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The Planets (in two parts)
The Inner Planets
The inner 4 planets are called Terrestrial planets
What do you think?
• Is the temperature on Mercury, the closest
planet to the Sun, higher than the
temperature on Earth?
• What is the composition of the clouds
surrounding Venus?
• Does Mars have surface liquid water today?
• Is life known to exist on Mars today?
First, we need some basics
• Within the solar system we measure
distances with the unit of an Astronomical
Unit
• This is the average distance between the
Sun and the Earth
We will use the Earth as a basis for Comparison
Mercury
Large portions of Mercury weren’t imaged until 2008-2009
2011 finally bought complete images of Mercury
This image of Mercury is from NASA’s Messenger probe from
October 2008
Photographs from
Mariner 10
(1973) reveal
Mercury’s lunar
like surface.
What are the
similarities?
What are the
differences?
What does that
tell us about
Mercury?
Mercury
Moon
Caloris Basin
Note the edge of
a huge crater on
the left, mostly
in shadow.
Unusual, Hilly
Terrain
The tiny, fine-grained
wrinkles are actually
closely spaced hills.
Mercury also has numerous long cliffs, called scarps,
believed to have formed when the planet cooled
Link to formation of a scarp
Mercury is not hospitable for Human Life
• Mercury’s temperature range is the most extreme in the
solar system
• Mercury’s slow 58 Earth day rotation and the lack of an
appreciable atmosphere means temperatures vary
enormously from one side of the planet to the other.
• Daytime with the Sun overhead reaches 700K (or 800°F)
• Midnight with the Sun completely obscured is 100K (or 280°F)
• Earth typically has temperature differences between day and
night of about 11K (or 20°F)
Mercury Fast Facts
• Mercury has a dry dusty surface
• The surface of Mercury is much like our
Moon
• Mercury has almost no atmosphere
• Mercury has wild temperature swings
• Mercury has no moons
Venus
The surface of
Venus is
completely
hidden beneath
permanent cloud
cover
•Mercury is called “Evening Star”
Why would it be called this?
•Although it is 0.723AU from the
Sun, to us it always appears close to
the Sun
Venus
• Atmosphere is 96% CO2 and 4% N2
• Venus has dropplets of concentrated
sulfuric acid in its clouds
• The atmospheric pressure on Venus is 90
times that of Earth
• Temperature is 750K
– much higher than Mercury
– daytime AND nightime. Why?
– caused by the greenhouse effect
The greenhouse effect heats Venus’s surface
We see dramatic
increases in both pressure
and temperature as we
approach the surface of
Venus.
At the surface, the
temperature is an
astounding 860F, even
hotter than Mercury.
The extreme heating of Venus’ surface is caused by
the greenhouse effect
The carbon dioxide in
the atmosphere of Venus
acts as a “greenhouse,”
trapping the heat from
the Sun underneath and
the temperature rising
until finally thermal
equilibrium is
reached…when the
surface is 860F!
A global view of Venus using
radar images from the
Magellan spacecraft
The craters found on Venus tend to be in
clusters.
This suggests that they were formed from a
large single piece of falling debris that was
broken up by the Venusian atmosphere.
Venus is covered with gently rolling hills, two
“continents,” and numerous volcanoes
The Magellan spacecraft, in an orbit around Venus, was able to “see
through” the thick clouds using radar, giving us the best view of our
sister planet.
This false color map of Venus, equivalent to a
topographical map of Earth, shows the large-scale surface
features of the planet.
Venus fast facts
•Venus is about the size of Earth
•Venus has an atmosphere that is very thick, giving a
very high atmospheric pressure
•On Venus it rains concentrated sulfuric acid
•The atmosphere is mostly CO2, leading to a nasty
greenhouse effect
•Venus rotates in the opposite direction of other planets
•Venus has no moons
Mars
Mars has been the Center of Speculation about
Extraterrestrial Life
Early telescope images showed features
which were perceived as irrigation
canals.
People feared an attack from Mars, like
this one portrayed in “The War of the
Worlds.”
Mars Atmosphere
•Mars has an atmosphere, but it is
only 0.006 times as dense as that of
the Earth.
•It is made up of CO2 and N2
•It is thought that Mars used to have
liquid water
•What happened?
Mars as viewed
from Earth
Impact Craters on Mars
Most of these craters are found in the Southern Hemisphere, suggesting that the
northern vastness has been resurfaced.
•Like Earth,
Mars has polar
ice caps that
grow and shrink
with the
changing
seasons.
•Unlike Earth, the
polar ice caps are
not water but
frozen carbon
dioxide or what
we know as dry
ice.
Martian Seasons
Mars is tilted on its axis by 25.19 (nearly the same as Earth) and the hemispheres
experience seasons that can be observed by examining the polar caps.
Large ice cap made mostly of frozen carbon
dioxide (dry ice)
The dry ice melts, leaving a much smaller
polar cap
Enormous
shield
volcanoes
Valles Marineris is many times larger than the Grand Canyon. On
Earth is would stretch from NY to LA
Topographical Map of Mars
Olympus Mons - the largest volcano in the solar
system has a base larger than the state of Colorado
The Martian surface also has some unusual
features
Apparent “face” on the
Martian surface
22 years later, with improved
technology the feature looks more
natural
Surface features indicate that
water once flowed on Mars
Ohio
River
valley
on Earth
River
channels
on Mars
Surface features believed to
be ancient waterways
A dried riverbed
An ancient lake
Sedimentation
Viking I Lander Picture from 1976
The red color comes form oxidized iron (rust)
1999 Picture
from the Mars
Pathfinder
Lander - Sagan
Station
Note the remotecontrol rover,
Sojourner, next to
a Martian rock
Martian air is thin and often filled
with dust
• Mars’ thin atmosphere is 95% CO2
• Mars’ atmospheric pressure is about 1% as
high as Earth’s
• Mars’ coldest temperatures occur at the
poles at about 160K (-170°F)
• Typical Mars temperatures range between
50°F and -80°F
• Dust storms and dirt devils form on Mars
The Martian meteorite found
in Antarctica has not
provided conclusive evidence
about life on Mars
Mars’ two moons, Phobos and Deimos,
look more like potatoes than spheres
Mars fast Facts
• Mars has an atmosphere, but it is only <1%
of Earth’s
• Mars is dry, but used to have water
• Mars is colder than Earth
• Mars’ poles are so cold, the polar caps are
dry ice
• Mars is a little smaller than Earth
• The Red color is due to oxidized iron (rust)
Part 2: The Outer Planets also called
Jovian Planets
Gas planets are big balls of gas, they are held together by gravity,
but they don’t have a solid surface.
Jupiter’s clouds move in east-west bands
Reddish-colored belts alternate with white-colored zones.
Against the background of
zones and belts, turbulent
swirling cloud patterns,
called white and brown
ovals, form.
The Great Red Spot is a huge
typhoon-like storm of swirling
gasses that has lasted for at
least 300 years and in which
two Earths could fit side to
side.
Jupiter is a called a gas
giant. It is called this
because it is made up of
mostly gas. It is thought
to only have a small
solid surface. You could
not stand on Jupiter
because there is nothing
to stand on.
Jupiter is a long way
from the Sun. The
average temperature of
its surface clouds is 108⁰C (-162⁰F)
Jupiter has rings too!
These 6 pictures were taken from Earth (Hawaii) in the IR spectrum of
Jupiter’s rings which are mostly made of small rocks
Jupiter has 63 moons, so many some of
them have not even been named yet!
These are some of the big ones.
These are the ones Galileo saw in 1609-1610
Europa
Europa houses liquid water
under its icy surface.
Scars on Europa’s surface are
believed to be caused by rising
warmed ice.
Ganymede
Ganymede, the largest satellite in the solar system, is even
larger than Mercury.
These images of Ganymede’s largest feature, a huge, dark,
circular region called Galileo Regio, show deep furrows in the
moon’s icy crust.
Jupiter fast facts
• Jupiter is 318 times as massive as Earth
• Jupiter has a diameter ~11 larger then Earth, this
doesn’t seem like a lot until you see a scale diagram
• The density of Jupiter is only 0.24 Earth density,
Earth would float on Jupiter!
• The Earth could float on Jupiter because it doesn’t
have a solid surface!
• Although the Jupiter is so much, much more
massive, it is also larger than Earth, its gravity is
only 2.4 times as great
• Jupiter has rings made of mostly rocks
Saturn, like Jupiter, has
bands of belts and zones
There is much less
contrast between the
belts and zones on
Saturn than on
Jupiter.
Also, there is very little
swirling structure in
Saturn’s clouds. It’s
cold!
In contrast to Jupiter,
Saturn’s rings are
made almost entirely
of water ice
Comparison of Jupiter’s and Saturn’s Atmospheres
The interiors of Jupiter and
Saturn are similar in
structure.
However, with less mass,
Saturn does not convert as
much of its hydrogen into
liquid.
(On both planets, the hydrogen is
under such intense pressure that it
forms metallic hydrogen. Metallic
hydrogen is degenerate matter,
which means it is so compressed
that the spacing between the nucleus
an the electrons is no longer spaced
like we conceive of it on Earth)
Our view of Saturn’s rings during its 30-year
revolution around the Sun
At some points in its orbit, we see the full face of the rings, and
sometimes the rings disappear when we see them edge-on.
Saturn has Many Diverse Moons
MINAS
ENCELADUS
TEHY
S
Saturn has 60 moons,
many recently found, one
Titan, is the 2nd largest in
the solar system
DIONE
RHEA
SATURN’S MOONS
IAPETUS
PHOEB
E
Titan has an atmosphere three times thicker than that of Earth. It is
composed of nitrogen, methane and a variety of carbon-hydrogen
compounds called hydrocarbons.
Saturn Fast Facts
• Saturn has the most distinct rings of any planet
in out solar system
• Saturn’s rings are made up mostly of water ice
• Saturn like Jupiter is a Gas Giant and has no
Solid surface
• Saturn is even colder than Jupiter
• Saturn has a diameter ~9 times larger than
Earth and is 95 times more massive
• Like Jupiter, Saturn is much more massive
than Earth, but the gravity is less, .91!
Uranus and Neptune
are Comparable in Size
EARTH ON
THE SAME
SCALE
URANUS
NEPTUNE
Uranus’ name is Dirty
Uranus can be pronounced two ways, both are equally right
according to “Universe Today”
Your anus
Or
Urine es
Either one should have been thought out better by for us
English speakers by the guy who named it Sir William
Herschel
The Uranus axis of rotation is tilted on its
side, making seasonal changes drastic.
The interiors of Uranus and Neptune are both
believed to have the same layers.
The Moons and Rings of Uranus
The rings of Uranus are much darker than
those of Saturn.
There are many fine
dust particles between
the main rings.
Uranus has 27
known moons
named after
Shakespeare
and Alexander
Pope
Characters The moon Miranda’s patchwork surface
suggests that huge chunks of rocks and
ice came back together after a huge
impact.
Neptune’s Atmosphere
Ultraviolet images reveal a band-like
structure similar to Jupiter and
Saturn. But it is really cold out here.
The Great Dark Spot was a
surprising find on a planet where it
was thought that temperatures
were too cold to sustain such
storms.
Like Uranus, Neptune is Surrounded
by Thin, Dark Rings
Neptune’s moon Triton has
a retrograde orbit around
the planet, suggesting it
was captured by Neptune.
A possible frozen water
ice lake
Uranus and Neptune Fast Facts
•
•
•
•
•
These guys are gas giants
They are very cold
Both are blue and have faint rings
Both are thought to have lots of water
The water is not what makes them blue
Before we get to Pluto, we need
to make life a little Easier
Here is a mnemonic to help remember the order to
the planets (plus Pluto)
1. My very easy method just set up nine planets
2. My very excellent Mother Just served us nine Pizzas
3. My very educated mother just showed us nine planets
Pluto was Discovered as it Moved against the
Background of Stars
Pluto’s moon Charon was
originally thought to be a
defect in the images of Pluto.
Pluto and Charon are
about the same size.
They are locked in a
mutual synchronous
orbit in which the same
sides of Pluto and
Charon always face
each other.
These images from the Hubble
Space Telescope are the best
we have of Pluto. They were
released in Feb 2010 and show
that Pluto has had a dramatic
change in surface color.
Pluto’s downfall
• In 2006 Pluto was downgraded from a
planed to a Plutoid or Dwarf Planet
• This was because
• Many other objects of greater mass are
being discovered in out solar system
• Pluto has does not orbit in the same plane
as the other planets
• Bye Bye Pluto
WHAT DID YOU THINK?
• Is Jupiter a “failed star?”
• No. Jupiter has 75 times too little mass to shine
as a star.
• What is Jupiter’s Great Red Spot?
• A long-lived, oval cloud circulation similar to
a hurricane on Earth.
• Does Jupiter have continents and oceans?
• No. The only solid matter in Jupiter is its core.
•
•
•
•
WHAT DID YOU THINK?
Is Saturn the only planet with rings?
No. Jupiter, Uranus and Neptune also have rings.
Are the rings of Saturn solid?
No. The rings are composed of thin, closely spaced
ringlets consisting of particles of ice and ice-coated
rocks.
• Do all moons rise and set as seen from their
respective planets?
• No. The one exception is Pluto’s moon Charon,
which remains over the same place on Pluto at all
times.
What did you think?
• Is the temperature on Mercury, the closest planet to the
Sun, higher than the temperature on Earth?
The temperature on the daytime side of Mercury is much higher
than on Earth, but the temperature on the nighttime side of
Mercury is much lower than on Earth because Mercury rotates so
slowly and has little atmosphere to retain heat.
• What is the composition of the clouds surrounding Venus?
The clouds are composed primarily of sulfuric acid.
• Does Mars have surface liquid water today?
No, but there are strong indications that it had liquid water in the
distant past.
• Is life known to exist on Mars today?
No life has yet been discovered on Mars.
Self-Check
1: Compare and contrast the atmospheres of the terrestrial
planets in terms of temperature, pressure, and chemical
composition.
2: List the properties that Mercury has in common with the
other terrestrial planets and with the Moon.
3: Compare and contrast the surfaces of Mercury, Mars, and
Venus with that of the Earth in terms of geologic structures
and evidence regarding tectonic activity.
4: Describe plausible explanations for the absence of water
vapor in the Venusian and Martian atmospheres.
Self-Check
6: Discuss the evidence for the existence of water on Mars
surface in the past and the location and form of that water
today.
7: Discuss the reasons for what we can see when we look at a
planet from outer space, for example, earth has got distinct
shapes that vary in color and the rest is blue.