Chapter 27 – The Planets and the Solar System

Page 586 Do you think it is possible to count the

rings of Saturn? The rings look solid in the image, do

you think they are? What do you think they are made of? What do we know about the planets?

Chapter 27.1

The Inner Planets

Two Planetary Neighborhoods

Inner Planets – Mercury, Venus, Earth, Mars

All have rocky crust Dense mantle layers and cores Because of their Earth like

appearance they are also known as terrestrial planets

Distance Between Planets Outer Planets – Jupiter, Saturn, Uranus,

Neptune and Pluto 1st four are called Jovian – or Jupiter like Very large gaseous planets with no

rocky crust Low density due to size Have ring systems Pluto is an oddball – not dense enough

to be terrestrial; too small to be Jovian

Mercury

Nearest to the Sun Orbits the sun in 88 days Smallest of terrestrials Mercury surface resembles the

moon’s Rotates every 59 days Temperature – day 400°C; night –

200°C

Chapter 27.2

Venus – Earth’s Sister Planet – 2nd planet from the Sun Near each other similar in

diameter, mass and gravity Venus is the only planet to

rotate from east to west Rotates every 243 days Orbits every 225 days Thick yellow clouds make

surface impossible to see

Magellan radar mapped it Fault system Yellow clouds made of sulfuric acid Surface is hot due to greenhouse

effect (CO2) causing surface to be 475°C

Visible from Earth in the morning or early evening – “evening star”

Mars – 4th planet from the Sun

687 day orbit Axis tilted about the same as

earth’s giving it seasons. However they are 2 times as long

Very thin atmosphere (1% of Earth’s) mostly CO2

Has ice caps – thought to be water covered by frozen CO2

Spacecraft have photographed and landed on Mars surface

Largest known volcano in the solar system “Olympus Mons”

Has a valley system suggesting water once ran on its surface

Page 543, 5 Martian landings

Outer Planets

Jovian Planets – Jupiter, Saturn, Uranus and Neptune

Much larger than terrestrials – smallest, Uranus, is 15 times more massive than earth

No solid surfaces – their “surface” is an uppermost gas layer

Composed mainly of light elements H and He

All Jovian planets have ring systems

Jupiter – 5th Planet from the Sun 11.9 year orbit 10 hour rotation Has 2 times more mass than all the other

planets combined Radiates 2 times as much energy back into

space as it receives from the sun Galileo probe entered Jupiter’s atmosphere

in 1995 – found no thick clouds and higher than expected temperatures

Saturn – 6th planet from the Sun

30 year orbit 10 hour rotation Lowest density of all planets,

less than 1 Saturn also radiates more

energy than it receives from the sun, like Jupiter it has internal heat sources

Uranus – 7th planet from the sun

84 year orbit 17.2 hour rotation It’s rotational axis is tipped

almost completely over It’s magnetic field is not tipped

Chapter 27.3

Neptune – 8th planet (most of the time) 165 year orbit Rotation 16.1 hours Neptune was found after

astronomers predicted its location mathematically in 1846

Winds over 2000 km/hr Becomes the 9th planet when Pluto is

taken close to the Sun due to Pluto’s highly elliptical orbit

Pluto

248 year orbit Smallest planet in the Solar

System Its moon, Charon, is ½ its size Most of its atmosphere is

frozen. However, it thaws slightly when it nears the sun

Planetary Satellites (moons)

Satellites of Earth and Mars

Earth has one moon Mars has 2 tiny moons, Deimos

and Phobos Phobos circles mars 3 times a

day Mercury and Venus have no

satellites

Jupiter’s Moons

At least 63 Galilean moons – Io, Europa,

Ganymede and Callisto are the 4 largest discovered by Galileo

Io is geologically active Nine active volcanoes No signs of crater impacts Galileo spacecraft found it has an

iron core surrounded by a molten silicate rock

Heat on Io is caused by tidal forces from Jupiter

Europa Surface is thought to be frozen

water It is thought liquid water may

exist under the ice

Ganymede – the largest Larger than Pluto and Mercury Surface of ice

Callisto – most heavily cratered object in the solar system

Saturn’s Moons

At least 31 moons Largest is Titan

Only moon in solar system to have a substantial atmosphere

Uranus’s Moons

At least 27 5 major moons are Titania,

Oberon, Umbriel, Ariel, and Miranda All lack atmosphere and are

heavily cratered

Neptune’s Moons

At least 13 moons – Triton is the largest

Solar System Debris

Comets and TNOs (Trans Neptune Objects)

Comets described as dirty snowballs Spend most of their time beyond

the orbit of Neptune Do not become visible until they

travel inside Jupiter’s orbit

Has 2 parts, nucleus and tail Tail always points away from the

sun due to solar winds Most famous comet is Halley’s, it

appears once every 76 years – last visit 1986

Asteroids – solid rocklike masses

Uneven surface causes their brightness to change

Revolve same direction as planets

Most in asteroid belt between Mars and Jupiter

Meteors and Meteoroids

Meteoroid – rock or ice fragment traveling in space, they differ from asteroids in that they are smaller in size

Meteor – when a meteoroid enters earth’s atmosphere and burns up “shooting star”

Meteor shower – occurs when earth passes into debris left by a comet that crossed earth’s path – very predictable, named after the constellation in the background.

Chapter 27.4

Meteorite A large meteoroid that survives earth’s

atmosphere and strikes its surface 3 types

Stony – resemble earth’s rocks, mostly made of silicates

95% Irons – mostly iron

5% Stony irons

<1% Most found in the ice of Antarctica

Impact Craters – bowl shaped depressions that remain after a meteor or other object strikes earth

Rare on earth because The atmosphere burns up most

meteoroids Earth is geologically active

Best known is Barringer Meteor Crater in AZ