Rings Of Saturn Research Articles

Near-infrared Spectroscopy for Remote Sensing of Porosity, Density, and Cubicity of Crystalline and Amorphous H2O Ices in Astrophysical Environments

We present laboratory spectra of pure amorphous and crystalline H2O ices in the near-infrared (NIR, 1–2.5 μm/10,000–4000 cm−1) at 80–180 K. The aim of this study is to provide spectroscopic reference data that allow remotely accessing ice properties for icy objects such as icy moons, cometary ice, or Saturn rings. Specifically, we identify new spectral markers for assessing three important properties of ices in space: (i) porosity/fluffiness, (ii) bulk density of amorphous ice, and (iii) cubicity in crystalline ice. The analysis is based on the first OH-stretching overtone (2ν OH) and the combinational band at 5000 cm−1/2 μm, which are potent spectral markers for these properties. By comparison of vapor-deposited, microporous amorphous solid water, pore-free low-, high-, and very-high-density amorphous ice, we are able to separate the effect of (bulk) density from the effect of porosity on NIR-spectra of amorphous ices. This allows for clarifying a longstanding inconsistency about the density of amorphous ice vapor-deposited at low temperatures, first brought up by Jenniskens & Blake. Direct comparison of NIR spectra with powder X-ray diffractograms allows us to correlate spectral features with the number of cubic stacking layers in stacking-disordered ice Isd, ranging from fully cubic ice Ic to fully hexagonal ice Ih. We show that exposure times for instruments on the James Webb Space Telescope are in the hour range to distinguish these properties, demonstrating the usefulness of the neglected NIR spectral range for identifying ices in space.

Relaxed magnetic structures in the Saturn's ring

Relaxed magnetic structures in the Saturn's ring

The Aeolian harp sound from the Madelung model of quantum mechanics

According to Madelung, Bohm and Vigier, Wilhelm, Rosen and others, the original Schroedinger equation can be transformed into the hydrodynamical system of equations by using the so called Madelung ansatz. We derive in such quantum hydrodynamics, the non-relativistic and relativistic Strouhal number from the so called von Karman's vortex street. The relativistic derivation of this formula follows from the addition formula for velocities. The Strouhal friction tones are generated also during the motion of cosmic rays in relic photon sea, during the motion of bolids in atmosphere, during the Saturn rings motion in the relic black-body sea, during the motion of bodies in superfluid helium and so on.

Astrometry of Cassini ISS Images of 7 Near-ring Inner Satellites of Saturn Affected by Scattered Light

The Imaging Science Subsystem (ISS) mounted on Cassini spacecraft took images of Saturn’s inner satellites between 2004 and 2017. In some of these images, the satellites are so close to Saturn rings that their images are affected by the scattered light from Saturn rings, which results in poor even impossible measurements of targets. A background removal algorithm is proposed to measure such images. A total of 70 ISS images of seven inner satellites near Saturn rings (Janus, Epimetheus, Atlas, Prometheus, Pandora, Methone, and Anthe) have been reduced by using the proposed method. Compared with the results from the method without removing the background affected by scattered light, the proposed method demonstrates an improvement in accuracy of at least 43%. The final results show that the residuals of these measurements relative to the JPL (Jet Propulsion Laboratory) ephemeris SAT415 have means of about 0.72 km and 2.26 km in right ascension and declination, with standard deviations of 10.99 km and 11.36 km, respectively.

Water‐Ice Dominated Spectra of Saturn's Rings and Small Moons From JWST

AbstractJWST measured the infrared spectra of Saturn's rings and several of its small moons (Epimetheus, Pandora, Telesto, and Pallene) as part of Guaranteed Time Observation program 1247. The NIRSpec instrument obtained near‐infrared spectra of the small moons between 0.6 and 5.3 microns, which are all dominated by water‐ice absorption bands. The shapes of the water‐ice bands for these moons suggests that their surfaces contain variable mixes of crystalline and amorphous ice or variable amounts of contaminants and/or sub‐micron ice grains. The near‐infrared spectrum of Saturn's A ring has exceptionally high signal‐to‐noise between 2.7 and 5 microns and is dominated by features due to highly crystalline water ice. The ring spectrum also confirms that the rings possess a 2%–3% deep absorption at 4.13 microns due to deuterated water ice previously seen by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft. This spectrum also constrains the fundamental absorption bands of carbon dioxide and carbon monoxide and may contain evidence for a weak aliphatic hydrocarbon band. Meanwhile, the MIRI instrument obtained mid‐infrared spectra of the rings between 4.9 and 27.9 microns, where the observed signal is a combination of reflected sunlight and thermal emission. This region shows a strong reflectance peak centered around 9.3 microns that can be attributed to crystalline water ice. Since both the near and mid‐infrared spectra are dominated by highly crystalline water ice, they should provide a useful baseline for interpreting the spectra of other objects in the outer solar system with more complex compositions.

Low-velocity impact experiments of porous ice balls simulating Saturn's ring particles: Porosity dependence of restitution coefficients and the mechanism of inelastic collision

We investigated the porosity dependence of the restitution coefficient (ε) of porous ice balls with porosities of 49.6%, 53.8%, and 60.8% colliding with granite, ice and porous ice plates at a low impact velocity (vi = 0.93–96.9 cm s−1) and temperature of −13.8 °C. The relationship between the impact velocity and the restitution coefficient was divided into two regions by the critical velocity vc: In the quasi-elastic region (vi≤vc), the restitution coefficient had a constant value of εqe regardless of the impact velocity and could be explained by using Dilley's viscous dissipation model. In the inelastic region (vi≥vc), the restitution coefficient decreased with the impact velocity and could be explained by using the improved Andrews' plastic deformation model. We then determined the porosity dependence of the εqe and vc empirically for collisions between the porous ice ball and the porous ice plate from our results. Then we extrapolated the porosity dependence of the restitution coefficient by substituting the calculated εqe and vc for the porosity of 10 to 70%. The restitution coefficient was found to decrease with increasing porosity of the porous ice, and to be strongly dependent on the porosity of the porous ice. Considering the energy budget in the steady-state dense ring system which is controlled by the restitution coefficient of the ring particles, the velocity dispersion of the ring particles was estimated to be ∼10−2 mm s−1 to cm s−1 for the ring particles with the porosity from 45% to 70% and < 10–90 cm s−1 for those with the porosity <45%.

Defect-influenced particle advection in highly confined liquid crystal flows.

We study the morphology of the Saturn ring defect and director structure around a colloidal particle with normal anchoring conditions and within the flow of the nematic host phase through a rectangular duct of comparable size to the particle. The changes in the defect structures and director profile influence the advection behaviour of the particle, which we compare to that in a simple Newtonian host phase. These effects lead to a non-monotonous dependence of the differential velocity of particle and fluid, also known as retardation ratio, on the Ericksen number.

Concepts of “Trauma” and “Memory” in W. G. Sebald’s Book Luftkrieg und Literatur (On the Natural History of Destruction)

This year, the second year of the Russian-Ukrainian war, a book by the German author W. G. Sebald (1944-2001), On the Natural History of Destruction, was published in Ukrainian translation by IST Publishing. I must say that reading Sebald's works translated by Roman Osadchuk is a distinct pleasure. This is the third book by Sebald translated into Ukrainian by R. Osadchuk. Before this one, Austerlitz and The Rings of Saturn were published by Komubook. Sebald is one of the few authors I discovered for myself during the war. His Austerlitz was a breath of fresh air at a time when I couldn't bring myself to read or write.

Statics and dynamics of point boojums, line and modified Saturn ring topological defects in nematic confined geometry.

In this paper we study the static structure and the dynamics of topological defects associated with isotropic droplets in nematic environment. Investigations were made in confined geometry of optical cells when the droplet size was of the order of or larger than the gap of the cell. We observed the coexistence of point boojums and Saturn ring or modified Saturn ring defects. We found transformation of the Saturn ring defect to two localized broad defects at increasing the droplet size. At droplet coalescence antipodes of point and localized broad defects were born and the dynamics of their annihilation with existing defects was investigated. We found strong difference in the process of annihilation of point and localized broad defects. Microscope images of isotropic droplets in nematic environment in a planar cell. The director orientation far from the droplets is in horizontal direction. The photographs were taken with crossed vertical and horizontal polarizers (a) and with a single horizontal polarizer (b). The cell thickness is 100μm. Droplet diameter is less than the cell thickness. 1 and 2 are point boojums, L is the Saturn ring defect.

Quick Hits: The explosive secret behind Saturn's rings, a Scandinavian arrow frozen for 4,000 years, the world's deepest-known virus, and much more in this month's Quick Hits.

Quick Hits: The explosive secret behind Saturn's rings, a Scandinavian arrow frozen for 4,000 years, the world's deepest-known virus, and much more in this month's Quick Hits.

Effective resection of dermatofibrosarcoma protuberans using the novel Saturn's rings technique.

Dermatofibrosarcoma protuberans (DFSP) is a rare, low-grade sarcoma with locally infiltrative characteristics. A wide excision is made with a 5 cm gross margin. However, recently, Mohs micrographic surgery has emerged as an alternative. In this study, we evaluate a novel method (Saturn's Rings technique) for removing tumors that combines the advantages of wide excision and Mohs micrographic surgery. Between September 2001 and March 2020, 29 patients with DFSP, excluding the head and neck, were treated using Saturn's rings technique. Frozen biopsies were performed at regular intervals under various conditions and depths. If the biopsy was positive, a negative margin was obtained through an additional session. The depth and breadth of excision, reconstruction method, and postoperative recurrence were analyzed. The breadth of excision was evaluated at 1 cm intervals. Only 1 session was required in 12 cases, 2 sessions were needed in 13 cases, and 3 or more sessions were performed in 4 cases. In 24 cases, the depth of excision was limited to above the superficial fascia, with a negative biopsy of the superficial fascia. Local flaps were the most common reconstruction method (n = 21, 72.4%). No cases of recurrence were observed at follow-up (average, 45.7 months). Saturn's rings technique for DFSP maximized the preservation of normal tissue with minimal resection, was advantageous for reconstruction, and yielded good results without recurrence.

Consequence of head-on collision of ion acoustic waves in unmagnetized plasmas having generalized (r, q) distributed electrons and positrons

To explore the effect of the head-on collision (such as phase shifts, collisional processes, and production of solitons) of ion-acoustic waves (IAWs), a collisionless unmagnetized electron-positron-ion (e-p-i) plasma is considered. The electrons and positrons follow the generalized () distribution. To do this, using the extended Poincaré-Lighthill-Kuo (ePLK) approach, the two-sided Korteweg-de Vries (KdV) equations and phase shifts are derived. The main aim of this study is to investigate the consequence of spectral indices and on both the negative and positive phase changes following an IAW-to-IAW collision. It is found that for the effects of the spectral indices of electrons and positrons both positive and negative phase shifts after head-on collisions are modified. The compressive (only hump-shaped) as well as rarefactive (both hump and dip-shaped) solitons become produced for the effect of spectral indices. The results obtained in the study may be helpful to understand the collision processes as well as the consequence of the head-on collision of IAWs in electron-positron-ion plasmas in the ionosphere, auroral acceleration regions, solar wind, Saturn rings, active galactic nuclei, polar cup of fast rotating neutron stars, semiconductor plasmas, and intense laser fields as well as in laboratory experiment.

Dwindling Surface Cooling of a Rotating Jovian Planet Leads to a Convection Zone That Grows to a Finite Depth

Recent measurements of Jupiter's gravitational field (by Juno) and seismology of Saturn's rings (by Cassini) strongly suggest that both planets have a stably stratified core that still possesses a primordial gradient in the concentration of heavy elements. The existence of such a “diffusely” stratified core has been a surprise as it was long expected that the Jovian planets should be fully convective and hence fully mixed. A vigorous zone of convection, driven by surface cooling, forms at the surface and deepens through entrainment of fluid from underneath. In fact, it was believed that this convection zone should grow so rapidly that the entire planet would be consumed in less than a million years. Here we suggest that two processes, acting in concert, present a solution to this puzzle. All of the giant planets are rapidly rotating and have a cooling rate that declines with time. Both of these effects reduce the rate of fluid entrainment into the convection zone. Through the use of an analytic prescription of entrainment in giant planets, we demonstrate that these two effects, rotation and dwindling surface cooling, result in a convection zone that initially grows but eventually stalls. The depth to which the convective interface asymptotes depends on the rotation rate and on the stratification of the stable interior. Conversely, in a nonrotating planet, or in a planet that maintains a higher level of cooling than current models suggest, the convection zone deepens forever, eventually spanning the entire planet.

A new perspective on drift waves in self-gravitating magnetized quantum plasma

The quantum hydrodynamic model is used in this study to investigate electrostatic waves in a non-uniform, quantum magnetized dusty plasmas while accounting for dust gravitational effects. Quantum effects for dust grains are omitted, and ions and electrons are considered low-temperature Fermi gases. The generalized analytical dispersion relationship for the dust gravitation drift (DGD) wave is derived. The temperature dependence of the environment induces quantum effects which have been shown to have a significant impact on wave dispersion. In the absence of gravitational effects at high temperature, the fundamental dust drift mode has been reproduced. The criteria and the transitioning regimes are presented. Our findings apply to dense astrophysical objects such as the Enceladus encounter in the E ring of Saturn.

A Past Episode of Rapid Tidal Evolution of Enceladus?

Saturn possesses a dynamically rich system containing numerous moons and impressive rings. Whether the rings of Saturn are much younger than the planet itself has been a long-standing open question; more recently a young age has been proposed for some moons. The recent detection of the fast orbital evolution of Rhea and Titan strongly suggests a highly frequency-dependent tidal response of Saturn, possibly through the excitation of inertial waves within the planet’s convective envelope. Here we show that resonance locking to inertial waves cannot explain the dynamical structure of the Saturnian system or the current tidal heating of Enceladus. On the other hand, both the observations and our modeling results indicate that the system is not consistent with evolution under equilibrium tides. We propose that the system’s architecture can best be explained by a relatively high “background” tidal response coupled with discrete resonant modes. In this view, only Titan may be in a true long-term resonance lock with a tidal mode of Saturn. Rhea is most likely currently experiencing a transient period of fast tidal evolution as it passes through a mode, rather than being locked into it. Assuming that Enceladus went through a temporary period of fast tidal evolution, we can reproduce its present resonance with Dione and satisfy other dynamical constraints. Additionally, we conclude that the long-term tidal response of Saturn to Tethys must be weaker than expected from frequency-independent tides, as already found by observations.

Mimas: Frozen Fragment, Ring Relic, or Emerging Ocean World?

Mimas, the smallest and innermost of Saturn's mid-sized moons, has a heavily cratered surface devoid of the intricate fracture systems of its neighbor, Enceladus. However, Cassini measurements identified a signature of an ocean under Mimas’ ice shell, although a frozen ice shell over a rocky interior could not be ruled out. The Mimas ocean hypothesis has stimulated inquiry into Mimas’ geologic history and orbital evolution. Here, we summarize the results of these investigations, which (perhaps surprisingly) are consistent with an ocean-bearing Mimas as long as it is geologically young. In that case, a ring origin for Mimas is favored over primordial accretion. An independently developed model for the formation of a gap in Saturn's rings provides a potential mechanism for generating a late-stage ocean within Mimas and may have assisted in the development of Enceladus’ ocean and associated geologic activity. Rather than a battered relic, Mimas may be the youngest ocean moon in the Saturn system, destined to join Enceladus as an active world in the future. The presence of oceans within Saturn's mid-sized moons also has implications for the habitability of Uranus’ moons; the Uranus system was chosen as the highest priority target for the next NASA Flagship-class mission. ▪ Models of Mimas’ tides and rotation state support a present-day internal ocean. ▪ Mimas’ craters, impact basin, and lack of widespread tectonism are compatible with a stable/warming ocean. ▪ The formation of the Cassini Division within Saturn's rings provides a potential pathway to a present-day ocean within Mimas. ▪ If Mimas has an ocean today, it is geologically young.

Editorial

Editorial

Twist-bend nematic drops as colloidal particles: Structural features.

The mesogen CB7CB [1″,7″-bis(4-cyanobiphenyl-4'-yl)heptane], mixed with a small quantity of a long chain amphiphile, is examined for the structural features of twist-bend nematic (N_{TB}) drops acting as colloidal inclusions in the isotropic and nematic environments. In the isotropic phase, the drops nucleating in the radial (splay) geometry develop toward escaped radial, off-centered structures, involving both splay and bend distortions. With further growth, they transform into low-birefringence (near-homeotropic) objects, within which remarkably well-organized networks of parabolic focal conic defects evolve in time. In electrically reoriented near-homeotropic N_{TB} drops, the pseudolayers develop an undulatory boundary possibly attributable to saddle-splay elasticity. In the matrix of the planar nematic phase, N_{TB} droplets appearing as radial hedgehogs attain stability in the dipolar geometry, through their association with hyperbolic hedgehogs. With growth, on transformation of the hyperbolic defect into its topologically equivalent Saturn ring around the N_{TB} drop, the geometry turns quadrupolar. Significantly, dipoles are stable in smaller drops, while quadrupoles are stable in larger ones. The dipole-quadrupole transformation is reversible, but is hysteretic with respect to drop size. Importantly, this transformation is often mediated by nucleation of two loop disclinations, one appearing at a marginally lower temperature than the other. The existence of a metastable state with partial formation of a Saturn ring and persistence of the hyperbolic hedgehog raises a question relating to the conservation of topological charge. In twisted nematics, this state features in the formation of a giant unknot that binds all N_{TB} drops together.

“like standing amidst a flood of paper”: Tropes of Abundance and Documentarity in The Rings of Saturn

The paper scrutinizes the role of documents and documentarity in The Rings of Saturn by W. G. Sebald. It primarily focuses on those passages of the novel that represent the excessive amounts of documents via tropes of abundance and proliferation. I argue that the narrator’s meditations upon 20th century history paradoxically connect the overwhelming accumulation of documents to the experience of erasure and destruction; however, certain episodes offer another approach, presenting the collection of masses of documents as an idiosyncratic, poetic practice. In these parts of the text, documents are displayed as “heaps” and “clouds” of paper: I reveal the ways Sebald’s language deprives them of their referential function, calling attention to their materiality.

Hubble Detects the Start of a New Saturn Ring Spoke Season

AbstractSaturn's ring spokes typically appear over an 8‐year duration centered on equinox. Hubble Space Telescope observations in 2021 indicate the beginning of a new spoke season as Saturn approaches equinox in 2025. The spokes show increased contrast and longevity in 2022, persisting for up to 11 hours. The spokes are visible from UV to near‐IR and are slightly bluer (i.e., less red) than the rings, but we find no significant wavelength dependence in the spectral contrast, which approximates their optical depth). Spoke rotation rates are between 606 and 626 min, consistent with either Keplerian rotation or possibly the variable rotation rate of Saturn's kilometric radiation. Spoke activity is expected to increase over the next several years.