Earth
Science, 10th edition
Chapter
21: Touring Our Solar System
I. Overview of the solar
system
A. Solar system
includes
1. Sun
2. Nine planets
and their satellites
3. Asteroids
4. Comets
5. Meteoroids
B. A planet's orbit
lies in an orbital plane
1. Similar to a
flat sheet of paper
2. The orbital
planes of the planets are inclined
a. Planes of
seven planets lie within 3 degrees of the Sun's equator
b. Mercury's
is inclined 7 degrees
c. Pluto's
is inclined 17 degrees
C. Two groups of
planets occur in the solar system
1. Terrestrial
(Earth-like) planets
a. Mercury
through Mars
b. Small,
dense, rocky
c. Low
escape velocities
2. Jovian
(Jupiter-like) planets
a. Jupiter
through
b. Large,
low density, gaseous
c. Massive
d. Thick
atmospheres composed of
1.
Hydrogen
2.
Helium
3.
Methane
4.
Ammonia
e. High
escape velocities
3. Pluto not
included in either group
D. Planets are composed
of
1. Gases
a. Hydrogen
b. Helium
2. Rocks
a. Silicate
minerals
b. Metallic
iron
3. Ices
a. Ammonia
(NH3)
b. Methane
(CH4)
c. Carbon
dioxide (CO2)
d. Water (H2O)
II. Evolution of the planets
(see textbook Introduction)
A. Nebular hypothesis
1. Planets formed
about 5 billion years ago
2. Solar system
condensed from a gaseous nebula
B. As the planets
formed, the materials that compose them separated
1. Dense metallic
elements (iron and nickel) sank toward their centers
2. Lighter
elements (silicate minerals, oxygen, hydrogen)
migrated toward their surfaces
3. Process called
chemical differentiation
C. Due to their surface
gravities, Venus and Earth retained atmospheric gases
D. Due to frigid
temperatures, the Jovian planets contain a high percentage of ices
III. Earth's Moon
A. General
characteristics
1. Diameter of
3475 kilometers (2150 miles) is unusually large compared to its parent planet
2. Density
a. 3.3 times
that of water
b. Comparable to Earth's crustal rocks
c. Perhaps
the Moon has a small iron core
3. Gravitational
attraction is one-sixth of Earth's
4. No atmosphere
5. Tectonics no
longer active
6. Surface is
bombarded by micrometeorites from space which gradually makes the
landscape smooth
B. Lunar surface
1. Two types of
terrain
a. Maria
(singular, mare), Latin for "sea"
1. Dark
regions
2.
Fairly smooth lowlands
3.
Originated from asteroid impacts and lava flooding the surface
b.
1.
Bright, densely cratered regions
2. Make
up most of the Moon
3. Make
up all of the "back" side of the Moon
4. Older
than maria
2. Craters
a. Most
obvious features of the lunar surface
b. Most are
produced by an impact from a meteoroid that produces
1.
Ejecta
2.
Occasional rays (associated with younger craters)
3. Lunar regolith
a. Covers
all lunar terrains
b. Gray,
unconsolidated debris
c. Composed
of
1.
Igneous rocks
2.
Breccia
3. Glass
beads
4. Fine
lunar dust
d.
"Soil-like" layer
e. Produced
by meteoric bombardment
C. Lunar History
1. Hypothesis
suggests that a giant asteroid collided with Earth to produce the Moon 2.
One method used to work out lunar history is to observe crater density
a. Older
areas have a higher density
b. Younger
areas are still smooth
3. Moon evolved
in three phases
a. Original
crust (highlands)
1. As
Moon formed, its outer shell melted, cooled, solidified, and became the
highlands
2. About
4.5 billion years old
b. Formation
of maria basins
1.
Younger than highlands
2. Between 3.2 and 3.8 billion years old
c. Formation
of rayed craters
1.
Material ejected from craters is still visible
2. e.g., Copernicus (a rayed crater)
IV. Planets: a brief tour
A. Mercury
1. Innermost
planet
2. Second
smallest planet
3. No atmosphere
4. Cratered
highlands
5. Vast, smooth
terrains
6. Very dense
7. Revolves
quickly
8. Rotates slowly
a. Cold
nights (-280°F)
b. Hot days
(800°F)
B. Venus
1. Second to the
Moon in brilliance
2. Similar to
Earth in
a. Size
b. Density
c. Location
in the solar system
3. Shrouded in
thick clouds
a. Impenetrable by visible light
b.
Atmosphere is 97% carbon dioxide
c. Surface
atmospheric pressure is 90 times that of Earth's
4. Surface
a. Mapped by
radar
b. Features
1. 80%
of surface is subdued plains that are mantled by volcanic flows
2. Low
density of impact craters
3.
Tectonic deformation must have been active during the recent geologic past
4.
Thousands of volcanic structures
C. Mars
1. Called the
"Red Planet"
2. Atmosphere
a. 1% as dense as Earth's
b. Primarily
carbon dioxide
c. Cold
polar temperatures (-193°F)
d. Polar
caps of water ice, covered by a thin layer of frozen carbon dioxide
e. Extensive
dust storms with winds up to 270 kilometers (170 miles) per hour
3. Surface
a. Numerous
large volcanoes – largest is Mons Olympus
b.
Less-abundant impact craters
c.
Tectonically dead
d. Several
canyons
1. Some
larger than Earth’s
2.
Valles Marineras – the largest canyon
a.
Almost 5000 km long
b.
Formed from huge faults
e.
"Stream drainage" patterns
1. Found
in some valleys
2. No
bodies of surface water on the planet
3.
Possible origins
a.
Past rainfall
b.
Surface material collapses as the subsurface ice melts
4. Moons
a. Two moons
1.
Phobos
2.
Deimos
b. Captured
asteroids
D. Jupiter
1. Largest planet
2. Very massive
a. 2.5 more
massive than combined mass of the planets, satellites, and asteroids
b. If it had
been ten times larger, it would have been a small star
3. Rapid rotation
a. Slightly
less than 10 hours
b. Slightly
bulged equatorial region
4. Banded
appearance
a.
Multicolored
b. Bands are
aligned parallel to Jupiter's equator
c. Generated
by wind systems
5. Great Red Spot
a. In planet's southern hemisphere
b.
Counterclockwise rotating cyclonic storm
6. Structure
a. Surface
thought to be a gigantic ocean of liquid hydrogen
b. Halfway
into the interior, pressure causes liquid hydrogen to turn into liquid
metallic hydrogen
c. Rocky and
metallic material probably exists in a central core
7. Moons
a. At least
28 moons
b. Four
largest moons
1.
Discovered by Galileo
2.
Called Galilean satellites
3. Each
has its own character
a.
Callisto
1.
Outermost Galilean moon
2.
Densely cratered
b.
Europa
1.
Smallest Galilean moon
2.
Icy surface
3.
Many linear surface features
c.
Ganymede
1.
Largest Jovian satellite
2.
Diverse terrains
3.
Surface has numerous parallel grooves
d.
Io
1.
Innermost Galilean moon
2.
Volcanically active (heat source could be from tidal energy)
3.
Sulfurous
8. Ring system
E. Saturn
1. Similar to
Jupiter in its
a.
Atmosphere
b.
Composition
c. Internal
structure
2. Rings
a. Most
prominent feature
b.
Discovered by Galileo in 1610
c. Complex
d. Composed
of small particles (moonlets) that orbit the planet
1. Most
rings fall into one of two categories based on particle density
a.
Main rings contain particles from a few centimeters to several meters in
diameter
b.
Faintest rings are composed of very fine (smoke-size) particles
2.
Thought to be debris ejected from moons
e. Origin is
still being debated
3. Other features
a. Dynamic
atmosphere
b. Large
cyclonic storms similar to Jupiter's Great Red Spot
c. Thirty
named moons
d. Titan –
the largest Saturnian moon
1.
Second largest moon (after Jupiter's Ganymede) in the solar system
2. Has a
substantial atmosphere
F. Uranus
1. Uranus and
Neptune are nearly twins
2. Rotates
"on its side"
3. Rings
4. Large moons
have varied terrains
G. Neptune
1. Dynamic
atmosphere
a. One of
the windiest places in the solar system
b. Great
Dark Spot
c. White
cirrus-like clouds above the main cloud deck
2. Eight
satellites
3. Triton –
largest
a. Orbit is
opposite the direction that all the planet's travel
b. Lowest
surface temperature in the solar system (-391°F)
c.
Atmosphere of mostly nitrogen with a little methane
d.
Volcanic-like activity
e. Composed
largely of water ice, covered with layers of solid nitrogen and methane
H. Pluto
1. Not visible
with the unaided eye
2. Discovered in
1930
3. Highly
elongated orbit causes it to occasionally travel inside the orbit of
where it resided
from 1979 thru February 1999
4. Moon (Charon)
discovered in 1978
5. Average temperature is -210°C
V. Minor members of the
solar system
A. Asteroids
1. Most lie
between Mars and Jupiter
2. Small bodies –
largest (Ceres) is about 620 miles in diameter
3. Some have very
eccentric orbits
4. Many of the
recent impacts on the Moon and Earth were collisions with asteroids
5. Irregular
shapes
6. Origin is
uncertain
B. Comets
1. Often compared
to large, "dirty snowballs"
2. Composition
a. Frozen
gases
b. Rocky and
metallic materials
3. Frozen gases vaporize when near the Sun
a. Produces
a glowing head called the coma
b. Some may
develop a tail that points away from Sun due to
1.
Radiation pressure and the
2. Solar
wind
4. Origin
a. Not well
known
b. Form at
great distance from the Sun
5. Most famous
short-period comet is Halley's comet
a. 76 year orbital period
b.
Potato-shaped nucleus (16 km by 8 km)
C. Meteoroids
1. Called meteors
when they enter Earth's atmosphere
2. A meteor
shower occurs when Earth encounters a swarm of meteoroids associated
with a comet's path
3. Meteoroids are
referred to as meteorites when they are found on Earth
a. Types of
meteorites classified by their composition
1. Irons
a.
Mostly iron
b. 5-20% nickel
2. Stony
a.
Silicate minerals with
b.
Inclusions of other minerals
3.
Stony-irons – mixtures
4.
Carbonaceous chondrites
a.
Rare
b.
Composition
1.
Simple amino acids
2.
Other organic material
b. May give
an idea as to the composition of Earth's core
c. Give an
idea as to the age of the solar system