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.

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.

New observations of the whirling cores of dead stars have deepened the mystery behind a glut of antimatter particles raining down on Earth from space.

The particles are antielectrons, also known as positrons, and could be a sign of dark matter — the exotic and unidentified culprit that makes up the bulk of the universe’s mass. But more mundane explanations are also plausible: Positrons might be spewed from nearby pulsars, the spinning remnants of exploded stars, for example. But researchers with the High-Altitude Water Cherenkov Observatory, or HAWC, now have called the pulsar hypothesis into question in a paper published in the Nov. 17 Science.

Although the new observations don’t directly support the dark matter explanation, “if you have a few alternatives and cast doubt on one of them, then the other becomes more likely,” says HAWC scientist Jordan Goodman of the University of Maryland in College Park.

Earth is constantly bathed in cosmic rays, particles from space that include protons, atomic nuclei, electrons and positrons. Several experiments designed to detect the showers of spacefaring particles have found more high-energy positrons than expected (SN: 5/4/13, p. 14), and astrophysicists have debated the excess positrons’ source ever since. Dark matter particles annihilating one another could theoretically produce pairs of electrons and positrons, but so can other sources, such as pulsars.
It was uncertain, though, whether pulsars’ positrons would make it to Earth in numbers significant enough to explain the excess. HAWC researchers tested how positrons travel through space by measuring gamma rays, or high-energy light, from two nearby pulsars — Geminga and Monogem — around 900 light-years away. Those gamma rays are produced when energetic positrons and electrons slam into low-energy light particles, producing higher-energy radiation.
The size and intensity of the resulting gamma-ray glow indicated that the positrons slowly dissipated away from their pulsar birthplaces, getting bogged down by magnetic fields that permeate the galaxy and twist up the particles’ trajectories. That sluggish departure suggests the particles wouldn’t have made it all the way to Earth, the researchers conclude, and therefore couldn’t explain the excess.

Astrophysicist Dan Hooper of Fermilab in Batavia, Ill., disagrees. He still thinks pulsars are the best explanation for the rogue antimatter. The gamma ray measurements are just one method for studying how cosmic ray particles propagate through space. Other methods indicate that the pulsars’ positrons should be able to make the trek across the galaxy swiftly enough to get to Earth, he says. “I have every confidence that those particles are now reaching the solar system.”

Ruling out pulsars still wouldn’t point the finger at dark matter. “I think they’ve made a good case that these pulsars are not the source,” says astrophysicist Gregory Tarlé of the University of Michigan in Ann Arbor. Instead, Tarlé thinks that scientists can explain the excess positrons by better understanding what happens as cosmic ray particles travel through space. Protons interacting with the interstellar medium — particles that permeate the spaces between stars — could produce positrons that would explain the observations, without invoking either dark matter or pulsars.

The conflict leaves physicists with their work cut out for them. “In order to prove that it’s dark matter, you have to prove that it’s not something ordinary,” says HAWC researcher Brenda Dingus of Los Alamos National Laboratory in New Mexico. Although the new result disfavors the most obvious ordinary candidates, Dingus says, other possibilities are still in the running. “We need to look harder.”

To halt the misuse of opioids, it may help to slash the number of pills prescribed, a new study suggests.

Five months after the implementation of new opioid prescription guidelines at a University of Michigan hospital, roughly 7,000 fewer pills went home with patients — a drop that might reduce the risk of accessible pills leading to substance abuse. But the opioid reduction didn’t leave patients who had undergone a routine surgery with more pain, the team reports online December 6 in JAMA Surgery.
“The decline in opioid volume after the intervention was dramatic,” says physician Mark Bicket of Johns Hopkins University School of Medicine, who was not involved in the study.

Around 50 percent of people who misuse opioids get the drugs from a friend or relative for free, while 22 percent obtain them from a doctor, according to the U.S. Department of Health and Human Services. Michael Englesbe, a surgeon at the University of Michigan in Ann Arbor, says that part of doing a better job of managing patients’ pain “will be preventing chronic opioid use after surgical care and making sure fewer pills get into the community.”

Englesbe and colleagues looked at 170 people who had a minimally invasive surgery to remove their gallbladders at the University of Michigan hospital from 2015 to 2016. All had received a prescription for opioids. Of those patients, 100 completed a survey detailing how much of the prescription they took, whether they also used a common painkiller such as ibuprofen or acetaminophen, and how they rated their pain during the first week after surgery.

The 170 individuals typically received a prescription equivalent to 40 to 60 tablets, each containing 5 milligrams of hydrocodone. Seven of the 170 patients requested an opioid prescription refill. The 100 patients who completed the survey used very little of their prescriptions, usually somewhere from one to 12 pills. And their average pain score on a scale of zero (no pain) to 10 (the worst pain imaginable) was five.
Based on this information, guidelines for opioid prescriptions following the same type of surgery were implemented at the hospital in November of 2016. The researchers recommended prescriptions of 15 opioid pills, plus the use of common painkillers.

In the five months after the guidelines went into effect, 200 patients had the gallbladder surgery. Five of those patients asked for an opioid prescription refill. Eighty-six of the patients filled out the survey and reported that they used even less of their prescriptions — from zero to nine pills — than the pre-guidelines survey group. These patients also noted the same average pain score as the previously surveyed group and similar common painkiller use.

The study demonstrates “a relatively simple intervention at the institutional level with promising results,” Bicket says. “Patients receive opioid prescriptions within a health care system, so it makes sense to focus on getting our systems to work better in reducing the unnecessary supply of opioids after surgery.”

Along with this gallbladder procedure, Englesbe and colleagues have developed opioid prescribing recommendations for other routine surgeries, such as appendix removal and hernia repair, for the state of Michigan.

There have been hints for years that playing football might come at a cost. But a study this year dealt one of the hardest hits yet to the sport, detailing the extensive damage in football players’ brains, and not just those who played professionally.

In a large collection of former NFL players’ postmortem brains, nearly every sample showed signs of chronic traumatic encephalopathy, or CTE, a disorder diagnosed after death that’s associated with memory loss, emotional outbursts, depression and dementia. Damaging clumps of the protein tau were present in 110 of 111 brains, researchers reported in JAMA (SN: 8/19/17, p. 15).
Those startling numbers captured the attention of both the football-loving public and some previously skeptical researchers, says study coauthor Jesse Mez, a behavioral neurologist at Boston University. “This paper did a lot to bring them around.” And that increased awareness and acceptance has already pushed the research further. “The number of brain donors who have donated since the JAMA paper came out has been astronomical,” Mez says.
As the largest and most comprehensive CTE dataset yet, the results described in JAMA are a necessary step on the path to finding ways to treat or prevent CTE, and not just for professional athletes.
Former college and high school football players’ brains were also examined, though in small numbers. Three of 14 high school players and 48 of 53 college players had signs of CTE. Many of the brains were donated by relatives who suspected something was amiss. That skewed sample makes it difficult to draw broad conclusions. Still, the study raised troublesome questions about the safety of youth sports.

Those questions haven’t been answered, though other research this year provided clues. A study of concussed hockey players ages 11 to 14 suggested that young brains may need more time than is usually allotted to heal after a hard knock. Players had troublesome changes in white matter tracts — nerve cell bundles that carry messages across the brain — three months after injury, despite normal thinking and memory abilities, researchers reported in November in Neurology.

To fully understand CTE, scientists need a way to identify and follow the disease as it progresses. A comprehensive study is now under way to look for CTE markers in live people, and has already hit on one clue.

Compared with postmortem brain tissue taken from healthy people and those with Alzheimer’s, tissue from people who had CTE had higher levels of an inflammation protein called CCL11, Mez and other researchers reported in September in PLOS ONE. In people with CTE, the more years that a person played football, the more CCL11. CCL11 levels, or other factors circulating in cerebrospinal fluid or blood, might one day let scientists monitor the brain health of athletes and others exposed to head trauma.

The battle of the sexes, at least among certain ocean mammals, may come down to well-placed skin folds, suggests research by Patricia Brennan, an evolutionary biologist at Mount Holyoke College in South Hadley, Mass., and colleagues.

In some species, enhanced male-female genital fit has evolved over time in ways that make mating easier. This is an example of what scientists call congruent evolution. In other species, genital anatomy reflects a battle, as shape and form change over time to give one sex an edge in control of fertilization. Fittingly, this is called antagonistic evolution.
Brennan’s recent collaboration, examining genitalia of porpoises, dolphins and seals, required extra creativity. In previous studies, her team used saline to inflate preserved penises from birds, snakes, sharks and bats. But the tough, fibroelastic penises of the cetaceans would not inflate with saline alone. So her collaborator, Diane Kelly, a penis biomechanics expert at the University of Massachusetts Amherst, suggested pressurizing the saline with a beer keg.

“We looked at each other and said, ‘This could be the best or worst idea we’ve ever had,’ ” Brennan laughs. But it worked. The scientists then created vaginal endocasts with dental silicone and made 3-D mathematical models to examine male-female fit. The team, led by marine mammalogist Dara Orbach of Dalhousie University in Halifax, Canada, described the work in the Oct. 11 Proceedings of the Royal Society B.

Story continues below image
The results show both antagonistic and congruent coevolution. In the model vaginas of short-beaked common dolphins ( Delphinus delphis) and harbor seals ( Phoca vitulina ), penises encountered no physical barriers to penetration.
But in harbor porpoises (Phocoena phocoena) and bottlenosed dolphins (Tursiops truncatus), the scientists found vaginal folds that may help females physically exert choice over sperm. By subtly changing body position during sex, females may use those folds to decrease penetration depth, reducing the likelihood of fertilization by unwanted males, Brennan says.
Brennan’s work has, understandably, made a splash over the years, attracting media coverage and, in 2013, criticism. Conservative news websites and internet trolls attacked her research, calling it “wasteful government spending.” Surprised by the reaction, Brennan responded publicly with an essay in Slate , arguing that basic science moves society forward and is a valid and valuable use of public funds. The experience convinced her that scientists must defend basic science.
Our ability to innovate is undermined without curiosity-driven science, she says. Brennan has developed an outreach program on basic science and plans to keep expanding knowledge of vertebrate genitalia. “In every species we have looked,” she says, “we have found something weird that nobody else knew.” Reason enough to keep discovering.