Moons orbiting wandering exoplanets could be habitable—with one catch - Astronomy & Space - Astrobiology - Planetary Sciences - UNIVERSE

Credit: David Dahlbüdding

Provided they host thick, hydrogen-dominated atmospheres, moons orbiting free-floating exoplanets could retain much of the heat generated deep within their interiors by tidal forces. Led by David Dahlbüdding at the Max Planck Institute for Extraterrestrial Physics and Giulia Roccetti at the European Space Agency, a new study predicts that hydrogen could act as a potent greenhouse gas—potentially providing habitable conditions for billions of years after their host planets are first ejected from their stellar systems. The work has been published in Monthly Notices of the Royal Astronomical Society.

Heat-absorbing hydrogen

Astronomers have now discovered hundreds of exoplanets drifting through interstellar space, most of them likely flung from their parent systems by violent gravitational encounters in the distant past. After ejection, these rogue worlds would likely have become extremely cold and dark—according to some astronomers, their moons may have faced more interesting fates.

During the chaos of ejection, a moon's orbit can become highly elongated, causing it to be repeatedly stretched and squeezed by its host planet's gravity. Much like Europa and Enceladus in our own solar system, these tidal forces could generate vast amounts of internal heat.

If such a moon's atmosphere were unstable enough for gases to condense into liquid form, most of this tidal heat would simply radiate into space. But the situation could be very different for high-pressure atmospheres dominated by hydrogen.

In Earth's present-day atmosphere, hydrogen molecules (simple pairs of bonded hydrogen atoms) have little warming effect—but under high pressures, they can absorb heat through a process known as "collision-induced absorption" (CIA). During fleeting collisions, hydrogen molecules form supramolecular complexes: temporary assemblies held together by weak, non-covalent bonds.

These complexes are far better at absorbing infrared radiation than the bonds within isolated hydrogen molecules and can rival the absorption of potent greenhouse gases like carbon dioxide and methane.

As a result, some previous studies have considered how much of the energy generated inside a moon, or even newly formed planets, could be trapped efficiently in a thick hydrogen atmosphere. If this were possible, these atmospheres could heat up without the large-scale condensation that plagued earlier carbon dioxide–dominated models.

"Such an exomoon could have surface temperatures sufficient to keep water liquid without a nearby star, significantly expanding the possibilities for life to emerge in the universe," Dahlbüdding explains. "But although such moons could even be detected in the near future, the confirmation and analysis of any atmosphere may well be impossible for a long time."

Combining calculations

For now, the best way to explore these exotic environments is through modeling. As Dahlbüdding explains, these simulations allow researchers to track how a moon's atmosphere and orbit evolve over billions of years following its planet's ejection.

"We combined accurate calculations of atmospheric temperatures with feedback on the chemical composition, mainly through condensation," he says. "This results in the most realistic—albeit still approximate—simulations of such moons to date."

On top of this, the researchers incorporated the latest theoretical insights into how exomoon orbits change over time. "In 2023, a study led by Giulia Roccetti modeled how orbital circularization leads to a decrease in the available tidal heat over time," Dahlbüdding continues. "Together with these previous results, we can calculate the maximum time spent in the habitable zone."

Retaining liquid water

The team's calculations reveal that in the thickest hydrogen-dominated atmospheres considered (reaching 100 times Earth's surface pressure), the effect of collision-induced absorption would make conditions both warm and stable enough to sustain liquid water. In some cases, these habitable conditions could persist for up to 4.3 billion years after the host planet's ejection—comparable to the current age of Earth.

"The hydrogen not only acts as a potent greenhouse gas but also as a stable background where more or less condensing species like methane, ammonia and water vapor can further contribute to retaining the internal heat," Dahlbüdding says.

Parallels with early Earth

Beyond modeling distant exomoons, the researchers suggest their findings may also shed light on Earth's own past. Before life emerged, our planet's atmosphere may have been far richer in hydrogen than it is today, and periodically pressurized by frequent asteroid impacts—conditions that could have enhanced collision-induced absorption.

Such environments may have favored the formation and replication of RNA molecules, ultimately helping to kickstart the process of evolution.

"Through ongoing discussions, we are connecting our research to the latest advances in the search for the emergence of life on Earth," Dahlbüdding says. "And with our paper, we hope to build this bridge between bio- and astrophysics for other scientists as well." 

by Sam Jarman, Phys.org

edited by Sadie Harley, reviewed by Robert Egan 

Source: Moons orbiting wandering exoplanets could be habitable—with one catch 

Creating green materials with light could transform clean energy - Energy & Green Tech - Hi Tech & Innovation

Light-driven synthesis of hourglass-shaped metal–organic frameworks. Credit: Dongling Ma, INRS

Metal-organic frameworks, better known as MOFs, are among the most intensely studied materials for addressing major environmental challenges. Their highly ordered, ultra-porous architecture enables applications ranging from CO₂ capture and air or water purification to catalysis and hydrogen production. It is therefore no surprise that MOFs have drawn global attention in recent years, notably with their recognition by the 2025 Nobel Prize in Chemistry, as they play an increasingly central role in the development of sustainable technologies.

Despite their promise, MOFs remain challenging to synthesize with high precision. Conventional solvothermal methods typically require high temperatures (up to 200° C) and long reaction times, making them energy-intensive and difficult to control. These harsh conditions can compromise structural precision and limit functional performance.

This constraint has now been overcome by Professor Dongling Ma, a nanomaterials expert at the Institut national de la recherche scientifique (INRS) and Canada Research Chair in Advanced Functional Nanocomposites. In collaboration with researchers from McGill University, her team has developed a photochemical synthesis strategy that enables MOFs to be formed under mild, ambient conditions.

"Our work demonstrates that photons can be used not only to initiate MOF synthesis, but also to guide it with exceptional precision. This strategy opens a sustainable pathway for engineering advanced materials while dramatically reducing energy consumption," says Prof. Ma.

In a study published in Nature Communications, the team at INRS Énergie Matériaux Télécommunications Research Centre reports the ambient-temperature synthesis (15° C, four hours) of a cobalt–porphyrin-based MOF—named phoPPF-3—using light as the sole driving force.

Rather than relying on thermal energy, this light-driven approach uses photons to initiate and control the assembly process at the atomic scale. The strategy enables multidimensional control over framework formation, resulting in unique two-dimensional hourglass-like morphologies. Crucially, it also induces selective Co²⁺–carboxylate coordination, preserving free-base porphyrin cores that cannot be maintained using conventional solvothermal synthesis. The outcome is a MOF with enhanced structural precision, improved thermal stability, and a level of control previously inaccessible under traditional conditions.

Enhanced photocatalytic performance for future energy technologies

Beyond its innovative synthesis, phoPPF-3 exhibits superior functional performance. Compared with solvothermally synthesized analogs, it demonstrates higher photocatalytic activity in both benzyl alcohol oxidation and photocatalytic hydrogen evolution. In some cases, performance improvements reach up to 50%, highlighting the strong link between synthesis precision and functional efficiency.

"MOFs already play a strategic role in the energy transition. By enabling atomically precise synthesis under ambient conditions, this approach accelerates the development of more efficient and scalable technologies," notes Yong Wang, a Ph.D. student in the Materials and Energy program in Dongling Ma's laboratory at the time the study was conducted.

Importantly, the researchers also demonstrated that this photochemical methodology is not limited to a single system. Its successful extension to other MOFs underscores the generality and versatility of the approach.

By drastically lowering the energy requirements for MOF synthesis while enhancing structural and functional control, this strategy opens new possibilities for large-scale production and applications such as CO₂ capture, environmental remediation, industrial catalysis, and solar energy conversion and storage. 

Provided by INRS  

by INRS

edited by Stephanie Baum, reviewed by Robert Egan 

Source: Creating green materials with light could transform clean energy