Download The Inner Planets

The Inner Planets
2012
Tycho Brahe


(1546-1601CE) A
Danish astronomer
who was not happy
with the accuracy of
the astronomical
observations of his and
earlier times.
Created his own
instruments and made
very detailed
observations of the
heavens for over 20
years.
Johannes Kepler (15711630)


German
mathematician who
used Brahe’s data
to compute the
actual orbit of the
planets.
He discovered that
the planets do not
orbit in circles, but
in ellipses.
Kepler’s Laws


Kepler’s three laws
enabled
astronomer’s to
figure out the orbits
of the planets.
But while he could
now predict where
a planet would be
on a given day, he
had no idea what
made them move in
almost circular
paths.
Sir Isaac Newton (16431727)
Famous for his three laws




One of the greatest
scientists in history.

Studied light and
optics, astronomy,
motion, thermal
dynamics, and many
other things.
When he couldn’t find 
mathematics powerful
enough to solve his
gravity and planetary
orbit problems, he

created his
mathematics, which we
call calculus today.
of motion and the Law of
Universal Gravitation.
Newtonian physics is
used today to send the
shuttle into orbit, space
probes to the stars, and
the Apollo astronauts to
the moon.
Was the first to show
how objects could be put
into orbit around our
planet.
“If I have seen further
than others, it is by
standing upon the
shoulders of giants.”
Inertia


Inertia is the
property of matter
to resist any change
in motion.
An object at rest
will remain at rest,
while an object in
motion will remain
in motion in a
straight line at a
constant speed until
acted on by an
outside force.
Gravity



Gravity is the force
of attraction
between any two
objects with mass.
The more mass, the
more gravity.
The further apart
the two objects are,
the less gravity.
Newton’s Law of Gravity




Newton realized that the
moon should go in a
straight line forever and
ever.
But the force of gravity
kept pulling it towards
the Earth.
The moon is going fast
enough that it keeps
curving around the Earth.
It is constantly falling
towards the Earth.
Newton and Kepler


Newton’s combined
Kepler’s Third Law with
his Law of Gravity.
Now he could figure
out the masses of the
other planets if he
knew how far they
were from the sun and
the time it takes them
to make one orbit.
Solar System




There are at least eleven planets (or planet-like
objects)in our solar system.
Mercury is 58,000,000-km from the sun.
Pluto is 5,913,000,000-km from the sun.
These numbers are hard to use!
Astronomical Units



We will use AU’s to
measure distances
in the solar system.
The Earth is about
150,000,000-km
(93,000,000 miles)
on average from
the sun.
So we will call this
distance 1 AU.
Planetary Distances









Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
0.4 AU
0.7 AU
1.0 AU
1.5 AU
5.0 AU
10.0 AU
19.0 AU
30.0 AU
39.0 AU




Light travels through
space at 300,000-km/s.
So it takes about 8
minutes for light from
the sun to travel 1 AU
and reach us.
How long would it take
light from the sun to
reach Pluto?
39 x 8 = 312 minutes,
or 5.2 hours!
Planetary Zones




First Zone: Contains the
rocky terrestrial planets
Mercury to Mars.
Asteroid belt divides the
first and second zones.
Second Zone: Contains
the gas giants Jupiter
through Neptune.
Third Zone: Goes from
the orbit of Neptune out
to 50 AU. Includes Pluto
and the “ice dwarfs” in
the Kuiper Belt.
The Inner Planets



Inner planets are
rocky.
Inner planets are
small.
Called terrestrial
from the Latin word
terra, which means
Earth.
Mercury

Roman name for
the Greek
messenger god. He
wore winged
sandals so he could
fly. Since Mercury
the planet is the
fastest of all the
planets this is
appropriate.
Mercury Data






Closest to the sun.
Temperature ranges from
427°C in daylight to 173°C at night. (most
extreme range in solar
system)
Rotates slowly, in two
Mercury years three
Mercury days will have
passed.
Essentially no
atmosphere.
Surface similar to the
moon, with craters and
smooth plains.
One third the size of the
Earth.
Mercury Facts





Diameter: one third the size of Earth
Distance: 0.4 AU
Atmosphere: no atmosphere worth
mentioning
Features: Craters with smooth plains,
similar to our Moon, and most extreme
temperature range in solar system
Life: no life because of lack of atmosphere
and extreme temperature range
Venus

Named for the
Roman goddess of
love and beauty.
Originally the Greek
goddess Aphrodite.
Venus Temperature



Almost same size
as the Earth.
Hottest surface in
our solar system.
The average
daytime surface
temperature is
464°C, compared
to the Earth’s 15°C.
This is hot enough
to melt lead.
Venus Atmosphere






Seen from Earth, Venus is
completely cloud covered.
Venus has an very thick
atmosphere, about 96% CO2,
and 4 % N2.
The clouds are mainly sulfuric
acid.
The atmospheric pressure is 92
atmosphere’s, compared to the
one atmosphere we experience
on Earth.
This is the pressure you would
feel if you were under 915
meters of water!
Crushing Pressure!
Greenhouse Effect





Venus is the classic example
of the “runaway greenhouse
effect.”
Water on Earth helped tie up
much of the CO2 in rocks.
Life also stored CO2 in plants
and shells of animals.
Venus was probably too
warm to have much water in
the liquid state, so the water
vapor added to the
greenhouse effect.
As the rocks got hotter, they
released their CO2 into the air
also.
So the greenhouse effect got
worse and worse.
Venus Motions


Since Venus takes 7.5
Earth months to
revolve around the sun
and 8 months to rotate
once on its axis, a day
on Venus is longer
than its year.
Venus also rotates east
to west, the only
planet to do so. This
retrograde rotation
(backward) was
probably caused by
Venus being struck by
a large object early in
its history.
Venus Surface



Since we can’t see through the clouds on Venus, we use
radar to scan the surface.
Venus has rocks, mountains, craters, and strange dome
shape landforms not found on other planets.
Like Earth without the water!
Venus Explorations


About 20 spacecraft have visited Venus,
with more either on the way or planned.
Some have even landed on the surface and
sent back pictures for a short while.
The Evening Star




When in the west at
sunset, Venus will be the
brightest object in the
sky.
This is because Venus
has the highest albedo
(0.76) of all the planets.
Albedo is the percent of
light reflected by an
object.
Our moon has an albedo
of 0.07, so it reflects very
little of the light that
strikes it.
Also called the morning
star when it is in the east.
Venus Facts





Diameter: 0.9 Earth
Distance: 0.7 AU
Atmosphere: 96% carbon dioxide at
almost 100 atmospheres. Runaway
greenhouse effect.
Features: hottest surface in solar system.
Retrograde rotation. Evening/Morning Star
Life: Very doubtful, the pressure and
temperatures are too high. Sulfuric acid
in atmosphere does not help either.
Earth Facts





Diameter: 1 earth
Distance: 1 AU
Atmosphere: 78% Nitrogen, 21%
Oxygen at 1 atmosphere
Features: water world, looks like a
blue marble from space, moderate
temperature and pressures
Life: teeming with life. Planet is “just
right” for life as we know it.
Mars



Mars is the Latin
name for Ares, the
Greek god of war.
Iron oxide in its soil
gives Mars a red
appearance.
Hence the Red
Planet!
Mars
Atmosphere




Mars has an atmosphere
that is mainly carbon
dioxide.
It is very thin, only 0.01
atmosphere’s at the
surface.
Mars even has clouds,
but they are thin also.
The winds can create
dust storms that cover
much of the planet and
last for months.
Mars Volcanoes




Mars surface has a
wide variety of
landscapes.
Olympus Mons is the
largest volcano in our
solar system. Its base
would cover the state
of Colorado.
It is three times taller
than Mt. Everest.
There are many other
volcanoes on Mars, but
none seem to be active
at this time.
Volcano Comparision

Heights of Mt. Everest on the Earth, Maxwell
Montes on Venus and Olympus Mons. (The
horizontal scale has been drastically squashed.)
Mars
Canyons

Valles Marineris is
an enormous
canyon on the
equator of Mars. It
is over 4000-km
long. This would
reach from Los
Angles to Chicago!
Mars Landscape


Mars seems to have
dried river and lake
beds, deltas, and other
features that make
scientists think Mars
had abundant water
early in its history.
If there was water it is
possible that life could
have existed on Mars,
and still might.
Ice Caps


The north and
south poles of
Mars are
covered by ice
caps composed
of frozen carbon
dioxide and
water.
They wax and
wane with the
seasons.
Mars Data



Mars is about half the
size of the Earth.
A 100 pound sixth grader
would weigh 39 pounds
on Mars.
It is very cold on Mars,
with the average
temperature ranging from
-140° C to 20° C.
Deimos
Moons




Mars has two very
small moons, Phobos
(fear) and Diemos
(terror).
They are named after
the horses that pulled
Mars’s chariot.
The larger Deimos is
only 23-km in
diameter.
Both appear to be
captured asteroids.
Phobos
Mars
Missions



There have been many
missions to Mars, starting
with the Viking craft in
1976.
There are currently two
orbiters and one rover
collecting data on Mars.
While Spirit finally stopped
responding last year,
Opportunity is starting its
9th year of operation.
Pretty good for a planned
90 day mission!
Manned missions are also
currently being planned,
around 2025 or so.
Mars






Diameter: 0.5 Earth
Distance: 1.5 AU
Atmosphere: 96% carbon dioxide at 0.01
atmospheres.
Features: large canyons, volcanoes. Two moons,
both are captured asteroids.
Ancient dried up lakes, streams, rivers, and
seas. Called the Red Planet.
Life: Possibly ancient life when there was liquid
water on the planet. Could still exist under the
sand.