Deep Impact also found evidence of ice on the surface of the comet, not just inside it.

深度撞击项目组还发现了证据表明冰不仅仅存在于彗星内部，也存在于彗星表面。

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If matches are found, then identification of the material inside the comet would be accomplished.

BBC: Q&A: Deep Impact comet mission

In addition to taking normal images of the impact in the visible spectrum, the HRI provides an infrared "fingerprint" of the material from inside the comet's nucleus.

BBC: Q&A: Deep Impact comet mission

The idea is to create an impressive extraterrestrial firework display to celebrate the success of the American rebellion while at the same time allowing the mother-ship to record what is inside the comet.

ECONOMIST: Those space probes in full