Happy 40th anniversary, Viking 1! Four decades ago — July 20, 1976 — the robotic probe became the first U.S. mission to land on Mars. Its sister spacecraft, Viking 2, touched down 45 days later.

Launched August 20, 1975, Viking 1 spent over 6 years snapping pictures and studying the soil at its landing site, an ancient crater named Chryse Planitia. An experiment to look for Martian microbes turned up nothing definitive, though some researchers continue to argue otherwise.

Viking 1 wasn’t the first to successfully touch down on the Red Planet. That honor goes to the Soviet probe Mars 3, whichgently landed on Mars in 1971, though its only transmission — a partial, garbled image — lasted just 20 seconds.

Today, seven probes actively call Mars home. A European-led orbiter and lander, ExoMars, is on its way, and NASA has two missions lined up: the Insight lander, whose launch was recently delayed to 2018, and the Mars 2020 rover, which will pick up where the Vikings left off and search for Martian life.

The latest in birthday science proposes that the vertebrate with the longest life span yet measured is the mysterious Greenland shark.

Dating based on forms of carbon found in sharks’ eye lenses suggests that a large female Somniosus microcephalus was about 392 years old (give or take 120 years) when she died, says marine biologist Julius Nielsen of University of Copenhagen. Even with that uncertainty, the shark outdoes what Nielsen considers the previous record holder: a bowhead whale estimated to have lived 211 years.
The dating comes from the first use of eye-lens dating for a fish, Nielsen says. An analysis that produced the date, involving 27 other Greenland shark specimens, suggests that females don’t reach sexual maturity until they’re about 156 years old, Nielsen and his colleagues report August 12 in Science. Remarkably little basic biology is known for the Greenland shark, though.

And figuring out the age of these sharks has “stymied all solution attempts,” says Steven Campana of the University of Iceland in Reykjavik. ”Given that the Greenland shark is one of the largest carnivores in the world and the king of the food chain [in northern waters], it is almost unbelievable that we don’t know if this shark lives to 20 years or to 1,000,” says Campana, who has long studied shark aging but was not part of this research. Both extremes have been suggested.

Unlike familiar bony fish, such as salmon and cod, sharks don’t have ear bones that build up calcified rings that reveal age. Some sharks, such as the great whites, have some calcified vertebrae that serve, but the Greenland species is “a soft shark,” Nielsen says. And it’s an odd-looking one. He finds that some people are disappointed with their first sight of the big, dark, ponderous beasts because they’re a long way from the stereotype of the great white sharks’ streamlined killer look. “Definitely plump,” Nielsen says.

Working with 28 Greenland sharks of different sizes that were accidentally caught during fisheries surveys, Nielsen and his colleagues examined eye lenses. The highly specialized clear proteins in lenses start with a nugget formed in utero, and studies in mammals have scrutinized that small bit for clues to a creature’s birth date.

Nielsen’s team looked for anomalies in carbon created by the pulse of radioactivity from the 1950s bomb testing in the Pacific Ocean. Radiocarbons worked their way into, and lingered in, all the food webs on the planet. The pulse first reached the sharks’ realms in the North Atlantic in the 1960s, the scientific literature indicates. Nielsen was startled to discover that only three specimens in his collection had the carbon anomalies — and they were the smaller sharks.
He and colleagues used the size of a shark that appeared to have been born just as the bomb pulse was arriving in the ocean food system as a kind of calibration marker. Then, in an elaborate statistical analysis, they used size and growth rates to work out ages for the rest.

Campana is skeptical that Greenland sharks can live nearly 400 years. Other sharks typically live for 10 to 80 years, he says. “I certainly accept that it grows for more than a century.” But to crown the Greenland shark a record holder, he is waiting for future research.

Extreme life spans evolve just like polar bear white fur or long giraffe necks to fit into the sum of ways an organism feeds, dodges its predators and reproduces in its environment. Says James R. Carey of the University of California, Davis, who studies demography across the tree of life, “the really deeper question is once you identify a species that’s long-lived — why?”

The Wasp That Brainwashed the Caterpillar Matt Simon Penguin Books, $20
Writer Matt Simon begins his new book with a bleak outlook on life: “In the animal kingdom, life sucks and then you die.” But thanks to evolution — which Simon calls “the most majestic problem-solving force on planet Earth” — some critters have peculiar adaptations that make life suck a little less (though sometimes at the expense of other species).

From mustachioed toads to pink fairy armadillos, Simon’s debut book, The Wasp That Brainwashed the Caterpillar, recounts an eclectic cadre of animals that use creative and often bizarre solutions to find love, a babysitter, a meal or a place to crash.
Take, for instance, the book’s title characters. Technically, it’s the wasp larvae that brainwash the caterpillar. Once a female Glyptapanteles wasp deposits eggs into a living caterpillar, she takes off, leaving the oblivious host to babysit her young. After hatching, some larvae stay behind to release chemicals that manipulate the caterpillar’s brain. Once their siblings erupt from the poor creature’s body, the caterpillar mindlessly protects the youngsters from predators.

Mind control isn’t unique to wasps — flies and even fungi do it, too. But the book is about more than just the seemingly diabolical tactics of parasites. Prey species also have skin, or in some cases snot, in the game.

Hagfish, eel-like fish that scavenge the seafloor, eject thick, slimy mucus to clog the gills of sharks that try to make a meal of the hagfish. And the East African crested rat protects itself from dogs and other predators by slathering its fur with the chewed-up bark of the Acokanthera tree, traditionally used by indigenous hunters to make poison arrows. “A species may gain an edge, but any sort of edge is answered,” Simon writes. And so marches on the arms race of natural selection.

The author never dives deeply into exactly how these creatures evolved. The book is a quick, fun read that’s light on science and heavy on snark (not to mention a lot of anthropomorphizing). Readers familiar with Simon’s column for Wired, “Absurd Creature of the Week,” may already be acquainted with some of these animals. But the book is packed full of even more fascinating facts that will both impress and creep out.

SAN DIEGO — Mice raised in cages bombarded with glowing lights and sounds have profound brain abnormalities and behavioral trouble. Hours of daily stimulation led to behaviors reminiscent of attention-deficit/hyperactivity disorder, scientists reported November 14 at the annual meeting of the Society for Neuroscience.

Certain kinds of sensory stimulation, such as sights and sounds, are known to help the brain develop correctly. But scientists from Seattle Children’s Research Institute wondered whether too much stimulation or stimulation of the wrong sort could have negative effects on the growing brain.
To mimic extreme screen exposure, mice were blasted with flashing lights and TV audio for six hours a day. The cacophony began when the mice were 10 days old and lasted for six weeks. After the end of the ordeal, scientists examined the mice’s brains.

“We found dramatic changes everywhere in the brain,” said study coauthor Jan-Marino Ramirez. Mice that had been stimulated had fewer newborn nerve cells in the hippocampus, a brain structure important for learning and memory, than unstimulated mice, Ramirez said. The stimulation also made certain nerve cells more active in general.

Stimulated mice also displayed behaviors similar to some associated with ADHD in children. These mice were noticeably more active and had trouble remembering whether they had encountered an object. The mice also seemed more inclined to take risks, venturing into open areas that mice normally shy away from, for instance.

Some of these results have been reported previously by the Seattle researchers, who have now replicated the findings in a different group of mice. Ramirez and colleagues are extending the work by looking for more detailed behavioral changes.

For instance, preliminary tests have revealed that the mice are impatient and have trouble waiting for rewards. When given a choice between a long wait for a good reward of four food pellets and a short wait for one pellet, stimulated mice were more likely to go for the instant gratification than non-stimulated mice, particularly as wait times increased.
Overstimulation didn’t have the same effects on adult mice, a result that suggests the stimulation had a big influence on the developing — but not fully formed — brain.

If massive amounts of audio and visual stimulation do harm the growing brain, parents need to ponder how their children should interact with screens. So far, though, the research is too preliminary to change guidelines (SN Online: 10/23/16).

“We are not in a position where we can give parents advice,” said neuroscientist Gina Turrigiano of Brandeis University in Waltham, Mass. The results are from mice, not children. “There are always issues in translating research from mice to people,” Turrigiano said.

What’s more, early sensory input may not affect all children the same way. “Each kid will respond very, very differently,” Turrigiano said. Those different responses might be behind why some children are more vulnerable to ADHD.

There’s still much scientists don’t understand about how sensory input early in life wires the brain. It’s possible that what seems like excessive sensory stimulation early in life might actually be a good thing for some children, sculpting brains in a way that makes them better at interacting with the fast-paced technological world, said Leah Krubitzer of the University of California, Davis. “This overstimulation might be adaptive,” she said. “The benefits may outweigh the deficits.”

Dogs don’t miss much. After watching a human do a trick, dogs remembered the tricks well enough to copy them perfectly a minute later, a new study finds. The results suggest that our furry friends possess some version of episodic memory, which allows them to recall personal experiences, and not just simple associations between, for instance, sitting and getting a treat.

Pet dogs watched a human do something — climb on a chair, look inside a bucket or touch an umbrella. Either a minute or an hour later, the dog was unexpectedly asked to copy the behavior with a “Do it!” command, an imitation that the dogs had already been trained to do. In many cases, dogs were able to obey these surprise commands, particularly after just a minute. Dogs didn’t perform as well when they had to wait an hour for the test, suggesting that the memories grew hazier with time.

Like people, dogs seem to form memories about their experiences all the time, even when they don’t expect to have to use those memories later, study coauthor Claudia Fugazza of Eötvös Loránd University in Budapest and colleagues write November 23 in Current Biology.

An antimatter atom abides by the same rules as its matter look-alike. Scientists studying antihydrogen have found that the energy needed to bump the atoms into an excited, or high-energy, state is the same as for normal hydrogen atoms.

Scientists at the European particle physics lab CERN in Geneva created antihydrogen atoms by combining antiprotons and positrons, the electron’s antiparticle. Hitting the resulting atoms with a laser tuned to a particular frequency of light boosted the antihydrogen atoms to a higher energy. The frequency of laser light needed to induce this transition was the same as that needed for normal hydrogen atoms, indicating that the energy jump was the same, scientists from the ALPHA-2 experiment report December 19 in Nature.

Antihydrogen’s similarity to hydrogen conforms to a principle known as charge-parity-time, or CPT, symmetry — the idea that the laws of physics would be unchanged if the universe were reflected in a mirror, time reversed, and particles swapped with antiparticles. So far scientists have never discovered a situation where this symmetry doesn’t hold up, but antihydrogen provides a precise way to check for subtle breakdowns in the rule.

Differences between matter and antimatter are essential for the existence of the universe as we know it: The Big Bang produced equal amounts matter and antimatter, yet somehow antimatter became very rare. So scientists are still on the lookout for any unexpected behavior from antimatter.

GRAPEVINE, TEXAS — A pair of cosmic radio beacons known as pulsars keep switching off and on, suggesting that there might be vast numbers of undiscovered pulsars hiding in our galaxy.

Pulsars are rapidly spinning neutron stars, the ultradense cores left behind after massive stars explode. Neutron stars are like lighthouses, sweeping a beam of radio waves around the sky. Astronomers see them as steady pulses of radio energy.

But at least two in the Milky Way seem to spend most of their time turned off, Victoria Kaspi, an astrophysicist at McGill University in Montreal, reported January 4 at a meeting of the American Astronomical Society. One, first detected at Arecibo Observatory in Puerto Rico in November 2011, only pulses about 30 percent of the time. Another, also discovered at Arecibo, laid down a steady beat just 0.8 percent of the time when observed in 2013 and 2015. Then starting in August 2015, it abruptly jumped to being on 16 percent of the time for several months.
When sending out pulses, the pulsars seem to behave like any other pulsar, Kaspi said. “You wouldn’t know that they have this dual personality.” Researchers don’t yet know why some pulsars behave this way. But Kaspi said that it’s probably tied to changes in their magnetic fields, which astronomers think help control the radio beacons.

These two intermittent pulsars join three others that had been previously observed. Given that most spend much of their time off, Kaspi said, astronomers might be missing a large population of pulsars in the Milky Way.

Earth’s magnetic field helps eels go with the flow.

The Gulf Stream fast-tracks young European eels from their birthplace in the Sargasso Sea to the European rivers where they grow up. Eels can sense changes in Earth’s magnetic field to find those highways in a featureless expanse of ocean — even if it means swimming away from their ultimate destination at first, researchers report in the April 13 Current Biology.

European eels (Anguilla anguilla) mate and lay eggs in the salty waters of the Sargasso Sea, a seaweed-rich region in the North Atlantic Ocean. But the fish spend most of their adult lives living in freshwater rivers and estuaries in Europe and North Africa.
Exactly how eels make their journey from seawater to freshwater has baffled scientists for more than a century, says Nathan Putman, a biologist with the National Oceanic and Atmospheric Administration in Miami.

The critters are hard to track. “They’re elusive,” says study coauthor Lewis Naisbett-Jones, a biologist now at the University of North Carolina at Chapel Hill. “They migrate at night and at depth. The only reason we know they spawn in the Sargasso Sea is because that’s where the smallest larvae have been collected.”

Some other marine animals, like sea turtles and salmon, tune in to subtle changes in Earth’s magnetic field to help them migrate long distances. To test whether eels might have the same ability, Putman and his colleagues placed young European eels in a 3,000-liter tank of saltwater surrounded by copper wires. Running electric current through the wires simulated the magnetic field experienced at different places on Earth.
With no electric current, the eels didn’t swim in any particular direction. But when the magnetic field matched what eels would experience in the Sargasso Sea, the fish mostly swam to the southwest corner of their tank. That suggests the eels might use the magnetic field as a guide to help them move in a specific direction to leave their spawning grounds.

Swimming southwest from the Sargasso Sea seems counterintuitive for an eel trying to ultimately go northeast, Putman says. But computer simulations revealed that that particular bearing would push eels into the Gulf Stream, whisking them off to Europe. Catching a more circuitous ride on a current is probably more efficient for the eels than swimming directly across the North Atlantic, says Putman.

Magnetic fields could help eels stay the course, too. A magnetic field corresponding to a spot in the North Atlantic further along the eels’ route to Europe sent the eels in the tank heading northeast. That’s the direction they’d need to go to keep following the Gulf Stream to Europe.

The researchers did see a fair amount of variation in how strongly individual eels responded to magnetic fields. But that makes sense, says Julian Dodson, a biologist at Laval University in Quebec City who wasn’t part of the study. The Gulf Stream is such a powerful current that the eels could wriggle in a spread of directions to get swept up in its flow.

Now, the researchers are looking at whether adult eels use a similar magnetic map to get back to the Sargasso Sea. Adults follow a meandering return route that might take more than a year to complete, previous research suggests (SN Online: 10/5/16). But whether there’s some underlying force that guides them remains to be seen.

Acting like miniature trees that soak up sunlight and release oxygen, photosynthetic bacteria injected into the heart may lighten the damage from heart attacks, a new study in rats suggests.

When researchers injected the bacteria into rats’ hearts, the microbes restored oxygen to heart tissue after blood supply was cut off as in a heart attack, researchers at Stanford University report June 14 in Science Advances.

“It’s really out of the box,” says Himadri Pakrasi, a systems biologist at Washington University in St. Louis who was not involved in the research. “It reads like science fiction to me, but it’s fantastic if it works.”
The organism, called Synechococcus elongatus, has been used recently to produce biofuels, but this may be the first time the cyanobacteria have ever been used in a medical setting, he says.

Other researchers also reacted enthusiastically to the study. “It’s outrageous, but outrageous in a good way,” says Susan Golden, who studies cyanobacteria at the University of California, San Diego. Cardiovascular scientist Matthias Nahrendorf of Massachusetts General Hospital in Boston says, “I enjoy the idea. It’s really fresh.”

Bringing oxygen to starved tissues is what Stanford cardiovascular surgeon Joseph Woo had in mind when he and colleagues dreamed up the plan to put light-harvesting bacteria into the heart. In a heart attack, clogged arteries or blood clots cut off blood flow to the organ. Without oxygen supplied by the blood, heart cells die.

Woo wanted a way for the heart to make its own oxygen or access another supply until doctors could open blocked vessels and restore blood flow. Plants make oxygen from carbon dioxide and sunlight, so Woo wondered, “Why not bring the tree to your heart?”

He and colleagues started by grinding up kale and spinach to harvest chloroplasts, the organelles within plant cells that carry out photosynthesis. But the chloroplasts didn’t survive outside the cells. That’s when the researchers learned about S. elongatus, a photosynthetic organism that Golden and other researchers have long used to study circadian rhythms.
After finding that cyanobacteria could provide oxygen to heart cells in a lab dish, the next step was to see how the cyanobacteria would fare in an animal. The researchers stopped blood flow to part of rats’ hearts and after 15 minutes injected either cyanobacteria or a saline solution. Oxygen in tissue with bacteria increased to about three times the levels measured right after the heart attack, similar to what saline-treated rats experienced.
That was in the dark: When researchers exposed the heart to light, rats that got the bacteria had 25 times higher oxygen levels than they did after the heart attack. Four weeks after the treatment, these rats had less heart damage than untreated rodents, indicating long-term benefits. In fact, the hearts of photosynthesis-treated rats were beating strongly: Blood flow out of the heart was 30 percent higher in rats treated with cyanobacteria and light than those treated with the bacteria in the dark. That extra blood flow could make the difference between life and death for some patients, Woo says. The results indicate that the bacteria need light to supply heart cells with enough oxygen to stave off damage. That presents a difficulty if the cyanobacteria are ever to be used in people: Getting light into the heart is a major hurdle.

“It will be next to impossible to open the chest to light,” says Nahrendorf. “A day on the beach won’t do the trick.” Woo says the researchers are working with engineers at Stanford to make devices that can shine light through bones and skin to reach the heart and other deep tissues.

Injecting bacteria into the heart is also a risky proposition. “What you’re doing is infecting a tissue, and that’s rarely a good thing,” says Nahrendorf. But the cyanobacteria were cleared from the rats’ bodies within 24 hours and didn’t provoke the immune system to attack the heart, the researchers found. Some other cyanobacteria produce toxins, says Golden. “But this organism is benign,” she says.

Cyanobacteria might also supply oxygen to tissues in other diseases, such as brain injuries, strokes or nonhealing wounds in people with diabetes, says Arnar Geirsson, a cardiovascular scientist at Yale University. Photosynthetic bacteria might also help preserve organs for transplant.

“I’m quite impressed,” Geirsson says. “It’s a really unique way to deliver oxygen.”