Chapter 28.4 Asteroids, Comets & Meteoroids Std 1f: Know the evidence for the dramatic effects that asteroid impacts have had in shaping the surface of planets and their moons and in mass extinctions of life on Earth Objective 1: Describe the physical characteristics of asteroids and comets Objective 2: Describe the Kuiper Belt and the Oort Cloud Objective 3: Compare meteoroids, meteorites and meteors

Asteroids Asteroids - a small, rocky object that orbits the sun The largest of the small bodies in the solar system More than 50,000 have been discovered The larger asteroids are known as “minor planets”

Asteroid Belt Most asteroids are located in a region between Mars and Jupiter known as the Asteroid Belt

Composition of Asteroids Composition (made out of) is similar to inner planets 3 categories of asteroids composition: 1) Silicate materials 2) Iron & Nickel 3) Carbon material (rarest)

Near-Earth Asteroids More than 1,000 asteroids have orbits that bring them very close to Earth Asteroids could strike Earth causing significant damage Asteroid detection programs track these near-Earth asteroids to help predict possible collisions

Comets Comets - small bodies of ice, rock and cosmic dust with an elliptical orbit around the sun It gives off gas and dust in the form of a tail as it passes close to the sun Most famous is Halley’s Comet which passes by Earth every 76 years (last time 1986) Hale-Bopp passed by in 1997

Composition of comets Comets have several parts: Core (nucleus)- made of rock, metals, and ice Coma- a spherical cloud of gas and dust surrounds the core (core & coma form the head of the comet) Tail- form when sunlight changes the comet’s ices to gases. Solar wind pushes the gas away from the sun

Objective 1: Describe the physical characteristics of asteroids and comets Where are most asteroids found? Between Mars and Jupiter (Asteroid belt) What are the 3 different compositions of asteroids? Silicate materials, nickel and iron, and Carbon What is a small, icy, rocky object that orbits the sun? comet What are the 3 parts that make up a comet? Core, coma, tail

Comets

The Oort cloud Most comets originate in the Oort cloud Oort cloud - a spherical cloud of dust and ice that surrounds the solar system and extends from the Kuiper belt to almost halfway to the nearest star Long-period comets – comets that take more than 200 years to complete one orbit of the sun

The Kuiper belt Pluto may be the largest body in this belt Kuiper belt - A region of the solar system just beyond the orbit of Neptune that contains small bodies of mainly ice

Objective 2: Describe the Kuiper Belt and the Oort Cloud Where is the Kuiper belt located? Beyond Neptune Where is the Oort cloud located? Surround the solar system almost to the next star Where do most comet originate? Oort cloud What is the largest body in the Kuiper belt? Pluto

Short period comets They take less than 200 years to complete one orbit around the sun Halley’s comet is a short period comet

Meteoroids (in space) Meteoroids -A relatively small, rocky body that travels through space Diameter is less than 1mm They are probably pieces of matter that come from passing comets Produce meteor showers Lyrid meteor shower (caused by dust from Thatcher comet) Peaks April 22 (best viewing 3:30 – 4:40am)

Meteors (in the atmosphere) Meteors -A bright streak of light that results when a meteoroid burns up in Earth’s atmosphere Meteors are commonly called shooting stars Meteoroids sometimes vaporize very quickly in a brilliant flash of light called a fire ball Meteor shower - A large number of small meteoroids entering Earth’s atmosphere in a short period of time D New report Amazing video

Meteorites (hits Earth) Large meteors may not burn up completely in the atmosphere If it hits the Earth’s surface it is known as a meteorite 3 types of meteors: 1) Stony 2) Iron 3) Stony iron

Objective 3: Compare meteoroids, meteorites and meteors What is a small rocky body that travels through space? meteoroid What is the bright streak of light caused by meteoroid burning up? meteor What is a meteor that hits the Earth? meteorite What are 3 types of meteors? Stoney, iron, stoney iron