Requirements for Life
Astrobiologists ask: where else in the universe could LIFE exist? To answer, they identify the REQUIREMENTS for known life. The big three: (1) LIQUID WATER, (2) ENERGY (sunlight, chemicals, or heat), (3) CHEMISTRY of carbon-based molecules (CHNOPS — carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur). Wherever these meet on Earth, life thrives. The same may be true elsewhere.
Life on Earth in EXTREME places. THERMOPHILES live in 200°F+ hot springs. PSYCHROPHILES live in Antarctic ice. BARORESISTANT bacteria live miles deep in the ocean under crushing pressure. RADIATION-RESISTANT bacteria survive radiation that would kill a human 1000x over. These EXTREMOPHILES tell us life is tougher than we thought — expanding the range of "habitable" environments we should search.
Which is the MOST critical requirement for ALL known life forms?
Promising places to search. MARS: had liquid water in the past; possibly today underground. EUROPA (Jupiter's moon): icy crust over a liquid water ocean — possibly more water than Earth has! ENCELADUS (Saturn's moon): geysers of water vapor confirm a liquid ocean below ice. TITAN (Saturn's moon): liquid methane lakes — could life use methane instead of water? VENUS: harsh now, but its CLOUDS might host microbial life. EXOPLANETS in habitable zones: thousands found, hundreds being studied.
Pick a Target
Look up "Europa Clipper" or "Mars Sample Return" — both upcoming/active missions searching for signs of life. What are they looking for? When will they get results? Living through the era when humans first detect life beyond Earth could be amazing.
Astrobiology asks one of the deepest questions: are we alone? With every mission, every discovery, we narrow the unknown. The answer would change everything.
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