Where, I'm unsure, but when, I think I know. There is a theory that the first asteroid to hit Earth was actually a comet. It wiped out the dinosaurs.
The answer to your question is a
Answer:
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Answer: 1) Ganymede, 2) lo, 3) Europa, 4) Tidal heating, 5) Callisto, 6) orbital resonance
Explanation:
What you're looking for in here is the hardness: a material can scratch another material if it's harder than it.
So the desired material cannot be harder than amphibole, which has a hardness of 6.
But it has to be harder than fluorite, which has a hardness of 4.
So we're looking for a hardness of between 4 and 6 and from the table we see it's magnesite (we'll need a hard magesite) - this is the correct answer!
