23 1 The Solar System

The Solar System
Chapter 23, Section 1
The Planets: An Overview
Terrestrial Planet – any of the Earth-like planets:
Mercury, Venus, Earth, and Mars
Jovian Planet – the Jupiter-like planets: Jupiter,
Saturn, Uranus, and Neptune; these planets have
relatively low densities and are huge gas giants
Size is the most obvious difference between the
terrestrial and the Jovian planets
The diameter of the largest terrestrial planet, Earth,
is only ¼ the diameter of the smallest Jovian planet,
Neptune; it’s mass is only 1/17 that of Neptune
Density, chemical makeup, and rate of rotation are
other ways in which the two groups of planets differ
The densities of the terrestrial planets average about
5 times that of water, while the Jovian planets only
average about 1.5 times that of water
Drawn to
The Interiors of the
The substances that make up the planets
are divided into 3 groups: gases, rocks,
and ices
Gases – Hydrogen and Helium (melting
point = -273oC)
Rocks – Silicate minerals and metallic iron
(melting point = 700oC)
Ices – Ammonia, methane, carbon dioxide,
and water (melting point = 0oC)
Terrestrial planets contain mostly rock
material, while the Jovian planets contain
the gases and ices.
The Interiors of the
The Atmospheres of the
A planet’s ability to retain an atmosphere
depends on its mass and size
Jovian planets have thick atmospheres of
hydrogen, helium, methane, and ammonia,
due to their high surface gravities and the
ability to hold on to the light gases
Terrestrial planets have very small
atmospheres in comparison, with the
atmosphere making up only a small portion
of the planet’s mass
The Atmospheres of the
Formation of the Solar
System – Nebular Theory
Nebula – a cloud of dust and gas in space
These thin gaseous clouds begin to rotate
and contract, and then spin faster
According to the nebular theory, the sun
and planets formed from a rotating disk of
dust and gases
As the speed of rotation increased, the
center of the disk began to flatten out
The matter became more concentrated in
the center, eventually igniting a nuclear
reaction (the sun)
Formation of the Solar
System – Planetesimals
Planetesimals – small, irregularly shaped
bodies; formed from the collision of matter
in space
As the collisions continued, the
planetesimals grew larger, and began
exerting their own gravity
In the inner solar system, it was so hot that
only the metals and silicate materials could
In the outer solar system, it was cool
enough for the planets to attract ice and
gases to add to their mass
of the
System –
Read Chapter 23, Section 1 (pg. 644-648)
Do Section 23.1 Assessment #1-7 (pg. 648)
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