Carl Zimmer

The number of birds in the United States and Canada has fallen by 29% since 1970, scientists reported Thursday. There are 2.9 billion fewer birds taking wing now than there were 50 years ago.

The analysis, published in the journal Science, is the most exhaustive and ambitious attempt yet to learn what is happening to avian populations. The results have shocked researchers and conservation organizations.

In a statement Thursday, David Yarnold, president and chief executive of the National Audubon Society, called the findings “a full-blown crisis.”

Experts have long known that some bird species have become vulnerable to extinction. But the new study, based on a broad survey of more than 500 species, reveals steep losses even among such traditionally abundant birds as robins and sparrows.

There are likely many causes, the most important of which include habitat loss and wider use of pesticides. “Silent Spring,” Rachel Carson’s prophetic 1962 book about the harms caused by pesticides, takes its title from the unnatural quiet settling on a world that has lost its birds: “On the mornings that had once throbbed with the dawn chorus of robins, catbirds, doves, jays, wrens, and scores of other bird voices, there was now no sound.”

Kevin Gaston, a conservation biologist at the University of Exeter, said that new findings signal something larger at work: “This is the loss of nature.”

Common bird species are vital to ecosystems, controlling pests, pollinating flowers, spreading seeds and regenerating forests. When these birds disappear, their former habitats often are not the same.

“Declines in your common sparrow or other little brown bird may not receive the same attention as historic losses of bald eagles or sandhill cranes, but they are going to have much more of an impact,” said Hillary Young, a conservation biologist at the University of California, Santa Barbara, who was not involved in the new research.

A team of researchers from universities, government agencies and nonprofit organizations collaborated on the new study, which combined old and new methods for counting birds.

For decades, professional ornithologists have been assisted by an army of devoted amateur bird-watchers who submit their observations to databases and help carry out surveys of bird populations each year.

In the new study, the researchers turned to those surveys to estimate the populations of 529 species between 2006 and 2015.

Those estimates include 76% of all bird species in the United States and Canada, but represent almost the entire population of birds. (The species for which there weren’t enough data to make firm estimates occur only in small numbers.)

The researchers then used bird-watching records to estimate the population of each species since 1970, the earliest year for which there is solid data.

“This approach of combining population abundance estimates across all species and looking for an overall trend is really unprecedented,” said Scott Loss, a conservation biologist at Oklahoma State University who was part of the new study.

While some species grew, the researchers found, the majority declined — often by huge numbers.

“We were stunned by the result — it’s just staggering,” said Kenneth V. Rosenberg, a conservation scientist at Cornell University and the American Bird Conservancy, and lead author of the new study.

“It’s not just these highly threatened birds that we’re afraid are going to go on the endangered species list,” he said. “It’s across the board.”

Weather radar offered another way to track bird populations. Rosenberg and his colleagues counted birds recorded on radar at 143 stations across the United States from 2007 to 2018. They focused on springtime scans, when birds were migrating in great numbers.

The team measured a 14% decline during that period, consistent with the drop recorded in the bird-watching records.

“If we have two data sets showing the same thing, it’s a home run,” said Nicole Michel, a senior quantitative ecologist at the Audubon Society who was not involved in the study.

Among the worst-hit groups were warblers, with a population that dropped by 617 million. There are 440 million fewer blackbirds than there once were.

Rosenberg said he was surprised by how widespread the population drop was. Even starlings — a species that became a fast-breeding pest after its introduction to the United States in 1890 — have dwindled by 83 million birds, a 49% decline.

Europe is experiencing a similar loss of birds, also among common species, said Gaston, of the University of Exeter. “The numbers are broadly comparable,” he said.

The new study was not designed to determine why birds are disappearing, but the results — as well as earlier research — point to some likely culprits, Rosenberg said.

Grassland species have suffered the biggest declines by far, having lost 717 million birds. These birds have probably been decimated by modern agriculture and development.

“Every field that’s plowed under, and every wetland area that’s drained, you lose the birds in that area,” Rosenberg said.

In addition to habitat loss, pesticides may have taken a toll. A study published last week, for example, found that pesticides called neonicotinoids make it harder for birds to put on weight needed for migration, delaying their travel.

The researchers found some positive signs. Bald eagles are thriving, for example, and falcon populations have grown by 33%. Waterfowl are on the upswing.

For the most part, there’s little mystery about how these happy exceptions came to be. Many recovering bird species were nearly wiped out in the last century by pesticides, hunting and other pressures. Conservation measures allowed them to bounce back.

“In those cases, we knew what the causes were and we acted on that,” Rosenberg said. “They’re models of success.”

But some thriving populations are harder to explain.

Tiny warbler-like birds called vireos are booming, with 89 million more birds than in 1970 — a jump of 53%. Yet warblers, which share the same habitats as vireos, have suffered a 37% decline.

“I have no idea why vireos are doing well,” Rosenberg said. “I’d love to do a study of vireos and discover what their secret is.”

The sheer scale of the bird decline meant that stopping it would require immense effort, said Young, of the University of California, Santa Barbara. Habitats must be defended, chemicals restricted, buildings redesigned. “We’re overusing the world, so it’s affecting everything,” she said.

The Audubon Society is calling for protection of bird-rich habitats, such as the Great Lakes and the Colorado River Basin, as well as for upholding the Migratory Bird Treaty Act, which the Trump administration is trying to roll back.

The society and other bird advocacy groups also suggest things that individuals can do. They urge keeping cats inside, so they don’t kill smaller birds. Vast numbers of birds die each year after flying into windows; there are ways to make the glass more visible to them.

To some birders, the study’s findings confirmed a dreaded hunch.

Beverly Gyllenhaal, 62, a retired cookbook author, and her husband, Anders, have spotted 256 species in parks in the eastern United States. But when she visited her mother in North Carolina in recent years, it seemed there weren’t as many birds as she recalled from her childhood there.

And when she talks to people around the United States on her birding travels, many say the same thing. “Oftentimes people will tell you, ‘It’s nothing like it used to be,’” she said.

The estimated losses have left her appalled. “If the cardinals and the blue jays and the sparrows aren’t doing well,” she said, “that’s really scary.”

This article originally appeared in

(Matter)

Birds Are Vanishing From North America

In a laboratory at the Stanford University School of Medicine, the mice are seeing things. And it’s not because they’ve been given drugs.

With new laser technology, scientists have triggered specific hallucinations in mice by switching on a few neurons with beams of light. The researchers reported the results Thursday in the journal Science.

The technique promises to provide clues to how the billions of neurons in the brain make sense of the environment. Eventually the research also may lead to new treatments for psychological disorders, including uncontrollable hallucinations.

“This is spectacular — this is the dream,” said Lindsey Glickfeld, a neuroscientist at Duke University, who was not involved in the new study.

In the early 2000s, Karl Deisseroth, a psychiatrist and neuroscientist at Stanford, and other scientists engineered neurons in the brains of living mice to switch on when exposed to a flash of light. The technique is known as optogenetics.

In the first wave of these experiments, researchers used light to learn how various types of neurons worked. But Deisseroth wanted to be able to pick out any individual cell in the brain and turn it on and off with light.

So he and his colleagues designed a new device: Instead of just bathing a mouse’s brain in light, it allowed the researchers to deliver tiny beams of red light that could strike dozens of individual brain neurons at once.

To try out this new system, Deisseroth and his colleagues focused on the brain’s perception of the visual world. When light enters the eyes — of a mouse or a human — it triggers nerve endings in the retina that send electrical impulses to the rear of the brain.

There, in a region called the visual cortex, neurons quickly detect edges and other patterns, which the brain then assembles into a picture of reality.

The scientists inserted two genes into neurons in the visual cortices of mice. One gene made the neurons sensitive to the red laser light. The other caused neurons to produce a green flash when turned on, letting the researchers track their activity in response to stimuli.

The engineered mice were shown pictures on a monitor. Some were of vertical stripes, others of horizontal stripes. Sometimes the stripes were bright, sometimes fuzzy. The researchers trained the mice to lick a pipe only if they saw vertical stripes. If they performed the test correctly, they were rewarded with a drop of water.

As the mice were shown images, thousands of neurons in their visual cortices flashed green. One population of cells switched on in response to vertical stripes; other neurons flipped on when the mice were shown horizontal ones.

The researchers picked a few dozen neurons from each group to target. They again showed the stripes to the mice, and this time they also fired light at the neurons from the corresponding group. Switching on the correct neurons helped the mice do better at recognizing stripes.

Then the researchers turned off the monitor, leaving the mice in darkness. Now the scientists switched on the neurons for horizontal and vertical stripes, without anything for the rodents to see. The mice responded by licking the pipe, as if they were actually seeing vertical stripes.

Anne Churchland, a neuroscientist at Cold Spring Harbor Laboratory who was not involved in the study, cautioned that this kind of experiment can’t reveal much about a mouse’s inner experience.

“It’s not like a creature can tell you, ‘Oh, wow, I saw a horizontal bar,’ ” she said.

Churchland said that it would take more research to better understand why the mice behaved as they did in response to the flashes of red light. Did they see the horizontal stripes more clearly, or were they less distracted by misleading signals?

One of the most remarkable results from the study came about when Deisseroth and his colleagues narrowed their beams of red light to fewer and fewer neurons. They kept getting the mice to lick the pipe as if they were seeing the vertical stripes.

In the end, the scientists found they could trigger the hallucinations by stimulating as few as two neurons. Thousands of other neurons in the visual cortex would follow the lead of those two cells, flashing green as they became active.

Clusters of neurons in the brain may be tuned so that they’re ready to fire at even a slight stimulus, Deisseroth and his colleagues concluded — like a snowbank poised to become an avalanche.

But it doesn’t take a fancy optogenetic device to make a few neurons fire. Even when they’re not receiving a stimulus, neurons sometimes just fire at random.

That raises a puzzle: If all it takes is two neurons, why are we not hallucinating all the time?

Maybe our brain wiring prevents it, Deisseroth said. When a neuron randomly fires, others may send a signal to quiet down.

Glickfeld speculated that attention may be crucial to triggering the avalanche of neuronal action only at the right times. “Attention allows you to ignore a lot of the background activity,” she said.

Deisseroth hopes to see what other hallucinations he can trigger with light. In other parts of the brain, he might be able to cause mice to perceive more complex images, such as the face of a cat. He might be able to coax neurons to create phantom sounds, or even phantom smells.

As a psychiatrist, Deisseroth has treated patients who have suffered from visual hallucinations. In his role as a neuroscientist, he’d like to find out more about how individual neurons give rise to these images — and how to stop them.

“Now we know where those cells are, what they look like, what their shape is,” he said. “In future work, we can get to know them in much more detail.”

This article originally appeared in <a href="https://www.nytimes.com/2019/07/18/science/mice-brain-hallucinations.html" id="c613659a-2622-3a9f-a1e9-7cd9c83023ea">The New York Times</a>.

Why Are These Mice Hallucinating? Scientists Are in Their Heads

For 340 days, Scott Kelly circled the Earth aboard the International Space Station, gathering data about himself.

He drew blood from his arms. He saved his urine. He played computer games to test his memory and reaction speed. He measured the shape of his eyes.

Two hundred-and-forty miles below, Scott’s twin brother, Mark, who also served as an astronaut, carried out identical tests. Now, a comparison of these two men has provided a unique opportunity to learn what happens to the human body in space — down to the molecular level.

On Thursday, just over three years after Scott Kelly, 55, returned to Earth, NASA researchers reported that his body experienced a vast number of changes while in orbit. DNA mutated in some of his cells. His immune system produced a host of new signals. His microbiome gained new species of bacteria.

Many of these biological changes seemed harmless, disappearing after he returned to Earth. But others — including genetic mutations and, after his return, declines in cognitive test scores — did not correct themselves, provoking concern among scientists.

Some considered the risks manageable, while others wondered whether it would ever be safe for astronauts to take long journeys to Mars or beyond. Final answers will depend on studies of still more astronauts.

“I believe it’s the most comprehensive assessment of human beings to date,” said Dr. Eric Topol, director of the Scripps Research Translational Institute, who was not involved in the study. “I don’t know that there’s been anything close to this.”

Although astronauts have been carried aloft for almost six decades, there’s much about life in space that scientists still don’t understand. With investigations like the NASA Twins Study, published in the journal Science, the agency hopes to get some answers before sending astronauts on longer flights.

In 2012, NASA picked Kelly to join Russian cosmonaut Mikhail Kornienko aboard the space station for a yearlong examination of the challenges of space travel, twice as long as previous studies.

In the run-up to the mission’s announcement, Kelly asked officials if they had any plans to compare him to his twin. “We have these two guys who are genetically identical,” Kelly recalled telling them. “They’d make for an interesting experiment.”

Officials had no such plans, but soon decided to take him up on the offer. Mark Kelly agreed, and the NASA Twins Study was born. (Mark Kelly, who retired from NASA in 2011 and is the husband of former Rep. Gabrielle Giffords, is running for John McCain’s Senate seat in Arizona.)

By comparing the brothers, NASA hoped to better understand the changes that Scott Kelly experienced during his mission.

“The fact that they’re twins really narrows down the alternatives,” said Susan Bailey, a cancer biologist at Colorado State University and a co-author of the new study. “We can say that, as best as we can tell, these changes are due to spaceflight.”

Ten research teams designed experiments for the twins; they are likely to bring an avalanche of research. But to Kelly, the experience didn’t feel very different from previous missions.

Drawing his own blood in zero gravity, for example, was a familiar routine. “I’ve had a couple spills in my time,” Kelly said. “You just reach out and grab the blobs of blood.”

By many measures, the scientists eventually found, Kelly changed about as much as astronauts who stayed on the space station for only six months. Eventually the pace of biological change slowed, suggesting that perhaps the human body reaches a new equilibrium in space.

But Kelly’s body was also altered in some surprising ways.

Bailey studied special sections of his DNA called telomeres, which sit at the end of chromosomes, protecting them from deterioration.

As people age, their telomeres tend to get shorter. Stress — such as radiation or pollution — may hasten aging by fraying telomeres even faster than usual.

Strangely, the average length of Kelly’s telomeres increased in space, rather than decreasing, as if his cells were becoming more youthful.

Regular exercise and a healthy diet might be part of the reason. But going to space also might have awakened a quiet population of stem cells in Kelly’s body, Bailey said.

His cells might not have grown longer telomeres, in other words. Instead, perhaps his body manufactured a new supply of young cells with longer telomeres.

Activated Genes

Going to space also appeared to trigger a genetic shift in Kelly. Thousands of genes that were once quiet increased their activity — genes that remained quiet in Mark Kelly’s body back on Earth. The longer Scott Kelly stayed aloft, the greater the number of genes becoming active.

Some of the awakened genes are known to encode proteins that help fix damaged DNA. That would make sense, given that radiation levels in the International Space Station are higher than on Earth.

Christopher Mason, a geneticist at Weill Cornell Medicine in New York, estimated that Kelly was exposed to 48 times more radiation than the average exposure on Earth over the course of a year. His cells might have been busy repairing radiation injury.

A number of other activated genes, however, play roles in the immune system. What exactly triggers those changes isn’t clear.

It may be the overall stress of life in the space station provokes an immune response. But recent studies have also shown that latent viruses can awaken in astronauts.

Or maybe it’s that the immune system, which never evolved for survival in space, simply gets confused.

“Is it good or bad? We just know it’s more,” Mason, a co-author of the new study, said of the immune activity. “To know for sure, we’d need more astronauts.”

Kelly’s return to Earth on March 1, 2016, proved to be one of the biggest moments — biologically speaking — of the whole mission. His body showed signs of intense stress, and his immune system was in high gear.

Michael Snyder, a geneticist at Stanford University and co-author of the research, cautioned that this response might not be typical. “Maybe he got a viral infection,” he speculated. “This is why you want to see it in more people.”

Despite that shock, Kelly’s body mostly returned to preflight condition. Some species of bacteria that thrived in his gut while he was in space, for example, became rare again on his landing.

The strange lengthening of Kelly’s telomeres disappeared after less than 48 hours on Earth. In fact, Bailey and her colleagues started finding many cells with telomeres that were shorter than before Kelly went to space.

“People have asked me, ‘Well, is going to space the fountain of youth?’ ” Bailey said. “I don’t think so. If it is, you’re going to have to stay up there forever.”

‘Fighting Through Quicksand’

Some aspects of Kelly’s biology didn’t return to the preflight norm.

Six months after he came back to Earth, 8.7% of his genes were still behaving in an altered way. Judging from the small size of this shift, Snyder described the change as modest.

The researchers also found that Kelly didn’t do as well on his return on cognitive exams. “He got slower and less accurate on virtually all of the tests,” said Dr. Mathias Basner, a cognitive scientist at the University of Pennsylvania.

It’s possible that some biological change was to blame. But Basner noted that Kelly also faced a lot of demands back on Earth, including a busy schedule of television interviews and public speaking.

And on an unconscious level, he may no longer have been pushing himself. “I mean, he basically retired the moment he hit the ground, and so perhaps he just wasn’t as motivated any longer,” Basner said.

In his 2017 memoir, “Endurance,” Kelly describes struggling after his return with pain, sleeping troubles and other woes. One night he felt as if he was “fighting through quicksand,” he wrote.

In an interview, Kelly speculated those difficulties might be to blame for his cognitive scores. “It’s hard to concentrate when you’re not feeling well,” he said.

Another enduring change, scientists found, was a collection of genetic mutations that Kelly gained in space. “We see them appear in flight, and then they persisted afterward,” Mason said.

Sometimes radiation triggers a type of mutation that makes cells prone to gain still more mutations as they divide. Eventually, the cells may start growing uncontrollably — “taking steps on the road to cancer,” Bailey said.

Peter Campbell, a cancer biologist at the Wellcome Sanger Institute in Britain who was not involved in the new study, said scientists can’t predict what the extra mutations will mean for Kelly’s health.

“It is hard to be sure, but I believe those sorts of numbers would be associated with a moderate increase in cancer risk,” he said.

These two lingering changes — in Kelly’s cognition and DNA — left a number of experts concerned about the risks of a trip to Mars, which could take a year.

Gary Strangman, a psychologist at Harvard Medical School, said that a decrease in speed and accuracy “could potentially have serious consequences on long-duration missions.”

After a grueling journey to the red planet, astronauts would probably need to take quick, accurate actions as they landed.

“If you had a period of slower cognitive processing speed and difficulty with balance and eye-head coordination, those behaviors would be at risk,” said Rachael Seidler, a cognitive neuroscientist at the University of Florida.

A heavy load of genetic mutations would not present immediate dangers to astronauts on their missions, but it might raise their lifelong risks of cancer.

Mason estimated that a mission to Mars would expose an astronaut to eight times more radiation than Kelly experienced.

“Every effort will need to be made to limit exposure to astronauts during periods of prolonged space travel,” said Charles Swanton, a cancer biologist at the Francis Crick Institute in Britain who was not involved in the new study.

Topol, of the Scripps institute, found the implications of Kelly’s experience to be grim.

“The main conclusion I got from this paper, based on all the objective data, is why would anybody want to go to Mars or be in space?” he said. “Because this is really scary.”

Jerry Shay, a cell biologist at the University of Texas Southwestern Medical Center, was much more optimistic. He held out hope for countermeasures that would protect astronauts.

Already he and his colleagues, for example, are testing drugs to trigger cells to fix DNA damaged by radiation. “I think all these problems are solvable,” Shay said.

NASA has begun sifting through all these results to help plan the next round of missions to the International Space Station.

“It won’t be a replication of what you saw in the Twins Study,” said Jennifer Fogarty, chief scientist at NASA’s Human Research Program.

“We’re going to learn from that, and we’re going to be smarter about the questions we ask. There’s a lot of fascinating stuff to go measure. It’s just not clear what it means.”

Bailey, for her part, plans to keep on studying Kelly’s baffling telomeres. Solving that mystery might shed light on ordinary aging and the diseases it brings.

“When we figure out the how and why of that, it’s going to be important for astronauts as well as for us mere Earthlings,” she said.

This article originally appeared in <a href="https://www.nytimes.com/2019/04/11/science/scott-mark-kelly-twins-space-nasa.html" id="682952c4-878c-39e3-a73c-2160512c0ed5">The New York Times</a>.

Sibling Rivalry of Sorts in a Study of Life in Orbit

Two hundred-and-forty miles below, Scott’s twin brother, Mark, who also served as an astronaut, carried out identical tests. Now, a comparison of these two men has provided an opportunity to learn what happens to the human body in space.

Many of these biological changes seemed harmless, disappearing after he returned to Earth. But others did not correct themselves, provoking concern among scientists.

“The fact that they’re twins really narrows down the alternatives,” said Susan Bailey, a co-author of the new study. “We can say that, as best as we can tell, these changes are due to spaceflight.”

Bailey studied special sections of Kelly’s DNA called telomeres, which sit at the end of chromosomes, protecting them from deterioration.

As people age, their telomeres tend to get shorter.

Going to space also appeared to trigger a genetic shift in Kelly. Thousands of genes that were once quiet increased their activity.

Six months after he came back to Earth, 8.7 percent of his genes were still behaving in an altered way.

The researchers also found that Kelly didn’t do as well on his return on cognitive exams.

Another enduring change, scientists found, was a collection of genetic mutations that Kelly gained in space.

Scott Kelly Spent a Year in Orbit. His Body Is Not Quite the Same.

Many of these biological changes seemed harmless, disappearing after he returned to Earth. But others — including genetic mutations and, after his return, declines in cognition test scores — did not correct themselves, provoking concern among scientists.

Although astronauts have been carried aloft for almost six decades, there’s much about life in space that scientists still don’t understand. With investigations like the NASA Twins Study, published in the journal Science, the agency hopes to answer some of the questions before sending astronauts on longer flights.

Starting in March 2015, astronaut Scott Kelly spent 340 days aboard the International Space Station. A team of scientists tracked his body’s responses to long-term spaceflight in painstaking detail. They simultaneously tracked his identical twin brother, Mark, on Earth.

On Thursday, the scientists began publishing the huge trove of results from the so-called NASA Twins Study — 90 pages, all told, and that’s just the first installment. Here’s a guide to what they’ve found … so far.

— Space travel changes the body.

Scientists tracked a huge range of measurements in the NASA Twins Study, from Scott Kelly’s performance on cognition tests to levels of gene activity in his cells. Many of the molecular tests had never been carried out on astronauts before.

The exams required Kelly to draw his own blood and to send fresh samples back to Earth in a Soyuz supply craft. Within 48 hours, researchers were analyzing the samples at NASA labs.

In one test, researchers broke open Kelly’s white blood cells and searched for molecular signals from each of his genes to see whether they were active. The scientists identified thousands of genes that ramped up their pace.

By looking at what those genes do, the team gleaned some clues as to why they became active in Kelly. Some are known to be triggered by stress, so it was no surprise to find that Kelly’s immune system also was on high alert.

In another test, the researchers scrutinized molecular caps on the ends of Kelly’s chromosomes, called telomeres. Telomeres shorten with age, and stress can shorten them further. But Kelly’s telomeres actually grew longer on average during his time in space.

— But it’s not clear what the changes mean.

Human biology is complicated and mysterious, even here on Earth. So documenting changes that Kelly experienced in space won’t automatically help scientists understand the causes.

For example, why did his telomeres get longer? The Twins Study researchers are still trying to figure it out. It might have something to do with Kelly’s carefully designed, nutrient-rich diet — or perhaps the stress of space travel triggered stem cells to wake up and start multiplying.

Another mystery lies in the very design of the experiment. NASA only examined a single astronaut in space, comparing his responses to his genetically identical brother. It’s hard to know if all astronauts would experience the same changes — or if some of those changes are flukes of his own experience and genetic makeup.

— The most worrisome findings: genetic mutations and lower scores on cognition tests.

Radiation can trigger certain mutations that may increase a person’s risk of developing cancer. And there’s more radiation in Earth orbit than on the surface of the planet.

In his 340 days aboard the space station, Kelly was exposed to an estimated 48 times more radiation than he would have been subjected to had he spent a year on the planet.

Scientists were able to observe the appearance of radiation-induced mutations in Kelly’s cells. The mutations were still present in Kelly months after his return, suggesting that he’ll carry them forward in his life, possibly causing a modest increase in his risk of cancer.

So it’s a bit worrying that a long-term trip to Mars would expose astronauts to eight times more radiation than Kelly received.

In addition, Kelly did worse on cognition tests even six months after landing, making more mistakes and responding more slowly. It’s possible that the physical demands of spaceflight were too blame, or that unconsciously his motivation had decreased.

These unexpected declines led some researchers to worry about how ready astronauts would be for a challenging landing on Mars after many months in deep space.

— If we attempt a trip to Mars, we’ll need to prepare.

NASA understands that long-duration spaceflight could pose serious challenges to astronauts. By studying those challenges aboard the space station, the agency has been trying to quantify those risks. And on Earth, scientists have been investigating potential countermeasures.

Take radiation. On the space station, Kelly’s cells switched on genes known to help repair DNA. It’s possible that his cells actually undid a lot of mutations right after they arose. Researchers are investigating a variety of compounds that might spur the cells of astronauts to repair even more damage.

But such drugs might not be enough to handle, say, an unexpected solar flare, which would spray vast amounts of radiation. Some experts have speculated that spaceships would need a shielded room where astronauts could hide until flares were over.

Although that might protect astronauts in theory, it would also add a lot of extra weight to a mission to Mars. And that’s just one of the biological risks that scientists will have to plan for.

This article originally appeared in <a href="https://www.nytimes.com/2019/04/11/science/scott-kelly-twins-study-nasa.html" id="a43addc0-4bdf-3481-a4f4-f623c7fcd961">The New York Times</a>.

There’s never been a study like it before, and there probably never will be again.

4 Takeaways From That Huge Study of Scott Kelly

On Thursday, just over three years after Scott Kelly, 55, returned to Earth, researchers with the NASA Twins Study published the first detailed findings in the journal Science.

The researchers found that Kelly’s body experienced a vast number of changes while in orbit. DNA mutated in some of his cells. His immune system produced a host of new signals. His microbiome gained new species of bacteria.

Although astronauts have been carried aloft for almost six decades, there’s much about life in space that scientists still don’t understand. NASA would like to resolve some of that mystery before sending astronauts on longer flights.

In an interview last week, Kelly speculated those difficulties might be to blame for his cognitive scores. “It’s hard to concentrate when you’re not feeling well,” he said.

The researchers found Kelly’s body experienced a vast number of changes while in orbit. DNA mutated in some of his cells. His immune system produced a host of new signals. His microbiome gained new species of bacteria.

<h1>(Science Times): At 3 o’clock in the afternoon on Sept. 4, 1882, the electrical age began. The Edison Illuminating Co. switched on its Pearl Street power plant, and a network of copper wires came alive, delivering current to a few dozen buildings in the surrounding neighborhood.</h1>

One of those buildings housed The New York Times. As night fell, reporters at The Times gloried in the steady illumination thrown off by Thomas Edison’s electric lamps. “The light was soft, mellow, and grateful to the eye, and it seemed almost like writing by daylight,” they reported in an article the next day.

But nature invented the electrical grid first, it turns out. Even in 1882, thousands of miles of wires were already installed in the ground in the New York region — in meadows, in salt marshes, in muddy river bottoms. They were built by microbes, which used them to shuttle electricity.

Electroactive bacteria were unknown to science until a couple of decades ago. But now that scientists know what to look for, they’re finding this natural electricity across much of the world, even on the ocean floor. It alters entire ecosystems, and may help control the chemistry of the Earth.

“Not to sound too crazy, but we have an electric planet,” said John Stolz, a microbiologist at Duquesne University in Pittsburgh.

In the mid-1980s, Stolz was helping to study a baffling microbe fished out of the Potomac River by his colleague Derek Lovley. The microbe, Geobacter metallireducens, had a bizarre metabolism. “It took me six months to figure out how to grow it in the lab,” said Lovley, now a microbiologist at the University of Massachusetts at Amherst.

Like us, Geobacter feed on carbon compounds. As our cells break down these compounds to generate energy, they strip off free electrons and transfer them to oxygen atoms, producing water molecules. Geobacter couldn’t use oxygen, however, because it lived at the bottom of the Potomac, where the element was in short supply.

Instead, Geobacter transfers its electrons to iron oxide, or rust, Lovley and his colleagues discovered. The process helps turn rust into another iron compound, called magnetite.

The finding left the scientists with a puzzle. We humans draw oxygen into our cells to use it, but Geobacter does not import rust. So the microbe must somehow get the electrons out of its cell body and attach them to rust particles. How?

The researchers struggled for years to find the answer. Stolz eventually turned to other microbes to study. But Lovley soldiered on. Over the years, he and his colleagues have come across Geobacter in many places far beyond the Potomac. They’ve even encountered the bacteria in oil drilled from deep underground. “It’s basically found everywhere,” Lovley said.

In the early 2000s, Lovley’s team discovered that Geobacter could sense rust in its neighborhood. The microbe responded by sprouting hairlike growths.

Maybe each of those growths, known as a pilus, was actually a wire that latched onto the rust, Lovley thought. Electrons could flow from the bacterium down the wire to the receptive rust. “It seemed like a wild idea at the time,” Lovley said.

But he and his team found several clues suggesting that the pilus is indeed a living wire. In one experiment, when Geobacter was prevented from making pili, the bacteria couldn’t turn rust to magnetite. In another, Lovley and his colleagues plucked pili from the bacteria and touched them with an electrified probe. The current swiftly shot down the length of the hairs.

Subsequent research revealed that Geobacter can deploy its wires in different ways to make a living. Not only can it plug directly into rust, it can also plug into other species of microbes.

The partners of Geobacter welcome the incoming flow of electrons. They use the current to power their own chemical reactions, which convert carbon dioxide into methane.

Discoveries like these raised the possibility that other bacteria might be dabbling in electricity. And in recent years, microbiologists have discovered a number of species that do.

“When people are able to dig down at the molecular level, we’re finding major differences in strategy,” said Jeff Gralnick of the University of Minnesota. “Microbes have solved this issue in several different ways.”

In the early 2000s, a Danish microbiologist named Lars Peter Nielsen discovered a very different way to build a microbial wire. He dug up some mud from the Bay of Aarhus and brought it to his lab. Putting probes in the mud, he observed the chemical reactions carried out by its microbes.

“It developed in a very weird direction,” Nielsen recalled.

One of those buildings housed The New York Times. As night fell, reporters at The Times gloried in the steady illumination thrown off by Thomas Edison’s electric lamps. “The light was soft, mellow, and grateful to the eye, and it seemed almost like writing by daylight,” they reported in an article the next day.

Carl Zimmer

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