Big, rogue planets — ones without parent stars — are rare.

A new census of free-floating Jupiter-mass planets determined that these worlds are a tenth as common as previous estimates suggested. The results appear online July 24 in Nature.

Planets can go rogue in two ways: They can get kicked out of their parent planetary systems or form when a ball of gas and dust collapses (SN: 4/4/15, p. 22).

In the new study, Przemek Mróz of the Astronomical Observatory of the University of Warsaw and colleagues estimated the number of large, rogue planets in our galaxy using a technique called microlensing. When an object with a mass of a planet passes in front of a distant, background star, the gravity of the planet acts as a gravitational magnifying glass. It distorts and focuses the light, giving up the planet’s existence.
Mróz and colleagues looked at 2,617 microlensing events recorded between 2010 and 2015 and determined which were caused by a rogue planet. For every typical star, called main sequence stars, there are 0.25 free-floating Jupiter-mass planets, the analysis suggests.

The new result sharply contrasts an estimate published in 2011, which suggested that rogue Jupiters are almost twice as common as main sequence stars. About 90 percent of stars in the universe are main sequence stars, so if that estimate were accurate, there should be a lot of free-floating Jupiters.

“That result changed our conceptual framework of the universe just a little bit,” says astronomer Michael Liu of the University of Hawaii in Honolulu. It challenged long-held ideas about how planets go rogue because the known methods wouldn’t generate enough planets to account for all the wanderers.

The 2011 result was based on a relatively small sample of microlensing events, only 474. Since then, infrared telescope images haven’t detected as many free-floating planets as expected. “Over the years, serious doubts were cast over the claims of a large population of Jupiter-mass free-floaters,” Mróz says.

David Bennett, coauthor of the 2011 study, agrees that the new census failed to find evidence for a large population of Jupiter-mass rogue planets. He notes, however, that the new data do reveal four times as many Jupiter-mass failed stars called brown dwarfs than predicted in the original census. So some of the rogues that were originally classified as planets may, in fact, be failed stars. Bennett, of NASA’s Goddard Space Flight Center in Greenbelt, Md., and colleagues are working on a new analysis of potential rogues with nearly 3,000 microlensing events and plan to compare their results with those from the new census.
Liu says the latest census is much more in line with theories of how planets form. Most rogues should be Earth-mass or a little heavier. Those lighter planets get tossed out of their planetary systems much easier than behemoths like Jupiter. Still, the smaller planets are harder to detect.

The new microlensing analysis did identify several events in which stars brightened and dimmed in less than half a day. Such short events hint at the existence of Earth-mass free-floaters because smaller planets with less gravity should brighten a distant star more briefly than more massive stars. Determining whether those small planets are really rogue and counting how many there are will take better telescopes, the team notes.

A species gets only one chance to explore its solar system for the first time.

For humans, that chance began 40 years ago this month, when the twin Voyager spacecraft embarked on their “grand tour” of the solar system. A new PBS documentary airing on August 23, The Farthest: Voyager in Space, chronicles their journey to send home the first close-ups of the giant planets and to bring a message about life on Earth to the stars.
Voyagers’ launch dates took advantage of a rare planetary alignment. In 1977, the giant planets — Jupiter, Saturn, Uranus and Neptune — lined up in such a way that a spacecraft could swing past all four in less than 15 years, stealing some gravitational oomph from each world as it went.

That lucky alignment happens only once every 176 years. When NASA’s administrator went to President Richard Nixon to ask for funding for Voyager, he allegedly said: “The last time the planets were lined up like that, President Jefferson was sitting at your desk. And he blew it.”

The Voyagers almost blew it, too. The first craft (Voyager 2, confusingly) launched on August 20, 1977. It experienced so much shaking that its onboard computer — which had as much computing power as a modern car key fob — thought it was failing and put itself in safe mode.
Engineers got it back on track and fixed the problem for Voyager 1’s launch. Then that spacecraft’s rocket had a fuel leak during launch. The craft was within 3½ seconds of running out of gas before it accelerated enough to reach Jupiter.

These nail-biters are mostly told through personal, entertaining anecdotes from Voyager team members. Historical footage from press conferences and newscasts grounds the story in its era. Everyone has big ’70s computers and big ’70s hair. Cuts from shots of the scientists today to their younger selves emphasize how much time has passed. It’s strange that such a high-tech and ambitious mission seems so vintage.

Even the Voyager footage of Jupiter and Saturn coming into view for the first time has a home video quality, especially compared with the sharp, colorful images that spacecraft send back from these planets today. Watching the footage felt like watching video of my parents’ wedding: I recognize everyone, but they look so different.

But the sense of awe that the Voyager images sparked is palpable. At the time, every picture was the best planetary picture ever taken. Much of what is known about the outer solar system now — Jupiter’s moon Io has volcanoes, Europa has an ocean, Neptune has a great churning hurricane that never stops — was glimpsed for the first time with Voyager.

The Voyager spacecraft are still out there, and one may have already left the solar system (SN: 8/23/14, p. 6). Good thing because both craft carry a message in a bottle: the Golden Record.

The Golden Record was a literal record to be played on a phonograph by any aliens that might encounter the spacecraft. The package included a needle, a speaker and graphical instructions on how to play the record. A listener would hear a two-hour sampling of sounds from Earth, including babies crying, whales singing, chimps screeching, trains, thunderstorms, Beethoven, Chuck Berry, greetings in 55 languages and astronomer Carl Sagan’s son saying, “Hello from the children of planet Earth.”

The Farthest weaves the story of exploration with the story of the making of the record. The record’s producers and champions recount how they pulled the whole thing together in just six weeks. What to leave in — a map to Earth, in case the aliens want to visit — and what to leave out — full frontal nudity — was fiercely debated.

At times, refrains of “Wow!” and “It was a first” feel repetitive. Some of the stock footage and spacecraft animations are a little cheesy. But The Farthest is a tender tribute, tinged with nostalgia and existential awe. For those like me, who weren’t alive or aware when the first pictures of Jupiter came back, The Farthest offers a sense of what we missed.

As luck (or exceptionally precise astronomical modeling) would have it, my new, small Oregon town happens to lie in the upcoming eclipse’s path of totality. For nearly two glorious minutes on August 21, we will look up and see the unworldly sight of the moon completely blocking the sun.

To put it mildly, Oregon is going bonkers. Local radio is warning of gas shortages and apocalyptic traffic. Schools and businesses are closing. Emergency services are ramping up for the expected onslaught. Every local store has a pile of eclipse glasses near the register, yours for a very reasonable $2. (Oregonians don’t price gouge.)

I bought glasses (the good kind) for my family and put them in a high drawer. But as a parent to a 2-year-old, I realize that my eclipse prep can’t stop there. I’ve seen what the girl does to regular sunglasses, so I’ve got a few ideas to preschooler-proof these eclipse glasses for her.

Except for during the brief window of totality (when the sun’s surface is completely blacked-out), you shouldn’t look directly at the sun during an eclipse without wearing proper, eclipse-specific eyewear. The powerful light can cause extensive, sometimes permanent eye damage, a condition called solar retinopathy.

As you may imagine, it might be hard to impress this risk on children. Take the cases of these three Australian kids. After watching the 2012 partial eclipse of the sun through binoculars, a 10-year-old boy hurt his eyes. Examinations three months after the injury revealed persistent damage. Another boy, this one 8 years old, stared at the same partial eclipse directly. His eyes showed signs of harm five months later. And an 11-year-old girl who peeked at the 2012 transit of Venus with only her right eye also suffered persistent eye damage.

Those cautionary examples, described in 2015 in the Journal of the American Association for Pediatric Ophthalmology and Strabismus, made me want to duct tape my children’s eclipse glasses to their heads, mummy-style.

In lieu of that, I’m opting for super thick and stretchy fabric bands that I’ll staple and tape to the arms of the glasses. I’m also experimenting with a headband to limit movement on the top of the head, and perhaps even a paper plate taped around the front of the glasses to block incidental light. You could even take a note from 1963 schoolchildren, who put big boxes over their heads to see a projection of an eclipse.
I was happy to see that my DIY ideas aren’t totally off: Amid its wealth of eclipse information, the American Astronomical Society recommends modifying eclipse glasses with elastic or tape around the back so they sit firmly on small faces.

Of course, if you have a little Houdini who regularly squirms out of constricting clothes, you may consider any tweaking to be too risky. A simple pinhole projector, which doesn’t require looking anywhere near the sun, might be better.

Clearly, eye protection is something to take seriously. But don’t let that worry keep you and your children from seeing this once-in-a-lifetime celestial event. It’s the type of natural phenomenon that people — especially really young ones — can grab onto and understand. After all, kids love shadows, and this is going to be one heck of a shadow.

Made out of a mere five molecules, the Ohio Bobcat Nanowagon checks in at 3.5 nanometers long and 2.5 wide — about the width of a DNA strand. Even so, it was the heftiest contender in the first-ever nanocar race earlier this year. This pip-squeak vehicle took home the bronze, but perhaps more importantly, researchers made a surprising observation while manufacturing this model of nanoracer.
About 90 percent of the Bobcat Nanowagons that researchers produced broke apart when the scientists tried attaching them to a racetrack. Most broken bits looked like two-wheel hoverboards.

“It’s very surprising that it seems to be easier to break the chassis than to remove the wheel from the chassis,” study coauthor Eric Masson said August 23 in a news conference at the American Chemical Society Meeting. The type of chemical bond linking atoms in the car frame is typically thought to be stronger than the kind of bond attaching its wheels.

Masson, a chemist at Ohio University in Athens, and colleagues aren’t sure why the Bobcat Nanowagon was more liable to snap in half than lose a wheel. Explaining this chemical quirk could help scientists better understand the operations of molecular machines, which may be useful for transporting information in electronic devices or delivering drugs to specific cells (SN: 10/29/16, p. 6).

In the early evening of March 27, 1964, a magnitude 9.2 earthquake roiled Alaska. For nearly five minutes, the ground shuddered violently in what was, and still is, the second biggest temblor in recorded history.

Across the southern part of the state, land cracked and split, lifting some areas nearly 12 meters — about as high as a telephone pole — in an instant. Deep, house-swallowing maws opened up. Near the coast, ground turned jellylike and slid into bays, dooming almost everyone standing on it. Local tsunamis swamped towns and villages.
Not many people lived in the newly formed state at the time. If the quake had struck in a more developed place, the damage and death toll would have been far greater. As it was, more than 130 people were killed.

In The Great Quake, Henry Fountain, a science journalist at the New York Times, tells a vivid tale of this natural drama through the eyes of the people who experienced the earthquake and the scientist who unearthed its secrets. The result is an engrossing story of ruin and revelation — one that ultimately shows how the 1964 quake provided some of the earliest supporting evidence for the theory of plate tectonics, then a disputed idea.

Using details from his own interviews with survivors — along with newspaper articles, diaries and other published accounts — Fountain focuses his story on two places near Prince William Sound. More people died in the port of Valdez (a familiar name because of the 1989 Exxon Valdez oil spill) than in any other Alaskan community, while the small village of Chenega suffered the highest proportional loss of life. Fountain’s tracking of the myriad small decisions people made that fateful day — that either put them in harm’s way or kept them safe — is meticulous. The experiences of the survivors and the lost are haunting.

Interwoven with stories of the human tragedy is Fountain’s account of the painstaking scientific gumshoe work necessary to piece together how such a monster earthquake had occurred. That’s where George Plafker, a geologist with the U.S. Geological Survey, comes in. In surveying the quake’s aftermath, Plafker, along with others, noticed something strange: There was no surface evidence of a fault large enough to explain the colossal shaking or the widespread uplift and sinking of land over hundreds of thousands of square kilometers.

Today, scientists know that Earth’s outer layer is divided into giant pieces and that the motion of tectonic plates — as they bump together or slide past each other — helps explain how some earthquakes occur. But in the mid-1960s, plate tectonics was just a hypothesis in need of real-world validation.
Plafker’s crucial contribution was to realize that the powerful Alaskan quake had no surface fault because it took place at what is now known as a subduction zone, where dense oceanic crust sinks under lighter continental crust. The insight into the quake’s origin provided some of the first real proof of tectonic plate movements.

Throughout the book, Fountain weaves in brief histories of key people and ideas in the development of the theory of plate tectonics. For those familiar with the history, Fountain doesn’t offer much new. People less familiar may find it a little difficult to keep one geologist straight from another geophysicist.

But The Great Quake is an elegant showcase of how the progressive work of numerous scientists over time — all the while questioning, debating, changing their minds — can be pieced together into an idea that reshapes how we see and understand the planet.

Words can’t describe the pandemonium that follows a child’s birth, but I’ll try anyway. After my first daughter was born, I felt like a giant had picked up my life, shaken it hard, martini-style, and returned it to the ground. The familiar objects in my life were all still there, but nothing seemed to be the same.

The day we came home from the hospital as a family of three, my husband and I plunged headfirst into profound elation and profound exhaustion, often changing by the minute. We worried. We snipped at each other. We marveled at this new, beautiful person. The experience, as new parents the world over know, was intense.

The first week home, my body took a bruising. I was recovering from the wildness that is childbirth. I was insanely thirsty and hungry. I was struggling to both breastfeed and pump every two hours, in an effort to boost my milk supply. And against this backdrop, my levels of estrogen and progesterone, after climbing to great heights during pregnancy, had fallen off a cliff.

Massive reconfigurations were taking place, both in life and in my body. And at times, I felt like the whole thing could go south at any point. After talking to other new mothers, I now realize that almost everyone has a version of this same story. Childbirth and caring for a newborn is really, really hard, in many different ways.

That fraught time can be particularly dangerous for postpartum mood disorders such as depression and anxiety. Unsurprisingly, most women experience mood disturbances in the aftermath of a baby. For the majority, symptoms are mild and ease up with time. But for an estimated 10 to 15 percent of women in industrialized countries and 20 to 40 percent of women in developing countries, symptoms of depression will be troublesome and persistent. And these estimates account for only depression — not anxiety, OCD or other disorders postpartum women sometimes experience.

As a clinical psychologist, Betty-Shannon Prevatt of North Carolina State University in Raleigh saw firsthand how hard the transition to motherhood was for many women. She set out to study why women with postpartum mood disorders often don’t get the help they need.

Along with her colleague Sarah Desmarais, Prevatt surveyed 211 women who had given birth in the previous three years. The researchers asked the women about potential symptoms of mood disorders, whether they had received treatment and, if not, factors that may have kept them from doing so.

I found the results, published August 1 in Maternal and Child Health Journal, shocking. At the time of the survey, 51 percent of the women felt they currently met the criteria for a postpartum mood disorder. That self-report isn’t the same as a diagnosis from a doctor, nor is it indicative of women’s rate overall. But still, the number is high. “I was absolutely surprised,” Prevatt says. The number was especially notable because these are women who would presumably have a good shot at getting help — they are primarily white, married, well-educated and middle class.

The follow-up number is even more worrisome: Twenty percent of the women who self-reported that they were struggling didn’t report their struggles to their health care provider. The two biggest roadblocks to getting help were time constraints (no shock there) and stigma.
A new mother can have trouble finding time to take a shower, let alone to make a doctor’s appointment, call insurance companies, find someone to watch the baby and all the other tasks that go into seeking help. Paid maternity leave policies might help alleviate some of this pressure for women who need to go back to work quickly, the authors write. Strong social support can help, too.

Overcoming stigma is another huge challenge. “Women fear judgment that they are not a good mother … and often feel embarrassed,” Prevatt says.

That has to change. Women ought to be able to seek the help they need without fear or shame. There’s a push among some providers to use a universal screening tool, to ask every postpartum woman about her mental health. But these new results hint that even a universal screen wouldn’t catch women who are ashamed of their illness. For providers to better catch that population, women need to know that they’re experiencing something that’s quite common, and often treatable. “The more we can normalize the wide range of emotions that follow childbirth, the easier it will be for women to disclose how they are truly feeling,” Prevatt says.

The postpartum time can be grueling, even for people lucky enough to not have to deal with a mood disorder. The best we can do is to try and take care of new moms who are giving their all to take care of their baby.

When Hurricane Maria’s 250-kilometer-per-hour winds slammed into Puerto Rico on September 20, they spurred floods, destroyed roads and flattened homes across the island. A week-and-a-half later, parts of the island remain without power, and its people are facing a humanitarian crisis.

The storm also temporarily knocked out one of the best and biggest eyes on the sky: the Arecibo Observatory, some 95 kilometers west of San Juan. The observatory’s 305-meter-wide main dish was until recently the largest radio telescope in the world (a bigger one, the FAST radio telescope, opened in China in 2016).

As news trickled out over the past week, it appeared that the damage may not be as bad as initially reported. The observatory is conserving fuel, but plans to resume limited astronomy observations September 29, deputy director Joan Schmelz tweeted earlier that day. “#AreciboScience is coming back after #MariaPR.”

But the direct whack still raises the issue of when – and even whether – to repair the observatory: Funding for it has repeatedly been on the chopping block despite its historic contributions to astronomy.

Arecibo’s recent work includes searching for gravitational waves by the effect they have on the clocklike regularity of dead stars called pulsars; watching for mysterious blasts of energy called fast radio bursts (SN Online: 12/21/16); and keeping tabs on near-Earth asteroids.

It played a key role in the history of the search for extraterrestrial intelligence: In 1974, astronomers Frank Drake, Jill Tarter and Carl Sagan used it to send messages to any extraterrestrial civilizations that might be listening (SN Online: 2/13/15). It was also the telescope that, in 1992, discovered the first planets outside the solar system.

Arecibo also holds a special place in my personal history: Watching actress Jodie Foster use the giant dish to listen for aliens in the movie Contact when I was 13 cemented my desire to study astronomy. I chose to go to Cornell University for undergrad in part because the university managed Arecibo at the time, and I hoped I might get to go there. (I never did, but my undergrad adviser, Martha Haynes, uses Arecibo to study the distribution of galaxies in the local universe.) And one of the first science stories I ever had published was about Cornell professors testifying to the National Science Foundation, which owns Arecibo, to defend the observatory’s funding.
Ten years after that story ran in the Cornell Daily Sun, Arecibo’s funding situation is still in doubt. It’s not clear how the recent damage will affect its future.

Telescope operator Ángel Vázquez sent the first damage reports via short-wave radio on September 21. A line feed antenna, used to receive and transmit radio waves to study the Earth’s ionosphere, broke off and fell onto the observatory’s main dish, damaging some of its panels. A second, 12-meter dish was thought to have been destroyed entirely.

But the smaller dish survived with only minor damage. “Initial reports said it had just been blown away, but it turned out that was not correct,” says Nicholas White of the Universities Space Research Association, which co-operates the observatory with SRI International, a nonprofit headquartered in Menlo Park, Calif., and Metropolitan University in San Juan, Puerto Rico. “That looks like it’s fine, although obviously we have to get up there and check it out.”

On September 23, observatory director Francisco Córdova posted a picture to the observatory’s Facebook page of two staff members standing in front of the big telescope dish with an outstretched Puerto Rican flag. “Still standing after #HurricaneMaria!” the post declares. “We suffered some damages, but nothing that can’t be repaired or replaced!”
The line feed antenna is a big loss, but it should be replaceable eventually, White says. And the damage to the main dish is fixable. Among the tasks was to get inside the Gregorian dome — the golf ball‒like structure suspended over the giant dish — and make sure the reflectors within it were aligned correctly. (Those reflectors were knocked askew by Hurricane George in 1998, says Cornell radio astronomer Donald Campbell.)

Meantime, Arecibo staff, who managed to safely shelter in place during the storm, “have been showing up for work, funnily enough,” White says. “People just want to get back to normal.”

But normal is also a state of uncertainty. The NSF, which foots $8.3 million of the observatory’s nearly $12 million a year operating costs, has been trying to offload their responsibility for it for several years. (NASA covers the balance.) And NSF’s agreement with the three groups that jointly maintain and operate the observatory runs out in March 2018. In 2016, the NSF called for proposals for other organizations to take over after that.

The NSF can’t estimate yet how expensive the repairs will be or how long they will take to complete, so it’s reserving comment on how the damage will affect decisions about the observatory’s future. “We need to make a complete assessment,” says NSF program director Joseph Pesce.

Personally, I hope the observatory remains open, both for science and for inspiration. I’m still waiting for a reply to that 1974 Arecibo message.

Shellfish stowaways on boat hulls could become castaways, thanks to a superslippery material.

Crowds of mussels can grab onto ships, piers and other infrastructure. They slow down the boats they commandeer, and they’re expensive to remove. The hitchhikers can even travel to new places and become invasive species (SN: 3/18/17, p. 30). A new lubricant-infused material could one day help prevent mussels from getting a grip in the first place, scientists report in the Aug. 18 Science.
Researchers modified a flexible silicone material to which Asian green mussels (Perna viridis) ordinarily stick liberally, suffusing it with a silicone lubricant. Some of the lubricant forms a thin, liquid layer and smooths out any microscopic roughness on the material’s surface; the rest creates a reservoir within the material’s pores. When the top layer wears off, the reservoir replenishes it.

Normally, mussels probe a surface with a footlike appendage and then send out a sticky thread to latch on. But mussels trying to attach to the lubricant-infused material either didn’t send out those threads at all or directed them to the wrong target — to the animals’ own shell or a different surface. That misfire suggests that the shellfish didn’t recognize the lubricated surface as a place to cling to, says study coauthor Joanna Aizenberg, an engineer at Harvard University.
She and colleagues are already commercializing lubricated coatings for use in other applications, such as implanted medical devices where it’s crucial that blood or bacteria not hold on to a surface. Next stop, the slippery coatings could take to the seas.

High-energy particles from outer space have helped uncover an enigmatic void deep inside the Great Pyramid of Giza.

Using high-tech devices typically reserved for particle physics experiments, researchers peered through the thick stone of the largest pyramid in Egypt for traces of cosmic rays and spotted a previously unknown empty space. The mysterious cavity is the first major structure discovered inside the roughly 4,500-year-old Great Pyramid since the 19th century, researchers report online November 2 in Nature.
“It’s a significant discovery,” says Peter Der Manuelian, an Egyptologist at Harvard University not involved in the work, “although precisely what it means is unclear.”

The open space may comprise one or more rooms or corridors, but the particle-detector images reveal only the rough size of the void, not the details of its design. Eventually, though, this detail of the Great Pyramid’s architecture could offer new insights into one of the world’s largest, oldest and most famous monuments. The only one of the ancient Seven Wonders of the World that’s still standing, the Great Pyramid was built as a burial tomb for Pharaoh Khufu.
“Imagine you’re an archaeologist and you walk into this room no one has walked in for [over] 4,000 years,” says Nural Akchurin, a physicist at Texas Tech University in Lubbock who wasn’t involved in the study. “That’s huge. It’s incredible.”
Researchers probed the Great Pyramid’s interior with devices that sense muons — by-products of spacefaring subatomic particles called cosmic rays striking atoms in the atmosphere. Muons continuously rain on Earth at nearly the speed of light. But while the subatomic particles easily streak through open air, rock can absorb or deflect them. By placing detectors near the base and areas deep inside of the Great Pyramid and measuring the number of muons that reach the detectors from different directions, scientists could spot empty spaces inside the ancient edifice.

For instance, if a detector inside the pyramid picked up slightly more muons from the north than the south, that would indicate there was slightly less rock on the north side to intercept incoming muons. That relative abundance of muons could indicate the presence of a chamber in that direction.

Muon imaging an enormous, dense construction like the Great Pyramid “is not an easy game,” Akchurin says. The monument obstructs 99 percent of incoming muons before the particles can reach detectors, so collecting enough data to spot its hollow spaces takes several months.
The newly identified void was first seen with a type of muon detector called nuclear emulsion film, which the researchers laid out in a space called the Queen’s chamber and the adjacent corridor inside the pyramid. When muons zip through these films, the particles’ chemical interactions with the material leave silver trails that reveal which direction the particles came from, explains Elena Guardincerri, a physicist at Los Alamos National Laboratory in New Mexico not involved in the work.

Upon developing these films, the researchers saw a surprising excess of muons coming through a region above the Grand Gallery, a sloping corridor that runs north-south through the center of the pyramid. The cavity appears to be at least 30 meters across — about the size of the Grand Gallery itself. “Our first reaction was a lot of excitement,” says study coauthor Mehdi Tayoubi, cofounder of the Heritage Innovation Preservation Institute in Paris. “We said, ‘Wow, we got something big!’”

Tayoubi and colleagues confirmed their discovery with observations from two other types of muon detectors, which generate electrical signals when muons pass through them, placed inside the Queen’s chamber and outside at the base of the pyramid.

Akchurin hopes this finding will pave the way for muon imaging of other ancient monuments around the world — particularly at archaeological sites where traditional excavation may be difficult, like deep in the jungle or on mountainsides.

Finding the chemical basis for the close association between the Attine ants, inhabiting an area extending from Argentina to the southern United States, and the fungus they culture is the aim of research … by Prof. Michael M. Martin of the University of Michigan. Although many animals feed on fungi, the culturing of fungus by the Attine ants is the only known example of creatures growing their own. — Science News, November 11, 1967

Update
Attine ants, a group of more than 200 species, began cultivating fungus “gardens” for food around 60 million years ago. Total codependence between the ants and fungi evolved around 30 million years ago, scientists wrote in April in Proceedings of the Royal Society B. During a global shift to a more arid climate with long seasonal dry periods, the moisture-loving fungi may have had a harder time surviving outside of ant-tended plots. Ants also became more dependent on fungi, losing, among other things, the ability to produce the amino acid arginine.