Slide 1: Threats to Earth P2g part 1 & 2
Slide 2: Objectives In this lesson we should learn: • about the properties of asteroids • how asteroids have affected Earth in the past
Slide 3: Foundation Paper You should now be able to.. • State that large asteroids have collided with the Earth in the past and describe some of the consequences and evidence of such collisions • State that asteroids are rocks and describe that asteroids are left over from the formation of the Solar System and where they can be found. Higher paper • Explain why the asteroid belt is between Mars and Jupiter: the large gravity of Jupiter disrupts the formation of a planet Outcomes
Slide 4: The asteroid Gaspra, found in the Asteroid Belt between Mars & Jupiter
Slide 5: Asteroid Ida with it’s moon Dactyl
Slide 6: Asteroids • Asteroids are large rocks left over from the formation of the Solar System They are mostly between the orbits of Mars and Jupiter • Asteroids (large rocks) have collided with the Earth in the past causing: - craters, - ejection of hot rocks, - widespread fires, - sunlight blocked by dust, - climate change, - species extinction
Slide 7: Collisions? • The evidence for past collision on Earth includes: - craters - layers of unusual elements in rocks - sudden changes of fossil numbers between adjacent layers of rock.
Slide 8: Rocks Asteroids are small ______________ which orbit the Sun Mars ______________, mainly between ______________ and Jupiter ______________. Occasionally, a long time ago, ______________ are thought to have struck Asteroids craters ______________, forming large ______________ and huge Earth water amounts of ______________ and ______________ vapour. dust An enormous asteroid is believed to have hit Earth ______________ 65 ______________ years ago, leading to million the ______________ of the ______________. extinction dinosaurs ______________ could not penetrate the ______________ sunlight atmosphere temperatures climate so ______________ fell, causing ______________ change. Asteroids craters extinction million snowballs water atmosphere dinosaurs Jupiter Neptune Sun climate dust Mars rocks sunlight comets Earth meteors Saturn temperatures
Slide 9: Foundation Paper You should now be able to.. State that large asteroids have collided with the Earth in the past and describe some of the consequences and evidence of such collisions State that asteroids are rocks and describe that asteroids are left over from the formation of the Solar System and where they can be found. Higher paper Explain why the asteroid belt is between Mars and Jupiter: the large gravity of Jupiter disrupts the formation of a planet Outcomes
Slide 10: Objectives • In this lesson we should learn: • about the properties of comets • how astronomers are monitoring the danger from near-Earth asteroids and comets
Slide 11: Outcomes Foundation Paper You should now be able to.. • Describe that a comet is made from ice and dust, the tail of a is a trail of debris and that comets have highly elliptical orbits • Describe that the speed of a comet increases as it approaches a star • Describe a near-Earth object (NEO) as an asteroid or comet on a possible collision course with Earth and how NEO may be seen with telescopes and that observations can be used to determine their trajectories Higher paper • Explain why the speed of a comet increases as it approaches a star: the strength of gravity increases • Suggest and discuss possible actions which could be taken to reduce the threat of NEOs
Slide 12: Halley’s Comet Reappears every 76 years Image from 1986
Slide 13: Hale-Bopp as seen from Craig County, VA in 1997
Slide 14: Hale-Bopp as seen from Alexandria, VA in 1997
Slide 15: Hale-Bopp as seen from Wyoming in 1997
Slide 16: Yerkes Observatory
Slide 17: Comets • Comets are balls of rock and ice, with trails of debris blown outward by the Sun • They have highly elliptical orbits and speed up as they approach the sun • The trajectories of observed objects can be predicted accurately • If an asteroid (or comet) on a collision course with Earth is spotted early enough, it may be possible to alter the trajectory of the asteroid
Slide 18: Threats to Earth • How can asteroids and comets be seen? • What is the difference between a comet and an asteroid? • What can be done to protect us from asteroid impacts?
Slide 19: Threats to Earth Answers • How can asteroids and comets be seen? With telescopes, because they reflect light from the Sun. • What is the difference between a comet and an asteroid? Asteroids are large rocks usually in orbit between Mars and Jupiter. Comets are ice and rock found in very elliptical orbits. • What can be done to protect us from asteroid impacts? Detect them early and then alter their course.
Slide 20: Outcomes Foundation Paper You should now be able to.. Describe that a comet is made from ice and dust, the tail of a is a trail of debris and that comets have highly elliptical orbits Describe that the speed of a comet increases as it approaches a star Describe a near-Earth object (NEO) as an asteroid or comet on a possible collision course with Earth and how NEO may be seen with telescopes and that observations can be used to determine their trajectories Higher paper Explain why the speed of a comet increases as it approaches a star: the strength of gravity increases Suggest and discuss possible actions which could be taken to reduce the threat of NEOs