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Unit 2

Chapter 5

Solar System

An Inventory of the Solar System

Early astronomers knew: Sun, Moon, Stars, Mercury, Venus, Mars, Jupiter, Saturn, comets, and
meteors

Now we know: Solar system has one star, eight planets (added Uranus, and Neptune), 135+
moons, asteroids, comets, and meteoroids.

Pluto was added as a Planet then reduced to a Dwarf Planet


Planetary Properties

Orbital period can be observed

Distance from Sun known by Kepler’s laws

Radius known from angular size

Masses from Kepler’s 3
rd

Law
as modified by Newton’

Rotation period from observations

Density can be calculated knowing radius and mass


Comparison of the Terrestrial Family of Planets to the Jovian Family of Planets

Differences between the terrestrial planets

Atmospheres and surface
conditions are very dissimilar

Only Earth has oxygen in atmosphere and liquid water on surface

Earth and Mars rotate at about the same rate;

Venus and Mercury are much slower, and

Venus rotates in the opposite direction

Earth and Mars have moons; Mercury

and Venus don’t




Earth, Mars and Mercury have magnetic fields; Venus does not.

Interplanetary Debris

A
steroids and meteoroids are rocky; asteroids are bigger

Asteroid Eros
’ the one visited by a spacecraft,

is 34 km long

Comets are icy, with some rocky p
arts.

One theory of Solar system formation


Cloud of gas and dust contracts due to gravity.

Conserv
ation of Angular Momentum causes
it spins faster and faster as it contracts

Condensation theory:

Interstellar dust grains help cool the cloud, and act as co
ndensation nuclei to produce
flakes

Local temperature in the condensing cloud determines where various materials
condense


Early Spacecraft Exploration of the Solar System

Soviet
Venera

probes landed on Venus from 1970

1978

Pioneer

and
Voyager

flew through

the outer solar system.




Chapter 6

Earth

The interior of the Earth has been determined by studying the transmittal and reflection of Seismic
Waves within the Earth.

Seismic waves are sound waves generated by earthquakes. They are compression waves and sinesoidal
waves. They reflect from and transmit through layer interfaces with the Earth.


The Earth has a solid iron inner core, a liquid iron outer core, a liquid roc
ky mantle and a solid rocky
crust

Can use the pattern of reflections made during earthquakes to deduce interior structure of Earth


Crust

The crust of the Earth is divided into several plates that move with respect to each other. The
movement is driven b
y convection currents in the mantle. Plate movement results in
earthquakes and volcanism

Interactions between the plates are:



transform, sliding against each other;



divergence, separating;



convergence, coming together.

When plates slide against each oth
er cracks (faults) occur and earthquakes happen.

The twisting Pacific plate has produced many earthquake zones and many active volcanoes.

At divergent boundaries new crust is made.

At convergent boundaries crust is lost by subduction (sliding under) and cr
umpling (mountain
building)


The Earth’s magnetic field



appears to be generated by electric currents circulating the liquid iron core.



The trapped hot charged particles in the Van Allan belts are shunted toward the magnetic poles
where they interact with

the air molecules. The particles are cooled by the air which glows as
auroras.


The Earth’s Biosphere,

Oceans and Atmosphere, come from hydrogen rich gasses trapped inside the Earth during
creation.

By far the most abundant

of the trapped gasses are methane, ammonia, and water.


The Earth is the only planet where conditions are right for liquid water to exist on the surface.

Trapped gasses Outgassing

Water

Nitrogen

Carbon Dioxide

Plant Life

Oxygen

The Earth’s Atmosphere

T
roposphere is where convection takes place


responsible for weather


The blue curve shows the temperature at each altitude

Convection depends on warming of ground by the Sun


Ionosphere is ionized by solar radiation, and is good conductor

Reflects radio
waves in the AM range, but is transparent to FM and TV

Ozone layer is between ionosphere and mesosphere; absorbs ultraviolet radiation


The Human Element

More Humans,

Industrial Revo
-
lution

Global Warming (?)


Chapter 7

The Moon

The seismograph placed on
the Moon by the Astronauts of the Apollo Program


Does the moon rotate?

What if the Moon did not rotate?

Synchronous Rotation

One rotation for one revolution


Lunar Phases as described by Aristotle

We only see the lighted portion of the Moon


Craters on t
he Moon and the Earth


Impact


Maria, Basins, Rays


Impact and volcanism


Rills and Domes


Volcanism

Craters, Maria and Basins are all due to meteorite impact

Moon has large dark flat areas, due to impact and lava flow, called maria or basins (early
observ
ers thought they were oceans or seas)


Far side of Moon has some large craters, but no large maria. The reason for this difference is still not
fully understood.


Meteoroid strikes Moon, ejecting material; explosion ejects more material; leaving crater, lips (rim) and
ejecta


Regolith
:

The surface of the moon is heavily cratered. One of the results of the infalling bodies is to
pulverize the surface, thus creating
a layer debris, much of it is very fine dust. The surfaced is
layered with debris on top of pulverized rock.


Most lunar craters date to at least 3.9 billion years ago; much less bombardment since then.


Craters are typically about 10 times as wide as the

meteoroid creating them, and twice as deep as they
are wide.


Early Intense Bombardment

Moon is still being bombarded by very small objects called “micrometeorites” which trends to round the
edges of craters and leave a layer of dust
.


Meteorites also hit

Earth; i.e. Meteor

C
rater in Arizona


The great “lakes “ of liquid rock that filled the large craters are greatest evidence of vulcanism on the
moon. Vulcanism ceased when the moon cooled.

This is an edge of a mare. The soo
th appearance is due to the lava

that flowed up through cracks ,
smoothed out then cooled.


Hadley Rill seems to be an extended lava tube whose roof has fallen in. There are other caved in lava
tubes but they are much shorter


Moon’s density is relatively low, and it has no magnetic fiel
d


cannot have sizeable iron/nickel core.
Due to cooling over time the crust has thickened.


Air molecules have high speeds due to thermal motion. If the average molecular speed is well below the
escape velocity, few molecules will escape.

Escape becomes
more probable:




for lighter molecules (higher speed for same kinetic energy)




at higher temperatures




for smaller planets (escape speed is less)


Early theories of the origin of the Moon


The currant, post Apollo, theory is the Collision Ejection Theory. Two large planetismals collide. Their
crusts splash, their interiors merge. The merged interiors become the Earth. The splashed crustal
material becomes the Moon

This theory accounts for
the difference in density of the Moon and Earth, the reason for the high
percentage of iron in the Earth, and the strange orbital placement.

.


Chapter 8

The Planet Mercury


Elongation of Mercury


The eccentricity of Mercury’s orbit allows to see it fathe
r from the sun sometimes.

Mercury as Seen from Earth



Synchronous rotation

1:1

Our moon

All the large moons



Mercury’s rotation 3:2

3 rotations to 2 revolutions


Comparison of Earth’s interior to that of Mercury

Mercury’s Magnetosphere


Mariner 10
Trajectory

Composite of the Mariner views of Mercury

Craters and Planes (?)

Scarp (Cliff)

Edge of Caloris Basin


The spacecraft MESSENGER in orbit around Mercury. Notice the shade designed to protect the
MESSENGER from the brilliant sunshine.


From its po
lar orbit MESSENGER is able to see the entire surface

Messenger may have found extinct volcanos

Some unusual features to be studied

Some features become more evident at different lighting

Some very strange terrain


Mercury & Dr. Einstein



Curvature of light

around a large mass



Orbital Precession


Chapter 9

Beautiful Venus

Atmosphere on Venus and on Earth

Gasses from a Volcano
on Earth

Evidence of

Eruption on

Venus


Greenhouse Effect

Greenhouse Effect on Venus


Venera

Mission

Venera Lander

Visible images from Venus by Venera


Magellan Spacecrafrt



Map of Venus by Magellan spacecraft



More of Venus’s Sphere by Magellan



Computer reconstruction

o

O
ne Face of Venus

o

A volcanic crater

o

Craters and lava flow

o

A large volcano

o

A lava field and an impact
crater

o

These are unusual ‘pancake’ lava flows

o

Lava fields around several craters

o

Lava field






Chapter 10

The Planet Mars

Early observers did not have photography and had to draw what they saw.


In the years from about 1890 to about 1910 Percival Lowell became enamored with the observations of
Schiapereli. Canali for him were canals. He believed in canals and the intelligent life forms needed to dig
them. He spent many years talking and writing
about them.


Mars’ Properties

Dist from Sun=1.5+ or app. 1.6 AU (T
-
B)

Year = 1.88 Earth years

Sol (Mars day) = 24h 37 m

Axis inclination = 25+ deg

Dia = .533 Earth dia

Surface gravity = .38 Earth

Surface Temp =
-
140 deg C to 20 deg C


Comparison of the At
mospheres


of the Terrestrial Planets


Earth


Venus


Mars

N
2


0.79


2


3 x 10
-
4


O
2


0.20


< 0.001


0
-
7


Ar

0.01


0.005


2 x 10
-
4


CO
2


0.0003


64


0.009

H
2
O

~ 0.02


~ 0.01


~10
-
6


Total

1.00


90


0.01


The interior of Mars has not been studied by seismic waves. Surface clues indicate that the interior as
shown is likely correct. Over time the interior has cooled and vulcanism has ceased.


The surface of Mars has been imaged and mapped at least as thorou
ghly as the Earth.



No liquid water has been found although there is much evidence that there has been standing
and flowing water in the past.



The Southern Hemisphere is somewhat higher in elevation and
covered with craters appearing

mu
ch like The Moon.



The lower Northern Hemisphere is much more earthlike. It has giant volcanoes and canyons.



A
topographical map of the Tharsis Rise shows giant volcanoes, a giant canyon, apparent dry
river beds and a dry ocean



If Mount Olympus a

giant volcano
,

were on Ear
th is would stand three times higher than Mount
Everest and would completely cover the State of Utah



An image of a dry watershed



An image of a dry river bed



A topographic map of the mouth of a dry river entering a dry ocean



A canyon land region called Sout
h Candor



A panoramic view of a rocky rolling valley


The North Polar Cap seems to have water ice with much dry ice covering it. There is much information
in the apparent layers that have accumulated over eons.


Today



Cold



Dry

Anciently



Warm



Wet


Robots to

Mars



From the Mariner Probes in the early ‘60s to the extremely successful
Curiosity

Lander
this year,

mankind has sent
a
variety of robot orbiters and landers to prepare the way for a future manned
mission to the exotic Red Planet.



Viking Program

o

Two Id
entical Systems

o

Orbiter

o

Lander

o

Mi
d 70’s

o

Search for Living Life

o

Chemical not biological results

o

Red color is iron oxide

o

A view from the Viking 2 Lander in summer and winter. The occasional frost layer only
lasts until Sun up.




The Mars Global Surveyor took

images in visible and infrared of the entire planet every day for
one full Mars year. Among its discoveries was this of recent gullies



One of the trickiest parts of the Mars Exploration is actually getting the rovers to Mars in
working condition.Imagine
trying to drop a sophisticated robot about 11
-
12 stories without
breaking it (or even dropping an ordinary DVD player)



When the Pathfinder lander and the Sojourner rover arrived in 1997 they began the era of
faster, cheaper spacecraft. Sojourner can be see
n examining the rock “Yogi”



The next generation Rovers were two, called the Spirit and Opportunity.

o

Spirit
’s landing place was similar to the
Viking
s’; this is a 360° panoramic view

o

Spirit View west from the Columbia Hills

o

This is a view from Opportunity

down into Victoria Crater. It spent nearly a full Earth
year finding the best way down into the crater and this is it.

o

Opportunity has now left Victoria Crater in search of another crater to explore.



Here we see the robotic arm at work. It cleans the
rock, examines it then analyses it for
elements.

o

This is the Instrument complex w
ith

t
he RAT, imager and spectrograph

D
iscoveries



Layering as if by water deposit



Spherical pebbles such as in a stream



Rust (color) same as the red iron oxide as in Southern
Utah

Adventures




Stuck in sand dune



Covered by dust in a storm



Uncovered by a whirl wind



Lived through a long Mars winter



Are still going strong (four times as long as expected


The Pheonix scooped up icy dirt that gave off liquid water when warmed.


Each
Rover has become more become bigger and more complex as we have learned how to build them
and use them

Mars Pathfinder (Success)

Mars Global Surveyor (Success)

Actively taking pictures and gathering data

Mars Polar Lander (Failed)

Mars Atmosphere
Observer (Failed)

2001 Mars Odyssey

-
arrived Oct 24. 2001

-
gathering data today

Landers (Future)


-
biology and geology Laboratory

-
to gather rocks and return them to Earth


Moons of Mars

Phobos (Fear) is the large
r
of the two.

They are both tin
y and badly scarred by impacts but Phobos looks like it was nearly shattered.

The Chinese

are planning to send a robot to pick up dirt and rock samples from Diemos (Terror)
to return them to Earth