Saturnian System Research Articles

Metastable Dihydrate of Sodium Chloride at Ambient Pressure.

Sodium chloride (NaCl) plays an important role in geochemistry, biology, industry, and food production, and it is among the most common salts in the solar system. Here, we report the discovery of a metastable NaCl dihydrate formed through rapid freezing (101-102 K s-1) of a NaCl solution at ambient pressure. Using synchrotron X-ray and neutron powder diffraction, we show that it transforms irreversibly to hydrohalite and ice Ih above 190 K upon heating and propose it is structurally related to hydrohalite with a 3 × 1 × 3 supercell as its unit cell. Calorimetric analyses reveal that the new hydrate transforms to hydrohalite with a heat release of -3.47 ± 0.55 kJ mol-1. The identification of this new NaCl dihydrate on the surfaces of icy worlds such as the moons of Jupiter and Saturn could indicate regions of recent activity where subsurface brines have frozen rapidly, priority targets for upcoming planetary missions.

Detailed Calculations of the Efficiency of Planetesimal Accretion in the Core-accretion Model. III. The Contribution of Planetesimals beyond Saturn

Continuing our initiative on advancing the calculations of planetesimal accretion in the core-accretion model, we present here the results of our recent study of the contributions of planetesimals around and beyond the orbit of Saturn. In our first two papers, where our focus was on the effects of the Sun and Saturn, the initial distribution of planetesimals was limited to the regions around the accretion zone of a growing Jupiter. In this paper, we expanded that distribution to regions beyond the accretion zone of Saturn. We integrated the orbits of a large ensemble of planetesimals and studied the rate of their capture by the growing proto-Jupiter. In order to be consistent with our previous studies, we did not consider the effect of the nebular gas. Results demonstrated that the exterior planetesimals, especially those beyond 8 au, have only slight contributions to the growth and metallicity of the growing Jupiter. The final mass and composition of this planet is mainly due to the planetesimals inside and around its accretion zone. Our study shows that although the rate of capture varies slightly by the size and composition of planetesimals, in general, the final results are independent of the size and material of these bodies. Results also pointed to a new finding: the rate of accretion follows the same trend as that of the evolution of Jupiter’s envelope, with the largest accretion occurring during the envelope’s collapse. We present details of our analysis and discuss the implications of its results.

Sun–Jupiter–Saturn System May Exist: A Verified Computation of Quasiperiodic Solutions for the Planar Three-Body Problem

In this paper, we present evidence of the stability of a model of our Solar System when taking into account the two biggest planets, a planar (Newtonian) Sun–Jupiter–Saturn system with realistic data: masses of the Sun and the planets, their semiaxes, eccentricities and (apsidal) precessions of the planets close to the real ones. (We emphasize that our system is not in the perturbative regime but for fixed parameters.) The evidence is based on convincing numerics that a KAM theorem can be applied to the Hamiltonian equations of the model to produce quasiperiodic motion (on an invariant torus) with the appropriate frequencies. To do so, we first use KAM numerical schemes to compute translated tori to continue from the Kepler approximation (two uncoupled two-body problems) up to the actual Hamiltonian of the system, for which the translated torus is an invariant torus. Second, we use KAM numerical schemes for invariant tori to refine the solution giving the desired torus. Lastly, the convergence of the KAM scheme for the invariant torus is (numerically) checked by applying several times a KAM–iterative lemma, from which we obtain that the final torus (numerically) satisfies the existence conditions given by a KAM theorem.

2019 UO14: A Transient Trojan of Saturn

Saturn has long been the only giant planet in our solar system without any known Trojan members. In this Letter, with serendipitous archival observations and refined orbit determination, we report that 2019 UO14 is a Trojan of the gas giant. However, the object is only a transient Trojan currently librating around the leading Lagrange point L 4 of the Sun–Saturn system in a period of ∼0.7 kyr. Our N-body numerical simulation shows that 2019 UO14 was likely captured as a Centaur and became trapped around L 4 ∼ 2 kyr ago from a horseshoe co-orbital. The current Trojan state will be maintained for another millennium or thereabouts before transitioning back to a horseshoe state. Additionally, we characterize the physical properties of 2019 UO14. Assuming a linear phase slope of 0.06 ± 0.01 mag deg−1, the mean r-band absolute magnitude of the object was determined to be H r = 13.11 ± 0.07, with its color measured to be consistent with that of Jupiter and Neptune Trojans and not statistically different from Centaurs. Although the short-lived Saturn Trojan exhibited no compelling evidence of activity in the observations, we favor the possibility that it could be an active Trojan. If confirmed, 2019 UO14 would be marked as the first active Trojan in our solar system. We conservatively determine the optical depth of dust within our photometric aperture to be ≲10−7, corresponding to a dust mass-loss rate to be ≲1 kg s−1, provided that the physical properties of dust grains resemble Centaur 29P/Schwassmann–Wachmann 1.

Modified method of round Gaussian rings. Application to the two-planetary problem

A scheme of the modified method of round Gaussian rings, designed to study the secular evolution of orbits in systems consisting of a central star and two planets, is presented. The reason for the secular evolution of the nodes and inclinations of the orbits of the planets is their mutual gravitational attraction. The orbits of the planets are modeled by homogeneous round Gaussian rings, to which the masses, sizes and angles of inclination of the orbits, as well as orbital angular momenta of the planets, are transferred. The method takes into account the fact that, in general, the ascending nodes of the orbits may not coincide. The mutual gravitational energy of the rings 𝑊𝑚𝑢𝑡 is represented as a series in the quadratic approximation in powers of small inclination angles. Using this function 𝑊𝑚𝑢𝑡, a closed system of four differential equations describing the secular evolution of the planets’ orbits is composed. The solution to the equations is obtained in finite analytic form, which simplifies the interpretation of the investigated planetary motions. The method was tested on the example of the Sun-Jupiter-Saturn system; for it, in particular, the difference in the longitudes of the nodes of the orbits of Jupiter and Saturn was calculated as a function of time. New approach is also used to study the precession of nodes in the exoplanetary system K2-36; graphs of all unknown quantities are obtained. It has been established that in the course of evolution the mutual inclination angle of the orbits remains constant, and the librations of the orbits in the inclination angle and in the motion of the nodes occur synchronously.

Evidence for phospholipid self-organisation in concentrated ammonia-water environments

Titan, the largest moon of Saturn is thought to have the potential to support primordial life. The surface of Titan contains bodies of liquid hydrocarbons, and modelling suggests that an ammonia-water ocean resides deep beneath the surface, both of which have been speculated to support primordial chemistry. Here we present the first evidence that both preformed and self-organised phospholipid vesicles remain stable and can maintain concentration gradients in ammonia-water environments; a fundamental requirement for primordial chemistry and biology to originate. We further reveal the remarkable stability of a diether phospholipid, such as those found in extremophilic bacteria, under these conditions and demonstrate that electron microscopy and tomography are useful tools to investigate macromolecular structure under diverse physico-chemical environments.

Redshifted Sodium Transient near Exoplanet Transit

Neutral sodium (Na i) is an alkali metal with a favorable absorption cross section such that tenuous gases are easily illuminated at select transiting exoplanet systems. We examine both the time-averaged and time-series alkali spectral flux individually, over 4 nights at a hot Saturn system on a ∼2.8 day orbit about a Sun-like star WASP-49 A. Very Large Telescope/ESPRESSO observations are analyzed, providing new constraints. We recover the previously confirmed residual sodium flux uniquely when averaged, whereas night-to-night Na i varies by more than an order of magnitude. On HARPS/3.6 m Epoch II, we report a Doppler redshift at v Γ,NaD = + 9.7 ± 1.6 km s−1 with respect to the planet’s rest frame. Upon examining the lightcurves, we confirm night-to-night variability, on the order of ∼1%–4% in NaD, rarely coinciding with exoplanet transit, not readily explained by stellar activity, starspots, tellurics, or the interstellar medium. Coincident with the ∼+10 km s−1 Doppler redshift, we detect a transient sodium absorption event dF NaD/F ⋆ = 3.6% ± 1% at a relative difference of ΔF NaD(t) ∼ 4.4% ± 1%, lasting Δt NaD ≳ 40 minutes. Since exoplanetary alkali signatures are blueshifted due to the natural vector of radiation pressure, estimated here at roughly ∼−5.7 km s−1, the radial velocity is rather at +15.4 km s−1, far larger than any known exoplanet system. Given that the redshift magnitude v Γ is in between the Roche limit and dynamically stable satellite orbits, the transient sodium may be a putative indication of a natural satellite orbiting WASP-49 A b.

Mutation Operator for Resonance Flybys in Moon Tour Design Optimization

The global optimization of the moon tour design problem is addressed in this paper. These missions are usually designed using graphical methods or grid search, which require simplifying assumptions, and a skillful mission designer. The grid search methods are computationally intense. Trajectories with a high number of flybys and multiple resonance flybys are usually hard to optimize, especially with small-size/short-period flyby moons. This work proposes a new mutation operator that is incorporated with the Monotonic Basin Hopping in the Evolutionary Mission Trajectory Generator tool; this mutation operator increases the exploration of resonance flybys to improve convergence in moon tour design optimization problems. In this work, the Hidden Genes Genetic Algorithm is used to optimize the undetermined number of moon flybys. A Europa Clipper-like mission is optimized assuming two-body dynamics, and a validation study for the proposed resonance mutation operator is presented. The results include an optimized baseline solution and a new solution with a different sequence of flybys with a different sequence of flybys for the Europa Clipper-like mission, in addition to an optimized moon tour in the Saturnian system.

Looking for Subsurface Oceans Within the Moons of Uranus Using Librations and Gravity

AbstractSeveral of the icy moons in the Jupiter and Saturn systems appear to possess internal liquid water oceans. Our knowledge of the Uranian moons is more limited but a future tour of the system has the potential to detect subsurface oceans. Planning for this requires an understanding of how the moons' internal structures—with and without oceans—relate to observable quantities. Here, we show that the amplitude of forced physical librations could be diagnostic of the presence or absence of subsurface oceans within the Uranian moons. In the presence of a decoupling global ocean, ice shell libration amplitudes at Miranda, Ariel, and Umbriel will exceed 100 m if the shells are thick. The presence of oceans could also imply significant tidal heating within the last few hundred million years. Combining librations with the quadrupole gravity field could provide comprehensive constraints on the internal structures and histories of the Uranian moons.

Collision induced absorption spectra of N2 and CH4

Collision-induced absorption (CIA) spectra of nitrogen and methane are needed to model radiative transfer in atmospheres of objects such as Saturn's moon, Titan. We present rare, extremely low temperature Fourier transform infrared spectra of nitrogen and methane rototranslation CIA in the range of 40–600 cm−1. The peak CIA of methane was found to be 2.05×10−5 cm−1/amagat2 at 123.8 K while nitrogen had a peak value of 1.65×10−5 cm−1/amagat2 at an average temperature of 102.5 K. These measurements were made possible by the unique instrumentation available at the Far-IR beamline at the Canadian Light Source.

Flexible Bridge-Conic Strategies for Moon-to-Moon Analytical Transfer Design

The multi-burn transfer framework based on the moon-to-moon analytical transfer method allows rapid patching of low-energy trajectories in the vicinity of different moons in a planetary system. However, the semimajor axis and eccentricity of intermediate arcs of one transfer mission are fixed in the existent multi-burn strategies. Additional propellant consumption is required to enable the transfers at all departure epochs, and a nonanalytical formulation still remains for transferring to spatial periodic orbits. To address these difficulties, new multi-burn strategies with variable intermediate arcs are proposed to meet the transfer conditions for different types of arrival orbits. Specifically, one or two intermediate arcs with one variable parameter are introduced and can be determined analytically. In numerical simulations, the proposed flexible bridge-conic strategies are applied to design transfers between libration point orbits in both the Jovian and Saturnian systems. Final results validate the effectiveness of the proposed strategies and indicate the important advantage in propellant saving compared with the existent multi-burn strategies.

Alternative Pathways in Astrobiology: Reviewing and Synthesizing Contingency and Non-Biomolecular Origins of Terrestrial and Extraterrestrial Life.

The pursuit of understanding the origins of life (OoL) on and off Earth and the search for extraterrestrial life (ET) are central aspects of astrobiology. Despite the considerable efforts in both areas, more novel and multifaceted approaches are needed to address these profound questions with greater detail and with certainty. The complexity of the chemical milieu within ancient geological environments presents a diverse landscape where biomolecules and non-biomolecules interact. This interaction could lead to life as we know it, dominated by biomolecules, or to alternative forms of life where non-biomolecules could play a pivotal role. Such alternative forms of life could be found beyond Earth, i.e., on exoplanets and the moons of Jupiter and Saturn. Challenging the notion that all life, including ET life, must use the same building blocks as life on Earth, the concept of contingency-when expanded beyond its macroevolution interpretation-suggests that non-biomolecules may have played essential roles at the OoL. Here, we review the possible role of contingency and non-biomolecules at the OoL and synthesize a conceptual model formally linking contingency with non-biomolecular OoL theories. This model emphasizes the significance of considering the role of non-biomolecules both at the OoL on Earth or beyond, as well as their potential as agnostic biosignatures indicative of ET Life.

Unveiling the Reaction Mechanism of the N(2D) + Pyridine Reaction: Ring-Contraction versus 7-Membered-Ring Formation Channels.

Despite the relevance of the reactions of the prototypical nitrogen-containing six-membered aromatic molecule (N-heterocyclic) of pyridine (C6H5N) in environmental science, astrochemistry, planetary science, prebiotic chemistry, and materials science, few experimental/theoretical studies exist on the bimolecular reactions involving pyridine and neutral atomic/molecular radicals. We report a combined experimental and theoretical study on the elementary reaction of pyridine with excited nitrogen atoms, N(2D), aimed at providing information about the primary reaction products and their branching fractions (BFs). From previous crossed molecular beam (CMB) experiments with mass-spectrometric detection and present synergistic calculations of the reactive potential energy surface (PES) and product BFs we have unveiled the reaction mechanism. It is found that the reaction proceeds via N(2D) barrierless addition to pyridine that, via bridged intermediates followed by N atom "sliding" into the ring, leads to 7-membered-ring structures. They further evolve, mainly via ring-contraction mechanisms toward 5-membered-ring radical products and, to a smaller extent, via H-displacement mechanisms toward 7-membered-ring isomeric products and their isomers. Using the theoretical statistical estimates, an improved fit of the experimental data previously reported has been obtained, leading to the following results for the dominant product channels: C4H4N (pyrrolyl) + HCN (BF = 0.61 ± 0.20), C3H3N2 (1H-imidazolyl/1H-pyrazolyl) + C2H2 (BF = 0.11 ± 0.06), and C5H4N2 (7-membered-ring molecules or pyrrole carbonitriles) + H (BF = 0.28 ± 0.10). The ring-contraction product channels C4H4N (pyrrolyl) + HCN, C3H3N2 (1H-imidazolyl) + C2H2, C3H3N2 (1H-pyrazolyl) + C2H2, and C5H5 (cyclopentadienyl) + N2 have statistical BFs of 0.54, 0.09, 0.11, and 0.07, respectively. Among the H-displacement channels, the cyclic-CHCHCHCHNCN + H channel and cyclic-CHCHCHCHCN2 + H are theoretically predicted to have a comparable BF (0.07 and 0.06, respectively), while the other isomeric 7-membered-ring molecule + H channel has a BF of 0.03. Pyrrole-carbonitriles and 1H-ethynyl-1H-imidazole (+ H) isomeric channels have an overall BF of 0.03. Implications for the chemistry of Saturn's moon Titan and prebiotic chemistry, as well as for understanding the N-doping of graphene or carbon nanotubes, are noted.

The Astrobiological Potential of the Uranian Moon System.

The 2023-2032 Planetary Science and Astrobiology Decadal Survey prioritized the Uranus Orbiter and Probe (UOP) mission concept as the next priority flagship mission. The UOP concept includes scientific studies of the Uranian moon system. Although the Uranian moons differ greatly from the ocean worlds in the Jovian and Saturnian systems, the emerging hypothesis is that some of them could at least sustain thin, potentially concentrated, oceans. Herein, we make a case that these moons are important and interesting targets of astrobiological research. Studying these worlds would provide critical astrobiological data related to their habitability, including origin, evolution, and potential death, as well as the formation and evolution of ocean worlds more broadly. There is a strong need for research that connects astrobiology to modeling and experimentation to better characterize the possible conditions of these worlds, and this will be critical in formulating and maximizing the potential science that could be done by a Uranus flagship mission.

Remarks on the possibility of deep space travel to potentially habitable satellites like Titan and Europa

The vast expanse of space beckons us with the promise of discovery and the potential for finding new homes for humanity. This paper explores the feasibility of deep space travel, specifically focusing on missions to potentially habitable satellites like Titan (Saturn's moon) and Europa (Jupiter's moon), which possible have liquid water on their surface or atmosphere. We discuss the technological advancements required for such endeavors, considering challenges like propulsion systems, life support, and radiation shielding. The paper analyzes the unique environments of Titan and Europa, highlighting their potential for harboring life and the possibility of terraforming them to create suitable habitats for humans. Finally, we explore the ethical considerations surrounding and the importance of international collaboration in achieving this possible deep space travel.

A Hamiltonian for 1/1 rotational secondary resonances, and application to small satellites of Saturn and Jupiter

In this work, we study the dynamics of rotation of the small satellites Methone and Aegaeon and revisit previous works on the rotation of Prometheus, Metis, and Amalthea. In all cases, the surfaces of section computed with the standard spin–orbit model reveal that the synchronous regime with small amplitude of libration shares another large domain in the phase space. We reproduce and apply the hamiltonian theory given in Wisdom 2004 [1] to analytically characterize the detected structure as being a secondary resonance where the period of the physical libration is similar to the orbital period of the satellite. We also show that the amplitude of libration in the secondary resonance is always larger than in the case of the other mode. Since the current rotational states of these sorts of satellites should be synchronous, our results can be considered in evolutionary studies of their rotation.

An inorganic silicate simulant to represent the interior of enceladus

Enceladus, an icy moon of Saturn, consists of an ice shell, global subsurface ocean and a silicate interior. By sampling plume material, the Cassini spacecraft found evidence of ongoing water-rock reactions between the silicate interior and the subsurface ocean. These data showed that these reactions provide a source of bioessential elements to the ocean, making Enceladus one of the leading astrobiological targets in our Solar System. Understanding these water-rock reactions is critical in understanding the potential habitability of Enceladus. To study these reactions experimentally, a chemical simulant to represent the contemporary silicate interior of Enceladus has been designed. Based on the available interpretations of Cassini data about the density, chemical composition, and aqueous alteration of the interior, the chosen starting point for the simulant is a CI chondrite. However, Enceladus is still undergoing active aqueous alteration, thus its silicate mineral assemblage cannot have reached the fully altered assemblage seen in a CI chondrite. To account for this, adaptations have been made to a CI chondrite mineral assemblage, extrapolating back to an assemblage of less aqueously altered minerals whilst maintaining the same chemical composition in terms of major oxide phases. Thus, the chemical and mineralogical composition of this simulant represents a best estimate of the silicate components in the ongoing water rock interactions on Enceladus today.

Ephemeris accuracy improvement for moons of gas giants: a deep learning based method

Ephemerides accuracy of gas giant planetary system is of paramount importance in astronomical research, planetary exploration missions, and space navigation. Traditional mathematical methods face challenges when processing with data of different observation precisions, which may lead to extra noise and reduce the ephemeris accuracy. This paper proposes an Denoising Autoencoder based Method for Ephemeris Improvement (DAMEI) to improve the accuracy of ephemerides for moons in gas giant planetary system. Utilizing multiple sources of data efficiently, the DAMEI method can mitigate the impact of noise and uncertainty introduced by observational data with different precisions. Based on the symmetrical structure, the DAMEI method learns to encode essential motion features of gas giant planetary system into a latent space and captures the intricate patterns in planetary motion from observational data, subsequently decodes it to improve the ephemeris accuracy. The experimental results show that, for Jupiter’s major satellites (Galilean moons), the DAMEI method achieves more accurate ephemeris of up to 91.65% compared with current mathematical method. The proposed method is also assessed with satellites of Saturn, Uranus, and Neptune. It is shown that the DAMEI method also presents a better performance of up to 95.37%. The promising performance of DAMEI method can reduce the uncertainty introduced by low-accuracy data and improve ephemeris accuracy making the utmost of observational data with different precisions.

Impacts of Hydrostatic Pressure on Distributed Temperature-Sensing Optical Fibers for Extreme Ocean and Ice Environments

Optical fiber is increasingly used for both communication and distributed sensing of temperature and strain in environmental studies. In this work, we demonstrate the viability of unreinforced fiber tethers (bare fiber) for Raman-based distributed temperature sensing in deep ocean and deep ice environments. High-pressure testing of single-mode and multimode optical fiber showed little to no changes in light attenuation over pressures from atmospheric to 600 bars. Most importantly, the differential attenuation between Stokes and anti-Stokes frequencies, critical for the evaluation of distributed temperature sensing, was shown to be insignificantly affected by fluid pressures over the range of pressures tested for single-mode fiber, and only very slightly affected in multimode fiber. For multimode fiber deployments to ocean depths as great as 6000 m, the effect of pressure-dependent differential attenuation was shown to impact the estimated temperatures by only 0.15 °K. These new results indicate that bare fiber tethers, in addition to use for communication, can be used for distributed temperature or strain in fibers subjected to large depth (pressure) in varying environments such as deep oceans, glaciers and potentially the icy moons of Saturn and Jupiter.

Early Feasibility Study with the SATURN Transapical Mitral Valve Replacement Device

PurposeTo report the outcomes of the early feasibility study of transapical transcatheter mitral valve replacement (TMVR) with the SATURN System (InnovHeart, Milano, Italy) to treat patients with severe functional mitral regurgitation. DescriptionFive high surgical risk patients underwent transapical transcatheter mitral valve replacement with the SATURN System at a single center. One-year follow-up is complete for all patients. EvaluationThe valve was implanted successfully in all patients without any major adverse events. All patients were alive at the last follow-up. Kansas City Cardiomyopathy Questionnaire improved from a median of 63.5 (interquartile range, 19.6) at baseline to 99.0 (interquartile range, 21.6) at 1 year. Echocardiographic follow-up demonstrates stable valve function, no transvalvular or paravalvular mitral regurgitation, and absence of left ventricular outflow tract obstruction. ConclusionsAt 1 year after transapical SATURN transcatheter mitral valve replacement, all patients are alive with quality of life improvement and favorable device hemodynamics. These initial results are promising and larger scale studies with continued follow-up are required to further elucidate the efficacy and safety of this novel technology.