Lava tubes on Mars and the Moon are so wide they can host planetary bases

 Researchers at the Universities of Bologna and Padua studied the subsurface cavities that lava created underground on Mars and the Moon. These cavities can shield from cosmic radiation.

The international journal Earth-Science Reviews published a paper offering an overview of the lava tubes (pyroducts) on Earth, eventually providing an estimate of the (greater) size of their lunar and Martian counterparts.

This study involved the Universities of Bologna and Padua and its coordinators are Francesco Sauro and Riccardo Pozzobon. Francesco Sauro is a speleologist and head of the ESA programmes CAVES and PANGAEA, he is also a professor at the Department of Biological, Geological, and Environmental Sciences at the University of Bologna. Riccardo Pozzobon is a planetary geologist at the Department of Geosciences of the University of Padua.

"We can find lava tubes on planet Earth, but also on the subsurface of the Moon and Mars according to the high-resolution pictures of lava tubes' skylights taken by interplanetary probes. Evidence of lava tubes was often inferred by observing linear cavities and sinuous collapse chains where the galleries cracked," explains Francesco Sauro. "These collapse chains represent ideal gateways or windows for subsurface exploration. The morphological surface expression of lava tubes on Mars and the Moon is similar to their terrestrial counterpart. Speleologists thoroughly studied lava tubes on Earth in Hawaii, Canary Islands, Australia and Iceland."

"We measured the size and gathered the morphology of lunar and Martian collapse chains (collapsed lava tubes), using digital terrain models (DTMs), which we obtained through satellite stereoscopic images and laser altimetry taken by interplanetary probes," reminds Riccardo Pozzobon. "We then compared these data to topographic studies about similar collapse chains on the Earth's surface and to laser scans of the inside of lava tubes in Lanzarote and the Galapagos. These data allowed to establish a restriction to the relationship between collapse chains and subsurface cavities that are still intact."

Researchers found that Martian and lunar tubes are respectively 100 and 1,000 times wider than those on Earth, which typically have a diameter of 10 to 30 meters. Lower gravity and its effect on volcanism explain these outstanding dimensions (with total volumes exceeding 1 billion of cubic meters on the Moon).

Riccardo Pozzobon adds: "Tubes as wide as these can be longer than 40 kilometres, making the Moon an extraordinary target for subsurface exploration and potential settlement in the wide protected and stable environments of lava tubes. The latter are so big they can contain Padua's entire city centre."

"What is most important is that, despite the impressive dimension of the lunar tubes, they remain well within the roof stability threshold because of a lower gravitational attraction," explains Matteo Massironi, who is professor of Structural and Planetary Geology at the Department of Geosciences of the University of Padua. "This means that the majority of lava tubes underneath the maria smooth plains are intact. The collapse chains we observed might have been caused by asteroids piercing the tube walls. This is what the collapse chains in Marius Hills seem to suggest. From the latter, we can get access to these huge underground cavities."

Francesco Sauro concludes: "Lava tubes could provide stable shields from cosmic and solar radiation and micrometeorite impacts which are often happening on the surfaces of planetary bodies. Moreover, they have great potential for providing an environment in which temperatures do not vary from day- to night-time. Space agencies are now interested in planetary caves and lava tubes, as they represent a first step towards future explorations of the lunar surface (see also NASA's project Artemis) and towards finding life (past or present) in Mars subsurface."

Researchers also point out how this study opens up to a completely new perspective in planetary exploration, which is increasingly focusing on the subsurface of Mars and the Moon.

"In autumn 2019, ESA called up universities and industries with a campaign seeking ideas for developing technologies for lunar caves exploration. They are specifically looking for systems that would land on the lunar surface to operate missions exploring lunar tubes," clarifies Unibo professor Jo De Waele, who is one of the authors of the study and a speleologist. "Since 2012, in collaboration with some European universities including Bologna and Padua, ESA has been carrying out two training programmes for astronauts focusing on the exploration of underground systems (CAVES) and planetary geology (PANGAEA). These programmes include lava tubes on the island of Lanzarote. So far, 36 astronauts from five space agencies have received training in cave hiking; moreover, six astronauts and four mission and operation specialists have received geological field training."

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Stellar egg hunt with ALMA

 Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) took a census of stellar eggs in the constellation Taurus and revealed their evolution state. This census helps researchers understand how and when a stellar embryo transforms to a baby star deep inside a gaseous egg. In addition, the team found a bipolar outflow, a pair of gas streams, that could be telltale evidence of a truly newborn star.

Stars are formed by gravitational contraction of gaseous clouds. The densest parts of the clouds, called molecular cloud cores, are the very sites of star formation and mainly located along the Milky Way. The Taurus Molecular Cloud is one of the active star-forming regions and many telescopes have been pointed at the cloud. Previous observations show that some cores are actually stellar eggs before the birth of stars, but others already have infant stars inside.

A research team led by Kazuki Tokuda, an astronomer at Osaka Prefecture University and the National Astronomical Observatory of Japan (NAOJ), utilized the power of ALMA to investigate the inner structure of the stellar eggs. They observed 32 starless cores and nine cores with baby protostars. They detected radio waves from all of the nine cores with stars, but only 12 out of 32 starless cores showed a signal. The team concluded that these 12 eggs have developed internal structures, which shows they are more evolved than the 20 quite cores.

"Generally speaking, radio interferometers using many antennas, like ALMA, are not good at observing featureless objects like stellar eggs," says Tokuda. "But in our observations, we purposely used only the 7-m antennas of ALMA. This compact array enables us to see objects with smooth structure, and we got information about the internal structure of the stellar eggs, just as we intended."

Increasing the spacing between the antennas improves the resolution of a radio interferometer, but makes it difficult to detect extended objects. On the other hand, a compact array has lower resolution but allows us to see extended objects. This is why the team used ALMA's compact array of 7-m antennas, as known as the Morita Array, not the extended array of 12-m antennas.

They found that there is a difference between the two groups in the gas density at the center of the dense cores. Once the density of the center of a dense core exceeds a certain threshold, about one million hydrogen molecules per cubic centimeter, self-gravity leads the egg to transform into a star.

A census is also useful for finding a rare object. The team noticed that there is a weak but clear bipolar gas stream in one stellar egg. The size of the stream is rather small, and no infrared source has been identified in the dense core. These characteristics match well with the theoretical predictions of a "first hydrostatic core," a short-lived object formed just before the birth of a baby star. "Several candidates for the first hydrostatic cores have been identified in other regions," explains Kakeru Fujishiro, a member of the research team. "This is the first identification in the Taurus region. It is a good target for future extensive observation."

Kengo Tachihara, an associate professor at Nagoya University mentions the role of Japanese researchers in this study. "Japanese astronomers have studied the baby stars and stellar eggs in Taurus using the Nagoya 4-m radio telescope and Nobeyama 45-m radio telescope since the 1990s. And, ALMA's 7-m array was also developed by Japan. The present result is part of the culmination of these efforts."

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DNA from an ancient, unidentified ancestor was passed down to humans living today

 A new analysis of ancient genomes suggests that different branches of the human family tree interbred multiple times, and that some humans carry DNA from an archaic, unknown ancestor. Melissa Hubisz and Amy Williams of Cornell University and Adam Siepel of Cold Spring Harbor Laboratory report these findings in a study published 6th August in PLOS Genetics.

Roughly 50,000 years ago, a group of humans migrated out of Africa and interbred with Neanderthals in Eurasia. But that's not the only time that our ancient human ancestors and their relatives swapped DNA. The sequencing of genomes from Neanderthals and a less well-known ancient group, the Denisovans, has yielded many new insights into these interbreeding events and into the movement of ancient human populations. In the new paper, the researchers developed an algorithm for analyzing genomes that can identify segments of DNA that came from other species, even if that gene flow occurred thousands of years ago and came from an unknown source. They used the algorithm to look at genomes from two Neanderthals, a Denisovan and two African humans. The researchers found evidence that 3 percent of the Neanderthal genome came from ancient humans, and estimate that the interbreeding occurred between 200,000 and 300,000 years ago. Furthermore, 1 percent of the Denisovan genome likely came from an unknown and more distant relative, possibly Homo erectus, and about 15% of these "super-archaic" regions may have been passed down to modern humans who are alive today.

The new findings confirm previously reported cases of gene flow between ancient humans and their relatives, and also point to new instances of interbreeding. Given the number of these events, the researchers say that genetic exchange was likely whenever two groups overlapped in time and space. Their new algorithm solves the challenging problem of identifying tiny remnants of gene flow that occurred hundreds of thousands of years ago, when only a handful of ancient genomes are available. This algorithm may also be useful for studying gene flow in other species where interbreeding occurred, such as in wolves and dogs.

"What I think is exciting about this work is that it demonstrates what you can learn about deep human history by jointly reconstructing the full evolutionary history of a collection of sequences from both modern humans and archaic hominins," said author Adam Siepel. "This new algorithm that Melissa has developed, ARGweaver-D, is able to reach back further in time than any other computational method I've seen. It seems to be especially powerful for detecting ancient introgression."

 From Science Daily

New insight into the evolution of complex life on Earth

 A novel connection between primordial organisms and complex life has been discovered, as new evidence sheds light on the evolutionary origins of the cell division process that is fundamental to complex life on Earth.

The discovery was made by a cross-disciplinary team of scientists led by Professor Buzz Baum of University College London and Dr Nick Robinson of Lancaster University.

Their research, published in Science, sheds light on the cell division of the microbe Sulfolobus acidocaldarius, which thrives in acidic hot springs at temperatures of around 75?C. This microbe is classed among the unicellular organisms called archaea that evolved 3.5 billion years ago together with bacteria.

Eukaryotes evolved about 1 billion years later -- likely arising from an endosymbiotic event in which an archaeal and bacterial cell merged. The resulting complex cells became a new division of life that now includes the protozoa, fungi, plants and animals.

Now a common regulatory mechanism has been discovered in the cell division of both archaea and eukaryotes after the researchers demonstrated for the first time that the proteasome -- sometimes referred to as the waste disposal system of the cell -- regulates the cell division in Sulfolobus acidocaldarius by selectively breaking down a specific set of proteins.

The authors report: "This is important because the proteasome has not previously been shown to control the cell division process of archaea."

The proteasome is evolutionarily conserved in both archaea and eukaryotes and it is already well established that selective proteasome-mediated protein degradation plays a key role in the cell cycle regulation of eukaryotes.

These findings therefore shed new light on the evolutionary history of the eukaryotes.

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Origins of life: Chemical evolution in a tiny Gulf Stream

 Chemical reactions driven by the geological conditions on the early Earth might have led to the prebiotic evolution of self-replicating molecules. Scientists at Ludwig-Maximilians Universitaet (LMU) in Munich now report on a hydrothermal mechanism that could have promoted the process.

Life is a product of evolution by natural selection. That's the take-home lesson from Charles Darwin's book "The Origin of Species," published over 150 years ago. But how did the history of life on our planet begin? What kind of process could have led to the formation of the earliest forms of the biomolecules we now know, which subsequently gave rise to the first cell? Scientists believe that, on the (relatively) young Earth, environments must have existed, which were conducive to prebiotic, molecular evolution. A dedicated group of researchers is engaged in attempts to define the conditions under which the first tentative steps in the evolution of complex polymeric molecules from simple chemical precursors could have been feasible. "To get the whole process started, prebiotic chemistry must be embedded in a setting in which an appropriate combination of physical parameters causes a non-equilibrium state to prevail," explains LMU biophysicist Dieter Braun. Together with colleagues based at the Salk Institute in San Diego, he and his team have now taken a big step toward the definition of such a state. Their latest experiments have shown the circulation of warm water (provided by a microscopic version of the Gulf Stream) through pores in volcanic rock can stimulate the replication of RNA strands. The new findings appear in the journal Physical Review Letters.

As the carriers of hereditary information in all known lifeforms, RNA and DNA are at the heart of research into the origins of life. Both are linear molecules made up of four types of subunits called bases, and both can be replicated -- and therefore transmitted. The sequence of bases encodes the genetic information. However, the chemical properties of RNA strands differ subtly from those of DNA. While DNA strands pair to form the famous double helix, RNA molecules can fold into three-dimensional structures that are much more varied and functionally versatile. Indeed, specifically folded RNA molecules have been shown to catalyze chemical reactions both in the test-tube and in cells, just as proteins do. These RNAs therefore act like enzymes, and are referred to as 'ribozymes'. The ability to replicate and accelerate chemical transformations motivated the formulation of the 'RNA world' hypothesis. This idea postulates that, during early molecular evolution, RNA molecules served both as stores of information like DNA, and as chemical catalysts. The latter role is performed by proteins in today's organisms, where RNAs are synthesized by enzymes called RNA polymerases.

Ribozymes that can link short RNA strands together -- and some that can replicate short RNA templates -- have been created by mutation and Darwinian selection in the laboratory. One of these 'RNA polymerase' ribozymes was used in the new study.

Acquisition of the capacity for self-replication of RNA is viewed as the crucial process in prebiotic molecular evolution. In order to simulate conditions under which the process could have become established, Braun and his colleagues set up an experiment in which a 5-mm cylindrical chamber serves as the equivalent of a pore in a volcanic rock. On the early Earth, porous rocks would have been exposed to natural temperature gradients. Hot fluids percolating through rocks below the seafloor would have encountered cooler waters at the sea-bottom, for instance. This explains why submarine hydrothermal vents are the environmental setting for the origin of life most favored by many researchers. In tiny pores, temperature fluctuations can be very considerable, and give rise to heat transfer and convection currents. These conditions can be readily reproduced in the laboratory. In the new study, the LMU team verified that such gradients can greatly stimulate the replication of RNA sequences.

One major problem with ribozyme-driven scenario for replication of RNA is that the initial result of the process is a double-stranded RNA. To achieve cyclic replication, the strands must be separated ('melted'), and this requires higher temperatures, which are likely to unfold -- and inactivate -- the ribozyme. Braun and colleagues have now demonstrated how this can be avoided. "In our experiment, local heating of the reaction chamber creates a steep temperature gradient, which sets up a combination of convection, thermophoresis and Brownian motion," says Braun. Convection stirs the system, while thermophoresis transports molecules along the gradient in a size-dependent manner. The result is a microscopic version of an ocean current like the Gulf Stream. This is essential, as it transports short RNA molecules into warmer regions, while the larger, heat-sensitive ribozyme accumulates in the cooler regions, and is protected from melting. Indeed, the researchers were astonished to discover that the ribozyme molecules aggregated to form larger complexes, which further enhances their concentration in the colder region. In this way, the lifetimes of the labile ribozymes could be significantly extended, in spite of the relatively high temperatures. "That was a complete surprise," says Braun.

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New class of laser beam doesn't follow normal laws of refraction

 University of Central Florida researchers have developed a new type of laser beam that doesn't follow long-held principles about how light refracts and travels.

The findings, which were published recently in Nature Photonics, could have huge implications for optical communication and laser technologies.

"This new class of laser beams has unique properties that are not shared by common laser beams," says Ayman Abouraddy, a professor in UCF's College of Optics and Photonics and the study's principal investigator.

The beams, known as spacetime wave packets, follow different rules when they refract, that is when they pass through different materials. Normally, light slows down when it travels into a denser material.

"In contrast, spacetime wave packets can be arranged to behave in the usual manner, to not change speed at all, or even to anomalously speed up in denser materials," Abouraddy says. "As such, these pulses of light can arrive at different points in space at the same time."

"Think about how a spoon inside a water-filled glass looks broken at the point where the water and air meet," Abouraddy says. "The speed of light in air is different from the speed of light in water. And so, the light rays wind up bending after they cross the surface between air to water, and so apparently the spoon looks bent. This is a well-known phenomenon described by Snell's Law."

Although Snell's Law still applies, the underlying change in velocity of the pulses is no longer applicable for the new laser beams, Abouraddy says. These abilities are counter to Fermat's Principle that says light always travels such that it takes the shortest path, he says.

"What we find here, though, is no matter how different the materials are that light passes through, there always exists one of our spacetime wave packets that could cross the interface of the two materials without changing its velocity," Abouraddy says. "So, no matter what the properties of the medium are, it will go across the interface and continue as if it's not there."

For communication, this means the speed of a message traveling in these packets is no longer affected by traveling through different materials of different densities.

"If you think of a plane trying to communicate with two submarines at the same depth but one is far away and the other one's close by, the one that's farther away will incur a longer delay than the one that's close by," Abouraddy says. "We find that we can arrange for our pulses to propagate such that they arrive at the two submarines at the same time. In fact, now the person sending the pulse doesn't even need to know where the submarine is, as long as they are at the same depth. All those submarines will receive the pulse at the same time so you can blindly synchronize them without knowing where they are."

Abouraddy's research team created the spacetime wave packets by using a device known as a spatial light modulator to reorganize the energy of a pulse of light so that its properties in space and time are no longer separate. This allows them to control the "group velocity" of the pulse of light, which is roughly the speed at which the peak of the pulse travels.

Previous work has shown the team's ability to control the group velocity of the spacetime wave packets, including in optical materials. The current study built upon that work by finding they could also control the spacetime wave packets' speed through different media. This does not contradict special relativity in any way, because it applies to the propagation of the pulse peak rather than to the underlying oscillations of the light wave.

"This new field that we're developing is a new concept for light beams," Abouraddy says. "As a result, everything we look into using these beams reveals new behavior. All the behavior we know about light really takes tacitly an underlying presumption that its properties in space and time are separable. So, all we know in optics is based on that. It's a built-in assumption. It's taken to be the natural state of affairs. But now, breaking that underlying assumption, we're starting to see new behavior all over the place."

Co-authors of the study were Basanta Bhaduri, lead author and a former research scientist with UCF's College of Optics and Photonics, now with Bruker Nano Surfaces in California, and Murat Yessenov, a doctoral candidate in the college.

Bhaduri became interested in Abouraddy's research after reading about it in journals, such as Optics Express and Nature Photonics, and joined the professor's research team in 2018. For the study, he helped develop the concept and designed the experiments, as well as carried out measurements and analyzed data.

He says the study results are important in many ways, including the new research avenues it opens.

"Space-time refraction defies our expectations derived from Fermat's principle and offers new opportunities for molding the flow of light and other wave phenomena," Bhaduri says.

Yessenov's roles included data analysis, derivations and simulations. He says he became interested in the work by wanting to explore more about entanglement, which in quantum systems is when two well-separated objects still have a relation to each other.

"We believe that spacetime wave packets have more to offer and many more interesting effects can be unveiled using them," Yessenov says.

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Hubble uses Earth as proxy for identifying oxygen on potentially habitable exoplanets

Taking advantage of a total lunar eclipse, astronomers using NASA's Hubble Space Telescope have detected Earth's own brand of sunscreen -- ozone -- in our atmosphere. This method simulates how astronomers and astrobiology researchers will search for evidence of life beyond Earth by observing potential "biosignatures" on exoplanets (planets around other stars).

Hubble did not look at Earth directly. Instead, the astronomers used the Moon as a mirror to reflect sunlight, which had passed through Earth's atmosphere, and then reflected back towards Hubble. Using a space telescope for eclipse observations reproduces the conditions under which future telescopes would measure atmospheres of transiting exoplanets. These atmospheres may contain chemicals of interest to astrobiology, the study of and search for life.

Though numerous ground-based observations of this kind have been done previously, this is the first time a total lunar eclipse was captured at ultraviolet wavelengths and from a space telescope. Hubble detected the strong spectral fingerprint of ozone, which absorbs some of the sunlight. Ozone is important to life because it is the source of the protective shield in Earth's atmosphere.

On Earth, photosynthesis over billions of years is responsible for our planet's high oxygen levels and thick ozone layer. That's one reason why scientists think ozone or oxygen could be a sign of life on another planet, and refer to them as biosignatures.

"Finding ozone is significant because it is a photochemical byproduct of molecular oxygen, which is itself a byproduct of life," explained Allison Youngblood of the Laboratory for Atmospheric and Space Physics in Boulder, Colorado, lead researcher of Hubble's observations.

Although ozone in Earth's atmosphere had been detected in previous ground-based observations during lunar eclipses, Hubble's study represents the strongest detection of the molecule to date because ozone -- as measured from space with no interference from other chemicals in the Earth's atmosphere -- absorbs ultraviolet light so strongly.

Hubble recorded ozone absorbing some of the Sun's ultraviolet radiation that passed through the edge of Earth's atmosphere during a lunar eclipse that occurred on January 20 to 21, 2019. Several other ground-based telescopes also made spectroscopic observations at other wavelengths during the eclipse, searching for more of Earth's atmospheric ingredients, such as oxygen and methane.

"One of NASA's major goals is to identify planets that could support life," Youngblood said. "But how would we know a habitable or an uninhabited planet if we saw one? What would they look like with the techniques that astronomers have at their disposal for characterizing the atmospheres of exoplanets? That's why it's important to develop models of Earth's spectrum as a template for categorizing atmospheres on extrasolar planets."

Her paper is available online in The Astronomical Journal.

Sniffing Out Planetary Atmospheres

The atmospheres of some extrasolar planets can be probed if the alien world passes across the face of its parent star, an event called a transit. During a transit, starlight filters through the backlit exoplanet's atmosphere. (If viewed close up, the planet's silhouette would look like it had a thin, glowing "halo" around it caused by the illuminated atmosphere, just as Earth does when seen from space.)

Chemicals in the atmosphere leave their telltale signature by filtering out certain colors of starlight. Astronomers using Hubble pioneered this technique for probing exoplanets. This is particularly remarkable because extrasolar planets had not yet been discovered when Hubble was launched in 1990 and the space observatory was not initially designed for such experiments.

So far, astronomers have used Hubble to observe the atmospheres of gas giant planets and super-Earths (planets several times Earth's mass) that transit their stars. But terrestrial planets about the size of Earth are much smaller objects and their atmospheres are thinner, like the skin on an apple. Therefore, teasing out these signatures from Earth-sized exoplanets will be much harder.

That's why researchers will need space telescopes much larger than Hubble to collect the feeble starlight passing through these small planets' atmospheres during a transit. These telescopes will need to observe planets for a longer period, many dozens of hours, to build up a strong signal.

To prepare for these bigger telescopes, astronomers decided to conduct experiments on a much closer and only known inhabited terrestrial planet: Earth. Our planet's perfect alignment with the Sun and Moon during a total lunar eclipse mimics the geometry of a terrestrial planet transiting its star.

But the observations were also challenging because the Moon is very bright, and its surface is not a perfect reflector because it is mottled with bright and dark areas. The Moon is also so close to Earth that Hubble had to try and keep a steady eye on one select region, despite the Moon's motion relative to the space observatory. So, Youngblood's team had to account for the Moon's drift in their analysis.

Where There's Ozone, There's Life?

Finding ozone in the skies of a terrestrial extrasolar planet does not guarantee that life exists on the surface. "You would need other spectral signatures in addition to ozone to conclude that there was life on the planet, and these signatures cannot necessarily be seen in ultraviolet light," Youngblood said.

On Earth, ozone is formed naturally when oxygen in the Earth's atmosphere is exposed to strong concentrations of ultraviolet light. Ozone forms a blanket around Earth, protecting it from harsh ultraviolet rays.

"Photosynthesis might be the most productive metabolism that can evolve on any planet, because it is fueled by energy from starlight and uses cosmically abundant elements like water and carbon dioxide," said Giada Arney of NASA's Goddard Space Flight Center in Greenbelt, Maryland, a co-author of the science paper. "These necessary ingredients should be common on habitable planets."

Seasonal variability in the ozone signature also could indicate seasonal biological production of oxygen, just as it does with the growth seasons of plants on Earth.

But ozone can also be produced without the presence of life when nitrogen and oxygen are exposed to sunlight. To increase confidence that a given biosignature is truly produced by life, astronomers must search for combinations of biosignatures. A multiwavelength campaign is needed because each of the many biosignatures are more easily detected at wavelengths specific to those signatures.

"Astronomers will also have to take the developmental stage of the planet into account when looking at younger stars with young planets. If you wanted to detect oxygen or ozone from a planet similar to the early Earth, when there was less oxygen in our atmosphere, the spectral features in optical and infrared light aren't strong enough," Arney explained. "We think Earth had low concentrations of ozone before the mid-Proterozoic geological period (between roughly 2.0 billion to 0.7 billion years ago) when photosynthesis contributed to the build up of oxygen and ozone in the atmosphere to the levels we see today. But because the ultraviolet-light signature of ozone features is very strong, you would have a hope of detecting small amounts of ozone. The ultraviolet may therefore be the best wavelength for detecting photosynthetic life on low-oxygen exoplanets."

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This fruit attracts birds with an unusual way of making itself metallic blue

There's a reason why blue fruits are so rare: the pigment compounds that make fruits blue are relatively uncommon in nature. But the metallic blue fruits of Viburnum tinus, a popular landscaping plant in Europe, get their color a different way. Instead of relying solely on pigments, the fruits use structural color to reflect blue light, something that's rarely seen in plants. Researchers reporting August 6 in the journal Current Biology show that the fruits use nanostructures made of lipids in their cell walls, a previously unknown mechanism of structural color, to get their striking blue -- which may also double as a signal to birds that the fruits are full of nutritious fats.

"Structural color is very common in animals, especially birds, beetles, and butterflies, but only a handful of plant species have ever been found to have structural color in their fruits," says co-first author Miranda Sinnott-Armstrong, a postdoctoral researcher at the University of Colorado-Boulder. "This means that V. tinus, in addition to showing a completely novel mechanism of structural color, is also one of the few known structurally colored fruits."

Senior author Silvia Vignolini, a physical chemist at the University of Cambridge, has been interested in the plants for nearly 10 years. "I actually found this Viburnum in a garden in Italy and observed that they looked weird, so we measured them at the time but didn't have conclusive results. It was kind of always on the back of my mind," she says. As her team grew, they become more interested in V. tinus and eventually had the capability to examine the structure of the fruits using electron microscopy. "Before we got the images, we were just seeing all these blobs," she says. "When we found out that those blobs were lipids, we got very excited."

While most plants have cell walls made of cellulose, used to make cotton and paper, V. tinus fruit cells have much thicker walls with thousands of globular lipids arranged in layers that reflect blue light. The structure formed by this so-called lipid multilayer allows the fruits to create their vibrant blue color while containing no blue pigment. "This is very strange because globular lipids like these are not usually found in this arrangement in the cell wall, as they are normally stored inside the cell and used for transport," says co-first author Rox Middleton, a physicist who studied the optical response of the fruits during her PhD and is now a postdoctoral researcher at the University of Bristol. "We also believe that this lipid may contribute to the fruit's nutrition. That means that the fruit can demonstrate how nutritious it is by being a beautiful, shiny blue."

This extra nutrition would be important for V. tinus's main consumers: birds that disperse the plant's seeds. Although the researchers can't say for sure whether the lipids are used as fat by the birds that consume them, there is reason to believe they might be. If so, the researchers suggest that the metallic blue color made by the lipid multilayer could indicate to the birds that if they see this striking blue, the fruit in question will have enough nutrients to make it a worthwhile meal. "While birds have been shown to be attracted to blue fruits," says Vignolini, "other blue fruits that we have studied essentially don't have any nutritional value."

Going forward, the researchers want to see how widespread blue structural color is in fruits to understand its ecological significance. They had never seen this type of lipid multilayer in a biomaterial before, but since their discovery, they've begun to take notice of other species. "We actually realize now that there are some older electron microscopy pictures from other plants where you can see the blobs. The researchers didn't know that they were lipids at the time, or that lipids could even form this type of structure, but our research suggests that they very well could be, meaning this structure may not be limited to Viburnum," Vignolini says.

Additionally, learning how V. tinus can use such a unique mechanism to make color may have implications for how we color our own foods. "There are lots of problems connected to food coloration," says Vignolini. She adds that once this mechanism is better understood, it could potentially be used to create a healthier, more sustainable food colorant.

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Non-invasive nerve stimulation boosts learning of foreign language sounds

New research by neuroscientists at the University of Pittsburgh and University of California San Francisco (UCSF) revealed that a simple, earbud-like device developed at UCSF that imperceptibly stimulates a key nerve leading to the brain could significantly improve the wearer's ability to learn the sounds of a new language. This device may have wide-ranging applications for boosting other kinds of learning as well.

Mandarin Chinese is considered one of the hardest languages for native English speakers to learn, in part because the language -- like many others around the world -- uses distinctive changes in pitch, called "tones," to change the meaning of words that otherwise sound the same. In the new study, published today in npj Science of Learning (a Nature partner journal), researchers significantly improved the ability of native English speakers to distinguish between Mandarin tones by using precisely timed, non-invasive stimulation of the vagus nerve -- the longest of the 12 cranial nerves that connect the brain to the rest of the body. What's more, vagus nerve stimulation allowed research participants to pick up some Mandarin tones twice as quickly.

"Showing that non-invasive peripheral nerve stimulation can make language learning easier potentially opens the door to improving cognitive performance across a wide range of domains," said lead author Fernando Llanos, Ph.D., a postdoctoral researcher in Pitt's Sound Brain Lab.

"This is one of the first demonstrations that non-invasive vagus nerve stimulation can enhance a complex cognitive skill like language learning in healthy people," said Matthew Leonard, Ph.D., an assistant professor, Department of Neurological Surgery, UCSF Weill Institute for Neurosciences, whose team developed the nerve stimulation device. Leonard is a senior author of the new study, alongside Bharath Chandrasekaran, Ph.D., professor and vice chair of research, Department of Communication Science and Disorders, Pitt School of Health and Rehabilitation Sciences, and director of the Sound Brain Lab.

Researchers used a non-invasive technique called transcutaneous vagus nerve stimulation (tVNS), in which a small stimulator is placed in the outer ear and can activate the vagus nerve using unnoticeable electrical pulses to stimulate one of the nerve's nearby branches.

For their study, the researchers recruited 36 native English-speaking adults and trained them to identify the four tones of Mandarin Chinese in examples of natural speech, using a set of tasks developed in the Sound Brain Lab to study the neurobiology of language learning.

Participants who received imperceptible tVNS paired with two Mandarin tones that are typically easier for English speakers to tell apart showed quick improvements in learning to distinguish these tones. By the end of the training, those participants were 13% better on average at classifying tones and reached peak performance twice as quickly as control participants who wore the tVNS device but never received stimulation.

"There's a general feeling that people can't learn the sound patterns of a new language in adulthood, but our work historically has shown that's not true for everyone," Chandrasekaran said. "In this study, we are seeing that tVNS reduces those individual differences more than any other intervention I've seen."

"This approach may be leveling the playing field of natural variability in language learning ability," added Leonard. "In general, people tend to get discouraged by how hard language learning can be, but if you could give someone 13% to 15% better results after their first session, maybe they'd be more likely to want to continue."

The researchers now are testing whether longer training sessions with tVNS can impact participants' ability to learn to discriminate two tones that are harder for English speakers to differentiate, which was not significantly improved in the current study.

Stimulation of the vagus nerve has been used to treat epilepsy for decades and has recently been linked to benefits for a wide range of issues ranging from depression to inflammatory disease, though exactly how these benefits are conferred remains unclear. But most of these findings have used invasive forms of stimulation involving an impulse generator implanted in the chest. By contrast, the ability to evoke significant boosts to learning using simple, non-invasive vagus nerve stimulation could lead to significantly cheaper and safer clinical and commercial applications.

The researchers suspect tVNS boosts learning by broadly enhancing neurotransmitter signaling across wide swaths of the brain to temporarily boost attention to the auditory stimulus being presented and promote long-term learning, though more research is needed to verify this mechanism.

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Placebos prove powerful even when people know they're taking one

How much of a treatment is mind over matter? It is well documented that people often feel better after taking a treatment without active ingredients simply because they believe it's real -- known as the placebo effect.

A team of researchers from Michigan State University, University of Michigan and Dartmouth College is the first to demonstrate that placebos reduce brain markers of emotional distress even when people know they are taking one.

Now, evidence shows that even if people are aware that their treatment is not "real" -- known as nondeceptive placebos -- believing that it can heal can lead to changes in how the brain reacts to emotional information.

"Just think: What if someone took a side-effect free sugar pill twice a day after going through a short convincing video on the power of placebos and experienced reduced stress as a result?," said Darwin Guevarra, MSU postdoctoral fellow and the study's lead author. "These results raise that possibility."

The new findings, published in the most recent edition of the journal Nature Communications, tested how effective nondeceptive placebos -- or, when a person knows they are receiving a placebo -- are for reducing emotional brain activity.

"Placebos are all about 'mind over matter," said Jason Moser, co-author of the study and professor of psychology at MSU. "Nondeceptive placebos were born so that you could possibly use them in routine practice. So rather than prescribing a host of medications to help a patient, you could give them a placebo, tell them it can help them and chances are -- if they believe it can, then it will."

To test nondeceptive placebos, the researchers showed two separate groups of people a series of emotional images across two experiments. The nondeceptive placebo group members read about placebo effects and were asked to inhale a saline solution nasal spray. They were told that the nasal spray was a placebo that contained no active ingredients but would help reduce their negative feelings if they believed it would. The comparison control group members also inhaled the same saline solution spray, but were told that the spray improved the clarity of the physiological readings the researchers were recording.

The first experiment found that the nondeceptive placebos reduced participants' self-reported emotional distress. Importantly, the second study showed that nondeceptive placebos reduced electrical brain activity reflecting how much distress someone feels to emotional events, and the reduction in emotional brain activity occurred within just a couple of seconds.

"These findings provide initial support that nondeceptive placebos are not merely a product of response bias -- telling the experimenter what they want to hear -- but represent genuine psychobiological effects," said Ethan Kross, co-author of the study and a professor of psychology and management at the University of Michigan.

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