What are the criteria for defining habitable environments in the search for extraterrestrial life, and what are the prospects for discovering life beyond Earth within our solar system and in exoplanetary systems?

Habitability criteria include the presence of liquid water, energy sources, and chemical building blocks necessary for life. Ongoing exploration missions to Mars, Europa, and Enceladus seek evidence of past or present life, while future telescopes aim to characterize the atmospheres of exoplanets and search for biosignatures indicative of life elsewhere in the universe.