5 Comets………Dirty Balls of Ice They look like a star with a ghostly white tail.The term "comet" derives from the Greek aster kometes, which means "long- haired star"---a reference to the tail.
6 Comets………Dirty Balls of Ice They can be seen by us only when they pass by the sun and the sun’s heat melts them.The comet's tail is made of material from the comet; gasfrom the ices and dust that is mixed in with the ice. They escape as the comet melts.The tail always points away from the sun due to the solar winds (movement of heat away from sun)
7 They travel around the sun in long looping orbits that bring them near the sun on one end and around Jupiter on the other end.Example:If a comet has a large orbit, it takes a long time to go around the Sun. Some comets are "short-period" comets that take five or ten years to complete an orbit. Some comets are "long-period" comets that take decades, centuries, or millenia to orbit the Sun.
8 Comets………Dirty Balls of Ice The icy, hard part of the comet is called the nucleus. As the comet melts, sometimes large chunks of ice break off in a hurry and large amounts of gases escape at once and cause a bright “outburst”.The gas and dust are released and form an atmosphere around the comet called the coma.
9 After 500 or so passes near the Sun, most of a comet's ice and gas is lost - leaving a rocky object very much like an asteroid in appearance.
10 Asteroids……Rockin’ Around Asteroids are LARGE chunks of rock and metal that orbit the sun.They range from just over ½ a mile (1km) to a few hundred miles in diameter (diameter = how wide across)
11 Most asteroids travel in the wide gap between the inner planets and outer planets (between Mars and Jupiter).But a few travel in paths across Mar’s orbit and some even cross in Earth’s orbit.
12 Most of the chunks or rock and metal in space came together long ago to form the planets and moons. Asteroids are left- over pieces of rock from when the solar system was formed.
14 How are meteorites related to asteroids? Meteorites are pieces of asteroids - or sometimes planets or the Moon.
15 Key Questions: 1. Has Earth ever been hit by a comet or an asteroid Key Questions: 1.Has Earth ever been hit by a comet or an asteroid? If yes, how have such impacts affected Earth? 2.How often does a comet or an asteroid hit Earth?
16 Module 3 Activity 1: (Simulation Activity) What happens when a comet or an asteroid hits Earth?Main objective- describe how impact craters are formed when a comet or asteroid hits Earth, based on a simulation
20 QUESTIONS:Q1. What do you notice about the shape of your pebble’s crater and the shape of the impact crater shown in the photo?Q2. What do you think happened to the plants and animals living in the area where the comet or asteroid crashed?Q3. Which is most likely to make a more frequent “visitor” of Earth: a comet or an asteroid? Why do you think so?
28 Barringer’s CraterAn iron meteorite 100 feet across and 70,000 tons slamed into the Earth at about 43,000mph in the Arizona desert near Flagstaff 40,000 years ago. Barringer Crater is 4,100 feet wide and 571 feet deep.
30 Key IdeasSome comets and asteroids may become Near-Earth Objects as they orbit the Sun.Other planets in the Solar System (gravity) are believed to affect the NEOs’ orbits, thus they crashed into Earth.Comets and asteroids have hit Earth in the past.
31 An impact crater is formed on the ground where a comet, asteroid, or their fragments hit Earth's surface. Large-scale impacts changed the physical geography of the surrounding, killed living creatures in the surrounding area, and most probably caused global climate change (e.g., ice age). Comets and asteroids have similarities and differences (Table 1). Their major differences are in their origin and composition.
44 AnswerA meteor shower happens when Earth passes through the orbit of a comet (or an asteroid) where fragments and dust remain in orbit and orbits the Sun as well while Earth goes around the Sun. Since there are more dust and fragments, there are more meteoroids that may burn up in Earth’s atmosphere as Earth passes the orbit of the parent comet or asteroid.
47 What have we learned? • Why is there an asteroid belt? Orbital resonances with Jupiter disrupted the orbits of planetesimals, preventing them from accreting into a planet. Those that were not ejected from this region make up the asteroid belt today. Most asteroids in other regions of the inner solar system accreted into one of the planets.• How are meteorites related to asteroids?Most meteorites are pieces of asteroids. Primitive meteorites are essentially unchanged since the birth of the solar system. Processed meteorites are fragments of larger asteroids that underwent differentiation.
48 Comets and asteroids may break apart while orbiting the Sun Comets and asteroids may break apart while orbiting the Sun. These smaller fragments are called meteoroids.Rock fragments coming from the Moon, Mars, and other planets are also called meteoroids.
49 Meteor and meteor showers are light phenomena. The meteoroid burns as it enters Earth’s atmosphere. Surviving fragments that land on Earth are called meteorites.Meteor and meteor showers are light phenomena.
50 Meteors…Shooting Stars or Space Garbage Meteors are also called shooting starsMeteors are small pieces of space debris (junk) pulled into Earth’s atmosphere by gravity.Meteorites are metallic rocks broken off from asteroids and cometsMeteors fall to Earth at speeds from 22,000 MPH to 64,000 MPH (8x shuttle speed)You Can Buy Meteors-
51 Most meteors are only as big as a grain of sand. Most burn up while entering Earth’s AtmosphereHowever………………They can be bigger. Craters in the Earth and ones studied below the surface show that one about the size of a house landed about 250,000 years ago! Is that what killed the dinosaurs???
52 Meteors are falling all the time. On a clear, dark night you may see one.During the annual meteor storms, you may see 100 per hour.
53 How can something as small as a grain of sand light up so brightly? Entering the Earth’s atmosphere so fast creates a lot of friction. The friction causes them to heat up and give off light.The light trail may stay in the sky for up to 30 minutes and end with a “POP”.REALLY bright meteors are called FIREBALLS
55 What’s That Up In The Sky??? COMETSASTEROIDSMETEORSMade of ice-have tailsMade of rock and metalStay in spaceFall into Earth’s atmosphereOrbit the sunGravity pulls to Earth; they burn up as they fall