Threats to EarthP2g part 1 & 2

Objectives

In this lesson we should learn:• about the properties of asteroids• how asteroids have affected Earth in the

past

OutcomesFoundation PaperYou 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

The asteroid Gaspra, found in the Asteroid Belt between

Mars & Jupiter

Asteroid Ida with it’s moon Dactyl

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

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.

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.

Asteroids atmosphere climate cometscraters dinosaurs dust Earthextinction Jupiter Mars meteorsmillion Neptune rocks Saturnsnowballs Sun sunlight temperatureswater

RocksSun MarsJupiterAsteroids

Earth cratersdust water

Earth millionextinction dinosaurs

sunlight atmospheretemperatures climate

OutcomesFoundation PaperYou 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 paperExplain why the asteroid belt is between Mars

and Jupiter: the large gravity of Jupiter disrupts the formation of a planet

Objectives

• In this lesson we should learn:• about the properties of comets• how astronomers are monitoring the

danger from near-Earth asteroids and comets

OutcomesFoundation PaperYou 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

Halley’s Comet Reappears every 76 years

Image from 1986

Hale-Bopp as seen fromCraig County, VA in 1997

Hale-Bopp as seen

from Alexandria, VA in 1997

Hale-Bopp as seen from Wyoming in 1997

Yerkes Observatory

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

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

Answers1. 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

OutcomesFoundation PaperYou 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 paperExplain why the speed of a comet increases as it

approaches a star: the strength of gravity increasesSuggest and discuss possible actions which could be

taken to reduce the threat of NEOs

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