CHAPTER 29 – THE SOLAR SYSTEM

Section 1 – Wrote notes on board

SECTION 2 – THE INNER PLANETS

The inner planets are also referred to as Terrestrial planets (Earth-like)

Mercury, Venus, Earth, Mars

Small, dense, rocky

Metal core

No rings

Mercury Closest to the sun

Smallest planet now that Pluto is not a planet

Orbit period = 88 days

Planetary day = 59 days

Almost no atmosphere

Cold nights (-280 F)

Hot days (800 F)

Very dense, thought to have large iron core

No moons

Venus Second planet from the sun

Orbit period = 225 days

Planetary day = 243 days

Rotates opposite on its axis

Second to the Moon in brilliance

Similar to Earth in

Size, Density, and Location

Shrouded in thick clouds of sulfuric acid

Atmosphere is 97% carbon dioxide

Surface atmospheric pressure is 100 times that of Earth’s

Venus

The clouds of Venus do not allow visible light through

The Magellan orbiter produced radar images of the surface of Venus from 1990 to 1994

Earth

Third planet from the sun

Fifth largest planet

One moon

Life is possible because of distance from sun

Venus to close…to hot for liquid water

Mars to far…to cold for liquid water

Planets – A Brief Tour Mars

The “Red Planet”

Orbit period = 687 days

Planetary day = 24 hours 37 minutes

Cold polar temps (-193 F)

Polar caps of water ice, covered by thick layer of frozen carbon dioxide

Mars Numerous large

volcanoes

Largest is Olympus Mons

Mars Several canyons

Some larger than Earth’s Grand Canyon

Calles Marineras – The largest canyon

Almost 5000 km long

That’s as long as the U.S.

Mars “Stream drainage”

patterns

Found in some valleys

No bodies of surface water on the planet

Possible origins

Past rainfall

Surface material collapses as the subsurface ice melts

Planets – A Brief Tour Moons of Mars

Two moons

Phobos

Deimos

Captured asteroids

The fourth planet out from the Sun, Mars, has two moons. The are named Phobos (meaning "fear") and Deimos (meaning "panic"); appropriate companions for Mars, the God of War.

SECTION 3 – THE OUTER PLANETS

The outer planets are also referred to as the Jovian planets (Jupiter-like)

Jupiter, Saturn, Uranus, Neptune

Large, low-density, gaseous

Massive

Referred to as “Gas Giants”

All have rings, but Saturn's are the most prevalent

Jupiter

5th planet from sun

Largest planet

Orbit period = 12 years

Very massive 2.5 times more massive

than combined mass of all the planets, satellites, and asteroids

If it had been ten times larger, it would have been a small star

Jupiter

Rapid rotation

Slightly less than 10 hours

Slightly bulged equatorial regions

Banded appearance

Jupiter

Great Red Spot

In planet’s southern hemisphere

Like a giant hurricane, has been going for hundreds of years

600 km/hr winds

Jupiter

Structure

Liquid hydrogen ocean

Halfway into the interior, pressure causes liquid hydrogen to turn into metallic hydrogen

Core of rock and metallic minerals

Jupiter

At least 28 moons

Four largest moons

Discovered by Galileo

Called Galilean satellites

Saturn

Sixth planet from sun

Second largest planet

At least 20 moons

Orbit period = 29.5 years

Planetary day = 10 hours 40 minutes

Also has banded appearance

Saturn

Saturn has such a low density (0.7 g/cm3) it would actually float in water!

Uranus

7th planet from sun

3rd largest

Orbit period = 84 years

Planetary day = 17 hours

Uranus and Neptune are nearly twins

Rotates “on its side”

At least 15 moons

Neptune

8th planet from sun

Orbit period = 165 years

Planetary day = 16 hours

Dynamic atmosphere

1,000 km/hr winds!

Great Dark Spot

Storm the size of Earth

White cirrus-like clouds above the main cloud deck

Eight moons

Pluto

Now a “minor planet” or “planetoid”

Not visible with the unaided eye

Orbit period = 250 years

Planetary day = 6 days

Highly elongated orbit cases it to occasionally travel inside the orbit of Neptune, where it resided from 1979-1999

1 Moon (Charon)

The moon is half the size of Pluto

Average temp is -210 C

Planets – A Brief Tour

29.4 – ASTEROIDS, COMETS, AND METEOROIDS

There are millions of smaller bodies of matter flying all around the solar system

Some are just bits of dust or ice, others are as large as small moons

They are leftover material from the nebula that formed our solar system

Asteroids

Asteroids are the largest of the smaller bodies in the solar system

Fragments of rock that orbit the sun

More than 50,000 asteroids for sure, possible millions

Asteroids have impacted the Earth, causing mass extinctions in the past

Asteroids

Most lie between Mars and Jupiter in what is known as the Asteroid Belt

Asteroids

Three main types of asteroids

1.) Made of carbon materials

Dark in appearance

2.) Made of iron and nickel

Metallic appearance

3.) Made of silicate minerals

Looks like ordinary earth rocks

Asteroids

Some asteroids are not in the asteroid belt

Trojan Asteroids are in groups just ahead of and just behind Jupiter

Earth-grazers have very elongated orbits which brings them close to Earth at times

They can, and have, collide with Earth

Planets – A Brief Tour

Comets Often compared to large “dirty

snowballs”

Composition Frozen Gases (water, methane, ammonia)

Rocky and metallic materials

Frozen gases vaporize when near the sun Produces a glowing head called the coma

Some develop a tail that points away from the Sun due to radiation pressure and solar wind

Comets

Three main parts

1.) Nucleus

2.) Coma

3.) Tail

Comets

Scientists think that comets come from a very distant cloud of dust and ice called the Oort Cloud

They are so far away from the sun that many take millions of years to orbit

Comets

Long-period Comets – Periods of several thousands or even millions of years

Short-period Comets – Periods of around 100 years Halley’s Comet appears

every 76 years

Meteoroids

Meteoroids are smaller bits of rock or metal

Called meteors when they enter Earth’s atmosphere

A meteor shower is when Earth encounters a swarm of meteoroids

Meteoroids are referred to as meteorites when they are found on Earth

Meteoroids

Most are less than 1 mm in diameter

A large one would be greater than 1 cm in diameter

Can be produced by collisions between asteroids

Meteoroids Most meteoroids burn up when entering

Earth’s atmosphere

This is what you are seeing when you see a “shooting star”

Meteoroids

Three basic types of meteorites

1.) Stony Meteorites Similar to Earth rocks

2.) Iron Meteorites Metallic appearance

3.) Stony-iron Meteorites Contain both iron and stone (very rare)

Meteorites from Mars?

Meteorite found in Antarctica in 1984

Thought to have come from Mars!

In 1996 scientists discovered fossil evidence of microorganisms

How could it have reached Earth? Why is this significant?