Transcript Comets, Meteors, and Asteroids

Chapter 28
Minor Bodies of the Solar System
Section 1
Earth’s Moon
1
Exploring the Moon

Seven of the planets in our solar system have
natural satellites, or moons.
The Apollo space program sent six spacecraft to
study the moon.
 Scientists were able to gather data about the
moon’s weak gravity and its effect on astronauts,
as well as data about the moon’s surface

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The Lunar Surface


Any feature of the moon is referred to as lunar.
Luna is Latin for “moon”.
The light patches seen on the moon’s surface are
called anorthosites.
 The darker areas are called maria.


Maria are plains of dark, solidified lava which
formed more than 3 billion years ago when lava
slowly filled basins that were created by massive
asteroids.
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Craters, Rilles, and Ridges
The surface of the moon is covered with craters,
rilles, and ridges.
 Most of the craters formed when debris struck the
moon about 4 billion years ago.


Rilles are long, deep channels that run through the
maria. Rilles are thought to be leftover lava
channels from the formation of the maria.

The moon’s surface also has several ridges, which
are long, narrow elevations of rock that rise out of
the surface and criss-cross the maria.
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Regolith

The moon’s surface is very susceptible to
meteorite hits because the moon has no
atmosphere for protection.

Over billions of years, these meteorites crushed
much of the rock on the moon’s surface into a
layer of dust and small fragments called regolith.

The depth of regolith on the moon varies from 1 m
to 6 m.
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Lunar Rocks
Lunar rocks are igneous, and most rocks near the
surface are composed mainly of oxygen and
silicon.
 Rocks from the lunar highlands are light-colored,
coarse-grained anorthosites that contain calcium
and aluminum.
 Rocks from the maria are fine-grained basalts and
contain titanium, magnesium, and iron.
 Breccia is found in both maria and the highlands.
Lunar breccia formed when meteorites

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The Interior of the Moon

The interior of the moon is less dense than the
interior of earth.

Scientists have determined that the moon’s interior
is layered by studying seismic information
collected during moonquakes.

Like, Earth, the moon has three compositional
layers: the crust, the mantle, and the core.
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The Moon’s Crust

The side of the moon that faces Earth is called the
near side, while the side of the moon that faces
away from Earth is called the far side.

The moon’s crust is thicker on side than the other.

The crust on the near side is about 60 km thick.
The crust on the far side is up to 100 km thick.

The difference in thickness was caused by the pull
of Earth’s gravity during the formation of the
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moon.
The Moon’s Mantle and
Core

Beneath the crust is the moon’s mantle. The
mantle is thought to be made of rock that is rich in
silica, magnesium, and iron.

Scientists think that the moon has a small iron
core that has a radius of less than 700 km.

Studies of the core have shown that the moon’s
rotation is not uniform and that the core is neither
completely solid nor completely liquid.
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The Giant Impact Hypothesis

Most scientists agree that the moon formed in
three stages.
The giant impact hypothesis:
#1Impact
#2 The collision ejected chunks of Earth’s mantle
into orbit around Earth.
 #3 The debris eventually clumped together to
form the moon.




This hypothesis explains when moon rocks share
many of the chemical characteristics of Earth’s 10
Formation of the Moon
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Differentiation of the Lunar Interior

Early in its history, the lunar surface was covered
by an ocean of molten rock.

Over time, the densest materials moved toward the
center of the moon and formed a small core.

The least dense materials formed an outer crust.

The other materials settled between the core and
the outer layer to form the moon’s mantle.
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Meteorite Bombardment

When the moon first formed, it was bombarded
with meteorites, creating craters and regolith on
the moon’s surface.

About 3 billion years ago, less material struck the
lunar surface, and few new craters formed.

Craters that have rays formed during the most
recent meteor impacts. During this stage, virtually
all geologic activity stopped on the moon.
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Lava Flows on the Moon
 After
impacts on the moon’s surface formed
deep basins, lava flowed out of cracks, or
fissures, in the lunar crust.
 This
lava flooded the crater basins to form
maria.
 The
presence of maria suggest that fissure
eruptions once characaterized the moon.
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Lava Flows on the Moon

Because of the uneven thickness of the moon’s crust, more
maria formed on the near side of the moon than on the far
side.

Scientist do not yet know how magma formed in the lunar
interior or how magma reached the surface because there is
no evidence of plate tectonics on the moon.

Some scientists think the magma was formed by the large
amount of energy that was produced by the long period of
intense meteorite bombardment. Other scientists think
radioactive decay of materials may have caused magma to
form.
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Chapter 28
Minor Bodies of the Solar System
Section 2
Movement of the Moon
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Movements of the Moon
1. The Earth Moon System
2. Lunar & Solar Eclipses
3. Phases of the Moon
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Lunar Landing Sites
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The Earth-Moon System

Earth and the moon revolve around each other.
Together they form a single system that orbits the
sun.

The balance point of the Earth-moon system is
located within the Earth’s interior, because
Earth’s mass is greater than the moon’s mass.

This balance point is called the barycenter.

The barycenter follows a smooth orbit around the
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sun.
The Earth-Moon System
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The Moon’s Elliptical Orbit

The orbit is an ellipse, the distance between Earth and
the moon varies over a month’s time.

When the moon is farthest from Earth, the moon is at
apogee.

When the moon is closest to Earth, the moon is at
perigee.

The Average distance to the moon is about 384,000
km.
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Moonrise and Moonset

The moon appears to rise and set at Earth’s horizon
because of Earth’s rotation on its axis.

The moon rises and sets 50 minutes later each night.
This happens because of both Earth’s rotation and the
moon’s revolution.

While Earth completes one rotation each day, the
moon also moves in its orbit around Earth.

It takes 1/29 of Earth’s rotation, or about 50 minutes,
for the horizon to catch up to the moon.
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Lunar Rotation
 The
moon’s revolution around Earth and its
rotation on its axis take the same amount of
time.
 Because
the rotation and revolution take the
same amount of time, observers on Earth
always see the same side of the moon.
 The
part of the moon illuminated by sunlight
changes as the moon orbits Earth.
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The sides of the Moon
The “near” side: The side
The “far” side: The
we see from Earth; smooth
with lunar ‘maria’
side we never see from
Earth; highly cratered
with extreme coloration
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changes
Synchronous Rotation:
The moon takes exactly the same amount of time
to orbit Earth as it does to rotate
There is no“dark
side” of the Moon.
 All locations on the
moon experience
about 14 days of
daylight and 14 days
of night.

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ECLIPSES
 One
of the most striking astronomy events
 Happen when one object blocks another
- Moon, Sun, Earth
Two types:
 LUNAR eclipse (common)
 SOLAR eclipse (rare!)
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Eclipse
 Bodies
orbiting the sun cast long shadows
into space.
 An eclipse occurs when one body passes
through the shadow of another.
 Shadows have two parts:
 the inner, cone-shaped part of the
shadow called the umbra
 the outer part of the shadow called the
penumbra.
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Solar and Lunar Eclipses
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Solar Eclipses

During a total solar eclipse, the sun’s light is
completely blocked by the moon. The umbra falls
on the area of Earth that lies directly in line with
the moon and the sun.

Outside the umbra, but within the penumbra,
people see a partial solar eclipse. The penumbra
falls on the area that immediately surrounds
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Effects of Solar Eclipses

The sunlight that is not eclipsed by the moon
shows the normally invisible outer layers of the
sun’s atmosphere.

This causes what is known as the diamond-ring
effect, because the sunlight often glistens like the
diamond on a ring.
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Effects of Solar Eclipses

If the moon is at or near apogee during a solar
eclipse, the moon’s umbra does not reach Earth.
This causes an “annual eclipse” in which a thin
ring of sunlight is visible around the outer edge of
the moon.

The brightness of this ring prevents observers
from seeing the outer layers of the sun’s
atmosphere
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Total Solar Eclipse
- Sun’s corona (thin, outer gases) is visible
- Time to study chromosphere, corona
during eclipse
Why do eclipses not happen at every
FULL and NEW moon (2x month!) ?
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Lunar Eclipses

A lunar eclipse occurs when Earth is positioned
between the moon and the sun and when Earth’s
shadow crosses the lighted half of the moon.

When only part of the moon passes into Earth’s umbra,
a partial lunar eclipse occurs.

When the entire moon passes through Earth’s
penumbra, a penumbral eclipse
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Time-lapse picture of a total lunar eclipse
 Even
during a total Lunar eclipse, sunlight is
bent around the earth and causes the moon to
appear red.
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The orbital planes of Earth/Moon are not exactly aligned
 5 degree difference makes eclipses rare!
• solar eclipses: 2-5 a year (half are total)
• lunar eclipses: 2-3 a year (half are total)
No More than 7 eclipses
Normally there are
can occur in one year.
4 eclipses a year.
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Annular Solar Eclipse

The distance between the
Moon and the Earth
changes slightly during the
Moon’s orbit

When the Moon is farthest
from the Earth (apogee),
then the solar eclipse will
be annular
 the Moon does not
completely cover up the
Sun
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Locations of Solar Eclipses for 1997-2020
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Total Solar Eclipse 2001
Zambia, Africa
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Misconception:
Phases of the Moon are
caused by the shadow of
the Earth on the Moon
Truth: Phases of the Moon
are caused by our changing
view of the illuminated
side of the Moon
• ½ of the Moon is always
illuminated by the Sun
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Phases of the Moon
• caused by its orbital motion around the Earth
• repeat every 29 ½ days
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You can tell the moon phase by
- looking at its face
- observing what time it rises/sets
Full Moon
Rises ~ sunset
Sets ~ sunrise
New Moon
Rises ~ sunrise
Sets ~ sunset
First Quarter Moon
Rises ~ noon
Sets ~ midnight
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Time from New Moon to New
Moon
The moon revolves around Earth in 27.3 days,
however, the period from one new moon to the
next one is 29.5 days.
 In the 27.3 days in which the moon orbits Earth,
the Earth moves along its orbit around the sun.
 The moon must go a little farther to be directly
between Earth and the sun.
 About 2.2 days are needed for the moon to travel
this extra distance.

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Tides on Earth

Bulges in Earth’s oceans, called tidal bulges, form
because the moon’s gravitational pull on Earth
decreases with distance from the moon.

As a result, the ocean on Earth’s near side is pulled
toward the moon with the greatest force.

The solid Earth experiences a lesser force.

Because Earth rotates, tides occur in a regular
rhythm at any given point on Earth’s surface each
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day.
Causes of Tides
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Action of the Moon
The depth of water over each point changes as the
Earth rotates.
 This produces two high and two low waters per day.

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Check Your Knowledge Questions
1.
If you observe the moon to be rising at sunset, what
phase is it?
1. Full
2. First Quarter
3. New
4. Third Quarter
2. If you observe the moon to be rising around midnight,
what phase is it?
1.
Full
2.
First Quarter
3.
New
4.
Third Quarter
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Asteroids, Comets, and Meteoroids
Chapter 28
Section 4
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Asteroids
In addition to the planets and their moons,
our solar system includes millions of
smaller bodies, such as asteroids, comets,
and meteoroids.
The largest of these smaller bodies are
asteroids, which are fragments of rock that
orbit the sun.
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Asteroids
Astronomers have found over 50,000 asteroids.
Millions asteroids may exist in the solar system.
The orbits of asteroids are ellipses.
Most asteroids are located in a region between the
orbits of Mars and Jupiter known as the asteroid
belt.
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Asteroids
Not all asteroids are located in the asteroid belt.
The closest asteroids to the sun are inside the orbit
of Mars.
The Trojan asteroids are concentrated in groups
just ahead of and just behind Jupiter as it orbits the
sun.
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Asteroid Belt
Apollo
Trojans
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Composition of Asteroids
The composition of asteroids is similar to
that of the inner planets.
Asteroids are classified according to their
composition into three main categories.
The first type of asteroid is also the most
common; these asteroids are made mostly
of silicate material.
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Composition of Asteroids
The second type of asteroid is composed of
mostly iron and nickel. These asteroids have
a shiny, metallic appearance, especially on
fresh surfaces.
The third, and rarest, type of asteroid is
made mostly of carbon materials, which
give this type of asteroid a dark color.
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Near-Earth Asteroids
More than a thousand asteroids are called
near-Earth asteroids because their orbits
bring them close to Earth.
Several asteroid detection programs have
begun to track all near-Earth asteroids.
By monitoring these asteroids, scientists
hope to predict and possibly avoid future
collisions.
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Ida - Dactyl
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Gaspra
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Asteroids Elsewhere
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Comets
The most famous comet is Halley’s Comet,
which passes by Earth every 76 years.
It last passed Earth in 1986, and will return
in 2061.
Every 5 to 10 years, a bright comet is
visible from Earth.
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Composition of Comets
A comet has several parts. The core, or nucleus of
a comet is made of rock, metals, and ice.
A spherical cloud of gas and dust, called the coma,
surrounds the nucleus. The coma can extend as far
as 1 million kilometers from the nucleus.
The nucleus and the coma form the head of the
comet.
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Composition of Comets
The most spectacular part of a comet is its tail.
Tails form when sunlight causes the comet’s ice to
change to gas. The solar wind pushes the gas away
from the comet’s head.
The comet’s second tail is made of dust and curves
backward along the comet’s orbit
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Structure of a Comet
Ion Tail
Dust
Tail
Coma
To Sun
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Comet Structure
 Nucleus
 10
km “Dirty Snowball”
 Coma
 Cloud
of evaporated ices and ions
 may be 1,000,000 km in diameter
 Tail
 Always
 Solar
points away from Sun
Wind and Radiation Pressure
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The Oort Cloud
Scientists think that most comets originate
in the Oort cloud.
The Oort cloud surrounds the solar system
and may reach as far as halfway to the
nearest star.
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The Oort Cloud
 In
1950 Jan Oort noticed that

no comet has been observed with an
orbit that indicates that it came from
interstellar space,

there is no preferential direction from
which comets come.
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The Oort Cloud
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The Oort Cloud
Bodies within the Oort cloud circle the sun so
slowly that they take a few million years to
complete one orbit.
But, the gravity of a star that passes near the solar
system may cause a comet to fall into a more
elliptical orbit around the sun.
If a comet takes more than 200 years to complete
one orbit of the sun, the comet is called a longperiod comet.
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The Kuiper Belt
Advances in technology have allowed
scientists to observe many small objects
beyond the orbit of Neptune.
Most of these objects are from the Kuiper
belt and are called Kuiper-belt objects.
Pluto is located in the Kuiper belt during
much of its orbit.
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Short-Period Comets
Comets called short-period comets take less
than 200 years to complete one orbit around
the sun.
Astronomers have discovered that most
short-period comets come from the Kuiper
belt.
Halley’s comet, which has a period of 76
years, is a short-period comet.
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Comet Halley
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Bayeaux Tapestry
Norman Invasion of 1066
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Comet Halley 1910
•Pope Callixtus III
excommunicated
Halley's Comet in 1456
•In 1910, charlatans sold
"comet pills"
Orbit
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Comet of 1577
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Hyakutake
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Hale-Bopp
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Meteoroids
Most meteoroids have a diameter of less than 1
mm. Scientists think that most meteoroids have a
diameter of less than 1 mm.
Scientists think that most meteoroids are piece of
matter that become detached from passing comets.
Large meteoroids, which are more than 1 cm in
diameter, are probably the result of collisions
between asteroids.
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Meteoroids
When a meteoroid enters Earth’s atmosphere,
friction heats and burn them up.
As the meteoroid burns up, it produces a
bright streak of light called a meteor.
Meteors are often called shooting stars.
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The 1833 storm
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The 1966 storm
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1997 Leonids from Orbit
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What causes meteor showers?
1.
2.
3.
4.
Lots of falling stars
Clouds
Debris left in the path of a comet
Solar wind particles
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The Cause of Meteor Showers
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Two Showers for Halley
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Spot Question
What is the difference between a meteor
and a meteoroid?
A meteoroid is a rocky body that travels
through space. When a meteoroid enters
Earth’s atmosphere and begins to burn up,
the meteoroid becomes a meteor. Location,
Location, Location!!!!!!
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Meteorites
Meteoroids that do not burn up, but fall to
Earth’s surface, are called meteorites.
Most meteorites are small and don’t cause
much damage, but occasionally large
meteorites strike Earth’s surface with the
force of a large bomb.
There are three types of meteorites: stony,
iron, and stony-iron.
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Meteorites
Stony meteorites are similar in composition
to rock on Earth.
Iron meteorites have a distinctive metallic
appearance.
Stony-iron meteorites contain both iron and
stone.
 Stony-iron meteorites are rare.
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Sporadic Meteors
Irons
Stony-Irons
Carbonaceous
Chondrite
Chondrites
Achondrite
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Meteorites
Astronomers think that almost all
meteorites come from collisions between
asteroids.
The oldest meteoroids may be 100 million
years older than Earth.
Meteorites may provide information about
how the early solar system formed.
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Barringer’s Crater
An iron meteorite 100 feet across and 70,000 tons
slamed into the Earth at about 43,000mph in the
Arizona desert near Flagstaff 40,000 years ago.
Barringer Crater is 4,100 feet wide and 571 feet deep.
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Other Impact Craters
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Tunguska, Siberia
 June
30, 1908- Space object hit a sparsely
populated and heavily forested area.
 Explosion heard over a radius of 500 miles,
covering an area of 500,000 square miles
 Pressure wave was recorded passing
England 5 hours and 15 minutes after
impact
 Blast equivalent to a 20-megaton H-bomb
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Tunguska, 1908
Nearly 1000 square miles of forest was
flattened due to an air burst (meteor
exploded before hitting the ground)
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K-T Boundary
 In
1980, Walter Alvarez and a team of
scientist discovered a thin layer of clay in
Italy that contained Iridium and dated back
64,980,000 years ago.
 Iridium is not naturally occurring on Earth,
but is found in space.
 The Alvarez Team named this layer of clay
the K-T Boundary
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K-T Boundary
 The
K-T Boundary is evidence that a
asteroid hit Earth and causes a ELE
(Extension Level Event) eliminating 70% of
life including the dinosaurs.
 The boundary marks different time periods
of dinosaurs and mammals. End of
Cretaceous Period and Beginning of
Tertiary Period.
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Chicxulub Crater
 The
problem the Alvarex team had with this
hypothesis was there was no impact site.
 In 1990,a crater 110 miles across in the
Yucatan Peninsula (off the coast of Mexico)
was identified as the impact site. The crater
was named Chicxulub “The Devils Tail”
and was caused by an asteroid
approximately 6 miles long.
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Chicxulub Evidence
 Besides
the impact crater and iridium
scientist have also found impact droplet and
shocked quartz (crystalline structure of
quartz is deformed) to support their theory.
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Walter Alvarez and
Son at the K-T
Boundary in Italy
K-T Boundary.
Colorado
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What else can impacts cause?
 1.
Tsunami
 2. Molten Rock
 3. Debris Throw-up causing impact winters
and difficulty breathing
 4. Fire
 5. Land shock
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Odds
Small chunks of matter hit and orbit Earth
everyday. These object are called NEO’s – Near
Earth Objects.
 Only a small number of scientists jobs are to
watch the sky for NEO’s
 1/1Million odds of being killed by an ELE
asteroid
 1/100 Million odds of being killed by a small
impact

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How Much Damage?
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Why is the study of comets, asteroids,
and meteors important?
1.
2.
3.
4.
Predicting the future
Original solar nebula material
Useful in refining mass of solar system
It will be on the test
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 And
God said, “fire not flood next
time.”
- Lyrics from Well, Well, Well by the group Peter, Paul,
and Mary
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End of Section
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