Related by context. Frequent words. (Click for all words.) 59 polar craters 59 erosional 58 stalactite 58 rock outcrop 57 jarosite 57 martian soil 57 spherules 57 rock outcrops 56 lava tubes 56 Gusev crater 56 lunar craters 55 striations 55 Meridiani 55 basaltic 55 goethite 55 meteor impacts 54 basalt rock 54 hydrothermal activity 54 steam vents 54 landforms 53 wavelike 53 clasts 53 promontories 52 icy crust 52 Valles Marineris 52 igneous rock 52 iron oxides 52 polar vortex 52 stratiform 52 scalloped edges 52 fumaroles 51 tuffs 51 andesitic 51 ridges 51 basalt 51 sandstone formations 51 bluish tint 51 outcrops 51 graben 51 subcrop 51 loess 51 siliceous 51 subglacial 51 rock outcroppings 51 steep ravines 51 lotus leaf 50 sedimentary rock 50 NASA Spirit rover 50 scarps 50 termite mounds 50 granite cliffs 50 escarpments 50 waxy substance 50 stippled 50 chalky white 50 Martian dust 50 Olympus Mons 50 olivine 50 Saturn moon 50 calcareous 50 volcanic rock 50 interbedded 50 calcite 50 gullies 50 greenish brown 50 magnetic susceptibility 50 igneous rocks 50 chalcedony 49 granite boulders 49 landform 49 sulfide minerals 49 cumulus clouds 49 mud volcanoes 49 striated 49 glacial till 49 NASA Opportunity rover 49 manganese oxide 49 stalactites 49 ridging 49 boulders 49 sparse vegetation 49 crustal 49 iridescence 49 gossanous 49 silicates 49 flower petal 49 hydrothermal breccia 49 pyroclastic 49 corrugations 49 rocks 49 interstellar clouds 49 whorls 49 geologic 49 vuggy silica 49 moon Enceladus 49 sawtooth 49 cirrus 49 meteorite impacts 49 lithosphere 49 snail shells 49 surficial