1. Small Bodies In Space: Asteroids, Comets and Meteors

2. Small Bodies in Space? o Besides the sun, 8 planets and their moons there are also: o Asteroids o Comets o Meteors …or space leftovers?!

3. Asteroids Asteroid: A rocky object in space that can be a few feet wide to several hundred miles wide. Asteroid: A rocky object in space that can be a few feet wide to several hundred miles wide. Asteroids are fragile, inactive objects Asteroids are fragile, inactive objects Majority orbit the sun Majority orbit the sun Are found in the asteroid belt between the orbits of Mars and Jupiter Are found in the asteroid belt between the orbits of Mars and Jupiter

4. Asteroids: Size Range in size: from 1 km across to over 100 km across Range in size: from 1 km across to over 100 km across The first and largest asteroid Ceres; was discovered in 1801 The first and largest asteroid Ceres; was discovered in 1801 933 km in diameter 933 km in diameter The smallest asteroid 1991 BA was discovered in 1991 The smallest asteroid 1991 BA was discovered in 1991 6 meters across 6 meters across

5. Asteroids: Composition Astronomers classify asteroids based on what they are made of: Astronomers classify asteroids based on what they are made of: Carbon Carbon Minerals Minerals

6. Asteroids: Measurement In 1991 the USA created and launched the first space probe for close range observation of asteroids In 1991 the USA created and launched the first space probe for close range observation of asteroids Named Galileo Named Galileo First asteroid photographed; Gaspra First asteroid photographed; Gaspra

7. Asteroids: Measurement In 1996 National Aeronautics and Space Administration (NASA) launched the probe NEAR (Near Earth Asteroid Rendezvous) In 1996 National Aeronautics and Space Administration (NASA) launched the probe NEAR (Near Earth Asteroid Rendezvous) Flew by Mathilde in 1997 Flew by Mathilde in 1997 Flew by Eros in 1998 Flew by Eros in 1998 Landed on Eros in 2001 Landed on Eros in 2001 In 2000 it was renamed NEAR-Shoemaker after an American Astronomer In 2000 it was renamed NEAR-Shoemaker after an American Astronomer

8. Asteroids: Orbit Orbit: the path a moon, planet, or small body in space takes as it travels around another body in space Orbit: the path a moon, planet, or small body in space takes as it travels around another body in space Most follow an oval-shaped orbit in the asteroid belt Most follow an oval-shaped orbit in the asteroid belt

9. Asteroids: Orbit Some follow orbits outside the asteroid belt and follow the same orbit as Jupiter; known as Trojans Some follow orbits outside the asteroid belt and follow the same orbit as Jupiter; known as Trojans Some asteroids are known as near-Earth asteroids, they orbit in the inner solar system Some asteroids are known as near-Earth asteroids, they orbit in the inner solar system Can cross the orbital path of Mars and Earth Can cross the orbital path of Mars and Earth

10. Asteroids: Collisions with Earth Many scientists believe that a near-Earth Asteroid collided with Earth around 65 million years ago, which triggered global environmental changes that led to the extinction of the dinosaurs. Many scientists believe that a near-Earth Asteroid collided with Earth around 65 million years ago, which triggered global environmental changes that led to the extinction of the dinosaurs.

11. Asteroids: Gravitational Force The gravitational pull from Jupiter and other large planets causes asteroid orbits to slowly change The gravitational pull from Jupiter and other large planets causes asteroid orbits to slowly change Orbital changes can lead asteroids to collide with one another; increasing the likelihood of further collisions Orbital changes can lead asteroids to collide with one another; increasing the likelihood of further collisions Collisions create smaller asteroids and fragments. Collisions create smaller asteroids and fragments. Some small fragments reach the earths surface as meteorites. Some small fragments reach the earths surface as meteorites.

12. Group Discussion Why are there asteroids between Mars and Jupiter instead of a planet? Why are there asteroids between Mars and Jupiter instead of a planet? Why do you think the asteroid belt is located where it is? Why do you think the asteroid belt is located where it is? Do you think that there is a high or low probability that the Earth will be hit by another large asteroid? Why? Do you think that there is a high or low probability that the Earth will be hit by another large asteroid? Why?

13. Comets: Dirty Snowballs from Space Comet: A small object made up of ice, dust and gas that orbit the sun. Jets of gas and dust form long tails that reflect sunlight and can be seen from Earth Comet: A small object made up of ice, dust and gas that orbit the sun. Jets of gas and dust form long tails that reflect sunlight and can be seen from Earth Consist of a solid nucleus core that is surrounded by a cloudy atmosphere called a coma and has one or two tails Consist of a solid nucleus core that is surrounded by a cloudy atmosphere called a coma and has one or two tails Comets are usually only seen through a telescope Comets are usually only seen through a telescope

14. Comets: Astronomers believe that comets are the left over debris from 4.6 billion years ago when the outer planets were first formed Astronomers believe that comets are the left over debris from 4.6 billion years ago when the outer planets were first formed

15. Comets: Classification Astronomers classify comets according to how long they take to orbit the sun Astronomers classify comets according to how long they take to orbit the sun Short-Period comets need less than 200 years to complete one orbit Short-Period comets need less than 200 years to complete one orbit Long-Period comets takes 200 years or more to complete one orbit Long-Period comets takes 200 years or more to complete one orbit

16. Comets: The Kuiper Belt Scientists think that short-period comets come from a band of objects called the Kuiper belt; which lies beyond the orbit of Pluto Scientists think that short-period comets come from a band of objects called the Kuiper belt; which lies beyond the orbit of Pluto Within the Kuiper belt comets are inactive Within the Kuiper belt comets are inactive The gravitational pull of the outer planets can shift objects out of the Kuiper belt and into the inner solar system where they become active comets The gravitational pull of the outer planets can shift objects out of the Kuiper belt and into the inner solar system where they become active comets

17. Comets: The Oort Cloud Long-period comets come from the Oort cloud; a nearly spherical collection of icy bodies about 1,000 times farther away from the sun than Pluto Long-period comets come from the Oort cloud; a nearly spherical collection of icy bodies about 1,000 times farther away from the sun than Pluto Within the Oort cloud comets are inactive Within the Oort cloud comets are inactive Gravitational interactions with passing stars can cause the icy bodies in the Oort cloud to enter the inner solar system and become active comets Gravitational interactions with passing stars can cause the icy bodies in the Oort cloud to enter the inner solar system and become active comets

18. Comets Comets move in long, oval shaped orbits that can cross the almost circular orbit of the planets. Comets move in long, oval shaped orbits that can cross the almost circular orbit of the planets. Sometimes comets collide with planets and their moons; the majority of impact craters across the galaxy are a result of comet collisions Sometimes comets collide with planets and their moons; the majority of impact craters across the galaxy are a result of comet collisions

19. Comets: Life Comets lose ice and dust each time they return to the inner solar system; leaving behind trails of dusty debris Comets lose ice and dust each time they return to the inner solar system; leaving behind trails of dusty debris When Earth travel through on of these trails the debris become meteors that burn up into the Earths atmosphere. When Earth travel through on of these trails the debris become meteors that burn up into the Earths atmosphere. Eventually a comet will lose all of its ice, it will then break up and dissipate into clouds of dust or turn into fragile, inactive objects (similar to asteroids) Eventually a comet will lose all of its ice, it will then break up and dissipate into clouds of dust or turn into fragile, inactive objects (similar to asteroids)

20. Comets: Halley’s Comet Originally discovered in 1682 by Sir Edmund Halley Originally discovered in 1682 by Sir Edmund Halley Passes earth every 76 years Passes earth every 76 years Most famous comet Most famous comet When it passed near Earth in 1986, five spacecraft flew past the comet and gathered information about its appearance and chemical composition When it passed near Earth in 1986, five spacecraft flew past the comet and gathered information about its appearance and chemical composition

21. Group Discussion If Halley was discovered in 1782, and Halley takes 76 years to orbit the sun, roughly when will Halley pass earth again? How old will you be? If Halley was discovered in 1782, and Halley takes 76 years to orbit the sun, roughly when will Halley pass earth again? How old will you be? Do you think there will be visible differences in Halley’s comet the next time it appears? What differences would you expect to see? Do you think there will be visible differences in Halley’s comet the next time it appears? What differences would you expect to see? How many more times do you predict Halley will pass by earth again? Why? How many more times do you predict Halley will pass by earth again? Why?

22. ANSWER The next time the Halley comet will pass earth will be in 2062 The next time the Halley comet will pass earth will be in 2062

23. Meteors: Meteor: Appear when a chunk of metallic or stony matter called a meteoroid enters the Earths atmosphere from outer space Meteor: Appear when a chunk of metallic or stony matter called a meteoroid enters the Earths atmosphere from outer space A bright streak of light that appears briefly in the sky: can be seen with the unaided eye A bright streak of light that appears briefly in the sky: can be seen with the unaided eye Often called falling/shooting stars Often called falling/shooting stars Meteoroids come from broken, disintegrated pieces of comets and asteroids Meteoroids come from broken, disintegrated pieces of comets and asteroids

24. Meteors Air friction heats up the meteoroid chunk and causes it to glow and create a shining trail of gases and melted particles Air friction heats up the meteoroid chunk and causes it to glow and create a shining trail of gases and melted particles Most glow for about a second, Most glow for about a second, Most disintegrate long before touching the Earths surface Most disintegrate long before touching the Earths surface Meteoroids that reach the Earths surface are called meteorites Meteoroids that reach the Earths surface are called meteorites

25. Meteors Millions of meteors occur in the Earths atmosphere every day – most are no bigger than a pebble Millions of meteors occur in the Earths atmosphere every day – most are no bigger than a pebble Meteoroids travel around the sun in a variety of orbit shapes and velocities Meteoroids travel around the sun in a variety of orbit shapes and velocities Fastest ones move 42 km per second Fastest ones move 42 km per second

26. Meteors The earth encounters a number of streams (trails) or swarms (clusters) of tiny meteoroids at certain times of the year. The earth encounters a number of streams (trails) or swarms (clusters) of tiny meteoroids at certain times of the year. Streams and swarms have oval-shaped orbits like comets Streams and swarms have oval-shaped orbits like comets The most brilliant meteor shower took place in November 12-13 1833. Since then this meteor shower continues to take place every November and seems to come from the direction of the constellation Leo (Leonid Shower) The most brilliant meteor shower took place in November 12-13 1833. Since then this meteor shower continues to take place every November and seems to come from the direction of the constellation Leo (Leonid Shower)

27. Meteors: Types There are three kinds of meteors: There are three kinds of meteors: Stony: consist of minerals rich in silicon and oxygen and come from the outer crust of a comet/asteroid Stony: consist of minerals rich in silicon and oxygen and come from the outer crust of a comet/asteroid Iron: consist mostly of iron and nickel and comes from the metallic core of a comet/asteroid Iron: consist mostly of iron and nickel and comes from the metallic core of a comet/asteroid Stony-iron: Consists of equal amounts of silicon/oxygen and iron/nickel and come from the inner crust of a comet/asteroid Stony-iron: Consists of equal amounts of silicon/oxygen and iron/nickel and come from the inner crust of a comet/asteroid

28. Meteors: Size Meteor size varies; most are relatively small Meteor size varies; most are relatively small Larger bodies like asteroids and comets can also strike the earth and become meteorites. Larger bodies like asteroids and comets can also strike the earth and become meteorites. Meteors will only strike the earth surface when they are just the right size, if they are too small they disintegrate into the atmosphere, if they are too big they will often explode when they hit the atmosphere – raining down much smaller pieces Meteors will only strike the earth surface when they are just the right size, if they are too small they disintegrate into the atmosphere, if they are too big they will often explode when they hit the atmosphere – raining down much smaller pieces Thousands of small meteorites have been found in Antarctica, which have provided scientists with clues to the types of materials that form planets Thousands of small meteorites have been found in Antarctica, which have provided scientists with clues to the types of materials that form planets

29. Meteors: Impact Craters Scientists have found more than 120 impact craters/basins on earth from meteors, comets, asteroids. Scientists have found more than 120 impact craters/basins on earth from meteors, comets, asteroids. Most famous: Meteor Crater in Arizona Most famous: Meteor Crater in Arizona 1, 275 meters across and 175 meters deep 1, 275 meters across and 175 meters deep Formed nearly 50, 000 years ago when an iron meteorite weighing 330, 000 metric tons struck the Earth Formed nearly 50, 000 years ago when an iron meteorite weighing 330, 000 metric tons struck the Earth Most impact points larger than the meteor crater have been worn away by time and surface changes Most impact points larger than the meteor crater have been worn away by time and surface changes

30. Group Discussion Why do people confuse a falling meteor with a falling star? Why do people confuse a falling meteor with a falling star? When you think about or see a falling meteor how does it make you feel? When you think about or see a falling meteor how does it make you feel? Do you really think it is possible to know what small body a meteor came from? Do you really think it is possible to know what small body a meteor came from?