Category: 7. Science

Due to extreme temperatures and the dryness of Mars, it’s thought to be impossible for liquid water to form on the planet’s surface, a critical precondition for habitability. The only hope of finding liquid water appears to be in the form of brines, which are liquids with high concentrations of salts that can freeze at much lower temperatures. But the question of whether brines can even form on Mars has yet to be answered.

Vincent Chevrier, an associate research professor at the University of Arkansas’ Center for Space and Planetary Sciences, has been studying that question for 20 years and now thinks he knows the answer: ‘yes they can.’

His case for the existence of liquid brines on Mars was recently published in Nature Communications Earth and Environment.

Chevrier used meteorological data taken from the Viking 2 landing site on Mars combined with computer modeling to determine that brines can develop for a brief period of time during late winter and early spring from melting frost. This challenges the assumption that Mars is entirely devoid of liquid water on the surface and suggests that similar processes may occur in other frost-bearing regions, particularly in the mid-to-high latitudes.

Data from Viking 2, which landed on Mars in 1976, was used because, Chevrier said, “It was the only mission that clearly observed, identified and characterized frost on Mars.” Melting frost presents the best chance to find liquid brines on Mars, but there’s a catch: frost on Mars tends to sublimate quickly, which means it transitions from a solid to a gas without spending time in a liquid state due to Mars’ unique atmospheric conditions.

But by sifting through the Viking 2 data, combined with data from the Mars Climate Database, Chevrier was able to determine that there was a brief window in late winter and early spring when the conditions were right for the formation of brines. Specifically, there is a period of one Martian month (roughly equivalent to two Earth months) where the conditions were ideal at two points during the day: roughly in the early morning and late afternoon.

There is an abundance of salts on Mars, and Chevrier has long speculated that perchlorates would be the most promising salts for brine formation since they have extremely low eutectic temperatures (which is the melting point of a salt–water mixture). Calcium perchlorate brine solidifies at minus 75 degrees Celsius, while Mars has an average surface temperature of minus 50C at the equator, suggesting there could be a zone where calcium perchlorate brine could stay liquid.

Modeling based off known data confirmed that twice a day for a month in late winter and early spring there is a perfect window in which calcium perchlorate brines can form because the temperature hovers right around the sweet spot of minus 75C. At other times of day it is either too hot or too cold.

While Chevrier’s findings are not slam-dunk proof of brines, they make a strong case for their existence in small amounts on a recurring basis. Even if there were direct evidence of a calcium perchlorate brine detected by a past or future lander, it would not be in large amounts. Calcium perchlorate is only about 1% of the Martian regolith, and the frost that does form on Mars is extremely thin – far less than a millimeter thick. So it is unlikely to generate much water, certainly not enough to support human life.

But it doesn’t mean the planet couldn’t have supported life adapted to a much colder, drier planet.

Either way, Chevrier is encouraged to find that brines would form under established conditions and looks forward to further confirmation. He notes in the conclusion of his paper: “The strong correlation between brine formation and seasonal frost cycles highlights specific periods when transient water activity is most likely, which could guide the planning of future astrobiological investigations.

“Robotic landers equipped with in situ hygrometers [for measuring moisture content in air] and chemical sensors could target these seasonal windows to directly detect brine formation and constrain the timescales over which these liquids persist.”

Perchlorate brine formation from frost at the Viking 2 landing site, Nature (open access)

Astrobiology,

The Europa Imaging System (EIS) consists of a Narrow-Angle Camera (NAC) and a Wide-Angle Camera (WAC) that are designed to work together to address high-priority science objectives regarding Europa’s geology, composition, and the nature of its ice shell.

EIS accommodates variable geometry and illumination during rapid, low-altitude flybys with both framing and pushbroom imaging capability using rapid-readout, 8-megapixel (4k × 2k) detectors. Color observations are acquired using pushbroom imaging with up to six broadband filters.

The data processing units (DPUs) perform digital time delay integration (TDI) to enhance signal-to-noise ratios and use readout strategies to measure and correct spacecraft jitter. The NAC has a 2.3° × 1.2° field of view (FOV) with a 10-μrad instantaneous FOV (IFOV), thus achieving 0.5-m pixel scale over a swath that is 2 km wide and several km long from a range of 50 km.

The NAC is mounted on a 2-axis gimbal, ±30° cross- and along-track, that enables independent targeting and near-global (≥90%) mapping of Europa at ≤100-m pixel scale (to date, only ∼15% of Europa has been imaged at ≤900 m/pixel), as well as stereo imaging from as close as 50-km altitude to generate digital terrain models (DTMs) with ≤4-m ground sample distance (GSD) and ≤0.5-m vertical precision.

The NAC will also perform observations at long range to search for potential erupting plumes, achieving 10-km pixel scale at a distance of one million kilometers. The WAC has a 48° × 24° FOV with a 218-μrad IFOV, achieving 11-m pixel scale at the center of a 44-km-wide swath from a range of 50 km, and generating DTMs with 32-m GSD and ≤4-m vertical precision.

The WAC is designed to acquire three-line pushbroom stereo and color swaths along flyby ground-tracks.

The Europa Imaging System (EIS) Investigation, Space Science Reviews via PubMed (open access)

Astrobiology,

Investigating the evolution of Escherichia coli in microgravity offers valuable insights into microbial adaptation to extreme environments.

Here the effects of simulated microgravity (SµG) on gene expression and genome evolution of E. coli REL606, a strain evolved terrestrially for 35 years, is explored. The transcriptomic changes for glucose-limited and glucose-replete conditions over 24 h illustrate that SµG increased the expression of genes involved in stress response, biofilm, and metabolism.

A greater number of differentially expressed genes related to the general stress response (GSR) and biofilm formation is observed in simulated microgravity cultures under glucose-limited conditions in comparison to glucose-replete conditions.

Longer term SµG culture under glucose-limited conditions led to the accumulation of unique mutations when compared to control cultures, particularly in the mraZ/fruR intergenic region and the elyC gene, suggesting changes in peptidoglycan and enterobacterial common antigen (ECA) production.

These findings highlight the physiological and genomic adaptations of E. coli to microgravity, offering a foundation for future research into the long-term effects of space conditions on bacterial evolution.

Simulated microgravity triggers a membrane adaptation to stress in E. coli REL606, BMC Microbiology (open access)

Astrobiology, space biology,

Current climate models have so far been unable to adequately reproduce the clouds over the Southern Ocean around Antarctica. An international team has now taken an important step towards filling this gap: The researchers were able to prove that the majority of ice nuclei in the atmosphere there are due to sugar compounds from marine microorganisms in the seawater.

They enter the clean air above the sea through sea spray and evaporation, causing water droplets to freeze and thus affecting cloud and precipitation formation. Ice formation in clouds has a major influence on the climate as ice particles in clouds reflect sunlight much more strongly than pure water clouds.

These results emphasize the importance of biological sources for precipitation formation in remote marine regions such as around the Antarctic, as researchers from the Leibniz Institute for Tropospheric Research (TROPOS) and the Arctic University of Norway in Tromsø recently published in the journal Environmental Science & Technology.

Ice formation processes influence the radiation properties, precipitation formation and consequently the lifespan of clouds. Ice formation is made possible by so-called ice nucleating particles (INPs). In remote marine regions such as the Southern Ocean, where INP concentrations in the clean atmosphere are low, large differences in radiative effects between models and measurements have been observed. A better understanding of the sources and properties of ice nuclei, such as aerosol particles originating from sea spray, is therefore necessary to improve climate models.

Extensive exchange processes take place between the ocean and the atmosphere. Here at the transition between the open sea and the ice shelf. The images were taken in 2019 during the PI-ICE expedition, in which researchers from TROPOS were also involved. Credit Sebastian Zeppenfeld, TROPOS

It has been known for over a decade that ice-forming macromolecules produced by marine microorganisms such as fungi, protists or yeasts in seawater can enter the atmosphere via sea spray. For terrestrial sources, there is now some knowledge to be able to assign the macromolecules to specific proteins and polysaccharides.

In contrast, there was previously a lack of knowledge about the chemical identity of these ice-forming macromolecules from marine sources. “During the Polarstern expedition PS106 in 2017, we observed increased glucose concentrations in Arctic samples and concluded that this glucose could be an indicator of ice nuclei in seawater. The monosaccharide glucose is a degradation product of polysaccharides. It was therefore obvious to us that polysaccharides could be the missing piece of the puzzle,” explains Dr Sebastian Zeppenfeld from TROPOS.

A cosmos of microorganisms such as bacteria, algae, marine diatoms, haloarchaea, viruses, yeasts and fungi live in the surface film of the oceans that separates seawater from the atmosphere above. In addition to algae and bacteria, which primarily contribute to the production and decomposition of biomass, marine fungi are now also attracting scientific interest.

As their potential role as ice nuclei was still largely unexplored, the researchers took a closer look at marine fungi. “In this study, we investigated the ice nucleation of marine polysaccharides derived from marine fungi and protist, as well as commercially available standard polysaccharides,” reports Dr Susan Hartmann from TROPOS, who examined ice nucleation in the laboratory using the INDA (Ice Nucleation Droplet Array) droplet freezing test.

The result is a collection of data that indicates how many ice nuclei are formed at which temperatures by which components in the cloud droplets. The data now published are the first on protists and fungi from seawater that produce the aforementioned polysaccharides and catalyze ice formation. It was already known that marine biology produces large numbers of ice nuclei in the atmosphere.

The new study has now shown that the polysaccharides explain the total number of biological ice nuclei between around -15 and -20 degrees centigrade. Together with the new data, various other studies provide a differentiated picture of which components in the unpolluted atmosphere of the southern high latitudes are responsible for ice in the cloud droplets: in warm clouds below -2 degrees Celsius these are mainly proteins, in medium-cold clouds below -10 degrees Celsius these are mainly the now proven polysaccharides and only in very cold clouds below -20 degrees Celsius the well-known mineral dust dominates.

However, as extensive sources of mineral dust (e.g., deserts) are scarce in the Southern Hemisphere, the importance of mineral dust for ice formation in the very clean air over the seas around Antarctica is much lower than in the Northern Hemisphere. The mixed-phase clouds with liquid water and ice are mostly located in the temperature range between -15 and -20 degrees Celsius, i.e., precisely in the range in which the polysaccharides are among the most important ice nuclei.

“In our simulations, we were able to show that at -15 to -16 degrees Celsius, the polysaccharides over the gigantic areas of the oceans in the clean Southern Hemisphere are probably the most important ice nuclei, i.e., they contribute more to ice formation than mineral dust emitted from the deserts, which is normally assumed to be the main type of ice nuclei in climate models. This is a new and important finding for climate models,” summarizes Dr Roland Schrödner from TROPOS, who analyzed the data using the TM5 global atmospheric chemistry transport model.

The study builds on years of preliminary work by three groups at TROPOS: The Aerosol Microphysics is investigating ice formation in cloud droplets for a long time, Atmospheric Modelling is researching the influence of various types of particles on the climate and Atmospheric Chemistry is analyzing the chemical composition.

The researchers had previously measured the concentrations of polysaccharides in the atmosphere during various expeditions, including the Spanish Antarctic expedition PI-ICE, the German Arctic expedition PASCAL/PS106, the MarParCloud campaign in the tropical Atlantic and measurements on Spitsbergen in the Arctic. These new findings were only made possible by combining this work.

From the researchers’ point of view, this study emphasizes the importance of natural biological components in the atmosphere and that the biosphere and atmosphere are closely linked in the Earth system.

If the ambitious climate protection goals of many countries are realized in the coming decades, man-made emissions are expected to decrease and natural aerosol particles will become even more important for cloud microphysics. Clouds in a clean environment, i.e., with a low number of droplets, react more sensitively to fluctuations in aerosol number concentration.

The clean Southern Hemisphere around Antarctica is therefore particularly exciting for cloud research: The “HALO-South” mission of the German research aircraft HALO will investigate the interaction of clouds, aerosols and radiation over the Southern Ocean around New Zealand in more detail from July to October 2025 under TROPOS leadership. The measurements in the air will be supplemented by measurements on the ground.

During the “goSouth-2” measurement campaign, researchers from TROPOS and Leipzig University will work with other partners to investigate the clouds of the Southern Ocean. To this end, the mobile aerosol and cloud remote sensing system LACROS will be deployed near Invercargill at the southern tip of New Zealand from September 2025 to March 2027. The clouds of the less anthropogenically influenced Southern Hemisphere still harbour many secrets that the researchers from Leipzig hope to uncover over the next few years.

Tilo Arnhold

Polysaccharides – Important Constituents of Ice Nucleating Particles of Marine Origin, EGU

Astrobiology,

A rocky planet zips around the faint orange star WASP-132 once every 24 hours and 17 minutes. Far beyond it, a frigid gas giant drifts along a path that takes five Earth years to complete.

Lead author Nolan Grieves of the University of Geneva and colleagues uncovered the pair while re‑examining nine years of telescope data.

Their find shows that hot Jupiter systems can shelter nearby small planets rather than always clearing them out.

Sprinting around WASP-132

The inner world, named super‑Earth WASP‑132 c, skims only about 1.7 million miles from its star, closer than many low‑Earth satellites circle ours.

Despite the proximity, its measured bulk density of 5.5 g/cm³ hints at a largely rocky composition, slightly heavier than Earth itself.

TESS space‑telescope photometry reveals that each transit lasts just over one hour. Follow‑up spectra show a planetary mass roughly six times that of Earth, confirming its compact size.

“This is the first time we have observed such a configuration,” said Dr. David Armstrong, University of Warwick, referring to a super‑Earth tucked inside a hot‑Jupiter system.

Armstrong’s team supplied high‑cadence data with the HARPS spectrograph, boosting the radial velocity precision enough to isolate the tiny wobble of the 24‑hour world.

An icy giant in the dark

WASP‑132 d, the newly announced outer planet, orbits nearly 252 million miles out, about the distance from the Sun to the asteroid belt.

It tips the scale at 5.2 times Jupiter’s mass and likely sports deep layers of methane‑rich clouds that never see direct starlight.

At such a distance the planet receives less than 1 percent of the light falling on Earth. Temperatures could hover hundreds of degrees below freezing, giving researchers a rare look at a young ice giant still cooling.

Because the orbit spans half a decade, astronomers relied on more than nine years of CORALIE spectrograph data to trace its slow pull.

The long baseline also revealed a steady velocity trend that hints at yet another, unseen companion further out.

Finding WASP-132

Space‑based photometry from TESS and CHEOPS provided crisp light curves, flagging potential planets.

Ground‑based spectra from HARPS and CORALIE then measured stellar wobble to pin down masses, a one‑two punch that has become routine for multiplanet hunts.

A multidimensional Gaussian‑process model filtered out chromospheric activity signals from starspots rotating every 31 days. Without that step the planet signatures would have drowned in stellar noise.

For the inner planet, the team measured a radial‑velocity amplitude of just 4.6 ft/s, about walking speed, showcasing the reach of modern spectrographs.

The outer giant’s tug, in contrast, registers at over 200 ft/s, easy to spot once enough years of data accumulate.

Together the datasets produce a complete family portrait: a small rocky planet at 0.018 AU, a seven‑day hot Jupiter originally found in 2017, and the distant icy behemoth at 2.71 AU. Such architectural detail lets theorists test how planets migrate after formation.

Lessons for planetary architects

Hot Jupiters usually travel inward through high‑eccentricity interactions that scatter smaller worlds. Finding a close‑in rocky planet surviving next to one challenges that picture.

The team argues that WASP‑132 b may have drifted quietly through the disk, leaving the inner super‑Earth untouched and preserving a dynamically “cool” history. Its near‑circular orbit and moderate equatorial gravity support that calm evolution.

François Bouchy of UNIGE called the system “a remarkable laboratory for studying the formation and evolution of multi‑planetary systems.”

He noted that mixing planet sizes and separations in one place lets models test where solid cores assemble and where gas envelopes inflate.

Interior modeling suggests the ice giant holds at least 17 Earth masses of heavy elements, while the inner planet is nearly bare of volatiles.

These contrasting chemistries likely reflect where each body accreted before migration reshuffled the deck.

Organic chemistry orbiting WASP-132

The discovery connects with current research in astrochemistry, which investigates how complex organic molecules develop on interstellar ice grains.

These molecules are considered important because they match those found in comets and asteroids.

When objects like these collide with planets, they can deliver both water and organic compounds. A distant ice giant such as WASP‑132 d helps maintain the low temperatures needed for these molecules to survive in space.

By sampling the planet’s atmosphere once it transits, as James Webb could do if orbital alignments cooperate, scientists hope to detect the chemical fingerprints of that frozen chemistry.

Spectral clues to methane, ethane, or even more complex organics would connect planetary science with prebiotic chemistry.

Meanwhile, the rocky inner planet lies far too close for life as we know it; its dayside bakes at an estimated 1 750°F. Yet its bulk density offers a laboratory for studying how silicate mantles and iron cores behave under extreme stellar radiation.

Where astronomers look next

Future Gaia data releases may detect the astrometric wobble of the ice giant, pinning its true mass and orbital tilt. Additional spectra could also reveal whether the outer trend is a brown dwarf or another planet.

The team has already secured ESPRESSO time to measure spin‑orbit alignment during transits. If both planets share the star’s equatorial plane, the quiet‑migration scenario gains weight.

Surveys are now re‑checking hot‑Jupiter hosts for hidden, fast‑orbiting companions like WASP‑132 c. As technology drives radial‑velocity precision below three feet per second, many more “day‑long year” planets may come to light.

Finding them will refine models of planetary system diversity and, by extension, the odds of habitable worlds. Each well‑characterized system moves the field from speculation toward statistical certainty.

The study is published in Astronomy & Astrophysics.

Image credit: Thibaut Roger, Université de Genève.

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