Touring Our Solar System

Chapter 23

23.1 The Solar System

99.85% of the mass of our solar system is in the Sun, planets make up the rest.

Gravity holds planets in orbit.A. Overview of the Planets

Terrestrial planets: small and rockyJovian planets: huge gas giants

How long is Jupiter’s “year”? How long is Mercury’s “year?

23.1 The Solar System

Interiors of the PlanetsClasses: (based on melting

point)gases: H and He (-273oC)rocks: silicate and iron (> 700oC)ices: ammonia, methane, carbon dioxide, and water. (between others)

23.1 The Solar System

Atmosphere of the Planets

Planets can only have an atmosphere if gravity is great enough.

Ex: Earth: 11 km/s escape velocity.

He and H escape from Earth.

23.1 The Solar System

B. Formation of solar System.

Nebular TheorySun and planets formed from a rotating disk of gas and dust.

Planetesimals collided and built the planets and become round.

23.2 Terrestrial Planets

A. Mercury:Smallest planet (no atmosphere)Dense with many cratersScraps from coolingTemperature:-173 to 427oC59 earth-day rotation88 earth-day revolution

23.2 Terrestrial PlanetsB. Venus:255 Earth-day “year”Thick crushing atmosphere (97%

carbon dioxide) 90x pressure Temperture-475oC

Radar maps shows basaltic volcanism and tectonic activity.

Most flat plains with few mountains.

23.2 Terrestrial PlanetsC. Mars:Polar caps made of CO2

Large long dust stormsMost atmosphere escapedOlympus Mons- 23 km highValles Marineris

23.2 Terrestrial PlanetsC. Mars:Rovers discovered marks of liquid

water on Mars

23.3 Outer Planets (and Pluto)Jupiter: Giant Among Planets1/800 of Sun Mass2.5x greater then all others

planets together.Great Red Spot- seen cyclonic

storm seen Giovanni Cassini about 1690.

Structure: pressure to make hydrogen into a liquid.

May have rocky core.

23.3 Outer Planets (and Pluto)Jupiter:Moons:Io- volcanicEurpoa- fractured icy surfaceGanymede- largest, parallel

grovesCallisto- many craters

23.3 Outer Planets (and Pluto)Jupiter:Rings:Very faint

Maybe fragments of 2 smaller moons

23.3 Outer Planets (and Pluto)Saturn:Rings: Main feature100 m thick

23.3 Outer Planets (and Pluto)Saturn:Moons:56 currentlyTitan – largest

Atmosphereand hydrocarbon seas

Enceladus-volcanic and water geysers

23.3 Outer Planets (and Pluto)Uranus: Planet on its

side.

Winking star was a sign of a ring (9)

Miranda

23.3 Outer Planets (and Pluto)Neptune: Windy Planet1000km/hrGreat Dark Spot: Storm

like Giant red Spot.Vanished! Repapered.Methane clouds.Triton –retrograde and

volcanic

23.3 Outer Planets (and Pluto)Pluto: Dwarf PlanetFails to attract object

in its orbit. (clearing its orbit)

228 yearsCharon-moon

23.4 Minor MembersNEAR ShoemakerLanded on asteroid

ErosVery low gravityMost asteroids are

between Mars and Jupiter.

23.4 Minor MembersCometsMade of rocks, frozen

water, methane, carbon dioxide and carbon monoxide.

Very elongated orbits.Tail points away from

the sun.

23.4 Minor MembersCometsMany short period

come from the Kuiper Belt

Long period come from the Oort Cloud

23.4 Minor MembersCometsHalley’s Comet1986 Giotto probe

passed within 600 km

8 km x 16 km

23.4 Minor MembersMeteoroidsSmall solid particles3 sources:

interplanetary debrisasteroid beltcomet remains

Meteors-burn up in contact with atmosphere.

Meteorites- reaches Earth

23.4 Minor MembersMeteoroidsAge of meteorites are

about 4.567 billion years old.

Made mostly of iron.Meteor Showers-

annual event from comet passes across Earth’s orbit.