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The NASA Cassini spacecraft will continue investigating Saturn and its rings and moons until the mission is terminated by vaporization of the spacecraft in Saturn’s atmosphere in September 2017. The Astrogeology Program provides key software (ISIS, Integrated Software for Imagers and Spectrometers) to the Cassini mission for analysis of data from the multiple onboard imagers and radar system. Astrogeology’s research has largely focused on Titan and Enceladus.

Titan is a moon with a thick nitrogen atmosphere and a global meteorological cycle involving methane (methane clouds, rain, rivers, and seas akin to Earth’s global hydrological cycle). Topographic information from the radar is used, for example, to identify sites on Titan that are likely to have “cryovolcanism‚” where water behaves like lava at the cryogenic temperatures of the outer Solar System. Another study is to detect lakes of liquid hydrocarbons by observing glints of sunlight off their surfaces with Cassini’s Visual and Infrared Mapping Spectrometer (VIMS). Studies of VIMS data have identified ethane as a major constituent of the lakes and new radar-derived topography is revealing the relief and depth of these lakes. During the last 2 years of the Cassini mission, the Sun’s latitude on Titan is moving northward as northern summer approaches, affording new opportunities to study the seasonal evolution of the lakes, including evaporation, rain, and changes in shorelines.

On tiny Enceladus, more than a thousand times less massive than Titan, Cassini discovered several  plumes that jet gas, ice, salts, and hydrocarbon grit from the southern polar region. Evidently, active chemical processes modulated by tidal forces drive these plumes, which emanate from long, narrow vents  dubbed "tiger stripes." Data from Cassini's Composite InfraRed Spectrometer (CIRS), coupled with thermal modeling techniques developed at Astrogeology, allow high-resolution temperature mapping of these unique structures. It is conceivable that Enceladus' subsurface environment could harbor the chemical ingredients and energy for life’s organic chemical precursors to emerge.


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Randolph Kirk
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