Howardites

The answer sheet for the worksheet The journey through the atmosphere. Each answer comes with the reason, so it can be used to mark or to go over the questions with the class.

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Start here: Explorer · Ages 10 and upAnswer sheet for teachers

Answers: The journey through the atmosphere

  1. A: Tiny dropletsThe melted surface is swept away in tiny droplets almost as soon as it forms.
  2. C: Earth's 30 km/s added to the 42 km/s solar-orbit limitA meteoroid at the 42 km/s limit for staying in solar orbit near Earth, meeting Earth's 30 km/s head-on, arrives at about 72 km/s.
  3. A: The same way as Earth, at nearly the same speedEarth's gravity speeds up even a meteoroid drifting along with Earth to about 11 km/s, so arriving that slowly means its motion nearly matched Earth's.
  4. B: It is ploughing into thicker and thicker airThe air thickens with depth, so the pressure on the front of the meteoroid rises rapidly.
  5. B: Explosions or thunderThe booms can carry tens of kilometres and are often mistaken for explosions or thunder.
  6. True (Old cracks weaken them until air pressure exceeds their strength)Many are already cracked from ancient collisions, so they fragment when the pressure becomes greater than their strength.
  7. True (Less than half of it survives as meteorites)Ablation and break-up usually remove most of a meteoroid's mass before it lands.
  8. Each break-up exposes fresh surfaces (accept any answer with the same meaning)Every time the meteoroid fragments, fresh surfaces are exposed and the fireball flares.
  9. A layer of squeezed, glowing gas in front of the rock (accept any answer with the same meaning)The meteoroid hits air molecules so fast that a layer of compressed, glowing gas forms in front of it.
  10. Winds at different heights (accept any answer with the same meaning)Winds at different heights push the fragments sideways as they fall.

Task

Answers will vary. The task comes from the lesson: Next time there is a reported fireball in the news, look at the map of where it was seen. Notice how the track runs in one direction. Where along that track would you expect the biggest pieces to land, and why?

Look for work that uses the key words correctly and gives a reason for each point.

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