Category: 7. Science

A new study by the Genomics and Microbial Evolution Group at the Miguel Hernández University of Elche (UMH) together with the Department of Host-Microbe Interactions at St. Jude Children’s Research Hospital in Memphis, USA, sheds light on one of the great enigmas of microbiology: why only certain strains of common bacteria become pandemic pathogens. The work, published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS), focuses on Vibrio cholerae, the bacterium that causes cholera. It reveals that its most dangerous form arises from a specific combination of genes and allelic variants that give it an advantage in the human intestine. This research could pave the way for new strategies to predict and prevent future cholera outbreaks.

The study results from a collaboration between UMH researcher Mario López Pérez and Professor Salvador Almagro-Moreno of the St. Jude Children’s Research Hospital. It also involved UMH Professor José M. Haro Moreno and predoctoral researcher Alicia Campos López, affiliated with the Department of Plant Production and Microbiology.

Through an extensive analysis of over 1,840 Vibrio cholerae genomes, the researchers identified eleven distinct phylogenetic clusters, with the pandemic group belonging to the largest and located within a lineage shared with environmental strains. Their findings suggest that the emergence of pandemic strains, responsible for global cholera outbreaks, is largely dependent on the acquisition of unique modular gene clusters and allelic variations that confer a competitive advantage during intestinal colonization.. These act as nonlinear filters that prevent most environmental strains from becoming human pathogens.

As a result, only a small group of Vibrio cholerae strains can cause cholera in humans, despite the species’ vast natural diversity. We wondered why only this small subset has ever triggered pandemics.”

Mario López, UMH researcher, lead author of the study

The study reveals that the emergence of pandemic V. cholerae clones is constrained by specific genetic bottlenecks. These require: a genetic background pre-adapted for virulence, the acquisition of key gene clusters such as CTXΦ and VPI-1, their organization into specific modular arrangements, and finally, the presence of unique allelic variants. “Only when all these elements come together can a strain evolve into a pandemic-capable pathogen,” the researchers explain.

These features are absent in most environmental V. cholerae strains and appear to grant pandemic clones a key competitive advantage: enhanced ability to colonize the human gut.

“Interestingly, the genetic traits that enable V. cholerae to infect humans don’t benefit the bacteria in their natural aquatic environment,” López notes. In the wild, V. cholerae typically lives freely or in association with cyanobacteria colonies, mollusks, or crustaceans.

Cholera is endemic in parts of the world with poor water, sanitation, and hygiene infrastructure. Outbreaks can also occur after natural disasters that disrupt these systems. The disease is characterized by sudden, severe episodes of watery diarrhea, leading to rapid dehydration and, if untreated, potentially death.

“Our analytical model could be applied to other environmental bacteria to understand how pathogenic clones emerge from non-pathogenic populations,” López emphasizes. The study also opens the door to more precise surveillance of strains with pandemic potential-an approach that could be highly useful for future public health preparedness.

The research was supported by the U.S. National Science Foundation (NSF) through the CAREER program (#2045671) and by the Burroughs Wellcome Fund’s Investigator in the Pathogenesis of Infectious Disease program (#1021977). It also received funding from the Spanish “MICRO3GEN” project (PID2023-150293NB-I00), co-financed by the European Regional Development Fund (FEDER) and managed by the Spanish Ministry of Economy, Industry, and Competitiveness.

The study of the evolution of Martian atmosphere and its response to EUV irradiation is an extremely important topic in planetary science. One of the dominant effects of atmospheric losses is the photochemical escape of atomic oxygen from Mars.

Increasing the magnitude of the irradiation changes the response of the atmosphere. The purpose of the current paper is to analyze the effects of enhanced EUV irradiation on the escape rates of oxygen atoms.

We have used the solar flare of 2017 September 10 as the baseline flare intensity and varied the intensity of the flare from a factor of 3 up to 10 times the baseline flare. We see an increase in the escape flux by 40% for flares up to 5x the intensity of the baseline flare.

However, beyond this point, the increase in escape flux tapers off, reaching only about 17% above the baseline. At 10x the baseline flare intensity, the escape flux decreases by nearly 25% compared to the escape rate of the original flare. We also found that the total escape amount of hot O peaks at 7x the original flare intensity.

Additionally, we have studied the effects of the time scales over which the flare energy is delivered. We find that energy dissipative processes like radiative cooling and thermal collisions do not come into play instantaneously. The escape flux from higher intensity flares dominate initially, but as time progresses, energy dissipative processes have a significant effect on the escape rate.

Chirag Rathi, Dimitra Atri, Dattaraj B. Dhuri

Comments: 11 pages, 7 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2506.20337 [astro-ph.SR] (or arXiv:2506.20337v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2506.20337
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Related DOI:
https://doi.org/10.3847/PSJ/ade708
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Submission history
From: Chirag Rathi
[v1] Wed, 25 Jun 2025 11:48:01 UTC (1,141 KB)
https://arxiv.org/abs/2506.20337
Astrobiology,

For more than 20 years, NASA has relied on a network of spacecraft circling Mars to send data to and from the Red Planet. Without the constellation of five orbiters, the agency would not have been able to land its rovers on Mars or guide them through its terrain. Although the White House is keen on advancing human missions to the Martian surface, it also wants to get rid of that vital lifeline

The Mars Relay Network is a fleet of orbiters equipped with radio systems powered by the Sun to maintain regular contact with Earth. It’s an interconnected system that relays data between rovers and landers on the surface of Mars, transmitting it tens of millions of miles through space to radio antennas located on Earth. “Every image seen from the surface of Mars since 2004 has been transmitted through the Mars Relay Network,” according to NASA. The international orbital squad, which includes NASA’s Mars Odyssey, Mars Reconnaissance Orbiter, and MAVEN, and the European Space Agency’s Mars Express and ExoMars, would play a vital role in human missions to Mars. Three of them, however, are at risk of termination due to funding.

NASA is preparing for severe cuts under the White House’s proposed budget for 2026. The budget, released in May, highlights the administration’s “objectives of returning to the Moon before China and putting a man on Mars.” It also reduces NASA’s upcoming budget by $6 billion compared to 2025.

The impending cuts would significantly affect the budget for Mars-focused science missions, terminating funding for two of the NASA orbiters and one ESA spacecraft to recoup the cost of the network’s ongoing operations, Forbes reported. “We have not yet received direction from NASA HQ to stop work on these [Mars Relay] projects, and we wait for further instruction,” Roy Gladden, manager of the Mars Relay Network at NASA’s leading-edge Jet Propulsion Laboratory (JPL) in Pasadena, told Forbes.

Under the proposed budget, NASA’s planetary science budget would drop from $2.7 billion to $1.9 billion. On the other hand, the agency’s human space exploration budget received an additional $647 million compared to the 2025 budget. Judging by the allocation of funding, the administration is clearly failing to understand that ongoing science missions to Mars are crucial to achieving a human presence on the Red Planet.

The Mars Relay Network is part of NASA’s main infrastructure to communicate with Mars; decommissioning three of the orbiters would significantly reduce the network’s capacity. Given the complexity of the proposed first human missions to another planet, the communications network should be expanded to ensure precision and not the other way round.

It may be that the current administration would favor a commercial substitute to NASA’s Mars Relay Network. In late 2024, NASA revealed that it was studying proposals for communication networks to set up in Mars’ orbit, including a pitch by SpaceX for a Marslink constellation (similar to the company’s Starlink in Earth orbit). Either way, NASA would no doubt need to update its current Mars communications system to support human missions. It would make more sense, however, to give the agency more funding as it contemplates landing humans on another planet for the first time.

A mini solar telescope strapped to the side of the International Space Station (ISS) has captured its first images, revealing subtle changes in our home star’s outer atmosphere that have never been seen before.

NASA’s Coronal Diagnostic Experiment (CODEX) is a small solar telescope attached to the outside of the ISS. It is a coronagraph, meaning that it blocks out the solar disk to allow the telescope to focus on the sun’s atmosphere, or corona, in unprecedented detail — mimicking the way the moon blocks the sun’s visible surface during a total solar eclipse on Earth. The occulting disk blocking out the sun’s light is around the size of a tennis ball and it is held in place by three metal arms at the end of a long metal tube, which also cast distinctive shadows in the resulting images.

The planet Venus is like Earth’s worst twin – roughly the same size but with a thick layer of acid clouds over a crushing, hellish atmosphere. Its clouds in particular have been a source of interest, but it is difficult to understand how they change long-term: most missions around the planet don’t last long. New observations might have finally filled that gap in knowledge, thanks to weather satellites orbiting our planet that caught a glimpse of Venus accidentally.

The Himawari-8 and -9 satellites, launched in 2014 and 2016, are Japanese meteorological satellites. They were designed to study global atmospheric phenomena, something that they do well thanks to a particular type of instrument: multispectral Advanced Himawari Imagers (AHIs). This device can – when the alignment is right – capture Venus just at the edge of Earth.

A team from the University of Tokyo, led by visiting researcher Gaku Nishiyama, realized that the instrument would be able to measure variation in the temperature on top of the Venusian clouds. They collected data from 2015 to 2025, providing crucial monitoring of the nearby rocky planet.  

“The atmosphere of Venus has been known to exhibit year-scale variations in reflectance and wind speed; however, no planetary mission has succeeded in continuous observation for longer than 10 years due to their mission lifetimes,” Nishiyama said in a statement. “Ground-based observations can also contribute to long-term monitoring, but their observations generally have limitations due to the Earth’s atmosphere and sunlight during the daytime.” 

The team was able to find 437 occurrences of the alignment in total, and they were able to show that temperatures did indeed change across the 10 years. Such methods will be very useful for continuous monitoring of Venus before future missions get there, though, while the European EnVision mission to Venus is still scheduled for the next decade, NASA’s two missions to Venus are in jeopardy following the Trump administration’s cuts.

“We believe this method will provide precious data for Venus science because there might not be any other spacecraft orbiting around Venus until the next planetary missions around 2030,” said Nishiyama.

It might not just be a tool for Venus either. The team believes that they can use accidental photobombs in weather satellites to study other worlds of the Solar System. The advantage of orbital observations is the lack of atmosphere, which affects what we can do from the ground.

“I think that our novel approach in this study successfully opened a new avenue for long-term and multiband monitoring of solar system bodies. This includes the moon and Mercury, which I also study at present. Their infrared spectra contain various information on physical and compositional properties of their surface, which are hints at how these rocky bodies have evolved until the present,” added Nishiyama.

The study is published in the journal Earth, Planets and Space.

We reconsider the problem of planetary protection using, by the analogy of planets as islands, the theory of island biogeography.

We show that although the notion of equilibrium populations that emerge from the effects of immigration and extinction generally breaks down when applied to interplanetary scales, the mean-time to extinction resulting from the combined effects of growth and death rates can be quantified.

We reconsider the probabilistic model of planetary protection, discuss how mean-time to extinction can instead be used to assess contamination risk, and we propose a research direction for planetary protection based on these ideas.

We discuss more broadly the applicability of island biogeography to considering biotic transfer at interplanetary scales.

Rethinking planetary protection: an island biogeographical analysis, Journal of the Royal Society (open access)

Astrobiology, Planetary Protection,

HCl was detected in the Martian atmosphere by the NOMAD and ACS spectrometers aboard the ExoMars TGO. Photochemical models show that using gas-phase chemistry alone is insufficient to reproduce these data.

Recent work has developed a heterogeneous chemical network within a 1D photochemistry model, guided by the seasonal variability in HCl. The aim of this work is to show that incorporating heterogeneous chlorine chemistry into a global 3D model of Martian photochemistry with conventional gas-phase chemistry can reproduce spatial and temporal changes in hydrogen chloride on Mars. We incorporated this heterogeneous chlorine scheme into the MPCM to model chlorine photochemistry during MYs 34 and 35.

These two years provide contrasting dust scenarios, with MY 34 featuring a global dust storm. We also examined correlations in the model results between HCl and other key atmospheric quantities, as well as production and loss processes, to understand the impact of different factors driving changes in HCl.

We find that this 3D model of Martian is consistent with the changes in HCl observed by ACS in MY 34 and MY 35, including detections and 70% of non-detections. For the remaining 30%, model HCl is higher than the ACS detection limit due to biases associated with water vapour, dust, or water ice content at these locations.

As with previous 1D model calculations, we find that heterogeneous chemistry is required to describe the loss of HCl, resulting in a lifetime of a few sols that is consistent with the observed seasonal variation in HCl.

As a result of this proposed chemistry, modelled HCl is correlated with water vapour, airborne dust, and temperature, and anticorrelated with water ice. Our work shows that this chemical scheme enables the reproduction of aphelion detections in MY 35.

Benjamin Benne (1,2), Paul I. Palmer (1,2), Benjamin M. Taysum (3), Kevin S. Olsen (4,5), Franck Lefèvre (6) ((1) The University of Edinburgh, School of GeoSciences, UK, (2) Centre for Exoplanet Science, University of Edinburgh, UK, (3) DLR, Germany, (4) Department of Physics, University of Oxford, UK, (5) School of Physical Sciences, The Open University, UK, (6) LATMOS, France)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2506.18757 [astro-ph.EP] (or arXiv:2506.18757v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2506.18757
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Related DOI:
https://doi.org/10.1051/0004-6361/202553872
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Submission history
From: Benjamin Benne
[v1] Mon, 23 Jun 2025 15:28:45 UTC (2,899 KB)
https://arxiv.org/abs/2506.18757
Astrobiology

The Evolutionary Map of the Universe (EMU) survey with ASKAP is transforming our understanding of radio galaxies, AGN duty cycles, and cosmic structure.

EMUCAT efficiently identifies compact radio sources, yet struggles with extended objects, requiring alternative approaches.

The Radio Galaxy Zoo: EMU (RGZ EMU) project proposes a general framework that combines citizen science and machine learning to identify around 4 million extended sources in EMU.

This framework is expected to enhance the EMUCAT cataloging on extended sources and can be further empowered with the introduction of cross-matched external data from surveys such as POSSUM and WALLABY.

A schematic diagram showing the proposed RGZ EMU cataloging framework using citizen science and machine learning. The blue box (top left panel) shows sample images that are excluded from the final selection, as having either a low complexity or a source major axis smaller than 20 arcsec. Sample images in the red box, on the contrary, refers to sample images fulfilled our selection criteria. Gradient blue arrows refers to operation done within the framework, and gradient green arrows indicates the framework components that will contribute to the EMUCAT supplementary catalogs. — astro-ph.IM

Hongming Tang, Eleni Vardoulaki, RGZ EMU collaboration

Comments: 6 pages, 2 figures, The 2nd edition of the International Conference on Machine Learning for Astrophysics (ML4ASTRO2), conference paper accepted
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2506.16138 [astro-ph.IM] (or arXiv:2506.16138v1 [astro-ph.IM] for this version)
https://doi.org/10.48550/arXiv.2506.16138
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From: Hongming Tang
[v1] Thu, 19 Jun 2025 08:44:47 UTC (7,722 KB)
https://arxiv.org/abs/2506.16138
Astrobiology,

We present a near-infrared spectroscopic analysis (0.9-2.4 micron) of gravity indices for 57 ultracool dwarfs (spectral types M5.5 to L0), including exoplanet hosts TRAPPIST-1, SPECULOOS-2, SPECULOOS-3, and LHS 3154. Our dataset includes 61 spectra from the SpeX and FIRE spectrographs.

Using gravity-sensitive indices such as FeH absorption (at 0.99, 1.20, and 1.55 microns), the VO band at 1.06 microns, the H-band continuum, and alkali lines like K I (at 1.17 and 1.25 microns), we investigate correlations between surface gravity, stellar metallicity, and the presence of close-in transiting planets.

All four planet-hosting stars show intermediate-gravity spectral signatures despite indicators of field age. However, a volume-corrected logistic regression reveals no significant association between gravity class and planet occurrence. Among individual indices, FeH_z is the most promising tracer of planet-hosting status.

We tentatively identify a correlation between FeH_z (0.99 micron) and planet presence at the 2-sigma level, though this may reflect observational biases including transit probability, small-number statistics, and detection sensitivity. More robustly, we find a significant anti-correlation between FeH_z and metallicity ([Fe/H]) at 3.3 sigma. A Kruskal-Wallis test shows no significant metallicity difference across gravity classes, suggesting the observed FeH_z-metallicity trend is not driven by bulk metallicity differences.

We propose this anti-correlation reflects interplay between age, gravity, and composition: higher-metallicity objects may be systematically younger with lower gravities, suppressing FeH absorption. While our results only hint at a link between gravity-related characteristics and planet occurrence among late-M dwarfs, they underscore the need for caution when using spectral diagnostics to infer properties of planet-hosting ultracool dwarfs.

Fatemeh Davoudi, Benjamin V. Rackham, Julien de Wit, Jan Toomlaid, Michaël Gillon, Amaury H. M. J. Triaud, Adam J. Burgasser, Christopher A. Theissen

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2506.19928 [astro-ph.EP] (or arXiv:2506.19928v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2506.19928
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From: Fatemeh Davoudi
[v1] Tue, 24 Jun 2025 18:05:48 UTC (2,086 KB)
https://arxiv.org/abs/2506.19928
Astrobiology