Related by context. Frequent words. (Click for all words.) 67 latitudes 54 polar regions 52 equator 51 Arctic tundra 50 infrared wavelengths 50 Northern Hemisphere 49 tropics 49 Little Ice Age 48 warmer climates 47 altitudes 47 Red Planet 47 arctic 46 aurora 46 Arctic 46 Antarctica 46 auroras 46 equatorial Pacific 46 hydrothermal vents 45 northern hemisphere 45 troposphere 45 albedo 45 sunspots 45 extrasolar planets 44 distant galaxies 44 Arctic Circle 44 equatorial 44 wintering grounds 44 polar orbit 44 polar 44 sunspot 44 warmer temperatures 44 colder climates 44 brown dwarfs 44 sunlight 44 Earth orbit 44 geomagnetic field 43 colder 43 cosmic rays 43 winter solstice 43 rocky planets 43 aurora borealis 43 Meridiani Planum 43 warmer 43 comets 43 ringed planet 43 brown dwarf 43 ionosphere 43 exoplanet 43 overwinter 43 Mars Odyssey 43 UV radiation 43 Martian surface 43 meteor showers 43 Arctic Ocean 42 vitamin D deficiency 42 Antarctic 42 Migratory birds 42 distant galaxy 42 Enceladus 42 Martian 42 permafrost 42 cold climates 42 Mars 42 boreal forests 42 XMM Newton 42 NASA Cassini spacecraft 42 warm climates 42 higher elevations 42 exoplanets 42 glaciation 42 moon Titan 41 planets 41 snowpacks 41 martian 41 planets orbiting 41 temperate 41 daytime temperatures 41 greenhouse warming 41 Sedna 41 atmospheric circulation 41 elevations 41 total lunar eclipse 41 cold winters 41 Perseids 41 Daytime highs 41 abundances 41 volcanism 41 seasonal affective disorder 40 summer solstice 40 temperatures 40 redshift 40 vernal equinox 40 GLAST 40 deciduous trees 40 ice melts 40 Holocene 40 tundra 40 Tibetan Plateau 40 quasars 40 Daytime temperatures 40 Overnight lows