Related by context. Frequent words. (Click for all words.) 55 extraterrestrial 55 habitable planet 55 habitable planets 54 astrobiologists 54 moon Europa 53 Earthlike 52 spacefaring 51 extraterrestrial civilizations 51 icy moons 51 moon Enceladus 51 alternate universes 50 Higgs particle 50 Lake Vostok 50 Gliese #g 49 Martian rocks 49 alien civilizations 48 planet Uranus 48 Venusian 48 potentially habitable 48 astronomical phenomena 48 WASP #b 48 interstellar 48 rocky planets 48 cosmological 47 alien beings 47 polar craters 47 Hawking radiation 47 planets 47 supersymmetry 47 terrestrial planets 47 Oort Cloud 47 Exoplanet 47 hydrothermal vent 47 planetary 47 outerspace 47 habitable zones 46 graspable 46 invisibility cloaks 46 nanobacteria 46 unknowable 46 galaxy formation 46 dystopias 46 heavily cratered 46 undescribed 46 earths 46 chemtrails 46 lifeforms 46 aurorae 46 ALH# 46 precognition 46 outer space 45 asteroid 45 wormholes 45 undersea volcanoes 45 cylon 45 inter galactic 45 Martian 45 planetary nebulae 45 psychic phenomena 45 ETs 45 Penikett 45 inter planetary 45 nonliving 45 Eagle Nebula 45 Nibiru 45 unobservable 45 transhumanism 44 alien 44 morphologies 44 superstrong 44 plausible 44 Tycho Brahe 44 evolutionary origins 44 flatworms 44 braincase 44 gaseous planets 44 geoid 44 martian 44 extrasolar planet 44 Saturn moons 44 cosmic 44 distant galaxy 44 Gamma ray bursts 44 lunar poles 44 Jupiter moons 44 Extraterrestrials 44 Mini SAR 44 noctilucent clouds 44 methane hydrate 44 gravitational lens 44 intelligent beings 44 cometary 44 quantum gravity 44 art imitates 44 Scientifically speaking 44 super Earths 44 vaguely resemble 44 GRBs 44 moonlets 44 comet tail 43 SIRTF