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…
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.
Mercury
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
Venus
Earth: The only
planet with liquid
water on its
surface and the
only planet with
molecular oxygen
in its atmosphere.
The Earth’s
surface, like that
of Venus, has very
few impact
craters, due to an
active geology
(plate tectonics)
and robust
weathering from
wind and rain.
Earth
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.
Mars
Properties of the Planets
• Terrestrial Planets
– Mercury
– Venus
– Earth
– Mars
Now, the Jovian planets...
• Jovian Planets
– Jupiter
– Saturn
– Uranus
– Neptune
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.
Jupiter
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.
Saturn
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.
Uranus
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
Earth’s.
Neptune
Properties of the Planets
• Terrestrial Planets
– Mercury
– Venus
– Earth
– Mars
• Jovian Planets
– Jupiter
– Saturn
– Uranus
– Neptune
What about Pluto?
We’ll cover Pluto a bit later…..
Pluto: As we shall see
shortly, Pluto is a world
that doesn’t 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.
Pluto
Planet
Distance from
Sun, AU
Mass
MEarth
Radius
REarth
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Let’s look at the
numbers. Please try to
see the similarities
within each class of
planet and the contrasts
between them.
Density
gm/cm3
Planet
Distance from
Sun, AU
Mercury
0.39
Venus
0.72
Earth
1.0
Mars
1.5
Jupiter
5.2
Saturn
9.5
Uranus
19
Neptune
30
Pluto
39
Mass
MEarth
Radius
REarth
Density
gm/cm3
Planet
Distance from
Sun, AU
Mercury
0.39
Venus
0.72
Earth
1.0
Mars
1.5
Jupiter
5.2
Saturn
9.5
Uranus
19
Neptune
30
Pluto
39
Mass
MEarth
Radius
REarth
Terrestrial
Planets
Density
gm/cm3
Planet
Distance from
Sun, AU
Mercury
0.39
Venus
0.72
Earth
1.0
Mars
1.5
Jupiter
5.2
Saturn
9.5
Uranus
19
Neptune
30
Pluto
39
Mass
MEarth
Radius
REarth
Terrestrial
Planets
Jovian Planets
Density
gm/cm3
Meter-stick Ninja
Earth
1”
Jupiter
5.2”
Saturn
10”
Pluto
39”
Uranus
19”
Neptune
30”
This meter stick ninja is a cute way of visualizing the
relative distances of the planets form the Sun. In this
Meter-stick Ninja
Earth
1”
Jupiter
5.2”
Uranus
19”
Pluto
39”
Saturn
10”
Mercury 1/3”
Venus ¾”
Mars 1 ½”
Neptune
30”
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.
Sunrise on the Planets
A 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.
Sunrise on Mercury
Available Solar Energy ~9,350 W/m2
Sunrise on Earth
Available Solar Energy ~1,350 W/m2
Sunrise on Jupiter
Available Solar Energy ~50 W/m2
Sunrise on Saturn
Available Solar Energy ~15 W/m2
Sunrise on Uranus
Available Solar Energy ~4 W/m2
Sunrise on Neptune
.
Available Solar Energy ~1.6 W/m2
Planet
Distance from
Sun, AU
Mass
MEarth
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
Radius
REarth
Density
gm/cm3
Now we’ll
compare the
masses of the
planets. Note
that we will
use the Earth
as a standard
mass for
convenience.
Planet
Distance from
Sun, AU
Mass
MEarth
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
Radius
REarth
Density
gm/cm3
Terrestrial
Planets
Planet
Distance from
Sun, AU
Mass
MEarth
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
Radius
REarth
Density
gm/cm3
Terrestrial
Planets
Jovian Planets
Imagine a “planetary balance” that could weight the planets in
terms of Earth masses. How would the other planets compare?
About 9 planet
Mars’ to equal
one Earth
About 17 planet
Earth’s to equal
one Neptune
About 318 planet
Earth’s to equal
one Jupiter
Planet
Distance from
Sun, AU
Mass
MEarth
Radius
REarth
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
Density
gm/cm3
Now,
we’ll
examine
the radii
of the
planets.
Planet
Distance from
Sun, AU
Mass
MEarth
Radius
REarth
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
Density
gm/cm3
Terrestrial
Planets
Terrestrial Planet Radii
Earth
Venus
These images
of the
Terrestrial
planets are
approximately
to scale.
Mars
Mercury
Planet
Distance from
Sun, AU
Mass
MEarth
Radius
REarth
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
Density
gm/cm3
Terrestrial
Planets
Jovian
Planets
Jovian Planets radii
These images
of the Jovian
planets are
approximately
to scale.
Uranus
Neptune
Jupiter
Saturn
Saturn
Notice how
large all the
Jovian
planets are
compared to
the largest
Terrestrial
Planet, Earth
Uranus
Jovian Planets compared to Earth
Earth
Jupiter
Saturn
Neptune
A Mnemonic for the Radii of Terrestrial Planets
1 R   Venus
…and Friends
1 R   Mars
2
1 R  Mercury
3 
1 R  Moon
4 
1 R   Pluto
5
This is a useful memory aid for the radii of Terrestrial Planets.
Planet
Mercury
Venus
Earth
Mars
Mass
Radius
Distance from
Sun,
MEarth density.
REarth
Now,AU
We’ll examine
Density
a
0.39 of an object
0.06 tells
0.38
scientist something about the
0.72
0.82
0.95
composition of the object.
1.0 bench mark
1.0 densities
1.00
Some
follow:
1.5
0.11
0.53
Density
gm/cm3
5.4
5.2
5.5
3.9
Jupiter
5.2
Material
318Density
11.2
1.3
Saturn
9.5
Water
951.0 g/cm
9.53
0.7
Uranus
19
14
4.0
1.3
30
17
3.9
1.6
0.002
0.18
2.0
Neptune
Pluto
Rock
Iron
39
3 to 5
g/cm3
7.8 g/cm3
Planet
Mercury
Venus
Mass
Radius
Distance from
Sun,
MostAU
TerrestrialM
Planets
have
REarth
Earth
densities around 5.3 g/cm3
0.39 a composition
0.06 of mostly
0.38
indicating
rock with a smaller amount of iron
Density
gm/cm3
5.4
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
Planet
Mercury
Venus
Mass
Radius
Distance from
Sun,
MostAU
TerrestrialM
Planets
have
REarth
Earth
densities around 5.3 g/cm3
0.39 a composition
0.06 of mostly
0.38
indicating
rock with a smaller amount of iron
Density
gm/cm3
5.4
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
Mars,
a anomalously
9.5however, has95
9.5
low density. We’ll try to explain
19the density is14
4.0
why
low when we
discuss planet formation.
0.7
Saturn
Uranus
Neptune
Pluto
1.3
30
17
3.9
1.6
39
0.002
0.18
2.0
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
Uranus
Neptune
Pluto
The Jovian planet densities are
MUCH
9.5 lower than the
95 Terrestrial
9.5
planets. These densities are
19
14
4.0
consistent
with a compositon
of
compressed gas.
0.7
1.3
30
17
3.9
1.6
39
0.002
0.18
2.0
Density Trend in the Solar System
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Density, gm/cc
6
5
4
3
2
1
0
0
5
10
15
20
25
30
35
40
Distance from Sun, AU
This graph displays the density vs. distance from the Sun for each planet
Density Trend in the Solar System
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Density, gm/cc
6
5
4
3
2
1
0
0
5
10
15
20
25
30
Distance from Sun, AU
This trend can be model by the dotted line.
35
40
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
Mars
Jupiter
1.0 contrasts Pluto’s
1.0 properties
1.00 with the5.5
This slide
other1.5
planets. You can
see that 0.53
it does not fit the
0.11
3.9
pattern of the Jovian planet in mass, radius or
5.2 Neither does318
11.2
1.3
density.
it fit the Terrestrial
planets.
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
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
In my on-site class I ask my students to memorize the numbers you can
39 no less of0.002
0.18
2.0
seePluto
on this slide. I expect
you.
Planet
Distance from
Sun, AU
Mass
MEarth
Radius
REarth
MercuryPlease notice
0.39that the closest
0.06Jovian planet,
0.38
Density
gm/cm3
5.4
Jupiter, is also the largest in mass and radius. We
Venus will have 0.72
an explanation 0.82
for why the0.95
closest Jovian5.2
planet is the largest and why the succeeding Jovian
Earth planets tend
1.0to get smaller1.0
1.00
5.5
in mass and radius
Solar System.3.9
Mars when we look
1.5 at the formation
0.11 of the0.53
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
Planetary Systems are characterized by two classes
of planets with mutually exclusive properties.
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
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
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?
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?
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?
We will answer these questions later.
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?