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

Synergistic observations from an orbiter, a balloon, a mini-probe and two drop sondes will enable
the first truly global 3-dimensional (and to a large extent 4-dimensional, including many measurements of
temporal changes) characterization of Venus’s atmosphere. The mission will return a dataset on Venus’s
radiation balance, atmospheric motions, cloud physics, and atmospheric chemistry and composition. The
relationships and feedbacks among these parameters, such as cloud properties and radiation balance, are
among the most vexing problems limiting the forecasting capability of terrestrial GCMs. Evidence will
also be gathered for the existence, nature and timing of the suspected ancient radical global change from
habitable, Earthlike conditions to the current hostile runaway greenhouse climate, with important
implications for understanding the stability of climate and our ability to predict and model climate change
on earth and extrasolar terrestrial planets. This mission does not require extensive technology
development, and could be accomplished in the coming decade, providing extremely valuable data to
improve our understanding of climate on the terrestrial planets.
New Frontiers-Class
Important contributions can be made to the goals for the study of the inner planets by a Lunar
Geophysical Network.
Lunar Geophysical Network
The 2003 NRC decadal survey identified geophysical network science as a potential high-yield
science mission concept. The importance of geophysical networks to both lunar and solar system science
was strongly affirmed by subsequent reports. 27,28,29 Deploying a global, long-lived network of geophysical
instruments on the surface of the Moon to understand the nature and evolution of the lunar interior from
the crust to the core will allow the examination of planetary differentiation that was essentially frozen in
time at some 3-to-3.5 billion years ago. Such data (e.g., seismic, heat flow, laser ranging, and magnetic
field/electromagnetic sounding) are critical to determining the initial composition of the Moon and the
Earth-Moon system, understanding early differentiation processes that occurred in the planets of the inner
solar system, elucidating the dynamical processes that are active during the early history of terrestrial
planets, understanding the collision process that generated our unique Earth-Moon system, and exploring
processes that are currently active at this stage of the Moon’s heat engine.
FIGURE 5.4 Understanding the interior of the Moon provides both a snapshot for the earliest stages of
the interior evolution of a terrestrial planet and an end-member for understanding evolutionary pathways
taken by planetary heat engines. SOURCE: J.W. Head III, Surfaces and interiors of the terrestrial planets,
pp. 157-173 in The New Solar System (J.K. Beatty, C.C. Petersen, and A., Chaikin, eds.). Sky Publishing,
Cambridge, Mass., Copyright 1999. Reprinted with permission of the Cambridge University Press.
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
5-21