
1) Apollo 11 sighting 2) German girl name 3) German geological term 4) Lunar cleft 5) Lunar feature 6) Lunar surface feature 7) Lunar trench 8) Lunar vale 9) Lunar valley 10) Moon marking 11) Moon surface feature 12) Moon valley 13) Sight from Apollo craft 14) Valley for Selene 15) Valley of the moon
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https://www.crosswordclues.com/clue/rille

Rille (German for `groove`) is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length. However, the term has also been used loosely to describe similar structures on a number of planets in the Solar Sys.....
Found on
http://en.wikipedia.org/wiki/Rille

• (n.) One of certain narrow, crooked valleys seen, by aid of the telescope, on the surface of the moon.
Found on
http://thinkexist.com/dictionary/meaning/rille/

any of various valleys or trenches on the surface of the Moon. The term was introduced by early telescopic observersprobably the German astronomer ... [1 related articles]
Found on
http://www.britannica.com/eb/a-z/r/50

Hadley Rille on the southeast edge of Mare Imbrium A long, narrow furrow, usually with steep sides and sometimes meandering (known as a sinuous rille), formed either as an open channel in a lava flow, or as an underground tube carrying hot lava that collapsed as the lava flowed out. Rilles up t...
Found on
http://www.daviddarling.info/encyclopedia/R/rille.html
Rille (rĭl)
noun [ German
rille a furrow.]
(Astron.) One of certain narrow, crooked valleys seen, by aid of the telescope, on the surface of the moon.
Found on
http://www.encyclo.co.uk/webster/R/83

An elongate trench of cracklike valleys on the moon's surface. Rilles can be sinuous and meandering or relatively linear structural depressions.
Found on
http://www.evcforum.net/WebPages/Glossary_Geology.html

Grooves in the Moon's surface which resemble canals or canyons.
Found on
http://www.moonconnection.com/moon-glossary.phtml

One of several trenchlike, or cracklike valleys up to several hundred km long and 1-2 km wide commonly occurring on the Moon's surface.
Found on
https://pds.jpl.nasa.gov/planets/special/glossary.htm
No exact match found.