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

FIGURE 7.5 Top: This composite compares the optically thick rings, such as the epsilon (upper line),
and optically thin rings, such as the zeta (lower line), at different viewing angles. Bottom: Images from
the Keck 10-m telescope shows the changing aspect of Uranus as it approached the 2007 equinox, as well
as the improving quality of Keck’s adaptive optics (AO) system as it was tuned for Uranus. At this
wavelength (2.2 microns) methane absorption darkens the planet except for discrete cloud features
reaching altitudes high enough to be above the bulk of the methane. SOURCE: Top: Courtesy of Imke
de Pater (UC Berkeley), Heidi B. Hammel (SSI, Boulder), and the W.M. Keck Observatory. Bottom:
From I. de Pater, H.B. Hammel, M.R. Showalter, and M.A. van Dam, The dark side of the rings of
Uranus, Science 317(5846):1888-1890, 2007. Reprinted with permission from AAAS.
Important Questions
Some important questions concerning ring systems as laboratories for planetary formation
processes include the following:
• What can the significant differences among ring systems teach us about the differing origins,
histories, or current states of these giant planet systems?
• Can the highly structured forms of the Uranus and Neptune ring systems be maintained for
billions of years, or are they “young”? Are their dark surfaces an extreme example of space weathering?
• What drives orbital evolution of embedded moonlets; how do they interact with their disks?
• What drives mass accretion in a ring system?
PREPUBLICATION COPY—SUBJECT TO FURTHER EDITORIAL CORRECTION
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