Nearly 35 percent of a group of 15.8 million Chinese adults were classified as overweight, while the prevalence of overweight and obesity was higher in northern China than southern China, according to media reports on Monday, citing a study on the prevalence of overweight and obesity in China. The topic of obesity triggered a wide discussion online on Monday, with many calling for a focus on healthier lifestyles.

A study titled "Prevalence of obesity and associated complications in China: A cross-sectional, real-world study in 15.8 million adults" was published in Diabetes, Obesity and Metabolism, a journal of pharmacology and therapeutics on August 17.

The study showed a digital version of the China obesity situation based on the BMI (body mass index) classification of overweight and obesity in the country, with 34.8 percent of the 15.8 million adult participants being considered overweight, and 14.1 percent diagnosed as obese.

Being overweight and obesity were more prevalent in male than female participants, with 41.1 percent of male participants being overweight. The prevalence of being overweight peaked at age 50-54 years-old in males and at age 65-69 years-old in females, according to the study.

The study was based on data obtained from 519 Meinian health check-up centers across 243 cities, with eligible participants aged 18 years-old and above. The prevalence rates of overweight and obesity nationwide were standardized according to the 2010 China census by age group and sex, according to the study.

According to both WHO and Chinese BMI classifications, the prevalence of both overweight individuals and obesity was higher in northern China than southern China, with the highest prevalence seen in North China's Inner Mongolia Autonomous Region, East China's Shandong Province and North China's Hebei Province, according to the study. 

Experts have noted that several factors have contributed to the high obesity rates in China such as sedentary lifestyles and a decrease in physical activity. Especially in teenagers, instances of being overweight or obese have become one of the serious challenges faced by young people, as it is reported that about 30 million teenagers are dealing with being either overweight or obese. 

The country has recognized the severity of the obesity and has carried out measures to address the rising trend.  In a notice released in July on improving China's basic public health services in 2023, the country has stressed the work in health services on key groups including prevention of overweight and obesity in children.

In 2020, Chinese authorities set a goal of reducing the average annual growth rates of overweight and obese children and adolescents by 70 percent from a baseline in the next 10 years.

The Senj Wind Farm, a project of the Belt and Road Initiative (BRI), is an example of the mutually beneficial and win-win cooperation between Croatia and China, said Luci Veljacic, manager of the Grupa Company in southern Croatia, in a recent interview with Xinhua.

"For me and my company it was a great honor to be part of the Senj Wind Farm project," Veljacic said, adding that in July 2019, the Grupa Company was offered a contract for supervision and implementation of safety and health protection, fire protection and environmental protection during construction of the Senj Wind Farm project.

Despite numerous unfavourable conditions, including the extremely complex mountainous terrains, the COVID-19 pandemic, snow, strong winds and thunderstorms during the construction process, the Senj Wind Farm, undertaken by China's Norinco International Cooperation Ltd. (Norinco International), was completed on schedule and "without any worker injuries, deaths or incidents," Veljacic noted.

"During the construction, all legal regulations of Croatia and the European Union (EU) and all safety measures were observed to the maximum," Veljacic said.

The Grupa Company is one of the more than 70 contractors from across Croatia participating in the construction, and among the daily turnover of about 300 workers during the construction, more than half of them were from Croatia, Veljacic said, adding that most Croatian workers were from the local Lika-Senj County.

Moreover, participation in the project has made many Croatian companies gain extensive professional experience, which will certainly make them more competitive in the EU market, not just in Croatia, Veljacic said.

Veljacic hailed the "exceptional" cooperation with the Chinese side during the construction process.

"We had an exceptional cooperation, both professional and friendly, with all Chinese companies and workers at the Senj Wind Farm project," Veljacic said, noting that in spite of the language barrier, "we successfully communicated, negotiated, solved daily problems and performed work safely."

In addition, "We also found time to socialize during the project, getting to know the cultures of the two countries ... we talked about history, music, education, customs and the like," Veljacic added.

Veljacic was deeply impressed by the hard work and expertise of the Chinese workers during the construction process.

"During this project, Chinese workers performed the most demanding work and showed exceptional expertise, professionalism, endurance and technological progress," she said, adding that she and her company colleagues also received a lot of help from Chinese engineers who "were always ready to help with their professional knowledge and experience."

The Senj Wind Farm, located on the Adriatic coast of western Croatia and inaugurated in December 2021, produces about 530 million kilowatt-hours (kWh) of green electricity each year and reduces Croatia's carbon dioxide emissions by about 460,000 tonnes per year.

In the eyes of Veljacic, the Senj Wind Farm is a project valuable and important not only for the Lika-Senj County but also for the whole Croatia, as it can significantly contribute to the total annual production of electricity from clean and renewable sources, reduce electricity imports and further promote low-carbon development.

"With this project, Norinco International has become one of the largest investors in green energy and the green economy in Croatia ... The example of the Senj Wind Farm project, the joint successful cooperation of Chinese and Croatian workers and companies will certainly be further developed," Veljacic said.

Most people don’t live close to a coral reef. If we want to visit one, we have to travel far, to the tropical waters that are home to these beautiful and diverse ecosystems. But, it turns out, most coral reefs aren’t that far from people. And it’s those really accessible reefs that we should be worrying about, a new study argues.

Eva Maire of the University of Montpellier in France and colleagues started by breaking up all of the world’s coral reefs into 1-kilometer-square cells. They then calculated how much travel time sat between each of those cells and the nearest human settlement, doing their best to account for whether a person would have to use a boat, a road or a meager track to reach the reef.
Fifty-eight percent of the cells are less than 30 minutes from people, the group reports February 15 in Ecology Letters. Most of those reefs can be found in the Caribbean, the Coral Triangle off Southeast Asia, the Western Indian Ocean and around islands in the Pacific. Others, such as those in the Coral Sea or the northwest Hawaiian Islands, are largely inaccessible, requiring 12 hours or more to reach — too far for a quick fishing jaunt.

Being close to people means that a reef and its resources can be more easily accessed and exploited. Proximity to a market — a source of income for fishermen with easy access to a rich catch — may make that even easier. The researchers found that a quarter of the reefs were within four hours of a major market, and nearly a third were more than 12 hours away. And how close a reef sat to a market appears to matter when it comes to the amount of fish swimming on the reef — those that are closer have lower amounts of fish, the team calculated.

Then the group looked at the pattern of protection for reefs. Many reefs are in marine protected areas that have been set up to limit exploitation. But the reefs most likely to be in a protected area are those that are far from people. An isolated coral reef is more than twice as likely to be protected than average.

The pattern is easy to explain. To set up a protected area, a government has to get everyone who is using that swath of ocean — for fishing, recreation, tourism or anything else — on board with the restrictions that will be placed on usage. And it’s a lot easier to do that with remote patches that not many people are using.

The problem with this, Maire and her colleagues note, is that it means that we may be protecting areas of the ocean that don’t really need protection. And it’s possible that the global goal of protecting 10 percent of the ocean by 2020 “can be met without actually reducing human impacts on the seascape,” they write.

There needs to be more work analyzing the pattern of marine protected areas before any such conclusion can be drawn. And there’s also something to be said for protecting coral reefs now, before they’re totally exploited. Corals already face an uphill battle for survival, given the threats of climate change and ocean acidification. Setting some reefs aside before fishermen and others can do damage doesn’t seem like a bad idea.

BALTIMORE — Metamaterials, among the most intricate and skillfully designed configurations of matter ever devised by science, could be improved with the help of Legos.

Famous for their use in cloaking devices, metamaterials are artificial structures that play unnatural tricks with light and sound and other vibrations. Scientists have investigated the use of such materials for soundproofing rooms or protecting buildings from the shaking of earthquakes, among other things. But to do their jobs, metamaterials must be properly designed and fabricated using precisely manufactured components. Testing ideas for new metamaterials is therefore time-consuming and expensive.
So Paolo Celli and colleagues at the University of Minnesota sought alternatives. They considered 3-D printing, Celli said March 15 at a meeting of the American Physical Society. But the printing process can be slow and the “ink” isn’t cheap, so they rejected that idea. “That’s when we thought, ‘Why don’t we use Lego bricks?’” he said. Legos are relatively cheap and can rapidly be rearranged into all sorts of configurations.

Celli and colleagues arranged Lego bricks on a base plate attached to a wooden frame and investigated how the arrangements influenced the way vibrations traveled through the plate. For some arrangements, certain vibration wavelengths could not be transmitted. Manipulation of the Legos allowed the scientists to determine what processes created the forbidden wavelength zones (known as bandgaps), providing valuable data for future designs of real metamaterials.

Further experiments showed how Lego arrangements could identify metamaterial architectures that might provide a shield for buildings at risk from earthquake waves. “We might be able to design a metamaterial shield that might block some frequencies that can be harmful to that structure,” Celli said.

Ahmed Elbanna, a materials researcher at the University of Illinois at Urbana-Champaign, called the work with Legos exciting and said in principle it could be applicable to designing metamaterials for some applications. He said he was “a little bit more skeptical” that it could result in useful earthquake protection.

Celli emphasized that the motivation behind the work was not solely to produce better metamaterials. “We’ve been looking for an agile and versatile experimental platform,” he said, “but we were also looking for something that people can relate to…. We think that this platform is probably very powerful” for promoting this branch of physics to a broader community.

Asked if he played with Legos as a child, Celli replied, “a lot.”

Resistance may soon be futile. With machine implants worthy of a Star Trek villain, a new breed of beetle takes walking instructions from its human overlords.

Hirotaka Sato and his colleagues at Nanyang Technological University in Singapore inserted electrodes into flower beetles (Mecynorrhina torquata) to stimulate specific leg muscle groups. By altering the order of electrical zap sequences, the team was able to control a beetle’s gait. Changing the duration of the electrical signals also altered the insects’ speed and step length, Sato and colleagues report March 30 in the Journal of the Royal Society Interface.

Scientists have already made cyborg insects that can fly, scuttle, and crawl, but controlling things like speed could allow biobots to do more complex tasks. Cyborg beetles and other insects provide a more energy efficient and easier-to-assemble alternative to plain old robots and double as a means to study insect locomotion, the researchers argue.

Dome effect dōm ih-fekt n.
Airborne black carbon, also called soot, can cause the dome effect by warming the atmosphere’s top layer and blocking sunlight that would otherwise warm the surface air. The reduced temperature difference between the two layers lowers the boundary between them. This effect traps pollution around major cities, worsening air quality, new research suggests.

Researchers observed the dome effect around several of China’s megacities in December 2013. The compressed near-surface layer of the atmosphere led to thick hazes of pollution, the researchers report online March 16 in Geophysical Research Letters. Reducing local black carbon emissions from industry, biofuel burning, diesel vehicles and coal burning would quickly improve air quality around many megacities, the researchers propose.

A century and a half ago, a young paleontologist named Othniel Charles Marsh persuaded his uncle, philanthropist George Peabody, to give Yale University $150,000 for a museum of natural history. And so Yale’s Peabody Museum was born, an institution that has repeatedly upended how people understand Earth’s past. In House of Lost Worlds, Richard Conniff tells the story of the Peabody through the curious characters connected to it.
Marsh is arguably the best known, for his fossil-collecting rivalry with Edward Drinker Cope (the infamous Bone Wars) and as the discoverer (or describer) of Stegosaurus, Brontosaurus, Triceratops and Allosaurus, to name a few. Other characters include James Dwight Dana, who Conniff calls “the Linnaeus of the geological world”; G. Evelyn Hutchinson, the father of modern ecology; and Hiram Bingham III, who brought Machu Picchu to public attention in the 1910s (and is thought, by some, to have been the inspiration for Indiana Jones). The book is celebration, not exposé, but Conniff still conveys the researchers’ full personalities, including their competitive natures, along with academic squabbling.

Squeezed in throughout is the story of the building itself — perpetually undersized and often underappreciated — yet, as Conniff seems to remind us, the place where the soul of the science resides. As Hutchinson said, the museum “began to play a great part in my life as soon as I stepped into it.”

Conniff doesn’t go so far as to suggest that the museum makes the man (and, through no fault of Conniff’s, most of the leading characters are men). But he views the Peabody as a rich repository of knowledge. Its walls enclose over 150 years of insights built on discoveries built on insights, ad infinitum. Without the artifacts brought back from Machu Picchu (later returned to Peru after a bitter battle), anthropologists wouldn’t have redefined the site as an estate for Incan emperors. It was Marsh’s studies of dinosaurs, and horses, that positioned the Peabody to teach evolution when others were attacking it. And the first reconstruction of a feathered dinosaur’s colors (SN: 2/27/10, p. 9) depended on a fossilized squid left mostly unnoticed in the Peabody for over a century.

Throughout the book, Conniff emphasizes the discoveries yet to be made and the pleasure of finding out something new. “Please,” he invites readers, “step inside.”

Raging wildfires could burn away efforts to reduce Arctic-damaging soot emissions. Soot produced by burning fossil fuels and plants, also called black carbon, can cause respiratory diseases and greenhouse warming, and can accelerate the melting of ice.

Rising temperatures and changing weather patterns will shift where and how fiercely wildfires burn and spew soot, new simulations show. Outside of the tropics, fire seasons will last on average one to three months longer during the 2090s than they do currently, researchers report online April 8 in the Journal of Geophysical Research: Atmospheres. Soot emissions from wildfires will as much as double in regions that border the Arctic and counteract projected reductions in soot from human activities, the researchers predict.
“Humankind would do well to proactively develop adequate land and fire management strategies to have at least some control on future wildfire emissions,” says study coauthor Andreas Veira, an earth system scientist at the Max Planck Institute for Meteorology in Hamburg.

Predicting the future of fires is difficult because many factors — from weather to vegetation — influence wildfires. Veira and colleagues strung together three different computer simulations that projected the impact of climate change on wildfires (SN Online: 7/15/15). The first predicted future changes in global vegetation, which fed into the second, a wildfire simulation called SPITFIRE. Finally, the researchers plugged their predicted fires into a climate simulation.

If carbon emissions aren’t cut, overall soot emissions from wildfires will stay fairly steady but shift in location. Outside of the tropics, wildfire soot emissions will increase 49 percent by the end of the century as fire seasons get longer, the researchers predict. In the tropics, changing land usage and fewer human-caused ignitions due to urbanization will help decrease emissions there by 37 percent.

A northward shift in wildfires will push more soot emissions toward the Arctic, the researchers warn. Fallen soot darkens ice and snow, accelerating melting (SN: 10/5/13, p. 26). A 2009 study estimated that soot was responsible for more than a third of Arctic warming between 1976 and 2007. The new simulations show that about 53 percent more soot will fall on the Arctic at the end of the century, even if humans cut their own soot emissions in half.

Many factors that could influence future wildfires remain uncertain, says atmospheric scientist Shane Murphy of the University of Wyoming in Laramie. “We shouldn’t take the absolute numbers to mean too much, just to inform us that there’s the potential for severe consequences.”

A year ago, researchers in two small submarines were exploring a seamount — an underwater, flat-topped mountain — off the Pacific coast of Panama when they noticed a dense cloud of sediment extending 4 to 10 meters above the seafloor. One of the submarines approached closer, and the scientists could soon see what was kicking up the cloud: thousands of small, red crabs that were swarming together like insects.

“The encounter was unexpected and mesmerizing,” Jesús Pineda of the Woods Hole Oceanographic Institution in Massachusetts and colleagues write in a paper published April 12 in Peer J.

The team decided to investigate further. They sent an autonomous underwater vehicle to pass over the swarm several times, capturing images and video of the crabs. At the densest points in the swarm, there were more than 70 crabs in a square meter of ocean bottom, and this occurred consistently in a water depth of 350 to 390 meters. The crabs, all 2.3 centimeters in carapace length and larger, were moving together in the same general direction. Some would jump and swim for about 10 centimeters or so before landing back in the pack.
Using one of the submarines, the researchers collected some crabs from the swarm. Back in the lab in Woods Hole, they used DNA barcoding to identify the species: Pleuroncodes planipes. This is the same species of crab that has sometimes washed up in mass stranding events on California beaches, which the team confirmed by comparing the DNA barcodes to those of crabs from a stranding event in La Jolla, Calif., in June 2015.

For reasons that scientists still don’t fully understand, seamounts are ecological hot spots where plankton get trapped and feed a wide array of fish and marine mammals higher up in the food web. Fishermen have figured out that they can take advantage of this, but scientists are just now getting into the game and exploring these sites. Because of this, less than one percent of the world’s seamounts have been checked out by researchers. That probably explains why no one had seen a crab swarm like this before on a seamount.
But this is not the first time crabs have been seen swarming. Scientists have previously documented large aggregations of king crabs, spider crabs, tanner crabs and lyre crabs on the seafloor. Such behavior may be linked to reproduction.

And then there are the red crabs of Christmas Island in the Indian Ocean, which swarm in the millions during the wet season, coming out of the forests and making a long trek to the beach for a massive mating party.

In a 1967 episode of Star Trek, Captain Kirk and crew investigated the mysterious murders of miners on the planet Janus VI. The killer, it turned out, was a rock monster called the Horta. But the Enterprise’s sensors hadn’t registered any signs of life in the creature. The Horta was a silicon-based life-form, rather than carbon-based like living things on Earth.

Still, it didn’t take long to determine that the Horta was alive. The first clue was that it skittered about. Spock closed the case with a mind meld, learning that the creature was the last of its kind, protecting its throng of eggs.
But recognizing life on different worlds isn’t likely to be this simple, especially if the recipe for life elsewhere doesn’t use familiar ingredients. There may even be things alive on Earth that have been overlooked because they don’t fit standard definitions of life, some scientists suspect. Astrobiologists need some ground rules — with some built-in wiggle room — for when they can confidently declare, “It’s alive!”
Among the researchers working out those rules is theoretical physicist Christoph Adami, who watches his own version of silicon-based life grow inside a computer at Michigan State University in East Lansing.
“It’s easy when it’s easy,” Adami says. “If you find something walking around and waving at you, it won’t be that hard to figure out that you’ve found life.” But chances are, the first aliens that humans encounter won’t be little green men. They will probably be tiny microbes of one color or another — or perhaps no color at all.

By definition
Trying to figure out how to recognize those alien microbes, especially if they are very strange, has led scientists to propose some basic criteria for distinguishing living from nonliving things. Many researchers insist that features such as active metabolism, reproduction and Darwinian evolution are de rigueur for any life, including extraterrestrials. Others add the requirement that life must have cells big enough to contain protein-building machines called ribosomes.

But such definitions can be overly restrictive. A list of specific criteria for life may give scientists tunnel vision, blinding them to the diversity of living things in the universe, especially in extreme environments, says philosopher of science Carol Cleland of the University of Colorado Boulder. Narrow definitions will “act as blinkers if you run into a form of life that’s very different.”

Some scientists, for instance, say viruses aren’t alive because they rely on their host cells to reproduce. But Adami disagrees. “There’s no doubt in my mind that biochemical viruses are alive,” he says. “They don’t carry with them everything they need to survive, but neither do we.” What’s important, Adami says, is that viruses transmit genetic information from one generation to another. Life, he says, is information that replicates.
Darwinian evolution should be off the table, too, Cleland says. Humans probably won’t be able to tell at a quick glance whether something is evolving, anyway. “Evolvability is hard to detect,” she says, “because you’ve got a snapshot and you don’t have time to hang around and watch it evolve.”

Cell size restrictions may also squeeze minuscule microbes out of consideration as aliens. But a cell too tiny to contain ribosomes may still be big enough if it uses RNA instead of proteins to carry out biochemical reactions, says Steven Benner, an astrobiologist at the Foundation for Applied Molecular Evolution in Alachua, Fla. Cells are thought necessary because they separate one organism from another. But layers of clay could provide the needed separation, Adami suggests. Cleland postulates that life could even exist as networks of chemical reactions that don’t require separation at all.

Such fantastical thinking can loosen the grip of rigid criteria limiting scientists’ ability to recognize alien life when they see it. But they will still need to figure out where to look.
Up close and personal
With the discovery in recent years of more than a thousand exoplanets far beyond the solar system, the odds favoring the existence of extraterrestrial life in the cosmos are better than ever. But even the most powerful telescopes can’t detect microscopic organisms directly. Chances of finding microbial life are much higher if scientists can reach out and touch it, which means looking within our solar system, says mineralogist Robert Hazen, of the Carnegie Institution for Science in Washington, D.C.

“You really need a rover down on its hands and knees analyzing chemicals,” Hazen says. Rovers are sampling rocks on Mars (SN: 5/2/15, p. 24) and the Cassini probe has bathed in geysers spewing from Saturn’s icy moon Enceladus (SN: 10/17/15, p. 8). Those mechanical explorers and others in the works may send back signs of life.

But those signs are probably going to be subtle, indirect “biomarkers.” It may be surprisingly difficult to tell whether those biomarkers are from animals, vegetables, microbes or minerals, especially at a distance.

“We really need to have life be as obvious as possible,” says astrobiologist Victoria Meadows, who heads the NASA Astrobiology Institute’s Virtual Planetary Laboratory at the University of Washington in Seattle. By obvious, she partly means Earth-like and partly means that no chemical or geologic process could have produced a similar signature.
Some scientists say life is an “I’ll know it when I see it” phenomenon, says Kathie Thomas-Keprta, a planetary geologist. But life may also be in the eye of the beholder, as Thomas-Keprta knows all too well from studying a Martian meteorite. She was part of a team at the NASA Johnson Space Center in Houston that studied a meteorite designated ALH84001 (discovered in Antarctica’s Allan Hills ice field in 1984).

In 1996, a team led by Thomas-Keprta’s late colleague David McKay claimed that carbonate globules embedded in the meteorite resembled microscopic life on Earth. The researchers found large organic molecules with the carbonate, indicating that they formed at the same time. Thomas-Keprta also identified tiny magnetite crystals overlapping the globules that closely resemble crystals formed by “magnetotactic” bacteria on Earth. Such bacteria use chains of the crystals as a compass to guide them as they swim in search of nutrients. The researchers believed that they were looking at fossils of ancient Martians.

Other researchers disagreed. The globules and crystals could have formed by chemical or geologic processes, not biology, critics said. Since then, the claim of fossilized Martian life has been widely dismissed.

Surely, recognizing something that is still alive, rather than dead and turned to rock, would be much simpler. But don’t bet on it, Cleland says. There may even be strange forms of life on Earth — a shadow biosphere — that people have overlooked.

Desert varnish
One bit of evidence for shadow terrestrials is “desert varnish,” the dark stains on the sunny sides of rocks in arid areas. Odd, communal life-forms could be sucking energy from the rocks and building the varnish’s hard outer crust, Cleland suggests. Some scientists, for instance, think manganese-oxidizing bacteria or fungi might be responsible for concentrating iron and manganese oxides to create the stains. Unknown microbes may cement the metals with clay and silicate particles to produce the varnish’s shellac. Scientists have tried and failed to re-create desert varnish in the lab using fungi and bacteria.
Critics say that varnishes form too slowly — over thousands of years — to be a microbial process and that oxidizing manganese doesn’t generate enough energy to live on. Desert varnish is most likely a product of physical chemistry, they say.

But that criticism shows bias, Cleland responds. “We have an assumption that life on Earth has a pace,” she says. Shadow life may grow far more leisurely, making it hard for scientists to classify it as alive.

One way to determine whether the varnish has a biological or geologic origin is to measure isotope ratios, Cleland says. Isotopes are forms of elements with differing numbers of neutrons in the nuclei of their atoms. Lighter isotopes, with fewer neutrons, are favored by some biochemical reactions.

“Life is lazy,” says Cleland. “It doesn’t want to haul around an extra neutron.” Concentrations of lighter isotopes could signal the handiwork of living organisms, she notes.

Mineral distortions
To find life, and classify it correctly, look for the odd thing out, suggests Hazen, who is looking for messages in minerals. Minerals on Earth are unevenly distributed, he and colleagues have determined. There are 4,933 recognized minerals on the planet. Hazen and colleagues mapped the locations of 4,831 of them and found that 22 percent exist in only one location (SN Online: 12/8/14). Close to 12 percent occur in only two places, the researchers reported last year in The Canadian Mineralogist.

One reason for the skewed distribution is that evolving life has used local resources and concentrated them into new minerals. Take for example hazenite, named for Hazen. The phosphate mineral is produced only by microbes living in California’s Mono Lake. Actions of other species in other places on Earth have combined with the planet’s geology to make Earth’s mineralogy unique, Hazen wrote with colleagues last year in Earth and Planetary Science Letters.

Finding similarly distorted distributions of minerals on other planets or moons could indicate that life exists, or once existed, there. Hazen has advised NASA on how rovers might identify mineral clues to life on Mars.
But determining whether something is unusual might not be as easy as it sounds. Scientists don’t yet know enough about the environment of Mars, Benner says. “Every rover has given us surprises.” He’d like to see a manned fact-finding mission, which he says might lead to a better understanding of the Red Planet and speed up the search for life there.

Mars was once wet (SN Online: 10/8/15) and still has occasional running water (SN: 10/31/15, p. 17). That and other mounting evidence that the Red Planet was once capable of supporting life led Benner to hypothesize in 2013 that Mars may have seeded life on Earth. Whether that hypothesis holds may depend on finding Martians, but Benner doesn’t seem worried.

“I think I would be surprised now if they don’t find life on Mars,” he says. Once the announcement is made, researchers will begin fighting over whether the Martians are real, he predicts. “It will be a good-natured fight because everybody wants to find life, but everybody is aware of the pitfalls of experiments conducted at a 100-million-mile distance by robots.”

Manned missions could easily reach Mars to confirm a find, says Dirk Schulze-Makuch, an astrobiologist at Washington State University in Pullman. “If you have a human with a microscope and the microbe is wiggling and waving back, that’s really hard to refute,” he jokes.

But humans and even probes may have a harder time spotting life on more distant or exotic locales, such as the moons of Jupiter and Saturn. Europa, Enceladus and Titan are frigid places barely kissed by the sun’s energetic rays, but that doesn’t mean they are devoid of life, Schulze-Makuch says. ET hunters are particularly attracted to Europa and Enceladus because liquid oceans slosh beneath their icy crusts. Liquid water is thought to be necessary for many of the chemical reactions that could support life, so it’s one of the primary things astronomers look for.

Going for the less obvious
But water is actually a terrible solvent for forming complex molecules on which life could be based, Schulze-Makuch says. Instead, he thinks, really alien aliens might have spawned at hot spots deep in the hydrocarbon lakes of Saturn’s biggest moon, Titan. There, “you could make something very intriguing. Whether you can get all the way to life, we don’t know,” he says. If he sent a probe to that moon, he would first look for large macro-molecules similar to the DNA, RNA and proteins that Earth life uses, but with a Titanic twist.

He has been studying a natural asphalt lake in Trinidad to learn more about what life in Titan’s lakes might be like. Last July in the journal Life, he and colleagues laid out the physical, chemical and physiological limits that life on Titan would bump up against.

Perhaps the biggest challenge for Titanic life is the extreme cold, says chemical engineer Paulette Clancy of Cornell University. Frosty Titan is so cold that methane — a gas on balmy Earth — is a viscous, almost-freezing liquid, and water “would be like a rock,” she says. Under those conditions, organisms with Earth-like chemistry wouldn’t stand a chance.
For one thing, the membranes that hold in a cell’s guts on Earth wouldn’t work on Titan. Membranes are made of twin sheets of chainlike molecules each with an oxygen-containing head and a long tail of fatty acids. “On Titan,” says Clancy, “long chains would be a disadvantage because they would be frozen in place,” making membranes brittle. Plus, Titan has no free oxygen to form the molecules’ traditional heads.

But Clancy and her Cornell colleagues, chemical engineer James Stevenson and astronomer Jonathan Lunine, simulated experiments under Titan-like conditions. (Molecules that would be stable on Titan would fall apart on Earth, so the researchers had to do computer experiments instead of synthesizing the molecules in a lab.) Short-tailed acrylonitrile molecules with nitrogen-containing heads could spontaneously create stable bubbles called azotosomes, the researchers reported last year in Science Advances. The bubbles are similar to cell membranes.

“Azo” is a prefix that denotes a particular configuration of nitrogen atoms in a molecule. It’s also Greek for “without life.” The word’s meaning “would be ironic if life on Titan were based … on nitrogen,” Clancy says.

Like desert varnish, life on Titan may have unfamiliar pacing that could prevent Earthlings from determining whether azotosomes or other membranous bubbles found in that moon’s methane oceans actually harbor life. With little solar radiation to stimulate evolution and frigid temperatures to slow chemical reactions, life on Titan may be really poky, Schulze-Makuch says. He imagines that Titanic life-spans may stretch to millions of years, with organisms reproducing or even breathing only once every thousand years. Scientists may need to measure metabolic reactions instead of generation times to determine whether something is living on Saturn’s frigid satellite.

Clancy hopes to explore what types of metabolism Titan’s chemistry might allow. Neptune’s icy moon Triton, which is covered in a thin veneer of nitrogen and methane and has nitrogen-spewing geysers, may also be a candidate for new and exciting biochemistry, she says.

With so many options out there, Clancy predicts that there are several planets or moons with life on them. “That we have the lock on the way life decided to develop, I think, is unlikely.”

Many other researchers are also optimistic that life is out there to find. “I think life is a cosmic imperative,” Hazen says. Someday, astrobiologists may come face-to-face with ET. Maybe they will even recognize it when they see it.