Howardites

The answer sheet for the worksheet The NC–CC isotopic dichotomy. 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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Answers: The NC–CC isotopic dichotomy

  1. C: Relatively late in Earth's growthMolybdenum and other elements suggest a CC contribution that came relatively late.
  2. A: In the CC fieldMaterial from both asteroids belongs to the CC group.
  3. B: Imperfect mixing of material from different starsIf the disc's dust was not perfectly mixed, regions inherited different proportions of isotopes from different stars.
  4. C: They are preservedOrdinary geological processes on a parent body cannot create or erase these anomalies.
  5. D: The large-scale dynamics of the young discMeteorites record not only local history but the movement of material across the young disc.
  6. False: the right answer is CV in CC, IIIAB in NCAll carbonaceous chondrite groups are CC, while IIIAB is one of the NC iron groups.
  7. True (IVB)IIC, IID, IIF, IIIF and IVB are CC irons; IAB, IIAB, IIIAB and IVA are NC.
  8. Both made cores at the same time without mixing (accept any answer with the same meaning)NC and CC irons formed cores within about the first 1 to 4 million years, so something kept the reservoirs apart.
  9. They separate stellar processes in irons and stones (accept any answer with the same meaning)Molybdenum separates the effects of different nucleosynthetic processes and is measurable in both irons and stony meteorites.
  10. In the outer disc, beyond Jupiter (accept any answer with the same meaning)CC material was held in the outer disc and NC material inside Jupiter's orbit.

Task

Answers will vary. The task comes from the lesson: Make a two-column table headed NC and CC. Sort every meteorite group mentioned in this course into one column, and add Earth, Mars, Ryugu and Bennu.

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

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