Howardites

The answer sheet for the worksheet Ordinary chondrites: H, L and LL. 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: Ordinary chondrites: H, L and LL

  1. B: Low total iron and low metalLL means low total iron and low metal, a chemical description of the group.
  2. A: From surviving grains of chromiteTiny chromite grains survive the replacement and reveal an L chondrite origin.
  3. D: How iron-rich the pyroxene isFs stands for ferrosilite, the iron-rich end-member of pyroxene, and it rises from H to L to LL.
  4. A: It is less securely known than LL'sSeveral asteroids have been proposed for H chondrites, but their parent body is less certain than those of L and LL.
  5. D: Olivine and low-calcium pyroxeneOlivine and low-calcium pyroxene are the main minerals, with smaller amounts of feldspar, metal and troilite.
  6. True (It aims electrons at a polished sample and reads X-rays)The microprobe fires a focused electron beam at a polished sample and measures the X-rays given off.
  7. True (L)Fa22 to Fa26 is the range for L chondrites; H is lower and LL higher.
  8. About 15 to 20 per cent (accept any answer with the same meaning)H chondrites have the most metal of the three groups, very roughly 15 to 20 per cent by weight.
  9. A huge collision broke up their parent body (accept any answer with the same meaning)Shared shock and reheating at one time points to a catastrophic collision that broke up the L parent body.
  10. Earth received a burst of L chondrite debris (accept any answer with the same meaning)The fossil meteorites are L chondrites in rock of about the break-up age, showing an unusually intense shower of debris.

Task

Answers will vary. The task comes from the lesson: Compare photographs of cut H, L and LL chondrites in a museum catalogue or book. Can you see differences in the amount of shiny metal? Rank them by metal content before reading the labels.

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

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