According to a widely accepted theory, the mass extinction at the Cretaceous-Paleogene boundary was triggered by the impact of an asteroid at least 10 kilometres in diameter near Chicxulub on the Yucatán Peninsula in Mexico. On impact, the asteroid and large quantities of earth rock vaporized. Fine dust particles spread into the stratosphere and obscured the sun. This led to dramatic changes in the living conditions on the planet and brought photosynthetic activity to a halt for several years.

The dust particles released by the impact formed a layer of sediment around the entire globe. This is why the Cretaceous-Paleogene boundary can be identified and sampled in many places on Earth. It contains high concentrations of platinum-group metals, which come from the asteroid and are otherwise extremely rare in the rock that forms the Earth’s crust.

By analysing the isotopic composition of the platinum metal ruthenium in the cleanroom laboratory of the University of Cologne’s Institute of Geology and Mineralogy, the scientists discovered that the asteroid originally came from the outer solar system. “The asteroid’s composition is consistent with that of carbonaceous asteroids that formed outside of Jupiter’s orbit during the formation of the solar system,” said Dr Mario Fischer-Gödde, first author of the study.

The ruthenium isotope compositions were also determined for other craters and impact structures of different ages on Earth for comparison. This data shows that within the last 500 million years, almost exclusively fragments of S-type asteroids have hit the Earth. In contrast to the impact at the Cretaceous-Paleogene boundary, these asteroids originate from the inner solar system. Well over 80 percent of all asteroid fragments that hit the Earth in the form of meteorites come from the inner solar system. Professor Dr Carsten Münker, co-author of the study, added: “We found that the impact of an asteroid like the one at Chicxulub is a very rare and unique event in geological time. The fate of the dinosaurs and many other species was sealed by this projectile from the outer reaches of the solar system.”

Special recordings made by Flinders University ecologists in Australia show this chaotic mixture of soundscapes can be a measure of the diversity of tiny living animals in the soil, which create sounds as they move and interact with their environment.

With 75% of the world’s soils degraded, the future of the teeming community of living species that live underground face a dire future without restoration, says microbial ecologist Dr Jake Robinson, from the Frontiers of Restoration Ecology Lab in the College of Science and Engineering at Flinders University.

This new field of research aims to investigate the vast, teeming hidden ecosystems where almost 60% of the Earth’s species live, he says.

“Restoring and monitoring soil biodiversity has never been more important.

“Although still in its early stages, ‘eco-acoustics’ is emerging as a promising tool to detect and monitor soil biodiversity and has now been used in Australian bushland and other ecosystems in the UK.

“The acoustic complexity and diversity are significantly higher in revegetated and remnant plots than in cleared plots, both in-situ and in sound attenuation chambers.

“The acoustic complexity and diversity are also significantly associated with soil invertebrate abundance and richness.”

The latest study, including Flinders University expert Associate Professor Martin Breed and Professor Xin Sun from the Chinese Academy of Sciences, compared results from acoustic monitoring of remnant vegetation to degraded plots and land that was revegetated 15 years ago.

The passive acoustic monitoring used various tools and indices to measure soil biodiversity over five days in the Mount Bold region in the Adelaide Hills in South Australia. A below-ground sampling device and sound attenuation chamber were used to record soil invertebrate communities, which were also manually counted.

“It’s clear acoustic complexity and diversity of our samples are associated with soil invertebrate abundance — from earthworms, beetles to ants and spiders — and it seems to be a clear reflection of soil health,” says Dr Robinson.

“All living organisms produce sounds, and our preliminary results suggest different soil organisms make different sound profiles depending on their activity, shape, appendages and size.

“This technology holds promise in addressing the global need for more effective soil biodiversity monitoring methods to protect our planet’s most diverse ecosystems.”

Dr Joshua Soderholm, an Honorary Senior Research Fellow from UQ’s School of the Environment, and lead researcher PhD candidate Yuzhu Lin from Penn State in the US, have found storm modelling outcomes change significantly when using real hailstones.

Key points:

• Researchers are measuring and scanning samples for a global ‘hailstone library’
• Storm simulations using 3-D modelling of real hailstones show it behaves differently than spherical hail shapes
• Data from the hail library could lead to more accurate storm forecasts

“People tend to think of a hailstone as a perfect sphere, like a golf ball or cricket ball,” Dr Soderholm said.

“But hail can be all sorts of weird shapes, from oblong to a flat disc or have spikes coming out — no two pieces of hail are the same.

“Conventional scientific modelling of hail assumes spherical hailstones, and we wanted to know if that changed when non-spherical, natural hail shapes are used.”

Ms Lin said they found the differences were dramatic.

“Modelling of the more naturally shaped hail showed it took different pathways through the storm, experienced different growth and landed in different places,” Ms Lin said.

“It also affected the speed and impact the hail had on the ground.

“This way of modelling had never been done before, so it’s exciting science.”

Dr Soderholm said building a ‘hailstone library’ was critical to further fine-tuning hailstorm simulations.

“This is effectively a dataset to represent the many and varied shapes of hailstones, to make weather modelling more accurate,” he said.

“Our study used data from 217 hail samples, which were 3-D scanned and the sliced in half, to tell us more about how the hailstone formed.

“This data is now part of a global library, as we try and get a really clear picture of hailstone shape and structure.”

Dr Soderholm said the research has significant potential.

“At the moment, the modelling is specifically for scientists studying storms, but the end game is to be able to predict in real-time how big hail will be, and where it will fall,” he said.

“More accurate forecasts would of course warn the public so they can stay safe during hailstorms and mitigate damage.

“But it could also significantly benefit industries such as insurance, agriculture and solar farming which are all sensitive to hail.”

The research paper was published in the Journal of the Atmospheric Sciences.

Dr Soderholm is also a Research Scientist at the Australian Bureau of Meteorology.

Some hail samples for the UQ data set were provided by Higgins Storm Chasing.

In a new study, now published in the Nature journal Communications Biology, scientists at the University of Cincinnati have determined when the taste buds start to appear in areas beyond the oral cavity. The study was supported by the National Science Foundation.

To begin, blind cavefish evolved in cave ponds in northeastern Mexico. They are pale pink and nearly translucent compared to their silvery counterparts that live in surface rivers and streams. While cavefish have the faintest outline of eye sockets, the surface fish have enormous round eyes that give them a perpetually surprised expression.

Despite the many obvious physical differences, the two fish are considered the same species.

“Regression, such as the loss of eyesight and pigmentation, is a well-studied phenomenon, but the biological bases of constructive features are less well understood,” says the article’s senior author UC professor and biologist Joshua Gross, whose laboratory is dedicated to the study of evolution and development of cave-dwelling vertebrates.

Although scientists in the 1960s discovered that certain populations of blind cavefish had extra taste buds — on the head and chin — there was no further study of the developmental or genetic processes that explain this unusual trait, says Gross.

To determine when the extra taste buds appear, Gross and his research team looked at the species Astyanax mexicanus, including two separate cavefish populations that dwell in the Pachón and Tinaja caves in northwestern Mexico, known to have the additional taste buds.

The research team found that the number of taste buds is similar to the surface fish from birth through 5 months of age. The taste buds then start to increase in number and appear on the head and chin in smatterings, well into adulthood, at approximately 18 months.

Cavefish can live much longer than 18 months in nature and captivity, and the authors suspect even more taste buds continually accumulate as the fish get older.

While timing of taste bud appearance was comparable for the Pachón and Tinaja cavefish populations, some differences were evident with respect to density and timing of expansion, says Gross. The other surprising discovery from this study, says Gross, is the genetic architecture of this trait: “Despite the complexity of this feature, it appears that more taste buds on the head are controlled mainly by only two regions of the genome.”

The increase correlates with the time that the cavefish stop eating other live foods for sustenance and start to pursue other food sources, Gross says, such as bat guano. Equally fascinating, he says, is that the expansion may occur in other cave locations where there are no bat populations.

With more taste buds, he says, the cavefish have a keener sense of taste, “which is likely an adaptive trait.”

“It remains unclear what is the precise functional and adaptive relevance of this augmented taste system,” says Gross, which has led the team to begin new studies that focus on taste, by exposing the fish to different flavors such as sour, sweet and bitter.

But superconductors typically only work at extremely cold temperatures. When these materials are heated, they become ordinary conductors, which allow electricity to flow but with some energy lost, or insulators, which don’t conduct electricity at all.

Researchers have been hard at work looking for superconductor materials that can perform their magic at higher temperatures — perhaps even room temperature someday. Finding or building such a material could change modern technology, from computers and cell phones to the electric grid and transportation. Furthermore, the unique quantum state of superconductors also makes them excellent building blocks for quantum computers.

Now, researchers have observed that a necessary characteristic of a superconductor — called electron pairing — occurs at much higher temperatures than previously thought, and in a material where one least expects it — an antiferromagnetic insulator. Although the material did not have zero resistance, this finding suggests researchers might be able to find ways to engineer similar materials into superconductors that operate at higher temperatures. The research team from SLAC National Accelerator Laboratory, Stanford University, and other institutions published their results August 15 in Science.

“The electron pairs are telling us that they are ready to be superconducting, but something is stopping them,” said Ke-Jun Xu, a Stanford graduate student in applied physics and paper co-author. “If we can find a new method to synchronize the pairs, we could apply that to possibly building higher temperature superconductors.”

Out-of-sync electrons

Over the past 100 years, researchers have learned a lot about how exactly superconductors work. We know, for instance, that for a material to superconduct, electrons have to pair off, and these pairs must be coherent — i.e., their movements must be synchronized. If electrons are paired but incoherent, the material might end up being an insulator.

In superconductors, the electrons act like two reticent people at a dance party. At first, neither person wants to dance with the other. But then the DJ plays a song that both people like, allowing them to relax. They notice one another enjoying the song and become attracted from afar — they have paired but have not yet become coherent.

Then the DJ plays a new song, one that both people absolutely love. Suddenly, the two people pair and start to dance. Soon everyone at the dance party follows their lead: They all come together and start dancing to the same new tune. At this point, the party becomes coherent; it is in a superconducting state.

In the new study, the researchers observed electrons in a middle stage, where the electrons had locked eyes, but were not getting up to dance.

Cuprates acting oddly

Not long after superconductors were first discovered, researchers found that the thing that got electrons paired up and dancing was vibrations in the underlying material itself. This kind of electron pairing happens in a class of materials known as conventional superconductors, which are well understood, said Zhi-Xun Shen, a Stanford professor and investigator with the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC who supervised the research. Conventional superconductors work at temperatures typically close to absolute zero, below 25 Kelvin, in ambient pressure.

Unconventional superconductors — such as the copper oxide material, or cuprate, in the current study — work at significantly higher temperatures, sometimes up to 130 Kelvin. In cuprates, it is widely believed something beyond lattice vibrations helps pair up electrons. Although researchers aren’t sure exactly what’s behind it, the leading candidate is fluctuating electron spins, which cause the electrons to pair and dance with a higher angular momentum. This phenomenon is known as a wave channel — and early indications of such a novel state were seen in an experiment at SSRL about three decades ago. Understanding what drives electron pairing in cuprates could help design superconductors that work at higher temperatures.

In this project, scientists chose a cuprate family that had not been studied in depth because its maximum superconducting temperature was relatively low — 25 Kelvin — compared to other cuprates. Even worse, most members of this family are good insulators. To see the atomic details of the cuprate, researchers shined ultraviolet light onto material samples, which eject electrons from the material. When the electrons are bound, they are slightly more resistant to being ejected, resulting in an “energy gap.” This energy gap persists up to 150 Kelvin, suggesting that electrons are paired at much higher temperatures than the zero resistance state at about 25 Kelvin. The most unusual finding of this study is that the pairing is the strongest in the most insulating samples.

The cuprate in the study might not be the material to reach superconductivity at room temperature, around 300 Kelvin, Shen said. “But maybe in another superconductor material family, we can use this knowledge for hints to get closer to room temperature,” he said.

“Our findings open a potentially rich new path forward,” Shen said. “We plan to study this pairing gap in the future to help engineer superconductors using new methods. On the one hand, we plan to use similar experimental approaches at SSRL to gain further insight into this incoherent pairing state. On the other hand, we want to find ways to manipulate these materials to perhaps coerce these incoherent pairs into synchronization.”

This project was supported in part by the DOE’s Office of Science. SSRL is a DOE Office of Science user facility.