Satellite Titan Research Articles

Nuclear fusion powered Titan aircraft

This paper discusses a system for Titan exploration enabled by nuclear fusion power. Titan is one of the most interesting locations in the solar system with a thick atmosphere, surface oceans, under-ice oceans and complex terrain. This paper provides a conceptual design of a fusion-powered system to explore many parts of Titan and enable the use of high-power instruments. The design includes a fusion-powered orbital transfer vehicle and an electric Titan science aircraft. A Direct Fusion Drive (DFD) propulsive engine could bring a sizable spacecraft to Titan orbit in less than two years. A second fusion reactor, configured as a closed-loop power generator, would be used for an electric Titan science aircraft. Both reactors are based on the Princeton Field-Reversed Configuration (PFRC) concept which combines an FRC with a magnetic mirror. PFRC uses a novel radio-frequency plasma heating system and deuterium-helium-3 fuel. A lower temperature plasma flows around the closed-field FRC region removing the fusion products. In the DFD propulsive configuration, this secondary flow permits direct and variable thrust and exhaust velocity. The science aircraft would do a powered entry to Titan and then have the capability to fly anywhere on the moon at subsonic speeds. The DFD-powered transfer vehicle would allow the in-orbit transfer stage to change inclination as needed to cover different areas of the surface.

Modeling the Formation of Selk Impact Crater on Titan: Implications for Dragonfly

Selk crater is an ∼80 km diameter impact crater on the Saturnian icy satellite Titan. Melt pools associated with impact craters like Selk provide environments where liquid water and organics can mix and produce biomolecules like amino acids. It is partly for this reason that the Selk region has been selected as the area that NASA’s Dragonfly mission will explore and address one of its primary goals: to search for biological signatures on Titan. Here we simulate Selk-sized impact craters on Titan to better understand the formation of Selk and its melt pool. We consider several structures for the icy target material by changing the thickness of the methane clathrate layer, which has a substantial effect on the target thermal structure and crater formation. Our numerical results show that a 4 km diameter impactor produces a Selk-sized crater when 5–15 km thick methane clathrate layers are considered. We confirm the production of melt pools in these cases and find that the melt volumes are similar regardless of methane clathrate layer thickness. The distribution of the melted material, however, is sensitive to the thickness of the methane clathrate layer. In the case of a 10–15 km thick methane clathrate layer, the melt pool appears as a torus-like shape that is a few kilometers deep, and as a shallower layer in the case of a 5 km thick clathrate layer. Melt pools of this thickness may take tens of thousands of years to freeze, allowing more time for complex organics to form.

Lifetime and Dynamics of Natural Orbits around Titan

Considering the growing interest in sending probes to the natural satellite Titan, our work aims to investigate and map natural orbits around this moon. For that, we use mathematical models with forces that have symmetry/asymmetry phenomena, depending on the force, applied to orbits around Titan. We evaluated the effects due to the gravitational attraction of the Saturn, together with the perturbative effects coming from the non-sphericity of Titan (the gravitational coefficient J2) and the effects of the atmospheric drag present in the natural satellite. Lifetime maps were generated for different initial configurations of the orbit of the probe, which were analyzed in different scenarios of orbital perturbations. The results showed the existence of orbits surviving at least 20 years and conditions with shorter times, but sufficient to carry out possible missions, including the important polar orbits. Furthermore, the investigation of the oscillation rate of the altitude of the probe, called coefficient Δ, proposed in this work, showed orbital conditions that result in more minor oscillations in the altitude of the spacecraft.

Gravitational atmospheric tides as a probe of Titan’s interior: Application to Dragonfly

Context. Saturn’s massive gravity is expected to causes a tide in Titan’s atmosphere, producing a surface pressure variation through the orbit of Titan and tidal winds in the troposphere. The future Dragonfly mission could analyse this exotic meteorological phenomenon. Aims. We aim to analyse the effect of Saturn’s tides on Titan’s atmosphere and interior to determine how pressure measurements by Dragonfly could constrain Titan’s interior. Methods. We model atmospheric tides with analytical calculations and with a 3D global climate model (the IPSL-Titan GCM), including the tidal response of the interior. Results. We predict that the Love numbers of Titan’s interior should verify 1 + ℜ(k2 − h2) ~ 0.02–0.1 and ℑ(k2 − h2) < 0.04. The deformation of Titan’s interior should therefore strongly weaken gravitational atmospheric tides, yielding a residual surface pressure amplitude of only ~5 Pa, with a phase shift of 5–20 h. Tidal winds are very weak, of the order of 3 × 10−4 m s−1 in the lower troposphere. Finally, constraints from Dragonfly data may permit the real and the imaginary parts of k2 − h2 to be estimated with a precision of ±0.01–0.03. Conclusions. Measurements of pressure variations by Dragonfly over the whole mission could give valuable constraints on the thickness of Titan’s ice shell, and, via geophysical models, its heat flux and the density of its internal ocean.

A Titan mission using the Direct Fusion Drive

The main purpose of this work is to perform an analysis of realistic new trajectories for a robotic mission to Saturn’s largest moon, Titan, in order to demonstrate the great advantages related to the Direct Fusion Drive (DFD). The DFD is a D -23He fueled, aneutronic, thermonuclear fusion propulsion system (Cohen et al., 2019). This fusion propulsion concept is based on a magnetically confined field reversed configuration plasma, where the deuterium propellant is heated by fusion products, and then expanded into a magnetic nozzle, providing both thrust and electrical energy to the spacecraft. The trajectories calculations and analysis for the Titan mission are obtained based on the characteristics provided by the PPPL (Cohen et al., 2019) for a 2 MW-class DFD engine. Two different profile missions are considered: the first one is a thrust–coast–thrust profile with constant thrust and specific impulse, the second scenario is a continuous and constant thrust profile mission. Each mission study is divided into four different phases, starting from the initial low Earth orbit departure, the interplanetary trajectory, Saturn orbit insertion, and the Titan orbit insertion. For all mission phases, maneuver time and propellant consumption are calculated. The results of calculations and mission analysis offer a complete overview of the advantages in term of payload mass and travel time. It is important to emphasize that the deceleration capability is one of the DFD game changers: in fact, the DFD performance allows to rapidly reach high velocities and decelerate in even shorter time period. This capability results in a total trip duration of 2.6 years for the thrust–coast–thrust profile and less than 2 years for the continuous thrust profile. The high payload enabling capability, combined with the huge electrical power available from the fusion reactor leads to a tremendous advantage compared to present technology.

Hydrocarbons and degassing processes of Saturn’s satellite Titan

Research subject and methods. The paper presents a review of available information on the atmosphere of Titan and its surface, necessary for the development of concepts of hydrocarbon formation, including the natural hydrocarbon synthesis, formation of prebiogenic states and origin of life. The presence of vast reserves of abiogenic hydrocarbons on Titan is extremely important for the theory of hydrocarbon genesis on the Earth, since any concept of naphthogenesis claiming to be a consistent explanation of the entire set of available facts must take into account the possibility of abiogenic formation of large accumulations of hydrocarbons.Results. It was shown that the hydrocarbon diversity of the atmosphere and surface of Titan is provided by the inflow of endogenous methane. Degassing processes on Titan are characterized by specific forms due to their flow through a liquid medium: 1) “gas-lifting degassing” forming numerous small depressions with increased fluid levels and, possibly, being the cause of “magic islands” in the sea of Ligeia; 2) limnological emissions of gaseous methane, followed by intensive cloud formation, the development of methane storms and large amounts of precipitation.Conclusions. It is concluded that the presence of active degassing processes on Titan in combination with the emerging models of its internal structure contribute to clarifying the previously proposed scheme of primary natural hydrocarbon synthesis in the depths of Titan.

Diffraction-limited Titan Surface Imaging from Orbit Using Near-infrared Atmospheric Windows

Abstract The selection of Dragonfly enables regional Titan surface science, but global Titan geophysics, geology, hydrology, and meteorology require an orbiter. We consider the sources of signal and noise that would contribute to near-infrared surface imaging from such an orbiter both analytically and numerically. The fraction of light arriving at an orbiting camera directly from Titan’s surface, and therefore conveying full-resolution surface information, decreases at shorter wavelengths as additive atmospheric scatter and light blurred on the way out increase with higher haze optical depths. We apply the Monte Carlo radiative transfer model SRTC++ and show that up to 75% of observed flux in Titan’s 5 μm window comes directly from the surface, up to 47% comes directly at 2 μm, and up to just 7% comes directly in the 0.94 μm window. We find that diffraction-limited surface imaging with 10 m pixels is possible with a signal-to-noise ratio for surface features of 100 in the near-infrared at 5 and 2 μm using a 50 cm aperture. A Titan orbiter camera could image in color using 5 μm, 2 μm, and potentially other wavelengths using a pushbroom strategy with time-delay integration.

Convection in the Magnetosphere of Saturn During the Cassini Mission Derived From MIMI INCA and CHEMS Measurements

AbstractAn extensive analysis of Cassini Ion and Neutral Camera (INCA) and Charge Energy Mass Spectrometer (CHEMS) measurements of ~6–231 keV ion anisotropies acquired during selected spin and stare periods for nearly all mission orbits has been completed. Based on this analysis, we find that the computed azimuthal speed of Saturn's magnetodisk plasma increases within the inner and middle magnetosphere. Beyond the orbit of Titan, in the magnetotail, the calculated rotation speed remains roughly constant with increasing distance from Saturn. The component of convection parallel to Saturn's spin axis is smaller and on average nearly zero. The radial speed of plasma shows distinct local time dependence and increases outward with increasing distance down the magnetotail. The magnetodisk flow remains primarily azimuthal to large distances, indicating the plasma is still under the influence of Saturn as it transits across the nightside. Tailward flows have been observed in the region near the dawn and dusk magnetotail flanks. The plasma flow in the predawn quadrant is much more disorganized than that in the premidnight quadrant. The hydrogen and oxygen hot ion temperatures increase with decreasing distance to Saturn. Some plasma evidently escapes into a dusk boundary layer at the dusk magnetotail flank, while the remaining plasma primarily moves across the magnetotail and is entrained into the flow of a boundary layer at the dawn flank of the magnetotail. When scaled to the magnetopause standoff distance and corotation fraction, the convection speed of plasma in the magnetospheres of Jupiter and Saturn is similarly organized.

Ai intelligent industrial design of Titan space probe (landing capsule and Saturn vehicle)

Exploring the solar system is of great significance for the realization of the community of human destiny. This article reviews the history of Saturn exploration and explores new directions in design aesthetics. The author designed a new type of Saturn’s sixth satellite (Titan) with three-dimensional software 3dsmax, including a landing capsule, a cruise vehicle (Saturn vehicle), involving the design of quantum communication, automatic driving, neural chain Ai chips, mechanical arms, etc. “Lack of beauty and tediousness”, pursue “characteristics, cultural innovation”. The new detector, with exquisite shapes and beautiful lines, combines the eastern cultural symbols of “Zhouyi and Dunhuang Feitian”, and uses memory metal and three-dimensional printing to manufacture, expanding the new Higgs boson, neutrino, and non-carbon-based life Explore the field, named “Hetu Jishu”, which closely combines mechanical aesthetics and the Silk Road.

Icy lanes on Titan

Multivariate analysis of infrared hyperspectral images of the Saturnian satellite Titan reveals widespread ice-rich terrains in the tropics. They are related to a variety of contemporary or past geological processes.

Magnetodisk Coordinates for Saturn

AbstractThe magnetosphere of Saturn is known to be warped into a bowl shape, and the severity of the warping varies with the seasonal tilt of Saturn's spin axis in its orbital plane. This peculiar geometry complicates the analysis of many magnetospheric phenomena, because they are symmetric about the warped magnetodisk equator rather than the spin equator. To reorganize the Cassini data, a new coordinate system is proposed wherein a zA coordinate represents the perpendicular distance above or below the warped surface, and a ρA coordinate represents the arc length along the surface from the origin to where the perpendicular intersects the surface. Using the Cassini spacecraft trajectory, examples show how these disk coordinates (ρA, zA) significantly deviate from the standard spin‐equatorial coordinates (ρ, z), especially outside the orbit of Titan. Another example indicates that fluxes of energetic electrons are well organized in this new system. Supporting information tabulates the disk coordinates as a function of time during the Cassini mission.

Feasibility Assessment of Aerocapture for Future Titan Orbiter Missions

Numerical simulation is used to perform parametric analysis to assess the feasibility of aerocapture at Titan over arrival of , vehicle lift-to-drag ratio of 0–1, and vehicle ballistic coefficient of 90 and . Aerodynamic forces, peak heat rate, and total heat load are evaluated. It is shown that aerocapture at Titan requires a lifting vehicle with a minimum lift-to-drag ratio of 0.2 and an arrival of , an equivalent propulsive of about , which is higher than what is realistically possible. Results show that aerocapture requires different interplanetary trajectories from propulsive options, and aerocapture with a vehicle of lift-to-drag ratio of 0.3 enables an arrival of and higher. The peak heat rate is well within the capability of the state-of-the-art technologies of thermal protection system materials. In addition, the vehicle can achieve an inclination change up to 20 deg via an aerocapture maneuver.

Statistical Study of the Energetic Proton Environment at Titan's Orbit From the Cassini Spacecraft

AbstractA statistical study of the energetic proton environment at Titan's orbit as captured by the MIMI/LEMMS and MIMI/CHEMS instruments is performed. The data analyzed cover all the dedicated flybys of Titan by Cassini as well as the orbit crossings that happen far from the moon. The energetic environment is found to be highly variable on timescales comparable to that of the duration of a flyby. Analysis of H+ ion fluxes reveals a weak asymmetry in Saturn local time with the highest fluxes occurring in the premidnight sector of the magnetosphere. A correlation between the energetic ion fluxes and the location of Cassini in the magnetosphere with respect to the center of the current sheet can be observed. Finally, an empirical model of proton spectra for energies above 20 keV is derived based on fits to Kappa distribution functions. This model can be used to better understand the interaction of Titan with the magnetosphere and the energy deposition by energetic particles below the main ionospheric peak.

An Empirical Model of Titan's Magnetic Environment During the Cassini Era: Evidence for Seasonal Variability

AbstractBased on the magnetic field data collected during the Cassini era, we construct an empirical model of the ambient magnetospheric field conditions along the orbit of Saturn's largest moon Titan. Observations from Cassini's close Titan flybys as well as 191 nontargeted crossings of Titan's orbit are taken into account. For each of these events we apply the classification technique of Simon et al. (2010b) to categorize the ambient magnetospheric field as current sheet, lobe‐like, magnetosheath, or an admixture of these regimes. Independent of Saturnian season, Titan's magnetic environment around noon Saturn local time is dominated by the perturbed fields of Saturn's broad magnetodisk current sheet. Only observations from the nightside magnetosphere reveal a slow but steady change of the background field from southern lobe‐type to northern lobe‐type on a timescale of several years. This behavior is consistent with a continuous change in the curvature of the bowl‐shaped magnetodisk current sheet over the course of the Saturnian year. We determine the occurrence rate of each magnetic environment category along Titan's orbit as a function of Saturnian season and local time.

A Single Deformed Bow Shock for Titan‐Saturn System

AbstractDuring periods of high solar wind pressure, Saturn's bow shock is pushed inside Titan's orbit exposing the moon and its ionosphere to the solar wind. The Cassini spacecraft's T96 encounter with Titan occurred during such a period and showed evidence for shocks associated with Saturn and Titan. It also revealed the presence of two foreshocks: one prior to the closest approach (foreshock 1) and one after (foreshock 2). Using electromagnetic hybrid (kinetic ions and fluid electrons) simulations and Cassini observations, we show that the origin of foreshock 1 is tied to the formation of a single deformed bow shock for the Titan‐Saturn system. We also report the observations of a structure in foreshock 1 with properties consistent with those of spontaneous hot flow anomalies formed in the simulations and previously observed at Earth, Venus, and Mars. The results of hybrid simulations also show the generation of oblique fast magnetosonic waves upstream of the outbound Titan bow shock in agreement with the observations of large‐amplitude magnetosonic pulsations in foreshock 2. We also discuss the implications of a single deformed bow shock for new particle acceleration mechanisms and also Saturn's magnetopause and magnetosphere.

Titan's ionosphere: A survey of solar EUV influences.

Effects of solar EUV on positive ions and heavy negative charge carriers (molecular ions, aerosol, and/or dust) in Titan's ionosphere are studied over the course of almost 12 years, including 78 flybys below 1400 km altitude between TA (October 2004) and T120 (June 2016). The Radio and Plasma Wave Science/Langmuir Probe-measured ion charge densities (normalized by the solar zenith angle) show statistically significant variations with respect to the solar EUV flux. Dayside charge densities increase by a factor of ≈2 from solar minimum to maximum, while nightside charge densities are found to anticorrelate with the EUV flux and decrease by a factor of ≈3-4. The overall EUV dependence of the ion charge densities suggest inapplicability of the idealized Chapman theory below 1200 km in Titan's ionosphere. Nightside charge densities are also found to vary along Titan's orbit, with higher values in the sunward magnetosphere of Saturn compared to the magnetotail.

SUPRATHERMAL ELECTRONS IN TITAN’S SUNLIT IONOSPHERE: MODEL–OBSERVATION COMPARISONS

ABSTRACT The dayside ionosphere of the Saturnian satellite Titan is generated mainly from photoionization of N2 and CH4. We compare model-derived suprathermal electron intensities with spectra measured by the Cassini Plasma Spectrometer/Electron Spectrometer (CAPS/ELS) in Titan's sunlit ionosphere (altitudes of 970–1250 km) focusing on the T40, T41, T42, and T48 Titan flybys by the Cassini spacecraft. The model accounts only for photoelectrons and associated secondary electrons, with a main input being the impinging solar EUV spectra as measured by the Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment and extrapolated to Saturn. Associated electron-impact electron production rates have been derived from ambient number densities of N2 and CH4 (measured by the Ion Neutral Mass Spectrometer/Closed Source Neutral mode) and related energy-dependent electron-impact ionization cross sections. When integrating up to electron energies of 60 eV, covering the bulk of the photoelectrons, the model-based values exceed the observationally based values typically by factors of ∼3 ± 1. This finding is possibly related to current difficulties in accurately reproducing the observed electron number densities in Titan's dayside ionosphere. We compare the utilized dayside CAPS/ELS spectra with ones measured in Titan's nightside ionosphere during the T55–T59 flybys. The investigated nightside locations were associated with higher fluxes of high-energy (>100 eV) electrons than the dayside locations. As expected, for similar neutral number densities, electrons with energies <60 eV give a higher relative contribution to the total electron-impact ionization rates on the dayside (due to the contribution from photoelectrons) than on the nightside.

ION IRRADIATION OF ETHANE AND WATER MIXTURE ICE AT 15 K: IMPLICATIONS FOR THE SOLAR SYSTEM AND THE ISM

ABSTRACT Solid water has been observed on the surface of many different astronomical objects and is the dominant ice present in the universe, from the solar system (detected on the surface of some asteroids, planets and their satellites, trans-Neptunian objects [TNOs], comets, etc.) to dense cold interstellar clouds (where interstellar dust grains are covered with water-rich ices). Ethane has been detected across the solar system, from the atmosphere of the giant planets and the surface of Saturn’s satellite Titan to various comets and TNOs. To date, there were no experiments focused on icy mixtures of C2H6 and H2O exposed to ion irradiation simulating cosmic rays, a case study for many astronomical environments in which C2H6 has been detected. In this work, the radiolysis of a C2H6:H2O (2:3) ice mixture bombarded by a 40 MeV58Ni11+ ion beam is studied. The chemical evolution of the molecular species existing in the sample is monitored by a Fourier transform infrared spectrometer. The analysis of ethane, water, and molecular products in solid phase was performed. Induced chemical reactions in C2H6:H2O ice produce 13 daughter molecular species. Their formation and dissociation cross sections are determined. Furthermore, atomic carbon, oxygen, and hydrogen budgets are determined and used to verify the stoichiometry of the most abundantly formed molecular species. The results are discussed in the view of solar system and interstellar medium chemistry. The study presented here should be regarded as a first step in laboratory works dedicated to simulate the effect of cosmic radiation on multicomponent mixtures involving C2H6 and H2O.

Complex organics in space from Solar System to distant galaxies

Recent observational and experimental evidence for the presence of complex organics in space is reviewed. Remote astronomical observations have detected $$\sim $$ 200 gas-phased molecules through their rotational and vibrational transitions. Many classes of organic molecules are represented in this list, including some precursors to biological molecules. A number of unidentified spectral phenomena observed in the interstellar medium are likely to have originated from complex organics. The observations of these features in distant galaxies suggests that organic synthesis had already taken place during the early epochs of the Universe. In the Solar System, almost all biologically relevant molecules can be found in the soluble component of carbonaceous meteorites. Complex organics of mixed aromatic and aliphatic structures are present in the insoluble component of meteorites. Hydrocarbons cover much of the surface of the planetary satellite Titan and complex organics are found in comets and interplanetary dust particles. The possibility that the early Solar System, or even the early Earth, have been enriched by interstellar organics is discussed.

Genesis of volatile components at Saturn’s regular satellites. Origin of Titan’s atmosphere

Jupiter’s and Saturn’s regular satellites, which posses much ice, are currently thought to have been formed during the early evolution of the Solar System in circumplanetary protosatellite disks. Two of Saturn’s regular satellites—Titan and Enceladus—were experimentally proved to contain, along with water, other volatile components: molecular nitrogen, and methane (which are the major components of Titan’s atmosphere) and various nitrogen and carbon compounds in water plumes of Enceladus. The protomaterial of these rocky–icy satellites was formed in the outer regions of the gas–dust circumsolar nebula, and its closest analogue currently accessible to study is cometary material. The paper presents a review of experimental data on the chemical and isotopic composition of cometary material as possible sources of volatile components on Titan and Enceladus and model evaluations of temperatures in the circumsolar gas–dust protoplanetary disk and Jupiter’s and Saturn’s protosatellite disks during various evolutionary episodes of the solar system. The P–T parameters of the origin of the protomaterial of Jupiter’s and Saturn’s regular satellites were proved to have been remarkably different, and hence, the material of Europa, a Jupiter’s regular satellite, cannot contain any volatile components other than water, in contrast to Titan and Enceladus. This conclusion is supported by experimental data. Cometary material is likely genetically related to the material of Saturn’s regular satellites Titan and Enceladus. The paper presents results of thermodynamic simulation of the evolution of the chemical and phase composition of Saturn’s satellites and suggests a model for the origin of Titan’s nitrogen–methane atmosphere.