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

INTERCONNECTIONS
Links to Other Parts of the Solar System
Comparative planetary studies offer great potential to improve our understanding of planetary
systems in general. Knowledge gained about any of the terrestrial planets helps us to understand the
origin and evolution of Earth-like planets in general. In the same vein, missions to the giant planets will
help us to understand the basic physical properties of gas and ice giant planets as a class. In terms of the
origin and evolution of the giant planet systems, learning about the planets, their satellites, and even other
regions of the outer solar system (Kuiper belt objects, plutoids, comets, etc.) all help us to understand how
conditions began and evolved over the lifetime of the solar system. Several aspects of giant planet
science have connections to terrestrial planets, including but not limited to polar vortices, stratospheric
oscillations, effects of planetary migration and volatile delivery, and the physics of large airbursts.
Links to Heliophysics
The giant planets are the only solar system examples, besides Earth, of planets with strong
internal magnetic fields interacting with the solar wind. Many of the observed phenomena in the outer
regions of a magnetosphere—including the auroral displays seen near the magnetic poles of Earth,
Jupiter, and Saturn—are controlled in part by interactions with the solar wind. In the case of Earth, most
of the magnetospheric plasma is actually derived from trapped solar wind, but at Jupiter and Saturn the
main sources appear to be, respectively, Io and either the rings or the icy satellites (especially Enceladus).
At Earth, these interactions have important consequences for human civilization (e.g., disruption in power
distribution networks and satellite communications). Understanding the interactions of the solar wind at
all of the planets aids understanding of the physical processes at Earth.
Links to Extrasolar Planets
The rapidly expanding fields of exoplanets and protoplanetary disks⎯fueled by data from space
observatories as well as ground-based facilities⎯bring a wealth of new ideas regarding the processes that
build and shape planetary systems. The majority of exoplanets discovered to date are giant planets,
though the field is rapidly evolving as the Kepler, CoRoT, and other missions study hundreds of
candidate objects. 95 Current studies of the atmospheres and magnetospheres of the giant planets are
increasingly performed with an eye toward the application to extrasolar giant planets. It is critically
important to understand the basic physics of the giant planets in the solar system if we are to understand
the >500 exoplanets that have been discovered around nearby stars, for which there is a small fraction of
the data that we have about the local giants Jupiter, Saturn, Uranus, and Neptune. 96
Giant planet atmospheres exhibit both super- and sub-rotation with respect to their cores, but the
driving mechanisms are not fully understood. If we cannot understand the origin and physics of
atmospheric dynamics in the local giants’ atmospheres and clouds, our predictions for the circulation
from dayside to nightside in an extrasolar giant that is phase-locked to its star will be of limited
robustness. Understanding thermal balance and tidal effects are critical to understanding the evolution of
extrasolar giant planet atmospheres and orbits.
Remarkably, thermal profiles for many exoplanets have been measured, and hot stratospheres
have been found to be ubiquitous. If we do not understand the energy sources of the hot stratospheres and
coronal upper atmospheres of the local giant planets (and we do not), we will not be able to predict the
conditions in the upper atmosphere of a jovian planet at an orbital distance less than that of Mercury from
its star. This is critical for understanding the rapid escape into space of the atmospheres of extrasolar
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