Date: Prior to 1993
On the core of Uranus what is in the water content?
The astronomy texts I looked at seem to agree that the core of
Uranus is composed of a mixture of ice and rock, the core having a radius of
approximately 1/3 of Uranus' radius. One text estimates that the cores of the
gas giants are roughly half water ice and half rock. This guess is based on
trying to match the observed planet densities using estimates for water-ice
density and a "typical" rock density at the pressures believed to exist in the
interiors. However, there was an article in the March 1992 ssue of Sky &
Telescope magazine that questioned the presence of rocky material. The
following is an abstract of that article, provided by the online Reader's
Guide Abstract Index: "Data from Voyager 2 and recent laboratory experiments
suggest that Uranus and Neptune may have highly pressurized slushy interiors
rather than the rocky cores predicted by standard models of planet formation.
William B. Hubbard of the University of Arizona and colleagues mixed water,
ammonia, and isopropanol to create a material similar to the mantle of Uranus,
then subjected the mixture to pressures of 2 million atmospheres. They report
in the August 9, 1991, issue of Science that the characteristics of the
compressed liquid matched models of Uranus and Neptune's interiors so well
that rocky cores became superfluous."
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Update: June 2012