Related by context. Frequent words. (Click for all words.) 59 greenish brown 59 salt crystals 59 streambeds 58 powdery sand 57 erosional 57 decaying vegetation 57 waxy substance 57 granite boulders 57 icy crust 56 coarse sand 56 hydrothermal fluids 56 silty 56 polar craters 56 chalky white 56 quartz sand 55 igneous rock 55 pebbly 55 loess 55 tannic acid 55 rotting vegetation 54 Martian dust 54 sandstone formations 54 silts 54 calcite 54 powdery 54 lunar soil 53 regolith 53 coquina 53 mussel shells 53 hardened lava 53 caliche 53 lava tubes 53 dune 53 sand 53 Meridiani 53 marl 53 dense canopy 53 lakebed 53 naturally occurring mineral 53 iron oxides 53 sedimentary rock 52 volcanic rock 52 sediment 52 limestone 52 soils 52 crushed limestone 52 abraded 52 goethite 52 calcareous 52 clasts 52 acidic soils 52 silica 52 Valles Marineris 52 glacial till 52 brownish gray 51 basalt 51 lithosphere 51 corrugations 51 sandy 51 stippled 51 windblown dust 51 mudstone 51 planetesimals 51 rugged cliffs 51 decomposed granite 51 basaltic 51 olivine 51 lava rocks 51 heavily cratered 51 oceanic crust 51 oxidise 51 hardpan 51 tussocks 51 ejecta 51 granite cliffs 50 brownish red 50 alternating layers 50 sulphates 50 greenish gray 50 martian atmosphere 50 crystallinity 50 sandy soil 50 scarps 50 silt 50 lava flowing 50 polar vortex 50 carbonic acid 50 Asbestos fibers 50 thin layer 50 silicates 50 sooty mold 50 crust 50 stalactite 50 silicate 50 sparse vegetation 50 tiny specks 50 roadbeds 50 rock outcrops 50 absorbs carbon dioxide 49 stalactites 49 topsoil