has quality composed primarily of environmental material astronomical body part cryosphere For the moment the definition links to liquid water but in the future we might need to link to other materials for other planets, e.g., Mars. Need to make this planet agnostic. Might want to not have the definition link to years as some astronomical body parts might not be in systems with years. Note that in a strict sense, rocks are also frozen but in a practical sense we use terms like "solidified". This maybe something to revist if we add more astrogelogical content. frozen