1. Threats to Earth P2g part 1 & 2

2. Objectives In this lesson we should learn: about the properties of asteroids how asteroids have affected Earth in the past

3. Outcomes 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

4. The asteroid Gaspra, found in the Asteroid Belt between Mars & Jupiter

5. Asteroid Ida with its moon Dactyl

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

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.

8. Asteroids are small ______________ which orbit the ______________, mainly between ______________ and ______________. Occasionally, a long time ago, ______________ are thought to have struck ______________, forming large ______________ and huge amounts of ______________ and ______________ vapour. An enormous asteroid is believed to have hit ______________ 65 ______________ years ago, leading to the ______________ of the ______________. ______________ could not penetrate the ______________ so ______________ fell, causing ______________ change. Asteroidsatmosphereclimatecomets cratersdinosaursdustEarth extinctionJupiter Marsmeteors million NeptunerocksSaturn snowballsSunsunlight temperatures water Rocks SunMars Jupiter Asteroids Earth craters dust water Earth million extinctiondinosaurs sunlightatmosphere temperaturesclimate

9. Outcomes 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

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

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

12. Halleys Comet Reappears every 76 years Image from 1986

13. Hale-Bopp as seen from Craig County, VA in 1997

14. Hale-Bopp as seen from Alexandria, VA in 1997

15. Hale-Bopp as seen from Wyoming in 1997

16. Yerkes Observatory

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

18. 1.How can asteroids and comets be seen? 2.What is the difference between a comet and an asteroid? 3.What can be done to protect us from asteroid impacts? Threats to Earth

19. Answers 1.How can asteroids and comets be seen? 2.What is the difference between a comet and an asteroid? 3.What can be done to protect us from asteroid impacts? With telescopes, because they reflect light from the Sun. Asteroids are large rocks usually in orbit between Mars and Jupiter. Comets are ice and rock found in very elliptical orbits. Detect them early and then alter their course. Threats to Earth

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

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