Ascertain the phase state of water ice in the coma of 3I/ATLAS

Ascertain whether the water ice present in the coma of the interstellar comet 3I/ATLAS is predominantly amorphous or crystalline by obtaining higher signal-to-noise near-infrared spectroscopy or other diagnostic observations that enable robust spectral modeling of ice phase indicators.

Background

The physical phase of water ice (amorphous versus crystalline) encodes its formation and thermal history, with amorphous ice forming below ~100 K and transitioning to crystalline above ~137 K. Differentiating these phases spectroscopically requires sufficient signal-to-noise and resolution.

Although the authors detect water ice signatures and model the coma composition, the available IRTF data have limited signal-to-noise, preventing constraints on the ice phase. Clarifying the phase state would inform the origin and thermal evolution of 3I/ATLAS in its parent system.