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Hypothetical alternatives to water include ammonia , which , like water , is a polar molecule , and cosmically abundant ; and non-polar hydrocarbon solvents such as methane and ethane , which are known to exist in liquid form on the surface of Titan .
 Titan
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Titan