Category: 7. Science

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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Submission history
From: Fatemeh Davoudi
[v1] Tue, 24 Jun 2025 18:05:48 UTC (2,086 KB)
https://arxiv.org/abs/2506.19928
Astrobiology

The National Radio Astronomy Observatory is a facility of the U.S. National Science Foundation
operated under cooperative agreement by Associated Universities, Inc. Founded in 1956, the NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.

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AUI collaborates with the scientific community and research sponsors to plan, build, and operate cutting-edge facilities. We cultivate excellence, deliver value, enhance education, and engage the public.

Scientists are claiming a “cosmic chemistry breakthrough” following the discovery of a large “aromatic” molecule in deep space. The discovery suggests that these molecules could help seed planetary systems with carbon, supporting the development of molecules needed for life.

The molecule, called cyanocoronene, belongs to a class of carbon-based organic compounds called polycyclic aromatic hydrocarbons (PAHs), which are made up of multiple fused aromatic rings — structures in which electrons are shared across double-bonded carbon atoms, giving them unique chemical stability.

In these polar waters, cold, fresh surface water overlays warmer, saltier waters from the deep. In the winter, as the surface cools and sea ice forms, the density difference between water layers weakens, allowing these layers to mix and heat to be transported upward, melting the sea ice from below and limiting its growth.

Since the early 1980s, the surface of the Southern Ocean had been freshening, and stratification – that density difference between the water layers – had been strengthening. This was trapping heat below and sustaining more sea ice coverage.

Now, new satellite technology, combined with information from floating robotic devices which travel up and down the water column, shows this trend has reversed; surface salinity is increasing, stratification is weakening, and sea ice has reached multiple record lows – with large openings of open ocean in the sea ice (polynyas) returning.

This is the first time scientists have been able to monitor these changes in the Southern Ocean in real time. 

Aditya Narayanan, a postdoctoral research fellow at the University of Southampton and co-author on the paper, said: “While scientists expected that human-driven climate change would eventually lead to Antarctic Sea ice decline, the timing and nature of this shift remained uncertain.

“Previous projections emphasised enhanced surface freshening and stronger ocean stratification, which could have supported sustained sea ice cover. Instead, a rapid reduction in sea ice – an important reflector of solar radiation – has occurred, potentially accelerating global warming.”

What this all means is that – according to Professor Alberto Naveira Garabato, co-author on the study and Regius Professor of Ocean Sciences at the University of Southampton – our current understanding “may be insufficient” to accurately predict future changes.

“It makes the need for continuous satellite and in-situ monitoring all the more pressing, so we can better understand the drivers of recent and future shifts in the ice-ocean system.”

The paper – ‘Rising surface salinity and declining sea ice: a new Southern Ocean state revealed by satellites is published in Proceedings of the National Academy of Sciences and is available online.

This project has been supported by the European Space Agency.

Click here for more from the Oceanographic Newsroom.

Extreme environments impose strong mutation and selection pressures that drive distinctive, yet understudied, genomic adaptations in extremophiles.

In this study, we identify 15 bacterium–archaeon pairs that exhibit highly similar k-mer–based genomic signatures despite maximal taxonomic divergence, suggesting that shared environmental conditions can produce convergent, genome-wide patterns that transcend evolutionary distance. To uncover these patterns, we developed a computational pipeline to select a composite genome proxy assembled from non-contiguous subsequences of the genome.

Using supervised machine learning on a curated dataset of 693 extremophile microbial genomes, we found that 6-mers and 100 kbp genome proxy lengths provide the best balance between classification accuracy and computational efficiency. Our results provide conclusive evidence of the pervasive nature of k-mer–based patterns across the genome, and uncover the presence of taxonomic and environmental components that persist across all regions of the genome.

The 15 bacterium-archaeon pairs identified by our method as having similar genomic signatures were validated through multiple independent analyses, including 3-mer frequency profile comparisons, phenotypic trait similarity, and geographic co-occurrence data. These complementary validations confirmed that extreme environmental pressures can override traditionally recognized taxonomic components at the whole-genome level.

Together, these findings reveal that adaptation to extreme conditions can carry robust, taxonomic domain-spanning imprints on microbial genomes, offering new insight into the relationship between environmental mutagenesis and selection and genome-wide evolutionary convergence.

Life at the extremes: Maximally divergent microbes with similar genomic signatures linked to extreme environments, biorxiv.org

Astrobiology

The totality of bacteria, viruses and fungi that exist in and on a multicellular organism forms its natural microbiome. The interactions between the body and these microorganisms significantly influence both, the functions and health of the host organism. Researchers assume that the microbiome plays an important role in the defence against pathogens, among other things. The Collaborative Research Centre (CRC) 1182 “Origin and Function of Metaorganisms” at Kiel University has been investigating the highly complex interplay between host organisms and microorganisms for several years using various model organisms, including the nematode Caenorhabditis elegans.

In a recent study, researchers from the CRC 1182 have gained new insights into the molecular mechanisms within the microbiome which contribute to the defence against pathogens. In collaboration with scientists from the Max Planck Institute for Terrestrial Microbiology and the University of Edinburgh, they discovered that a protective bacterium of the genus Pseudomonas, which is found in the intestinal microbiome of C. elegans, produces sphingolipids. This result was surprising, as it was previously assumed that the production of sphingolipids was restricted to only a few bacterial phyla and the bacterial genus Pseudomonas was not known to be able to produce these specific molecules. The researchers discovered that Pseudomonas utilises an alternative metabolic pathway for sphingolipid production, which differs significantly from the known sphingolipid synthesis pathways in other bacteria. They were also able to show that the sphingolipids produced by Pseudomonas bacteria play an essential role in protecting the intestinal epithelium of the host from damage by the pathogen.

Responsible for sphingolipid production in Pseudomonas bacteria is a specific biosynthetic gene cluster that forms the enzymes for this novel metabolic pathway. Interestingly, similar gene clusters were also found in other host-associated gut bacteria, suggesting that the ability to produce sphingolipids may be more widespread than previously thought. This suggests that bacterial sphingolipids may play a central role in microbiome-mediated protection against infection – not only in C. elegans, but potentially also in other host organisms. The results of the interdisciplinary study, conducted under the leadership of PD Dr Katja Dierking (Evolutionary Ecology and Genetics research group at Kiel University), in collaboration with other research groups from Kiel and national and international cooperation partners, were recently published in the journal Nature Communications.

Bacteria use alternative pathway to produce protective sphingolipids

A few years ago, the Kiel research group had already published a study (Kissoyan et al. (2019), Current Biology) that showed that certain members of the C. elegans microbiota protect against pathogen infection.  “For one Pseudomonas species we knew that it can protect the worm from infections. However, we had not yet been able to identify the substances and mechanisms involved,” emphasises Dr Lena Peters, a scientist in the Evolutionary Ecology and Genetics research group.

In a broad-based collaboration of scientists both within the CRC 1182 – including Kiel professors Christoph Kaleta and Manuel Liebeke – and with external scientists, including Professor Helge Bode from the MPI for Terrestrial Microbiology in Marburg and Professor Dominic Campopiano from the University of Edinburgh in Scotland, the genetic and metabolic basis of the protection against infection mediated by the microbiome was analyzed. Using metabolic and transcriptional studies, single molecule analyses and mass spectrometry approaches, the researchers made a surprising discovery: they were able to prove that the protective bacteria of the genus Pseudomonas produce sphingolipids that influence the worm’s sphingolipid metabolism and thus support the host’s protection against pathogens.

“This finding is relatively new,” explains Peters, member of the CRC 1182, “normally, bacteria use the sphingolipid metabolism of host organisms to manipulate it in a targeted manner to promote infections. In our case, however, we observe the opposite – bacterial sphingolipids apparently actively support the protection of the host.” Sphingolipids are fat-like molecules that are typically found in eukaryotes, where they fulfil important structural and regulatory functions, but are rare in bacteria. In Pseudomonas, they are synthesised via a previously unknown, alternative metabolic pathway – not as a component of primary metabolism, as is usually the case, but as a so-called secondary metabolite.

The researchers discovered that this previously unknown metabolic pathway is based on a specific biosynthetic gene cluster, a so-called polyketide synthase. “With our experiments, we were able to confirm that the worms survived better in the presence of Pseudomonas fluorescens bacteria possessing this gene cluster when they were infected with the pathogen Bacillus thuringiensis,” emphasises Peters, first author of the study. After identifying the responsible genes, the scientists could confirm through further analyses that the gene cluster encodes the enzymes required for sphingolipid synthesis. “It is exciting to be authors on this important, breakthrough paper. We are pleased that our expertise in bacterial sphingolipid research has helped discover a new role in the worm microbiome for these enigmatic lipids,” says Prof. Campopiano.

“The protective mechanism against infections with B. thuringiensis apparently works indirectly. The lipids produced by Pseudomonas influence the worm’s sphingolipid metabolism, which presumably leads to an improved barrier function of the intestinal cells,” explains Peters. When the worm is infected with B. thuringiensis, the toxins of the pathogen create small pores in the cell membrane of the host, which makes it easier for the pathogens to penetrate. “We assume that the sphingolipid metabolism modified by P. fluorescens strengthens the stability and resistance of the cell membranes – and thus offers effective, indirect protection against pathogens,” Peters continues.

“Overall, the new research work expands our understanding of how microbial metabolites support host defence against pathogens,” says Dierking, independent group leader in the Evolutionary Ecology and Genetics research group. In the long term, the researchers of the CRC 1182, who are also active in Kiel University’s priority research area Kiel Life Science (KLS), hope that better knowledge of such fundamental mechanisms will also make it possible to influence disorders of the human gut microbiome which may result in better treatment options for a variety of associated diseases.

Reference: Peters L, Drechsler M, Herrera MA, et al. Polyketide synthase-derived sphingolipids mediate microbiota protection against a bacterial pathogen in C. elegans. Nat Commun. 2025;16(1):5151. doi: 10.1038/s41467-025-60234-1

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After nearly two decades in orbit, NASA’s Mars Reconnaissance Orbiter (MRO) is trying something new.

Engineers have taught the spacecraft how to roll – hard. This isn’t just a simple tilt. These are full-body rolls, sometimes nearly upside down.

The purpose is to see deeper beneath the surface of Mars and hunt for signs of water and ice.

Teaching Mars Orbiter to roll

The new technique comes from scientists at the Planetary Science Institute and NASA’s Jet Propulsion Laboratory.

Between 2023 and 2024, MRO performed three massive rotations – what the team calls “very large rolls” – to boost the performance of one of its key instruments.

“Not only can you teach an old spacecraft new tricks, you can open up entirely new regions of the subsurface to explore by doing so,” said Gareth Morgan of the Planetary Science Institute in Tucson, Arizona.

Advanced planning and careful balance

Mars Reconnaissance Orbiter was originally built to roll up to 30 degrees to aim its cameras and sensors at specific features on the Martian surface.

It’s a flexible platform, designed to twist and turn in space so scientists can target impact craters, landing zones, and more.

“We’re unique in that the entire spacecraft and its software are designed to let us roll all the time,” said Reid Thomas, MRO’s project manager at NASA’s Jet Propulsion Laboratory in Southern California.

But the bigger rolls – 120 degrees or more – are something else entirely. These require advanced planning and careful balance.

Mars Orbiter: Why every roll counts

MRO’s five main science instruments all have different needs. When one is pointed at Mars, others might lose their ideal view.

That means every maneuver is scheduled weeks in advance. Teams negotiate which instruments will be active and when.

An algorithm takes over from there, guiding the orbiter to roll and aim while keeping its solar panels locked on the Sun and its antenna aimed at Earth. For very large rolls, even those systems go dark temporarily.

“The very large rolls require a special analysis to make sure we’ll have enough power in our batteries to safely do the roll,” Thomas said.

Flipping for stronger radar returns

The massive rolls are especially helpful for SHARAD, the Shallow Radar instrument on board. It is designed to see about half a mile to 1.2 miles (0.8 – 1.9 kilometers) below the Martian surface.

SHARAD can also differentiate between ice, rock, and sand – a crucial capability for identifying water that future astronauts might one day use.

“The SHARAD instrument was designed for the near-subsurface, and there are select regions of Mars that are just out of reach for us,” said Morgan. “There is a lot to be gained by taking a closer look at those regions.”

Normally, SHARAD’s signals bounce off parts of the orbiter before hitting Mars, which muddies the data. But by flipping the spacecraft 120 degrees, SHARAD gets a clean line of sight. That single move boosts signal strength tenfold or more.

This improvement is big, but it comes with tradeoffs. During the maneuver, MRO can’t communicate with Earth or recharge its batteries. That limits the team to one or two very large rolls each year – for now.

Old instruments with new tricks

SHARAD isn’t the only instrument adjusting to new routines. The Mars Climate Sounder, a radiometer built at JPL, is also leaning into MRO’s roll capability. It tracks temperatures and atmospheric changes on Mars, revealing patterns in dust storms and cloud formations.

Originally, this instrument used a gimbal to adjust its view. But the gimbal started to fail in 2024. Now, the Climate Sounder depends on the orbiter’s roll maneuvering instead.

“Rolling used to restrict our science, but we’ve incorporated it into our routine planning, both for surface views and calibration,” said Mars Climate Sounder’s interim principal investigator, Armin Kleinboehl of JPL.

Mars Orbiter still delivers after 18 years

NASA’s Mars Reconnaissance Orbiter has been circling the Red Planet since 2006. It’s an aging but incredibly capable machine.

These new rolling maneuvers show that even after 18 years in space, it’s still finding new ways to contribute.

By shifting its body in bold new directions, MRO is helping us see what lies beneath the Martian dust – and just maybe, where water waits to be found.

Image Credit: NASA/JPL-Caltech

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