It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Tuesday, September 29, 2026
Beyond temperature: How people experience urban heat
Urban heat is more than a matter of temperature. It can affect how people sleep, work, travel through the city, how they dress, and even how safe or comfortable they feel in public space. Yet these everyday consequences often remain invisible in conventional assessments of urban heat.
This summer in Europe and in Germany particularly, has shown just how dramatic the effects of heat waves can be – ranging from a reduced quality of life and enormous economic damage to a high number of heat-related deaths.
A new study by an interdisciplinary team from the University of Würzburg, the German Aerospace Center (DLR), and the Mendel University in Brno (Czechia) examines the human dimension of urban heat, using Mexico City in 2022 as a case study.
Their study combines satellite observations, weather-station measurements, urban spatial structures, census data, and geolocated social media posts to understand how and where urban heat affects urban residents. This latest study demonstrates the added value of interdisciplinary research – the combination of remote sensing, linguistics, digital humanities and geography enables a more spatially and thematically nuanced examination of the phenomenon of heat. This study was conducted within the field of Geolingual Studies, currently developed at JMU Würzburg. (https://www.phil.uni-wuerzburg.de/gls Intern: 251126)
Heat affects many aspects of everyday urban life
The researchers found a clear threshold. The lead author of the study, Dr. Richard Lemoine-Rodríguez, explains: “Once air temperatures exceeded 25°C, heat-related social media posts from Mexico City increased exponentially, showing that heat becomes a public concern above this threshold. Additionally, we found that more heat-related posts were shared from hotter and more densely built parts of Mexico City.”
“What people discussed online showed that heat affects many dimensions of everyday life. The most common issue was health problems and heat stress, with users describing fatigue, insomnia, physical discomfort, and emotional distress. Working conditions and clothing were another prominent concern: people described insufficient cooling infrastructure and reported that they were not allowed to wear shorts at work despite extreme heat, and in some cases argued that work should stop under those conditions”, Dr. Lemoine-Rodríguez elaborates further.
Women also described unwanted attention and harassment when wearing lighter clothes to cope with high temperatures, turning this adaptation strategy into a distressing experience for them.
Professor Carolin Biewer explains further findings. “Other posts focused on public transport and infrastructure; including delays, uncomfortable journeys, and insufficient ventilation or air conditioning. Users also described the situation of having to decide which was the lesser of two evils: exposure to heat or air pollution. If they were to open a window to cool down, they would at the same time be forced to inhale polluted air.”
Discussion also included cooling areas and air conditioning as well as concerns about birds, pets, and other animals needing water. Some posts also connected the heat with broader concerns about social inequality and climate change.
From measured to experienced heat
Professor Hannes Taubenböck emphasizes that “satellites and weather stations can tell us where it is hot and how hot it is. But they cannot reveal whether people cannot sleep, struggle to work, feel unsafe, or suffer during their daily commute. This is the central idea behind the study: moving from measured to experienced heat.”
By combining physical measurements with social media data, the authors of this research identified not only where heat occurs, but also the concrete problems it creates in people’s daily lives.
The study therefore points toward a more human-centred approach to climate adaptation, in which temperature maps are complemented by information about people’s experiences and needs.
“To adapt cities to increasing heat, it is not enough to know how hot they are. We also need to understand what that heat means for people”, says Taubenböck.
Journal
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
ARLINGTON, Va. — The Association for Professionals in Infection Control and Epidemiology (APIC) and the Society for Healthcare Epidemiology of America (SHEA) issued the following statement in response to The New York Times report on staffing losses and operational strain at the Centers for Disease Control and Prevention:
Every day, infection preventionists and healthcare epidemiologists in hospitals, nursing homes, and outpatient clinics rely on the CDC's science, surveillance, and guidance to keep patients and healthcare personnel safe. The reporting that the agency has lost nearly a third of its workforce, including experienced scientists in its emerging infectious disease and respiratory disease centers, confirms what our members have been experiencing on the front lines. Guidance is slower to arrive, technical assistance is harder to reach, and scientific expertise is thinner at a time when it is most needed.
The timing could not be more concerning. Healthcare facilities are entering respiratory virus season without updated federal vaccine recommendations. At the same time, they are preparing for measles exposures and monitoring imported threats such as Ebola. Infection prevention does not work without a strong, credible national partner. When that partner is weakened, the burden shifts to already stretched facilities and to state and local health departments. Ultimately, patients and communities bear the consequences.
"Infection preventionists safeguard our nation’s healthcare system against healthcare-associated infections, and we depend on the CDC to arm us with timely, evidence-based guidance," said APIC President, Kathy Ward RN, BSN, MPH, FAPIC, CIC. "The losses described in this report put that partnership, and patient safety, at risk."
"Healthcare epidemiology is built on sound science and trusted data," said Lisa Maragakis, MD, MPH, FIDSA, FSHEA, President, SHEA. "The CDC's scientific independence and expert workforce are national assets that cannot be rebuilt overnight once they are lost."
APIC and SHEA urge Congress and the Administration to take three key steps:
Restore and sustain CDC staffing in infectious disease, healthcare quality promotion, and laboratory programs.
Protect the agency's scientific independence.
Ensure that funds appropriated for state and local public health partners are distributed promptly.
About APIC The Association for Professionals in Infection Control and Epidemiology (APIC) is the leading professional association for infection preventionists with a mission to create a safer world through the prevention of infection.
About SHEA The Society for Healthcare Epidemiology of America (SHEA) is a professional society representing physicians and other healthcare professionals in the fields of healthcare epidemiology, infection prevention, and antimicrobial stewardship.
SPACE/COSMOS
Canadian telescope directly maps earliest glow of hydrogen, opening a new window on the universe
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has shown, for the first time, that it can detect the faint glow of hydrogen gas from deep in the universe's past using only its own data.
The breakthrough paves the way for a faster, less expensive method for scientists to study dark energy — the mysterious force thought to be driving the universe to expand at an ever-increasing rate, and one of the biggest open questions in physics. The achievement also marks a milestone for the telescope, built for this very reason. The findings are published in a paper today in TheAstrophysical Journal.
“Hydrogen is the most common element in the universe and the raw material from which stars form,” said co-author Dr. Arnab Chakraborty, postdoctoral fellow at the University of Toronto who first proposed the finding. “Its faint radio emission acts like a cosmic tracer, revealing how matter is distributed across space.”
There are contradicting theories about the nature of dark energy in the astrophysical community. Using its own data, CHIME can investigate these theories independently and help prove or disprove them.
“This is a completely new technique for probing the cosmos, delivered by an instrument that was conceived, built and funded by Canadians,” said co-author Dr. Mark Halpern, professor in the UBC department of physics and astronomy and CHIME principal investigator. “It’s a bold new step in the global cosmology program and a Canadian success story.”
Mapping hydrogen’s glow
CHIME is a radio telescope near Penticton, British Columbia, hosted by the National Research Council of Canada (NRC), which maps the entire northern sky every day.
It is a pan-Canadian research project built and operated by scientists at the University of British Columbia, McGill University, the University of Toronto and the Dominion Radio Astrophysical Observatory (NRC), as well as other North American collaborators including Arizona State University.
CHIME was built to map the distribution of hydrogen gas in the early universe, allowing astronomers to calculate its expansion and thus investigate dark energy, the mysterious force thought to be driving the universe to expand faster over time.
Previously, CHIME had to cross-correlate its observations with galaxy survey data from other telescopes. Galaxy surveys investigate the same question, using light and focusing in fine detail. They cost millions more dollars, and they focus just on the part of the universe hot and dense enough to form stars.
By mapping the combined radio glow that hydrogen emits on its own, CHIME can explore the same questions at a greater scale, further back in time, at a fraction of the cost and without relying on anyone else’s results.
Signal interpretation
In an accompanying paper, the researchers examined what the observed signal reveals about the distribution of hydrogen in the universe.
“Our data indicate that roughly two per cent of the hydrogen in the universe was in neutral atomic form at this time, broadly consistent with other measurements” said co-author Dr. Shabbir Shaikh, postdoctoral fellow at Arizona State University. “By measuring how that hydrogen is distributed and clustered, CHIME gives us a new way to test our understanding of how galaxies form and evolve”.
Delayed celebration
The finding wasn’t a Eureka moment. The research applied new data analysis and processing techniques to find the faint signal amongst the overwhelming noise of the background universe, human technology and even the instrument itself. They then spent more than a year testing the finding to prove it was correct: it was indeed a call from the universe itself when it was about five billion years old, based on 94 nights of observation data collected in 2019.
“We worked very hard to convince ourselves that this wasn't a false alarm,” said Dr. Chakraborty. “After all the tests, the signal remained. That gave us confidence we were seeing real hydrogen from the distant universe.”
Seven years of data
The current measurement uses only a small fraction of the data CHIME has collected since operations began. Researchers now have nearly seven years of observations available and are working to expand the analysis to include earlier periods in cosmic history when the universe was only three billion years old.
This project is funded by the Canada Foundation for Innovation, theNational Research Council of Canada, the Natural Sciences and Engineering Research Council and the provinces of British Columbia, Ontario and Quebec, and supported by the Digital Research Alliance of Canada.
Additional quotes:
“For a long time, astrophysicists have believed there is great potential in this hydrogen mapping technique with this kind of telescope. By actually showing that the technique works in practice, we've opened up a whole new window on the universe. We can use it to test our current theories, and learn new things about galaxies and other properties of the universe.”
- Co-author Dr. Simon Foreman, assistant professor at Arizona State University
Artist’s illustration of a supermassive black hole at the center of a radio galaxy launching powerful jets (shown in pink) all the way into the galaxy’s CGM. The study finds that these jets do not light up the surrounding gas equally in all directions. Instead, the hydrogen gas glows (shown in red) most strongly along the path of the radio jets. This suggests that black holes can send energy far beyond the galaxy’s center and shape the larger gas reservoir that regulates star formation and fate of galaxies. We use optical data from the DESI survey and radio observations from the LOFAR Two meter Sky Survey (LoTss).
Credit: Image courtesy of Hailey Nelson/ Arizona State University.
Galaxies are enormous and hold hundreds of billions of stars. These stars form from cold, dense gas. Indeed, every large galaxy, including the Milky Way, is wrapped in a huge envelope of gas called the circumgalactic medium, or CGM. This gas is a reservoir of raw material and stretches 10-20 times the size of the visible portion of the galaxy. This CGM gas eventually cools, moves inward into the galaxy, and clumps together to form stars. Thus, the CGM plays a key role in shaping stars, planets, and even life within a galaxy. But astronomers have long puzzled over why, given how much star-forming gas surrounds them, galaxies don't have even more stars. What is keeping the fuel from cooling down and forming those stars?
A new study led by astronomers Sanchayeeta Borthakur of Arizona State University (ASU) and Namrata Roy, now at the Raman Research Institute (RRI), found evidence that narrow jets of heated plasma, blasted out by the supermassive black holes at galaxies' centers, can affect the whole galaxy even beyond what we can see, and may shape its future. The jets may reach out and disrupt the gas that galaxies need to keep growing. Their research has been published in the Astrophysical Journal Letters.
“This is a pathbreaking result that solves the long-standing mystery of how black holes influence galaxies, their stars, and life as we know it!” said Borthakur, Associate Professor in ASU’s School of Earth and Space Exploration. “This work opens a new direction to explore further the intricacies of the connection between the supermassive black holes trillions of miles from where we are to how we came to be here.”
Little in size, big in influence
When a black hole actively feeds on gas, it can release enormous energy that heats the surrounding gas. Even though these black holes can be powerhouses of energy, they are quite small and are roughly about the size of our solar system. On the other hand, their host galaxies can hold about 100 billion such solar systems.
“The surprising question is: how can something so small energetically impact something so enormous?” said Roy, assistant professor at RRI and former ASU Exploration Prize Postdoctoral Fellow.
One way to envision it is to think of an ant leaving its impression hundreds or thousands of kilometers away. Scientists still do not fully understand how energy from these active black holes reaches such distances and changes along the way.
The team’s study provides evidence as to how this could occur. They focused on active black holes that emit strong jets, which are narrow streams of hot, fast-moving plasma shooting out far beyond a galaxy’s visible edge. They looked for a distinct imprint in the ionization state of the gaseous reservoir caused by these jets. The ionized gas, or the “glow” from hydrogen gas they were looking for in the CGM, is so faint that no single galaxy would show it clearly. Hence, the team combined observations of hundreds of galaxies with active jets, using data from the Dark Energy Spectroscopic Instrument (DESI) survey and radio jet measurements from the LOFAR Two-meter Sky Survey (LoTSS). They combined measurements coming from the direction of the jet axes and searched for a specific telltale sign of ionized hydrogen gas along the jet path, known as H-alpha.
Roy, Borthkur and colleagues showed that when averaged over all directions around the galaxies, the signal was weak; however, along the radio jets, the H-alpha signal became clear and strong. This indicates that the gas does not glow uniformly everywhere but is particularly bright along the jet path. A simple analogy is that the jet acts less like a lamp shining in all directions, and more like a powerful beam that makes the gas glow where it passes through.
These findings show that black-hole jets do not affect the gas surrounding galaxies equally in all directions; instead, they leave a distinct impression by causing the gas to shine and become ionized mainly along the radio jet's path. They also found that the jets have the biggest impact, and that the glow from ionized hydrogen is brightest in two places: close to the galaxy where the jet first hits the CGM, and much farther out near the CGM’s outer edge, where the jet releases most of its energy. This provides a clear signature of how jets can illuminate or disrupt the surrounding gas, even at great distances, all the way to the CGM. This mechanism helps shape the galaxy's environment, influence its growth and evolution - it determines whether the galaxy continues to form stars or becomes quiescent.
“What excites me most is the scale of the connection,” Roy said. “A black hole is incredibly small compared to a galaxy, but its impact can reach hundreds of thousands of light-years, far into the galaxy’s outer reaches. The jet carries the energy outward, and the gas lights up along its path.
”As a check, the team also examined a tracer of cooler gas via the absorption signature of magnesium. Unlike the directional glow in H-alpha, Magnesium was more widely distributed isotropically and did not show any connection to the jet direction. This implies that the cool gas component might already exist as a reservoir surrounding the galaxy uniformly on all sides. Yet the jet brightens, heats, and ionizes gas along its own path, lighting up a trail and causing it to glow in H-alpha.
Black holes determine a galaxy's fate.
The findings offer some of the clearest evidence yet for how a black hole can affect galaxies far beyond its central region. By heating, stirring, and disturbing gas throughout the CGM, jets can prevent that gas from cooling down and falling inward to fuel new stars. This acts as a brake on the galaxy’s growth, changes its fate, and makes it much less active in star formation.
This means the black hole is not just “feeding” at the center of the galaxy, as some might think. It also reaches out and changes the galaxy’s environment, which can eventually change its fate.
Specific Directions: Look both ways on the path
Past studies searched for the signal but couldn't detect it, making this directional discovery an exciting breakthrough. The signal only appears when we look along the jet direction. If the astronomers had thought the CGM was the same in every direction, the team would have missed this discovery. The jet ionizes hydrogen gas along its path, making it glow in H-alpha in a very specific direction.
This study shows the value of large optical and radio surveys like the Dark Energy Spectroscopic Instrument (DESI) survey and the LOFAR Two-meter Sky Survey (LoTss). By combining many weak signals, astronomers can now study the behavior of galaxies that would otherwise stay hidden. The study also gives astronomers and theorists a new way to test how black-hole jets affect galaxies.
Contributing co-authors include Timothy Heckman at Johns Hopkins University and Tanmay Singh at Arizona State University.
Artist’s visualization of an early galaxy and its surrounding gaseous environment. The orange structures represent metal-enriched gas being expelled from the galaxy, illustrating how young galaxies began dispersing heavy elements into their surroundings within the Universe’s first 500 million years. The visualization is based on publicly available FIRE-2 cosmological simulation data and is not a direct telescope image.
When the universe was still in its infancy – only 500 million years after the Big Bang or about 3% of its current age – some of the universe's earliest stars and galaxies had already formed. Astronomers have long predicted that much of the gas surrounding these young galaxies must have remained rather pristine, composed of mostly hydrogen and helium, the primordial ingredients available in the newborn cosmos.
According to a study published by astronomers at the University of Arizona in Nature Astronomy, this picture likely is not correct. Instead, galaxies were already seeding the cosmos with heavy elements, such as oxygen and carbon, much earlier than astronomers expected.
"We observed that heavy elements escaped from galaxies very, very early in cosmic time," said Yongda Zhu, first author of the paper and postdoctoral researcher at the U of A Department of Astronomy and Steward Observatory. "Not only were the galaxies producing these elements, but they were also dispersing them, possibly seeding other galaxies."
How the universe got its elements
In the early universe, the cosmos barely contained anything other than hydrogen and helium, the two simplest elements occupying the very top of the periodic table. Over time, gravity pulled clouds of these simple elements together to form stars, where the immense pressures and temperatures inside allowed nuclear fusion and other reactions to forge more complex, heavier elements such as carbon and oxygen.
When stars burned out or ended their lives as supernovae, they shed these heavy elements into space, where they became the building blocks for future generations of stars, planets and ultimately, life. Even the carbon in our bodies and the oxygen we breathe were forged in earlier generations of stars.
Until now, however, it wasn't clear how and when heavier elements were transported from the earliest galaxies into the surrounding universe.
Looking at early galaxies
Zhu's research centered on three early galaxies whose light has traveled for more than 13 billion years, showing them as they appeared about 500 million years after the Big Bang, during a cosmic period known as the Epoch of Reionization. At that time, the first generations of stars and galaxies were transforming the early universe by ionizing the hydrogen gas between them. This process, during which electrons were stripped from their hydrogen nuclei, gradually brought an end to the cosmic "dark ages" by allowing ultraviolet light to travel more freely through the universe.
"We used the galaxies themselves as background light sources," said Zhu. "As light from the galaxies traveled toward Earth, it passed through surrounding gas, and we were able to look at the light's absorption patterns to detect specific elements."
Observations of these ancient galaxies were only made possible by the infrared capabilities of NASA's James Webb Space Telescope, which allowed the researchers to observe galaxies as they appeared about 13 billion years ago. The nearly 30 hours of exposure provided enough light to detect faint absorption patterns in the spectra of these distant galaxies.
Over the course of one long night, Zhu manually searched through publicly available JWST spectra from hundreds of galaxies and pinpointed three with absorption patterns indicating the presence of heavy elements, including carbon, oxygen and silicon. The absorption lines were "blueshifted" relative to the galaxies' redshift, indicating that the gas was moving outward from the galaxies and carrying oxygen, carbon and other heavy elements into intergalactic space.
The chemical fingerprints of these infant galaxies closely resembled those of evolved galaxies billions of years later, providing evidence that even at cosmic dawn, galaxies were already producing and spreading heavy elements into the space around them.
"Think of these elements, which originated from the galaxies' stars, as food dye dropped into a cup of water," said Zhu. "The color begins to spread through the water, and, in a similar fashion, these heavy elements from early galaxies began to escape into space and 'enrich' their surroundings."
Baryon Cycling
The process by which galaxies exchange material is known as baryon cycling. It is one reason galaxies are not isolated systems, but interconnected parts of a larger galactic ecosystem. Material produced by one generation of stars can be recycled and redistributed through this galactic ecosystem.
The discovery of early baryon cycling may also help explain why astronomers have struggled to find the first generation of stars, known as Population III stars. These stars are thought to have been the very first stars formed from pristine gas containing only hydrogen and helium, before heavier elements had been produced and dispersed throughout the universe. If galaxies were already enriching their surroundings only 500 million years after the Big Bang, truly pristine gas – and the Population III stars that formed from it – simply may not have been around long enough to be observed.
"If you start out with pure vanilla ice cream but start mixing in sprinkles soon after, it won't be long until you can no longer find any pristine, plain, vanilla ice cream,” Zhu said.
Artist’s rendering of Saturn’s icy moon Enceladus, showing a plume of ice particles and water vapour erupting from fractures near its south pole. Material originating from the moon’s subsurface ocean travels through these icy vents before being ejected into space. The new study suggests that ocean droplets freeze slowly during this journey, allowing salts to separate before the frozen droplets fragment into the chemically diverse ice grains detected by NASA’s Cassini spacecraft. The illustration is based on observations from the Cassini mission.
Saturn's icy moon Enceladus hides a global ocean beneath its frozen surface. From fractures near its south pole, material from this ocean is ejected into space as a plume of water vapour and ice particles. These particles offer scientists a rare opportunity to investigate an extraterrestrial ocean without drilling through kilometres of ice.
Now, an international research team including scientists from the Earth-Life Science Institute (ELSI) at the Institute of Science Tokyo has uncovered how ocean water may be transformed on its journey from the subsurface ocean into the tiny ice grains observed in space.
From 2004 to 2017, the Cosmic Dust Analyser aboard the Cassini spacecraft measured the composition of individual ice grains in Saturn's E-ring, which is supplied by material ejected from Enceladus. Researchers led by Prof Frank Postberg at Freie Universität Berlin analysed 961 mass spectra of salt-rich grains, known as Type 3 particles. Rather than finding grains with broadly similar mixtures of ocean salts, they discovered striking chemical diversity.
Different grains were enriched in different salts, including sodium chloride, carbonates, phosphates and potassium chloride. In particular, chloride and carbonate were rarely found together in the same sodium-rich grain. This raised a question: if these particles originated from the same ocean, how did their compositions become so different?
To investigate, Professor Yasuhito Sekine and colleagues at ELSI conducted laboratory experiments using droplets designed to reproduce the major salt components expected in Enceladus' ocean. The team froze droplets of different sizes at different cooling rates and examined how their constituent elements were distributed after freezing.
The experiments revealed that cooling rate matters. In droplets around 200 micrometres across, salts became spatially separated when the droplets froze slowly, at approximately 10 K per minute or less. Faster freezing produced a much more uniform distribution.
"What surprised us was that the diversity seen by Cassini could emerge from droplets originating from essentially the same ocean water," said Sekine. "Our experiments show that when relatively large ocean droplets freeze slowly, different salts can separate within them. If those frozen droplets are later broken apart, they can produce much smaller ice grains, each with very different chemical compositions."
The slow freezing also provides clues to conditions inside Enceladus' icy crust. Previous research had generally assumed that seawater spray freezes rapidly, moving towards space fast after leaving the ocean. The new results instead suggest that droplets at the beginning travel more slowly through the subsurface vent system, potentially through more complex pathways within fractures, before reaching the surface.
The researchers propose a multi-stage journey. Ocean spray initially forms droplets tens to hundreds of micrometres across. These travel relatively slowly through deeper parts of the vents, allowing salts to separate as the droplets gradually freeze. Closer to the surface, the gas flow accelerates and the frozen droplets collide with the walls of narrower ice channels at high speeds, causing them to shatter. The resulting fragments can contain different salt-rich regions and are eventually carried into Saturn's E-ring.
"The Cassini data showed us that these salt-rich grains are far more chemically diverse than an average ocean composition would suggest," said Postberg. "Combining those observations with the freezing experiments gives us a physical explanation: Cassini may have sampled fragments of larger frozen ocean droplets, each preserving different components that became separated during their journey towards the surface. The abundance of each individual component in the ocean is then reflected in the number of fragments in which a particular component is found."
The findings have implications for future exploration of Enceladus. Freezing and fragmentation can concentrate particular compounds into different grains. Salts are not just separated from each other but also from organics, and previous analyses have also shown that many organic species show up separated from each other at elevated concentrations. Analysing particles individually could therefore make it much easier for future spacecraft detect compounds that are otherwise diluted in the ocean, mixed with many other compounds.
On Earth, for example, chemical laboratories go to great lengths to separate and concentrate the various components of a sample before analysis. Enceladus now conveniently performs both of these “sample preparation” steps for us: The chemical components are separated from one another and then appear in elevated concentrations in a fraction of the ice particles.
Slow freezing may also create small pockets of liquid brine between growing ice crystals, where salts and organic compounds become concentrated. Such concentration could be relevant to prebiotic chemistry, where bringing dilute organic molecules together is an important challenge. Since much of Enceladus' plume material falls back onto the moon, these processes could potentially occur repeatedly.
Understanding how these particles form, therefore, provides both a picture of the hidden environment beneath Enceladus' surface and a guide for interpreting material sampled by future missions searching for clues to the moon's habitability and signs of life.
Reference
Frank Postberg1*, Zenghui Zou2,1, Yasuhito Sekine3,10,11, Minori Koga3, Jürgen Schmidt1, Mark Fox-Powell4, Fabian Klenner5,6, Jon K. Hillier1, Nozair Khawaja1, Toshihiko Kadono7, Melih Çakar1,3, Sascha Kempf8, Ralf Srama9, Cassini CDA observes compositional segregation of Enceladus’ ice grains from slow freezing and fragmentation of oceanic spray,Science Advances,DOI: 10.1126/sciadv.aee7256
Institut für Geologische Wissenschaften, Freie Universität Berlin, Berlin, Germany.
School of Mathematics and Physics, Qinghai University, Xining, China.
Earth-Life Science Institute (ELSI), Tokyo Institute of Technology, Tokyo, Japan.
School of Environment, Earth & Ecosystem Sciences , The Open University, Milton-Keynes, UK.
Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA.
Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA.
Department of Basic Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan.
Laboratory for Atmospheric and Space Physics, University of Colorado in Boulder, Boulder (CO), USA.
Institut für Raumfahrtsysteme, Universität Stuttgart, Stuttgart, Germany.
GENTEN Research Center, Institute of Science Tokyo, Tokyo, Japan.
Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Japan.
More information
Earth-Life Science Institute (ELSI) is one of Japan’s ambitious World Premiere International research centers, whose aim is to achieve progress in broadly inter-disciplinary scientific areas by inspiring the world’s greatest minds to come to Japan and collaborate on the most challenging scientific problems. ELSI’s primary aim is to address the origin and co-evolution of the Earth and life.
Institute of Science Tokyo (Science Tokyo) was established on October 1, 2024, following the merger between Tokyo Medical and Dental University (TMDU) and Tokyo Institute of Technology (Tokyo Tech), with the mission of “Advancing science and human wellbeing to create value for and with society.”
World Premier International Research Center Initiative (WPI) was launched in 2007 by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) to foster globally visible research centers boasting the highest standards and outstanding research environments. Numbering more than a dozen and operating at institutions throughout the country, these centers are given a high degree of autonomy, allowing them to engage in innovative modes of management and research. The program is administered by the Japan Society for the Promotion of Science (JSPS).
Freie Universität Berlin (German: Freie Universität Berlin, often abbreviated as FU Berlin or simply FU) is a public research university in Berlin, Germany. It was founded in West Berlin in 1948 during the early Cold War period. The Free University's name referred to West Berlin's status as part of the intellectual continuum of the Western "Free World" in contrast to Soviet-controlled East Berlin. Its main campus is located in Berlin-Dahlem in the Steglitz-Zehlendorf district.
Illustration of the proposed journey of ocean material through Enceladus' icy crust. Seawater droplets rise from the subsurface ocean and gradually freeze, allowing different salts and other chemical components to separate within them. As the frozen droplets travel through narrowing vents, collisions with the ice walls cause them to fragment into much smaller, chemically distinct grains. These particles are then ejected into space in Enceladus' plume, where they can be sampled individually by spacecraft.
Credit
FUB/Marie Dannenmann
Elemental maps of laboratory-frozen droplets containing major salt components expected in Enceladus' ocean. Each column shows the distribution of a different element, while the rows represent different cooling rates. At slower cooling rates, salts become increasingly separated into distinct regions within the droplets, particularly chloride salts associated with sodium and potassium. With faster cooling, the elements remain more uniformly distributed. These experiments show how slow freezing could produce the chemical segregation needed to explain the diverse ice grains detected by Cassini. Scale bars represent 50 micrometres.
The study examined mass spectra of ice grains from Enceladus's plume and found that the grains exhibit much greater compositional diversity than previously recognized, suggesting that plume formation is more complex than previously thought. This illustration shows the mechanism the authors propose: the plume forms through the slow freezing and fragmentation of oceanic spray originating from within the moon.
RIVERSIDE, Calif. -- With a global ocean of liquid water below a thick crust of ice, Saturn’s moon Enceladus is one of the most promising places to search for life beyond Earth. A new study suggests the moon itself may aid in that search by making some ocean compounds easier for future spacecraft to detect.
At the moon’s south pole, jets of water vapor and tiny ice particles erupt from Enceladus’s ocean and extend hundreds of miles into space to feed Saturn’s E ring. NASA’s Cassini spacecraft, which arrived at Saturn in 2004, repeatedly flew through this plume, allowing it to sample ocean-derived material without landing or drilling through miles of ice. Cassini detected salts and organic compounds, as well as evidence of water-rock interactions occurring on the moon’s rocky seafloor.
Published Sept. 25 in Science Advances, the study examined how different salts separate and become concentrated in different grains as ocean spray freezes and travels through cracks in the ice. Crucially, a similar process may concentrate organic molecules, and potentially molecular biosignatures, into individual grains, making them much easier for future spacecraft to detect.
The study examined nearly 1,000 individual salt-rich ice grains recorded by Cassini’s Cosmic Dust Analyzer. Some grains were rich in sodium chloride. Others were dominated by carbonates, phosphates, hydroxides, or potassium-bearing salts.
“We show that each grain is not necessarily a tiny scoop of the ocean,” said Fabian Klenner, a UC Riverside assistant professor of planetary sciences and co-author on the study. “It is more of a fragment of a much larger ocean droplet in which freezing separated the salts before that droplet broke apart.”
To reconstruct that process, the researchers combined Cassini data with laboratory experiments, thermodynamic calculations, and models of droplet cooling. In the experiments, they froze droplets of alkaline salt water formulated to resemble the Enceladus ocean. Larger droplets that cooled relatively slowly developed distinct salt-rich regions, while the smallest and most rapidly frozen droplets remained more uniform.
“When these droplets freeze relatively slowly, different salts can separate into distinct regions within a single grain,” Klenner said. “For example, sodium chloride could concentrate in one region and potassium chloride in another. As the grain is accelerated through the vents, collisions with the icy walls can break it into smaller fragments with different compositions. This is the mechanism we propose.”
The research team’s model begins when bursting bubbles at the ocean surface produce spray droplets. Water vapor carries the droplets upward through the vents, where they freeze slowly enough for different salts to separate. Closer to the surface, narrower passages accelerate the vapor and frozen droplets to a few hundred miles per hour, and collisions with the icy walls break them into micrometer-scale fragments.
“Enceladus actually does a lot of the work for us in preparing samples for analysis that usually take a lot of effort in chemical labs on Earth,” said Frank Postberg, a professor of planetary sciences at Freie Universität Berlin who led the study. “The oceanic constituents are separated from each other and simultaneously concentrated into individual ice particles.”
The finding also changes how scientists should interpret plume samples. A single grain may not represent the ocean’s average composition. Combining many particles into one measurement could erase the natural separation and conceal rare compounds, while analyzing grains individually preserves that information.
“Analyzing a large number of individual grains increases our chances of finding interesting compositions and gives us a better picture of the ocean as a whole,” Klenner said. “The most useful information is in the differences from grain to grain. Future missions should analyze as many individual grains as possible.”
Klenner said related physical processes may help explain why some organic compounds occur at elevated concentrations in only a small fraction of Enceladus ice grains.
“This tells us something important about the search for life on Enceladus,” he said. “Molecular signatures of life, if present, may be concentrated in only a few grains. A future spacecraft has to find exactly those grains.”
Searching for habitable environments and signs of life beyond Earth is a focus of Klenner’s research at UCR. His laboratory studies how organic molecules and possible biosignatures would appear in individual ice grains, and how spacecraft mass spectrometers could distinguish biological from nonbiological chemistry.
The research included collaborators in Germany, Japan, China, the United Kingdom, and the United States.
Klenner was funded by NASA and the European Research Council.
The title of the paper is “Cassini CDA observes compositional segregation of Enceladus’ ice grains from slow freezing and fragmentation of oceanic spray.”
The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment is more than 27,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Center. The campus has an annual impact of more than $2.7 billion on the U.S. economy. To learn more, visit www.ucr.edu.
A three-herb preparation restored immune function in rats living under simulated weightlessness and then challenged with bacteria, a research team in China reports. The study, published in Model Organisms Research, points to a nutritional way of helping crews stay well on long missions, and possibly to similar support for people on the ground.
Long-duration flight weakens the immune system, and space crew in orbit also face infection risk from microorganisms that behave differently. Escherichia coli is a normal gut bacterium, and on the ground it rarely causes trouble. In low-gravity experiments, however, bacteria including E. coli have been reported to form tougher biofilms and to switch on genes linked to virulence. Weightlessness weakens the host's own defences at the same time, and in orbit the two effects arrive together.
Jing Liu and Yao Xie of Beijing Dongfanghong Aerospace Biotech Co. Ltd., working with researchers at Beijing Institute of Technology, built a "two-hit" model to reproduce that combination: rats were tail-suspended for four weeks to simulate microgravity and given E. coli by intragastric gavage, while receiving the Ganoderma-Rhodiola Compound Preparation (GRCP), made from Ganoderma lucidum, Rhodiola rosea and Paecilomyces hepiali mycelium, daily. While most studies use one, this study combines two stressors.
Compared with untreated animals, those given GRCP showed a broadly restored immune profile across immune organs, immune cells and signalling factors. Inflammation fell both in the blood and in the lining of the gut, and the internal structure of the spleen held up. NF-κB/RelA, a switch that drives inflammation, was held in check, which the team identifies as the likely route by which a single preparation produces multi-target immune regulation. The effect was clearest at the highest dose tested.
“Traditional Chinese medicine brings a multi-component, multi-target advantage to protecting against stress-induced injury,” explains corresponding author Professor Yu-Lin Deng, School of Medical Technology, Beijing Institute of Technology, Beijing, China. “What we designed for the demands of spaceflight rests on a mechanism that is not specific to space — an innovation born for space that may end up helping far more people on the ground.”
The results provide a scientific basis for testing GRCP as a way of protecting crew health on long-duration crewed missions. The same decline in immune function seen in space also affects long-term bedridden patients, older adults and people who sit all day.
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Contact the author: Yu-Lin Deng, School of Medical Technology, Beijing Institute of Technology, Beijing, China, deng@bit.edu.cn.
The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 300 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).
Taken by the Mars Express High Resolution Stereo Camera, this view of Korolev crater near the north pole of Mars comprises five different ‘strips’ that have been combined to form a single image, with each strip gathered over a different orbit.
Although Mars may have once resembled Earth, the rocky red planet now appears far from hospitable. Still, certain details — such as ice-bound water — pique researchers’ curiosity. Much like on Earth, ice contains valuable records of past climate that could say whether Mars hosts, or has ever hosted, life.
Aside from the poles, where ice is sometimes exposed, most of Mars’ ice is buried beneath a dusty surface layer. Dust impacts climate by darkening ice, which changes how much sunlight is reflected into space. A University of Washington study published Sept. 8 in npj Space Exploration shows that the north pole of Mars contains less dust than scientists thought.
“We know there is water ice in the area surrounding the north pole of Mars, but there has been widespread disagreement as to how dusty that ice is,” said Aditya Khuller, a senior research scientist at the UW’s Applied Physics Laboratory. “If it is dustier, the ice will be darker. Just like a dark T-shirt in the sun makes you warmer, dusty ice gets warmer and vaporizes faster on Mars.”
Much of what we know about how Earth’s climate has evolved through millennia comes from sampling ice. Scientists drill deep into polar ice to draw out long cylinders that contain a record of the local atmosphere. Like a tree’s rings, these records can be dated to ancient periods of Earth’s history. But this is no easy task on Earth. On Mars, it’s even more complicated.
The National Aeronautics and Space Administration celebrated its first successful mission to Mars 50 years ago. In 2008, the Mars Phoenix mission successfully sampled ice near the north pole, a major triumph after the Polar Lander went missing near the south pole in 1999. The UW researchers used data from the Mars Phoenix mission, combined with observations from orbiting satellites, to complete this study.
Several years ago, Khuller discovered a discrepancy in the way researchers were analyzing the physical properties of ice on Mars. The leading approach was developed for studying soil on the Moon, but when Khuller checked its accuracy on Earth, the results seemed off.
In this study, Pari Mohan, who recently graduated from the UW with a degree in geoscience, worked with Khuller to redo the calculations using a different method. Theirs is based on an approach developed by Steve Warren, UW professor emeritus of Earth and space science, and an expert in analyzing snow and ice.
“His methods had been used successfully to study snow and ice on Earth for decades. So I thought it would be interesting to adapt these Earth-tested methods to Mars,” Khuller said.
The results suggest that the north pole is stacked “like an ice-cream sandwich,” with layers of dustier ice between slabs of cleaner ice. A dusty layer of frost forms over the ice every winter and disappears in the summer, revealing older, cleaner ice. Previous estimates suggested that the top layer of polar ice contained as much as 25% dust by mass, but this study says it’s closer to 3%.
“By looking at how the brightness changed over time, we figured out that there is a frost that forms in the winter and it’s more dusty. In the Martian summer it goes away, exposing cleaner, older ice,” Khuller said.
These layers contain key details about the climate of Mars thousands of years ago, when the ice is thought to have formed from snowfall. Mars experiences massive ice ages that have deposited shallow ice on roughly one-third of the planet.
Earth is stabilized by the gravitational pull of its moon. Mars, having only two small moons, “oscillates wildly,” Khuller said, which causes these dramatic ice ages.
In a previous study, Khuller and colleagues suggested that layers of dust and ice could create conditions for life on Mars. The dark layers could help trap sunlight and form pockets of meltwater within the ice. These pockets, enriched with nutrients from the dust, could potentially host bacteria and primitive life forms.
Similar pockets of shallow, dusty meltwater found in ice on Earth are often teeming with life in the summer. In the winter, the liquid water freezes and the microbes become dormant until the next summer.
“The fact that Mars and Earth both have these similar layers of water ice and dust is interesting,” Khuller said. “Why does one planet have life and the other doesn’t?”
Uncovering details about the climate moves the needle, but answering this question may take years. Khuller hopes to expand on this work by applying these improved methods to other regions of the red planet.
Satellites that navigate by talking to each other slowly lose their sense of direction, because nothing in a purely Earth-orbiting network provides a fixed reference in space. A new study shows that adding four satellites in elliptical lunar frozen orbits (ELFO) to China's BeiDou-3 navigation constellation can eliminate this drift. Using real inter-satellite link (ISL) ranging data from BeiDou-3 Medium Earth Orbit (MEO) satellites together with simulated lunar link measurements, the researchers kept the constellation's orientation stable for 60 days and held the mean user range error (URE) at 0.35 m, while the lunar satellites themselves were located to within 2.3 m in three dimensions.
Autonomous orbit determination (AOD) lets navigation satellites calculate their own orbits using only inter-satellite ranging, removing dependence on ground stations that can fail or be disrupted. But because relative range measurements cannot sense the overall rotation of a constellation, the whole network gradually drifts in orientation. Predicted orbit forecasts can slow this drift but cannot stop it, and the error grows over time, especially during eclipse seasons. Because of these challenges, there is a need for an external, dynamics-based reference that can make the constellation's absolute orientation observable over long missions.
The study, led by Xia Lin and Baojun Lin of the Chinese Academy of Sciences, was published (DOI: 10.1186/s43020-026-00217-9) in Satellite Navigation on 17 September 2026. The team combined 24 BeiDou-3 Medium Earth Orbit (MEO) satellites with four elliptical lunar frozen orbits (ELFO) satellites in a centralized extended Kalman filter (EKF), processing 60 days of real onboard BeiDou-3 inter-satellite link (ISL) measurements alongside simulated Earth-moon links. Three cases were compared: no rotational correction, traditional prediction-based correction, and the joint Earth-moon solution.
The key insight is that lunar gravity dominates the motion of ELFO satellites, breaking the dynamical symmetry that makes a GNSS (Global Navigation Satellite System) constellation's rotation unobservable. The team's observability analysis showed that the condition number of the position information matrix fell from roughly 10¹⁵–10¹⁸ with MEO satellites alone — effectively a singular, rank-deficient case — to about 10² once four ELFO satellites were added. In the joint solution, three-axis rotational biases stayed within 13.59, 10.27, and 4.04 milliarcseconds (mas) over 60 days, compared with more than 300 mas without correction and about 18 mas with prediction-based correction. The BeiDou-3 user range error (URE) remained at 0.35 m, versus 7.85 m and 0.60 m in the other two cases. The ELFO satellites also achieved high accuracy, with maximum radial, along-track, and cross-track errors below 0.16 m, 1.7 m, and 1.8 m.
The authors said the work addresses a limitation that has persisted since the earliest autonomous navigation concepts. They said that because the moon's gravity acts so differently on lunar satellites than Earth's gravity acts on MEO satellites, the two constellations respond differently to the same rotation, making that rotation visible in the ranging data. They added that using real BeiDou-3 inter-satellite link measurements, rather than simulations alone, gives a more realistic picture of what today's operational system can achieve, and that the lunar satellites essentially act as an anchor for the entire network.
The approach could support future lunar navigation and communication constellations. The ELFO, our paper studied，offers favorable coverage of the polar regions while requiring low station-keeping budgets. Both ESA's Moonlight program(ESA, 2024) and NASA’s LunaNet initiative (NASA, 2021) have selected ELFO as the reference orbit for their planned lunar navigation and communication constellations to cover the lunar south pole. Beyond the moon, the method offers a path to long-duration autonomous navigation for Earth-orbiting constellations, reducing reliance on ground infrastructure and improving resilience. The authors note that future work will replace simulated lunar links with real onboard observations once lunar satellite missions are operational, and will develop link scheduling strategies that also provide continuous positioning, navigation, and timing (PNT) services to lunar users.
Supported by the Strategic Priority Research Program of the Chinese Academy of sciences (Grant No. XDA 0350405) and the National Natural Science Foundation of China (Grant No. 42374044).
Satellite Navigation(ISSN: 2662-1363; ISSN: 2662-9291) Satellite Navigation is the official journal of the Aerospace Information Research Institute. The journal aims to report innovative ideas, new results, and progress in the theories, techniques, and applications of satellite navigation. The journal welcomes original articles, reviews and commentaries.
SETI Institute Welcomes Three New Postdoctoral Fellows
The new fellows will study the evolution of viruses and cells, habitability on Mars and the formation of planetary systems.
September 29, 2026, Mountain View, CA — The SETI Institute has welcomed three new postdoctoral fellows: Mino Fellow L. Felipe Benites and Frank Drake Fellows Genesis Berlanga and Dingshan Deng.
Their research covers three very different areas. Benites studies the evolution of viruses and cells. Berlanga studies the physical and chemical conditions that constrain the potential for life. Deng studies protoplanetary disks and the conditions in which planets form.
“What excites me about this new group of fellows is the extraordinary range of scales they bring to one of humanity’s oldest questions: how does life emerge, evolve and persist in the universe,” said Dr. Nathalie Cabrol, Director of the Carl Sagan Center at the SETI Institute. “Their research takes us from viruses and genomes, through the environments that can sustain life, all the way to the disks where planets themselves are born. Following the question of life across these scales is essential if we want to understand not just where life might exist, but how it becomes possible in the first place. This is exactly the kind of interdisciplinary science we want to foster at the SETI Institute.”
L. Felipe Benites
L. Felipe Benites investigates the evolution of viruses and cells, with a particular interest in biological systems that fall outside traditional models of genetic inheritance.
His research includes eukaryotic algae, the viruses associated with them and the genetic material exchanged between them. He uses large-scale genomic data to study how these interactions influence evolution.
Viruses lie outside the traditional tree of life, but they have had a significant role in shaping it. That makes them useful for investigating questions about the evolution and complexity of life.
Benites has also expanded his research to the origins of genomic complexity and the early evolution of proteins. His work combines computational, phylogenetic, comparative and environmental genomic approaches.
“I’m thrilled to join the SETI Institute and have their support to pursue fascinating questions such as: Could there still be hidden forms of life on our own planet,” said Benites. “Exploring this hidden diversity on Earth may change how we search for life beyond Earth."
His Mino Fellowship project is SETI with microscopes: illuminating ‘dark genomic lineages’ with computational and optical methods.
Genesis Berlanga
Genesis Berlanga studies how planetary environments physically and chemically constrain the potential for life, and how scientists might identify those constraints beyond Earth.
His research focuses on the mineralogical and geochemical conditions that regulate water availability, chemical gradients and environmental stability. These factors help determine whether an environment is habitable.
Mars provides Berlanga with a natural laboratory for studying these processes. His work draws on laboratory experiments, terrestrial field sites that serve as Mars analogs and observations from spacecraft on Mars.
“I study other planets to better understand our own-to appreciate Earth's beauty, understand what makes it unique, and help protect it,” said Berlanga. “By following the water, we can broaden our search for extraterrestrial life and better understand our place in the universe. I'm excited to embark on that search with the SETI Institute.”
His Frank Drake Fellowship project, Coordination of lab, field, and Mars rover datasets and machine learning-assisted prediction of brine evolution and habitability metrics in Mars analog systems will bring together laboratory, field and Mars rover datasets and use machine learning to predict brine evolution and habitability in Mars analog environments.
Dingshan Deng
Dingshan Deng studies protoplanetary disks, the disks of gas and dust around young stars where planetary systems form.
His research focuses on how the physics and chemistry of these disks establish the initial conditions for planet formation and planetary atmospheres. He combines observations from ALMA and the James Webb Space Telescope with thermochemical modeling to study how planet-building materials are distributed and transported through disks.
Understanding the mass and composition of these disks can help scientists determine what material was available as planets formed, including the volatile compounds that can influence planetary composition, atmospheres and habitability.
His Frank Drake Fellowship project, Tracing Planet-building Materials from Gas to Ice with Self-Consistent Thermochemical Models, will develop physics- and chemistry-based models with AI and machine-learning tools to trace planet-building materials from molecular gas to icy solids and determine what is ultimately available to forming planets.
“I’m excited to join the SETI Institute and use the Frank Drake Fellowship to follow the journey of planet-building materials in protoplanetary disks to forming planets,” said Deng. “By understanding how these materials evolve, we will learn why planetary systems are so diverse and what conditions may ultimately allow habitable worlds to emerge.”
Postdoctoral Research at the SETI Institute
Benites, Berlanga and Deng join four other postdoctoral researchers at the SETI Institute.
The Frank Drake Postdoctoral Fellowship supports early-career scientists pursuing research connected to the questions embodied in the Drake Equation and the search for life in the universe.
The Mino Postdoctoral Fellowship supports cross-disciplinary research into the origins and nature of life, planetary habitability and the relationship between life and its environment.
“Supporting the next generation of scientists is an important part of what we do at the SETI Institute,” said Cabrol. “These fellowships give early-career researchers the opportunity to pursue ambitious ideas, work across disciplines and grow into independent scientists. By investing in them, we are also investing in the future of the questions we explore.”
Together, the Institute’s postdoctoral fellows work across a range of disciplines related to understanding life and its place in the universe.
About the SETI Institute Founded in 1984, the SETI Institute is a non-profit, multi-disciplinary research and education organization whose mission is to lead humanity’s quest to understand the origins and prevalence of life and intelligence in the Universe and to share that knowledge with the world. Our research encompasses the physical and biological sciences and leverages expertise in data analytics, machine learning and advanced signal detection technologies. The SETI Institute is a distinguished research partner for industry, academia and government agencies,
