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The answer sheet for the worksheet The journey from the asteroid belt. 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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Adult · Adults; no background neededAnswer sheet for teachers

Answers: The journey from the asteroid belt

  1. A: Many separate collisions released its piecesA cluster marks one break-up; ages scattered with no clusters point instead to many separate events.
  2. A: One collision released them all at onceA cluster of similar exposure ages points to a single break-up that set many fragments loose together.
  3. B: The collision that broke it off as a small fragmentIsotopes build up once the rock becomes a body only metres across, which happens when a collision breaks it free.
  4. B: About a million yearsRegular tugs in a resonance stretch the orbit within about a million years.
  5. C: A spinning body absorbing sunlightThe push comes from a rotating body that absorbs sunlight and re-radiates the heat unevenly.
  6. True (Exactly one third of Jupiter's period)A resonance with Jupiter means a simple fraction of Jupiter's own period, such as one third.
  7. True (It acts for millions of years and adds up)A very small but steady thrust, kept up over millions of years, gradually reshapes the orbit.
  8. They all began on their parent body's orbit (accept any answer with the same meaning)A family is the debris of one shattered asteroid, so its fragments set off on orbits close to their parent's.
  9. From rare isotopes made in it by cosmic rays (accept any answer with the same meaning)The amounts of isotopes produced by cosmic rays reveal how long the body was exposed in space.
  10. Helium-3 and neon-21 (accept any answer with the same meaning)Cosmic rays striking a small body produce rare isotopes such as helium-3 and neon-21.

Task

Answers will vary. The task comes from the lesson: Visit the asteroids section of this site and look up Vesta and one asteroid of your choice. Note where each orbits and how big it is. Then write a few sentences describing the journey of a fragment from Vesta to Earth, using the words collision, Yarkovsky effect, resonance and exposure age.

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

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