SPACE/COSMOS
‘Space ice’ is less like water than we thought
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Visual representation of the structure of low-density amorphous ice. Many tiny crystallites (white) are concealed in the amorphous material (blue).
view moreCredit: Credit: Michael B Davies, UCL and University of Cambridge
“Space ice” contains tiny crystals and is not, as previously assumed, a completely disordered material like liquid water, according to a new study by scientists at UCL (University College London) and the University of Cambridge.
Ice in space is different to the crystalline (highly ordered) form of ice on Earth. For decades, scientists have assumed it is amorphous (without a structure), with colder temperatures meaning it does not have enough energy to form crystals when it freezes.
In the new study, published in Physical Review B, researchers investigated the most common form of ice in the Universe, low-density amorphous ice, which exists as the bulk material in comets, on icy moons and in clouds of dust where stars and planets form.
They found that computer simulations of this ice best matched measurements from previous experiments if the ice was not fully amorphous but contained tiny crystals (about three nanometres wide, slightly wider than a single strand of DNA) embedded within its disordered structures.
In experimental work, they also re-crystallised (i.e. warmed up) real samples of amorphous ice that had formed in different ways. They found that the final crystal structure varied depending on how the amorphous ice had originated. If the ice had been fully amorphous (fully disordered), the researchers concluded, it would not retain any imprint of its earlier form.
Lead author Dr Michael B. Davies, who did the work as part of his PhD at UCL Physics & Astronomy and the University of Cambridge, said: “We now have a good idea of what the most common form of ice in the Universe looks like at an atomic level.
“This is important as ice is involved in many cosmological processes, for instance in how planets form, how galaxies evolve, and how matter moves around the Universe.”
The findings also have implications for one speculative theory about how life on Earth began. According to this theory, known as Panspermia, the building blocks of life were carried here on an ice comet, with low-density amorphous ice the space shuttle material in which ingredients such as simple amino acids were transported.
Dr Davies said: “Our findings suggest this ice would be a less good transport material for these origin of life molecules. That is because a partly crystalline structure has less space in which these ingredients could become embedded.
“The theory could still hold true, though, as there are amorphous regions in the ice where life’s building blocks could be trapped and stored.”
Co-author Professor Christoph Salzmann, of UCL Chemistry, said: “Ice on Earth is a cosmological curiosity due to our warm temperatures. You can see its ordered nature in the symmetry of a snowflake.
“Ice in the rest of the Universe has long been considered a snapshot of liquid water – that is, a disordered arrangement fixed in place. Our findings show this is not entirely true.
“Our results also raise questions about amorphous materials in general. These materials have important uses in much advanced technology. For instance, glass fibers that transport data long distances need to be amorphous, or disordered, for their function. If they do contain tiny crystals and we can remove them, this will improve their performance.”
For the study, the researchers used two computer models of water. They froze these virtual “boxes” of water molecules by cooling to -120 degrees Centigrade at different rates. The different rates of cooling led to varying proportions of crystalline and amorphous ice.
They found that ice that was up to 20% crystalline (and 80% amorphous) appeared to closely match the structure of low-density amorphous ice as found in X-ray diffraction studies (that is, where researchers fire X-rays at the ice and analyse how these rays are deflected).
Using another approach, they created large “boxes” with many small ice crystals closely squeezed together. The simulation then disordered the regions between the ice crystals reaching very similar structures compared to the first approach with 25% crystalline ice.
In additional experimental work, the research team created real samples of low-density amorphous ice in a range of ways, from depositing water vapour on to an extremely cold surface (how ice forms on dust grains in interstellar clouds) to warming up what is known as high-density amorphous ice (ice that has been crushed at extremely cold temperatures).
The team then gently heated these amorphous ices so they had the energy to form crystals. They noticed differences in the ices’ structure depending on their origin - specifically, there was variation in the proportion of molecules stacked in a six-fold (hexagonal) arrangement.
This was indirect evidence, they said, that low-density amorphous ice contained crystals. If it was fully disordered, they concluded, the ice would not retain any memory of its earlier forms.
The research team said their findings raised many additional questions about the nature of amorphous ices – for instance, whether the size of crystals varied depending on how the amorphous ice formed, and whether a truly amorphous ice was possible.
Amorphous ice was first discovered in its low-density form in the 1930s when scientists condensed water vapour on a metal surface cooled to -110 degrees Centigrade. Its high-density state was discovered in the 1980s when ordinary ice was compressed at nearly -200 degrees Centigrade.
The research team behind the latest paper, based both at UCL and the University of Cambridge, discovered medium-density amorphous ice in 2023. This ice was found to have the same density as liquid water (and would therefore neither sink nor float in water).
Co-author Professor Angelos Michaelides, from the University of Cambridge, said: “Water is the foundation of life but we still do not fully understand it. Amorphous ices may hold the key to explaining some of water’s many anomalies.”
Dr Davies said: “Ice is potentially a high-performance material in space. It could shield spacecraft from radiation or provide fuel in the form of hydrogen and oxygen. So we need to know about its various forms and properties.”
An enhanced image of the Jovian moon Ganymede was obtained by the JunoCam imager aboard NASA's Juno spacecraft during the mission's June 7, 2021, flyby of the icy moon on Juno's 34th pass close to Jupiter.
Credit
NASA/JPL-Caltech/SwRI/MSSS/Kalleheikki Kannisto
Journal
Physical Review B
Exoplanet Sparks Stellar Fireworks
Scientists have discovered the first clear case of a planet causing its host star to flare, offering new insights into the dramatic interactions between stars and their closely orbiting planets. The research was led by Dr. Ekaterina Ilin and Dr. Harish K. Vedantham of ASTRON (Netherlands Institute for Radio Astronomy), as well as Prof. Dr. Katja Popppenhäger from AIP, along with an international team of collaborators.
The study focused a young star system HIP 67522, which is located around 408 light years away in the constellation of Upper Centaurus Lupus. In one of the closest known orbits, a giant planet passes its star in less than seven days. The team led by Ekaterina Ilin has discovered that stellar flares frequently erupt at the moments when the planet passes in front of the star from our perspective. These huge eruptions of electromagnetic energy and flares seem to be triggered directly by the planet’s influence.
“We’ve found the first clear evidence of flaring star-planet interaction, where a planet triggers energetic eruptions on its host star,” said Ekaterina Ilin. “What’s particularly exciting is that this interaction has persisted for at least three years, allowing us to study it in detail.”
The analysis is based on five years of data from NASA’s TESS satellite and the European Space Agency’s CHEOPS telescope. In their study, the astronomers show that the planet releases energy by disturbing the magnetic field lines of its star, which discharges explosively – a veritable ‘firework display’ in space. “This type of star-planet interaction has been expected for a long time, but getting the observational evidence was only possible with this large space telescope dataset”, said Katja Poppenhäger.
This interplanetary interaction also has dramatic effects on the planet itself: The findings show that the planet induces the star to flare approximately six times more often than it would have without the interaction. Data from the James Webb Space Telescope shows a unusually expanded atmosphere – a possible result of the intense bursts of radiation. “The planet is essentially subjecting itself to an intense bombardment of radiation and particles from these induced flares,” explained Harish K. Vedantham, co-author and researcher at ASTRON. “This self-inflicted space weather likely causes the planet’s atmosphere to puff up and may dramatically accelerate the rate at which the planet is losing its atmosphere.”
This discovery establishes HIP 67522 as an archetypal system for studying how magnetic interactions between stars and planets can affect planetary evolution, particularly for young planets. The team plans further observations of this and other systems to better understand how energy is transported and released along the planet-star connection, how common this phenomenon is among young planetary systems and what it means for the ability of young planets to retain their nascent atmospheres.
International Gemini Observatory and SOAR discover surprising link between fast X-ray transients and the explosive death of massive stars
Unprecedented study of closest supernova associated with a fast X-ray transient presents a breakthrough in astronomy’s understanding of how stars larger than our Sun explode
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This sequence of images shows the fading light of the supernova SN 2025kg, which followed the fast X-ray transient EP 250108a, a powerful blast of X-rays that was detected by Einstein Probe (EP) in early 2025. Using a combination of telescopes, including the International Gemini Observatory, funded in part by the U.S. National Science Foundation and operated by NSF NOIRLab, and the SOAR telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF NOIRLab, a team of astronomers studied the evolving signal of EP 250108a/SN 2025kg to uncover details about its origin. Their analysis reveals that fast X-ray transients can result from the ‘failed’ explosive death of a massive star.
view moreCredit: International Gemini Observatory/NOIRLab/NSF/AURA Acknowledgment: PI: J. Rastinejad (Northwestern University) Image processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), M. Zamani (NSF NOIRLab)
Since their first detection, powerful bursts of X-rays from distant galaxies, known as fast X-ray transients (FXTs), have mystified astronomers. FXTs have historically been elusive events, occurring at vast distances away from Earth and only lasting seconds to hours. Einstein Probe (EP), launched in 2024, is dedicated to observing transient events in the X-ray and is changing the game for astronomers looking to understand the origin of these exotic events.
In January 2025 EP alerted astronomers to the nearest FXT known at the time, named EP 250108a. Its proximity to Earth (2.8 billion light-years away) provided an unprecedented opportunity for detailed observations of the event’s evolving behavior.
After the initial detection of EP 250108a, a large, international team of astronomers jumped into action to capture its signal in multiple wavelengths. The FLAMINGOS-2 spectrograph on the Gemini South telescope, one half of the International Gemini Observatory, provided near-infrared data, while the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope provided optical. Gemini’s rapid response capabilities allowed the team to quickly point to the location of EP 250108a where they found the shining aftermath of the explosive death of a massive star, known as a supernova.
Through analysis of EP 250108a’s rapidly evolving signal over the first six days following initial detection, the team found that this FXT is likely a ‘failed’ variation of a gamma-ray burst (GRB). GRBs are the most powerful explosions in the Universe and have been observed preceding supernovae. During these events, violent geysers of high-energy particles burst through a star’s outer layers as it collapses in on itself. These jets flow at nearly the speed of light and are detectable by their gamma-ray emission.
EP 250108a appears similar to a jet-driven explosion, but one in which the jets do not break through the outer layers of the dying star and instead remain trapped inside. As the stifled jets interact with the star’s outer layers, they decelerate and their kinetic energy is converted to the X-rays detected by Einstein Probe.
“This FXT supernova is nearly a twin of past supernovae that followed GRBs,” says Rob Eyles-Ferris, a postdoctoral researcher at the University of Leicester and lead author of one of two companion papers presenting these results, to appear in The Astrophysical Journal Letters. “Our observations of the early stages of EP 250108a’s evolution show that the explosions of massive stars can produce both phenomena.”
While these early-stage observations provide insight into the mechanisms driving the FXT, longer-term monitoring of the event is necessary to piece together the characteristics of the progenitor star. So the team continued observing EP 250108a beyond the first six days, watching as the emission from the trapped jet faded and the optical signal from its associated supernova, SN 2025kg, dominated the spectra.
“The X-ray data alone cannot tell us what phenomena created the FXT,” says Jillian Rastinejad, PhD student at Northwestern University and lead author of the second companion paper. “Our optical monitoring campaign of EP 250108a was key to identifying the aftermath of the FXT and assembling the clues to its origin.”
At the location of EP 250108a, the team observed a rise in optical brightness that lasted a few weeks before fading, along with spectra containing broad absorption lines. These characteristics indicate that the FXT is associated with a Type Ic broad-lined supernova.
Near-infrared observations from the 4.1-meter Southern Astrophysical Research (SOAR) Telescope at NSF Cerro Tololo Inter-American Observatory (CTIO) in Chile further helped to constrain the supernova’s peak brightness, offering more clues as to what the progenitor star looked like. The team estimates that the star whose death ignited EP 250108a and its associated supernova had a mass of about 15–30 times that of the Sun.
“Our analysis shows definitively that FXTs can originate from the explosive death of a massive star,” says Rastinejad. “It also supports a causal link between GRB-supernovae and FXT-supernovae, in which GRBs are produced by successful jets and FXTs are produced by trapped or weak jets.”
Together, the team’s companion papers present the most detailed dataset to date of a supernova accompanying an EP FXT. Their combined analysis indicates that ‘failed’ jets associated with FXTs are more common in massive star explosions than ‘successful’ jets associated with GRBs. Since the launch of EP, FXTs have been detected several times each month. Meanwhile, GRB detections have historically been sparse, occurring roughly once per year.
“This discovery heralds a broader understanding of the diversity in massive stars’ deaths and a need for deeper investigations into the whole landscape of stellar evolution,” says Eyles-Ferris.
Astronomers’ understanding of stars will be significantly expanded upon by the upcoming NSF–DOE Vera C. Rubin Observatory, funded by the NSF and the U.S. Department of Energy’s Office of Science (DOE/SC). Its decade-long Legacy Survey of Space and Time (LSST) will provide astronomers with immense amounts of detailed time-domain data on stellar explosions, revealing the internal workings of FXTs and many other exotic stellar events.
“The International Gemini Observatory combines rapid response capabilities with world-leading sensitivity to faint, distant sources,” says Martin Still, NSF program director for the International Gemini Observatory. “This optimizes Gemini to be a premier follow-up machine for explosive event alerts from gravitational wave and particle detectors, space-borne surveys, and the upcoming Legacy Survey of Space and Time by the NSF-DOE Vera C. Rubin Observatory.”
More information
This research was presented in the companion papers: “The kangaroo's first hop: the early fast cooling phase of EP250108a/SN 2025kg” and “EP 250108a/SN 2025kg: Observations of the most nearby Broad-Line Type Ic Supernova following an Einstein Probe Fast X-ray Transient,” both to appear in The Astrophysical Journal Letters.
The teams are composed of: R. A. J. Eyles-Ferris (University of Leicester), P. G. Jonker (Radboud University), A. J. Levan (Radboud University), et al.; J. C. Rastinejad (Northwestern University), A. J. Levan (Radboud University), P. G. Jonker (Radboud University) et al.
NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.
The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.
The Southern Astrophysical Research (SOAR) Telescope is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTIC/LNA), NSF NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).
Links
- Read the paper: The kangaroo's first hop: the early fast cooling phase of EP250108a/SN 2025kg
- Read the paper: EP 250108a/SN 2025kg: Observations of the most nearby Broad-Line Type Ic Supernova following an Einstein Probe Fast X-ray Transient
- Photos of the Gemini South telescope
- Videos of the Gemini South telescope
- Photos of Gemini North
- Videos of Gemini North
- Photos of SOAR
- Videos of SOAR
- Check out other NOIRLab Science Releases
Journal
The Astrophysical Journal Letters
This image shows the cosmic field in which the fast X-ray transient EP 250108a, and the supernova that followed it, were detected by Einstein Probe (EP) in early 2025. Using a combination of telescopes, including the International Gemini Observatory, funded in part by the U.S. National Science Foundation and operated by NSF NOIRLab, and the SOAR telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF NOIRLab, a team of astronomers studied the evolving signal of EP 250108a/SN 2025kg to uncover details about its origin. Their analysis reveals that fast X-ray transients can result from the ‘failed’ explosive death of a massive star.
Credit
International Gemini Observatory/NOIRLab/NSF/AURA Acknowledgment: PI: J. Rastinejad (Northwestern University) Image processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), M. Zamani (NSF NOIRLab)
VIDEO
Cosmoview Episode 100: International Gemini Observatory and SOAR Discover
Using a combination of telescopes, including the International Gemini Observatory, funded in part by the U.S. National Science Foundation and operated by NSF NOIRLab, and the SOAR telescope at Cerro Tololo Inter-American Observatory in Chile, a Program of NSF NOIRLab, astronomers have characterized the closest supernova linked to a fast X-ray transient. The observations reveal that these bright blasts of X-rays may be the result of a ‘failed’ explosive death of a massive star.
Credit
International Gemini Observatory/CTIO/NOIRLab/NSF/AURA/NASA’s Goddard Space Flight Center Image processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), M. Zamani (NSF NOIRLab) Acknowledgment: PI: J. Rastinejad (Northwestern University) Motion graphics: Mik Garrison Music: Fundamental Uncertainty - Mik Garrison
Fluid-structure interaction analysis and wave-coupled dynamics of airbag-cushioned reentry capsules: Unlocking safer maritime spacecraft recovery?
Tsinghua University Press
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The dynamic response of the capsule-airbags system during interaction with both regular and irregular waves at Ux=12m/s is systematically analyzed across three characteristic phases: initial impact, peak overload, and stabilization. Results demonstrate a pronounced tendency for capsule capsizing at this horizontal velocity.
view moreCredit: Chinese Journal of Aeronautics
As global interest in reusable spacecraft and crewed deep-space exploration surges, ensuring the safe recovery of spacecraft in complex maritime environments has become a critical challenge. A groundbreaking study led by researchers from Nanjing University of Aeronautics and Astronautics, published in the Chinese Journal of Aeronautics on June 6, 2025, has systematically decoded the water-landing characteristics of reentry capsules equipped with airbag cushioning systems under wave conditions using a fluid-structure interaction (FSI) model. This research not only provides a scientific foundation for optimizing spacecraft recovery design but also establishes a technical cornerstone for the safety of future crewed missions.
Spacecraft recovery is the “final mile” of crewed space missions, directly impacting personnel safety and equipment integrity. Compared to land recovery, maritime recovery—with its lower impact forces (36% of land impacts), enhanced safety in unpopulated areas, and vast landing flexibility—is the preferred method for crewed missions. However, the complex interactions between reentry capsules and waves, as well as the coupling effects of airbag cushioning and hydrodynamic forces, have long been engineering blind spots.
“With the rise of commercial aerospace and reusable technologies, airbag cushioning systems, such as those on Boeing’s CST-100 and the Orion spacecraft, are widely adopted to mitigate impact forces. Yet prior studies focused on land or calm-water scenarios, leaving the mechanisms of capsule-airbag-wave interactions in real ocean environments poorly understood,” emphasized Dr. Yang Zhang, corresponding author of the study and an associate researcher at the College of Astronautics, Nanjing University of Aeronautics and Astronautics. “Failure to accurately predict impact loads under wave conditions could lead to structural damage or even mission failure.”
The team developed a high-fidelity FSI model integrating fluid dynamics (ALE method), airbag dynamics (control volume method), and wave coupling, and uncovered the following pivotal mechanisms:
- Speed control & angle adjustment ensure stability. At medium speeds (8-10 m/s), airbags stabilize the capsule when paired with optimal tilt angles. However, high speeds (16 m/s) risk capsizing even with airbags, requiring strict speed limits.
- Vertical speed drives impact; attitude angle reduces force. Vertical velocity is the main contributor to peak impact forces, while horizontal speed has minimal effect. Increasing attitude angles cuts impact forces by over 30%.
- Wave troughs pose highest risk; design for chaos. Wave troughs generate 40% higher impacts than crests. Systems must withstand both predictable regular waves and chaotic irregular waves, especially at higher speeds.
“These findings subvert traditional design paradigms dominated by calm-water assumptions,” Dr. Zhang stressed. “The randomness of real-world ocean waves must be integrated into recovery system designs.”
While the study marks a milestone, the team acknowledges limitations: turbulence effects are unaccounted for, and model accuracy requires enhancement through integration of drop-test data. Next, the team will collaborate with space agencies to conduct maritime airdrop trials, establishing a “simulation-testing” validation loop.
“In the era of deep-space exploration, safe recovery is the ‘lifeline’ of crewed missions. We hope this work adds certainty to humanity’s journey to the stars. Our ultimate goal is to develop an intelligent recovery system adaptive to wave environments,” Dr. Zhang revealed. “By real-time sensing of wave phases and capsule dynamics, we aim to dynamically adjust airbag pressure and landing trajectories to keep impact forces within safety thresholds.”
Other contributors include Shiqing Wu, Jiangli Lei, Wei Huang, Huai Xie from Beijing Institute of Space Mechanics and Electricity in Beijing, China.
Original Source
Jiapeng HAN, Shiqing WU, Jiangli LEI, Wei HUANG, Huai XIE, Yang ZHANG. Numerical study on water landing characteristics of a reentry capsule with airbag cushioning under calm water and regular/irregular waves [J]. Chinese Journal of Aeronautics, 2025, https://doi.org/10.1016/j.cja.2025.103615.
About Chinese Journal of Aeronautics
Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.7, Q1), EI, IAA, AJ, CSA, Scopus.
Journal
Chinese Journal of Aeronautics
Article Title
Numerical study on water landing characteristics of a reentry capsule with airbag cushioning under calm water and regular/irregular waves
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