High-pressure clinopyroxene in Northwest Africa 12774 and new geobarometric evidence for a planetary embryo-sized angrite parent body

The NASA Viking Program laid the framework for Mars science, technology, and exploration. While the barren view of the Red Planet revealed by Viking was antithetical to the expectations of the planetary science community at the time, Viking was remarkable because it achieved numerous novel technical feats that continue to shape planetary robotic exploration today, integrating technical elements from disparate scientific fields, culminating in the scientific, engineering, and management achievements of over 2000 people. Over the last five decades, the results of the Viking science payload have led to vigorous debate within the astrobiology community on the burden of proof necessary to determine the detection of life, a necessary discussion that continues today. The future of missions designed to search for extant life will build upon the foundation laid by Viking, with a scientifically integrated, matured search-for-life strategy, one invigorated by technologists, engineers, and science communicators. As we celebrate the 50th anniversary of this groundbreaking mission, it is imperative that the scientific community reflects the Viking program's foundational impact on planetary science and exploration. Looking to the future, we must consider the perspectives and lessons learned from Viking while working towards a long-term vision for continued astrobiological exploration of Mars and other planetary bodies.

Liquid water exists on the Earth and several other planetary bodies in our solar system. The chemical character of these aqueous reservoirs is central to evaluating their habitability. Here, we synthesize the chemical features of water reservoirs and their biological implications on the modern Earth. We then outline constraints on the evolutionary history of Earth's ocean chemistry and discuss its interplay with the biosphere. Furthermore, we examine the inferred chemical environments of water bodies on early Mars, dwarf planet Ceres, Jupiter's moon Europa and Saturn's moons Enceladus and Titan. We conclude by outlining priority questions for future planetary habitability studies.

The ambiguity of the Viking lander life-detection experiments left microbiology and microbial ecology out of space missions for 50 years. However, this was largely because the scientific process inherent in the search for life was misunderstood by a space exploration community that wanted clear-cut answers. Since Viking, enormous advances have been made in our knowledge of microorganisms, their biochemistry, and physical and chemical limits. Coupled with improvements in methods for culturing microorganisms and measuring their active metabolism, this has made possible more sophisticated experiments to search for life in extreme environments on Earth and on other planetary bodies. By overcoming misunderstandings surrounding the Viking lander experiments, microbiology and microbial ecology can take center stage in renewed efforts to seek life elsewhere. Furthermore, new knowledge in these fields should be used to overhaul assumptions in planetary protection, and it can be used to achieve permanent human space settlement.

This review of martian organic geochemistry aims to contextualize recent findings of organic molecules in martian meteorites and from Mars missions within the broader study of origins of life on Earth. Analyzing martian organic inventories helps us understand the abiotic processes in planetary environments that are common wherever rocks interact with liquid brines and that likely contributed to the emergence of life on Earth. Mars is only the second planetary body studied for organic molecules; while carbonaceous meteorites, comet missions, and sample-return analyses of comets and asteroids have shown the diversity of organics across the solar system, studying Mars reveals what these molecules are on another planet. Although a definitive sign of extraterrestrial life has not yet been found, the findings provide insights into abiotic synthesis mechanisms that would have occurred on early Earth. At worst, these observations represent the oldest planetary record of organic and prebiotic chemical synthesis pathways that could have led to life, as inferred from the alteration of Earth's oldest rocks. They may also point to potential habitats for past martian life. Currently, samples collected by the Perseverance rover represent a unique opportunity to verify which of the two questions, "Are we alone?" or "How did we get here?" will be true for Mars. Without doubt, these questions would be best addressed through the use of higher resolution analyses by more advanced and sensitive instrumentation after sample return to Earth. Even if no definitive signs of life are found in returned samples, they would give us the opportunity to study the missing link to life on Earth, that of the primordial abiotic organic chemical processes that could have led to life. Therefore, there are no wrong answers to exploring Mars for signs of life; its secrets will illuminate our understanding of ourselves and our place in the universe, whatever the answer.

ABSTRACT Within the Earth and other terrestrial planetary bodies, magnetospheres are generated by convective dynamo action within their liquid metallic outer cores. By experimentally determining the solid–liquid phase transitions of core-relevant alloys, the likely compositions of these cores may be constrained. Experiments were conducted on Fe-Si alloys in the range of Fe-5 to Fe-33 wt% Si using a 1000-ton cubic anvil press, for pressures up to 5 GPa and temperatures into the liquid state. The liquidus was mapped across this composition range for each of 3, 4, and 5 GPa. It was determined that the high-pressure melting boundaries are roughly 100–200 K higher than at 1 atm, with an increase of ∼100 K from 3–5 GPa. A range of 10–18 wt% Si is suggested for the Moon, which would not support chemical convection in the lunar core and may explain why its magnetic field shut down so early in its evolution.

Recent astronomical observations show that carbon dioxide (CO2) is widespread on planetary bodies, often coexisting with water (H2O). Crystalline carbonic acid (H2CO3), produced from CO2-H2O interactions, has been predicted and synthesized under high pressure, yet their dynamic behaviors under planetary interior conditions remain poorly understood. Here, we investigate the stability of CO2-H2O planetary ices across pressures from 0 to 500 gigapascals. Our simulations demonstrate that H2CO3 and orthocarbonic acid (H4CO4) become dominant C─O─H compounds and evolve from molecular crystals into three-dimensional solids with increasing pressures. Particularly, both carbonic acids transform into a H-diffusive superionic phase and subsequently a C─H doubly superionic conduit enabled by interconnected oxygen polyhedral voids, where correlated motions between ions enhance the ionic conductivities. Moreover, the hydrogen in H2CO3 exhibits strong anisotropic behaviors that may contribute to the nonaxisymmetric magnetic fields of ice giants. These findings further suggest that carbonic acid ices could sustain hydrogen-carbon transport, potentially enhancing convective volatile cycling in giant planet interiors.

Extreme environments on Earth are often studied as analog environments on other planetary bodies, since other planetary bodies in our solar system have extreme conditions for life as we know it. Extremophiles are commonly studied in astrobiology given that these microorganisms can survive in extreme conditions (e.g., pressure, temperature, pH). Omics aims to characterize and quantify biological molecules that regulate the structure, function, and dynamics of organisms; hence these methods can improve our understanding of their adaption strategies. The properties of the membranes of extremophiles, for example, which are amphiphilic molecules like lipids and fatty acids, play a key role in their adaptation to extreme conditions. Lipidomics of contemporary extremophiles offer a way to study the composition of their lipids exposed to a variety of stress conditions. Lipids are geostable biomolecules that can retain information about their biological origin for more than a billion years. Therefore, the ability of these molecular fossils to become preserved in extreme environments and assist in the reconstruction of early life on Earth indicate that they are likely to survive if preserved in extreme environments elsewhere. This review article highlights the importance of lipidomics in astrobiology and connects contemporary extremophilic lipids with the lipid fossils to outline approaches to detect extraterrestrial microbial life.

Abstract Superrotation is a common feature of quickly rotating gas giants (e.g., Jupiter), slowly rotating planetary bodies (e.g., Titan), and tidally locked planets. In this paper we compare and contrast the mechanisms of superrotation in slow rotators and tidally locked planets. We cover a wide range of planetary properties, in particular varying the thermal Rossby number Ro T (controlled by planetary size, rotation rate, and instellation) and a radiative relaxation timescale T rad (which parameterizes atmospheric optical thickness). We use a two-level primitive equation model that contains the principal mechanisms for superrotation in both regimes yet remains analytically tractable. Linearizations of the model elucidate the behavior of superrotation-inducing eddies. In tidally locked planets a baroclinic Matsuno–Gill-like structure arises in response to the zonal heating asymmetry but only produces superrotation when low-level drag is present. Nonlinear integrations further explore the superrotating regimes and exhibit significant time variability even in statistical equilibrium. Not all tidally locked regimes superrotate: subrotation arises at high T rad (optically thick atmospheres) and weak low-level drag. On axisymmetrically forced slow rotators, superrotation is ubiquitously linked to a previously identified Rossby–Kelvin instability. The instability itself is also linked to the spin-up of superrotation in some tidally locked regimes. Finally, we explore the continuous transition in the mechanisms of superrotation from axisymmetrically forced to tidally locked planets by applying a progressively stronger zonally asymmetric equatorial forcing. The Matsuno–Gill pattern quickly dominates over traveling planetary Rossby–Kelvin waves in forcing superrotation, although both mechanisms can coexist. These results provide a unified view of superrotation mechanisms across a wide range of planetary bodies.

Determining the internal structure of planetary bodies from gravitational observations is a key challenge in planetary geophysics. Traditional gravity inversion methods suffer from non-uniqueness due to trade-offs between mass distribution and depth, limiting their ability to resolve internal layering. We present SynthGen , a forward-modelling code developed to simulate the gravitational response of planetary bodies using parametric, multi-layer interior models without any a priori assumption, like the hydrostatic equilibrium. SynthGen calculates gravitational potential, Free-Air, and Bouguer anomalies through spherical harmonic expansions, leveraging the SHTools library (Wieczorek and Meschede, 2018). It accommodates a wide variety of internal configurations, including homogeneous layers with user-defined densities, thicknesses, and topographic geometries of internal interfaces, such as spherical, ellipsoidal, random, or Bouguer anomaly-derived interfaces. The code can be used both predictively and diagnostically: about the latter, SynthGen performs parameter-space exploration constrained by total mass, moment of inertia, and shape, identifying best-fit interior models by minimising the misfit between observed and synthetic gravity fields using combined statistical metrics. We apply SynthGen to Mercury, using the HgM009 gravity model derived from MESSENGER data (Genova et al., 2023), and recover crustal thickness and core parameters consistent with recent independent geophysical estimates. In predictive mode, SynthGen generates synthetic gravity fields for planetary bodies where gravity data are not available or are still limited in resolution, such as Ganymede. These simulations can support the planning and optimisation of space missions. By integrating physical constraints, statistical validation, and flexibility in model design, SynthGen offers a robust platform for planetary interior studies, constraining interior structures from gravity measurements across a broad range of Solar System bodies. • SynthGen simulates gravity fields of planetary bodies using parametric interior models and spherical harmonics. • SynthGen retrieves best-fit internal structures by comparing simulated and real gravity data with statistical metrics. • SynthGen can predict gravitational signals for future missions like JUICE and supports diverse planetary scenarios.

Accurate onboard navigation is fundamental to spacecraft autonomy, especially in deep-space and cislunar environments where ground-based orbit estimation may introduce unacceptable latency. Optical navigation (OpNav) offers a viable solution, but conventional geometric methods typically require high-resolution imagery and substantial computational resources, limiting their applicability under challenging visual conditions and onboard hardware constraints. This paper presents a reinforcement learning (RL) framework for autonomous optical navigation in cislunar space. A convolutional neural network is trained to correct the position estimates by processing differences between simulated and observed lunar images. Training is performed in a simulated visual environment, enabling the policy to learn robust estimation strategies under observation noise, unmodeled dynamics, and varied initial conditions. The method is demonstrated for station-keeping along a southern halo orbit around the Earth–moon L2 point. Results show that the RL-based navigation policy consistently provides position estimates within the required accuracy for the closed-loop onboard controller to successfully maintain the spacecraft along the reference orbit, despite low-quality image inputs and a low update frequency. These findings underline the feasibility of RL-driven OpNav as a computationally efficient and resilient alternative to traditional techniques, offering a promising foundation for future onboard learning-based navigation systems in the vicinity of planetary bodies.

Understanding how granular materials behave in low gravity is crucial for planetary science and space exploration. It can also help us understand granular phenomena usually hidden by gravity. On Earth, gravity dominates granular behavior, but disentangling its role from intrinsic particle interactions is challenging. We present a series of compression and shear experiments conducted in microgravity using the Center of Applied Space Technology and Microgravity drop tower and GraviTower Bremen. Our in-house developed experimental setup enables precise measurement of packing density and in situ shear stress via a Taylor–Couette rheometer. We find that the jamming transition occurs at a lower packing density in microgravity than on Earth, confirming that gravity promotes densification. Rheological measurements further reveal that in microgravity, the lack of a secondary force field and the predominance of cohesive interparticle forces increase the stress needed for granular media to flow. These findings highlight gravity’s dual role in enhancing both compaction and flow and demonstrate the need for tailored granular models, valid in low- and microgravity environments.

Titan, Saturn’s largest moon, presents a uniquely compelling environment for in situ resource utilization (ISRU) in the outer Solar System. This paper examines Titan’s atmospheric, surface, and compositional characteristics in the context of resource extraction, propellant production, and energy generation. Titan possesses a dense, nitrogen-rich atmosphere, stable surface reservoirs of liquid methane and ethane, and extensive deposits of water ice, enabling the acquisition of both fuel and oxidizer from local materials. Methane can be obtained directly with minimal processing, while oxygen may be produced through electrolysis of water ice, forming an efficient methane-oxygen propellant system that benefits from Titan’s low temperatures and elevated surface pressure. The hydrogen co-produced in this process may also serve as a rocket fuel. In addition to propellant production, multiple indigenous energy sources, including chemical, wind, hydropower and solar, are evaluated as enablers of sustained ISRU operations. Collectively, these features distinguish Titan from other planetary bodies and establish it as a technically credible and strategically significant target for ISRU-enabled exploration missions.

Planetary and geological melts and magmas produced at depth encounter rocks at a variety of temperatures and redox conditions during their ascension towards the surface of planetary bodies. Reactions occur between the magma and surrounding rock material, but despite their potential importance for the regulation of magmatic differentiation, the rates of such interactions are rarely considered and poorly known. The aim of this work is to review the results of high-temperature experiments and kinetic models for the dissolution of the main rock-forming minerals in aluminosilicate melts, that may be applied to partial melting of common rock types, and reactions between the melts and the principal rocks composing the lithosphere. A kinetic equation allowing the first-order prediction of mineral dissolution rates in planetary and geological melts was generated. The diffusion-controlled dissolution rate r (mol cm-2 s-1) of common rock-forming silicate minerals in aluminosilicate melts at 1300 ± 20 °C and <1 GPa pressure can be described by an inverse function of the viscosity of boundary layer melt (i.e. that formed at the crystal-melt interface upon the dissolution) independent of silicate mineral composition according to: r = k η-n, where the correlation coefficient k = 2 ×10-7 (mol cm-2 sn-1 Pan), n = 0.5, and η (Pa s) is the viscosity of the boundary layer melt (for η ≤105 Pa s). This function relating dissolution rate and melt viscosity is consistent with a simple detachment mechanism involving network-forming Si-O atoms during silicate mineral dissolution. This equation can be applied to the dissolution of the principal rock-forming minerals during melt-rock interactions in the lithosphere such as lithosphere assimilation. It shows that low-viscosity mafic-ultramafic magmas can be significantly more contaminated by lithosphere rock material compared to the high viscosity felsic magmas. This correlation for the main rock-forming minerals may be directly applicable to planetary lithosphere assimilation by magmas, magma mixing as well as the modeling of mantle metasomatism or other types of melt-rock interactions. Future efforts should be concentrated on developing kinetic models and providing further experimental constraints on the kinetic factors that control mineral-melt reactions in the terrestrial and planetary mantles.

Geoelectrochemical reduction of CO2 is proposed as a potentially significant abiotic synthesis pathway catalyzed by sulfide minerals under planetary conditions, but whether this reaction could be catalyzed by geologically abundant carbonate and phyllosilicate minerals is unknown. Here we show that adsorption of trace transition metal cations, such as Cu(II) and Zn(II), endows common Ca/Mg-carbonates and phyllosilicates with high catalytic performance for CO2 reduction to form methane, formic acid, carbon monoxide, and C2 organics. We also observe viable synthesis of C-N bonded compounds (mainly acetamide) when ammonia is present. During these reactions, the adsorbed metal cations are partially reduced into metallic states and become catalytic, while mineral substrates facilitate the water dissociation to supply protons for CO2 hydrogenation. This facile electrochemical reduction of CO2 catalyzed by carbonates and phyllosilicates could facilitate the origin of life on the primitive Earth and help explain the detection of organics on other habitable planetary bodies.

Context. Free-floating planetary mass objects – worlds that roam interstellar space untethered to a parent star – challenge conventional notions of planetary formation and migration, but also of star and brown dwarf formation. Aims. We focus on the multiplicity among free-floating planets. By virtue of their low binding energy (compared to other objects that formed in these environments), these low-mass substellar binaries represent the most sensitive probe of the mechanisms at play during the star formation process. Methods. We use the Hubble Space Telescope and its Wide Field Camera 3 and the Very Large Telescope and its ERIS adaptive optics facility to search for visual companions among a sample of 77 objects, members of the Upper Scorpius and Taurus young nearby associations, with estimated masses in the range between approximately 6–66 M Jup . Results. We report the discovery of one companion candidate around a Taurus member with a separation of 111.9±0.4 mas or ∼18 au assuming a distance of 160 pc, with an estimated primary mass in the range between 3–6 M Jup and a secondary mass between 2.6– 5.2 M Jup , depending on the assumed age. This corresponds to an overall binary fraction of 1.8 −1.3 +2.6 % among low-mass brown dwarfs and free-floating planetary mass objects over the separation range ≥7 au. Despite the limitations of small-number statistics and variations in spatial resolution and sensitivity, our results, combined with previous high-spatial-resolution surveys, suggest a notable difference in the multiplicity properties of objects below ∼30–50 M Jup between Upper Sco and Taurus. In Taurus, a binary fraction of 5.6 −2.3 +3.2 % is found for objects with masses below 30M Jup , and of 7.8 −2.4 +3.0 % for objects with masses below 50M Jup , while no binary was found among 80 objects over the matching luminosity range in Upper Sco, corresponding to an upper limit of ≤1.2%. Conclusions. This difference may point to intrinsically distinct formation conditions, with warmer parental molecular clouds originally present in Upper Sco potentially inhibiting fragmentation into the lowest-mass brown dwarfs and free-floating planets compared to cooler environments such as Taurus.

Long-chain nitrogen ions and radicals ([Nn]x+/[Nn]x-, n > 3) are naturally occurring under the intense radiative conditions of the Earth's ionosphere and those of other planetary bodies. However, the strong thermodynamic driving force to lose N2 renders these types of molecule extremely reactive under ambient conditions such that they can typically be studied only under extreme conditions, for example, at ultrahigh pressures (10 GPa to >200 GPa). Here we report the isolation of a series of five molecules featuring metal unsupported {N4}•- units under ambient conditions, with one derivative demonstrating remarkable multi-week long persistence in the solid state. Spectroscopic, crystallographic and computational studies provide insight into the bonding across the {N4}•- chain. Reactivity studies reveal that the chain can cleave into N1 and N3 fragments, and can act as a source of nitrene radical anions, an observation that such molecules could act as storable nitrogen group transfer reagents.

The "two-layer model" is a degrees-of-freedom non-autonomous dynamical system consisting of a massive, ellipsoidal (possibly spheric) body made of two layers - a hard core and a viscous fluid - revolving about a major planet or a star. We assume that the rotation and the two revolution periods (of core and shell) are close to a resonance, and aim to investigate, in a rigorous way, the mathematical conditions which maintain the resonant motion. In a previous article (Pinzari et al. in Celest Mech Dyn Astron 136(5):39, 2024), we discussed the phenomenon known as "capture into resonance", via qualitative arguments supported by numerical findings. In this paper, we reframe the model along the lines of a suitable version of (which we refer to as "non-quasi-periodic") normal form theory and provide an explicit amount of the resonance trapping time, which is estimated as exponentially-long, in terms of the small parameters of the system.

Lunar mare basalts are often rich in titanium, hosted predominantly within the mineral ilmenite (Fe2+Ti4+O3). Here, we examine ilmenite in a ~ 3.8 billion-year-old mare basalt (Apollo rock 75035) using high-resolution electron microscopy and electron energy loss spectroscopy. A key finding is that 75035 ilmenite is itself enriched in Ti, beyond the end member of the conventional solid solution series. Using energy loss near-edge spectroscopy, we determine that the excess Ti is trivalent, with Ti3+ accounting for 13% of the total Ti content. This discovery confirms the presence of trivalent Ti in lunar ilmenite, long hypothesized based on the Moon’s reducing environment. Accounting for the change in implied stoichiometry, a review of literature data suggests that Ti3+ may be present in ilmenite across a wide range of lunar samples. We extrapolate known relationships from the literature to connect Ti3+ to redox conditions, estimating the oxygen fugacity during crystallization of 75035 to be below the iron-wüstite buffer, ΔIW≤ − 1.6. Further quantifying the relationship between Ti valence state and oxygen fugacity would allow Ti3+-bearing ilmenite to serve as an oxybarometer able to access the reducing conditions found on many planetary bodies.

We aim to understand how landslides affect the shape and rotational motion of small rubble planetary bodies. We limit ourselves to axisymmetric global landslides and take the primordial shape of the body to be axisymmetric as well. The landslides are modelled as shallow granular surface flows using depth averaging, while incorporating the effects of the body’s rotation, topographical changes from previous landslides, its non-uniform gravity field and possible surface mass shedding. The body’s rotational dynamics is coupled to its shape change due to the transport of regolith – surface grains – and also accounts for the influence of radiation torque. We utilise our framework to investigate regolith motion on idealised rubble bodies and actual asteroids. We then study the evolution of the shape and spin state of an initially spherical rubble asteroid undergoing multiple global landsliding events over millions of years – a time scale comparable to typical asteroidal lifetimes. We find that shape changes due to landsliding resist spin-up due to radiation torque and, in some instances, may even cause the body to spin down. Furthermore, rotational fission is delayed, and may even be suppressed, by regolith redistribution toward the body’s equator. Finally, top-shaped configurations may emerge rapidly, which may explain the prevalence of top-shaped asteroids in near-Earth orbits.