Threats to Earth

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 it’s 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. Rocks 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. Sun Mars Jupiter Asteroids craters Earth water dust Earth million extinction dinosaurs sunlight atmosphere temperatures climate Asteroids atmosphere climate comets craters dinosaurs dust Earth extinction Jupiter Mars meteors million Neptune rocks Saturn snowballs Sun sunlight temperatures water

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 andthat 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. Halley’s Comet Reappears every 76 yearsImage from 1986

13. Hale-Bopp as seen fromCraig 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. 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?

19. Threats to Earth Answers • 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? 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.

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 andthat 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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