Related by context. Frequent words. (Click for all words.) 55 supernova explosion 50 supernova explosions 48 radioactive decay 47 glaciation 47 mass extinctions 47 Earth 47 volcanism 46 biosphere 45 mass extinction 45 planetary 44 supernovae 44 planet 44 Martian atmosphere 44 comet nucleus 44 dwarf galaxy 44 terrestrial planets 44 plate tectonics 43 volcanic eruptions 43 Solar System 43 outer planets 43 planets 43 solar flares 43 Martian surface 43 comets 42 coronal mass ejections 42 Milky Way Galaxy 42 comet 42 Little Ice Age 42 landforms 42 olivine 42 gamma ray burst 42 Eta Carinae 42 rocky planets 42 distant galaxy 42 X ray emission 42 supernova 42 galaxy cluster 42 ejecta 42 astrophysical 41 single celled 41 Martian 41 Orion Nebula 41 Tibetan Plateau 41 planetary science 41 Big Bang 41 multicellular 41 nebula 41 martian 41 single celled organisms 41 Tunguska 41 quasars 41 Saturn rings 41 primordial 40 landmass 40 quark gluon plasma 40 crustal 40 earths 40 cataclysmic 40 Comet Tempel 1 40 primordial soup 40 universe 40 cosmos 40 polar regions 40 Earths 40 supernovas 40 sedimentary rock 40 planets orbiting 40 HD #b [002] 40 organic molecules 40 asteroid 40 Saturn moons 40 galaxy 40 asteroids 39 GRBs 39 cometary 39 neutron star 39 Milky Way galaxy 39 megatons 39 cataclysm 39 galaxies 39 interstellar medium 39 lunar 39 earth 39 Saturn moon 39 extrasolar planet 39 Kuiper Belt 39 planet orbiting 39 neutron stars 39 distant galaxies 39 Late Cretaceous 39 lifeforms 39 earth crust 39 super Earths 39 hydrothermal vents 39 epoch 38 hydrothermal 38 Large Magellanic Cloud 38 galactic 38 volcanic activity 38 heliosphere 38 megafauna