A new visitor from the outer Solar System, comet C/2025 R2 (SWAN) also known as SWAN25B was only discovered late last week, on September 11. That's just a day before the comet reached perihelion, its closest approach to the Sun.

First spotted by Vladimir Bezugly in images from the SWAN instrument on the sun-staring SOHO spacecraft, the comet was surprisingly bright but understandably difficult to see against the Sun's glare. Still close to the Sun on the sky, the greenish coma and tail of C/2025 R2 (SWAN) are captured in this telescopic snapshot from September 17.

Spica, alpha star of the constellation Virgo, shines just beyond the upper left edge of the frame while the comet is about 6.5 light-minutes from planet Earth. Near the western horizon after sunset and slightly easier to see in binoculars from the southern hemisphere, this comet SWAN will pass near Zubenelgenubi, alpha star of Libra, on October 2. C/2025 R2 (SWAN) is scheduled to make its closest approach to our fair planet around October 20.

Image Credit & Copyright: Team Ciel Austral

A new investigation of Saturn’s upper atmosphere, carried out with the James Webb Space Telescope (JWST), has uncovered strikingly unusual features never before observed on any planet in the Solar System. The findings were unveiled last week by Professor Tom Stallard of Northumbria University during the EPSC-DPS2025 Joint Meeting in Helsinki.

“This opportunity to use JWST was the first time we have ever been able to make such detailed near-infrared observations of Saturn’s aurora and upper atmosphere. The results came as a complete surprise,” said Professor Stallard.

This video shows how the structures observed in Saturn’s ionosphere and stratosphere relate to one another. Starting with the aurora at 1100 km, the brightness is increased to reveal the dark bead-like features. The video then fades into the star-arm shapes within the underlying 600 km layer. The darkest beads in the ionosphere appear to line up with the strongest arm underneath it, but it is not clear if this is coincidental, or if it suggests coupling between Saturn’s lowest and highest layers of the atmosphere. Credit: NASA/ESA/CSA/Stallard et al 2025.

Beads, Stars, and the Unexpected Patterns
“We anticipated seeing emissions in broad bands at the various levels. Instead, we’ve seen fine-scaled patterns of beads and stars that, despite being separated by huge distances in altitude, may somehow be interconnected – and may also be linked to the famous hexagon deeper in Saturn’s clouds. These features were completely unexpected and, at present, are completely unexplained.”

The discovery was made by an international collaboration of 23 researchers from the UK, US, and France, who observed Saturn for a continuous 10-hour stretch on November 29, 2024, while the planet rotated under JWST’s gaze.

Although the building blocks of life such as hydrogen and oxygen appear stable to us, many theories of physics predict that they are actually just tremendously long-lived, with the particles found in their nuclei slowly, but ultimately decaying.

To investigate this idea, researchers have been hunting for evidence of this decay by looking for faint signals of decaying protons in Japan's Super-Kamiokande observatory.

So far, no definitive signals of proton decay have emerged, implying that if the proton does decay, it probably has a lifetime exceeding 1033 years—that's 10 with 32 zeros behind it.

But the Japanese observatory can't see every type of proton decay: if the decay fragments are too low in energy, they would be invisible to the detector.

In a recent study published in Physical Review Letters, Virginia physicists showed that two other observatories—the Jiangmen Underground Neutrino Observatory (JUNO) and the Deep Underground Neutrino Experiment (DUNE)—should soon be able to see these lower-energy proton decays thanks to their complementary detector designs.

"Lowering the detection threshold will open a much wider window to include decays that might have fallen through the cracks in earlier searches," said Ian Shoemaker, associate professor in the Department of Physics and study co-author.

Working with Julian Heeck from the University of Virginia, Shoemaker found that proton decay experiments can also be sensitive to protons decaying anywhere inside Earth, if they decay into new elementary particles.

Most intriguingly, said Shoemaker, one of these new particles could be the long-sought-after "sterile neutrino," which would finally allow scientists to understand the origin of neutrino mass.

"Our initial exploration of these signatures hints at many novel exciting opportunities for theoretical and experimental work that could lead to the groundbreaking discovery of new physics," Shoemaker said.

In May 2010, Japan’s Aerospace Exploration Agency (JAXA) launched the "Planet C" spacecraft – also known as "Akatsuki" or the Venus Climate Orbiter – towards Earth's "sister planet". The early stages of the mission did not go as planned. On its approach to Venus in December 2010, the spacecraft was supposed to decelerate with a controlled burn to place it in orbit. But due to a malfunction with the main engine, the planned 12-minute burn lasted just three, and Planet C shot well past its target instead.

That could have been the end of it, but JAXA was able to use the spacecraft's auxiliary reaction control system to adjust its trajectory and slow it down as it orbited the Sun. Five years later, the space agency announced that they had finally put the probe around Venus, and work could begin.

“As a result of measuring and calculating the Akatsuki’s orbit after its thrust ejection, the orbiter is now flying on the elliptical orbit at the periapsis altitude of about 400 kilometers and apoapsis altitude of about 440,000 kilometers from Venus," the space agency announced in 2015. "The orbit period is 13 days and 14 hours. We also found that the orbiter is flying in the same direction as that of Venus’s rotation.”

Soon after that, the spacecraft began returning its first photographs and data, helping us to study the atmosphere of Venus. Though not in its original planned orbit, the orbit it ended up in was advantageous.
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"Communication with 'Akatsuki' was lost during operations near the end of April 2024, triggered by an incident in a control mode of lower-precision attitude maintenance for a prolonged period," JAXA explained in a statement.

"Although recovery operations were conducted to restore communication, there has been no luck so far. Considering the fact that the spacecraft has aged, well exceeding its designed lifetime, and was already in the late-stage operation phase, it has been decided to terminate operations."

Monday 20:19 CEST marked the September Equinox!

This image from eumetsat’s Meteosat-12 satellite, captured that morning, shows Earth on the equinox — when the terminator line runs from pole to pole, dividing the planet into equal halves of light and dark. From space, it appears as a strikingly vertical line.

High energy scans or the body looking for tumors or infections could be greatly improved by adopting perovskite detectors instead of the fragile or low-resolution options currently in use, a new study reports. The process would not only make the diagnosis of health threats more accurate, but reduce exposure to radiation that can cause problems down the line, saving money at the same time.

Advances in nuclear medicine mean that we can now measure the biological activity at a location in the body, for example the blood flow in small veins or arteries to identify abnormalities. Increasingly, such techniques applied to the brain allow doctors to distinguish between different types of dementia, that may respond to different interventions, among a host of other applications.

“Perovskites are a family of crystals best known for transforming the field of solar energy,” said Professor Mercouri Kanatzidis of Northwestern University in a statement. “Now, they are poised to do the same for nuclear medicine. This is the first clear proof that perovskite detectors can produce the kind of sharp, reliable images that doctors need to provide the best care for their patients.”

Nuclear medicine includes treatments such as radiotherapy, but in this context is about diagnosis, not treatment. Single-photon emission computing tomography (SPECT) represents a way to build three dimensional reconstructions of organs. A short-lived gamma ray source is placed inside the body, and the rays emitted are captured by detectors. Subtle changes in activity affect the movement of the gamma rays, allowing the detector to put together an image, just as bones show up on X-rays, but in this case the reconstructions can be 3D.

However, the existing detector technologies are expensive to build, and one of the two main receptor chemistries, cadmium zinc telluride, is prone to cracking. The alternative, sodium iodide, lacks clarity.

Kanatzidis was one of the pioneers of making solar cells from perovskites, a technology that is now starting to reach commercial application, offering cheaper and more efficient energy collection from the Sun. In the process, Kanatzidis’s team developed skills in producing perovskite crystals with few flaws or impurities. Kanatzidis noted some of these crystals efficiently convert high-energy photons to electricity, as well as the other characteristics needed to make them excellent detectors of X-rays or gamma rays.

A novel class of light-sensitive nanoparticles may one day enable new approaches to medical imaging. They were developed by a research team at Martin Luther University Halle-Wittenberg (MLU). The particles absorb laser light and convert them into heat, thereby changing their internal structure, similar to folded proteins. The research was published in the journal Communications Chemistry.

The newly developed particles are known as single-chain nanoparticles (SCNPs) and consist of individually folded polymer chains. The scientists embedded molecules of the substance polypyrrole into these chains, which absorb light in the near-infrared range and convert it into heat. Laser irradiation not only causes the nanoparticles to heat up, they also change their internal structure.

"When exposed to light, each individual nanoparticle clumps together to form a spherical structure that is only a few nanometers in diameter. This opens up the possibility of concentrating them in specific areas of the body—precisely where there is light," says MLU-chemist Professor Wolfgang Binder. He led the study together with Dr. Justus Friedrich Thümmler, Professor Karsten Mäder from the Institute of Pharmacy, and Professor Jan Laufer from the Institute of Physics.

SCNPs have a remarkable thermoresponsivity; their structure reacts to changes in temperature. This property is based on the specific molecular design of the particles, which also allows them to convert light into heat very efficiently. Experiments in the lab have shown that even a weak laser beam and relatively few nanoparticles are enough to generate very high local temperatures—up to 85°C.

This effect is important, for example, for imaging techniques used in medical diagnostic testing. The rapid heating of the tissue releases sound waves. These can be measured with photoacoustic imaging techniques, which, in turn, can be used to create 3D models of the inside of the body.

The team hopes that the newly developed particles could help study the development of cancer in a few years' time, for example, by using photoacoustic imaging to make tumors and their response to treatment more visible and easier to track.

But the potential goes even further: "In the future, we want to use the nanoparticles to transport an active ingredient into the body in a targeted manner and activate it there using light and heat," explains Binder. The particles could possibly even be used to kill cancer cells through light-controlled heat, a process known as hyperthermia. However, more extensive studies are needed to explore the therapeutic potential of the new particles.

Spiral, elliptical or neither? 🍩

Today’s NASA/ESA Hubble Space Telescope image features the galaxy NGC 2775.

NGC 2775 sports a smooth, featureless centre that is devoid of gas, resembling an elliptical galaxy. It also has a dusty ring with patchy star clusters, like a spiral galaxy.

Because we can only view NGC 2775 from one angle, it’s difficult to say for sure.

Which do you think it is? ➡️ esahubble.org/images/potw253…

Human activity has added an average of 40 days to the global wildfire season, fundamentally changing when fires occur around the world. New research from the University of Tasmania, published in Nature Ecology & Evolution, shows that more than half of all burned area now happens outside the natural fire season, the period when lightning and dry conditions naturally coincide.

The study analyzed fuel moisture and lightning data across more than 700 ecological regions worldwide, finding that humans have altered wildfire timing in nearly every environment on Earth, from tropical savannas to boreal forests to Mediterranean landscapes.

"Before people began influencing fire, wildfires mostly happened when lightning struck during dry conditions," said lead author Dr. Todd Ellis, Research Associate in Physical Pyrogeography at the University of Tasmania.

"Our study separates natural fire seasons from those driven by people, showing just how much human influence has reshaped when wildfires occur across the globe."

The transformation is most dramatic in tropical grasslands, where people have effectively extended the wildfire season by around three months, with most fires now occurring in this human-driven window.
Importantly, even remote boreal forests and tundra are beginning to experience longer fire seasons, stretching beyond what natural lightning ignitions would allow.

This global shift in wildfire seasonality poses significant ecological risks. Species have evolved over millennia to cope with wildfires occurring during specific seasonal windows. When wildfires happen outside these natural periods, ecosystems face unprecedented stress.

"We're not just seeing more wildfires, and fires of a greater intensity, we're seeing them at times of the year when ecosystems haven't evolved to cope with them," co-author Dr. Grant Williamson explained.

"This temporal mismatch can hamper species recovery and disrupt reproductive processes which are often closely tied to specific seasons, thereby threatening biodiversity in ways we're only beginning to understand."

NASA introduced its newest astronauts Monday, 10 scientists, engineers and test pilots chosen from more than 8,000 applicants to help explore the moon and possibly Mars.

For the first time, there were more women than men in an incoming astronaut class. They included a geologist who worked on NASA's Curiosity Mars rover and a SpaceX engineer who's already rocketed into orbit, flying on a billionaire-sponsored mission that featured the world's first private spacewalk last year.

The six women and four men will undergo two years of training before becoming eligible for spaceflight.

Acting Administrator Sean Duffy said one of them could become one of the first to step on Mars. He also stressed that the U.S. will win this second race to land astronauts on the moon.

Research on rare post-mortem brain tissue shows changes in gene activity, offering new insight into the biological basis of depression.

Researchers from McGill University and the Douglas Institute have discovered two distinct types of brain cells that show alterations in individuals with depression.

Their study, published in Nature Genetics, paves the way for potential treatments that directly target these cells while also advancing scientific understanding of depression, a major global health challenge affecting over 264 million people.

“This is the first time we’ve been able to identify what specific brain cell types are affected in depression by mapping gene activity together with mechanisms that regulate the DNA code,” said senior author Dr. Gustavo Turecki, a professor at McGill, clinician-scientist at the Douglas Institute and Canada Research Chair in Major Depressive Disorder and Suicide. “It gives us a much clearer picture of where disruptions are happening, and which cells are involved.”

Rare brain bank enables breakthrough
The team examined post-mortem brain tissue from the Douglas-Bell Canada Brain Bank, one of the rare global resources containing donated samples from individuals with psychiatric conditions.

Using single-cell genomic methods, they analyzed RNA and DNA from thousands of brain cells to determine which cell types functioned differently in depression and which DNA sequences might account for those changes. Their analysis included samples from 59 individuals with depression and 41 without the condition.

Tardigrades — also known as water bears or moss piglets — are pretty adorable. Under a microscope, each one looks a bit like a plump caterpillar, wriggling around on eight legs tipped with dainty clawed feet. But don’t let their cuteness fool you. These salt grain–sized animals are some of the toughest beasts on Earth.

Water bears can brave days in space without air. They can cope with temperatures colder than any ever measured on Earth. They have been known to survive hundreds of times the X-ray radiation that would kill a human. And they’ve even withstood getting blasted out of a gun at more than 1,800 miles per hour. Basically, tardigrades are the ultimate extremophiles.

Why did these wee creatures evolve to be so durable? Some 1,300 species of tardigrades have been found. They thrive in ponds, streams and damp soil and clumps of moss. Many of those places can dry out in the summer. So tardigrades need ways to survive being parched. Adaptations they evolved to survive dehydration may have bestowed tardigrades with the power to survive other harsh conditions.

Alarge asteroid strike on the Moon could have negative consequences for the artificial satellites we now depend on. That being the case, a NASA-led team has looked into the options for preventing Asteroid 2024 YR4 from making such an impact in 2032. Contrary to the usual conclusions that asteroids should be diverted, not destroyed, they think this is a time for a Hollywood-approved demolition event.

When 2024 YR4 was discovered last December, it sparked headlines around the world, given the small possibility it would strike the Earth less than eight years later. As we learned more about its orbit, that chance rose to 3 percent before being downgraded. At an estimated 60 meters (200 feet) wide, this is no dinosaur-killer in size, nor probably speed, but it is large enough to do serious local damage if it struck a populated area, or unleash tsunamis in the ocean.

We now know the chance of a direct hit to Earth is essentially zero, but the chance of 2024 YR4 striking the Moon in seven years is currently 4 percent. While most people have been looking forward to the history-making once-in-5,000-years show we might all get if such an event were to occur, some spoilsports are crying “won’t somebody think of the satellites” and considering options.

An impact this large would inevitably throw up a lot of material, and with no atmosphere to constrain it, vast quantities of tiny particles would escape the low lunar gravity and spread widely. Some of this material would impact Earth’s atmosphere, creating a marvelous meteor shower lasting several days. Most of the rest would expand around the general vicinity of the Earth-Moon system, sometimes colliding later to slightly increase our ongoing meteor count. 

This all sounds great until you consider all the satellites that are vulnerable to being hit by material this size, including the JWST and the International Space Station. In a pre-print paper still undergoing peer review, a team led by Brent Barbee of NASA’s Goddard Space Flight Center has looked into what can be done to minimise the danger.

Stars close to the center of our galaxy dance around what appears to be nothing at all, but is actually a black hole with the mass of 4 million Suns.

Born to climb, these ibex kids, just days old, navigate dizzying cliffs as they follow the herd to the desert's most important resource—water.

A small group of leopard sharks has been seen – and caught on film – engaging in a three-way bout of reproductive hanky-panky in the wild.

It's the first time scientists have documented this mating behavior in the animals, as first one male and then a second mated with a female leopard shark (Stegostoma tigrinum) in quick succession. The stunning observation, recorded from beginning to end, could shed light on the reproductive strategies of this endangered species.

The Trump administration just announced a program of actions to tackle the so-called “autism epidemic”, a term that is disputed by many within the autistic community. As well as seeking Food and Drug Administration (FDA) approval for a new drug treatment, safety label changes are being pursued for acetaminophen (paracetamol) due to a “potential association” between its use in pregnancy and neurodevelopmental conditions.

They told us way back in April that they would “know” the causes of autism by September. As predicted, the new announcements from the US Department of Health and Human Services (HHS) cannot go as far as that, but they do bring forth a suite of “bold actions” that many scientific experts say are not supported by any quality data and that, in short, are going too far, too fast.
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“Following the science”, however, is the last thing these policies are doing, according to some experts.

“The best available evidence is that paracetamol use in pregnancy is not linked to autism,” Dr Edward Mullins, Clinical Associate Professor at Imperial College London, told the Science Media Centre. “In the absence of any new evidence, the reported press release from the Trump administration claiming it is would appear to be an unsubstantiated theory which is likely to lead to an essential treatment for fever and pain being denied to women in pregnancy without good reason, contrary to US and European medical guidance.”

“The fear mongering will prevent women from accessing the appropriate care during pregnancy,” said Dr Monique Botha, Associate Professor at Durham University. “Further, it risks stigmatising families who have autistic children as having brought it on themselves and reinvigorates the long pattern of maternal shame and blame as we’ve seen re-emerge repeatedly over the last 70 years where we try to pay the fault of autism at the mother’s door one way or another.”

The makers of Tylenol, Kenvue, pushed back strongly as well, telling the BBC that they are “deeply concerned with the health risk this poses for expectant mothers.”

Is life possible—or has it ever been possible—on other planets? The (Origin of) Life Marker Chip (LMCOOL) seeks the answer. This innovative chip is being developed by a Dutch consortium led by TU Delft. UT researcher Jurriaan Huskens and his team are going to make the optical sensor selective for the required biomarkers.

A Dutch-built instrument capable of detecting traces of life on Saturn's moon Enceladus—that is the ultimate dream of TU Delft researcher Niels Ligterink. Over the coming years, he will work with around thirty colleagues from various Dutch companies and knowledge institutes on the (Origin of) Life Marker Chip (LMCOOL).
The invention is best described as a tiny yet complete laboratory in the form of a computer chip. It is "pre-programmed" to identify specific molecules in liquids; molecules that could point to life, such as amino acids.

"You can best compare our chip to a keyhole, with the molecule we are searching for as the key," explains Ligterink, "Because only one key fits in the keyhole, we can be almost 100% certain that we have captured the molecule we are looking for when we detect something with our chip. This makes our lab-on-a-chip revolutionary."

UT researcher Huskens adds, "An important step forward is that we are going to selectively recognize a mirror image of an amino acid. After all, living organisms make only one of the mirror images, and so this recognition is essential to determine whether the amino acid comes from a life process or not."

A lighter way to search for life
The idea for the Life Marker Chip (LMC) was first proposed more than twenty years ago for ESA's ExoMars mission. Although ESA eventually selected other instruments for that mission, the consortium partners remained enthusiastic about the concept. With financial support from the NSO Instruments Program, the instrument is now being further developed so that it can be used on a range of future planetary missions.

One of the greatest advantages of the new LMCOOL is its compact size and low weight. Current life-detection instruments on Mars are the size of a microwave oven and weigh between ten and twenty kilos. By contrast, LMCOOL will be about the size of a soft drink can and weighs only 700 grams. In space exploration, where every kilogram of launch mass matters, the Dutch chip offers a lightweight yet high-performance alternative.

The new find was possibly 23 feet (7 meters) long and hailed from a mysterious group of dinosaurs called megaraptorans. They prowled across what's now South America, Australia and parts of Asia, splitting off into different species over millions of years.

Megaraptorans were known for their stretched-out skulls and "huge and very powerful claws," said Lucio Ibiricu with the Patagonian Institute of Geology and Paleontology, who was part of the discovery team.

But it's not yet clear how these creatures hunted and where they fall on the evolutionary timeline—mainly because the fossils recovered so far were incomplete.

In a new study, researchers said they uncovered part of a skull as well as arm, leg and tail bones from the Lago Colhué Huapi rock formation in Patagonia. They noticed unique features in the bones that made them realize this could be a new species.

This latest member of the megaraptoran clan named Joaquinraptor casali "fills a major gap by providing one of the most complete skeletons yet," Federico Agnolin with the Argentine Museum of Natural Science Bernardino Rivadavia said in an email.

Our vision for the future of space transportation.
Transportation hubs in orbit around our planet will act as airports and train stations on Earth, offering refilling and maintenance services for spacecraft en route to other destinations and platforms.