Horns, spikes and bony plates—dinosaurs developed many adaptations to protect themselves. But paleontologist Lawrence M. Witmer has discovered that a group of dinosaurs called ankylosaurs had a secret weapon. It was even more important than their tanklike armor, and it was hidden inside their skull: their nasal passages.
Ankylosaurs’ thick full-body armor protected them from predators, but it did not allow much heat to escape from their huge body. Paleontologists were puzzled at how these animals were able to regulate their temperature and survive under the blazing Cretaceous-period sun.
Using advanced scanning and 3-D modeling technologies in his Ohio University lab, Witmer and his colleagues discovered that Euoplocephalus, a genus of ankylosaurs, had strange corkscrew-shaped nasal passages that Witmer likens to a “child’s crazy straw.”
Jason Bourke, a former doctoral student of Witmer’s, now at the New York Institute of Technology College of Osteopathic Medicine at Arkansas State, modeled the dinosaur’s nasal airflow and found the corkscrew shape allowed the passages to act like the coils inside a modern air conditioner. They helped cool ankylosaurs’ blood before it reached the brain, preventing the animals from dying of heat stroke.
Witmer’s study is part of a larger research effort to understand how different groups of dinosaurs dealt with the extreme heat of their environment. In in ankylosaur fossils, the answer was relatively easy to find: their nasal passages were well-preserved inside their bony skull. But the answer is proving more elusive in dinosaurs whose skull had large openings, including long-necked sauropods and carnivorous dinosaurs such as Tyrannosaurus rex.
For Witmer, unearthing this knowledge is not strictly about understanding the giants of the past. “Right now we’re seeing this unprecedented global warming, global climate change, which is disrupting all kinds of weather patterns,” he says. “Dinosaurs, in a sense, can give us some insight into how animals today might be able to deal with this increased heat that we see.”
New research finds they fly around on noise-cancelling wings
By Karen Hopkin
Extreme magnification of moth wing scales.
Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.
[CLIP: Audio of bat calls]
Hopkin: Bats use echolocation to hunt for their meals, and moths are often on the menu. But in the acoustic arms race between predator and prey, moths also have a trick or two up their sleeve—or, actually, on their wings, because a new study shows that moth wings are covered with scales that absorb sound, particularly the ultrasonic variety preferred by bats.
Thomas Neil: So moth and butterfly wings are covered in layers of scales. These are made of a naturally occurring polymer called chitin, which is a polymer you find in most insect and crustacean exoskeletons.
Hopkin: That’s Thomas Neil of the University of Bristol. He started out by bombarding bits of moth wings with sound and seeing what bounced back.
Neil: We discovered that moth scales actually resonate in response to being hit with ultrasound. And they resonate at frequencies that pretty much perfectly match the frequencies that bats use for echolocation.
Hopkin: That vibration converts sound energy to mechanical energy, which muffles the echo that gets back to the bats.
Neil: That probably hasn’t happened by accident, that these scales are such a shape and size that they’re resonating at just the right frequencies that they can absorb sound energy from hunting bats.
Hopkin: Next, Neil and his colleagues modeled the sound-dampening capabilities of an array of different scales.
Neil: The really cool thing about moths is their scales are all different shapes and sizes. So what we found is that each individual scale will resonate at slightly different frequencies—and that, collectively, they actually absorb a really broadband range of frequencies.
Neil: So it means that the moths should be pretty well protected from a whole host of bats that they might interact with out in the wild.
Hopkin: But does the strategy actually work?
Neil: So we don’t actually know how effective these scales are at protecting moths in the real world. But from everything we can model and measure and predict, it seems like they would have quite a considerable advantage in trying to hide these moths from bats hunting at night.
Hopkin: For any bats that might be listening, Neil says there’s not much you can do to thwart this moth maneuver.
Neil: The only real thing that they could do would be to call at higher amplitudes, so to increase the strength of their own echolocation calls such that the echo they got from a moth would be stronger.
Hopkin: In other words, you might catch more moths with a shout than with a whisper.
I am very sure that there is life up there, somewhere in our solar system,” says Christine Moissl-Eichinger, a microbiologist at the Medical University of Graz in Austria. But like any scientist, Moissl-Eichinger knows full well that substantial proof is needed for such a substantial claim. So she and others are working to find that proof—both here on Earth and on Mars.
On the Red Planet, NASA’s Mars rover Perseverance is searching for fossils and traces of alien biochemistry in Jezero Crater, an ancient lake bed thought to have once offered habitable conditions for microbial life. Back home, microbiologists are investigating oxygen-poor environments that may mimic the habitat of early Mars. This two-pronged approach of grounding scientists’ extraterrestrial extrapolations with studies of Earthly analogues could help clarify the bedrock limits for life on rocky planets, greatly aiding the development and execution of future extraterrestrial missions.
The Mars Analogues for Space Exploration project (MASE) was a four-year-long effort that used Earth to understand Mars by analyzing five types of harsh but habitable terrestrial environments that may resemble those that once—or even now—existed on our neighboring planet. Its funding concluded in 2017, but MASE researchers continue to publish results about the habitability of Mars. The study sites included a sulfidic spring, a briny mine, an acidic lake and river, and permafrost. Because of the extreme conditions in these environments, organisms that live here are called extremophiles.
Extremophile research was pioneered by the late Thomas Brock, a microbiologist at the University of Wisconsin–Madison. He found, against all expectations, that certain hardy microbes could thrive in geothermal springs hot enough to poach an egg. The microbiologist’s curiosity led to the isolation of a molecule—from a heat-loving bacterium—that is now used in laboratories across the world to amplify and sequence DNA. Brock passed away in April 2021, but his legacy lives on.
Brock published his extremophile findings in April 1969, mere months before humans first walked on the moon. This paved the way for astrobiology, the study of life in all its forms on this planet and elsewhere in the universe. Astrobiology is not about making money off of space travel, says Luke McKay, a researcher at Montana State University, who was not involved with that study or Moissl-Eichinger’s recent research. It is about basic science and answering a single, timeless question: Does life exist beyond Earth?
This is a question so profound that so far scientists have only managed to chip away at its edges, with each hard-won revelation usually accompanied by a host of newfound mysteries. Moissl-Eichinger and her team’s chief contribution has been their attempt at cultivating extremophiles from MASE’s five environments, but even this straightforward task has been devilishly difficult. Out of more than 1,000 different extremophile species gathered from those sites, the team managed to grow just 31 in the lab. This is a common struggle in environmental microbiology. Because these microbes live in extreme places, it is difficult for researchers to re-create the exact conditions they require to thrive. To capture more of the diversity, the team’s scientists used genetic sequencing, which allowed them to look at all the microbial DNA in their samples. They specifically searched for genes that may help microbes survive hostile conditions, such as extreme temperatures or the absence of oxygen.
“Cultured [microbial] isolates are not representative of the environment, and that’s why it’s really cool what they did. By using isolates and sequencing, I think they really tried to cover all the bases,” McKay says.
Despite their trouble culturing their extremophile samples, the researchers discovered a vast diversity of microorganisms in all five locations. Even in the most extreme Earthly environments, it seems, life indeed finds a way. Most remarkably, the team’s DNA sequencing revealed 34 unique microbial sequences that were conserved in all MASE sites, which is evidence of microbes surviving a combination of extreme environments. According to Moissl-Eichinger, although many microbes are adapted to live in certain conditions such as intense cold or scant oxygen, it is novel to find a group of microbes adapted to survive a combination of these extreme stressors. This ability to survive in many types of environments strengthens the researchers’ claims that similar microbes could exist on Mars—not only in the deep past but even today.
“Microbes are everywhere. They can live in places where we’d expect they could not thrive, but somehow they do,” Moissl-Eichinger says. “Of course, on Mars, we do not know if these [extremophiles] are the types of microorganisms we expect to see. They may just be very adapted to life on Earth.”
One way these microbes may be particularly adapted to our planet is their dependence on carbon-based compounds, or organic matter. These are the molecular building blocks of life on Earth and may be rare in some otherwise habitable extraterrestrial environments. Some microbes in environments with scarce organic matter can instead get nutrients from inorganic substances, such as ammonia and certain sulfur compounds. Yet all the microbes cultured in the MASE studies relied on organic carbon to survive—even those that could survive without oxygen. According to Moissl-Eichinger, this could be because microbes that consume organic matter grow faster. So with more time, she and her colleagues might successfully culture microbes that get their nutrients from other chemical sources, potentially revealing new biochemical pathways and ecological niches to consider when searching for life on Mars.
“We are far away from understanding what microbes could look like on Mars and how we can find them. But of course, research always gives a little piece by piece, and at some point, the picture gets fuller,” Moissl-Eichinger says.
Understanding how all these disparate pieces fit together may change our definition of what it means to be alive. According to McKay, extraterrestrial environments for life may be like those found on Earth, or they could differ vastly. At present, given our sample size of only one confirmed life-bearing world, both possibilities appear equally plausible.
“If [extraterrestrial life] is too [similar] to our life on Earth, people will argue that it is something that we brought with us. But if it is too different, will we be able to see it?” Moissl-Eichinger says. “Now that is the question that drives us.”
LAUNCH SITE ONE, West Texas—The richest person on Earth has now traveled beyond it.
Jeff Bezos, the billionaire founder of the spaceflight company Blue Origin, launched into suborbital space with three other people today (July 20) on the first crewed mission of the company’s New Shepard vehicle—a landmark moment for the man and the space tourism industry.
“Blue Control, Bezos. Best day ever!” Bezos said while in flight.
The autonomous New Shepard, which consists of a rocket topped by a capsule, lifted off from Blue Origin’s Launch Site One near the West Texas town of Van Horn today at 9:11 a.m. EDT (1311 GMT; 8:11 a.m.local time).
The capsule carried Bezos, 57, his brother Mark, 53, 82-year-old aviation pioneer Wally Funk and 18-year-old Dutch physics student Oliver Daemen 66.5 miles (107 kilometers) above Earth, then came down for a parachute-aided, dust-raising landing in the West Texas scrublands. The rocket also returned safely, making a vertical, powered touchdown at its designated landing zone. Its descent was punctuated by a deafening sonic boom, along with raucous cheers from the Blue Origin workers here who watched the flight.
All of this action, from liftoff to landings, took just over 10 minutes. But it was doubtless the experience of a lifetime for the four passengers.
“I’m so excited. I can’t wait to see what it’s going to be like,” Bezos told NBC’s TODAY on Monday (July 19). “People say they go into space and they come back changed. Astronauts always talk about that, whether it’s the thin limb of the Earth’s atmosphere and seeing how fragile the planet is, that it’s just one planet. So I can’t wait to see what it’s gonna do to me.”
Bezos became the second billionaire to reach space in less than two weeks. On July 11, Virgin Group founder Richard Branson flew on the first fully crewed flight of the VSS Unity space plane, which is operated by Virgin Galactic, Blue Origin’s chief rival in the suborbital space tourism business.
Two decades of work
Bezos founded Blue Origin in September 2000, six years after he established Amazon. The spaceflight company worked stealthily for a decade, generally staying out of the public eye.
That changed in 2010, when Blue Origin won a contract from NASA’s Commercial Crew Program, which aimed to encourage the development of private American astronaut taxis to fill the shoes of the space shuttle, which was about to retire. The company snagged another contract the next year but didn’t land the big deal; NASA announced in 2014 that it had selected the vehicles built by SpaceX and Boeing—capsules known as Crew Dragon and CST-100 Starliner, respectively.
Blue Origin continued to work on its own vehicles, including New Shepard, which is designed to carry people and payloads on brief trips to suborbital space. The 59-foot-tall (18 meters) craft is named after NASA astronaut Alan Shepard, whose suborbital jaunt on May 5, 1961, was the United States’ first crewed spaceflight.
New Shepard first launched to suborbital space in April 2015. The capsule landed softly as planned on that flight, but the rocket crashed during its touchdown attempt. But the next New Shepard iteration aced a test flight that November, pulling off the first-ever vertical landing of a rocket during a space mission. (SpaceX nailed a landing of its own a month later with the first stage of its Falcon 9 orbital rocket, a feat Elon Musk’s company has now pulled off more than 80 times.)
In January 2016, the same New Shepard flew successfully again, notching another reusability milestone. Over the next five-plus years, that vehicle and two others flew 12 more uncrewed test missions, the latest an “astronaut rehearsal” this past April.
All were successful, paving the way for today’s mission, which was the third flight of the fourth New Shepard vehicle, known as RSS Next Step.
Making, and acknowledging, history
Blue Origin announced the July 20 target on May 5. Both of those dates were chosen advisedly: May 5 was the 60th anniversary of Shepard’s pioneering flight, and July 20 is the 52nd anniversary of the Apollo 11 moon landing.
Bezos has often cited Apollo 11 as a big inspiration, saying that his dreams of spaceflight were born when he watched the historic lunar landing at the age of five.
Blue Origin made some history of its own today, and not just for the company annals: Funk and Daemen became the oldest and youngest people, respectively, ever to reach the final frontier.
The off-Earth journey was a dose of long-overdue justice for Funk. She’s one of the “Mercury 13,” women who passed NASA’s physiological screening tests in the early days of the space age but were never seriously considered for flight. Back then, you had to be a man—and more specifically, a white military man—to be a NASA astronaut.
The agency didn’t fly a female astronaut to space until June 1983, when Sally Ride reached orbit on the space shuttle Challenger’s STS-7 mission. (Challenger’s STS-8 flight, which launched that August, carried Guion Bluford, the first African American to reach space.)
Funk takes the oldest-spaceflyer mantle from John Glenn, who launched at the age of 77 in October 1998 on the STS-95 mission of the shuttle Discovery, decades after becoming the first American to reach orbit.
Blue Origin announced on July 1 that today’s flight would include Funk. Daemen was a later addition to the manifest; the company revealed his participation just last Thursday (July 16). In mid-June, Blue Origin auctioned off the fourth and final seat on RSS Next Step, for the astronomical sum of $28 million. But the still-anonymous person who placed that bid had scheduling conflicts, company representatives said, so Daemen took their place.
Daemen’s father, Somerset Capital Partners CEO Joes Daemen, paid for the seat and decided to let his son fly, CNBC reported. So, in addition to all the other milestones, RSS Next Step flew its first paying customer today.
Suborbital space tourism lifts off
Virgin Galactic made its big announcement about Branson’s flight on July 1, the same day that Blue Origin did its Funk reveal. The dramatic news drops sparked many stories about a “billionaire space race,” which both Branson and Bezos have attempted to tamp down.
”There’s one person who was the first person in space—his name was Yuri Gagarin—and that happened a long time ago,” Bezos said on TODAY, referring to the cosmonaut’s landmark orbital mission on April 12, 1961. (And Branson wasn’t the first billionaire to reach the final frontier. For example, megarich software architect Charles Simonyi bought two trips to the International Space Station, flying there in 2007 and 2009 aboard Russian Soyuz spacecraft.)
“I think I’m gonna be number 570 or something; that’s where we’re gonna be in this list,” Bezos added. “So this isn’t a competition. This is about building a road to space so that future generations can do incredible things in space.”
Blue Origin aims to help make those incredible things happen over the long haul. The company is building an orbital launch system called New Glenn and a lunar lander named Blue Moon. Blue Origin also leads “The National Team,” a private consortium that proposed a crewed landing system for use by NASA’s Artemis program of lunar exploration. NASA picked SpaceX’s Starship vehicle for that job, but The National Team and another unsuccessful submitter, Alabama-based company Dynetics, have filed protests about the decision with the U.S. Government Accountability Office.
Whether or not there’s personal competition between Branson and Bezos, the companies led by the two billionaires are vying for the same relatively small pool of rich, adventurous customers.
Virgin Galactic’s most recently stated ticket price was $250,000. Blue Origin has not announced how much it’s charging for a regular (non-auctioned) seat, but it’s thought to be in the low six figures as well.
Both companies offer passengers three to four minutes of weightlessness and great views of Earth against the blackness of space. But there are significant differences between the two flight experiences. For example, New Shepard is an autonomous capsule that launches vertically and lands under parachutes, whereas VSS Unity is a two-pilot space plane that takes off under the wing of a carrier aircraft and lands on a runway.
New Shepard also gets a few miles higher than VSS Unity, a fact that Blue Origin highlighted in a couple of Twitter posts on July 9. Those tweets told folks that spaceflights with Virgin Galactic come with an asterisk because Unity doesn’t reach the Kármán line, the 62-mile-high (100 km) mark considered by some to be the point where space begins. (Unity does fly higher than 50 miles, or 80 km, the boundary recognized by NASA, the U.S. military and the Federal Aviation Administration.)
This competition will heat up soon, if all goes according to plan. Blue Origin plans to launch two more crewed New Shepard missions this year, with the next one targeted for September or October, company representatives said during a prelaunch press conference on Sunday (July 18). Those flights will presumably have paying customers on board, just as today’s did.
Virgin Galactic aims to fly a few more test flights this fall, then begin full commercial operations early next year from Spaceport America in New Mexico. Both companies plan to ramp up their flight rate over time, allowing them to reduce prices and broaden the customer pool substantially—perhaps enough for the rest of us to swim in it someday.
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The Borg have landed—or, at least, researchers have discovered their counterparts here on Earth. Scientists analysing samples from muddy sites in the western United States have found novel DNA structures that seem to scavenge and ‘assimilate’ genes from microorganisms in their environment, much like the fictional Star Trek ‘Borg’ aliens who assimilate the knowledge and technology of other species.
These extra-long DNA strands, which the scientists named in honour of the aliens, join a diverse collection of genetic structures—circular plasmids, for example—known as extrachromosomal elements (ECEs). Most microbes have one or two chromosomes that encode their primary genetic blueprint. But they can host, and often share between them, many distinct ECEs. These carry non-essential but useful genes, such as those for antibiotic resistance.
Borgs are a previously unknown, unique and “absolutely fascinating” type of ECE, says Jill Banfield, a geomicrobiologist at the University of California, Berkeley. She and her colleagues describe their discovery of the structures in a preprint posted to the server bioRxiv. The work is yet to be peer-reviewed.
Unlike anything seen before
Borgs are DNA structures “not like any that’s been seen before”, says Brett Baker, a microbiologist at the University of Texas at Austin. Other scientists agree that the find is exciting, but have questioned whether Borgs really are unique, noting similarities between them and other large ECEs.
In recent years “people have become used to surprises in the field of ECEs”, says Huang Li, a microbiologist at the Chinese Academy of Sciences in Beijing. “However, the discovery of Borgs, which undoubtedly enriches the concept of ECEs, has fascinated many in the field.”
Their vast size, ranging between more than 600,000 and about 1 million DNA base pairs in length, is one feature that distinguishes Borgs from many other ECEs. In fact, Borgs are so huge that they are up to one-third of the length of the main chromosome in their host microbes, Banfield says.
Banfield studies how microbes influence the carbon cycle—including the production and degradation of methane, a potent greenhouse gas—and, in October 2019, she and her colleagues went hunting for ECEs containing genes involved in the carbon cycle in Californian wetlands. There, they found the first Borgs and later identified 19 different types from this and similar sites in Colorado and California.
Borgs seem to be associated with archaea, which are single-celled microorganisms distinct from bacteria. Specifically, those Banfield and her team have discovered are linked to the Methanoperedens variety, which digest and destroy methane. And Borg genes seem to be involved in this process, says Banfield.
Scientists can’t yet culture Methanoperedens in the laboratory—an ongoing challenge for many microbes—so the team’s conclusions that Borgs might be used by the archaea for methane processing are based on sequence data alone.
“They’ve made an interesting observation,” says systems biologist Nitin Baliga, at the Institute for Systems Biology in Seattle, Washington. But he cautions that when researchers sift through fragments of many genomes and piece them together, as Banfield’s team has done, it’s possible to make errors. Finding Borgs in cultured Methanoperedens will be necessary for the finding to be considered definitive, he adds.
Costs and benefits
Assuming Borgs are real, maintaining such a massive ECE would be costly for Methanoperedens, Banfield and colleagues say, so the DNA structures must provide some benefit. To learn what that might be, the researchers analysed the sequences of hundreds of Borg genes and compared them with known genes.
Borgs seem to house many genes needed for entire metabolic processes, including digesting methane, says Banfield. She describes these collections as “a toolbox” that might super-charge the abilities of Methanoperedens.
So what makes a Borg a Borg? In addition to their remarkable size, Borgs share several structural features: they’re linear, not circular as many ECEs are; they have mirrored repetitive sequences at each end of the strand; and they have many other repetitive sequences both within and between the presumptive genes.
Individually, these features of Borgs can overlap with those seen in other large ECEs, such as elements in certain salt-loving archaea, so Baliga says the novelty of Borgs is still debatable at this stage. Borgs also resemble giant linear plasmids found in soil-dwelling Actinobacteria, says Julián Rafael Dib, a microbiologist at the Pilot Plant for Microbiological Industrial Processes in Tucumán, Argentina.
Banfield counters that although the individual features of Borgs have been seen before, “the size, combination and metabolic gene load” is what makes them different. She speculates that they were once entire microbes, and were assimilated by Methanoperedens in much the same way that eukaryotic cells gained energy-generating mitochondria by assimilating free-living bacteria.
Now that scientists know what to look for, they might find more Borgs by sifting through old data, says Baker, who used to work in Banfield’s lab. He thinks he might already have discovered some candidates in his own genetic database since the preprint was posted.
Resistance is futile
When analysing the Borg genome, Banfield and colleagues also saw features suggesting that Borgs have assimilated genes from diverse sources, including the main Methanoperedens chromosome, Banfield says. This potential to ‘assimilate’ genes led her son to propose the name ‘Borg’ over Thanksgiving dinner in 2020.
Banfield’s team is now investigating the function of Borgs and the role of their DNA repeats. Repeats are important to microbes: differently-structured repeats called CRISPR are snippets of genetic code from viruses that microbes incorporate into their own DNA to ‘remember’ the pathogens so they can defend against them in the future.
CRISPR and its associated proteins have been a boon for biotechnology because they have been adapted into a powerful gene-editing technique—hinting that Borg genomes might also yield useful tools. “It could be as important and interesting as CRISPR, but I think it’s going to be a new thing,” says Banfield, who is collaborating on future investigations with her preprint co-author, Jennifer Doudna, a pioneer of CRISPR-based gene editing at the University of California.
One potential application that the researchers see for Borgs could be as an aid in the fight against climate change. Fostering the growth of microbes containing them could, perhaps, cut down the methane emissions generated by soil-dwelling archaea, which add up to about 1 gigatonne globally each year. It would be risky to do this in natural wetlands, Banfield says, but it might be appropriate at agricultural sites. So, as a first step, her group is now hunting Borgs in Californian rice paddies.
This article is reproduced with permission and was first published on July 16 2021.
It was late afternoon in the winter scrub desert within Namibia’s Etosha National Park when I spotted a family of elephants on the southern edge of the clearing. I was scanning the horizon from the observation tower where my colleagues and I conduct our research at Mushara water hole. Wind had deterred elephant families from visiting the water hole earlier—it interferes with their efforts to keep tabs on one another vocally—but with the air now still, our first customers of the day had finally appeared.
Judging from how many trunks were stretched high, sampling the air, the group was itching to break cover and run for the water. The young males were particularly anxious to get going. Not only were they thirsty, but they had a lot of sparring to catch up on. As winter wears on, the environment dries out, and elephants have to venture farther from water to find enough to eat. Several days may pass before they can return to the water hole for a drink and a reunion.
I could see why this group was holding back, however. Another elephant family was amassing in the southeastern forest and heading our way, and the adult females were wary. They stood with their feet firmly planted, ears held straight out, as they sniffed what little remained of the prevailing wind for any potential danger. Not only would exiting the security of the forest expose the family to predators, but an encounter with a higher-ranking elephant family could result in an aggressive interaction. For the youngsters in the group, however, more families meant more opportunities to play. So after thoroughly assessing the clearing, the matriarch gave the word with a rumble and an ear flap, and the family began its approach to the water.
Late afternoon is my favorite time of day during our field season in the austral winter—the air cools fast as the sun sinks low in the sky, painting the elephants a radiant pink. My colleagues and I stand in the observation tower with a celebratory drink in hand, our binoculars trained on the horizon, hoping for a sunset visit like this one from one of our beloved resident families. During these daily visits, I always learn a new lesson about elephants—particularly when they play.
I have witnessed the important role of play in calf development and family politics by watching members of my favorite elephant groups frolic at this water hole at sunset. These often chaotic observations inspired me to want to understand more about how animals play and what advantages this behavior might confer, not just to elephants but to all social creatures, including humans. It turns out that play, like other forms of interaction, has rules of engagement. And it is essential for developing the physical and cognitive faculties that animals need to survive and reproduce.
Rules and Regulations
People tend to think of play as an activity one engages in at one’s leisure, outside of learning important skills needed to succeed later in life, such as hunting, mating, and evading predators. But although playing is fun for all involved—and fun for those who are watching—play behaviors evolved as ritualized forms of survival skills needed later in life, providing the opportunity to perfect those skills.
Engaging in play allows animals to experiment with new behaviors in a protected environment without dangerous consequences. The unwritten code of conduct surrounding play lets them explore many possible outcomes.
Animals learn the rules of engagement for play at a very young age. Among dogs, the bow is a universal invitation to engage in silliness that triggers the same bowing down and splaying of the front legs in the receiver of the signal—inevitably followed by chasing and pretend biting. Chimpanzees and gorillas motivate others to romp by showing their upper and lower teeth in what primatologists refer to as a play face, which is comparable to human laughter.
When a young male elephant wants to play with another male of similar age, he holds his trunk up and presents it to the other as an invitation. Most often his next move would be to place his trunk over the other’s head, which in adults signals dominance but in calves is guaranteed to precipitate a spirited sparring match. These encounters run the gamut from gentle shoving to intense headbutting and pushing back and forth with trunks entwining and tusks clacking. The fun continues for seconds to minutes for youngsters; for older teens and young adults, it can go on much longer. The sparring matches provide bulls with the opportunity to test their fighting ability so that they might successfully compete for a female when they reach sexual maturity and enter the hormonal state of musth around the age of 25.
When a young male elephant is feeling particularly adventurous, he may venture far away from Mom’s protection to invite a distant relative to spar. If his foray takes him too far away or if a spar turns unexpectedly rough, the brave calf will lose his nerve and often will run quickly back to Mom’s side with ears flapping and trunk yo-yoing as he retreats.
Occasionally an older sister will oversee a play bout between youngsters. These ever watchful siblings form part of an extended caretaking network that facilitates play, but its members also will intervene if a calf crosses an invisible bloodline and gets deflected with a trunk slap by an overly protective, high-ranking mother.
Forms of Play
Scholars of animal behavior recognize three main categories of play. The first is social play, which is any kind of antic that involves others. The second is locomotive play—including running, walking, jumping and pouncing—which facilitates lifelong motor skills. In prey species, locomotive play helps to perfect predator-avoidance tactics such as the springbok’s “pronking” high into the air while running as a herd and landing in unpredictable spots. In elephants, it hones predator-avoidance skills, as well as strategies for escaping an aggressive suitor or a competitor looking to inflict a mortal wound. Conversely, young predators such as lion cubs use locomotive play to sharpen their hunting ability. Chasing and tripping littermates and then giving them a good chew on the spine or throat are rehearsals of the skills needed to catch prey animals and dispatch them by severing their spinal cord or choking them.
Many species, including our own, engage in the mock-fighting variety of locomotive play, which allows them to test their strength in a safe environment where everyone understands the rules. A playful spar in elephants is just like an arm wrestle between human peers. When play becomes more elaborate and determined, it turns from an arm wrestle into something akin to martial arts, allowing both participants to practice skills and develop innovative solutions that could help them avoid mortal combat later in life. Play fighting also provides opportunities to test boundaries, gauge who can be trusted and learn important body language.
The third main category of play is object play, which incorporates objects from the environment into the cavorting. For an elephant, this object might take the form of a stick or branch that the elephant explores, carries or throws with its trunk. In captivity, elephants enjoy playing with balls or hauling inner tubes around for fun. Alternatively, the object could be another animal, such as a zebra or giraffe, that offers an irresistible opportunity for a chase. In one case, a four-year-old male calf named Leo taught his baby brother, Liam, just how fun such a chase can be, leaving Liam scrambling to keep up with Leo’s charge as a giraffe made a quick escape.
Two other forms of play have been documented only in great apes, including humans. One of these, game playing, combines social, locomotive and object play. Sports such as soccer, field hockey, lacrosse and polo are examples of traditional games that became formalized as sports with specific sets of rules (among nonhuman great apes, only captive individuals raised in human contexts play formal games). The other variety of play that appears to be unique to great apes is make-believe. For example, a wild chimpanzee may carry around a small log, pretending it is an infant. A human child might play with an invisible toy or set up an invisible barrier that they want adults to acknowledge.
Not Just Fun and Games
Play provides an environment for experimenting with risk. When a lion cub deliberately gives up some control over its body, it puts itself at a disadvantage, allowing others to succeed in pouncing on it. Marc Bekoff of the University of Colorado Boulder and his colleagues have proposed that play increases the versatility of movements used to recover from a loss of balance and enhances the ability of the player to cope with unexpected stressful situations. The goal is not to win but to improve skills, sometimes by self-handicapping.
Once a cub has been tackled by its littermates, roles might reverse such that a littermate handicaps itself, allowing the other cub to tackle it in return. Self-handicapping is risky and requires trust, but it is a great way to develop strength and agility. It is also an important exercise in building cooperation. In the Sawtooth wolf pack raised by Jim and Jamie Dutcher in the Sawtooth Mountains in Idaho, the dominant wolf would slow down to allow a close companion that happened to be a subordinate to catch up and tackle him. In elephants, on a number of occasions I have seen older male calves crouch down to allow a much younger calf to spar with them. This is akin to an older brother handicapping himself during an arm wrestle by not using all of his strength to let his little brother win.
Animals learn the rules of engagement for play early on. Among dogs, the “bow” is a universally understood invitation to play (top). Young predators such as lion cubs use play to develop their hunting skills (bottom). Credit: Nicola Gavin/Alamy Stock Photo (top); Manoj Shah/Getty Images (bottom)
Being silly is another important aspect of play, one that gets us outside our comfort zone and forces us to test new strategies. Silliness in our movements, behavior and even language helps us think much more broadly and creatively. Problem-solving derived from the silliness of play has been demonstrated in many species and even in robots. When mechanical engineer Hod Lipson of Columbia University gave his artificial-intelligence robots a chance to play—by dancing around in random movements—they outperformed other robots when challenged with the unexpected. The positioning information garnered from moving around randomly led one robot to come up with creative solutions for maintaining its balance after losing a limb.
Likewise, when sea lions play in the surf, they often project themselves high into the air midway down the face of monster waves, like those that roll into Santa Cruz. These are just the kinds of behaviors needed to avoid an attack by a great white shark—their primary predator apart from killer whales and humans.
Play also builds trust. Thomas Bugnyar of the University of Vienna in Austria and his colleagues found that ravens pretend to cache highly valued food items and then watch how other ravens respond, apparently to determine whom they can trust. Learning how to differentiate competitors from likely reliable collaborators early on has obvious advantages, whether one wants to gain allies or build a coalition within a group—or repair broken relationships.
Families Reunited
“Incoming from the southeast!” I called out from the Mushara tower as my elephant field team narrowed in on what looked like a dusty line of pinkish-gray boulders amassing on the edge of the clearing one afternoon during our 2018 field season. The search for identifying features began. A missing tusk, a notch in the bottom of the left ear, or a V-shaped cut in the top of the right ear would give the family away. Whoever identified the elephant family first would get an extra sundown drink.
That day the incoming family turned out to be the Actors. It was our first sighting of the group that season, and we were excited to see a new addition to the family: high-ranking Susan, identified by her daggerlike left tusk, had a new male calf, Liam. And low-ranking Wynona, who was missing her left tusk, had her two-year-old calf Lucy in tow. We had been following the contentious dynamic between these two mothers very closely over the years, particularly during the 2012 season when each had a calf—Leo and Liza, respectively.
Susan had relentlessly tormented Wynona all the way up to the end of her pregnancy, aggressively charging her whenever she got close to the water to drink. The tension was so high that when Wynona broke away from the family to give birth, surrounded by her daughter Erin and their calves, I worried for her baby’s life if a reunion were to take place. Sure enough, there was no fanfare and no reunion that we witnessed to present her new baby to the rest of the family. I assumed then that Wynona’s days as a member of the Actor family were numbered.
As predicted, Wynona did separate from the larger family and became the matriarch of her own core family. It went on like that for four years until the arrival of Wynona’s newest baby, Lucy, in 2016 yet again changed the dynamic of the larger extended family group. Play appeared to be an important contributing factor in reuniting the family.
Lucy’s older sister, Liza, had been a shy baby who stuck to her mom and her very close relatives. Wynona timed her movements to avoid too much overlap with the larger family group when they went to Mushara water hole to drink. They tended to be one day behind or ahead of the Actor family, usually behind. On the rare occasion that they did overlap just at the end of the extended family visit, Liza did not stray to interact with the larger family. And who would blame her? Susan was right there with a quick jab with her dagger tusk or a trunk slap, whichever was more convenient, making it clear that the low-ranking babies had no place on the playground with royalty. There was hardly a chance for calves of Wynona’s small but growing family to get to know members of the extended family.
Lucy changed all that. From the start, she was quite the extrovert. Maybe being born into a very small family made her all the more curious and excited by the opportunity to engage with the extended family on the infrequent occasion of their overlapping. And she was not deterred by the admonishments of high-ranking moms within the extended family, much to the seeming annoyance of the ever watchful Susan.
Now the two-year-old Lucy knew just how to run through adults’ legs and out of trunk’s reach, navigating potential minefields and dodging her mom’s attempts to rein her in. She behaved more like Susan’s calf, Leo, who was her older sister Liza’s contemporary. When we scored Leo’s distance from his mom at the water hole, he always had a much higher score than Liza. We had assumed that was attributable mainly to his sex and the male elephant’s early experiments with independence. But the arrival of Lucy showed us that the story was not that simple.
Lucy spent a lot of time a great distance away from her mom and played with calves of mothers of all ranks. When it came time to leave the water hole and go in separate directions, as dictated by the prevailing family politics, Lucy made that impossible. She was so busy playing with other calves that there was no extracting her, leaving Wynona no choice but to modify her behavior.
Instead of continuing on her premeditated departure route, in the opposite direction from the Actor family, Wynona, her eldest daughter Erin and their calves turned around and followed the rest of the family so that Wynona did not risk losing her new calf. There was no guarantee that the other mothers would protect Lucy, much less allow her to suckle, as that would mean fewer precious nutrients for their own calves. But by 2018 Wynona was fully reintegrated into the Actor family, whether she wanted to be or not.
Every time I see this dynamic unfold, it makes me smile. How often is it the case in our own families that grudges of older generations are put aside because of the bonds forged by the next generation through play?
Play should be on our daily agenda. Smiling and laughing are contagious behaviors that facilitate bonding, are curative and, most important, do not have to take up much time. The next time you feel like you are too busy to play a frivolous game at work or you don’t want to face that family reunion, make the time and muster the will. You might be surprised at the outcome, whether it be a better idea for a pitch meeting or the dissolution of a long-standing barrier between you and a contentious relative thanks to a good giggle.
Our highly adaptable and innovative nature is rooted in play. I am grateful to my favorite elephant, Wynona, and her daughter Lucy for reminding me that there is always something new we can learn from it—and that we are never too old to internalize those lessons. A good romp can pay off in ways I hadn’t anticipated. It forges new bonds, reunites divided families, improves coping skills and overall health, and facilitates cooperation and innovation. Given all these benefits, how could we afford not to play?
For Blue Origin, this coming moment has been more than two decades in the making.
The spaceflight company founded by billionaire Jeff Bezos is set to launch its first crewed mission on Tuesday (July 20), which will send the billionaire and three other people to suborbital space aboard a reusable rocket-capsule combo called New Shepard. Liftoff is set for 9 a.m. EDT (1300 GMT) from Blue Origin’s Launch Site One near Van Horn, Texas.
The flight is a huge milestone for Blue Origin, which Bezos founded back in September 2000. It will mark the company’s official entry into the suborbital space tourism business, because among New Shepard’s four passengers is its first paying customer, an 18-year-old Dutch man named Oliver Daeman.
Tuesday will also be a very big day for Bezos himself, and not just for professional reasons. The world’s richest person has repeatedly said that traveling to space is a nearly lifelong dream, one inspired when he watched the Apollo 11 moon landing in 1969 at the age of five. And his own flight is a sort of tribute to that epic mission, for it’s launching 52 years to the day that Neil Armstrong and Buzz Aldrin took humanity’s first-ever steps on a world beyond Earth.
New Shepard takes flight
Blue Origin operated very much under the radar for years after its founding. The company really came into the public eye only in 2010, when it won a development contract from NASA’s Commercial Crew Program.
Blue Origin secured another such deal a year later, but NASA ultimately chose SpaceX and Boeing to fly agency astronauts to and from the International Space Station. (SpaceX is in the middle of its third crewed mission to the orbiting lab; Boeing is gearing up for a key uncrewed test flight of its CST-100 Starliner capsule to the station on July 30.)
The company made more news in October 2012 with a successful pad-abort test of New Shepard in West Texas. The crew capsule fired its escape motor and zoomed away from a rocket simulator, showcasing tech that could help keep passengers safe in the event of an emergency during launch.
Then, in April 2015, New Shepard took flight in earnest for the first time. The capsule reached a maximum altitude of 58.1 miles (93.5 kilometers)—higher than the 50-mile (80 km) line that NASA and the U.S. military recognize as the boundary of space—and came back down to Earth safely under parachutes. The rocket didn’t fare quite so well, crashing during its landing attempt.
Seven months later, the next iteration of New Shepard flew even higher, getting about 62.5 miles (100.6 km) above the West Texas scrublands. And this time, both the capsule and the rocket aced their landings—a major milestone, and one that inspired some competitive back-and-forth between Bezos and SpaceX chief Elon Musk. (SpaceX managed to land the first stage of its orbital Falcon 9 rocket just weeks later, a feat Musk’s company has repeated dozens of times since.)
In January 2016, the same New Shepard vehicle flew to suborbital space again, in another landmark reusability moment.
And the test flights continued. To date, four New Shepard vehicles have launched on 15 suborbital missions, the last 14 of which have been completely successful. That string of success has convinced Bezos and the rest of the Blue Origin team that New Shepard is ready to start carrying people—and that Bezos should be among the first to fly.
Billionaires lift off
Blue Origin announced in early May that New Shepard’s first crewed mission would lift off on July 20, and that the company would auction off one of the seats. (In another nod to history, the announcement came on May 5, the 60th anniversary of the first American human spaceflight, the suborbital jaunt of NASA astronaut and New Shepard namesake Alan Shepard.)
A month later, Bezos revealed that he and his brother Mark will be on the flight—news that significantly juiced the auction, which was won by a still-unnamed bidder for $28 million. (That bidder later pulled out of the flight due to scheduling conflicts, according to Blue Origin; his or her spot was taken by Daemen.)
Then, on July 1, Blue Origin announced that trailblazing aviator Wally Funk will be on the flight as well. The 82-year-old is one of the “Mercury 13,” women who passed the same physiological screening tests that NASA put its astronauts through in the early days of the space age. None of those women were seriously considered as astronaut candidates at the time; American human spaceflight was a male-only affair until 1983, when Sally Ride launched to orbit aboard the space shuttle Challenger.
Funk will become the oldest person ever to reach space when New Shepard lifts off on July 20, breaking the record set by then-77-year-old John Glenn during a space shuttle mission October 1998. And Daeman will set a record as well, becoming the youngest-ever spaceflyer.
The same day that Blue Origin announced Funk’s involvement, the company’s main rival in the suborbital space tourism business, Virgin Galactic, came out with a bombshell of its own: It planned to launch its first fully crewed spaceflight on July 11, and billionaire Virgin Group founder Richard Branson would be on board.
This news—and the actual flight, which went well—stole some of Bezos’s thunder. But now it’s Blue Origin’s turn in the spotlight.
Big plans
If all goes according to plan on Tuesday, New Shepard could start full commercial operations in the coming weeks or months. Virgin Galactic aims to do the same in early 2022, after a few more test flights, so a bona fide suborbital space tourism industry may be about to get the ground at long last. (Virgin Galactic was founded in 2004.)
But Blue Origin’s ambitions extend far beyond suborbital space. The company is also developing a huge reusable rocket called New Glenn to carry people and payloads to Earth orbit, with a debut flight expected in 2022.
Blue Origin is working on a moon lander as well, and it leads “The National Team,” a private consortium that proposed a human landing system for use by NASA’s Artemis program of lunar exploration. In April of this year, NASA chose SpaceX’s Starship as the Artemis crewed lander, but The National Team and another finalist that was not selected, Dynetics, filed protests with the U.S. Government Accountability Office, which is expected to issue a decision on the matter in early August.
Blue Origin’s long-term goals are even bolder. The company aims to help humanity become a truly spacefaring species, and to protect our home planet in the process.
“Blue Origin was founded by Jeff Bezos with the vision of enabling a future where millions of people are living and working in space to benefit Earth,” the company’s vision statement reads, in part. “In order to preserve Earth, Blue Origin believes that humanity will need to expand, explore, find new energy and material resources, and move industries that stress Earth into space.”
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Trees that communicate, care for one another and foster cooperative communities have captured the popular imagination, most notably in Suzanne Simard’s much-praised book Finding the Mother Tree, soon to be a movie, and in other works like James Cameron’s Avatar, Peter Wohlleben’s The Hidden Life of Trees and Richard Powers’ Pulitzer Prize–winning novel The Overstory.
But many scientists like myself believe these depictions misrepresent ecosystems and harm the cause of conservation.
Do trees really talk? Sure. Plants emit hormones and defense signals. Other plants detect these signals and alter their physiology accordingly. But not all the talk is kind; plants also produce allelochemicals, which poison their neighbors.
Simard and others showed that carbon compounds made by one tree can end up in neighboring trees via the underground network of mycorrhizae, fungi that live on plant roots and exchange water and nutrients they gather from the soil for sugars plants make. They suggest that donor trees purposely and sacrificially send nourishment to others to help them grow and ensure the health of the community.
How would this work? Like other ecological interactions, cooperation must evolve by natural selection, in which traits increase in frequency because individuals who have them produce more offspring and pass on the traits.
Perhaps the simplest explanation is that the fungus shuttles carbon around to protect its own interests, cultivating multiple hosts to ensure its future supply of food.
Altruism can arise if a recipient is likely to reciprocate, ultimately benefiting the donor. Reciprocity among trees is possible, but many interactions are likely asymmetric, such as between mature trees and tiny seedlings.
Altruistic behavior can also evolve if it benefits relatives, who pass on the donor’s genes. Emerging evidence shows nutrient redistribution via mycorrhizal networks benefits kin more than unrelated plants. The mechanisms by which plants might recognize and respond to their relatives have yet to be fully worked out.
Unfortunately, the explanation most favored by popularizers, that trees send out resources to strengthen the community, is least likely. This would require natural selection to be countered by group selection—where groups that cooperate win out over groups that do not. When these forces conflict, natural selection almost always wins, because individuals are so much more numerous than groups and turn over much more rapidly.
Overemphasizing cooperation is misleading. The forest floor is a forum of fierce competition. A mature maple tree produces millions of seeds, and on average only one will grow to reach the canopy. The rest will die, with or without help from mom.
Amid this struggle, trees can sometimes facilitate each other’s growth. But this does not mean that a forest functions like one organism. An ecosystem comprises an ever-changing diversity of organisms having an ever-changing variety of interactions, positive and negative.
After the last glaciation, different tree species migrated north at different rates and by different routes. The beech-maple forest, or the oak-hickory forest, did not move as a unit. In fact, trees currently live in combinations that may have no analog in the past or future.
Anthropomorphism is taboo in science because it deceives us more often than it helps. Trees are not people and forests are not human families or even republics. Suggesting that they are can only lead us to imaginary conclusions.
In interviews, Simard has said that she purposely uses anthropomorphism and culturally weighted words like “mother”—even though the trees in question are male as well as female—so that people can relate to trees better, because “if we can relate to it, then we’re going to care about it more.”
Do trees need to have human values and emotions for us to let them live? The science supporting conservation is compelling enough. New discoveries about the underground world are thrilling enough. The public deserves to hear the true story, without the confusion of personification and stretched metaphor.
These distractions keep us from confronting reality: facilitation may be real, but so is the Darwinian struggle for existence. We are moral creatures in an amoral world. Nature does not share our values, and mercifully, we may choose not to emulate all of nature’s ways.
Between treating plants as objects or as humans, I suggest a third way: let’s seek to understand plants on their own terms. Plants are fundamentally unlike us: mute, rooted and inscrutable. We need to meet the challenge of cultivating respect for organisms that are different from us—in their separate and complex bodies, in their sophisticated interactions, in their unfathomable lives.
This is an opinion and analysis article; the views expressed by the author or authors are not necessarily those of Scientific American.
The hottest spots in the search for alien life are a few frigid moons in the outer solar system, each known to harbor a liquid-water ocean beneath its icy exterior. There is Saturn’s moon Titan, which hides a thick layer of briny water beneath a frozen surface dotted with lakes of liquid hydrocarbon. Titan’s sister Saturnian moon Enceladus has revealed its subsurface sea with geyserlike plumes venting from cracks near its south pole. Plumes also emanate from a moon that is one planet closer to the sun: Jupiter’s Europa, which boasts a watery deep so vast that, by volume, it dwarfs all of Earth’s oceans combined. Each of these aquatic extraterrestrial locales might be the site of a “second genesis,” an emergence of life of the same sort that occurred on Earth billions of years ago.
Astrobiologists are now pursuing multiple interplanetary missions to learn whether any of these ocean-bearing moons actually possess more than mere water—namely, habitability, or the nuanced geochemical conditions required for life to arise and flourish. NASA’s instrument-packed Europa Clipper spacecraft, for example, could begin its orbital investigations of Jupiter’s enigmatic moon by 2030. And another mission, a nuclear-fueled flying drone called Dragonfly, is scheduled to touch down on Titan as early as 2036. As impressive as these missions are, however, they are only preludes to future efforts that could more directly hunt for alien life itself. But in those strange sunless places so unlike our own world, how will astrobiologists know life when they see it?
More often than not, the “biosignatures” scientists look for in such searches are subtle chemical tracers of life’s past or current presence on a planet rather than anything so obvious as a fossilized form protruding from a rock or a little green humanoid waving hello. The instruments on NASA’s Perseverance Mars rover, for instance, can detect organic compounds and salts in and around its landing site: Jezero Crater, a dry lakebed that may contain evidence of past life. And in the fall of 2020 some astronomers telescopically studying Venus may have teased out the presence of phosphine gas there, a possible by-product of putative microbes floating in temperate regions of the planet’s atmosphere.
The trouble is that many simple biosignatures can be produced both by living things and through abiotic geochemical processes. Much of the phosphine on Earth comes from microbes, but Venus’s phosphine, if it exists at all, could potentially be linked to erupting volcanoes rather than some alien ecosystem in its clouds. Such ambiguities can lead to false positives, cases in which scientists think they see life where none exists. At the same time, if organisms possess radically different biochemistry and physiology from that of terrestrial creatures, scientists could instead encounter false negatives, cases in which they do not recognize life despite having evidence for its presence. Especially when contemplating prospects for life on distinctly alien worlds such as the ocean moons of the outer solar system, researchers must carefully navigate between these two interlinked hazards—the Scylla and Charybdis of astrobiology.
Now, however, a study recently published in the Bulletin of Mathematical Biology offers a novel approach. By shifting attention from specific chemical tracers—such as phosphine—to the broader question of how biological processes reorganize materials across entire ecosystems, the paper’s authors say, astrobiologists could illuminate new types of less ambiguous biosignatures. These clues would be suitable for discovering life in its myriad possible forms—even if that life employed profoundly unearthly biochemistry.
Sizing Up a Sea Change
The study relies on stoichiometry, which measures the elemental ratios that appear in the chemistry of cells and ecosystems. The researchers began with the observation that within groups of cells, chemical ratios vary with striking regularity. The classic example of this regularity is the Redfield ratio—a 16:1 average proportion of nitrogen to phosphorus displayed with remarkable consistency by phytoplankton blooms throughout Earth’s oceans. Other kinds of cells, such as certain types of bacteria, also exhibit their own characteristically consistent ratios. If the regularity of chemical ratios within cells is a universal property of biological systems, here or anywhere else in the cosmos, then careful stoichiometry could be the key to eventually discovering life on an alien world.
Importantly, however, these elemental proportions change in accordance with cell size, allowing for an additional check on any curiously consistent but possibly abiotic chemical ratios on another world. In bacteria, for instance, as cells get larger, concentrations of protein molecules decrease, whereas concentrations of nucleic acids increase. In contrast to groups of nonliving particles, biological particles will display “ratios that systematically change with cell size,” explains Santa Fe Institute researcher Chris Kempes, who led the new study, which expanded on prior work by co-author Simon Levin, also at the Santa Fe Institute. The trick is to devise a general theory of how, exactly, the various sizes of cells affect elemental abundances—which is precisely what Kempes, Levin and their colleagues did.
They focused on the fact that, at least for Earth life, as cell sizes increase in a fluid, their abundance decreases in a mathematically patterned way—specifically, as a power law, the rate of which can be expressed by a negative exponent. This suggests that, if astrobiologists know the size distribution of cells (or cell-like particles) in a fluid, they can predict the elemental abundances within those materials. In essence, this could be a potent recipe for determining whether a group of unknown particles, say within a sample of Europan seawater, harbors anything alive. “If we observe a system where we have particles with systematic relationships between elemental ratios and size, and the surrounding fluid does not contain these ratios,” Kempes explains, “we have a strong signal that the ecosystem may contain life.”
Testing the Waters
The study’s emphasis on such “ecological biosignatures” is the latest in a slow-simmering, decades-long quest to link life not only to the fundamental limitations of physics and chemistry but also to the specific environments in which it appears. It would, after all, be somewhat naive to assume organisms on the sunbathed surface of a warm, rocky planet would have the very same chemical biosignatures as those dwelling within the lightless depths of an oceanic moon. “There has been a constant evolution in ideas, in approaches, and that’s really important,” explains Jim Green, NASA’s chief scientist, who was not involved in the new study. “Now we are entering an era where we can go after what we know about how life has evolved and apply that as a general principle.”
So what does it take to bring this more holistic approach to biosignatures to our studies of worlds such as Europa, Titan and Enceladus? At the moment, Green explains, it will take more than the space agency’s Europa Clipper orbiter—perhaps a follow-up mission to the surface would suffice. “Through Clipper, we want to take much more detailed measurements, fly through the plume, study the evolution of Europa over a period of time and capture high-resolution images,” he says. “This would take us to the next step, which would be to get down to the ground. That’s where the next generation of ideas and instruments need to come in.”
Looking for the ecological biosignatures described by Kempes and his colleagues would require instrumentation that measures the size distribution and chemical composition of cells within their native fluid. On Earth, the technique that scientists use to sort cells by size is called flow cytometry, and it is used frequently in marine environments. But performing cytometry in an alien moon’s subsurface ocean would be far more challenging than merely sending instrumentation there: Because of the paucity of available energy in those sunlight-starved abysses, scientists expect any life there to be single-celled, extremely small and relatively sparse. To capture such organisms in the first place would require careful filtering and then a refined flow cytometer that would measure particles of this size range.
Our current flow cytometers are not up to that task, explains Sarah Maurer, a biochemist and astrobiologist at Central Connecticut University, who was not involved with the study. Many kinds of cells simply do not get picked up, and “there are cell types that require extensive preparation or they won’t go through a cytometer,” she says. To work in space, instruments to filter and sort cells would need both refinement on Earth and miniaturization for spaceflight.
Progress is already being made on both fronts, according to study co-author Heather Graham of the NASA-funded Laboratory for Agnostic Biosignatures and the agency’s Goddard Space Flight Center. The next steps, she says, will be to deploy new tools at marginally habitable field sites around the globe that play host to some of Earth’s most extreme and impoverished ecosystems. Once astrobiologists begin routinely discerning the distinctive chemical ratios associated with living ecosystems in our own planet’s quiescent waters, they can fine-tune the specifications for spaceflight-capable devices—and, just maybe, at last reveal a second genesis, written within the mathematics of a subsurface ocean’s chemistry.
