Related by context. Frequent words. (Click for all words.) 54 Antarctica 48 Antarctic 48 polar regions 48 oceans 47 Arctic Ocean 47 moon Titan 46 polar caps 45 moon Europa 45 Antartica 45 Arctic 44 outer planets 44 Saturn moon 44 polar ice 44 Antarctic ice 44 volcanic activity 43 Red Planet 43 glaciers 43 rover Opportunity 43 Iceland Eyjafjallajokull volcano 43 melting permafrost 43 polar 43 atmospheric carbon dioxide 43 equatorial regions 43 arctic 43 glacial melt 42 Martian surface 42 Arctic tundra 42 Antarctic Peninsula 42 Martian atmosphere 42 Greenland Ice 42 Arctic Sea 42 martian 42 NASA Cassini spacecraft 42 glacial ice 42 Greenland ice 42 lunar surface 41 permafrost 41 comet Wild 41 ocean currents 41 megafauna 41 Meridiani Planum 41 oceanic 41 earths 41 Medieval Warm Period 41 troposphere 41 greenhouse gas concentrations 41 landforms 41 Antarctic waters 41 active volcanos 40 Arctic seabed 40 Beaufort Sea 40 twin rovers 40 Antarctic Ice 40 journal Geophysical Research 40 IPY 40 glacier 40 plate tectonics 40 comet dust 40 ocean 40 equatorial Pacific 40 ice 40 mass extinctions 40 greenhouse warming 40 Tibetan Plateau 40 planet 40 coastlines 40 Earth crust 40 circumpolar 40 continent 40 glaciologists 39 sunspot activity 39 ringed planet 39 Gusev Crater 39 Eyjafjallajökull 39 tropics 39 woolly mammoths 39 emperor penguins 39 Ellesmere Island 39 species extinctions 39 Spitsbergen 39 dust devils 39 active volcanoes 39 Northern Hemisphere 39 comet nucleus 39 volcanoes 39 Serreze 39 cosmic microwave background 39 volcanic eruptions 39 geologically active 39 Earth 39 El Ninos 39 northern latitudes 39 atmospheric CO2 39 snowpack 39 extrasolar planet 39 sediment cores 39 volcanic eruption 39 NSIDC 39 Deep Impact mission 39 Northwest Passage 39 water vapor