South Korea is very keen on joining the Quad grouping, said the South Korean Envoy in India Chang Jae-bok on Wednesday, according to The Hindu. However, just recently, at the G20 summit, South Korean President Yoon Suk-yeol publicly expressed his hope to promote the stable and healthy development of the South Korea-China relationship. 

Currently, the South Korean government's foreign policy is heavily leaning toward the US, and the eagerness to join the Quad is an extension of this diplomatic policy. The Yoon administration's foreign policy is deeply entrenched in the mind-set of a "new cold war" and cannot extricate itself. 

The South Korean government seems to believe that the world has entered a new cold war and agrees with the US in dividing the world into "liberal" and "authoritarian" camps. In other words, South Korea may acknowledge the need to view non-Western countries as enemies, and cooperation has limitations. South Korea also understands that strengthening relations with the Western camp will lead to friction in the relations between China and South Korea and even on the Korean Peninsula, but it considers this a necessary cost.

The important thing is that South Korea believes that by doing so, it reflects its identity as a "global pivotal state" and assumes global responsibilities. Zhan Debin, director and professor of the Center for Korean Peninsula Studies at the Shanghai University of International Business and Economics, told the Global Times that South Korea, which claims to be the vanguard of safeguarding the order of freedom and democracy, has become an important ally in promoting the US Indo-Pacific strategy in the Asia-Pacific region, which can enhance South Korea's international status. However, this confidence and enthusiasm may only be wishful thinking on the part of South Korea.

Since the Yoon administration came to power, it has shown great confidence in joining the Quad. Due to the influence of the Japan-South Korea relationship at that time, Japan did not want to see South Korea's participation, let alone South Korea decreasing its influence within this small circle. Compared to Japan, India is even less willing to see the Quad become an anti-China and anti-Russia group, as this would diminish India's value. As the leader of the Quad, the US has also not provided much support to South Korea.

Despite the active pressure from the Donald Trump administration for the South Korean government to join the Quad, President Joe Biden has not made a proactive statement on this matter. The Yoon administration believed that as long as South Korea proposed it, the US would immediately agree. However, from the perspective of the US, South Korea's capabilities and contributions, especially in terms of security outside the Korean Peninsula, are limited and cannot be of much help to the US.

If South Korea joins the Quad, the US naturally needs to consider how much contribution South Korea can make within the Quad mechanism. Wu Xinbo, director of the Center for American Studies at Fudan University, told the Global Times that in current Quad mechanism, the US is using India, Japan and Australia to contain China from the Indian Ocean, the West Pacific Ocean and the South China Sea. What can South Korea do? It can at most cooperate with the US and Japan in economic and trade measures to suppress China. In other words, South Korea has not yet proved its capabilities among the Quad countries.

For South Korea, the security of the Korean Peninsula and Northeast Asia should be the most concerning issue. Without cooperation with China, South Korea cannot maintain a stable and peaceful situation in the region. However, the inexperienced administration of Yoon clearly does not realize it. On one hand, it claims to maintain China-South Korea relations, but on the other hand, it continuously tests China's bottom line, which is detrimental to regional peace and stability and does not align with South Korea's own interests. If the Yoon administration wants to manage China-South Korea relations well, it needs to show sincerity. If the trilateral summit between China, Japan, and South Korea is only for showcasing South Korea's leadership and international status, the public's dissatisfaction with the government will only continue to rise.

China's eight-day Mid-Autumn Festival and National Day holidays wrapped up on Friday, with the number of domestic trips and tourism revenue seeing robust growth and exceeding that of 2019, underscoring the robust recovery of the world's second-largest economy.

The bustling scenes seen across the country during the Golden Week holidays offered the latest sign of strong vitality in China's consumption, a major economic growth driver, and the vast potential of China's steady economic recovery, in stark contrast to the dire predictions made by Western media and politicians, analysts said.

While downward pressure remains, China's economy will continue to rebound in the rest of the year and could make a full recovery at the end of 2023, thanks to robust recovery in consumption and other areas and a range of policy measures taken to boost growth, analysts noted.

Bustling tourism

A total of 826 million domestic passenger trips were made in China during the eight-day Mid-Autumn Festival and National Day holidays, a year-on-year increase of 71.3 percent and up 4.1 percent from 2019. Holiday tourism generated 753.43 billion yuan ($104.68 billion), up 129.5 percent year-on-year and 1.5 percent increase from 2019, official data from the Ministry of Culture and Tourism showed on Friday.

Some 59.89 million trips were expected to be made on Friday during the return peak, a year-on-year increase of 58.4 percent, data from the Ministry of Transport showed on Friday. Among them, a total of 18.8 million passengers will travel via the railway with 12,571 trains to be operated, according to China Railway.

Domestic consumption experienced a strong pickup during the holidays, showing the best performance since 2019. For instance, the average daily consumption scale of service retail jumped by 153 percent compared with the same period of 2019, while the consumption scale for dine-in surged by 254 percent, according to data from China's e-commerce platform Meituan.

Multiple provincial-level regions rolled out their tourism reports for the holidays on Friday and Thursday, which returned to or even exceeded the 2019 level.

Shanghai welcomed a total of 21.30 million tourists for the holidays with transactions related to tourism recording a year-on-year increase of 29.7 percent to 29.24 billion yuan, official data showed on Friday.

The Inner Mongolia Autonomous Region received a total of 14.53 million domestic tourists in the first five days of the holidays, a yearly increase of 5.38 times and 1.29 times more than the same period in 2019, thepaper.cn reported on Thursday. The region generated a total of 9.93 billion yuan in tourism revenue, a year-on-year increase of 6.31 times and 1.12 times increase compared with 2019.

Chinese tourists were able to experience the holidays in diverse forms, from touring domestic and international scenic spots and enjoying leisure time in third- and fourth-tier cities to becoming involved in emerging experiences such as cultural and tourism integration projects, night markets, and musicals, according to reports from Chinese travel agencies.

Flight bookings for top domestic destinations during the holidays surged by nearly five times compared to before the COVID-19 pandemic, with bookings for flights departing on September 29 - the first day of the holidays - hitting a record high on Chinese online travel agency platform Qunar, the company told the Global Times on Friday. Bookings for domestic hotels in popular destinations doubled compared with the pre-COVID period. The top destinations included Beijing, Chengdu, Chongqing, Shanghai and other cities.

In addition to visiting well-known cities and metropolises, some Chinese travelers also opted to enjoy the nation's rich cultural heritage and breathtaking natural scenery.

A female traveler surnamed Zhao from Southwest China's Chongqing visited the Bingling Temple Grottoes in Northwest China's Gansu Province -a world cultural heritage with a history stretching back more than 1,600 years. Zhao told the Global Times on Friday that she also encountered some foreign visitors during her visit.

Meanwhile, the ongoing 19th Asian Games in Hangzhou, East China's Zhejiang Province, sparked a consumption craze in sports and related fields throughout the holidays. The order volume for service consumption within the province exceeded 195 percent this year compared with 2019, while the dine-in order volume in Hangzhou increased by 443 percent and orders related to sports and fitness increased by 762 percent, per media reports.

At the same time, outbound tourism witnessed a strong rebound for the recently passed holidays. Orders for overseas travel on Chinese online tourism platform Ctrip.com increased by more than eight times year-on-year, according to a report sent to the Global Times on Friday. Meanwhile, bookings for international flights for the holidays on Fliggy reached a peak within the year.

The boom in tourism also spurred a consumption craze. In the first seven days of the holidays, sales of key monitored retail and dining enterprises increased by 9 percent year-on-year, while the major passenger flow in key commercial areas in 36 cities increased by 164 percent year-on-year, data from the Ministry of Commerce showed on Friday. The domestic box office also topped 2.5 billion yuan, a yearly increase of 70 percent.

Experts attributed the rebound in consumption to China's steady economic recovery and effective macroeconomic stimulus policies, showing the nation's strong resilience and huge potential in consumption, which will also play a vital role in bolstering economic growth in the fourth quarter.

Boosting GDP growth

China's economic performance outperformed 2019 in some aspects after nearly one year of post-epidemic growth, shown by the consumption rebound for the holidays and gradual recovery in trade along with other indicators, Cao Heping, an economist at Peking University, told the Global Times on Friday, expecting a full recovery by the end of 2023 or at the latest by February next year.

China's official manufacturing purchasing managers' index for September came in at 50.2, its first time in positive territory since April and after a consecutive increase over the last four months, the National Bureau of Statistics announced on September 30.

The consumption boom reflected the strong resilience and driving force of the spending power of Chinese residents, Zhang Yi, CEO of iiMedia Research Institute, told the Global Times on Friday.

Cong Yi, a professor at the Tianjin University of Finance and Economics, echoed Zhang's view and added that the targeted policy measures had further noticeable effects during the Golden Week, stressing the importance of continuing to implement the policies moving froward.

Cong told the Global Times on Friday that the consumption rebound during the holidays reflected China's huge consumption potential while also serving as a significant factor to further shore up market confidence and bolster domestic demand.

This confidence will play a vital role in promoting continuous economic growth while also elevating supply, Cong noted.

Zhang expected the consumption momentum to become an indispensable engine for advancing the economy, as the fourth quarter is also a peak season for domestic consumption, with major consumption events like the Double 11 online shopping festival.

In response to the bearish outlook on the Chinese economy painted by some Western media outlets and politicians, experts said China's consumer market is showing strong recovery and growth signs despite downward pressure with its strong market potential, resilience and confidence.

Cong noted that China maintains its market confidence as the world's second-largest consumption market, especially amid the process of rapid structural upgrading. He also stressed the importance of stepping up efforts in sectors such as infrastructure investment and support for the private economy to ignite market dynamics.

China's economic development should be the least worrying one during the global economic recovery process, Cong said.

An extraordinary story has emerged with the recent discovery of a rare fossil dating back approximately 125 million years ago, through joint efforts between Chinese and Canadian researchers. This fossil unveil a remarkable encounter where a large herbivorous dinosaur fell victim to an attack by a carnivorous mammal.

About the size of a large dog, the dinosaur fossil was identified as Psittacosaurus whereas the badger-like mammal fossil is an example of Repenomamus robustus, one of the largest mammals during the Cretaceous - a time when mammals had not yet become the dominant animals on Earth.

The two were found "locked in mortal combat," and "intimately intertwined," said Dr Jordan Mallon, the palaeobiologist with the Canadian Museum of Nature who handled the fossils.

The discovery of these two species Psittacosaurus and Repenomamus robustus was not a "novel finding" in and of itself, but the "predatory behaviour" on display is a rare find, Mallon emphasized.

Wu Xiaochun, a core figure on the project, told the Global Times that the fossils reveal the mammal was not feasting on an already dead dinosaur, but was actively attacking the animal.

"Similar articles that feature a predator mammal have been published before, but only until this one can we show it had its prey alive," said Wu, who is also the head of the Paleobiology Research and Collections Department of the Canadian Museum of Nature.
A typical case of a smaller predator attacking bigger prey, the fossils show, according to Mallon, that they had both lost their lives in the "roily aftermath."

While the fossil had been researched for years since it was first excavated in 2012 in Northeast China's Liaoning Province, the study was only published on Tuesday in Scientific Reports, a scholarly journal. Mallon is the co-author of the paper.

From excavation to publication, Wu played a pivotal role in bringing the researchers from China and Canada together for the project.

In 2012, the fossil was collected in Northeast China's Liaoning Province, more exactly from the Liujitun fossil beds, which are dubbed "China's Dinosaur Pompeii." After excavation, the fossils were in the care of study co-author Dr Han Gang in China, and later Wu helped Han connect with Mallon.

The research projects between China and Canada "will continue in 2023," Wu revealed to the Global Times.

"Joint research projects such as one on a marine reptile in Southwest China's Guizhou Province, is coming along," Wu said.

Some towns in Yancheng, East China's Jiangsu Province, were hit by a tornado on Sunday afternoon. The tornado took two lives and injured 15 people, according to the local authorities. 

The tornado hit Yancheng at around 4:15 pm Sunday, in some towns in Dafeng district, Yancheng, under the influence of strong convective weather. The tornado was identified by experts as EF2 level (medium intensity), China Central Television (CCTV) reported Sunday.

The wind speed of a EF2-level tornado is estimated at 178 to 217 km per hour and usually causes a considerable damage. Under a EF2-level tornado, whole roofs ripped off frame houses, interiors of frame homes damaged, and small, medium, and large trees uprooted. Weak structures such as barns, mobile homes, sheds, and outhouses have been completely destroyed. Cars were lifted off the ground.

According to local authorities, two deaths and 15 injuries were reported from the disaster. All of the injured have been sent to hospital for treatment and none of the injuries are life-threatening. 

According to preliminary verification, 283 agricultural houses and 32 vegetable greenhouses have been damaged. The damage is being further verified, CCTV reported.

All the affected people have now been properly relocated, while post-disaster recovery and reconstruction work is being carried out in an orderly manner, according to CCTV.

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.

When your barista says today’s cuppa joe has rich, spicy notes found only in Colombia’s soil or ‘terroir,’ he or she might not be completely full of … beans.

Before going global, the coffee bean plant originated in Ethiopia, while cacao was first cultivated in the Amazon. Both coffee and cacao beans undergo fermentation prior to roasting. Wild yeast and other microbes that live on the bean digest the pulp that coats the beans, altering flavor and color as well. Researchers wondered, are these yeasts a product of the plants’ current geography or their original roots?

So, they bought unroasted coffee and cacao beans from 27 countries, isolated bean yeasts and analyzed the yeasts’ genes. While coffee and cacao yeasts are even more diverse than wine yeasts, strains that came from the same continents and countries had more in common genetically with their immediate neighbors. Still, some cacao strains from South America share genes with European vineyard yeast and North American oak tree yeast. Such hybrids are probably the result of human trade and travel, the team reports March 24 in Current Biology.

Determining the flavor fallout of all this yeast diversity requires further study, but wine yeasts from different locales are linked to specific chemical profiles.

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.

The sperm whale is one of the odder-looking cetaceans swimming the oceans. Its massive, blocky head is unlike anything sported by other whales. The space above the mouth holds two large, oil-filled organs stacked one on top of the other — the spermaceti organ on top, and another below it called the (we did not make this up) junk. And in the last couple of decades, scientists have determined that the two organs amplify and direct the sonar clicks that the whales use to navigate in the water.

But there have long been suggestions that the massive head could serve another purpose — to ram other whales. The hypothesis dates back to the 19th century, when sperm whales sometimes rammed — and even sank — whaling vessels. “The structure and strength of the whale’s head is admirably designed for this mode of attack,” wrote Owen Chase, first mate of the Essex, which was sank by a whale and inspired the tale of Moby Dick.

Scientists have largely been leery of this hypothesis, though, in part because ramming would risk damage to organs used to generate sound, and because no one had seen a sperm whale ram another. Or at least no one had ever reported such an event in the scientific literature. But a new study, appearing April 5 in PeerJ, shows that Owen and his whaling buddies just may have been right.

Olga Panagiotopoulou of the University of Queensland in Australia and colleagues created computer simulations of a sperm whale’s head and what might happen when the head rammed another object. Partitions of connective tissue inside the junk, they found, appear to reduce the stresses created by impact, “and thus potentially function as a protective mechanism during ramming,” the team writes.

An impact creates tension in the connective tissue that serves as partitions between pockets of oil in the junk. That tension disperses the impact over a greater volume of the head, protecting both bone and soft tissue from injury. When the connective tissue was removed from the simulations, stresses increased by 45 percent and it became more likely that the skull would crack.

Scars on the heads of sperm whales tend to be around the junk, which may indicate that the whales avoid contact over the spermaceti organ — behind which is the whale’s sound generating system, the researchers note. So if the whales are ramming into one another, they probably can do so without hurting their ability to generate sonar clicks.

But are sperm whales really ramming each other? There is other evidence to suggest they just might be. For one, male sperm whales are as much as three times bigger than females, and such size differences are often found in species in which males compete through fighting. There are those sunken whaling ships, too, which add to the argument that ramming behavior may have been something natural for the whales.
But there’s also a report from a wildlife pilot who, on January 30, 1997, while flying over the Gulf of California, saw two males swim directly toward each other at a speed of about 17 kilometers per hour — and then collide, forehead to forehead.

Just before impact, the whales dove just below the surface of the water. That may explain why no one else has reported such sperm whale contests: If they’re occurring below the water’s surface, a person would have to be directly above the event, or in the water with the whales. And besides, if two 50-ton mammals are about to go head-to-head, it might be best to get out of the way.

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.