What effect does exposure to interstellar cosmic radiation have on water ice in objects like 'Oumuamua?

• A. It causes the complete sublimation of the ice.
• B. It can result in the formation of embedded pockets of hydrogen gas.
• C. It converts water to oxygen-rich ice.
• D. It produces solid CO ice.

Answer: (B)

Exposure to interstellar cosmic radiation drives chemical changes in water ice through radiolysis. Energetic particles strike water molecules, breaking bonds and producing hydrogen along with oxygen-containing fragments. In cold, solid ice, some of the hydrogen becomes trapped in tiny voids, forming embedded pockets of hydrogen gas within the ice. This outcome is more consistent with radiolysis than with complete sublimation, formation of oxygen-rich ice, or creation of CO ice, since the radiation alters the internal chemistry and creates gas pockets rather than simply melting or reordering the ice into other compounds.