Download Chapter 23: Touring Our Solar System

Chapter 23: Touring Our Solar
System
23.1: The Solar System
Text pp 644-648
The sun is a hub of a huge rotating
system of eight planets, their
satellites and other small bodies.
About 99.85% of the mass of
our solar system is contained
within the sun.
Most of the remaining 0.15% of
the mass is contained by the
planets.
(Although Pluto is now a dwarf
planet, it is large enough for us to
study it separately.)
Fast Facts on the Solar System
• Each planet moves in an elliptical orbit.
• All planets travel in the same direction.
• The planet closest to the Sun is
Mercury, and it has the fastest orbital
speed of all planets as well as the
shortest period of revolution.
• The (dwarf) planet furthest from the
Sun is Pluto. It has the slowest orbital
speed as well as the longest period of
revolution.
The Planets in order, from
closest to furthest from the sun :
•
•
•
•
•
•
•
•
•
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto (recently reassigned as a “dwarf planet.”)
The Planets: An Overview
• Terrestrial Planets
• Terrestrial =
Earthlike
• AKA “Rocky
Planets, Inner
Planets”
• Mercury, Venus,
Earth, Mars
• Small and rocky.
• Dense, solid.
• Jovian Planets
• Jovian = Jupiter-like
• AKA “Gas Giants,
Outer Planets”
• Jupiter, Saturn,
Uranus, Neptune.
• Huge and gaseous.
• Not dense, made of
gas.
Key Concepts
• Size is the most obvious difference
between the Terrestrial and the Jovian
planets.
• Density, chemical makeup, and the rate
of rotation are other ways in which the
two groups differ.
Planet Interiors
• Terrestrial planets
are dense. They
consist of mostly of
rocky and metallic
substances, and
only small amounts
of gasses and
liquids.
• Jovian planets contain
mostly gases (hydrogen
and helium) and ices
(mostly water, ammonia
and methane.) This
explains their low
densities. What solids
they have are
concentrated in their
cores.
Atmospheres of the Planets
• Terrestrial Planets
• Jovian Planets
• Lower surface
gravity means…
• Low escape velocity
(the speed a gas
molecule needs to
escape Earth’s gravity
& go into space.
Therefore…
• Thin atmospheres
• High surface gravity
means…
• High escape velocity.
Therefore…
• Thick, heavy
atmospheres of
hydrogen, helium,
methane & ammonia.
23.2: The Terrestrial Planets
Text pp 649-653
Mercury- The Innermost Planet
• The innermost and
smallest planet.
• Has cratered highlands,
like Earth’s moon.
• VERY dense - iron core?
• One full day cycle = about
88 earth hours.
• One full orbit cycle = 59
earth days.
• Three months of day/ three
months of night.
Mercury has the greatest temperature
extremes of any planet.
Day temperatures are high
enough to melt lead: +425 C.
Night temperatures can
drop down to -173°C.
The chances of life as we
know it living on Mercury is
practically nonexistent.
Venus – The Veiled Planet
Venus has been called “Earth’s
Twin,” because it is so similar
to Earth in size, density, mass
and location in the Solar
System.
Venus orbits the sun
every 244 earth-days.
It rotates on its axis
about every 225
earth-hours.
Neither Mercury nor Venus
have natural satellites.
Volcanism and tectonic activity have shaped
Venus’ surface. This is also like earth.
Venus is covered with a thick
atmosphere of mostly carbon
dioxide, a greenhouse gas.
It traps solar heat, making
Venus the hottest planet in
the Solar System, over 475 C,
hot enough to melt lead.
Mars – The Red Planet
Mars is called the Red
Planet for its reddish
appearance when viewed
through a telescope.
Mars has some dark regions
that change intensity during
the Martian year. It also has
brilliant white polar caps.
Mars has two natural satellites –
Phobos and Deimos, only discovered in 1977.
The Martian Atmosphere
Mars’ polar ice caps seem
to be made mostly of
frozen carbon dioxide.
The atmosphere of Mars
has only 1% the density of
Earth’s atmosphere. It is
made up of mostly carbon
dioxide and tiny amounts
of water vapor.
Although the atmosphere of Mars is very thin, extensive
dust storms occur and may cause the color changes
observed from Earth. Hurricane-force winds up to 270 kph
can go on for weeks.
Surface Features of Mars
Much of the Martian surface strongly resembles some of
Earth’s desert areas, including dust storms.
Its surface holds numerous large volcanoes; the largest,
Olympus Mons, is the size of Ohio and 23 kilometers high!
There are also several canyons, much larger that Earth’s
Grand Canyon.
Most of Martian surface
features are old by Earth’s
standards. The “newest”
may be more than one
billion years old.
Water on Mars
This is a photograph taken
of a frozen water “puddle”
on the surface of Mars.
There are many
indicators that in the
VERY distant past,
Mars had streams
and islands in large
bodies of water.
Many of its rocks
could not have
formed without water,
as well.
This is an artist’s rendition on how frozen water could be
trapped underneath Mars’ dusty & dry surface.
Most scientists believe
that most surface water
on Mars seeped out
from pockets of
underground ice.
Although there are stream
channels on its surface, most
of Mars’ water has either
evaporated away or re-frozen
in underground pockets.
The Outer Planets
Text pp 654-659
Jupiter: Giant Among Planets
Jupiter has a mass that is 2 ½ times greater than
all the other planets combined.
Had Jupiter been 10 times
larger, it would have
evolved into a small star.
Jupiter completes one rotation
in just less than 10 earth hours –
the fasted rotating planet in the
Solar System.
Jupiter appears to be covered in bands of multicolored
clouds that run parallel to its equator. These are driven
by a constant wind system and the rotation of the planet.
•Jupiter gives off twice as much heat as it absorbs from
the sun. The convection currents produced by this heat
drives the winds at Jupiter’s surface.
Notice how the cloud bands move in opposite directions.
This is because the convection currents underneath
the clouds are rising and sinking.
Jupiter’s most striking feature is the Great Red Spot in its
southern hemisphere. This appears to be a huge cyclone
which has been raging for at least the past 400 years.
At least two earths could fit
into the Great Red Spot.
Here is a video of The Great Red Spot’s wind currents.
Structure of Jupiter
• Jupiter’s atmosphere is mostly
hydrogen and helium.
• Beneath its gaseous surface, Jupiter
may be a ball of liquid hydrogen
underneath its atmosphere because of
its enormous internal pressure.
Jupiter’s Moons
(3)
Jupiter has at least 60
moons.
The four largest are
(4)
(1)Callisto;
(2) Ganymede;
(2)
(3) Io and
(4) Europa.
(1)
Each moon is its own
unique geological world.
Jupiter’s Rings
Jupiter’s rings were one of the most unexpected
discoveries by Voyager I.
Saturn: The Elegant Planet
Saturn Fast Facts
• Saturn takes almost 30 Earth-years to
make one revolution.
• It is very similar to Jupiter in
composition and atmosphere, but only
half its size.
• The most prominent feature of Saturn
is its system of rings.
Features of Saturn
Saturn’s atmosphere
is very active, with
winds up to 1500 km
per hour.
Saturn has at least 31
moons. Titan is the
largest moon, and is
larger than Mercury.
Saturn has large
“cyclone” storms similar
to Jupiter’s Great Red
Spot, just not as large.
Saturn’s density
is so light that it
could float in a
tub of water!
Saturn’s Rings
All of the Jovian planets
have ring systems.
They all consist of
multiple concentric rings
separated by gaps in
various widths.
Saturn’s rings are very dense and wide, but they
are only about 100 meters from top to bottom.
Uranus: The Sideways Planet
Uranus is unique in that it rotates “on its
side.” Its axis of rotation is lies nearly
parallel with the plane of its orbit.
Uranus, like all Jovian
planets, has a ring system
that is perpendicular to its
axis.
Uranus has at least five moons.
Neptune: The Windy Planet
Winds exceeding 1000 km per hour encircle Neptune,
making it one of the windiest places in the solar system.
Neptune has a layer of white, whispy clouds of
frozen methane about 50 kms above its surface.
It also has at least 13 moons.
Neptune has a
“Great Dark
Spot” similar to
Jupiter’s Great
Red Spot.
Scientists believe
that it is also a
cyclone, about
the size of the
earth.
Pluto: Planet X
Pluto was downgraded to a “dwarf planet”
in 2005. It is still a controversial decision.
Pluto lies at the edge of the Solar
System, more than 40 times
farther from the sun than Earth.
Pluto takes about 248 earth-years to orbit the sun.
Pluto’s orbit is highly eccentric,
and the planet sometimes travels
inside the orbit of Neptune.
Pluto is cold enough to freeze most gases that might be
present. It could be described as a dirty ice ball.