Chapter 19-2

The Inner and Outer Planets

Rocket Science . . .http://www.youtube.com/watch?v=mmlM5XQxdMs

Source: http://vathena.arc.nasa.gov/curric/space/planets/

The Nine Eight Planets• The term “planet” is derived from the Greek

for “wanderer” (picture not to scale)

Planets

• Five visible w/o telescope– Mercury, Venus, Mars, Jupiter, Saturn

• Nine Eight total– Uranus, Neptune, Pluto– Who is Clyde Tombaugh, and why should you know?

• Moons: (define satellite)– Earth’s: Luna, “loony,” werewolves, moonth– Jupiter’s: Galilean (Io, Europa, Ganymede, Callisto) disc. by . . .

Galileo Galilei– Saturn’s, Uranus,’ Neptune’s– Pluto’s size ~ Charon’s; considered a binary system

Planets & Their Moons

The planets, to scale

The Terrestrial Worlds

Inner Planets: Overview

• Inside the asteroid belt• “Terrestrial” planets

–Small–Solid surfaces–Composed of rocks & metals–High densities–Few satellites

Inner Planets: Mercury• God of commerce, travel

& thievery (speed)• Closest to sun

– Orbit didn’t behave according to Newton’s predictions on planetary motion• Caused by Vulcan?

– Reconciled by Einstein’s General Theory of Relativity

Inner Planets: Venus• Ancient goddess of

beauty• Bright, beautiful

morning/evening “star”

• Heavily clouded w/CO2

• Hot, sulfuric acid• Runaway

greenhouse effect

Inner Planets: Earth• Hydrosphere• Thick enough

atmosphere to protect from UV– Mercury’s is too thin, no

protection– Venus’ is too thick, traps

energy• Oxygenated via

volcanic gases & photosynthesis

Inner Planets: Mars

Mars Rover Landing

Surface Exploration

Olympus Mons

Valles Marinaris

Polar CO2 “ice” caps

Exobiology

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

Mars• Two tiny moons (20 km

diameter)• Very thin atmosphere of

carbon dioxide• No liquid water on surface• Mostly frigid (200 K), but

occasionally warm (290 K)• Chance of microbial life,

especially in past

MARSThe Red Planet

Al-Qahira Auqakuh

Ares

Huo Hsing

Maíadim

Shalbatnu

Hrad

Her Descher

Harmakhis

Bahram

WHY DO YOU THINK MARS IS RED?

a) Mars is red because that is where men are from. Men get red when they are angry or embarrassed or trying to not pass gas in mixed company.

WHY DO YOU THINK MARS IS RED?

(b) Mars is red because it has such a thin atmosphere, which cannot hold the blue like the earth's atmosphere can. Mars is also red because of all of the rusted iron dust surrounding the planet and all the rusted iron on the planet.

WHY DO YOU THINK MARS IS RED?

(c) The ancient Roman god, Mars, was a great hunter (and resident of Georgia) who was smeared with red blood. Mars had a gun rack on the back of his truck, and liked to shoot off his guns on New Year's Eve. Mars was originally called the Redneck god, but over time, people just started saying, "Mars is red."http://www.why-is-the-sky-blue.tv/mars-red.htm

OKAY, REALLY . . .

• FROM http://image.gsfc.nasa.gov/poetry/ask/a10510.html

• Mars’ is red because of the prevalence of iron oxides (rust) on the surface.

SCHIAPARELLI

H. G. WELLS

• Lowell's theories influenced the young English writer H.G. Wells, who in 1898

published “The War of the Worlds”• In this novel, Wells created an invasion of Earth by deadly aliens from Mars and

launched a whole new genre of alien science fiction.

• Radio broadcast Halloween 1938

Mars landings (1976, 1997)

Why haven’t we gone to Mars?

• 140 times farther than the moon (at best)

• Months of weightlessness is crippling

• Serious radiation hazards• Would have to carry food,

fuel, oxygen to last years• Taking earth bacteria to

Mars could confuse search for native Martian life

• So much to learn from robotic exploration!

IS THE FACE ON MARS REAL?•  The "face" is nothing

more than a hill that has been eroded by billions of years of Martian winds. The original Viking orbiter image showed the hill illuminated from an angle that highlighted certain features, creating the impression of a face.

WATER, VOLCANOES, ICE CAPS

• Canyon: would reach from Chicago to LA if on Earth http://www.kidscosmos.org/kid-stuff/mars-facts.html

• Dust storms can last for months• Two moons, Phobos (fear) & Deimos

(panic)

VOLCANOES

• Olympus Mons, largest volcano in the solar system

• Covers an area about the size of Arizona

• More than 3 times the height of Mt. Everest

Asteroids

• “Asteroid” means “starlike”

• Also called minor planets– 3 to 700 km diameter

• Hundreds of thousands have been identified

• The largest (Ceres) has a diameter of 1023 km

• Most in belt between Mars and Jupiter

• Some cross Earth’s orbit (called Apollo objects)

Source: http://www.solstation.com/stars/asteroid.htm

Source: http://www.mira.org/fts0/planets/098/images/gaspra.jpg

Source: http://cfa-www.harvard.edu/iau/lists/InnerPlot.html

Asteroid Belt (10/4/04)

Orbitof

Jupiter

Orbitof

Mars

Orbitof

Earth

Green dots represent minor planets

Outer Planets: Overview• Outside asteroid belt• “Jovian” planets, or gas giants• Primarily hydrogen & helium• Low densities• Deep atmospheres• Rings• Many Satellites

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

Outer Planets: Jupiter• Largest planet in solar

system– Could hold 1300 Earths– If 80x larger, would have

become a star

• 10-hour day• 12 (Earth)years to orbit sun• Great Red Spot: hurricane• Galilean Satellites

– Io, Europa, Callisto, Ganymede

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

Jupiter• 11 times earth’s diameter (1/10

sun’s diameter)• 300 times earth’s mass (1/1000

sun’s mass)• Visible surface is gas (mostly

hydrogen); interior must be mostly liquid, with solid core

• Fascinating banded patterns, hurricanes, great red spot

• Four large moons, many small ones

• Visited briefly 4 times in 1970’s (Pioneer, Voyager); orbited by Galileo spacecraft 1995-2003

Saturn• Prettiest planet in small

telescopes• 9 times earth’s diameter • 100 times earth’s mass (1/3

Jupiter)• Gaseous surface, liquid interior,

solid core (like Jupiter)• Rings!• Many moons• Visited by Pioneer 11 (1979),

Voyager 1 & 2 (1980-81); Cassini will arrive next year for a 4-year mission

Saturn’s rings

Rings are mostly ice particles, from tiny grains to boulder-sized chunks. Gaps are created by tug of nearby moons.

Uranus• Discovered by William

Herschel, 1781• At the threshold of naked-

eye visibility• Less than half the size of

Saturn, and nearly twice as far

• Another gas giant planet with rings (faint), many moons

• Spin axis is tipped sideways• Visited by Voyager 2, 1986

Uranus• Discovered by William

Herschel, 1781• At the threshold of naked-

eye visibility• Less than half the size of

Saturn, and nearly twice as far

• Another gas giant planet with rings (faint), many moons

• Spin axis is tipped sideways• Visited by Voyager 2, 1986

Moons of UranusAll are icy, smaller than our own moon.

Neptune• Discovered by mathematics

(anomaly in orbit of Uranus) in 1845-46, by John C. Adams and Urbain Leverrier

• Can be seen in binoculars (looks like a faint star)

• About the same size as Uranus, but 60% farther away

• Voyager 2 discovered a cool blue spot, which has since disappeared

• Largest moon, Triton, is a little smaller than our own and orbits backwards; surface is covered with ice

In a class by itself: Pluto• Is it a planet? (Neil DeGrasse Tyson on

The Daily Show)– Small, rocky– Unlike other outer planets

• Moon, Charon– Proportionally larger than the moons of any other

planets• Discovered by Kansan in 1930

– Clyde Tombaugh, age 24– Of Burdett, KS– While a teen, built his own telescopes, grinding his

own mirrors– Asked advice from Lowell Observatory; was

offered a job• Picture & narration

The comets

• “Comet” means “hairy”• Thousands have been

identified but the total population may be 10 trillion

• Total mass may be greater than Jupiter’s

• Divided into short-period and long-period comets

• Located in two areas:– Kuiper belt– Oort cloud

Source: http://www.solarviews.com/raw/comet/west.gif

Source: http://www.solarviews.com/browse/comet/halebop2.jpg

Where the comets live

Source: http://www.solarviews.com/browse/comet/kuiper3.jpg

The Oort cloud

Source: http://spaceguard.esa.int/NScience/neo/neo-what/com-oort.htm