Cassini Titan Science

The three mosaics above were composed with data from Cassini's Visual and Infrared Mapping Spectrometer (VIMS) taken during the last three Titan flybys.

On this page:


Publications, data, and analysis software for each Titan science theme:


Overview

The Titan Sections in Cassini Final Mission Report (in preparation) summarizes the status of Titan science, in 2018, as a result of Cassini exploration of the Saturn system. It also includes open questions that will be explored by future scientists.

Charm Talks is a series of talks given by the team that provides insight into discovery and development of understanding

Mission Objectives

  • Determine abundances of atmospheric constituents (including any noble gases); establish isotope ratios for abundant elements; constrain scenarios of formation and evolution of Titan and its atmosphere.
  • Observe vertical and horizontal distributions of trace gases; search for more complex organic molecules; investigate energy sources for atmospheric chemistry; model the photochemistry of the stratosphere; study formation and composition of aerosols.
  • Measure winds and global temperatures; investigate cloud physics and general circulation and seasonal effects in Titan's atmosphere; search for lightning discharges.
  • Determine physical state, topography and composition of surface; infer internal structure.
  • Investigate upper atmosphere, its ionization and its role as a source of neutral and ionized material for the magnetosphere of Saturn.
  • Determine seasonal changes in the methane-hydrocarbon hydrological cycle: of lakes, clouds, aerosols, and their seasonal transport.
  • Determine seasonal changes in the high-latitude atmosphere, specifically the temperature structure and formation and breakup of the winter polar vortex.
  • Observe Titan's plasma interaction as it goes from south to north of Saturn's solar-wind-warped magnetodisk from one solstice to the next.
  • Determine the types, composition, distribution, and ages, of surface units and materials, most notably lakes (i.e. filled vs. dry & depth; liquid vs. solid & composition; polar vs. other latitudes & lake basin origin).
  • Determine internal and crustal structure: Liquid mantle, crustal mass distribution, rotational state of the surface with time, intrinsic and/or internal induced magnetic field.
  • Measure aerosol and heavy molecule layers and properties.
  • Resolve current inconsistencies in atmospheric density measurements (critical to a future Flagship mission).
  • Determine icy shell topography and viscosity.
  • Determine the surface temperature distribution, cloud distribution, and tropospheric winds.

A list of publications related to Titan can be found on the Cassini Titan Reference Page.


Titan Data

The science topics above include links to data sets related to each topic. This section includes a comprehensive list of all of the search tools and data archives related to Titan studies.

Data Search Tools

Searching by parameters:

  • OPUS is a search tool for CIRS, ISS, UVIS and VIMS data with a wide variety of search parameters including the target body, distance, and illumination conditions.
  • PDS Imaging Atlas is a search tool for ISS and RADAR data with a wide variety of search parameters including the target body, distance, and illumination conditions.

Searching by surface map:

  • Titan Trek is a Geographical Information System (GIS) tool to find, visualize and download data in the context of a map of Titan.
  • PILOT is a Geographical Information System (GIS) tool to find and download data in the context of a map of Titan (data through 2010).

Searching by mission events:

  • The Event Calendar helps search for Titan observations
  • The Tour Atlas (Readme File) provides various geometric parameters (range, latitude, longitude, etc.) referenced to Saturn, Titan and the icy satellites in 5-minute and 1-hour time steps for the entire mission

Documentation and Orientation

Instruments Used to Study Titan with Links to Data

Table with instruments, PDS archive links, OPUS/Atlas search links, and links to the instrument pages goes here. also annotate with examples of what an instrument can study on Titan, if there is space.

Titan Interior

Cassini measured Titan's gravity field and dynamic tidal response, indicating (together with Huygens electric field data) the presence of a deep subsurface water ocean—one denser than liquid water and thus possibly salty. A relatively low density, possibly hydrated, core was detected.
    Cassini measured the shape of Titan's gravity field, including the tidal response and firmly established no intrinsic magnetic field.

Key Publications

    In Titan from Cassini-Huygens (Brown, R. H., J-P. Lebreton, and J. H. Waite, Jr., Eds). Springer, 535 pp., 2009 (DOI: 10.1007/978-1-4020-9215-2)
  • The Origin and Evolution of Titan. J Lunine, M Choukroun, D Stevenson, G Tobie
    In Titan: Interior, Surface, Atmosphere, and Space Environment (Ingo Müller-Wodarg , Caitlin A. Griffith , Emmanuel Lellouch, Thomas E. Cravens, Eds). Cambridge University Press (2014) (DOI: 10.1017/CBO9780511667398)
  • The Origin and Evolution of Titan. Tobie, G., J.I. Lunine, J. Monteux, O. Mousis And F. Nimmo

Individual publications:

Titan Interior Data

From RADAR:
  • Titan Global Shape Model contains a variety of different models for the global shape of Titan obtained by interpolation or by least-squares fitting to RADAR altimetry and SARTopo data.

Titan Surface

By the conclusion of the mission Cassini-Huygens had revealed a complex Titan surface with a striking resemblance to the total geomorphology of the Earth. Dunes, rivers, gullies, lakes, seas, volcanic constructs, mountains, are all present. Titan’s methane cycle, analogous to the Earth’s hydrologic cycle, drives processes including sedimentary transport that lead to the most geologically diverse surface after that of the Earth. Most spectacular was the discovery of several polar seas and hundreds of lakes, covering multiple hundreds of thousands of square kilometers. Some of the coastlines appear very Earth-like, with bays, cliffs, coves and river estuaries, while other boundaries are puzzling and may reflect a tectonic origin of the sea basins. Bathymetry and compositional measurements by Cassini lead to a liquid hydrocarbon inventory of about 70,000 square kilometers, mostly methane.
Cassini-Huygens observed dynamic meteorology in cloud behavior and rainstorms, changes in the lakes and seas, and evaporation of liquids from the surface. Cassini and the close-up images provided by Huygens establish fluvial erosion and rainfall as important processes tying together Titan's surface and atmosphere. A variety of cloud and weather patterns, including those generating rain, occur in the lower atmosphere, and comparison of cloud patterns with general circulation models supports the presence of a substantial amount of liquid methane in Titan’s crust.
An average surface age of ~ 0.5–1 billion years is derived from a variety of Cassini-Huygens data.

Key Publications

    In Titan from Cassini-Huygens (Brown, R. H., J-P. Lebreton, and J. H. Waite, Jr., Eds). Springer, 535 pp., 2009 (DOI: 10.1007/978-1-4020-9215-2)
  • Geology and Surface Processes on Titan. R Jaumann, R. L. Kirk, R. D. Lorenz, R. M.C. Lopes, E Stofan, E. P. Turtle et al.
  • Composition of Titan's Surface. L. A. Soderblom, J. W. Barnes, R. H. Brown, R. N. Clark, M. A. Janssen, T. B. McCord et al.
    In Titan: Interior, Surface, Atmosphere, and Space Environment (Ingo Müller-Wodarg , Caitlin A. Griffith , Emmanuel Lellouch, Thomas E. Cravens, Eds). Cambridge University Press (2014) (DOI: 10.1017/CBO9780511667398)
  • Titan's Surface Geology. By O. Aharonson, A. G. Hayes, P. O. Hayne, R. M. Lopes, A. Lucas, J. T. Perron

Individual publications:

  • Hayes et al., A post-Cassini view of Titan's methane-based hydrologic cycle, Nature Geosciencevolume 11, pages306–313 (2018) (DOI: 10.1038/s41561-018-0103-y)

Titan Surface Data

Search tools

  • Titan Trek allows geospatial search for RADAR, VIMS, and ISS data, as well as downloadable map mosaics.
  • PILOT to find ISS and VIMS data in the context of Titan's surface map (data through 2010).
  • PDS Imaging Atlas to find ISS, VIMS and RADAR data, based on search parameters.
  • OPUS is another parameter-based search tool to find CIRS, UVIS, ISS and VIMS data on Titan.
  • Cassini VIMS Data Portal at the Université de Nantes, organized by flyby.

Derived data products

From RADAR:
  • Geologic Maps are available at Icarus (a.k.a Geomorphologic Maps) of Titan are derived from SAR and HiSAR swath mosaics, and where these are not available, from global radiometry and ISS global mosaics. The maps show the major geomorphologic classes of Titan (Craters, Mountains, Labyrinths, Plains, Dunes, and Lakes) as described in Malaska et al., (2016) (DOI: 10.1016/j.icarus.2016.02.021). These maps are available as registered GeoTIFFs ready for installation in GIS programs.
  • Radiometer Maps include data from pole-to-pole scans and are tabulated in time ordered tables of point-by-point of brightness temperature and other parameters. Residual maps interpolated on a regular grid in cylindrical coordinate are also included.
  • RADAR - SAR Images from each flyby are derived from Cassini RADAR Basic Image Data Records at 256 pixels/degree. These versions have had systematic biases due to thermal and quantization noise, and systematic variation due to incidence angle have been removed. For more information on this process, see the User's Guide.
From RSS (Radio Science Subsystem):

Other Derived data products


Huygens Lander on Titan

"On 14 January 2005, at 13:34 CET (12:34 UTC), ESA's Huygens probe entered the history books by descending to the surface of Titan, Saturn's largest moon. This was humanity's first successful attempt to land a probe on another world in the outer Solar System.
Huygens hitched a ride to the Saturn system during an epic, seven-year voyage attached to NASA's Cassini spacecraft. The final chapter of the interplanetary trek was a 21-day solo cruise toward the haze-shrouded moon. Plunging into Titan's atmosphere, the probe survived the hazardous 2 hour 27 minute descent to touch down safely on Titan's frozen surface."

Huygens Data and Related Cassini Orbiter Data

Key Publications

  • Lebreton, J. P., A.Coustenis, J. I. Lunine, F. Raulin, T. Owen, D. F. Strobel, Results from the Huygens probe on Titan, Astro & Astrophys. Rev., 17, 149-179, doi 10.1007/s00159-009-0021-5, 2009.
  • Huygens, Science, Payload and Mission, ESA SP-1177, ed. Wilson, A., European Space Agency, Noordwijk, The Netherlands, 1997.

Titan Atmosphere

To understand the structure of Titan's atmosphere one must keep in mind certain basic facts from solar system dynamics. First, the axial tilt of Saturn and Titan is 26.73°, second, Saturn's orbital eccentricity is 0.05415, which yield variations in the distance from the Sun from 9.04 to 10.07 AU and in the total solar flux of ~ 20 %. Titan's atmospheric seasonal evolution is driven by three mechanisms: the seasonal change in solar declination, the orbital eccentricity of Saturn with Titan receding from the Sun since 2002, and the solar cycle variation of the Sun with activity increasing from its minimum in late 2009 to peak solar activity for cycle 24 in April 2014. Perihelion last occurred in 25 February 2003. Summer solstice in Titan's southern hemisphere was 17 March 2002; summer solstice in the northern hemisphere was on 24 May 2017 after spring equinox on 11 August 2009. The measurement of isotopic argon in the atmosphere supports significant outgassing over Titan's history, while the low abundance of primordial argon along with other isotopic measurements support ammonia as the original parent molecule of Titan's atmospheric nitrogen.
At the end of the Cassini-Huygens Prime Mission, we had a good first order knowledge of the density and thermal structure of the atmosphere with the exception of the ~ 500-950 km region, variously called the ignorosphere, agnostosphere, etc. Although HASI inferred the thermal structure at equatorial latitudes through this region, it did not yield a pronounced mesopause as was widely expected from theory. CIRS data provided detailed altitudinal and latitudinal composition and temperature measurements of the stratosphere. The latter allowed the derivation of stratospheric zonal winds at substantial super-rotation speeds.
The Cassini Equinox and Solstice Missions enabled the study of seasonal variations of composition, temperatures and inferred zonal winds to understand the transition from summer in the southern hemisphere to equinoctial conditions to summer in the northern hemisphere, especially as the northern polar region emerges out of the polar winter night and its strong circumpolar vortex breaking up. The entire duration of the Cassini Mission exceeded 13 years, permitting observations over close to half of a seasonal cycle (almost half of Saturnian year) on Titan and revealed that seasonal variations are not symmetrical. The eccentricity of Saturn's orbit and the obliquity of its rotational pole is sufficient to produce the observed asymmetry in Titan's seasonal response. But its entire stratosphere is tilted by several degrees from the rotational pole. Seasonal variations in composition, density, and thermal structure of Titan's upper atmosphere were characterized in particular by INMS with complementary data from UVIS measurements. Cassini-Huygens observed dynamic meteorology in cloud behavior and rainstorms, changes in the lakes and seas, and evaporation of liquids from the surface.
Cassini data determined that the thermosphere is highly variable, contradicting model predictions. It is also a chemical factory that initiates the formation of complex positive and negative ions in the high thermosphere as a consequence of magnetospheric-ionospheric-atmospheric interaction involving solar EUV and UV radiation, energetic ions and electrons. This factory produces very heavy positive and negative ions and large molecules, which condense out and are detectable in solar and stellar UV occultations at ~ 1000 km, and initiate the haze formation process. As these particles fall through the 500-950 km region and grow, they become detectable by remote sensing: UVIS at ~ 1000 km, ISS at ~ 500 km and eventually become ubiquitous throughout the stratosphere. These haze particles are strong absorbers of solar UV and visible radiation, play a fundamental role in heating Titan's stratosphere and mesosphere and provide a surface for heterogeneous reactions. The differential heating with latitude drives wind systems in Titan's middle atmosphere, much as ozone does in the Earth's middle atmosphere.
  • Cassini-Huygens discovered a variety of weather patterns, including rainstorms, in Titan's lower atmosphere and documented seasonal changes therein.
  • Cassini further explored the evolution and composition of the winter circumpolar vortex that switches hemispheres seasonally. Titan has strong parallels to the Earth with strong winter polar vortices.
  • Cassini-Huygens discovered Enceladus as one possible source for oxygen compounds in Titan's atmosphere.
  • Cassini-Huygens came up with the surprising result that lightning is absent despite observed methane moist convection.

Key Publications

    In Titan from Cassini-Huygens (Brown, R. H., J-P. Lebreton, and J. H. Waite, Jr., Eds). Springer, 535 pp., 2009 (DOI: 10.1007/978-1-4020-9215-2)
  • Volatile Origin and Cycles: Nitrogen and Methane. R Jaumann, R. L. Kirk, R. D. Lorenz, R. M.C. Lopes, E Stofan, E. P. Turtle et al.
  • High-Altitude Production of Titan's Aerosols. J. H. Waite Jr., D. T. Young, J. H. Westlake, J. I. Lunine, C. P. McKay, W. S. Lewis
  • Atmospheric Structure and Composition. Darrell F. Strobel, Sushil K. Atreya, Bruno Bézard, Francesca Ferri, F. Michael Flasar, Marcello Fulchignoni et al.
  • Composition and Structure of the Ionosphere and Thermosphere. T. E. Cravens, R. V. Yelle, J. -E. Wahlund, D. E. Shemansky, A. F. Nagy
  • Aerosols in Titan's Atmosphere. Martin G. Tomasko, Robert A. West
  • Atmospheric Dynamics and Meteorology. F. M. Flasar, K. H. Baines, M. K. Bird, T. Tokano, R. A. West
  • Seasonal Change on Titan. Ralph D. Lorenz, Michael E. Brown, F. Michael Flasar
  • Mass Loss Processes in Titan's Upper Atmosphere. R. E. Johnson, O. J. Tucker, M. Michael, E. C. Sittler, H. T. Smith, D. T. Young et al.
  • Energy Deposition Processes in Titan's Upper Atmosphere and Its Induced Magnetosphere. Edward C. Sittler, R. E. Hartle, Cesar Bertucci, Andrew Coates, Thomas Cravens, Iannis Dandouras et al.
    In Titan: Interior, Surface, Atmosphere, and Space Environment (Ingo Müller-Wodarg , Caitlin A. Griffith, Emmanuel Lellouch, Thomas E. Cravens, Eds). Cambridge University Press (2014) (DOI: 10.1017/CBO9780511667398)
  • Thermal structure of Titan's troposphere and middle atmosphere pp 102-121. F. M. Flasar, R. K. Achterberg, P. J. Schinder
  • The general circulation of Titan's lower and middle atmosphere pp 122-157. S. Lebonnois, F. M. Flasar, T. Tokano, C. E. Newman
  • The composition of Titan's atmosphere pp 158-189. B. Bézard, R. V. Yelle, C. A. Nixon
  • Storms, clouds, and weather pp 190-223. C. A. Griffith, S. Rafkin, P. Rannou, C. P. McKay
  • Chemistry of Titan's atmosphere pp 224-284. V. Vuitton, O. Dutuit, M. A. Smith, N. Balucani
  • Titan's haze pp 285-321. R. West, P. Lavvas, C. Anderson, H. Imanaka
  • Titan's upper atmosphere: thermal structure, dynamics, and energetics pp 322-354. R. V. Yelle, D. S. Snowden, I. C. F. Müller-Wodarg
  • Titan's upper atmosphere/exosphere, escape processes, and rates pp 355-375. D. F. Strobel, J. Cui

Individual publications:

  • Hayes et al., A post-Cassini view of Titan's methane-based hydrologic cycle, Nature Geoscience volume 11, pages306–313 (2018) (DOI: 10.1038/s41561-018-0103-y)
  • Hörst, S. M., Titan's atmosphere and climate, Journal of Geophysical Research: Planets, Volume 122, Issue 3, pp. 432–482 (2017) (DOI: 10.1002/2016JE005240)

Lower atmospheric chemistry has more to do with surface

Reta: do we want to link to pre-filled ADS things or not? Find Pubs

Titan Atmosphere Data

Search tools:

  • Event Calendar can be used to find data related to flybys of Titan
  • OPUS is one way to find data

The instruments used to study Titan's atmosphere, grouped by study topic, were:

  • Atmosphere-Surface Interaction Layer
    1. Planetary Boundary Layer (CIRS, ISS, RSS)
    2. Surface-atmosphere interaction data (RADAR, CIRS, ISS, VIMS)
    3. Methane humidity (GCMS)
    4. Clouds and Haze (DISR, ISS, VIMS)
  • Troposphere
    1. Density and Temperature (CIRS, RSS, HASI)
    2. Clouds and Haze (DISR, ISS, VIMS)
  • Stratosphere (~ 45-450 km)
    1. Density and Temperature (CIRS, RSS, HASI, VIMS)
    2. Haze (CIRS, VIMS, ISS, DISR)
  • Mesosphere (~ 450-950 km)
    1. Density and Temperature (UVIS, HASI)
    2. Haze (UVIS, CDA)
  • Thermosphere (> 950 km)
    1. Density and Temperature (INMS, UVIS, HASI, AACS, NAV)
    2. Ionosphere/Plasma composition, density, temperature, conductivity,
    3. magnetic field
    4. (INMS, CAPS, RPWS+LP , RSS, MAG)
  • Exosphere (> 1500 km)
    1. Density and Temperature (INMS, UVIS)
    2. Plasma composition, density, temperature (INMS, CAPS, RPWS+LP)
  • Atmospheric Chemistry
    1. Neutral Photochemistry (CIRS,VIMS, UVIS, INMS)
    2. Ionospheric Chemistry (INMS, CAPS, RPWS+LP, RSS)
    3. Aerosol and Haze Formation (ACP, UVIS, INMS, CAPS, RPWS+IP)
  • Atmospheric Dynamics
    1. Troposphere and Stratosphere (DWE, CIRS, RSS, ISS)
    2. Thermosphere (INMS, RPWS-LP, UVIS)
  • Atmospheric Radiation and Power Sources
    1. Solar power - DISR measurements
    2. Magnetospheric Power (CAPS, MIMI, INMS, UVIS)
    3. Airglow (Dayglow: UVIS); (Nightglow: ISS, UVIS)
    4. Thermal emission (CIRS)

High-Level Data Products by Instrument

Cross-instrument:
From INMS (Ion and Neutral Mass Spectrometer):
From UVIS (Ultraviolet Imaging Spectrograph):

Observation High-Level Data Products


Titan Magnetospheric Interactions

Cassini magnetometer data was used to determine that the internal magnetic field of Titan was at the most very small, but the magnetometer data show that the moon's magnetic environment is strongly affected by its proximity to Saturn's warped and highly dynamic magnetodisk. Saturn's magnetodisc is in turn controlled by the solar wind pressure, Saturn seasons, and inner magnetospheric effects (periodicities and mass loading by rings and by Enceladus).
Cassini data determined that the thermosphere is a chemical factory that initiates the formation of complex positive and negative ions in the high thermosphere as a consequence of magnetospheric-ionospheric-atmospheric interaction involving solar EUV and UV radiation, energetic ions and electrons. It is very dynamic and temporally variable. Qualitatively, Cassini in situ measurements point to an important role for Saturn's magnetospheric interaction as a key driver of this observed variability as well as the solar EUV and UV input. It is likely that solar radiation mostly heats the upper atmosphere, whereas magnetospheric particle precipitation plays a more important role in the ionization of the atmosphere below the main ionosphere.

Key Publications

Needs formatting
            Several chapters from the Titan book published in 2009 provide useful background on Titan’s ionosphere and interaction with Saturn’s magnetosphere.  They include chapters 8 (Waite), 11(Cravens) and 16 (Sittler).

  Brown, R., Lebreton, J. P., & Waite, H. (Eds.). (2009). Titan from Cassini-Huygens. Springer Science & Business Media.

  A number of key references attempted to categorize each Titan flyby according to the magnetospheric environment at the time of the flyby:

  Rymer, A. M., Smith, H. T., Wellbrock, A., Coates, A. J., & Young, D. T. (2009). Discrete classification and electron energy spectra of Titan's varied magnetospheric environment. Geophysical Research Letters, 36(15).

  Simon, S., Wennmacher, A., Neubauer, F. M., Bertucci, C. L., Kriegel, H., Saur, J., ... & Dougherty, M. K. (2010). Titan's highly dynamic magnetic environment: A systematic survey of Cassini magnetometer observations from flybys TA–T62. Planetary and Space Science, 58(10), 1230-1251.

  Simon, S., van Treeck, S. C., Wennmacher, A., Saur, J., Neubauer, F. M., Bertucci, C. L., & Dougherty, M. K. (2013). Structure of Titan's induced magnetosphere under varying background magnetic field conditions: Survey of Cassini magnetometer data from flybys TA–T85. Journal of Geophysical Research: Space Physics, 118(4), 1679-1699.

  Review papers
  Coates, A. J. (2009). Interaction of Titan's ionosphere with Saturn's magnetosphere. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, 367(1889), 773-788.

  Bertucci, C., Duru, F., Edberg, N., Fraenz, M., Martinecz, C., Szego, K., & Vaisberg, O. (2011). The induced magnetospheres of Mars, Venus, and Titan. Space science reviews, 162(1-4), 113-171.

Titan Magnetosphere Data

High-Level Data Products by Instrument

From CAPS (Cassini Plasma Spectrometer):
From MAG (Magnetometer):
  • [C Russel to be delivered]

Magnetosphere models and other high-level data products


For questions and comments, visit the PDS Cassini Contact Page