Volcanism on the Moon

left|thumb|Rima Hyginus, an eminent rille, in selenochromatic format thumb|Rimae on the floor of the lunar crater Gassendi (crater)|Gassendi, from [[Apollo 16.]] thumb|Mamers Valles rille on Mars. thumb|Rima Ariadaeus is categorized as a straight rille (graben) and is over 300 km in length. thumb|Hadley Rille at center is a sinuous rille visited by the Apollo 15 mission. thumb|Detail of part of Hadley Rille

lunar valley

sub-surface tunnel on the Moon, believed to have formed during basaltic lava flows

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