Minor Members of the Solar Minor Members of the Solar SystemSystem

Chapter 23, Section 4Chapter 23, Section 4

AsteroidsAsteroids

Asteroid – Asteroid – small rocky bodies that have been small rocky bodies that have been likened to “flying mountains”likened to “flying mountains”

Most asteroids lie between the orbits of Mars Most asteroids lie between the orbits of Mars and Jupiter. They have orbital periods of 3 to 6 and Jupiter. They have orbital periods of 3 to 6 years.years.

Some have very eccentric orbits, a few regularly Some have very eccentric orbits, a few regularly pass Earth and our moonpass Earth and our moon

Many asteroids have irregular shapes, and some Many asteroids have irregular shapes, and some planetary geologists believe the asteroids are planetary geologists believe the asteroids are fragments of a broken planet (pulled apart by the fragments of a broken planet (pulled apart by the immense gravity of Jupiter)immense gravity of Jupiter)

Asteroid OrbitsAsteroid Orbits

CometsCometsComets – Comets – pieces of rocky and metallic materials pieces of rocky and metallic materials held together by frozen gasesheld together by frozen gasesMost comets travel in elongated orbits, taking Most comets travel in elongated orbits, taking them past Pluto and take hundreds of thousands them past Pluto and take hundreds of thousands of years to go around the sun.of years to go around the sun.ComaComa – glowing head of a comet, caused by the – glowing head of a comet, caused by the solar energy vaporizing frozen gasessolar energy vaporizing frozen gasesA small glowing nucleus with a diameter of only A small glowing nucleus with a diameter of only a few kilometers can sometimes be detected a few kilometers can sometimes be detected within a coma. As comets approach the sun, within a coma. As comets approach the sun, some develop a tail that extends for millions of some develop a tail that extends for millions of kilometers.kilometers.The tail of the comet always points away from The tail of the comet always points away from the sun, this is accounted for by the solar wind the sun, this is accounted for by the solar wind and radiation pressureand radiation pressure

CometsComets

Comet’s Tail OrientationComet’s Tail Orientation

Beyond the PlanetsBeyond the Planets

Kuiper Belt – where most short-period Kuiper Belt – where most short-period comets are thought to originate from, it is a comets are thought to originate from, it is a belt of material orbiting outside the orbit of belt of material orbiting outside the orbit of Neptune.Neptune.

Oort Cloud – Unlike the Kuiper Belt Oort Cloud – Unlike the Kuiper Belt comets, these comets have longer orbital comets, these comets have longer orbital periods and aren’t confined to the plane of periods and aren’t confined to the plane of the solar system. The Oort Cloud appears the solar system. The Oort Cloud appears as a spherical shell of comets and other as a spherical shell of comets and other materials surrounding our solar system.materials surrounding our solar system.

Beyond the PlanetsBeyond the Planets

MeteoroidsMeteoroidsMeteoroid –Meteoroid – a small solid particle that travels through a small solid particle that travels through spacespaceMost meteoroids originate from any one of the Most meteoroids originate from any one of the following sources: (1) interplanetary debris that was following sources: (1) interplanetary debris that was not gravitationally swept up during the formation of the not gravitationally swept up during the formation of the solar system, (2) material from the asteroid belt, or (3) solar system, (2) material from the asteroid belt, or (3) the solid remains of comets that once traveled near the solid remains of comets that once traveled near Earth’s orbitEarth’s orbitMeteor – Meteor – meteoroids that enter Earth’s atmosphere meteoroids that enter Earth’s atmosphere and burn up, a “shooting star”and burn up, a “shooting star”The light that we see is caused by the friction between The light that we see is caused by the friction between the meteor and the airthe meteor and the airMeteorite – Meteorite – a meteoroid that reaches Earth’s surfacea meteoroid that reaches Earth’s surfaceA few meteorites have blasted out craters on Earth’s A few meteorites have blasted out craters on Earth’s surfacesurface

MeteoroidsMeteoroids

World Map of Major Impact World Map of Major Impact StructuresStructures

The Age of the Solar SystemThe Age of the Solar System

How did scientists determine the age of the How did scientists determine the age of the Solar System?Solar System?They use radiometric dating to determine that They use radiometric dating to determine that the oldest meteorites found on Earth formed the oldest meteorites found on Earth formed more than 4.54 billion years agomore than 4.54 billion years agoScientists believe that the composition of these Scientists believe that the composition of these meteorites is similar to the composition of other meteorites is similar to the composition of other materials in the inner solar system during its materials in the inner solar system during its formationformationThe oldest moon rocks are believed to be ~4.5 The oldest moon rocks are believed to be ~4.5 billion years oldbillion years oldThe oldest known Earth rocks are found in The oldest known Earth rocks are found in Canada ~4 billion years oldCanada ~4 billion years old

Age of the Solar SystemAge of the Solar System

AssignmentAssignment

Read Chapter 23, Section 4 (pg. 660-664)Read Chapter 23, Section 4 (pg. 660-664)

Do Section 23.4 Assessment #1-6 (pg. 664)Do Section 23.4 Assessment #1-6 (pg. 664)