmental advertising comes from companies that are the worst polluters.

Update
Concerns about “greenwashing,” a term coined in the 1980s to describe the practice of organizations marketing their products as environmentally friendly when they are not, have persisted into the current climate crisis. As more consumers have become environmentally conscious, corporations’ greenwashing tactics have evolved. For instance, some energy companies in the United States have claimed that natural gas is a “clean” energy source because the power plants emit less carbon dioxide than coal plants. But natural gas plants can emit large amounts of methane, a potent greenhouse gas. In 2022, the U.S. Federal Trade Commission plans to review its “Green Guides,” rules for companies that make environmental claims.