Comet ice is expected to be either crystalline or amorphous, depending on if the Solar System's protoplanetary disc formed hot (> 300K) or cold with ices inherited from the interstellar medium--explained Bin Yang today at #Astronomy2024 #IAU2024--You can measure ice structure with JWST (Fresnel Peak in the infrared spectrum). Which is super cool, but... turns out inconclusive! Different comets (so far) are showing a range of icy structures.