Saturday, May 30, 2020

Metal Collector Made of Bacteria


Microorganisms produce substances capable of binding metals from the environment. Their blueprints might be worth copying.

Bacteria, fungi and plants sometimes produce metal-binding substances that can be harnessed, for example for the extraction of raw materials, for their separation, for cleaning soils or for medical purposes. Professor Dirk Tischler, Head of the Microbial Biotechnology research group at Ruhr-Universität Bochum (RUB), outlines how these natural substances or modified semi-artificial variants of them can be produced according to genetic information in an article in Natural Product Reports from 19 May 2020.

Dirk Tischler was invited to write a review article about metal-binding substances.
Dirk Tischler
Credit:  © RUB, Marquard


How to extract metals from the environment

Microorganisms such as fungi and bacteria as well as plants generate a wide range of chemical substances that are not absolutely necessary for their survival. Such so-called secondary metabolites are usually formed in response to current environmental conditions. They include metal-binding molecules called chelators. The best described group of chelators are the iron-binding siderophores. 

They are relevant for many metabolic processes, as iron is an essential component of many enzymes and signalling pathways. For example, pathogenic bacteria use siderophores to extract iron from their host for their metabolism. The host might then suffer from iron deficiency. But siderophores are also used by bacteria living in soil that thus get access to iron and, as a result, gain an advantage over other organisms in the same habitat. In addition to iron-specific chelators, there are a number of others for various metals and metalloids such as zinc, vanadium, molybdenum or even uranium oxides.

Many potential applications

“Such chelators have many potential applications,” explains Dirk Tischler. “They can be used, for example, to remediate floors, selectively extract or separate raw materials, or in biosensorics or medicine.” In medical applications, siderophores are used to treat iron overload in the body, a disorder known as “iron storage disease”.

Over the last few years, his research group, together with other teams, has identified further strains that form chelators and described new structures. They have also successfully deciphered the genetic information for the formation of these substances and introduced them into easy-to-handle organisms such as Escherichia coli bacteria. These bacteria then serve as producers of the required natural substances or of modified substances. “This is how we can create semi-artificial compounds,” says Dirk Tischler.

Biosynthesis of precursors

In the review article, he describes the different natural chelators and their ability to bind metals and metalloids and explores current and potential future applications. “At present, we are using the knowledge we’ve gained so far to create artificial biosynthetic pathways that enable us to generate and characterise precursors of siderophores,” concludes Tischler. These precursors will subsequently be chemically modified in order to gain access to new drug classes.
Funding

The research was partially funded by Dechema within the framework of the Max Buchner scholarship MBFSt 3646 and the Ministry of Innovation, Science and Research in North Rhine-Westphalia (PtJ-TRI/1141ng006).


Contacts and sources:
Prof. Dr. Dirk Tischler
Research group Microbial Biotechnology
Faculty of Biology and Biotechnology

Ruhr-University Bochum

Publications:
Marika Hofmann, Gerardo Retamal-Morales, Dirk Tischler: Metal binding ability of microbial natural metal chelators and potential applications, in: Natural Product Reports, 2020, DOI: 10.1039/C9NP00058E

Artur Maier, Sarah Wansel, Alvaro Gomez Baraibar, Carolin Mügge, Dirk Tischler: N-Hydroxydiamine – vielseitige Bausteine für Wirkstoffsynthesen, in: Biospektrum 2020, DOI: 10.1007/s12268-020-1374-6




Chimpanzees Help Trace the Evolution of Human Speech Back to Ancient Ancestors


Chimpanzee lip-smacks exhibit a speech-like rhythm, a group of researchers led by the University of Warwick have found.

They found chimpanzees produce lip-smacks at a speech-like rhythm of open-close mouth cycles close to 5Hz (i.e. 5 open-close cycles per second), confirming that speech-rhythm was built upon existing primate signal systems.

Similarly to chimpanzees, fast-paced mouth signals with a speech-like rhythm have now been described in orangutans and several monkey species, confirming altogether that speech has ancient roots within primate communication.

One of the most promising theories for the evolution of human speech has finally received support from chimpanzee communication, in a study conducted by a group of researchers led by the University of Warwick.

The evolution of speech is one of the longest-standing puzzles of evolution. However, inklings of a possible solution started emerging some years ago when monkey signals involving a quick succession of mouth open-close cycles were shown to exhibit the same pace of human spoken language.


Credit:  Katie Slocombe, University of Warwick

In the paper ‘Chimpanzee lip-smacks confirm primate continuity for speech-rhythm evolution’, published today, the 27th May, in the journal Biology Letters, a consortium of researchers, including St Andrews University and the University of York, led by the University of Warwick, have found that the rhythm of chimpanzee lip-smacks also exhibit a speech-like signature – a critical step towards a possible solution to the puzzle of speech evolution.

Just like each and every language in the world, monkey lip-smacks have previously shown a rhythm of about 5 cycles/second (i.e. 5Hz). This exact rhythm had been identified in other primate species, including gibbon song and orangutan consonant-like and vowel-like calls. However there was no evidence from African apes, such as gorillas, bonobos and chimpanzees - who are closer related to humans, meaning the plausibility of this theory remained on hold

Two Chimpanzees grooming each other. 

Credit: Catherine Hobaiter

Now, the team of researchers using data from 4 chimpanzee populations have confirmed that they too produce mouth signals at a speech-like rhythm. The findings show there has been most likely a continuous path in the evolution of primate mouth signals with a 5Hz rhythm. Proving that evolution recycled primate mouth signals into the vocal system that one day was to become speech.

African great apes, the closest species to humans, had never been studied for the rhythm of their communication signals. Researchers investigated the rhythm of chimpanzee lip-smacks, produce by individuals while they groom another and found that chimpanzees produce lip-smacks at an average speech-like rhythm of 4.15 Hz.

Researchers used data across two captive and two wild populations, using video recordings collected at Edinburgh Zoo and Leipzig Zoo, and recordings of wild communities including the Kanyawara and the Waibira community, both in Uganda.

Dr Adriano Lameira, from the Department of Psychology at the University of Warwick comments:

“Our results prove that spoken language was pulled together within our ancestral lineage using “ingredients” that were already available and in use by other primates and hominids. This dispels much of the scientific enigma that language evolution has represented so far. We can also be reassured that our ignorance has been partly a consequence of our huge underestimation of the vocal and cognitive capacities of our great ape cousins.

“We found pronounced differences in rhythm between chimpanzee populations, suggesting that these are not the automatic and stereotypical signals so often attributed to our ape cousins. Instead, just like in humans, we should start seriously considering that individual differences, social conventions and environmental factors may play a role in how chimpanzees engage “in conversation” with one another.

“If we continue searching, new clues will certainly unveil themselves. Now it’s a matter of mastering the political and societal power to preserve these precious populations in the wild and continue enabling scientists to look further.”






Contacts and sources:
Alice Scott
University of Warwick

Publication: Chimpanzee lip-smacks confirm primate continuity for speech-rhythm evolution. André S. Pereira, Eithne Kavanagh, Catherine Hobaiter, Katie E. Slocombe, Adriano R. Lameira. Biology Letters, 2020; 16 (5): 20200232 DOI: 10.1098/rsbl.2020.0232 https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0232




The Most Common Organism in the Oceans Harbors a Virus in Its DNA


The most common organism in the oceans, and possibly on the entire planet, is a family of single-celled marine bacteria called SAR11. These drifting organisms look like tiny jelly beans and have evolved to outcompete other bacteria for scarce resources in the oceans.

The viruses, colored orange, attached to a membrane vesicle from the SAR11 marine bacteria, colored gray, that was the subject of this study.
grey oval with orange circles attached
Credit: Morris et al./Nature Microbiology
We now know that this group of organisms thrives despite — or perhaps because of — the ability to host viruses in their DNA. A study published in May in Nature Microbiology could lead to new understanding of viral survival strategies.

University of Washington oceanographers discovered that the bacteria that dominate seawater, known as Pelagibacter or SAR11, hosts a unique virus. The virus is of a type that spends most of its time dormant in the host’s DNA but occasionally erupts to infect other cells, potentially carrying some of its host’s genetic material along with it.

Pelagibacter, or SAR11, is a single-celled bacterium that survives off dissolved carbon throughout the oceans. It makes up one in four cells on the ocean’s surface.
Credit: NOAA

“Many bacteria have viruses that exist in their genomes. But people had not found them in the ocean’s most abundant organisms,” said co-lead author Robert Morris, a UW associate professor of oceanography. “We suspect it’s probably common, or more common than we thought — we just had never seen it.”

This virus’ two-pronged survival strategy differs from similar ones found in other organisms. The virus lurks in the host’s DNA and gets copied as cells divide, but for reasons still poorly understood, it also replicates and is released from other cells.

The new study shows that as many as 3% of the SAR11 cells can have the virus multiply and split, or lyse, the cell — a much higher percentage than for most viruses that inhabit a host’s genome. This produces a large number of free viruses and could be key to its survival.

“There are 10 times more viruses in the ocean than there are bacteria,” Morris said. “Understanding how those large numbers are maintained is important. How does a virus survive? If you kill your host, how do you find another host before you degrade?”

The study could prompt basic research that could help clarify host–virus interactions in other settings.

“If you study a system in bacteria, that is easier to manipulate, then you can sort out the basic mechanisms,” Morris said. “It’s not too much of a stretch to say it could eventually help in biomedical applications.”

The UW oceanography group had published a previous paper in 2019 looking at how marine phytoplankton, including SAR11, use sulfur. That allowed the researchers to cultivate two new strains of the ocean-dwelling organism and analyze one strain, NP1, with the latest genetic techniques.

Co-lead author Kelsy Cain fills a bottle with seawater off the coast of Oregon aboard the RV Roger Revelle during the VISIONS ’17 research cruise in July 2017. Cain diluted the water several times and then isolated a new strain of SAR11 bacteria that became the focus of the new paper.

Credit: Mitch Elend/University of Washington

Co-lead author Kelsy Cain collected samples off the coast of Oregon during a July 2017 research cruise. She diluted the seawater several times and then used a sulfur-containing substance to grow the samples in the lab — a difficult process, for organisms that prefer to exist in seawater.

The team then sequenced this strain’s DNA at the UW PacBio sequencing center in Seattle.

“In the past we got a full genome, first try,” Morris said. “This one didn’t do that, and it was confusing because it’s a very small genome.”

The researchers found that a virus was complicating the task of sequencing the genome. Then they discovered a virus wasn’t just in that single strain.

“When we went to grow the NP2 control culture, lo and behold, there was another virus. It was surprising how you couldn’t get away from a virus,” said Cain, who graduated in 2019 with a UW bachelor’s in oceanography and now works in a UW research lab.

Cain’s experiments showed that the virus’ switch to replicating and bursting cells is more active when the cells are deprived of nutrients, lysing up to 30% of the host cells. The authors believe that bacterial genes that hitch a ride with the viruses could help other SAR11 maintain their competitive advantage in nutrient-poor conditions.

“We want to understand how that has contributed to the evolution and ecology of life in the oceans,” Morris said.

Co-authors are postdoctoral researcher Kelli Hvorecny and associate professor Justin Kollman in the UW Department of Biochemistry. The study was funded by the National Science Foundation and the National Institutes of Health’s National Institute of Allergy and Infectious Disease.



Contacts and sources:
Hannah Hickey
University of Washington

Publication: Lysogenic host–virus interactions in SAR11 marine bacteria. Robert M. Morris, Kelsy R. Cain, Kelli L. Hvorecny, Justin M. Kollman. Nature Microbiology, 2020; DOI: 10.1038/s41564-020-0725-x



World's Oldest Bug Fossil from 425 Million Years Ago

UT Austin scientists found that the fossil millipede Kampecaris obanensis was 425 million years old.
Fossil Millipede Resized
Credit: British Geological Survey.

A 425-million-year-old millipede fossil from the Scottish island of Kerrera is the world’s oldest “bug” — older than any known fossil of an insect, arachnid or other related creepy-crawly, according to researchers at The University of Texas at Austin.

The findings offer new evidence about the origin and evolution of bugs and plants, suggesting that they evolved much more rapidly than some scientists believe, going from lake-hugging communities to complex forest ecosystems in just 40 million years.

“It’s a big jump from these tiny guys to very complex forest communities, and in the scheme of things, it didn’t take that long,” said Michael Brookfield, a research associate at UT Austin’s Jackson School of Geosciences and adjunct professor at the University of Massachusetts Boston. “It seems to be a rapid radiation of evolution from these mountain valleys, down to the lowlands, and then worldwide after that.”

The research was recently published in the journal Historical Biology. Brookfield led the study with co-authors including Elizabeth Catlos, an associate professor in the Jackson School’s Department of Geological Sciences, and Stephanie Suarez, a doctoral student at the University of Houston who made improvements to the fossil dating technique used in the study when she was an undergraduate at the Jackson School.

The world’s oldest known “bug” fossil is from Kerrera, an island in Scotland.
Credit: Michael Brookfield.

The team found that the ancient millipede fossil is 425 million years old, or about 75 million years younger than the age other scientists have estimated the oldest millipede to be using a technique known as molecular clock dating, which is based on DNA’s mutation rate. Other research using fossil dating found that the oldest fossil of a land-dwelling, stemmed plant (also from Scotland) is 425 million years old and 75 million years younger than molecular clock estimates.

Although it’s certainly possible there are older fossils of both bugs and plants, Brookfield said that the fact they haven’t been found — even in deposits known for preserving delicate fossils from this era — could indicate that the ancient millipede and plant fossils that have already been discovered are the oldest specimens.

If that’s the case, it also means both bugs and plants evolved much more rapidly than the timeline indicated by the molecular clock. Bountiful bug deposits have been dated to just 20 million years later than the fossils. And by 40 million years later, there’s evidence of thriving forest communities filled with spiders, insects and tall trees.

“Who is right, us or them?” Catlos said. “We’re setting up testable hypotheses – and this is where we are at in the research right now.”

Given their potential evolutionary significance, Brookfield said that he was surprised that this study was the first to address the age of the ancient millipedes.

When she was an undergraduate student at UT Austin, Stephanie Suarez developed a method for extracting minerals used in fossil dating. She is now a doctoral student at the University of Houston
. Credit: Chris Watts, University of Houston.

Suarez said a reason could be the difficulty of extracting zircons — a microscopic mineral needed to precisely date the fossils — from the ashy rock sediment in which the fossil was preserved. As an undergraduate researcher at the Jackson School, Suarez developed a technique for separating the zircon grain from this type of sediment. It’s a process that takes practice to master. The zircons are easily flushed away when trying to loosen their grip on the sediment. And once they are successfully released from the surrounding rock, retrieving the zircons involves an eagle-eyed hunt with a pin glued to the tip of a pencil.

“That kind of work trained me for the work that I do here in Houston,” Suarez said. “It’s delicate work.”

As an undergraduate, Suarez used the technique to find that a different millipede specimen, thought to be the oldest bug specimen at the time, was about 14 million years younger than estimated — a discovery that stripped it of the title of oldest bug. Using the same technique, this study passes the distinction along to a new specimen.

The research was funded by the Jackson School, the Max Kade Foundation and DFG Scientific Instrumentation and Information Technology.

Contacts and sources:
Anton Caputo, Jackson School of Geosciences
Monica Kortsha, Jackson School of Geosciences
University of Texas at Austin

Publication: Myriapod divergence times differ between molecular clock and fossil evidence: U/Pb zircon ages of the earliest fossil millipede-bearing sediments and their significance. M. E. Brookfield, E. J. Catlos, S. E. Suarez. Historical Biology, 2020; 1 DOI: 10.1080/08912963.2020.1761351



Yes Your Dog Wants To Save You



What to do. You're a dog. Your owner is trapped in a box and is crying out for help. Are you aware of his despair? If so, can you set him free? And what’s more, do you really want to?

That’s what Joshua Van Bourg and Clive Wynne wanted to know when they gave dogs the chance to rescue their owners.

File:Long Beach Comic & Horror Con 2011 - Krypto, the Super Dog (6301707368).jpg
Credit: The Conmunity - Pop Culture Geek / Wikimedia Commons

Until recently, little research has been done on dogs’ interest in rescuing humans, but that’s what humans have come to expect from their canine companions — a legend dating back to Lassie and updated by the popular Bolt.

“It’s a pervasive legend,” said Van Bourg, a graduate student in Arizona State University’s Department of Psychology.

Simply observing dogs rescuing someone doesn’t tell you much, Van Bourg said. “The difficult challenge is figuring out why they do it.”

So, Van Bourg and Wynne, an ASU professor of psychology and director of the Canine Science Collaboratory at ASU, set up an experiment assessing 60 pet dogs' propensity to rescue their owners. None of the dogs had training in such an endeavor.

In the main test, each owner was confined to a large box equipped with a light-weight door, which the dog could move aside. The owners feigned distress by calling out “help,” or “help me.”


Video courtesy Clive Wynne.

Beforehand, the researchers coached the owners so their cries for help sounded authentic. In addition, owners weren’t allowed to call their dog’s name, which would encourage the dog to act out of obedience, and not out of concern for her owner’s welfare.

“About one-third of the dogs rescued their distressed owner, which doesn’t sound too impressive on its own, but really is impressive when you take a closer look,” Van Bourg said.

That’s because two things are at stake here. One is the dogs’ desire to help their owners, and the other is how well the dogs understood the nature of the help that was needed. Van Bourg and Wynne explored this factor in control tests — tests that were lacking in previous studies.

In one control test, when the dog watched a researcher drop food into the box, only 19 of the 60 dogs opened the box to get the food. More dogs rescued their owners than retrieved food.

“The key here is that without controlling for each dog’s understanding of how to open the box, the proportion of dogs who rescued their owners greatly underestimates the proportion of dogs who wanted to rescue their owners,” Van Bourg said.

“The fact that two-thirds of the dogs didn’t even open the box for food is a pretty strong indication that rescuing requires more than just motivation, there’s something else involved, and that’s the ability component,” Van Bourg said. “If you look at only those 19 dogs that showed us they were able to open the door in the food test, 84% of them rescued their owners. So, most dogs want to rescue you, but they need to know how.”

In another control test, Van Bourg and Wynne looked at what happened when the owner sat inside the box and calmly read aloud from a magazine. What they found was that four fewer dogs, 16 out of 60, opened the box in the reading test than in the distress test.

“A lot of the time it isn’t necessarily about rescuing,” Van Bourg said. “But that doesn’t take anything away from how special dogs really are. Most dogs would run into a burning building just because they can’t stand to be apart from their owners. How sweet is that? And if they know you’re in distress, well, that just ups the ante.”

Canine researcher Clive Wynne and one of his adorable subjects.

Photo by Deanna Dent/ASU Now

The fact that dogs did open the box more often in the distress test than in the reading control test indicated that rescuing could not be explained solely by the dogs wanting to be near their owners.

The researchers also observed each dog’s behavior during the three scenarios. They noted behaviors that can indicate stress, such as whining, walking, barking and yawning.

“During the distress test, the dogs were much more stressed,” Van Bourg said. “When their owner was distressed, they barked more, and they whined more. In fact, there were eight dogs who whined, and they did so during the distress test. Only one other dog whined, and that was for food.”

What’s more, the second and third attempts to open the box during the distress test didn’t make the dogs less stressed than they were during the first attempt. That was in contrast to the reading test, where dogs that have already been exposed to the scenario, were less stressed across repeated tests.

“They became acclimated,” Van Bourg said. “Something about the owner’s distress counteracts this acclimation. There’s something about the owner calling for help that makes the dogs not get calmer with repeated exposure.”

In essence, these individual behaviors are more evidence of “emotional contagion,” the transmission of stress from the owner to the dog, explains Van Bourg, or what humans would call empathy.

“What’s fascinating about this study,” Wynne said, “is that it shows that dogs really care about their people. Even without training, many dogs will try and rescue people who appear to be in distress — and when they fail, we can still see how upset they are. The results from the control tests indicate that dogs who fail to rescue their people are unable to understand what to do — it’s not that they don’t care about their people.

“Next, we want to explore whether the dogs that rescue do so to get close to their people, or whether they would still open the box even if that did not give them the opportunity to come together with their humans,” Wynne added.

The study, “Pet dogs (Canis lupus familiaris) release their trapped and distressed owners: Individual variation and evidence of emotional contagion was published last month,” was published online last month in the journal PLOS.



Contacts and sources:
Robin Tricoles
Arizona State University
Publication: Pet dogs (Canis lupus familiaris) release their trapped and distressed owners: Individual variation and evidence of emotional contagion. Joshua Van Bourg, Jordan Elizabeth Patterson, Clive D. L. Wynne. PLOS ONE, 2020; 15 (4): e0231742 DOI: 10.1371/journal.pone.0231742



Friday, May 29, 2020

In Planet Formation, It's Location, Location, Location



Astronomers using NASA's Hubble Space Telescope are finding that planets have a tough time forming in the rough-and-tumble central region of the massive, crowded star cluster Westerlund 2. Located 20,000 light-years away, Westerlund 2 is a unique laboratory to study stellar evolutionary processes because it's relatively nearby, quite young, and contains a large stellar population.

The brilliant tapestry of young stars flaring to life resembles a glittering fireworks display in this Hubble Space Telescope image. The sparkling centerpiece of this fireworks show is a giant cluster of thousands of stars called Westerlund 2. The cluster resides in a raucous stellar breeding ground known as Gum 29, located 20,000 light-years away from Earth in the constellation Carina. Hubble's Wide Field Camera 3 pierced through the dusty veil shrouding the stellar nursery in near-infrared light, giving astronomers a clear view of the nebula and the dense concentration of stars in the central cluster. The cluster measures between six light-years and 13 light-years across.

Credits: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI) and the Westerlund 2 Science Team

A three-year Hubble study of stars in Westerlund 2 revealed that the precursors to planet-forming disks encircling stars near the cluster's center are mysteriously devoid of large, dense clouds of dust that in a few million years could become planets.

However, the observations show that stars on the cluster's periphery do have the immense planet-forming dust clouds embedded in their disks. Researchers think our solar system followed this recipe when it formed 4.6 billion years ago.

So why do some stars in Westerlund 2 have a difficult time forming planets while others do not? It seems that planet formation depends on location, location, location. The most massive and brightest stars in the cluster congregate in the core, which is verified by observations of other star-forming regions. The cluster's center contains at least 30 extremely massive stars, some weighing up to 80 times the mass of the Sun. Their blistering ultraviolet radiation and hurricane-like stellar winds of charged particles blowtorch disks around neighboring lower-mass stars, dispersing the giant dust clouds.

"Basically, if you have monster stars, their energy is going to alter the properties of the disks around nearby, less massive stars," explained Elena Sabbi, of the Space Telescope Science Institute in Baltimore and lead researcher of the Hubble study. "You may still have a disk, but the stars change the composition of the dust in the disks, so it's harder to create stable structures that will eventually lead to planets. We think the dust either evaporates away in 1 million years, or it changes in composition and size so dramatically that planets don't have the building blocks to form."

The Hubble observations represent the first time that astronomers analyzed an extremely dense star cluster to study which environments are favorable to planet formation. Scientists, however, are still debating whether bulky stars are born in the center or whether they migrate there. Westerlund 2 already has massive stars in its core, even though it is a comparatively young, 2-million-year-old system.

Using Hubble's Wide Field Camera 3, the researchers found that of the nearly 5,000 stars in Westerlund 2 with masses between 0.1 to 5 times the Sun's mass, 1,500 of them show fluctuations in their light as the stars accrete material from their disks. Orbiting material clumped within the disk would temporarily block some of the starlight, causing brightness fluctuations.

However, Hubble detected the signature of such orbiting material only around stars outside the cluster's packed central region. The telescope witnessed large drops in brightness for as much as 10 to 20 days around 5% of the stars before they returned to normal brightness. They did not detect these dips in brightness in stars residing within four light-years of the center. These fluctuations could be caused by large clumps of dust passing in front of the star. The clumps would be in a disk tilted nearly edge-on to the view from Earth. "We think they are planetesimals or structures in formation," Sabbi explained. "These could be the seeds that eventually lead to planets in more evolved systems. These are the systems we don't see close to very massive stars. We see them only in systems outside the center."

Thanks to Hubble, astronomers can now see how stars are accreting in environments that are like the early universe, where clusters were dominated by monster stars. So far, the best known nearby stellar environment that contains massive stars is the starbirth region in the Orion Nebula. However, Westerlund 2 is a richer target because of its larger stellar population.

"Hubble's observations of Westerlund 2 give us a much better sense of how stars of different masses change over time, and how powerful winds and radiation from very massive stars affect nearby lower-mass stars and their disks," Sabbi said. "We see, for example, that lower-mass stars, like our Sun, that are near extremely massive stars in the cluster still have disks and still can accrete material as they grow. But the structure of their disks (and thus their planet-forming capability) seems to be very different from that of disks around stars forming in a calmer environment farther away from the cluster core. This information is important for building models of planet formation and stellar evolution."

This cluster will be an excellent laboratory for follow-up observations with NASA's upcoming James Webb Space Telescope, an infrared observatory. Hubble has helped astronomers identify the stars that have possible planetary structures. With Webb, researchers can study which disks around stars are not accreting material and which disks still have material that could build up into planets. This information on 1,500 stars will allow astronomers to map a path on how star systems grow and evolve. Webb also can study the chemistry of the disks in different evolutionary phases and watch how they change, and help astronomers determine what influence environment plays in their evolution.

NASA's Nancy Grace Roman Space Telescope, another planned infrared observatory, will be able to perform Sabbi's study on a much larger area.​ Westerlund 2 is just a small slice of an immense star-formation region. These vast regions contain clusters of stars with different ages and different densities. Astronomers could use Roman Space Telescope observations to start to build up statistics on how a star's characteristics, like its mass or outflows, affect its own evolution or the nature of stars that form nearby. The observations could also provide more information on how planets form in tough environments.

Sabbi's team's results appeared in The Astrophysical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.


Contacts and sources:
Claire Andreoli
NASA's Goddard Space Flight Center, Greenbelt, Md.

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore

Elena Sabbi
Space Telescope Science Institute


Publication: Time-domain Study of the Young Massive Cluster Westerlund 2 with the Hubble Space Telescope The Astrophysical Journal, Volume 891, Number 2
http://dx.doi.org/10.3847/1538-4357/ab7372






New Earth Found Orbiting Proxima Centauri, Our Closet Neighbor Star

The existence of a planet the size of Earth around the closest star in the solar system, Proxima Centauri, has been confirmed by an international team of scientists including researchers from the University of Geneva (UNIGE). The results, which you can read all about in the journal Astronomy & Astrophysics, reveal that the planet in question, Proxima b, has a mass of 1.17 earth masses and is located in the habitable zone of its star, which it orbits in 11.2 days. 


This artist's impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System.

Credit: © ESO/M. Kornmesser

This breakthrough has been possible thanks to radial velocity measurements of unprecedented precision using ESPRESSO, the Swiss-manufactured spectrograph - the most accurate currently in operation - which is installed on the Very Large Telescope in Chile. Proxima b was first detected four years ago by means of an older spectrograph, HARPS - also developed by the Geneva-based team - which measured a low disturbance in the star's speed, suggesting the presence of a companion.

The ESPRESSO spectrograph has performed radial velocity measurements on the star Proxima Centauri, which is only 4.2 light-years from the Sun, with an accuracy of 30 centimetres a second (cm/s) or about three times more precise than that obtained with HARPS, the same type of instrument but from the previous generation.

"We were already very happy with the performance of HARPS, which has been responsible for discovering hundreds of exoplanets over the last 17 years", begins Francesco Pepe, a professor in the Astronomy Department in UNIGE's Faculty of Science and the man in charge of ESPRESSO. "We're really pleased that ESPRESSO can produce even better measurements, and it's gratifying and just reward for the teamwork lasting nearly 10 years."

Shining brightly in this Hubble image is our closest stellar neighbour: Proxima Centauri. Proxima Centauri lies in the constellation of Centaurus (The Centaur), just over four light-years from Earth. Although it looks bright through the eye of Hubble, as you might expect from the nearest star to the Solar System, Proxima Centauri is not visible to the naked eye.
Credit: Hubble Space Telescope/ESA

Alejandro Suarez Mascareño, the article's main author, adds: "Confirming the existence of Proxima b was an important task, and it's one of the most interesting planets known in the solar neighbourhood."

The measurements performed by ESPRESSO have clarified that the minimum mass of Proxima b is 1.17 earth masses (the previous estimate was 1.3) and that it orbits around its star in only 11.2 days.

Artist's impression of the exoplanet Proxima Centauri b shown as of a arid (but not completely water-free) rocky Super-Earth. This appearance is one of several possible outcomes of current theories regarding the development of this exoplanet, while the actual look and structure of the planet is known in no ways at this time. Proxima Centauri b is the closest exoplanet to the Sun and also the closest potentially habitable exoplanet as well. It orbits Proxima Centauri, a red dwarf with a surface temperature of 3040 K (thus hotter than light bulbs and therefore whiter, as depicted here). The Alpha Centauri binary system is shown in the background.

Credit: ESO/M. Kornmesser

"ESPRESSO has made it possible to measure the mass of the planet with a precision of over one-tenth of the mass of Earth", says Michel Mayor, winner of the Nobel Prize for Physics in 2019, honorary professor in the Faculty of Science and the 'architect' of all ESPRESSO-type instruments. "It's completely unheard of."

And what about life in all this?

Although Proxima b is about 20 times closer to its star than the Earth is to the Sun, it receives comparable energy, so that its surface temperature could mean that water (if there is any) is in liquid form in places and might, therefore, harbour life.

Having said that, although Proxima b is an ideal candidate for biomarker research, there is still a long way to go before we can suggest that life has been able to develop on its surface. In fact, the Proxima star is an active red dwarf that bombards its planet with X rays, receiving about 400 times more than the Earth.

"Is there an atmosphere that protects the planet from these deadly rays?" asks Christophe Lovis, a researcher in UNIGE's Astronomy Department and responsible for ESPRESSO's scientific performance and data processing. "And if this atmosphere exists, does it contain the chemical elements that promote the development of life (oxygen, for example)? How long have these favourable conditions existed? We're going to tackle all these questions, especially with the help of future instruments like the RISTRETTO spectrometer, which we're going to build specially to detect the light emitted by Proxima b, and HIRES, which will be installed on the future ELT 39 m giant telescope that the European Southern Observatory (ESO) is building in Chile."

Surprise: is there a second planet?

In the meantime, the precision of the measurements made by ESPRESSO could result in another surprise. The team has found evidence of a second signal in the data, without being able to establish the definitive cause behind it. "If the signal was planetary in origin, this potential other planet accompanying Proxima b would have a mass less than one third of the mass of the Earth. It would then be the smallest planet ever measured using the radial velocity method", adds Professor Pepe.

It should be noted that ESPRESSO, which became operational in 2017, is in its infancy and these initial results are already opening up undreamt of opportunities. The road has been travelled at breakneck pace since the first extrasolar planet was discovered by Michel Mayor and Didier Queloz, both from UNIGE's Astronomy Department. In 1995, the 51Peg b gas giant planet was detected using the ELODIE spectrograph with an accuracy of 10 meters per second (m/s). Today ESPRESSO, with its 30 cm/s (and soon 10 after the latest adjustments) will perhaps make it possible to explore worlds that remind us of the Earth.



Contacts and sources:
Francesco Pepe
University of Geneva (UNIGE)






750-715 BCE: Cannabis and Frankincense Used at "Holy of Holies" Shrine in Israel


Analysis of the material on two Iron Age altars discovered at the entrance to the "holy of holies" of a shrine at Tel Arad in the Beer-sheba Valley, Israel, were found to contain Cannabis and Frankincense, according to new article in the journal, Tel Aviv.

Past excavations revealed two superimposed fortresses, dated to the 9th to early 6th centuries BCE, which guarded the southern border of biblical Judah. Highly important Iron Age finds were unearthed, including a well-preserved shrine that was dated to ca. 750-715 BCE.

Front view of the shrine at Arad, rebuilt in the Israel Museum. The top-down view of the altars: on where you can see the black residue of cannabis and frankincense

Credit: (Collection of the Israel Antiquities Authority, Photo © The Israel Museum, by Laura Lachman

Two limestone altars (the smaller altar is 40 cm high and about 20 × 20 cm at the top; the larger is about 50 cm high and 30 × 30 cm at the top) were found lying at the entrance to the "holy of holies" of the shrine.

Evidently, they had played an important role in the cult practices of the shrine. An unidentified black solidified organic material was preserved on the altars' surfaces. Past analysis of these materials failed to identify their content and this dark material was recently submitted to organic residue analysis by modern methods.

The study reveals that on the smaller altar cannabis had been mixed with animal dung to facilitate heating, while the larger altar contained traces of frankincense that was mixed with animal fat to promote evaporation.

These unique findings shed new light on cult practices in biblical Judah, suggesting cannabis was used here as a deliberate psychoactive, to stimulate ecstasy as part of cultic ceremonies.

Lead author Eran Arie from The Israel Museum in Jerusalem commented, "This is the first time that cannabis has been identified in the Ancient Near East; Its use in the shrine must have played a central role in the cultic rituals performed there."

Frankincense comes from Arabia. Therefore, the presence of frankincense at Arad indicates the participation of Judah in the south Arabian trade even before the patronage and encouragement of the Assyrian empire. Arad provides the earliest evidence for frankincense in a clear cultic context. Frankincense is mentioned as a component of the incense that was burned in the Temple of Jerusalem for its pleasant aroma.

The "fortress mound" of Tel Arad in the Beer-sheba Valley in southern Israel was excavated over 50 years ago under the direction of the late TAU Professor Yohanan Aharoni.



Contacts and sources:
Krystina SihduEran Arie, The Israel Museum, Jerusalem
Dvory Namdar, Volcani Center of Agricultural Research
Krystina Sihdu, Taylor and Francis





Thursday, May 28, 2020

Erosion of Ozone Layer Responsible for Mass Extinction Event 360 Million Years Ago

Researchers at the University of Southampton have shown that an extinction event 360 million years ago, that killed much of the Earth’s plant and freshwater aquatic life, was caused by a brief breakdown of the ozone layer that shields the Earth from damaging ultraviolet (UV) radiation. This is a newly discovered extinction mechanism with profound implications for our warming world today.

Researchers at the University of Southampton have shown that an extinction event 360 million years ago, that killed much of the Earth’s plant and freshwater aquatic life, was caused by a brief breakdown of the ozone layer that shields the Earth from damaging ultraviolet (UV) radiation. This is a newly discovered extinction mechanism with profound implications for our warming world today.

Marshall
Credit:

There have been a number of mass extinction in the geological past. Only one was caused by an asteroid hitting the Earth, which was 66 million years ago when the dinosaurs became extinct. Three of the others, including the end Permian Great Dying, 252 million years ago, were caused by huge continental scale volcanic eruptions that destabilised the Earth’s atmospheres and oceans.

Now, scientists have found evidence showing it was high levels of UV radiation which collapsed forest ecosystems and killed off many species of fish and tetrapods (our four limbed ancestors) at the end of the Devonian geological period, 359 million years ago. This damaging burst of UV radiation occurred as part of one of the Earth’s climate cycles, rather than being caused by a huge volcanic eruption.

Credit:

The ozone collapse occurred as the climate rapidly warmed following an intense ice age and the researchers suggest that the Earth today could reach comparable temperatures, possibly triggering a similar event. Their findings are published in the journal Science Advances.

The team collected rock samples during expeditions to mountainous polar-regions in East Greenland, which once formed a huge ancient lake bed in the arid interior of the Old Red Sandstone Continent, made up of Europe and North America. This lake was situated in the Earth’s southern hemisphere and would have been similar in nature to modern day Lake Chad on the edge of the Sahara Desert.

Other rocks were collected from the Andean Mountains above Lake Titicaca in Bolivia. These South American samples were from the southern continent of Gondwana, which was closer to the Devonian South Pole. They held clues as to what was happening at the edge of the melting Devonian ice sheet, allowing a comparison between the extinction event close to the pole and close to the equator.


Back in the lab, the rocks were dissolved in hydrofluoric acid, releasing microscopic plant spores (like pollen, but from fern like plants that didn’t have seeds or flowers) which had lain preserved for hundreds of millions of years. On microscopic examination, the scientists found many of the spores had bizarrely formed spines on their surface – a response to UV radiation damaging their DNA. Also, many spores had dark pigmented walls, thought to be a kind of protective ‘tan’, due to increased and damaging UV levels.

The scientists concluded that, during a time of rapid global warming, the ozone layer collapsed for a short period, exposing life on Earth to harmful levels of UV radiation and triggering a mass extinction event on land and in shallow water at the Devonian-Carboniferous boundary.

Following melting of the ice sheets, the climate was very warm, with the increased heat above continents pushing more naturally generated ozone destroying chemicals into the upper atmosphere. This let in high levels of UV-B radiation for several thousand years.

Lead researcher Professor John Marshall, of the University of Southampton’s School of Ocean and Earth Science, who is a National Geographic Explorer, comments: “Our ozone shield vanished for a short time in this ancient period, coinciding with a brief and quick warming of the Earth. Our ozone layer is naturally in a state of flux – constantly being created and lost – and we have shown this happened in the past too, without a catalyst such as a continental scale volcanic eruption.”

During the extinction, plants selectively survived, but were enormously disrupted as the forest ecosystem collapsed. The dominant group of armoured fish became extinct. Those that survived – sharks and bony fish – remain to this day the dominant fish in our ecosystems.

These extinctions came at a key time for the evolution of our own ancestors, the tetrapods. These early tetrapods are fish that evolved to have limbs rather than fins, but still mostly lived in water. Their limbs possessed many fingers and toes. The extinction reset the direction of their evolution with the post-extinction survivors being terrestrial and with the number of fingers and toes reduced to five.

Professor Marshall says his team’s findings have startling implications for life on Earth today: “Current estimates suggest we will reach similar global temperatures to those of 360 million years ago, with the possibility that a similar collapse of the ozone layer could occur again, exposing surface and shallow sea life to deadly radiation. This would move us from the current state of climate change, to a climate emergency.”

The remote locations visited in East Greenland are very difficult to access, with travel involving light aircraft capable of landing directly on the tundra. Transport within the vast field area was by inflatable boats equipped with outboard motors, all of which had to fit in the small aircraft.

All field logistics was organised by CASP, an independent charitable trust based in Cambridge specialising in remote geological fieldwork. Mike Curtis, Managing Director of CASP says: “We have a history of assisting research geologists such as John Marshall and colleagues to access remote field areas and we are particularly pleased that their research has proved to have such potentially profound implications.”



Contacts and sources:
University of Southampton

Publication: UV-B radiation was the Devonian-Carboniferous boundary terrestrial extinction kill mechanism.
John E. A. Marshall, Jon Lakin, Ian Troth, Sarah M. Wallace-Johnson. Science Advances, 2020; 6 (22): eaba0768 DOI: 10.1126/sciadv.aba0768




Women with Neanderthal Gene Give Birth to More Children



One in three women in Europe inherited the receptor for progesterone from Neanderthals - a gene variant associated with increased fertility, fewer bleedings during early pregnancy and fewer miscarriages. This is according to a study published in Molecular Biology and Evolution by researchers at the Max Planck Institute for Evolutionary Anthropology in Germany and Karolinska Institutet in Sweden.

"The progesterone receptor is an example of how favorable genetic variants that were introduced into modern humans by mixing with Neanderthals can have effects in people living today," says Hugo Zeberg, researcher at the Department of Neuroscience at Karolinska Institutet and the Max Planck Institute for Evolutionary Anthropology, who performed the study with colleagues Janet Kelso and Svante Pääbo.

Models of male and female Homo neanderthalensis in the Neanderthal Museum, Mettmann, Germany
File:Neandertala homo, modelo en Neand-muzeo.JPG
Credit: UNiesert / Wikimedia Commons

Progesterone is a hormone, which plays an important role in the menstrual cycle and in pregnancy. Analyses of biobank data from more than 450,000 participants - among them 244,000 women - show that almost one in three women in Europe have inherited the progesterone receptor from Neandertals. 29 percent carry one copy of the Neanderthal receptor and three percent have two copies.

"The proportion of women who inherited this gene is about ten times greater than for most Neanderthal gene variants," says Hugo Zeberg. "These findings suggest that the Neanderthal variant of the receptor has a favorable effect on fertility."

The study shows that women who carry the Neanderthal variant of the receptor tend to have fewer bleedings during early pregnancy, fewer miscarriages, and give birth to more children. Molecular analyses revealed that these women produce more progesterone receptors in their cells, which may lead to increased sensitivity to progesterone and protection against early miscarriages and bleeding.


Contacts and sources:
arolinska Institutet

Publication: The Genomic History of the Bronze Age Southern Levant. Lily Agranat-Tamir, Shamam Waldman, Mario A.S. Martin, David Gokhman, Nadav Mishol, Tzilla Eshel, Olivia Cheronet, Nadin Rohland, Swapan Mallick, Nicole Adamski, Ann Marie Lawson, Matthew Mah, Megan Michel, Jonas Oppenheimer, Kristin Stewardson, Francesca Candilio, Denise Keating, Beatriz Gamarra, Shay Tzur, Mario Novak, Rachel Kalisher, Shlomit Bechar, Vered Eshed, Douglas J. Kennett, Marina Faerman, Naama Yahalom-Mack, Janet M. Monge, Yehuda Govrin, Yigal Erel, Benjamin Yakir, Ron Pinhasi, Shai Carmi, Israel Finkelstein, Liran Carmel, David Reich. Cell, 2020; 181 (5): 1146 DOI: 10.1016/j.cell.2020.04.024



The Lancet: First Human Trial of COVID-19 Vaccine Finds It Is Safe and Induces Rapid Immune Response



The first COVID-19 vaccine to reach phase 1 clinical trial has been found to be safe, well-tolerated, and able to generate an immune response against SARS-CoV-2 in humans, according to new research published in The Lancet. The open-label trial in 108 healthy adults demonstrates promising results after 28 days--the final results will be evaluated in six months [1]. Further trials are needed to tell whether the immune response it elicits effectively protects against SARS-CoV-2 infection.

Micrograph of Covid-19 Virus
Novel coronavirus structure reveals targets for vaccines and ...
Credit: NIH


"These results represent an important milestone. The trial demonstrates that a single dose of the new adenovirus type 5 vectored COVID-19 (Ad5-nCoV) vaccine produces virus-specific antibodies and T cells in 14 days, making it a potential candidate for further investigation", says Professor Wei Chen from the Beijing Institute of Biotechnology in Beijing, China, who is responsible for the study. "However, these results should be interpreted cautiously. The challenges in the development of a COVD-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19. This result shows a promising vision for the development of COVID-19 vaccines, but we are still a long way from this vaccine being available to all." [2]

The creation of an effective vaccine is seen as the long-term solution to controlling the COVID-19 pandemic. Currently, there are more than 100 candidate COVID-19 vaccines in development worldwide.

The new Ad5 vectored COVID-19 vaccine evaluated in this trial is the first to be tested in humans. It uses a weakened common cold virus (adenovirus, which infects human cells readily but is incapable of causing disease) to deliver genetic material that codes for the SARS-CoV-2 spike protein to the cells. These cells then produce the spike protein, and travel to the lymph nodes where the immune system creates antibodies that will recognize that spike protein and fight off the coronavirus.

The trial assessed the safety and ability to generate an immune response of different dosages of the new Ad5-nCoV vaccine in 108 healthy adults between the ages of 18 and 60 years who did not have SARS-CoV-2 infection. Volunteers were enrolled from one site in Wuhan, China, and assigned to receive either a single intramuscular injection of the new Ad5 vaccine at a low dose (5 × 1010 viral particles/0·5ml, 36 adults), middle dose (1×1011 viral particles/1.0ml, 36 adults), or high dose (1.5 x 1011 viral particles/1.5ml, 36 adults).

The researchers tested the volunteers' blood at regular intervals following vaccination to see whether the vaccine stimulated both arms of the immune system: the body's 'humoral response' (the part of the immune system that produces neutralising antibodies which can fight infection and could offer a level of immunity), and the body's cell-mediated arm (which depends on a group of T cells, rather than antibodies, to fight the virus). The ideal vaccine might generate both antibody and T cell responses to defend against SARS-CoV-2.

The vaccine candidate was well tolerated at all doses with no serious adverse events reported within 28 days of vaccination. Most adverse events were mild or moderate, with 83% (30/36) of those receiving low and middle doses of the vaccine and 75% (27/36) in the high dose group reporting at least one adverse reaction within 7 days of vaccination.

The most common adverse reactions were mild pain at the injection site reported in over half (54%, 58/108) of vaccine recipients, fever (46%, 50/108), fatigue (44%, 47/108), headache (39%, 42/108), and muscle pain (17%, 18/108). One participant given the higher dose vaccine reported severe fever along with severe symptoms of fatigue, shortness of breath, and muscle pain--however these adverse reactions persisted for less than 48 hours.

Within two weeks of vaccination, all dose levels of the vaccine triggered some level of immune response in the form of binding antibodies (that can bind to the coronavirus but do not necessarily attack it - low-dose group 16/36, 44%; medium dose 18/36, 50%; high dose 22/36, 61%), and some participants had detectable neutralising antibodies against SARS-CoV-2 (low-dose group 10/36, 28%; medium dose 11/36, 31%; high dose 15/36, 42%).

After 28 days, most participants had a four-fold increase in binding antibodies (35/36, 97% low-dose group; 34/36 (94%) middle-dose group, and 36/36, 100% in high-dose group), and half (18/36) of participants in the low- and middle-dose groups and three-quarters (27/36) of those in the high-dose group showed neutralising antibodies against SARS-CoV-2.

Importantly, the Ad5-nCoV vaccine also stimulated a rapid T cell response in the majority of volunteers, which was greater in those given the higher and middle doses of vaccine, with levels peaking at 14 days after vaccination (low-dose group (30/36; 83.3%), medium (35/36, 97.2%), and high-dose group (35/36, 97.2%) at 14 days).

Further analyses showed that 28 days after vaccination, the majority of recipients showed either a positive T cell response or had detectable neutralising antibodies against SARS-CoV-2 (low-dose group 28/36, 78%; medium-dose group 33/36, 92%; high-dose group 36/36, 100%).

However, the authors note that both the antibody and T-cell response could be reduced by high pre-existing immunity to adenovirus type 5 (the common cold virus vector/carrier)--in the study, 44%-56% of participants in the trial had high pre-existing immunity to adenovirus type 5, and had a less positive antibody and T-cell response to the vaccine.

"Our study found that pre-existing Ad5 immunity could slow down the rapid immune responses to SARS-CoV-2 and also lower the peaking level of the responses. Moreover, high pre-existing Ad5 immunity may also have a negative impact on the persistence of the vaccine-elicited immune responses", say Professor Feng-Cai Zhu from Jiangsu Provincial Center for Disease Control and Prevention in China who led the study.

The authors note that the main limitations of the trial are its small sample size, relatively short duration, and lack of randomised control group, which limits the ability to pick up rarer adverse reactions to the vaccine or provide robust evidence for its ability to generate an immune reaction. Further research will be needed before this trial vaccine becomes available to all.

A randomised, double-blinded, placebo-controlled phase 2 trial of the Ad5-nCoV vaccine has been initiated in Wuhan to determine whether the results can be replicated, and if there are any adverse events up to 6 months after vaccination, in 500 healthy adults--250 volunteers given a middle dose, 125 given a low dose, and 125 given a placebo as a control. For the first time, this will include participants over 60 years old, an important target population for the vaccine.

The study was funded by National Key R&D Program of China, National Science and Technology Major Project, and CanSino Biologic. It was conducted by researchers from Beijing Institute of Biotechnology, Beijing, China; Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, China; National Institute for Food and Drug Control, Beijing, China; Hubei Provincial Center for Disease Control and Prevention, Wuhan, China; State Key Laboratory of Pathogen and Biosecurity, Beijing, China; CanSino Biologics, Tianjin, China; Huazhong University of Science and Technology, Wuhan, China; and Shanghai Canming Medical Technology, Shanghai, China.

The labels have been added as part of a project run by the Academy of Medical Sciences seeking to improve the communication of evidence. For more information, please see: http://www.sciencemediacentre.org/wp-content/uploads/2018/01/AMS-press-release-labelling-system-GUIDANCE.pd

Contacts and sources:
Jessica Kleyn
The Lancet




Wednesday, May 27, 2020

New Class of Cosmic Explosions Discovered

Astronomers have found two objects that, added to a strange object discovered in 2018, constitute a new class of cosmic explosions. The new type of explosion shares some characteristics with supernova explosions of massive stars and with the explosions that generate gamma-ray bursts (GRBs), but still has distinctive differences from each.

Artist's conception illustrates the differences in phenomena resulting from an "ordinary" core-collapse supernova explosion, an explosion creating a gamma-ray burst, and one creating a Fast Blue Optical Transient. Details in text.

Credit: Bill Saxton, NRAO/AUI/NSF


The saga began in June of 2018 when astronomers saw a cosmic blast with surprising characteristics and behavior. The object, dubbed AT2018cow (“The Cow”), drew worldwide attention from scientists and was studied extensively. While it shared some characteristics with supernova explosions, it differed in important aspects, particularly its unusual initial brightness and how rapidly it brightened and faded in just a few days.

In the meantime, two additional blasts — one from 2016 and one from 2018 — also showed unusual characteristics and were being observed and analyzed. The two new explosions are called CSS161010 (short for CRTS CSS161010 J045834-081803), in a galaxy about 500 million light-years from Earth, and ZTF18abvkwla (“The Koala”), in a galaxy about 3.4 billion light-years distant. Both were discovered by automated sky surveys (Catalina Real-time Transient Survey, All-Sky Automated Survey for Supernovae, and Zwicky Transient Facility) using visible-light telescopes to scan large areas of sky nightly.

Two teams of astronomers followed up those discoveries by observing the objects with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA). Both teams also used the Giant Metrewave Radio Telescope in India and the team studying CSS161010 used NASA’s Chandra X-ray Observatory. Both objects gave the observers surprises.

Anna Ho, of Caltech, lead author of the study on ZTF18abvkwla, immediately noted that the object’s radio emission was as bright as that from a gamma-ray burst. “When I reduced the data, I thought I had made a mistake,” she said.

Deanne Coppejans, of Northwestern University, led the study on CSS161010, which found that the object had launched an “unexpected” amount of material into interstellar space at more than half the speed of light. Her Northwestern co-author Raffaella Margutti, said, “It took almost two years to figure out what we were looking at just because it was so unusual.”

In both cases, the follow-up observations indicated that the objects shared features in common with AT2018cow. The scientists concluded that these events, called Fast Blue Optical Transients (FBOTs), represent, along with AT2018cow, a type of stellar explosion significantly different from others. The scientists reported their findings in papers in the Astrophysical Journal and the Astrophysical Journal Letters.

Artist's conception illustrates the phenomena that make up the new class of cosmic explosions called Fast Blue Optical Transients.
Credit: Bill Saxton, NRAO/AUI/NSF


FBOTs probably begin, the astronomers said, the same way as certain supernovae and gamma-ray bursts — when a star much more massive than the Sun explodes at the end of its “normal” atomic fusion-powered life. The differences show up in the aftermath of the initial explosion.

In the “ordinary” supernova of this type, called a core-collapse supernova, the explosion sends a spherical blast wave of material into interstellar space. If, in addition to this, a rotating disk of material briefly forms around the neutron star or black hole left after the explosion and propels narrow jets of material at nearly the speed of light outward in opposite directions, these jets can produce narrow beams of gamma rays, causing a gamma-ray burst.

The rotating disk, called an accretion disk, and the jets it produces, are called an “engine” by astronomers.

FBOTs, the astronomers concluded, also have such an engine. In their case, unlike in gamma-ray bursts, it is enshrouded by thick material. That material probably was shed by the star just before it exploded, and may have been pulled from it by a binary companion.

When the thick material near the star is struck by the blast wave, it causes the bright visible-light burst soon after the explosion that initially made these objects appear so unusual. That bright burst also is why astronomers call these blasts “fast blue optical transients.” This is one of the characteristics that distinguished them from ordinary supernovae.

As the blastwave from the explosion collides with the material around the star as it travels outwards, it produces radio emission. This very bright emission was the important clue that proved that the explosion was powered by an engine.

The shroud of dense material “means that the progenitor star is different from those leading to gamma-ray bursts,” Ho said. The astronomers said that in the Cow and in CSS161010, the dense material included hydrogen, something never seen in in gamma-ray bursts.

Using the W.M. Keck Observatory, the astronomers found that both CSS 161010 and ZTF18abvkwla, like the Cow, are in small, dwarf galaxies. Coppejans said that the dwarf galaxy properties “might allow some very rare evolutionary paths of stars” that lead to these distinctive explosions.

Although a common element of the FBOTs is that all three have a ‘central engine,’ the astronomers caution that the engine also could be the result of stars being shredded by black holes, though they consider supernova-type explosions to be the more likely candidate.

“Observations of more FBOTs and their environments will answer this question,” Margutti said.

To do that, the scientists say they will need to use telescopes covering a wide range of wavelengths, as they have done with the first three objects. “While FBOTs have proven rarer and harder to find than some of us were hoping, in the radio band they’re also much more luminous than we’d guessed, allowing us to provide quite comprehensive data even on events that are far away,” said Daniel Perley, of the Liverpool John Moores University.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The study of CSS161010 was partially supported by the Heising-Simons Foundation, NASA, and the National Science Foundation.



Contacts and sources:
Dave Finley
National Radio Astronomy Observatory


Publications:

A Mildly Relativistic Outflow from the Energetic, Fast-rising Blue Optical Transient CSS161010 in a Dwarf Galaxy. D. L. Coppejans, R. Margutti, G. Terreran, A. J. Nayana, E. R. Coughlin, T. Laskar, K. D. Alexander, M. Bietenholz, D. Caprioli, P. Chandra, M. R. Drout, D. Frederiks, C. Frohmaier, K. H Hurley, C. S. Kochanek, M. MacLeod, A. Meisner, P. E. Nugent, A. Ridnaia, D. J. Sand, D. Svinkin, C. Ward, S. Yang, A. Baldeschi, I. V. Chilingarian, Y. Dong, C. Esquivia, W. Fong, C. Guidorzi, P. Lundqvist, D. Milisavljevic, K. Paterson, D. E. Reichart, B. Shappee, M. C. Stroh, S. Valenti, B. A. Zauderer, B. Zhang. The Astrophysical Journal Letters, 2020; 895 (1): L23 DOI: 10.3847/2041-8213/ab8cc7


The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at z = 0.27. Anna Y. Q. Ho, Daniel A. Perley, S. R. Kulkarni, Dillon Z. J. Dong, Kishalay De, Poonam Chandra, Igor Andreoni, Eric C. Bellm, Kevin B. Burdge, Michael Coughlin, Richard Dekany, Michael Feeney, Dmitry D. Frederiks, Christoffer Fremling, V. Zach Golkhou, Matthew J. Graham, David Hale, George Helou, Assaf Horesh, Mansi M. Kasliwal, Russ R. Laher, Frank J. Masci, A. A. Miller, Michael Porter, Anna Ridnaia, Ben Rusholme, David L. Shupe, Maayane T. Soumagnac, Dmitry S. Svinkin. The Astrophysical Journal, 2020; 895 (1): 49 DOI: 10.3847/1538-4357/ab8bcf


The Dinosaur Killing Asteroid Hit Earth at Deadliest Possible Angle



New simulations from Imperial College London have revealed the asteroid that doomed the dinosaurs struck Earth at the ‘deadliest possible’ angle.

The simulations show that the asteroid hit Earth at an angle of about 60 degrees, which maximised the amount of climate-changing gases thrust into the upper atmosphere.

Such a strike likely unleashed billions of tonnes of sulphur, blocking the sun and triggering the nuclear winter that killed the dinosaurs and 75 per cent of life on Earth 66 million years ago.
Original artwork depicting the moment the asteroid struck in present-day Mexico. Shown are the asteroid in the background and silhouetted dinosaurs in the foreground.
 Credit: Chase Stone

Drawn from a combination of 3D numerical impact simulations and geophysical data from the site of the impact, the new models are the first ever fully 3D simulations to reproduce the whole event – from the initial impact to the moment the final crater, now known as Chicxulub, was formed.

Lead researcher Professor Gareth Collins, of Imperial’s Department of Earth Science and Engineering, said: “For the dinosaurs, the worst-case scenario is exactly what happened. The asteroid strike unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of the dinosaurs. This was likely worsened by the fact that it struck at one of the deadliest possible angles.

“Our simulations provide compelling evidence that the asteroid struck at a steep angle, perhaps 60 degrees above the horizon, and approached its target from the north-east. We know that this was among the worst-case scenarios for the lethality on impact, because it put more hazardous debris into the upper atmosphere and scattered it everywhere – the very thing that led to a nuclear winter.”

The results are published in Nature Communications. The simulations, which used a 17-km diameter asteroid with a density of 2630 kgm3 and a speed of 12 km/s, were performed on the Science and Technology Facilities Council (STFC) DiRAC High Performance Computing Facility.


Crater creation

Gravity map showing asymmetries in the Chicxulub crater reflect the asteroid's impact angle

Credit: Gareth Collins/Imperial College London

The upper layers of earth around the Chicxulub crater in present-day Mexico contain high amounts of water as well as porous carbonate and evaporite rocks. When heated and disturbed by the impact, these rocks would have decomposed, flinging vast amounts of carbon dioxide, sulphur and water vapour into the atmosphere.

The sulphur would have been particularly hazardous as it rapidly forms aerosols - tiny particles that would have blocked the sun’s rays, halting photosynthesis in plants and rapidly cooling the climate. This eventually contributed to the mass extinction event that killed 75 per cent of life on Earth.

The team of researchers from Imperial, the University of Freiburg, and the University of Texas at Austin, examined the shape and subsurface structure of the crater using geophysical data to feed into the simulations that helped diagnose the impact angle and direction. Their analysis was also informed by recent results from drilling into the 200 km-wide crater, which brought up rocks containing evidence of the extreme forces generated by the impact.


Peak performance

Pivotal to diagnosing the angle and direction of impact was the relationship between the centre of the crater, the centre of the peak ring - a ring of mountains made of heavily fractured rock inside the crater rim - and the centre of dense uplifted mantle rocks, some 30 km beneath the crater.

At Chicxulub, these centres are aligned in a southwest-northeast direction, with the crater centre in between the peak-ring and mantle-uplift centres. The team’s 3D Chicxulub crater simulations at an angle of 60 degrees reproduced these observations almost exactly.

The simulations reconstructed the crater formation in unprecedented detail and give us more clues as to how the largest craters on Earth are formed. Previous fully 3D simulations of the Chicxulub impact have covered only the early stages of impact, which include the production of a deep bowl-shaped hole in the crust known as the transient crater and the expulsion of rocks, water and sediment into the atmosphere.

Credit: Gareth Collins/Imperial College London

These simulations are the first to continue beyond this intermediate point in the formation of the crater and reproduce the final stage of the crater’s formation, in which the transient crater collapses to form the final structure (see images below). This allowed the researchers to make the first comparison between 3D Chicxulub crater simulations and the present-day structure of the crater revealed by geophysical data.







Credit: Gareth Collins/Imperial College London


Snapshot of the start of the simulation at 30° impact



Credit: Gareth Collins/Imperial College London


Snapshot of the end of the simulation at 30° impact



Credit: Gareth Collins/Imperial College London


Snapshot of the start of the simulation at 60° impact



Credit: Gareth Collins/Imperial College London


Snapshot of the end of the simulation at 60° impact 


Credit: Gareth Collins/Imperial College London

Co-author Dr Auriol Rae of the University of Freiburg said: “Despite being buried beneath nearly a kilometre of sedimentary rocks, it is remarkable that geophysical data reveals so much about the crater structure - enough to describe the direction and angle of the impact.”

The researchers say that while the study has given us important insights into the dinosaur-dooming impact, it also helps us understand how large craters on other planets form.

Co-author Dr Thomas Davison, also of Imperial’s Department of Earth Science and Engineering, said: “Large craters like Chicxulub are formed in a matter of minutes, and involve a spectacular rebound of rock beneath the crater. Our findings could help advance our understanding of how this rebound can be used to diagnose details of the impacting asteroid.”

The work was supported by the International Ocean Discovery Program (IODP), International Continental Scientific Drilling Program (ICDP), (STFC) DiRAC High Performance Computing Facility and the Natural Environment Research Council.




Contacts and sources:
Caroline Brogan
Imperial College London

Publication: “A steeply-inclined trajectory for the Chicxulub impact” G. S. Collins, N. Patel, T. M. Davison, A. S. P. Rae, J. V. Morgan, S. P. S. Gulick, IODP-ICDP Expedition 364 Science Party.






Archaeologists Reveal Rock Art’s Big Little Secret



Australian archaeologists have discovered some of the most detailed examples of rare, small-scale rock art in the form of miniature stencils in a rockshelter traditionally owned by the Marra people.

The research, published in the journal Antiquity, examined the unusual art from the Yilbilinji rockshelter at Limmen National Park in the southwest Gulf of Carpentaria region of northern Australia.

Traditionally owned by the Marra Aboriginal people, the site was documented by the research team in 2017 and instantly stood out as unique.

The Yilbilinji rock art site

 Photos Dr Liam Brady, Flinders University.


“It’s the size of the rock art that makes this site unusual and highly distinctive,” says Flinders University archaeologist ARC Future Fellow Dr Liam Brady.

“Typically, stencilled rock art around the globe features full or life-sized dimensions such as human and animal body parts, objects (e.g. boomerangs), and even plant matter.

“However, many of the stencils at Yilbilinji are tiny or miniature-sized, and too small to have been made using real-life body parts and full-size objects.”

Only two other examples of this miniature stencilled form of rock art, both human figures, are known from anywhere in the world: one at Nielson’s Creek in New South Wales, and one at Kisar Island in Indonesia.

Replication experiments were conducted to test the method used to create the art works.

Photos Dr Liam Brady, Flinders University.

The research team – archaeologists, anthropologists, Marra rangers, and Limmen National Park rangers – recorded a total of 17 images of these miniature stencils during a 2017 field trip.

The images depict a wide range of motifs including, human figures, animals (crab, long-necked turtles), kangaroo paws, wavy lines, boomerangs, and geometric shapes.

The researchers set out to find out how these unusual images were made. One clue came from the fact most of the miniature stencils were made with rounded and curved edges meaning they were probably made using something that could be easily moulded and stuck to the rock surface.

Another clue came from anthropological research in the region. Co-author and anthropologist Dr John Bradley, from the Monash Indigenous Centre, has worked with Aboriginal people in the study area for more than 40 years.

He remembers seeing beeswax used by people for a range of purposes such as an adhesive for repairing spears and harpoons. He also saw children shaping beeswax into objects and animals such as cattle, horses and cowboys.

Experimental archaeology: recreating the stencils using beeswax.

Photos Dr Liam Brady, Flinders University.

“Using these clues, the researchers decided to test if beeswax could have been used to make the miniature stencils,” he says.

“Our experiments involving heating and shaping beeswax into human figures, animals, objects, and geometric shapes, and then stencilling onto a rock slab confirmed beeswax was an excellent material for making miniature stencils.”

“Whoever made these miniature stencils – adults or children – is open for debate, as is their meaning,” says Matthew Flinders Fellow Professor Amanda Kearney.

“However, what is important here is that this discovery adds another dimension to the Australian and global rock art record,” she says.

Photos Dr Liam Brady, Flinders University.

In fact, since this discovery was made, three additional stencils have been discovered in the area – a human figure, an echidna and a freshwater turtle – which further highlights the archaeological potential at Limmen National Park.

Glenn Durie, Manager of Aboriginal Partnerships, Northern Territory Parks and Wildlife, says the research with Marra Traditional Owners, archaeologists, and park rangers means this discovery could be among the first of many more in the area.

The article, ‘A rare miniature and small-scale stencil assemblage from the Gulf of Carpentaria: replication and meaning in Australian rock art’ (May 2020) by Liam M Brady, John J Bradley (Monash University), Amanda Kearney and Daryl Wesley has been published in Antiquity (Cambridge) Vol 94, No 375 June 2020 DOI: 10.15184/aqy.2020.48

This research is funded by the Australian Research Council (DP170101083, DE170101447, FT180100038).
Contacts and sources:
Flinders University

Publication:





Earth's Magnetic Shield Weakening along South Atlantic Anomaly



In an area stretching from Africa to South America, Earth’s magnetic field is gradually weakening. This strange behaviour has geophysicists puzzled and is causing technical disturbances in satellites orbiting Earth. Scientists are using data from ESA’s Swarm constellation to improve our understanding of this area known as the ‘South Atlantic Anomaly.’

 ‘South Atlantic Anomaly.’
Credit: European Space Agency, ESA

Earth’s magnetic field is vital to life on our planet. It is a complex and dynamic force that protects us from cosmic radiation and charged particles from the Sun. The magnetic field is largely generated by an ocean of superheated, swirling liquid iron that makes up the outer core around 3000 km beneath our feet. Acting as a spinning conductor in a bicycle dynamo, it creates electrical currents, which in turn, generate our continuously changing electromagnetic field.

This field is far from static and varies both in strength and direction. For example, recent studies have shown that the position of the north magnetic pole is changing rapidly.

Over the last 200 years, the magnetic field has lost around 9% of its strength on a global average. A large region of reduced magnetic intensity has developed between Africa and South America and is known as the South Atlantic Anomaly.South Atlantic Anomaly impact radiation

The South Atlantic Anomaly refers to an area where our protective shield is weak. White dots on the map indicate individual events when Swarm instruments registered the impact of radiation from April 2014 to August 2019. The background is the magnetic field strength at the satellite altitude of 450 km.

Credit: European Space Agency, ESA

From 1970 to 2020, the minimum field strength in this area has dropped from around 24 000 nanoteslas to 22 000, while at the same time the area of the anomaly has grown and moved westward at a pace of around 20 km per year. Over the past five years, a second centre of minimum intensity has emerged southwest of Africa – indicating that the South Atlantic Anomaly could split up into two separate cells.

Earth’s magnetic field is often visualised as a powerful dipolar bar magnet at the centre of the planet, tilted at around 11° to the axis of rotation. However, the growth of the South Atlantic Anomaly indicates that the processes involved in generating the field are far more complex. Simple dipolar models are unable to account for the recent development of the second minimum.

Scientists from the Swarm Data, Innovation and Science Cluster (DISC) are using data from ESA’s Swarm satellite constellation to better understand this anomaly. Swarm satellites are designed to identify and precisely measure the different magnetic signals that make up Earth’s magnetic field.

Swarm constellation
Credit: European Space Agency, ESA

Jürgen Matzka, from the German Research Centre for Geosciences, says, “The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously. We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth’s core driving these changes.”

It has been speculated whether the current weakening of the field is a sign that Earth is heading for an eminent pole reversal – in which the north and south magnetic poles switch places. Such events have occurred many times throughout the planet’s history and even though we are long overdue by the average rate at which these reversals take place (roughly every 250 000 years), the intensity dip in the South Atlantic occurring now is well within what is considered normal levels of fluctuations.

At surface level, the South Atlantic Anomaly presents no cause for alarm. However, satellites and other spacecraft flying through the area are more likely to experience technical malfunctions as the magnetic field is weaker in this region, so charged particles can penetrate the altitudes of low-Earth orbit satellites.

The mystery of the origin of the South Atlantic Anomaly has yet to be solved. However, one thing is certain: magnetic field observations from Swarm are providing exciting new insights into the scarcely understood processes of Earth’s interior.


Contacts and sources:
European Space Agency, ESA