Philippa Kaur

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    in Space & Astronomy

    Planet-forming disks around stars may come preloaded with ingredients for life

    The chemistry leading to life may start before stars are even born.

    In the planet-forming disk of gas and dust around a young star, astronomers have detected methanol. The disk is too warm for the methanol to have formed there, so this complex organic molecule probably originated in the interstellar cloud that collapsed to form the star and its disk, researchers report online May 10 in Nature Astronomy. This finding offers evidence that at least some organic matter from interstellar space can seed the disks around newborn stars to provide potential ingredients for life on new planets.

    “That’s pretty exciting, because it means that, in principle, all planets forming around any kind of star could have this material,” says Viviana Guzmán, an astrochemist at the Pontifical Catholic University of Chile in Santiago not involved in the work.

    Complex organic molecules have been observed in interstellar clouds of gas and dust (SN: 3/22/21), as well as in planet-forming disks around young stars (SN: 2/18/08). But astronomers didn’t know whether organic material from interstellar space could survive the formation of a protoplanetary disk, or whether organic chemistry had to start from scratch around new stars.

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    “When you form a star and its disk, it’s not a very easy, breezy process,” says Alice Booth, an astronomer at Leiden University in the Netherlands. Radiation from the new star and shock waves in the imploding material, she says, “could destroy a lot of the molecules that were originally in your initial cloud.”

    Using the ALMA radio telescope array in Chile, Booth and colleagues observed the disk around a bright, young star named HD 100546, about 360 light-years away. There, the team spotted methanol, which is thought to be a building block for life’s molecules, such as amino acids and proteins.

    Methanol could not have originated in the disk, because this molecule forms when hydrogen interacts with carbon monoxide ice, which freezes below temperatures of about –253° Celsius. The disk around HD 100546 is much warmer than that, heated by a star whose surface is roughly 9,700° C — some 4,000 degrees hotter than the sun. So the disk must have inherited its methanol from the interstellar cloud that forged its central star, the researchers conclude.

    “This is the first evidence that the really interesting chemistry we see early on [in star formation] actually survives incorporation into the planet-forming disk,” says Karin Öberg, an astrochemist at Harvard University who was not involved in the work. Astronomers should next search the disks around other young stars for methanol or other organic molecules, she says, to “explore whether this is a one-time, get lucky kind of thing, or whether we can safely assume that planet-forming disks always inherit these kinds of molecules.” More

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    in Humans

    Ancient hominins may have needed midwives to help deliver babies

    By Michael Marshall

    Childbirth may have been difficult for ancient hominins CHRISTIAN JEGOU PUBLIPHOTO DIFFUSION/SCIENCE PHOTO LIBRARY
    It isn’t just modern humans that have found giving birth painful and dangerous. Growing evidence suggests birth was difficult for our hominin relatives millions of years ago. As a result, earlier hominins like Australopithecus may have needed help to deliver their babies.
    Birth is strikingly dangerous for modern humans compared with other primates. Globally, for every 100,000 births in 2017, 211 mothers died. In the worst-affected countries, such as South Sudan, the maternal mortality rate is more than five times that. Many nations have … More

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    in Humans

    Brain's movement control centre may have had key role in our evolution

    By Michael Marshall

    The cerebellum may have had a larger role in human evolution than once thoughtKATERYNA KON/SCIENCE PHOTO LIBRARY
    The key to human evolution may have been at the back of our minds all along – literally. Some of the biggest biochemical differences between human brains and those of other primates are found in the cerebellum, a region at the rear of the brain that has often been overlooked in evolutionary studies.
    The finding adds to growing evidence that changes to the cerebellum have been crucial for the origin of the human mind.

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    All backboned animals have a cerebellum, which is involved in controlling movement.
    “It’s not really associated with much that’s uniquely human,” says Elaine Guevara at Duke University in North Carolina. Instead, neuroscientists seeking to explain the evolution of our brains have tended to focus on the cortex, the thick outer layer of the forebrain – especially the prefrontal cortex, which underpins our ability to consciously decide what to do.
    In recent years, some neuroscientists have argued that the cerebellum has changed more than thought during human evolution, and that these changes may have been crucial.

    Guevara and her colleagues studied the cerebellum and prefrontal cortex at the molecular level. They took brain samples from humans, chimpanzees and monkeys called rhesus macaques, and extracted DNA from both brain regions.
    The team looked to see which parts of the DNA had small molecules called methyl groups attached. Methylation is an example of a so-called epigenetic influence on our genes. Patterns of methylation reflect which genes have been active and inactive during an animal’s life, and they vary between body parts and between species.
    Guevara’s team found that the pattern of methylation in human DNA was different to that in chimps and macaques. Crucially, the difference between species was greater in the cerebellum than in the prefrontal cortex, suggesting there had been more changes there during our evolution.
    It isn’t clear what the methylation changes did, says Guevara. But there are intriguing clues. Some of the genes where the cerebellar methylation patterns were different are known to be involved in changing the strengths of the connections between neurons, a process thought to be important for learning.
    Some of these are also associated with neurodevelopmental differences such as autism and neuropsychiatric conditions such as schizophrenia, both of which may be unique to humans or at least more common in humans, says Guevara.
    Journal reference: PLoS Genetics, DOI: 10.1371/journal.pgen.1009506
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    in Humans

    78'000 year old human burial is oldest in Africa

    Remains of a 3-year-old child discovered in a cave in Kenya called Panga ya Saidi are the oldest known burial in Africa. Researchers named the child Mtoto, which means “child” in Swahili, and estimate that they lived around 78,300 years ago, making this the oldest deliberate burial found in Africa. “It was a child and someone gave it a farewell,” says Martinón-Torres.

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    in Space & Astronomy

    Saturn has a fuzzy core, spread over more than half the planet’s diameter

    One of Saturn’s rings has revealed properties of its core, hidden deep beneath the planet’s golden atmosphere.

    That core isn’t the lump of rock and ice that many scientists had envisioned, the new study finds. Instead, the core is diffuse, pervaded by huge amounts of hydrogen and helium and so spread out that it spans 70,000 kilometers, or about 60 percent of the planet’s diameter, researchers report April 28 at arXiv.org.

    The new intel should help planetary scientists better understand not only how giant planets formed in our solar system but also the nature of such worlds orbiting other stars.  

    To ascertain the structure of Saturn’s core, astronomer Christopher Mankovich and astrophysicist Jim Fuller, both at Caltech, examined the giant planet’s rings. Just as earthquakes help seismologists probe Earth’s interior, oscillations inside Saturn can reveal its internal composition. These oscillations alter Saturn’s gravitational forces, inducing waves in the rings —especially the C ring, which is the nearest of the three main rings to the planet (SN: 1/22/19).

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    By analyzing a wave in that ring, along with data on Saturn’s gravity field from the now-defunct Cassini spacecraft (SN: 9/15/17), Mankovich and Fuller found that the core has about 17 Earth masses of rock and ice. But there’s so much hydrogen and helium mixed in, the core encompasses 55 Earth masses altogether — more than half of Saturn’s total, which is equivalent to the mass of 95 Earths. This “ring seismology” work will appear in a future Nature Astronomy.

    “It’s a new way to look at gas giant planets in the solar system,” says Ravit Helled, a planetary scientist at the University of Zurich who was not involved with the work. “This knowledge is important because it reflects on our understanding of giant exoplanets,” and indicates that giant planets in other solar systems probably have more complex structures than many researchers had thought.

    The discovery also illuminates how Saturn formed, says Nadine Nettelmann, a planetary scientist at the German Aerospace Center in Berlin.

    Older theories posited that a gas giant such as Saturn arises when rock and ice orbiting the sun start to conglomerate. Tenuous gaseous envelopes let additional solid materials sink to the center, forming a compact core. Only later, according to this theory, does the core attract lots of hydrogen and helium — the ingredients that make up most of the planet. Although these elements are gases on Earth, Saturn’s great gravity squeezes most of them into a fluid.

    But newer theories say instead that plenty of gas got incorporated into the core of rock and ice when it was taking shape 4.6 billion years ago. As the planet accreted additional mass, the proportion of gas rose. The structure Mankovich and Fuller deduce for Saturn’s core preserves this formation history, Nettelmann says, because the planet’s very center, representing the oldest part of Saturn, has the greatest proportion of rock and ice. The fraction of rock and ice decrease gradually rather than abruptly from the core’s center to its edge, reflecting the core’s development over time.

    “I find the conclusions very important and very exciting and the line of reasoning very convincing,” Nettelmann says. Still, she cautions that additional waves in the rings should be analyzed for confirmation.

    The type of oscillation that Mankovich and Fuller detect inside Saturn also implies that the core is stable rather than bubbling like a pot of water on a hot stove, which is one way a planet can carry heat from its hot interior outward. The core’s stability may help explain a long-standing puzzle: why Saturn emits more energy than it gets from the sun.

    After the planet formed, it was warm with the heat of its birth, but then it cooled off. The core’s stability could have put a lid on some of this cooling, however, which helped the planet retain heat that it still radiates to this day. In contrast, if the core had instead transported heat via the upwelling and downwelling of material, the planet would have cooled off faster and no longer give off so much heat. More

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    in Humans

    Older children in the year group are more popular than younger peers

    By Karina Shah

    Older teenagers in a year group tend to be more popularStockbroker/MBI/Alamy
    Older teenagers tend, on average, to be more popular than their younger peers in the same class.
    Danelien van Aalst at the University of Groningen in the Netherlands and her colleagues have investigated how relative age affects popularity among 14 to 15-year-olds in the Netherlands, Sweden and England. They collected survey data from 13,251 students from the three countries, who were quizzed between October 2010 and April 2011.

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    Each teenager was asked to identify five of the most popular students in their class. The researchers then compared the popularity of each child to their age relative to that of their peers. They discovered a correlation: the older the student was, the more likely they were to be considered popular.
    “A child enters school before or after a certain cut-off date and that determines how old or young you are relative to your year group,” says van Aalst. “We found that if you’re born right after the cut-off date [making you one of the oldest members of your class], you’re going to be popular.”

    They found that the same effect also applied at the year-group level. Here, it was the children who were oldest relative to all of their peers in the year group – rather than just those in their particular class – that were the most popular.
    All three countries showed roughly the same pattern. However, at the year-group scale, it was most pronounced in England.
    At the classroom level, it was in the Netherlands that the pattern was strongest. This is partly because the country has a system of grade retention – when students don’t meet their academic requirements, their teachers will hold them back a year, which means they then become the oldest in their class and often the most popular.
    This relative age effect has been shown in other areas. “Relative age has earlier been demonstrated to affect school performance – relatively older children do better in school,” says Herman van de Werfhorst at the University of Amsterdam, who wasn’t involved in the study.
    Similarly, previous research has shown that older children tend to be better at sports than younger students in the same year group.
    Journal reference: PLoS One, DOI: 10.1371/journal.pone.0249336

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    in Humans

    What to cook if covid-19 has affected your sense of smell and taste

    By Sam Wong

    OksanaKiian/Getty ImagesFOR many of us, food has been one of the most dependable pleasures in a year when so many normal activities have been put on hold. It seems particularly cruel that a common, lingering symptom of covid-19 is an altered sense of taste and smell, with studies finding that between 40 and 85 per cent of people with the illness experience some loss of these senses.
    The virus that causes covid-19 attaches to ACE2 proteins in the olfactory epithelium, the tissue inside the nose where our smell receptors are located. Once the virus enters these cells, … More

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    in Humans

    Don't Miss: Netflix's Oxygen, a sci-fi thriller with a shocking twist

    Shana Besson/Netflix
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    Oxygen, Alexandre Aja’s sci-fi thriller, is the story of a woman with amnesia (Mélanie Laurent) who is trapped in a cryogenic chamber. Her oxygen is running out and she will survive only if she remembers who she is. On Netflix from 12 May.

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    Crooked Cats tell their own bloody tales in anthropologist Nayanika Mathur’s study of how big cats – tigers, leopards and lions – come to prey on humans. Ecological collapse is an important reason why such attacks occur, but is it the whole story?
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    Cosmos: Reverse perspective looks at Earth from space through collages and graphics, capturing the changes we have lived through since Yuri Gagarin’s first orbit. Online from Pushkin House until 18 May. More