Vision and Voyages for Planetary Science in the - Solar System ...

organisms live there now?” Titan’s complex atmosphere exhibiting a global methane cycle akin to Earth’s
hydrological cycle is key to the understanding the Workings of the Solar System theme and the question
“can understanding the roles of physics, chemistry, geology, and dynamics in driving planetary
atmospheres and climates lead to a better understanding of climate change on Earth?” Finally, the giant
planet satellites exhibit an enormous spectrum of planetary conditions, chemistry, and processes—
contrasting those of the inner solar system and stretching our scientific imaginations in “how have the
myriad chemical and physical processes that shaped the solar system operated, interacted, and evolved
over time?”
SCIENCE GOALS FOR STUDIES OF PLANETARY SATELLITES
The planetary science community has made remarkable progress over the past decade in
understanding the major satellites of the giant planets (Table 8.2), but despite this progress, important
questions remain unanswered. The committee has developed some specific high-level goals and
associated objectives to guide the continued advancement of the study of planetary satellites. The goals
cover the broad areas of origin and evolution, processes, and habitability. They are as follows:
• How did the satellites of the outer solar system form and evolve?
• What processes control the present-day behavior of these bodies?
• What are the processes that result in habitable environments?
Each of these goals is described in more details in subsequent sections.
TABLE 8.2 Major Accomplishments by Ground- and Space-based Studies of the Satellites of the Giant
Planets in the Past Decade
Major Accomplishments Mission and/or Techniques
Discovered an active meteorological cycle on Titan,
involving liquid hydrocarbons instead of water.
Discovered endogenic activity on Enceladus, and found that
the Enceladus plumes have a major impact on the saturnian
environment.
Greatly improved our understanding of the origin and
evolution of Titan’s atmosphere and volatile inventory, and
its complex organic chemistry.
Major improvement in characterizing the processes,
composition and histories for all the saturnian satellites.
Developed new models improving our understanding of
Europa, Io, and the other Galilean satellites.
Cassini and Huygens; ground-based
observations.
Cassini
Theory and modeling based on Cassini and
Huygens’ data
Theory and modeling based on Cassini data
Theory and modeling based on Galileo data;
ground-based observations; and Cassini and
New Horizons.
HOW DID THE SATELLITES OF THE OUTER SOLAR SYSTEM FORM AND EVOLVE?
Understanding the origin and evolution of the satellites is a key goal of satellite exploration.
Satellite composition and internal structure (particularly the state of differentiation), provide important
clues to the formation of these worlds and their parent planet, and the origin and evolution of volatile
species are of particular interest. Orbital evolution, and its intimate connections to tidal heating, provides
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