extraterrestrial life alien life SETI exoplanets cosmological hypotheses cosmic mysteries extraterrestrial intelligence NASA life on earth origins of life habitable zone exoplanet life life building blocks life super telescopes technosignatures more tags breakthrough listen planets Enceladus Saturn solar system life molecules potentially habitable exoplanets Wolf 1061 ET Kepler DNA space projects cosmic megastructures tabby star moons space missions extraterrestrial fast radio bursts panspermia early earth