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.”

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.

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.