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Tides raised in Titan by Saturn give rise to a static and a periodic deformation; both will be measured with Doppler tracking during the CASSINI Tour of the Saturnian System. The latter deformation is due to the significant eccentricity of Titan's orbit and has a frequency equal to the orbital angular velocity of Titan.
Saturn's largest moon, Titan, boasts organic chemistry that may hold clues to how life formed on the primitive Earth. The Cassini Mission, to be launched in October 1997, will explore Saturn and its moons, especially Titan. Mapping the surface of Titan will be accomplished with a radar instrument that acts as a 14 GHz synthetic aperture radar, microwave radiometer, altimeter, and scatterometer.
This paper describes experimental results from a development program focused in maturing Titan aerobot technology in the areas of mechanical and thermal subsystems. Results from four key activities are described: first, a cryogenic balloon materials development program involving coupon and cylinder tests and culminating in the fabrication and testing of an inflated 4.6 m long prototype blimp at 93 K; second, a combined lab experiment and numerical simulation effort to assess potential problems resulting from radioisotope thermal generator waste heat generation near an inflated blimp; third, an aerial deployment and inflation development program consisting of laboratory and helicopter drop tests on a near full scale (11 m long) prototype blimp; and fourth, a proof of concept experiment demonstrating the viability of using a mechanically steerable high gain antenna on a floating blimp to perform direct to Earth telecommunications from Titan. The paper provides details on all of these successful activities and discusses their impact on the overall effort to produce mature systems technology for future Titan aerobot missions.
This viewgraph presentation reviews study into exploration of Titan. Including a possible Titan Rover that would use the advanced radioisotope power system (RPS). The goal of the study is to demonstrate a simple, credible and affordable rover mission concept for Titan in-situ exploration, enabled by an Advanced RPS. The presentation reviews the possible launch vehicle, and trajectory options; desired instrumentation that would be aboard the rover; and considerations for the design of the rover.
The wide spectral coverage and extensive spatial, temporal, and phase-angle mapping capabilities of the Visual Infrared Mapping Spectrometer (VIMS) onboard the Cassini-Huygens Orbiter are producing fundamental new insights into the nature of the atmospheres of Saturn and Titan. For both bodies, VIMS maps over time and solar phase angles provide information for a multitude of atmospheric constituents and aerosol layers, providing new insights into atmospheric structure and dynamical and chemical processes. For Saturn, salient early results include evidence for phosphine depletion in relatively dark and less cloudy belts at temperate and mid-latitudes compared to the relatively bright and cloudier Equatorial Region, consistent with traditional theories of belts being regions of relative downwelling. Additional Saturn results include (1) the mapping of enhanced trace gas absorptions at the south pole, and (2) the first high phase-angle, high-spatial-resolution imagery of CH4 fluorescence. An additional fundamental new result is the first nighttime near-infrared mapping of Saturn, clearly showing discrete meteorological features relatively deep in the atmosphere beneath the planet's sunlit haze and cloud layers, thus revealing a new dynamical regime at depth where vertical dynamics is relatively more important than zonal dynamics in determining cloud morphology. Zonal wind measurements at deeper levels than previously available are achieved by tracking these features over multiple days, thereby providing measurements of zonal wind shears within Saturn's troposphere when compared to cloudtop movements measured in reflected sunlight. For Titan, initial results include (1) the first detection and mapping of thermal emission spectra of CO, CO2, and CH3D on Titan's nightside limb, (2) the mapping of CH4 fluorescence over the dayside bright limb, extending to approximately 750 km altitude, (3) wind measurements of approximately 0.5 ms(exp -1), favoring prograde, from the movement of a persistent (multiple months) south polar cloud near 88 deg S latitude, and (4) the imaging of two transient mid-southern-latitude cloud features.
The Huygens probe arrived at Saturn's moon Titan on January 14, 2005, unveiling a world that is radically different from any other in the Solar system. The data obtained, complemented by continuing observations from the Cassini spacecraft, show methane lakes, river channels and drainage basins, sand dunes, cryovolcanos and sierras. This has lead to an enormous scientific interest in a follow-up mission to Titan, using a robotic lighter-than-air vehicle (or aerobot). Aerobots have modest power requirements, can fly missions with extended durations, and have very long distance traverse capabilities. They can execute regional surveys, transport and deploy scientific instruments and in-situ laboratory facilities over vast distances, and also provide surface sampling at strategic science sites. This paper describes our progress in the development of the autonomy technologies that will be required for exploration of Titan. We provide an overview of the autonomy architecture and some of its key components. We also show results obtained from autonomous flight tests conducted in the Mojave desert.
We report a wide-ranging study of Titan's surface temperatures by analysis of the Moon's outgoing radiance through a spectral window in the thermal infrared at 19 mm (530/cm) characterized by lower atmospheric opacity. We begin by modeling Cassini Composite Infrared Spectrometer (CIRS) far infrared spectra collected in the period 2004-2010, using a radiative transfer forward model combined with a non-linear optimal estimation inversion method. At low-latitudes, we agree with the HASI near-surface temperature of about 94 K at 101S (Fulchignoni et al., 2005). We find a systematic decrease from the equator toward the poles, hemispherically asymmetric, of approx. 1 K at 60 deg. south and approx. 3 K at 60 deg. north, in general agreement with a previous analysis of CIRS data and with Voyager results from the previous northern winter. Subdividing the available database, corresponding to about one Titan season, into 3 consecutive periods, small seasonal changes of up to 2 K at 60 deg N became noticeable in the results. In addition, clear evidence of diurnal variations of the surface temperatures near the equator are observed for the first time: we find a trend of slowly increasing temperature from the morning to the early afternoon and a faster decrease during the night. The diurnal change is approx. 1.5 K, in agreement with model predictions for a surface with a thermal inertia between 300 and 600 J/ sq. m s (exp -1/2) / K. These results provide important constraints on coupled surface-atmosphere models of Titan's meteorology and atmospheric dynamic.
Titan's landscape is profoundly shaped by its atmosphere and comparable in magnitude perhaps with only the Earth and Mars amongst the worlds of the Solar System. Like the Earth, climate dictates the intensity and relative roles of fluvial and aeolian activity from place to place and over geologic time. Thus Titan's landscape is the record of climate change. We have investigated three broad classes of Titan climate evolution hypotheses (Steady State, Progressive, and Cyclic), regulated by the role, sources, and availability of methane. We favor the Progressive hypotheses, which we will outline here, then discuss their implication for habitability.
We will discuss photochemical properties of Titan's organic molecules in the condensed phase as solid aerosols or surface material, from small linear polyyenes (polyacetylenes and polycyanoacetylenes) such as C2H2, C4N2, HC5N, etc. In particular we will focus on photochemistry caused by longer wavelength UV-VIS photons (greater than 250 nm) photons that make it through Titan's atmosphere to the haze region (approximately 100 km) and on to the surface of Titan.
Dune fields are one of the dominant landforms and represent the largest known organic reservoir on Titan. SAR-derived topography show that Titan's dune terrains tend to occupy the lowest altitude areas in equatorial regions occurring at mean elevations between approx.-400 and ~0 m. In elevated dune terrains, there is a definite trend towards a smaller dune to interdune ratio, interpreted as due to limited sediment availability. A similar linear correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. These findings place important constraints on Titan's geology and climate.
Titan is a high priority for exploration, as recommended by NASA's 2006 Solar System Exploration (SSE) Roadmap. NASA's 2003 National Research Council (NRC) Decadal Survey and ESA's Cosmic Vision Program Themes. Recent revolutionary Cassini-Huygens discoveries have dramatically escalated interest in Titan as the next scientific target in the outer solar system. This study demonstrates that an exciting Titan Saturn System Mission (TSSM) that explores two worlds of intense astrobiological interest can be initiated now as a single NASA/ESA collaboration.
Several recent studies have proposed certain terrain types (i.e., physiographic units) on Titan thought to be formed by fluvial processes acting on local uplands of bedrock or in some cases sediment. We have earlier used our landform evolution models to make general comparisons between Titan and other ice world landscapes (principally those of the Galilean satellites) that we have modeled the action of fluvial processes. Here we give examples of specific landscapes that, subsequent to modeled fluvial work acting on the surfaces, produce landscapes which resemble mapped terrain types on Titan.
Prompted by the detection of stratospheric cloud layers by Cassini's Composite Infrared Spectrometer (CIRS; see Anderson, C.M., Samuelson, R.E. [2011]. Icarus 212, 762-778), we have re-examined the observations made by the Descent Imager/Spectral Radiometer (DISR) in the atmosphere of Titan together with two constraints from measurements made outside the atmosphere. No evidence of thin layers (<1 km) in the DISR image data sets is seen beyond the three previously reported layers at 21 km, 11 km, and 7 km by Karkoschka and Tomasko (Karkoschka, E., Tomasko, M.G. [2009]. Icarus 199, 442-448). On the other hand, there is evidence of a thicker layer centered at about 55 km. A rise in radiance gradients in the Downward-Looking Visible Spectrometer (DLVS) data below 55 km indicates an increase in the volume extinction coefficient near this altitude. To fit the geometric albedo measured from outside the atmosphere the decrease in the single scattering albedo of Titan's aerosols at high altitudes, noted in earlier studies of DISR data, must continue to much higher altitudes. The altitude of Titan's limb as a function of wavelength requires that the scale height of the aerosols decrease with altitude from the 65 km value seen in the DISR observations below 140 km to the 45 km value at higher altitudes. We compared the variation of radiance with nadir angle observed in the DISR images to improve our aerosol model. Our new aerosol model fits the altitude and wavelength variations of the observations at small and intermediate nadir angles but not for large nadir angles, indicating an effect that is not reproduced by our radiative transfer model. The volume extinction profiles are modeled by continuous functions except near the enhancement level near 55 km altitude. The wavelength dependence of the extinction optical depth is similar to earlier results at wavelengths from 500 to 700 nm, but is smaller at shorter wavelengths and larger toward longer wavelengths. A Hapke-like model is used for the ground reflectivity, and the variation of the Hapke single scattering albedo with wavelength is given. Fits to the visible spectrometers looking upward and downward are achieved except in the methane bands longward of 720 nm. This is possibly due to uncertainties in extrapolation of laboratory measurements from 1 km-am paths to much longer paths at lower pressures. It could also be due to changes in the single scattering phase functions at low altitudes, which strongly affect the path length through methane that the photons travel. We demonstrate the effects on the model fits by varying each model parameter individually in order to illustrate the sensitivity of our determination of each model parameter.
We present results on the formation of Titan aerosol analogs produced via far-UV irradiation of five aromatic precursors: benzene, naphthalene, pyridine, quinoline and isoquinoline. This is the first reported evidence of far-IR emission features observed below 200 per cm in laboratory-created Titan aerosols. These laboratory studies were motivated by recent analyses of Cassini Composite Infrared Spectrometer (CIRS) spectra that show a broad aerosol emission feature in the far-IR spectral region centered near 140 per cm, which is unique to Titan's photochemically-produced aerosol. We find that all three of the aerosol analogs formed from nitrogen-containing aromatics have similar broad emission features near that of the observed CIRS far-IR aerosol spectral feature. In addition, the inclusion of 1.5% methane to that of trace amounts of benzene also gives rise to an aerosol with a weak far-IR emission feature located below 200 per cm.
Titan's stratospheric ice clouds are by far the most complex of any observed in the solar system, with over a dozen organic vapors condensing out to form a suite of pure and co-condensed ices, typically observed at high winter polar latitudes. Once these stratospheric ices are formed, they will diffuse throughout Titan's lower atmosphere and most will eventually precipitate to the surface, where they are expected to contribute to Titan's regolith.
During the past twenty years, NASA effectively erased earlier Mars mishaps with six successful missions to the Red Planet. These missions delivered one orbiter and five payloads to the surface. Those payloads included three rovers, Spirit (2004) which roamed 11 years, Opportunity (2004) which roamed nearly 15 years, and Curiosity (2012) which is in its ninth year, along with two landers, Phoenix (2008) and InSIGHT (2018). In July, the Mars 2020 mission will send another large rover, Perseverance, which will land in 2021. The InSIGHT mission even demonstrated the capability to send CubeSats along to help with communication back to the surface. NASA has demonstrated the capability to land a metric ton of vehicles plus science instruments on Mars and expects that the same technologies will be equally successful landing Dragonfly on Titan in the 2030’s. The thermal protection systems (TPS) used on the Mars missions are sufficiently developed and matured to continue furthering science on both Mars and Titan, assuming that the TPS materials are sustained by industry. The purpose of this white paper is to encourage further exploration and science on both Mars and Titan because we have the technologies to support them. In addition, we will look forward to human exploration of Mars and identify the improvements in TPS materials required to facilitate landing the larger payloads.
Titan is an extraordinary moon belonging to Saturn. It presents a dense atmosphere with a surface pressure approximately 1.45 times that of Earth’s. The relative abundance of noble gases and their isotopes can elucidate extant geochemical processes and inform past and future planetary evolution. The GCMS on the Hyugens probe sampled the dense atmosphere of Saturn’s Titan in 2005 and did not detect Kr or Xe at ppb concentrations. Several chemical pathways have been considered as mechanisms to account for the depletion of these heavy nobles. However, our understanding remains incomplete without in situ detection. Thus, we investigate spaceflight cryogenic enrichment for Kr and Xe. The thermodynamic processes would be capable of substantially amplifying these gases at femtomole concentrations, in anticipation of future atmospheric surveys on Titan.
The Tension Adjustable Network for Deploying Entry Membrane (TANDEM) concept is a phase II NASA Innovative Advanced Concepts (NIAC) project. One of the goals for this project was to extend the application of tensegrity-based rovers to a rideshare concept for a Titan mission. This report provides preliminary details of the TANDEM concept for Titan. System analyses of the entry vehicle were performed and compared to data from the Huygens mission to Titan. The entry aeroshell was based on Huygens and Stardust aeroshells. Modeling, simulation and design of the tensegrity deployment were performed using a nonlinear optimization form-finding algorithm. Lastly, a neuroevolution-based machine learning control strategy was applied, which produced efficient rolling locomotion gaits.