Chapter 27 The Planets and the Solar SystemPage 586Do 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 NeighborhoodsInner Planets Mercury, Venus, Earth, MarsAll have rocky crustDense mantle layers and coresBecause of their Earth like appearance they are also known as terrestrial planets

Distance Between PlanetsOuter Planets Jupiter, Saturn, Uranus, Neptune and Pluto1st four are called Jovian or Jupiter likeVery large gaseous planets with no rocky crustLow density due to sizeHave ring systemsPluto is an oddball not dense enough to be terrestrial; too small to be Jovian

MercuryNearest to the SunOrbits the sun in 88 daysSmallest of terrestrialsMercury surface resembles the moonsRotates every 59 daysTemperature day 400C; night 200C

Chapter 27.2

Venus Earths Sister Planet 2nd planet from the SunNear each other similar in diameter, mass and gravityVenus is the only planet to rotate from east to westRotates every 243 daysOrbits every 225 daysThick yellow clouds make surface impossible to see

Magellan radar mapped itFault systemYellow clouds made of sulfuric acidSurface is hot due to greenhouse effect (CO2) causing surface to be 475CVisible from Earth in the morning or early evening evening star

Mars 4th planet from the Sun687 day orbitAxis tilted about the same as earths giving it seasons. However they are 2 times as longVery thin atmosphere (1% of Earths) mostly CO2Has ice caps thought to be water covered by frozen CO2

Spacecraft have photographed and landed on Mars surfaceLargest known volcano in the solar system Olympus MonsHas a valley system suggesting water once ran on its surfacePage 543, 5 Martian landings

Outer Planets

Jovian Planets Jupiter, Saturn, Uranus and NeptuneMuch larger than terrestrials smallest, Uranus, is 15 times more massive than earthNo solid surfaces their surface is an uppermost gas layerComposed mainly of light elements H and HeAll Jovian planets have ring systems

Jupiter 5th Planet from the Sun11.9 year orbit10 hour rotationHas 2 times more mass than all the other planets combinedRadiates 2 times as much energy back into space as it receives from the sunGalileo probe entered Jupiters atmosphere in 1995 found no thick clouds and higher than expected temperatures

Saturn 6th planet from the Sun30 year orbit10 hour rotationLowest density of all planets, less than 1Saturn also radiates more energy than it receives from the sun, like Jupiter it has internal heat sources

Uranus 7th planet from the sun84 year orbit17.2 hour rotationIts rotational axis is tipped almost completely overIts magnetic field is not tipped

Chapter 27.3

Neptune 8th planet (most of the time)165 year orbitRotation 16.1 hoursNeptune was found after astronomers predicted its location mathematically in 1846Winds over 2000 km/hrBecomes the 9th planet when Pluto is taken close to the Sun due to Plutos highly elliptical orbit

Pluto248 year orbitSmallest planet in the Solar SystemIts moon, Charon, is its sizeMost of its atmosphere is frozen. However, it thaws slightly when it nears the sun

Planetary Satellites (moons)

Satellites of Earth and MarsEarth has one moonMars has 2 tiny moons, Deimos and PhobosPhobos circles mars 3 times a dayMercury and Venus have no satellites

Jupiters MoonsAt least 63Galilean moons Io, Europa, Ganymede and Callisto are the 4 largest discovered by Galileo

Io is geologically activeNine active volcanoesNo signs of crater impactsGalileo spacecraft found it has an iron core surrounded by a molten silicate rockHeat on Io is caused by tidal forces from Jupiter

EuropaSurface is thought to be frozen waterIt is thought liquid water may exist under the ice

Ganymede the largestLarger than Pluto and MercurySurface of iceCallisto most heavily cratered object in the solar system

Saturns MoonsAt least 31 moonsLargest is TitanOnly moon in solar system to have a substantial atmosphere

Uranuss MoonsAt least 275 major moons are Titania, Oberon, Umbriel, Ariel, and MirandaAll lack atmosphere and are heavily cratered

Neptunes MoonsAt least 13 moons Triton is the largest

Solar System Debris

Comets and TNOs (Trans Neptune Objects)Comets described as dirty snowballsSpend most of their time beyond the orbit of NeptuneDo not become visible until they travel inside Jupiters orbit

Has 2 parts, nucleus and tailTail always points away from the sun due to solar windsMost famous comet is Halleys, it appears once every 76 years last visit 1986

Asteroids solid rocklike massesUneven surface causes their brightness to changeRevolve same direction as planetsMost in asteroid belt between Mars and Jupiter

Meteors and MeteoroidsMeteoroid rock or ice fragment traveling in space, they differ from asteroids in that they are smaller in sizeMeteor when a meteoroid enters earths atmosphere and burns up shooting star

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

Chapter 27.4

MeteoriteA large meteoroid that survives earths atmosphere and strikes its surface3 typesStony resemble earths rocks, mostly made of silicates95%Irons mostly iron5%Stony irons

Impact Craters bowl shaped depressions that remain after a meteor or other object strikes earthRare on earth becauseThe atmosphere burns up most meteoroidsEarth is geologically activeBest known is Barringer Meteor Crater in AZ