Properties of the Planets

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Properties of the Planets

• Terrestrial Planets
• Mercury
• Venus
• Earth
• Mars

• Jovian Planets

This presentation will show you some of the
important physical differences between the
Terrestrial and Jovian Planets. First the
Terrestrial planets
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Mercury
Mercury Heavily cratered ancient rocky surface.
The innermost of the planets. We have only
photographed half of its surface because the
planet rotates very slowly and the flyby
spacecraft (Mariner) could only photograph the
sunlit portion.
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Venus
Venus Covered from pole to pole with bright
clouds. The surface cannot be seen from orbit at
visual wavelengths. Radar instruments on the
Magellan spacecraft mapped the surface and found
very few craters suggesting an active geology
that erases resurfaces the ancient landscapes
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Earth
Earth The only planet with liquid water on its
surface and the only planet with molecular oxygen
in its atmosphere. The Earths surface, like
that of Venus, has very few impact craters, due
to an active geology (plate tectonics) and robust
weathering from wind and rain.
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Mars
Mars The last Terrestrial planet. If has an
anomolusly low density for a terrestrial planet,
suggesting that it is made of a different mix of
materials than the other terrestrial planets.
Its surface shows signs of ancient geology, but
no evidence recent wide scale activity. Where is
the water on Mars is the focus of current
scientific work.
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Properties of the Planets

• Terrestrial Planets
• Mercury
• Venus
• Earth
• Mars

• Jovian Planets
• Jupiter
• Saturn
• Uranus
• Neptune

Now, the Jovian planets...
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Jupiter
Jupiter The closest Jovian planet. Composed
almost entirely of hydrogen and helium gas, this
planet began as a giant ball of ice and rock that
attracted a deep atmosphere of gas from the
nebula (cloud of gasses) the Sun and planets
formed from.
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Saturn
Saturn Almost ten times farther from the Sun
than the Earth, this could world of gasses the
most spectacular set of rings of all the Jovian
planets. The rings are believed to be the remains
of a moon that drifted to close to Saturn abd
broke apart, distributing its material around the
equatorial plane.
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Uranus
Unanus The first telescopically discovered
(1781) planet. It remains the most mysterious
of planets. No clouds can be seen it is hydrogen
and helium atmosphere tinted blue by a slight
enrichment of methane. Further adding to the
mystery, the rotation axis of Uranus is tipped
almost 90 degrees relative to the ecliptic
suggesting some catastrophic event slammed into
Uranus and knocked it over.
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Neptune
Neptune Much like Uranus in appearance, size and
compostion, although cluds can be seen throuogh
the atmosphere. These most distant Jovian
planets are the runts of the Jovian litter, yet
they still occupy a volume more than that of 64
Earths.
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Properties of the Planets

• Terrestrial Planets
• Mercury
• Venus
• Earth
• Mars

• Jovian Planets
• Jupiter
• Saturn
• Uranus
• Neptune

What about Pluto?
Well cover Pluto a bit later..
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Pluto
Pluto As we shall see shortly, Pluto is a world
that doesnt fit the pattern established by the
other planets. It is far too small and of the
wrong composition to be a Jovian planet and too
small, too far away and the wrong composition to
be a Terrestrial planet. Pluto, shown here with
its moon Charon, may be pieces of a planet that
was not able to finish its formation. It is
considered to be a piece of debris leftover from
the era of planet formation.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Lets look at the numbers. Please try to see the
similarities within each class of planet and the
contrasts between them.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39
Venus 0.72
Earth 1.0
Mars 1.5
Jupiter 5.2
Saturn 9.5
Uranus 19
Neptune 30
Pluto 39
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39
Venus 0.72
Earth 1.0
Mars 1.5
Jupiter 5.2
Saturn 9.5
Uranus 19
Neptune 30
Pluto 39
Terrestrial Planets
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39
Venus 0.72
Earth 1.0
Mars 1.5
Jupiter 5.2
Saturn 9.5
Uranus 19
Neptune 30
Pluto 39
Terrestrial Planets
Jovian Planets
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This meter stick ninja is a cute way of
visualizing the relative distances of the planets
form the Sun. In this image, imagine that 1
inch equals 1 A.U. Since there are about 39
inches in a meter, the entire retinue of planets
can be placed on a single meter stick at this
scale.
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Meter-stick Ninja
Pluto 39
Earth 1
Jupiter 5.2
Uranus 19
Saturn 10
Neptune 30
Mercury 1/3 Venus ¾ Mars 1 ½
Notice that, at this scale, all the Terrestrial
Planets are within 1½ inches from the Sun. The
Jovian planets are spread between 5 inches and 30
inches.
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Sunrise on the PlanetsA simulation

• The next series of slides are meant to help you
  visualize the effect of the vast distances of the
  Solar System by simulating, in a simple way, what
  sunrise would look like from each planet, taking
  into account its distance from the Sun. At the
  bottom of each slide appears the amount of solar
  energy available at that distance from the Sun.
  The solar energy follows an inverse square law
  like gravity. Notice how rapidly the available
  solar energy drops as you progress through the
  solar system.

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Sunrise on Mercury
Available Solar Energy 9,350 W/m2
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Sunrise on Earth
Available Solar Energy 1,350 W/m2
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Sunrise on Jupiter
Available Solar Energy 50 W/m2
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Sunrise on Saturn
Available Solar Energy 15 W/m2
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Sunrise on Uranus
Available Solar Energy 4 W/m2
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Sunrise on Neptune
.
Available Solar Energy 1.6 W/m2
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06
Venus 0.72 0.82
Earth 1.0 1.0
Mars 1.5 0.11
Jupiter 5.2 318
Saturn 9.5 95
Uranus 19 14
Neptune 30 17
Pluto 39 0.002
Now well compare the masses of the planets.
Note that we will use the Earth as a standard
mass for convenience.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06
Venus 0.72 0.82
Earth 1.0 1.0
Mars 1.5 0.11
Jupiter 5.2 318
Saturn 9.5 95
Uranus 19 14
Neptune 30 17
Pluto 39 0.002
Terrestrial Planets
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06
Venus 0.72 0.82
Earth 1.0 1.0
Mars 1.5 0.11
Jupiter 5.2 318
Saturn 9.5 95
Uranus 19 14
Neptune 30 17
Pluto 39 0.002
Terrestrial Planets
Jovian Planets
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Imagine a planetary balance that could weight
the planets in terms of Earth masses. How would
the other planets compare?
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About 9 planet Mars to equal one Earth
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About 17 planet Earths to equal one Neptune
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About 318 planet Earths to equal one Jupiter
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38
Venus 0.72 0.82 0.95
Earth 1.0 1.0 1.00
Mars 1.5 0.11 0.53
Jupiter 5.2 318 11.2
Saturn 9.5 95 9.5
Uranus 19 14 4.0
Neptune 30 17 3.9
Pluto 39 0.002 0.18
Now, well examine the radii of the planets.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38
Venus 0.72 0.82 0.95
Earth 1.0 1.0 1.00
Mars 1.5 0.11 0.53
Jupiter 5.2 318 11.2
Saturn 9.5 95 9.5
Uranus 19 14 4.0
Neptune 30 17 3.9
Pluto 39 0.002 0.18
Terrestrial Planets
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Terrestrial Planet Radii
These images of the Terrestrial planets are
approximately to scale.
Earth
Mars
Venus
Mercury
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38
Venus 0.72 0.82 0.95
Earth 1.0 1.0 1.00
Mars 1.5 0.11 0.53
Jupiter 5.2 318 11.2
Saturn 9.5 95 9.5
Uranus 19 14 4.0
Neptune 30 17 3.9
Pluto 39 0.002 0.18
Terrestrial Planets
Jovian Planets
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Jovian Planets radii
Uranus
These images of the Jovian planets are
approximately to scale.
Neptune
Jupiter
Saturn
Saturn
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Jovian Planets compared to Earth
Notice how large all the Jovian planets are
compared to the largest Terrestrial Planet, Earth
Uranus
Neptune
Earth
Jupiter
Saturn
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A Mnemonic for the Radii of Terrestrial Planets
and Friends
This is a useful memory aid for the radii of
Terrestrial Planets.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
Now, Well examine density. Density of an object
tells a scientist something about the composition
of the object. Some bench mark densities
follow Material Density Water 1.0
g/cm3 Rock 3 to 5 g/cm3 Iron 7.8 g/cm3
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
Most Terrestrial Planets have densities around
5.3 g/cm3 indicating a composition of mostly rock
with a smaller amount of iron
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
Most Terrestrial Planets have densities around
5.3 g/cm3 indicating a composition of mostly rock
with a smaller amount of iron
Mars, however, has a anomalously low density.
Well try to explain why the density is low when
we discuss planet formation.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
The Jovian planet densities are MUCH lower than
the Terrestrial planets. These densities are
consistent with a compositon of compressed gas.
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This graph displays the density vs. distance from
the Sun for each planet
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This trend can be model by the dotted line.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
This slide contrasts Plutos properties with the
other planets. You can see that it does not fit
the pattern of the Jovian planet in mass, radius
or density. Neither does it fit the Terrestrial
planets.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
In my on-site class I ask my students to memorize
the numbers you can see on this slide. I expect
no less of you.
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Planet Distance from Sun, AU Mass MEarth Radius REarth Density gm/cm3
Mercury 0.39 0.06 0.38 5.4
Venus 0.72 0.82 0.95 5.2
Earth 1.0 1.0 1.00 5.5
Mars 1.5 0.11 0.53 3.9
Jupiter 5.2 318 11.2 1.3
Saturn 9.5 95 9.5 0.7
Uranus 19 14 4.0 1.3
Neptune 30 17 3.9 1.6
Pluto 39 0.002 0.18 2.0
Please notice that the closest Jovian planet,
Jupiter, is also the largest in mass and radius.
We will have an explanation for why the closest
Jovian planet is the largest and why the
succeeding Jovian planets tend to get smaller in
mass and radius when we look at the formation of
the Solar System.
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Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.
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Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.

• Terrestrial Planets
• Close to the central star
• Small in mass and radius
• High density

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Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.

• Terrestrial Planets
• Close to the central star
• Small in mass and radius
• High density

• Jovian Planets
• Far from the central star
• Large in mass and radius
• Low density

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Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.

• Terrestrial Planets
• Close to the central star
• Small in mass and radius
• High density

• Jovian Planets
• Far from the central star
• Large in mass and radius
• Low density

Why are planetary systems organized in this
manner? Is there an over-arching principle that
explains this pattern? How common are planetary
systems around other stars and how common are
Earth-like planets?
53
Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.

• Terrestrial Planets
• Close to the central star
• Small in mass and radius
• High density

• Jovian Planets
• Far from the central star
• Large in mass and radius
• Low density

Why are planetary systems organized in this
manner? Is there an over-arching principle that
explains this pattern? How common are planetary
systems around other stars and how common are
Earth-like planets?
54
Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.

• Terrestrial Planets
• Close to the central star
• Small in mass and radius
• High density

• Jovian Planets
• Far from the central star
• Large in mass and radius
• Low density

Why are planetary systems organized in this
manner? Is there an over-arching principle that
explains this pattern? How common are planetary
systems around other stars and how common are
Earth-like planets?
55
Planetary Systems are characterized by two
classes of planets with mutually exclusive
properties.
We will answer these questions later.

• Terrestrial Planets
• Close to the central star
• Small in mass and radius
• High density

• Jovian Planets
• Far from the central star
• Large in mass and radius
• Low density

Why are planetary systems organized in this
manner? Is there an over-arching principle that
explains this pattern? How common are planetary
systems around other stars and how common are
Earth-like planets?