Competition for mates leads to a deeper voice than expected based on size.
An analysis of the songs of most of the world’s passerine birds reveals that the frequency at which birds sing mostly depends on body size, but is also influenced by sexual selection. The new study from researchers of the Max Planck Institute for Ornithology and colleagues suggests that habitat characteristics do not affect song frequency, thereby refuting a long-standing theory.
Many animals use acoustic signals for communication. These signals have evolved to maximize the effectiveness of the transmission and reception of the sounds, because this helps finding a mate or avoiding predation. One of the fundamental characteristics of acoustic signals is the frequency of the sound. In forested habitats, acoustic signals become attenuated because of sound absorption and scattering from foliage, which is particularly problematic for high-frequency sounds. Hence, a theory from the 1970s predicts that animals living in habitats with dense vegetation emit lower-frequency sounds compared to those living in open areas.
A team of researchers led by Bart Kempenaers from the Max Planck Institute for Ornithology in Seewiesen and Tomáš Albrecht from the Charles University in Praha and the Czech Academy of Sciences analysed the variation in song frequency of more than 5.000 passerine bird species, encompassing 85% of all passerines and half of all avian taxa. PhD student Peter Mikula collected song recordings primarily from xeno-canto, a citizen science repository of bird vocalizations, and from the Macaulay Library of the Cornell Lab of Ornithology.
Relationship between song frequency and body size
Contrary to the theory, the study reveals that the peak frequency of passerine song does not depend on habitat type. If anything, the data suggest that species living in densely vegetated habitats sing at lower frequencies, which is the opposite of what was predicted. As expected from basic physical principles, the researchers found a strong relationship between song frequency and body size and an effect of shared ancestry. “Both limit the range of sound frequencies an animal can produce”, says first author Peter Mikula. Heavier species sing at lower frequencies simply due to the larger vibratory structures of the vocal apparatus.
The study further reveals that species in which males are larger than females produce songs with lower frequencies than expected from their size. “This supports the hypothesis that the frequency of acoustic signals is affected by competition for access to mates”, says Bart Kempenaers. Song frequency may act as an indicator of an individual’s size and therefore of its dominance or fighting abilities. Thus, song frequency could influence reproductive success through competition with other males or even because it influences male attractiveness to females.
“Our results suggest that the global variation in passerine song frequency is mostly driven by natural and sexual selection causing evolutionary shifts in body size rather than by habitat-related selection on sound propagation”, summarizes Tomáš Albrecht.
Light-controlled genes could reveal how gut bacteria impact health.
Baylor College of Medicine researcher Meng Wang had already shown that bacteria that make a metabolite called colanic acid (CA) could extend the lifespan of worms in her lab by as much as 50%, but her collaboration with Rice University synthetic biologist Jeffrey Tabor is providing tools to answer the bigger question of how the metabolite imparts longer life.
In a study published in eLife, Wang, Tabor and colleagues showed they could use different colors of light to turn gut bacteria genes on and off while the bacteria were in the intestines of worms. The work was made possible by an optogenetic control system Tabor has been developing for more than a decade.
“Meng’s group discovered that the CA compound could extend lifespan but they couldn’t say for sure whether this was a dietary ingredient that was being digested in the stomach or a metabolite that was being produced by bacteria in the intestines,” said Tabor, an associate professor of bioengineering and of biosciences at Rice. “We were able to restrict production of CA to the gut and show that it had a beneficial effect on cells in the intestines.”
For the experiments, Tabor’s lab engineered strains of E. coli to make CA when exposed to green, but not red, light. To make sure the bacteria worked properly, the team added genes to make different colors of fluorescent proteins that would show up brightly under a microscope. One color was always present, to make it easy to see where the bacteria were inside the worms, and a second color was made only when the bacteria were producing CA.
In collaboration with the Wang lab, Tabor’s lab kept the bacteria under a red light and fed them to worms, a species called Caenorhabditis elegans (C. elegans) that’s commonly used in life sciences. Researchers tracked the bacteria’s progress through the digestive tract and switched on the green light when they made it to the intestines.
In the cells of C. elegans and other higher order life, from humans to yeast, specialized organelles called mitochondria supply most of the energy. Thousands of mitochondria work around the clock in each cell and maintain a dynamic balance between fission and fusion, but they become less efficient over time. As people and other organisms age, the dysfunction of mitochondria leads to functional decline in their cells.
In prior experiments with C. elegans, Wang and colleagues showed that CA can regulate the balance between mitochondrial fission and fusion in both intestinal and muscle cells to promote longevity. The worms typically live about three weeks, but Wang’s lab has shown that CA can extend their lives to 4.5 weeks — 50% longer than usual.
Tabor said this raises a host of questions. For instance, if CA is produced in the gut, do intestinal cells benefit first? Is the beneficial effect of CA related to its level? And most important, do the mitochondrial benefits spread throughout the body from the intestines?
In the eLife study, the researchers found that CA production in the gut directly improved mitochondrial function in intestinal cells in a short time. They did not find evidence of such direct, short-term mitochondrial benefits in the worms’ muscle cells. Thus, the longevity-promoting effect of CA starts from the gut and then spreads into other tissues over time.
“With our technology, we can use light to turn on CA production and watch the effect travel through the worm,” Tabor said.
He said the precision of the optogenetic technology could allow researchers to ask fundamental questions about gut metabolism.
“If you can control the timing and location of metabolite production with precision, you can think about experimental designs that show cause and effect,” he said.
Showing that gut bacteria directly impact health or disease would be a major achievement.
“We know gut bacteria affect many processes in our bodies,” Tabor said. “They’ve been linked to obesity, diabetes, anxiety, cancers, autoimmune diseases, heart disease and kidney disease. There’s been an explosion of studies measuring what bacteria you have when you have this illness or that illness, and it’s showing all kinds of correlations.”
But there is a big difference between showing correlation and causality, Tabor said.
“The goal, the thing you really want, is gut bacteria you can eat that will improve health or treat disease,” he said.
But it’s difficult for researchers to prove that molecules produced by gut bacteria cause disease or health. That’s partly because the gut is difficult to access experimentally, and it’s especially difficult to design experiments that show what is happening in specific locations inside the gut.
“The gut is a hard place to access, especially in large mammals,” Tabor said. “Our intestines are 28 feet long, and they’re very heterogeneous. The pH changes throughout and the bacteria change quite dramatically along the way. So do the tissues and what they’re doing, like the molecules they secrete.
“To answer questions about how gut bacteria influence our health, you need to be able to turn on genes in specific places and at particular times, like when an animal is young or when an animal wakes up in the morning,” he said. “You need that level of control to study pathways on their own turf, where they happen and how they happen.”
Because it uses light to trigger genes, optogenetics offers that level of control, Tabor said.
“To this point, light is really the only signal that has enough precision to turn on bacterial genes in the small versus the large intestine, for example, or during the day but not at night,” he said.
Tabor said he and Wang have discussed many ways they might use optogenetics to study aging.
“She’s found two dozen bacterial genes that can extend lifespan in C. elegans, and we don’t know how most of them work,” Tabor said. “The colanic acid genes are really intriguing, but there are many more that we’d like to turn on with light in the worm to figure out how they work. We can use the exact technique that we published in this paper to explore those new genes as well. And other people who are studying the microbiome can use it too. It’s a powerful tool for investigating how bacteria are benefiting our health.”
Study co-authors include Lucas Hartsough, Matthew Kotlajich, John Tyler Lazar, Elena Musteata and Lauren Gambill of Rice, and Mooncheol Park, Bing Han and Chih-Chun Lin of Baylor. The research was supported by the National Institutes of Health, the National Aeronautics and Space Administration, the John S. Dunn Foundation and the Welch Foundation.
Every year, people all over the world try to make the biggest artificial Christmas tree. Like the Gubbio Christmas Tree, formed by thousands of lights on the slopes of Mount Ingino. Or the illumination of the 372-metre high transmission mast at Lopik in The Netherlands. Maura Willems, a student of Applied Physics at Delft University of Technology (TU Delft), decided to do the opposite. She created what is probably the world’s smallest Christmas tree.
For her graduation, Willems works with a scanning tunneling microscope: a complex device that is capable of scanning individual atoms and even changing their position. She uses this microscope to build small structures, literally atom by atom, in order to study their quantum mechanical properties.
But sometimes you can also use technology for something more fun. Willems came up with the idea of making a Christmas tree by removing 51 atoms from a perfect crystal lattice. The tree is exactly 4 nanometers tall, or 4 millionths of a millimeter. But that is, admittedly, without counting the tree-topper.
Waray Dwarf Burrowing Snake occupies its own branch on snake tree of life.
To be fair, the newly described Waray Dwarf Burrowing Snake (Levitonius mirus) is pretty great at hiding.
In its native habitat, Samar and Leyte islands in the Philippines, the snake spends most of its time burrowing underground, usually surfacing only after heavy rains in much the same way earthworms tend to wash up on suburban sidewalks after a downpour.
So, it may not be shocking that when examples of the Waray Dwarf Burrowing Snake were collected in 2006 and 2007, they were misidentified in the field — nobody had seen them before. The specimens spent years preserved in the collections of the University of Kansas Biodiversity Institute and Natural History Museum, overlooked by researchers who were unaware they possessed an entirely new genus of snake, even after further examples were found in 2014.
But that changed once Jeff Weinell, a KU graduate research assistant at the Biodiversity Institute, took a closer look at the specimens’ genetics using molecular analysis, then sent them to collaborators at the University of Florida for CT scanning. Now, he’s the lead author on a paper describing the snake as both a new genus, and a new species, in the peer-reviewed journal Copeia.
“I was initially interested in studying the group of snakes that I thought it belonged to — or that other people thought it belonged to,” Weinell said. “This is when I first started my Ph.D. at KU. I was interested in collecting data on a lot of different snakes and finding out what I actually wanted to research. I knew this other group of small, burrowing snakes called Pseudorabdion — there are quite a few species in the Philippines — and I was interested in understanding the relationships among those snakes. So, I made a list of all the specimens we had in the museum of that group, and I started sequencing DNA for the tissues that were available.”
As soon as Weinell got the molecular data back, he realized the sample from the subterranean snake didn’t fall within Pseudorabdion. But pinpointing where the snake should be classified wasn’t a simple task: The Philippine archipelago is an exceptionally biodiverse region that includes at least 112 species of land snakes from 41 genera and 12 families.
“It was supposed to be closely related, but it was actually related to this entirely different family of snakes,” he said. “That led me to look at it in more detail, and I realized that there were actually some features that were quite different from what it was initially identified as.”
Working with Rafe Brown, professor of ecology & evolutionary biology and curator-in-charge of the KU Biodiversity Institute and Natural History Museum, Weinell took a closer look at the snake’s morphology, paying special attention to the scales on the body, which can be used to differentiate species.
He then sent one of the specimens to the University of Florida for CT scanning to get a more precise look at the internal anatomy of the mysterious Philippine snake. The CT images turned out to be surprising.
“The snake has among the fewest number of vertebrae of any snake species in the world, which is likely the result of miniaturization and an adaptation for spending most of its life underground,” Weinell said.
Finally, the KU graduate research assistant and his colleagues were able to determine the Waray Dwarf Burrowing Snake mirus was a new “miniaturized genus” and species of snake. Now, for the first time, Weinell has had the chance to bestow the snake with its scientific name, Levitonius mirus.
“It’s actually named for Alan Leviton, who is a researcher at the California Academy of Sciences, and he had spent decades basically studying snakes in the Philippines in the ’60s, ’70s, ’80s and then all the way up to now,” Weinell said. “So, that’s sort of an honorific genus name for him. Then, ‘mirus’ is Latin for unexpected. That’s referencing the unexpected nature of this discovery — getting the DNA sequences back and then wondering what was going on.”
In addition to Brown, Weinell’s co-authors on the new paper are Daniel Paluh of the University of Florida and Cameron Siler of the University of Oklahoma. Brown said the description of Levitonius mirus highlights the value of preserving collections of biodiversity in research institutions and universities.
“In this case, the trained ‘expert field biologists’ misidentified specimens — and we did so repeatedly, over years — failing to recognize the significance of our finds, which were preserved and assumed to be somewhat unremarkable, nondescript juveniles of common snakes,” Brown said. “This happens a lot in the real world of biodiversity discovery. It was only much later, when the next generation of scientists came along and had the time and access to accumulated numbers of specimens, and when the right people, like Jeff, who asked the right questions and who had the right tools and expertise, like Dan, came along and took a fresh look, that we were able to identify this snake correctly. It’s a good thing we have biodiversity repositories and take our specimen-care oaths seriously.”
According to Marites Bonachita-Sanguila, a biologist at the Biodiversity Informatics and Research Center at Father Saturnino Urios University, located in the southern Philippines, the snake discovery “tells us that there is still so much more to learn about reptile biodiversity of the southern Philippines by focusing intently on species-preferred microhabitats.”
“The pioneering Philippine herpetological work of Walter Brown and Angel Alcala from the 1960s to the 1990s taught biologists the important lesson of focusing on species’ very specific microhabitat preferences,” Bonachita-Sanguila said. “Even so, biologists have really missed many important species occurrences, such as this, because …. well, simply because we did not know basic clues about where to find them. In the case of this discovery, the information that biologists lacked was that we should dig for them when we survey forests. So simple. How did we miss that? All this time, we were literally walking on top of them as we surveyed the forests of Samar and Leyte. Next time, bring a shovel.”
She added that habitat loss as a result of human-mediated land use (such as conversion of forested habitats for agriculture to produce food for people) is a prevailing issue in Philippine society today.
“This new information, and what we will learn more in future studies of this remarkable little creature, would inform planning for conservation action, in the strong need for initiatives to conserve Philippine endemic species — even ones we seldom get to see,” Bonachita-Sanguila said. “We need effective land-use management strategies, not only for the conservation of celebrated Philippine species like eagles and tarsiers, but for lesser-known, inconspicuous species and their very specific habitats — in this case, forest-floor soil, because it’s the only home they have.”
A catastrophic tsunami occurred sometimes between 7,910 and 7,290 BCE with an extreme 16 m (52.5 feet) wave height and 1.5-3.5 km (0.93-2.2 mile) run-up on the Carmel coast of Israel, according to new research published in the journal PLoS ONE.
“Tsunami events in antiquity had a profound influence on coastal societies,” said lead author Dr. Gilad Shtienberg from the Department of Anthropology in the Scripps Center for Marine Archaeology at the University of California, San Diego, and colleagues.
“6,000 years of historical records and geological data show that tsunamis are a common phenomenon affecting the eastern Mediterranean coastline, occurring at a rate of around 8 events per century in the Aegean region over the past 2,000 years and approximately 10 per century over the past 3,000 years in the Levant basin.”
“Most of these events are small and have only local impacts.”
In the study, the researchers found a large paleo-tsunami deposit (between 9,910 to 9,290 years ago) at the archaeological site of Tel Dor in northwest Israel.
“Tel Dor, located along the Carmel coast of northwest Israel, is a maritime city-mound that has been occupied from the Middle Bronze II period (2000 to 1550 BCE) throughout the Roman period (3rd century CE) while Byzantine and Crusader remains are also found on the tel,” they said.
“The local environment of Dor is characterized by a series of unique embayments/pocket beaches that stand out from the linear morphology of the southeastern Mediterranean littoral shore face.”
To conduct their analysis, the scientists used photogrammetric remote sensing techniques to create a digital model of the Tel Dor site, combined with underwater excavation and terrestrial borehole drilling to a depth of 9 m (29.5 feet).
In their samples, they found an abrupt layer of seashells and sand, dated to between 9,910 and 9,290 years ago, in the middle wetland layers deposited 15,000 to 7,800 years ago.
They estimate that the ancient tsunami had a run-up of at least 16 m and traveled between 3.5 to 1.5 km inland from the paleo-coastline.
The near absence of Pre-Pottery Neolithic A-B archaeological sites (11,700-9,800 years ago) suggest these sites were removed by the tsunami, whereas younger, late Pre-Pottery Neolithic B-C (9,250-8,350 years ago) and later Pottery-Neolithic sites (8,250-7,800 years ago) indicate resettlement following the event.
“We can’t know for sure why people weren’t living there, in a place otherwise abundant with evidence of early human habitation and the beginnings of village life in the Holy Land,” said Professor Thomas Levy, a researcher in the Department of Anthropology and the Levant and Cyber-Archaeology Laboratory in the Scripps Center for Marine Archaeology at the University of California, San Diego.
“Was the environment too altered to support life? Was the tsunami part of their cultural knowledge — did they tell stories of this destructive event and stay away? We can only imagine.”
“Our project focuses on reconstructing ancient climate and environmental change over the past 12,000 years along the Israeli coast; and we never dreamed of finding evidence of a prehistoric tsunami in Israel,” Dr. Shtienberg said.
“Scholars know that at the beginning of the Neolithic, around 10,000 years ago, the seashore was 4 km (2.5 miles) from where it is today.”
“When we cut the cores open in San Diego and started seeing a marine shell layer embedded in the dry Neolithic landscape, we knew we hit the jackpot.”
Reference: G. Shtienberg et al. 2020. A Neolithic mega-tsunami event in the eastern Mediterranean: Prehistoric settlement vulnerability along the Carmel coast, Israel. PLoS ONE 15 (12): e0243619; doi: 10.1371/journal.pone.0243619
Newly described chemical reaction could have assembled DNA building blocks before life forms and their enzymes existed.
Chemists at Scripps Research have made a discovery that supports a surprising new view of how life originated on our planet.
In a study published in the chemistry journal Angewandte Chemie, they demonstrated that a simple compound called diamidophosphate (DAP), which was plausibly present on Earth before life arose, could have chemically knitted together tiny DNA building blocks called deoxynucleosides into strands of primordial DNA.
The finding is the latest in a series of discoveries, over the past several years, pointing to the possibility that DNA and its close chemical cousin RNA arose together as products of similar chemical reactions, and that the first self-replicating molecules—the first life forms on Earth—were mixes of the two.
The discovery may also lead to new practical applications in chemistry and biology, but its main significance is that it addresses the age-old question of how life on Earth first arose. In particular, it paves the way for more extensive studies of how self-replicating DNA-RNA mixes could have evolved and spread on the primordial Earth and ultimately seeded the more mature biology of modern organisms.
“This finding is an important step toward the development of a detailed chemical model of how the first life forms originated on Earth,” says study senior author Ramanarayanan Krishnamurthy, PhD, associate professor of chemistry at Scripps Research.
The finding also nudges the field of origin-of-life chemistry away from the hypothesis that has dominated it in recent decades: The “RNA World” hypothesis posits that the first replicators were RNA-based, and that DNA arose only later as a product of RNA life forms.
Is RNA too sticky?
Krishnamurthy and others have doubted the RNA World hypothesis in part because RNA molecules may simply have been too “sticky” to serve as the first self-replicators.
A strand of RNA can attract other individual RNA building blocks, which stick to it to form a sort of mirror-image strand—each building block in the new strand binding to its complementary building block on the original, “template” strand. If the new strand can detach from the template strand, and, by the same process, start templating other new strands, then it has achieved the feat of self-replication that underlies life.
But while RNA strands may be good at templating complementary strands, they are not so good at separating from these strands. Modern organisms make enzymes that can force twinned strands of RNA—or DNA—to go their separate ways, thus enabling replication, but it is unclear how this could have been done in a world where enzymes didn’t yet exist.
A chimeric workaround
Krishnamurthy and colleagues have shown in recent studies that “chimeric” molecular strands that are part DNA and part RNA may have been able to get around this problem, because they can template complementary strands in a less-sticky way that permits them to separate relatively easily.
The chemists also have shown in widely cited papers in the past few years that the simple ribonucleoside and deoxynucleoside building blocks, of RNA and DNA respectively, could have arisen under very similar chemical conditions on the early Earth.
Moreover, in 2017 they reported that the organic compound DAP could have played the crucial role of modifying ribonucleosides and stringing them together into the first RNA strands. The new study shows that DAP under similar conditions could have done the same for DNA.
“We found, to our surprise, that using DAP to react with deoxynucleosides works better when the deoxynucleosides are not all the same but are instead mixes of different DNA ‘letters’ such as A and T, or G and C, like real DNA,” says first author Eddy Jiménez, PhD, a postdoctoral research associate in the Krishnamurthy lab.
“Now that we understand better how a primordial chemistry could have made the first RNAs and DNAs, we can start using it on mixes of ribonucleoside and deoxynucleoside building blocks to see what chimeric molecules are formed—and whether they can self-replicate and evolve,” Krishnamurthy says.
He notes that the work may also have broad practical applications. The artificial synthesis of DNA and RNA—for example in the “PCR” technique that underlies COVID-19 tests—amounts to a vast global business, but depends on enzymes that are relatively fragile and thus have many limitations. Robust, enzyme-free chemical methods for making DNA and RNA may end up being more attractive in many contexts, Krishnamurthy says.
As we approach that magical time of the year again when Santa Claus will set off on his merry way, bringing gifts to children around the world, that familiar question arises:
How on Earth does he visit all those different places in a single night?
In many sceptics’ minds Santa seems to defy the laws of physics. But for quantum physicists there is no issue. The most modern theory, according to Professor John Goold and Dr Mark Mitchison (of the TCD QuSys research group in Trinity), is that Santa Claus is in fact exploiting quantum mechanics to deliver the gifts.
In a nutshell, quantum mechanics allows objects (and Santa, Rudolph and co.) to be in many places simultaneously. That is the key ingredient, which allows for his extraordinarily efficient delivery on Christmas Eve.
Quantum physics describes the basic building blocks of the stuff we can see around us. It explains almost everything we understand about the world: how the sun shines, why metal looks and feels different from plastic or wood, and very many other things. But quantum physics also makes some bizarre predictions, starting with the fact that objects can be in “superposition”, meaning that they exist in many different places at the same time!
Professor Goold, Assistant Professor and Royal Society URF in Physics at Trinity,, said:
“Experiments show that these weird states describe tiny things – like atoms – but also much larger things too. In fact, an important part of our job as physicists is trying to put bigger and bigger objects into superpositions, which we think will help us to build ultra-fast computers and a more secure Internet in the future. But we still haven’t learned to do it as well as Santa can!
“There is little doubt now to quantum physicists that Santa is exploiting what we know as ‘macroscopic quantum coherence’, which is precisely the same resource used by cutting-edge quantum technologies to outperform technologies based on classical physics.”
Einstein vs Santa
Historically the idea that an object can be in a macroscopic superposition has led to significant controversy. In fact, it has led many scientists over the years to question if quantum physics can really be true. Probably the most famous critic was Albert Einstein, who helped to discover quantum physics over 100 years ago, but then spent the rest of his life arguing that it was incomplete.
However, an intriguing rumour that has been circulating since Einstein’s time is that he hated Christmas (basically, the rumour, which may or may not have originated at the North Pole, implies he was a Grinch who didn’t like Santa Claus). Even after sparking a revolution in physics and establishing himself as the smartest man in history, Einstein still wasn’t as famous as Santa…
Green with envy, some believe Einstein tried to discredit Santa by arguing that quantum superpositions were impossible so no one could possibly visit all the children in the world in one night. Nowadays, scientists don’t take Einstein’s ideas about quantum physics seriously and it is widely accepted that superpositions are real – along with Santa Claus.
Santa’s advanced tech
Even if we agree that Santa uses quantum physics to bring gifts to all the children in the world on the same night, we still don’t understand exactly how he does it.
Dr Mark Mitchison said:
“When we observe a quantum object, we only ever find it in one place at a time. This tells us that superpositions are very fragile. Just looking at them causes them to ‘collapse’, which means the object ends up in just one place and all the other possibilities vanish.
“We are pretty sure that Santa has developed some advanced technology to protect his quantum superposition and stop such a collapse from ruining Christmas. But – just in case – we advise children the world over to go to bed early on Christmas Eve and suggest they don’t try to catch a glimpse of him and risk collapsing his merry superposition!”
Habitable terrestrial planets are those occupying orbits around a star that can maintain surface liquid water under a supporting atmosphere. The study of the evolution of planetary atmospheres has been an important research topic for the last several years, in an effort to determine the most important factors in creating a habitable environment for an exoplanet. A planet found in the habitable zone (HZ) around a star does not necessarily mean that the planet is habitable since stellar activity cannot be neglected. For example, it is well known that stellar emissions in the X-ray and extreme ultraviolet (EUV) leads to enhanced ionization and inflation of planetary ionospheres and atmospheres leading to atmospheric loss. Magnetically active stars produce very intense stellar flares that are often, but not always, accompanied by a coronal mass ejection (CME) and stellar winds leading to more atmospheric loss as observed at Mars. When the Martian dynamo shut down ~4.1 Ga and Mars lost its global magnetosphere, the intense solar wind and radiation ravished its atmosphere resulting in ocean evaporation and atmospheric loss transforming Mars from an early warmer and wetter world to a cold and dry planet with an average surface pressure of only 6 mbar. Simply stated, preservation of an atmosphere is one of the chief ingredients for surface habitability.
It has been shown in previous studies that young stars, particularly one solar mass and smaller, produce extremes such as stellar flares and CMEs that lead to planetary atmospheric loss and that these extremes are closely related to the stellar rotation rate in addition to mass. Johnstone and colleagues found that almost all solar mass stars have converged to slow rotators by 500 Myr after formation producing slower stellar wind. Compared with solar-type stars, it takes a longer time for M-type stars (with lower masses) to slow down. M-type stars also keep magnetically active for a longer period of time. Therefore, the ravaging of planetary atmospheres in the young solar system due to extreme solar radiation and particle fluxes is believed to be a significant factor for our understanding of how an exoplanet will develop and maintain an atmosphere, which is a critical element of a habitable environment. Meanwhile, recent studies show that planetary magnetic fields may protect planets from atmospheric losses, indicating planetary magnetic fields play an important role in planetary habitability.
Another factor that should be considered with respect to the habitability of a terrestrial exoplanet, unrecognized until this paper, concerns the magnetic characteristics of an associated exomoon. With the existence of exoplanets well established, one of the next frontiers is the discovery of exomoons. Today there are a number of exomoon candidates waiting to be confirmed. Since it is without a doubt that they must exist around some exoplanets, it is important to examine what role, if any, they would have in creating an environment that contributes to the habitability of their host planet.
Although speculated for several decades, only recently have scientists determined that our Moon had an extensive magnetosphere for several hundred million years soon after it was formed. Recently, Green and colleagues investigated the expected magnetic topology of the early Earth-Moon magnetospheres and found that they would couple in such a way as to protect the atmosphere of both the Earth and Moon. Assuming similar formation processes for terrestrial planets and their moons, how would these two magnetospheres interact, and what protection would such a combined magnetosphere afford to the atmospheres of early exoplanets and their moons orbiting young stars is the subject of this current research done by James Green and colleagues.
In their paper, they modeled two dipole fields simulating the main field of the exoplanet and the exomoon when the exomoon was at several locations ranging from 4 to 18 Rp from the exoplanet in a stellar wind environment. They take the Earth-Moon dipole strengths presented in their previous paper as their starting conditions illustrating a basic magnetic topology that would evolve over time.
Their results demonstrated that terrestrial exoplanet-exomoon coupled magnetospheres work together to protect the early atmospheres of both the exoplanet and the exomoon. When exomoon magnetospheres are within the exoplanet’s magnetospheric cavity, the exomoon magnetosphere acts like a protective magnetic bubble providing an additional magnetopause confronting the stellar winds when the moon is on the dayside. In addition, magnetic reconnection would create a critical pathway for the atmosphere exchange between the early exoplanet and exomoon. When the exomoon’s magnetosphere is outside of the exoplanet’s magnetosphere it then becomes the first line of defense against strong stellar winds, reducing exoplanet’s atmospheric loss to space.
They have also given a brief discussion on how this type of exomoon would modify radio emissions from magnetized exoplanets.
“Based on the solar system, one of the most well-known wave phenomena for planets with magnetospheres is the release of escaping radio emissions generated by the cyclotron maser instability (CMI) mechanism that derives their named based on the frequency range of the observed emission. It is well known that this type of emission is closely related to the local gyrofrequency above a planet’s aurora and therefore provides important clues to the presence of a planet’s magnetic field and its strength. For example, the Earth’s intense auroral-related radio emission is called Auroral Kilometric Radiation (AKR) and the Jovian Decametric (DAM) emissions are CMI related emissions from Jupiter’s auroral zone.”, said James Green lead author of the study.
Someprevious studies believed that the intense auroral related radio emission is the best indicator of planetary magnetospheres. The CMI generated radio emissions produce intense radiation perpendicular to the local magnetic field but the resulting emission cone can be filled-in by refraction or hollow. For instance, the emission cone of AKR has been observed to be relatively well filled in higher frequencies and may be hollow at the lower frequencies, while the Jovian DAM emissions produce hollow emission cones as illustrated in Figure 1A and Figure 1B, respectively. The Earth’s AKR emission cone points tailward with partially overlapping northern and southern hemisphere cones (only the northern hemisphere cone at one frequency is shown in Figure 1A) and is not dependent on Earth’s rotation or the location of the Moon.
One aspect of the Jovian DAM emission is that it is strongly coupled with the moon Io which has a thin atmosphere allowing an ionospheric current to connect field-lines from Jupiter creating a constant current and therefore a constant aurora and resulting CMI related radio emissions. These Io controlled DAM emissions produce, hollow emission cones that move with Io around the planet which has an orbital period of about 42 hours. Io is in an elliptical orbit and is so close to the planet Jupiter that the energy from the very strong tidal forces is dissipated through volcanic activity on the moon that are so strong that a torus of escaping material is left in its wake that stretches around Jupiter. Alfven waves are set up in the Io torus that produce magnetospheric currents stretching all the way to the Jovian auroral regions that also trigger additional CMI emissions that produce a set of nested hollow emission cones. Near equatorial spacecraft, such as the Voyager 1 and 2 missions, observed the Io-DAM emissions as a series of arc-like structures in frequency-time spectrograms. The shape of the nested emission cones, in frequency-time spectrograms, are strongly controlled by the higher moments of the Jovian magnetic fields since the strongly right-hand polarized DAM radiation propagating from the source over these intense magnetic islands suffer significant refraction. In addition, Jupiter’s moon Ganymede also produces aurora, not only in the upper atmosphere of Jupiter, but also in the very tenuous Ganymede atmosphere since that moon is the only one in the solar system that has been observed to currently generate its own magnetosphere. The rather small Ganymede magnetosphere is anti aligned with Jupiter which is similar to the lower left panel in Figure 2. These connected field lines also facilitate the exchange of atmospheric constituents.
In the case of both an exoplanet and exomoon with magnetospheres, Green and colleagues now observed a new situation in which the exomoon would be controlling the location of a potential CMI emission cone and producing either a hollow or filled in emission pattern. From a distant radio observer, periodicities in an observed CMI emission cone pattern along with the radio emission frequency not only could point to the existence and strength of an exoplanet’s magnetosphere but also the existence of an exomoon. The extent of the emission cone, ranging from completely hollow to completely filled-in provides additional information about the extent of the exoplanet’s ionosphere. In this manner, the detection and analysis of CMI generated radio emissions may provide additional information as to the habitability of the exoplanet.
“In order to understand the long-term evolution of exoplanetary atmospheres and their suitability for creating a habitable environment that may host life, we must understand not only the stellar environment, but also whether these planets and their associated moons have magnetic fields.”, said James Green.
Researchers concluded that, “future detection of exoplanet-exomoon magnetic fields from the detection of CMI radio emissions will provide a wealth of new information that will draw our attention to these systems having a greater chance of habitability.”
References: James Green, Scott Boardsen, Chuanfei Dong, “Magnetospheres of Terrestrial Exoplanets and Exomoons: Implications for Habitability and Detection”, ArXiv, pp. 1-13, 2020. https://arxiv.org/abs/2012.11694v1
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Ever heard of suspension animation?? No.. Let me tell you, it is the process which involves rapidly cooling the brain or person’s body to less than 10°C by replacing the patient’s blood with ice-cold saline solution. Typically the solution is pumped directly into the aorta, the main artery that carries blood away from the heart to the rest of the body.
This procedure was first placed by doctors in 2019, as part of a trial in the US that aims to make it possible to fix traumatic injuries that would otherwise cause death. For example, patients whose hearts have stopped, and have lost more than half their blood due to acute trauma such as gunshot or stab wounds. This process gives surgeons more time to repair the wounds before reviving the patient.
What’s the idea behind the process? Well, at normal body temperature – about 37°C – our cells need a constant supply of oxygen to produce energy. When our heart stops beating, blood no longer carries oxygen to cells. Without oxygen, our brain can only survive for about 5 minutes before irreversible damage occurs. However, lowering the temperature of the body and brain slows or stops all the chemical reactions in our cells, which need less oxygen as a consequence, and thus giving time to surgeons to fix the wounds.
Surgeons still don’t know how long we can extend the time in which someone is in suspended animation. When a person’s cells are warmed up, they can experience reperfusion injuries, in which a series of chemical reactions damage the cell – and the longer they are without oxygen, the more damage occurs. “It may be possible to give people a cocktail of drugs to help minimise these injuries and extend the time in which they are suspended”, says Tisherman to news scientist, “but we haven’t identified all the causes of reperfusion injuries yet”.
But wait a minute, did this process actually worked? Well, surgeons didn’t revealed the actual number of patients it worked on that trail. But, as per my research, there is less than 5% chance that the patient would normally survive. Well, it’s better to count this process rather than dying.
Copyright of this article totally belongs to our author S. Aman. One is allowed to reuse it only by giving proper credit either to him or to us.