Most material in the normal impact region is converted into small fragments after the impact while the large fragments are from material far from the normal impact region.

研究结果同时表明正撞击区内的材料大部分转化为了小碎片，大碎片则由远离正撞击区的材料产生。

youdao

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