NASA finds Neptune moons locked in 'dance of avoidance'

Screenshot of animation illustrating how the odd orbits of Neptune's inner moons Naiad and Thalassa enable them to avoid each other as they race around the planet.

Even by the wild standards of the outer solar system, the strange orbits that carry Neptune's two innermost moons are unprecedented, according to newly published research.

Orbital dynamics experts are calling it a "dance of avoidance" performed by the tiny moons Naiad and Thalassa. The two are true partners, orbiting only about 1,150 miles (1,850 kilometers) apart. But they never get that close to each other; Naiad's orbit is tilted and perfectly timed. Every time it passes the slower-moving Thalassa, the two are about 2,200 miles (3,540 kilometers) apart.

In this perpetual choreography, Naiad swirls around the ice giant every seven hours, while Thalassa, on the outside track, takes seven and a half hours. An observer sitting on Thalassa would see Naiad in an orbit that varies wildly in a zigzag pattern, passing by twice from above and then twice from below. This up, up, down, down pattern repeats every time Naiad gains four laps on Thalassa.

Although the dance may appear odd, it keeps the orbits stable, researchers said.

"We refer to this repeating pattern as a resonance," said Marina Brozović, an expert in solar system dynamics at NASA's Jet Propulsion Laboratory in Pasadena, California, and the lead author of the new paper, which was published Nov. 13 in Icarus. "There are many different types of 'dances' that planets, moons and asteroids can follow, but this one has never been seen before."

Far from the pull of the Sun, the giant planets of the outer solar system are the dominant sources of gravity, and collectively, they boast dozens upon dozens of moons. Some of those moons formed alongside their planets and never went anywhere; others were captured later, then locked into orbits dictated by their planets. Some orbit in the opposite direction their planets rotate; othersswap orbits with each otheras if to avoid collision.

Neptune has 14 confirmed moons. Neso, the farthest-flung of them, orbits in a wildly elliptical loop that carries it nearly 46 million miles (74 million kilometers) away from the planet and takes 27 years to complete.

Naiad and Thalassa are small and shaped like Tic Tacs, spanning only about 60 miles (100 kilometers) in length. They are two of Neptune's seven inner moons, part of a closely packed system that is interwoven with faint rings.

So how did they end up together -- but apart? It's thought that the original satellite system was disrupted when Neptune captured its giant moon, Triton, and that these inner moons and rings formed from the leftover debris.

"We suspect that Naiad was kicked into its tilted orbit by an earlier interaction with one of Neptune's other inner moons," Brozović said. "Only later, after its orbital tilt was established, could Naiad settle into this unusual resonance with Thalassa."

Brozović and her colleagues discovered the unusual orbital pattern using analysis of observations by NASA's Hubble Space Telescope. The work also provides the first hint about the internal composition of Neptune's inner moons. Researchers used the observations to compute their mass and, thus, their densities -- which were close to that of water ice.

"We are always excited to find these co-dependencies between moons," said Mark Showalter, a planetary astronomer at the SETI Institute in Mountain View, California, and a co-author of the new paper. "Naiad and Thalassa have probably been locked together in this configuration for a very long time, because it makes their orbits more stable. They maintain the peace by never getting too close."

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Tool for studying decision-making is ineffective for training better behavior

A two-step task commonly used to study people's decision-making behaviors does not appear to be effective for training people to rely more on goal-oriented behaviors and less on habitual behaviors. Elmar Grosskurth of Inselspital University Hospital Bern, Switzerland, and colleagues present these findings in PLOS Computational Biology.

Some psychiatric disorders, such as addiction and obsessive-compulsive disorder, heavily rely on habitual behaviors at the expense of goal-oriented behaviors. Many studies have used a two-step experimental approach to investigate these behaviors. In the new study, Grosskurth and colleagues tested whether the two-step task could also be used to train people to engage in more goal-oriented strategies. Such a training would be beneficial for the above-mentioned psychiatric disorders to reduce habitual behaviors and enhance goal-directed decisions.

The researchers recruited 33 healthy participants who each completed 1005 trials of the two-step task over five weeks. In the first step of each trial, the participant chose between two different shapes on a computer screen. That choice was associated with a probability that influenced whether one or another of two new pairs of shapes now appeared. The participant then chose a shape from the second pair and received a small monetary reward or not, depending on their choice.

As usual for the two-step task, the participants showed a mix of goal-directed versus habitual behaviors in making their choices. However, analysis of their choices across five weeks of intensive training suggests that the training had no effect on goal-directed or habitual behavior, nor on the balance between the two. Neuroimaging of brain circuits thought to underlie these behaviors supported these findings, showing that the training did not affect brain activity.

"Our findings suggest that the two-step task in its current form has methodological drawbacks which are not suitable for training purposes," says Lisa Holper, the senior author of the study. This result was observed in healthy people and may be different under psychiatric conditions.

The authors suggest that future work could focus on developing a more sophisticated version of the two-step task that could be used for psychiatric patients to train goal-directed behaviors while reducing habitual behavior.

From Science Daily

DNA data offers scientific look at 500 years of extramarital sex in Western Europe

These days it's easy to resolve questions about paternity with over-the-counter test kits. Now, researchers have put DNA evidence together with long-term genealogical data to explore similar questions of biological fatherhood on a broad scale among people living in parts of Western Europe over the last 500 years.

The findings reported in Current Biology on November 14 yielded some surprises. While the number of so-called extra-pair paternity (EPP) events overall was (not surprisingly) fairly low, their frequency varied considerably among people depending on their circumstances. Specifically, evidence of EPP events turned up much more often in people of lower socioeconomic status who lived in densely populated cities in the 19th century.

"Of course, extra-pair paternity, especially due to adultery, is a popular topic in gossip, jokes, TV series, and literature," said Maarten Larmuseau of KU Leuven and Histories, Belgium. "But scientific knowledge on this phenomenon is still highly limited, especially regarding the past.

"Our research shows that the chance of having extra-pair paternity events in your family history really depends on the social circumstances of your ancestors. If they lived in cities and were of the lower socioeconomic classes, the chances that there were EPP events in your family history are much higher than if they were farmers."

Evolutionarily speaking, it's clear that remaining faithful to one's partner isn't always the most advantageous strategy. Males may benefit from straying by siring extra offspring; females may benefit by mating with superior males. But in human societies over time, how often has EPP really happened?

In the new study, Larmuseau's team took the first broad look at this question to find that social context really matters. Their study covered a time period of several centuries during which there were dramatic changes in the human social environment, including the rapid urbanization that accompanied the Industrial Revolution in 19th century Western Europe. To estimate historical EPP rates among married couples, they identified 513 pairs of contemporary adult males living in Belgium and the Netherlands who, based on genealogical evidence, shared a common paternal ancestor and therefore -- barring an EPP event -- should have carried the same Y chromosome.

The evidence showed no significant difference in EPP rates between countries despite key religious differences, they report. But they varied widely with socioeconomic status and population density. The EPP rate was much lower among farmers and more well-to-do craftsmen and merchants (about 1%) than among lower class laborers and weavers (about 4%).

EPP rates also rose with population density. Putting the two together, the researchers report that the estimated EPP rates for the families varied by more than one order of magnitude, from about 0.5% among the middle to high classes and farmers living in the most sparsely populated towns to almost 6% for the low socioeconomic classes living in the most densely populated cities.

The researchers say the findings support evolutionary theories suggesting that individual incentives and opportunities for seeking or preventing extra-pair mating should depend on the social context. They also debunk the notion that EPP rates in Western society are generally high, they say, noting that the evidence puts average rates at around 1%.

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Ancient Egyptians gathered birds from the wild for sacrifice and mummification

Ibis

In ancient Egypt, Sacred Ibises were collected from their natural habitats to be ritually sacrificed, according to a study released November 13, 2019 in the open-access journal PLOS ONE by Sally Wasef of Griffith University, Australia and colleagues.

Egyptian catacombs are famously filled with the mummified bodies of Sacred Ibises. Between around 664BC and 250AD, it was common practice for the birds to be sacrificed, or much more rarely worshipped in ritual service to the god Thoth, and subsequently mummified. In ancient sites across Egypt, these mummified birds are stacked floor to ceiling along kilometers of catacombs, totaling many millions of birds. But how the Egyptians got access to so many birds has been a mystery; some ancient texts indicate that long-term farming and domestication may have been employed.

In this study, Wasef and colleagues collected DNA from 40 mummified Sacred Ibis specimens from six Egyptian catacombs dating to around 2500 years ago and 26 modern specimens from across Africa. 14 of the mummies and all of the modern specimens yielded complete mitochondrial genome sequences. These data allowed the researchers to compare genetic diversity between wild populations and the sacrificed collections.

If the birds were being domesticated and farmed, the expected result would be low genetic diversity due to interbreeding of restricted populations, but in contrast, this study found that the genetic diversity of mummified Ibises within and between catacombs was similar to that of modern wild populations. This suggests that the birds were not the result of centralized farming, but instead short-term taming. The authors suggest the birds were likely tended in their natural habitats or perhaps farmed only in the times of year they were needed for sacrifice.

The authors add: "We report the first complete ancient genomes of the Egyptian Sacred Ibis mummies, showing that priests sustained short-term taming of the wild Sacred Ibis in local lakes or wetlands contrary to centralised industrial scale farming of sacrificial birds."

From Science Daily

Experts unlock key to photosynthesis, a find that could help us meet food security demands

Green leaf in sunlight.

Scientists have solved the structure of one of the key components of photosynthesis, a discovery that could lead to photosynthesis being 'redesigned' to achieve higher yields and meet urgent food security needs.

The study, led by the University of Sheffield and published today in the journal Nature, reveals the structure of cytochrome b6f -- the protein complex that significantly influences plant growth via photosynthesis.

Photosynthesis is the foundation of life on Earth providing the food, oxygen and energy that sustains the biosphere and human civilisation.

Using a high-resolution structural model, the team found that the protein complex provides the electrical connection between the two light-powered chlorophyll-proteins (Photosystems I and II) found in the plant cell chloroplast that convert sunlight into chemical energy.

Lorna Malone, the first author of the study and a PhD student in the University of Sheffield's Department of Molecular Biology and Biotechnology, said: "Our study provides important new insights into how cytochrome b6f utilises the electrical current passing through it to power up a 'proton battery'. This stored energy can then be then used to make ATP, the energy currency of living cells. Ultimately this reaction provides the energy that plants need to turn carbon dioxide into the carbohydrates and biomass that sustain the global food chain."

The high-resolution structural model, determined using single-particle cryo-electron microscopy, reveals new details of the additional role of cytochrome b6f as a sensor to tune photosynthetic efficiency in response to ever-changing environmental conditions. This response mechanism protects the plant from damage during exposure to harsh conditions such as drought or excess light.

Dr Matt Johnson, reader in Biochemistry at the University of Sheffield and one of the supervisors of the study added: "Cytochrome b6f is the beating heart of photosynthesis which plays a crucial role in regulating photosynthetic efficiency.

"Previous studies have shown that by manipulating the levels of this complex we can grow bigger and better plants. With the new insights we have obtained from our structure we can hope to rationally redesign photosynthesis in crop plants to achieve the higher yields we urgently need to sustain a projected global population of 9-10 billion by 2050."

The research was conducted in collaboration with the Astbury Centre for Structural Molecular Biology at the University of Leeds.

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Extinct giant ape directly linked to the living orangutan

Modern-day orangutan

By using ancient protein sequencing, researchers have retrieved genetic information from a 1.9 million year old extinct, giant primate that used to live in a subtropical area in southern China. The genetic information allows the researchers to uncover the evolutionary position of Gigantopithecus blacki, a three-meter tall and may be up to 600 kg heavy primate, revealing the orangutan as its closest, living relative.

It is the first time that genetic material this old has been retrieved from a warm, humid environment. The study is published in the scientific journal Nature, and the results are groundbreaking within the field of evolutionary biology, according to Frido Welker, Postdoc at the Globe Institute at the Faculty of Health and Medical Sciences and first author of the study.

'Primates are relatively close to humans, evolutionary speaking. With this study, we show that we can use protein sequencing to retrieve ancient genetic information from primates living in subtropical areas even when the fossil is two million years old. Until now, it has only been possible to retrieve genetic information from up to 10,000-year-old fossils in warm, humid areas. This is interesting, because ancient remains of the supposed ancestors of our species, Homo sapiens, are also mainly found in subtropical areas, particularly for the early part of human evolution. This means that we can potentially retrieve similar information on the evolutionary line leading to humans', says Frido Welker.

Today, scientists know that the human and the chimpanzee lineages split around seven or eight million years ago. With the previous methodologies though, they could only retrieve human genetic information not older than 400,000 years. The new results show the possibility to extend the genetic reconstruction of the evolutionary relationships between our species and extinct ones further back in time, at least up to two million years -- covering a much larger portion of the entire human evolution.

Analyzing ancient dental enamel proteins using mass spectrometry-based proteomics

In a recent study, also published on Nature, Enrico Cappellini, Associate Professor at the Globe Institute and senior author on this study, initially demonstrated, together with an international team of colleagues, the massive potential of ancient protein sequencing.

'By sequencing proteins retrieved from dental enamel about two million years old, we showed it is possible to confidently reconstruct the evolutionary relationships of animal species that went extinct too far away in time for their DNA to survive till now. In this study, we can even conclude that the lineages of orangutan and Gigantopithecus split up about 12 million years ago', says Enrico Cappellini.

Sequencing protein remains two million years old was made possible by stretching to its limits the technology at the base of proteomic discovery: mass spectrometry. State of the art mass spectrometers and the top palaeoproteomics expertise needed to get the best out of such sophisticated instrumentation are key resources deriving from the decade-long strategic collaboration with Jesper Velgaard Olsen, Professor at Novo Nordisk Foundation Center for Protein Research and co-author on this study.

The mystery of Gigantopithecus

The fossil evidence attributed to Gigantopithecus was initially discovered in southern China in 1935, and it is currently limited to just a few lower jaws and lots of teeth. No complete skull and no other bone from the rest of the skeleton has been found so far. As a result, there has been a lot of speculation about the physical appearance of this mysterious animal.

'Previous attempts to understand which could be the living organism most similar to Gigantopithecus could only be based on the comparison of the shape of the fossils with skeletal reference material from living great apes. Ancient DNA analysis was not an option, because Gigantopithecus went extinct approximately 300,000 years ago, and in the geographic area Gigantopithecus occupied no DNA older than approximately 10,000 years has been retrieved so far. Accordingly, we decided to sequence dental enamel proteins to reconstruct its evolutionary relation with living great apes, and we found that orangutan is Gigantopithecus' closest living relative', says Enrico Cappellini.

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Spot the difference: Two identical-looking bird species with very different genes

New research by the Milner Centre for Evolution academics in collaboration with Sun Yat-sen University in Guangzhou (China) shows that Southern and Northern breeding populations of plovers in China are in fact two distinct species: Kentish plover (Charadrius alexandrinus) in the North and white-faced plover (Charadrius dealbatus) in the South.

Using state-of-the-art genomics analysis, the team revealed that the Kentish plover and white-faced plover diverged approximately half a million years ago due to cycling sea level changes between the Eastern and Southern China Sea causing intermittent isolation of the two regional populations.

The results show that despite looking very similar, the two plover species have high levels of genetic divergence on their sex chromosomes, (Z chromosome) than on other chromosomes, indicating that sexual selection might play a role to in the evolution of the two species.

Dr Yang Liu, a visiting scholar from Sun Yat-sen University at the Milner Centre for Evolution, led the work. He said: "The initial divergence of the two plovers was probably triggered by the geographical isolation.

"However, other factors, such as ecological specialisations, behavioural divergence, and sexual selection could also contribute to the speciation of the two species.

"In future studies, we wish to understand how these factors operate on plover populations."

Dr Araxi Urrutia, Senior Lecturer from the Milner Centre for Evolution at the University of Bath, said: "Speciation -- the process by which new species evolve -- is the basis of all biodiversity around us, yet our understanding of how new species arise is still limited.

"By studying recent divergence patterns, where the two species still able to reproduce with each other, we can better understand the conditions on which all species, including our own species, have evolved."

The team have published their findings in two papers. The first paper revealed small to moderate differences between Kentish and white-faced plover in their appearance (morphology), diet and behaviour. The second study produced the first genome of the Kentish plover, one of the few published genomes from shorebirds.

Dr Liu said: "The genomic resources generated by our team will help investigate other important evolutionary questions, such as genetic basis of local adaptation, migration and mating system variation."

Led by Dr Liu, the research team also included Dr Araxi Urrutia, Professor Tamás Székely and a former NERC funded PhD student Dr Kathryn Maher.

The research is part of a long-term study on the Kentish plover that has been running for over 30 years, led by Professor Székely.

He said: "Plovers are excellent model systems to understand breeding system evolution.

"These small, drab shorebirds have worldwide distribution, and they are amenable to field studies.

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At future Mars landing spot, scientists spy mineral that could preserve signs of past life

Next year, NASA plans to launch a new Mars rover to search for signs of ancient life on the Red Planet. A new study shows that the rover's Jezero crater landing site is home to deposits of hydrated silica, a mineral that just happens to be particularly good at preserving biosignatures.

"Using a technique we developed that helps us find rare, hard-to-detect mineral phases in data taken from orbiting spacecraft, we found two outcrops of hydrated silica within Jezero crater," said Jesse Tarnas, a Ph.D. student at Brown University and the study's lead author. "We know from Earth that this mineral phase is exceptional at preserving microfossils and other biosignatures, so that makes these outcrops exciting targets for the rover to explore."

The research is published in Geophysical Research Letters.

NASA announced late last year that its Mars 2020 rover would be headed to Jezero, which appears to have been home to an ancient lake. The star attraction at Jezero is a large delta deposit formed by ancient rivers that fed the lake. The delta would have concentrated a wealth of material from a vast watershed. Deltas on Earth are known to be good at preserving signs of life. Adding hydrated silica to the mix at Jezero increases that preservation potential, the researchers say. One of the silica deposits was found on the edge of the delta at low elevation. It's possible that the minerals formed in place and represent the bottom layer of the delta deposit, which is a great scenario for preserving signs of life.

"The material that forms the bottom layer of a delta is sometimes the most productive in terms of preserving biosignatures," said Jack Mustard, a professor at Brown and study co-author. "So if you can find that bottomset layer, and that layer has a lot of silica in it, that's a double bonus."

For the study, researchers used data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument that flies aboard NASA's Mars Reconnaissance Orbiter. The technique applied to the CRISM data used big data analysis methods to tease out the weak spectral signature of the silica deposits.

While the geologic context of the deposits suggests they could have formed at the base of the delta, it's not the only possibility, the researchers say. The minerals could have formed upstream in the watershed that fed Jezero and been washed subsequently into the crater, by volcanic activity or later episodes of water saturation in the Jezero crater lake. The rover should be able to isolate the real source, the researchers say.

"We can get amazing high-resolution images and compositional data from orbit, but there's a limit on what we can discern in terms of how these minerals formed," Tarnas said. "Given instruments on the rover, however, we should be able to constrain the origin of these deposits."

The rover will be able to perform fine-scale chemical analysis of the deposits and provide a close-up view of how the deposits are situated in relation to surrounding rock units. It will also have a sensor similar to CRISM to link orbital and lander data. That will go a long way to determining how the deposits formed. What's more, one instrument aboard the rover is able to look for complex organic material. If the silica deposits have high concentrations of organics, it would be an especially intriguing find, the researchers say.

And in addition to the work the rover does on site, it will also cache samples to be returned to Earth by future missions.

Read more at Science Daily

The smell of old books could help preserve them

Old books give off a complex mélange of odors, ranging from pleasant (almonds, caramel and chocolate) to nasty (formaldehyde, old clothes and trash). Detecting early signs of paper degradation could help guide preservation efforts, but most techniques destroy the very paper historians want to save. Now, researchers reporting in ACS Sensors have developed an electronic nose that can non-destructively sniff out odors emitted by books of different paper compositions, conditions and ages.

Paper is made primarily of cellulose, along with other plant components, and additives that improve the paper's properties. Cellulose is resistant to ageing, but the other paper components are much more vulnerable to degradation by heat, humidity and UV light. Before 1845, paper was made mainly from cotton and linen rags, which were relatively pure forms of cellulose and therefore quite stable. Then, in 1845, inventors developed a process to make paper from wood-pulp fibers. This paper is less durable than that made from cotton, but wood is cheaper and more readily available. In 1980, the advent of acid-free paper was a boon to preservationists because it degrades much more slowly than acidic wood-pulp paper. Marta Veríssimo, M. Teresa Gomes and colleagues wanted to develop an electronic nose that could non-destructively detect early signs of paper degradation from the volatile organic compounds (VOCs) books emit.

The researchers collected 19 books published from 1567 to 2016. They classified the books by time period, paper composition, color and visible state. Then, the researchers collected VOCs released from the books and detected the gases with an electronic nose containing six sensors that selectively bound different VOCs. The electronic nose clearly distinguished between paper from cotton or linen rags and paper from wood, as well as among books from three different time periods. Unexpectedly, some books published after 1990 still contained acidic paper, which the sensor discriminated from books with acid-free paper. And finally, the device sniffed out yellowing books, and new and used books from the same time period. The sensitive new method could help identify books in need of preservation, as well as help protect books from VOCs emitted by their neighbors on a shelf.

From Science Daily

Distant worlds under many suns

Illustration of exoplanet with two suns.

Is Earth the only habitable planet in the universe or are there more worlds somewhere out there that are capable of supporting life? And if there are, what might they look like? In a bid to answer these fundamental questions, scientists are searching space for exoplanets: distant worlds that orbit other stars outside our solar system.

More than 4,000 exoplanets are known to date, most of them orbiting single stars like our Sun. Now astrophysicist Dr Markus Mugrauer of Friedrich Schiller University Jena, Germany, has discovered and characterised many new multiple star systems that contain exoplanets. The findings confirm assumptions that the existence of several stars influences the process by which planets are formed and develop. The study by Mugrauer, of the Astrophysical Institute and University Observatory of the University of Jena, has now been published in the specialist journal Monthly Notices of the Royal Astronomical Society.

Space telescope provides precise data

"Multiple star systems are very common in our Milky Way," explains Mugrauer. "If such systems include planets, they are of particular interest to Astrophysics, because the planetary systems in them can differ from our solar system in fundamental ways." To find out more about these differences, Mugrauer searched more than 1,300 exoplanet host stars with exoplanets orbiting them to see whether they have companion stars. To this end, he accessed the precise observation data of the Gaia space telescope, which is operated by the European Space Agency (ESA).

In this way, he succeeded in demonstrating the existence of around 200 companion stars to planetary host stars that are up to 1,600 light years away from the Sun. With the help of the data, Mugrauer was also able to characterise the companion stars and their systems in more detail. He found that there are both tight systems with distances of only 20 astronomical units (au) -- which in our solar system corresponds approximately to the distance between the Sun and Uranus -- as well as systems with stars that are over 9,000 au from each other.

Red and white dwarfs

The companion stars also vary as to their mass, temperature and stage of evolution. The heaviest among them weigh 1.4 times more than our Sun, while the lightest have only 8 per cent of the Sun's mass. Most of the companion stars are low-mass, cool dwarf stars that glow faintly red. However, eight white dwarfs were also identified among the faint stellar companions. A white dwarf is the burnt-out core of a sun-like star, which is only about as big as our Earth, but half as heavy as our Sun. These observations show that exoplanets can indeed survive the final evolutionary stage of a nearby sun-like star.

Double, triple and quadruple star systems with exoplanets

The majority of the star systems with exoplanets identified in the study have two stars. However, some two dozen hierarchical triple star systems and even a quadruple star system were detected. In the range of distances investigated, of between approximately 20 and 10,000 astronomical units, a total of 15 per cent of the stars studied have at least one companion star. This is only about half the frequency expected in general for solar-like stars. In addition, the companion stars detected show distances about five times greater than in ordinary systems.

"These two factors taken together could indicate that the influence of several stars in a star system disrupts the process of planet formation as well as the further development of their orbits," says Mugrauer. The cause of this could be first the gravitational impact of a stellar companion on the gas and dust disc in which planets form around their host star. Later, the gravitation of the stellar companion influences the motion of the planets around their host star.

Read more at Science Daily