Solar System Overview
Astronomy ph290
Quiz: Planetary Characteristics
(1) If we divided the planets into inner and outer groups, which planets would be
in each group?
Mercury, Venus, Earth, Mars are the inner planets (generally small, dense) while Jupiter,
Saturn, Uranus and Neptune are in the outer group (large gas planets with generally
lower density).
(2) Does one planet not clearly fit into either group?
Pluto does not fit into either group - it is very small, yet located after the gas
giant planets.
(3) Based on average density and albedo, what might you suggest about the composition
of the two groups?
The inner planets are "rocky" with densities much higher than that of water. With
the exception of Venus, they are generally darker (lower albedo). The outer planets
are gas giants for which we are looking at cloud layers. The densities are in general
much lower and the albedo somewhat higher than the inner planets.
(4) Considering that an average rock has a density of about 3.5x that of water, what
must be true for the inner planets?
The inner planets must have an inner core of a much higher density substance - iron.
(5) In what way is Venus exceptional?
Venus is exceptional in several ways. It has a much higher albedo than the other
inner planets (due to a dense cloud layer which is effective in reflecting light).
It is also exceptional in having such a very slow rotation on its axis.
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