Category: 7. Science

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

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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.

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