Radio-Television-Film / This report is the narrative chronology of my nine-year process of writing my first ever feature film script, Saturn Returns, which I’ve submitted in final draft form as my thesis work for this degree. / text

The stratosphere of Saturn contains a photochemical haze that appears thicker at the poles and may originate from chemistry driven by the aurora. Models suggest that the formation of hydrocarbon haze is initiated at high altitudes by the production of benzene, which is followed by the formation of heavier ring polycyclic aromatic hydrocarbons. Until now there have been no observations of hydrocarbons or photochemical haze in the production region to constrain these models. We report the first vertical profiles of benzene and constraints on haze opacity in the upper atmosphere of Saturn retrieved from Cassini Ultraviolet Imaging Spectrograph stellar occultations. We detect benzene at several different latitudes and find that the observed abundances of benzene can be produced by solar-driven ion chemistry that is enhanced at high latitudes in the northern hemisphere during spring. We also detect evidence for condensation and haze at high southern latitudes in the polar night.

The exploration of Saturn's giant satellite Titan is considered, with particular reference to its surface which is hidden beneath a thick atmosphere. Groundbased observations, in which great progress has been made recently, and the measurements made by the Pioneer and Voyager spacecraft, are reviewed. Concepts for spacecraft to perform in-situ measurements on Titan are reviewed, as is the development of the NASA/ESA Cassini mission, how the mission constrains scientific investigations, and in tum how the mission has been constrained by funding pressures. The capabilities of the Cassini payload for investigating Titan's surface are critically assessed, and the ability of the Surface Science Package (SSP) on the Huygens probe to determine the composition of surface liquids is examined. Some thoughts on payload selection and the value of individual measurements are presented. The development of an impact penetrometer, and the interpretation of penetrometer and accelerometer data to measure surface mechanical properties, is described. It should be noted that Huygens is not a vehicle expressly designed as a lander, so the impact dynamics are complex. Additionally, the examination of the prospects offered by acoustic instrumentation are investigated. Modelling of a number of Titan surface processes is presented, including rainfall, photochemical and meteoric deposition, tidal dissipation in the interior, regolith processes such as volatile heat transport, annealing and aeolian transportation and the effects of tidal and crustal processes on lakes. A key subtopic of the thesis addresses the theme of planetary exploration as a whole, with the interaction between and the limitations of the exploration 'triad' of observations, insitu measurements and theory. Note is made of the remarkably significant role played by individuals and their perceptions.

Thesis--University of Chicago. / Typescript (carbon copy). Includes bibliographical references. Also issued in print.

Thesis--University of Chicago. / Typescript (carbon copy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--University of Oulu, 1985. / Includes bibliographical references (p. [34]-36).

Numerous wave and gap features observed in Voyager data of Saturn's rings are produced by resonances between the orbital frequencies of known external satellites and ring particle orbits. This thesis investigates the possibility that other, currently unassociated, ring features are generated by perturbations on ring participle orbits produced by non-axisymmetric gravitational fields resulting from acoustic oscillation modes of the planet. The frequencies of Saturnian low degree (l ≤ 8) fundamental (or f) mode oscillations are calculated for a variety of Saturn interior models which span the range of uncertainty of the interior structure of the planet. Corrections for rotation, oblateness, and possible differential rotation have been applied. Only the low degree f-modes are found to have frequencies and likely wave amplitudes in the range necessary to produce gap or wave features in the rings. The calculated positions of outer Lindblad resonances (OLR) for the degree l = 2,3,4, and 5 sectoral f-modes of a single Saturn model lie near four previously unassociated C-ring features. These features are the Maxwell gap and three waves identified as being forced at either OLR or inner vertical resonances. The outer vertical resonance (OVR) of the l = 5, m = 4 mode also overlaps the location of a wave which may be forced at either an OVR or an inner Lindblad resonance. Four other similar wave features, however, cannot be explained by oscillation mode resonances. This failure to account for all of the comparable unassociated C-ring waves is the principal inadequacy of the hypothesis. Other observed properties of the wave features, however, including their azimuthal wavenumbers m and the variation of amplitude with proposed oscillation mode degree are consistent with the proposed forcing. Planetary oscillation amplitudes of ∼1 m are required for gap opening; wave amplitudes of ∼10 cm are required for density wave production. The C-ring thus serves as a very sensitive f-mode detector. Observations by the Cassini spacecraft should unequivocally determine if the C-ring features are produced by planetary oscillation modes. If these observations confirm the association, significant new constraints could be placed on Saturnian energy transport, differential rotation, and core size.

A numerical model has been developed for atomic hydrogen densities in the Titan hydrogen torus. The effects of occasional collisions were included in order to accurately simulate physical conditions inferred from the Voyager 1 and 2 Ultraviolet Spectrometer (UVS) results of Broadfoot et al. (1981) and Sandel et al. (1982). The model employed Lagrangian perturbation of orbital elements of hydrogen atoms launched from Titan and Monte-Carlo simulation of collisions and loss mechanisms. The torus is found to be azimuthally symmetric with the density sharply peaked at Titan's orbit, and decreasing rapidly in the outward and perpendicular directions and more gradually inward from 17 to 5 R(s). The energetic hydrogen atoms from Saturn's upper atmosphere, first predicted by Shemansky and Smith (1982), were also investigated. Collisions of these Saturnian atoms with the torus population do not contribute to the torus density, and will lead to a net loss of torus atoms if their launch speeds from Saturn extend above 40 km/sec. The Saturnian atoms produce a corona which was modelled using the theory of Chamberlain (1963). Based on the energetic hydrogen production rate given by Shemansky and Smith (1986), the coronal density at Saturn's exobase is taken to be 200 to 300 cm⁻³, decreasing to 3 or 4 cm⁻³ at 20 R(s). Without the coronal population, the torus model does not reproduce the Voyager 2 UVS Lyman α intensities because the hydrogen atoms are too closely confined toward Titan's orbital plane. The observations can be reproduced by a model that includes the corona and has central plane maxima of 62 cm⁻³ at Titan's orbit and 318 cm⁻³ at Saturn's exobase. The effect of Titan's exospheric temperature (T(E)) on torus structure is seen in the column abundances perpendicular to the central plane at radii of 5 to 15 R(s). Spacecraft observations of these column abundances should allow verification of T(E) to within about 100°K. Similar observations of other species expected to be present in the torus, such as H₂, N, and N₂, would indicate their approximate launch speeds from Titan and thus the relative importance of thermal and non-thermal loss mechanisms.

No description available.

This licentiate thesis presents our investigation of Saturn's inner plasma disk. The thesis gives an overview of the Cassini-Huygens project, what a plasma is and how we use the Langmuir probe to investigate it, various difficulties related to the measurements, the structure of the magnetosphere of Saturn, with special focus on the inner magnetosphere and the region around the Saturnian moon Enceladus. For our investigation we use the Cassini Langmuir probe to derive ion density and ion velocity in the region from 2.5 to 12 Saturn radii. We show that the dominant part of the plasma torus, ion density above ~15 particle/cm3, is located in between 2.5 and 8 Saturn radii (1 RS = 60,268 km) from the planet, with a north-southward extension of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cpm" />2 RS. The plume of the moon Enceladus is clearly visible as an ion density maximum of 105 cm-3, only present at the south side of the ring plane, as expected since the Enceladus plumes are located in the south polar region. Also the azimuthal ion velocity vi,Θ is estimated, showing a clear general trend in the region between 3 and 7 RS, described by vi,Θ =1.5R2-8.7R+39. The average vi,Θ starts to deviate from corotation speed at around 3 RS and reaches down to ~68 % of corotation close to 5 RS. The Langmuir probe data show a clear day/night side asymmetry in both ion density and ion velocity, most prominent in the radial region 4-6 RS from the center of Saturn. The ion densities ni varies from an average of ~35 cm-3 for the lowest dayside values close to noon up to ~70 cm-3 for the highest nightside values around midnight. The azimuthal ion velocities vi,Θ varies from ~28-32 km/s at the lowest dayside values around noon to ~36-40 km/s at the highest nightside values around midnight. This gives an azimuthal ion velocity difference between noon and midnight of Δvi,Θ ~5-10 km/s. The day/night asymmetry is suggested to be due to dust-plasma interaction.