re: The Comet: film from images of the Rosetta mission

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I don’t know what I expected the comet to be, but a tumbling chunk of rock/ice is not it. In my mind that’s an asteroid.

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I think it becomes a comment when it grows a tail.

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I think I remember my fifth grade teacher saying the main difference between asteroids and comets is their composition, as in, what they are made of. Asteroids are made up of metals and rocky material, while comets are made up of ice, dust and rocky material. Both asteroids and comets were formed early in the history of the solar system about 4.5 billion years ago. Asteroids formed much closer to the Sun, where it was too warm for ices to remain solid. Comets formed farther from the Sun where ices would not melt. Comets which approach the Sun lose material with each orbit because some of their ice melts and vaporizes to form a tail.

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It looks like a kidney stone.

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Would be tough to pass that