Formation of lunar rilles

Until recently, I was excited about lunar rilles because the
prevailing theory was that they are collapsed lava tubes of immense
size. Such uncollapsed lava tubes would be ideal places for a lunar
colony and would probably contain condensed volatile cometary
materials including hydrocarbons. However, after viewing many rille
photos, I no longer go along with the lava tube hypothesis. They tend
to have strings of craters along their length that are clearly
collapse features (consistent with the lava tube hypothesis) and go
across many other features including ridges and craters. Sometimes
they both begin and end at high elevations which lava tubes would not
do. There is also no evidence for lava outflows from them and no
evidence of collapse of a lava tube ceiling.
There are some weird theories such as the one that says they are huge
electrical discharge features but I think the real explanation is much
more prosaic; they are simply cracks into which lunar regolith has
fallen. Imagine the moon as having an outer crust of low density and
an inner part that is denser and semiplastic and hot. When this shell
was walloped by an asteroid, it cracked all over. Repeated whackings
made it (the moon) shake and caused the cracked shell pieces to rub at
the edges. This caused the edges to wear and to fall into the crack
where the material heated and became denser and sank. Repeat the
process over a billion years and you get rilles.
This explains almost all of the rille features. Unfortunately, no
lunar lava tubes to explore.

On Jan 8, 6:37 pm, wrote:

There are some weird theories such as the one that says they are huge
electrical discharge features but I think the real explanation is much
more prosaic; they are simply cracks into which lunar regolith has
fallen.

On the other hand, rilles could be river channels for returning
rain water back to the maria.
http://volcano.und.nodak.edu/vwdocs/...s/schr_v1.html
http://volcano.und.nodak.edu/vwdocs/...s/schr_v2.html
Great depths of water shielded maria-floors from cratering
by incoming meteorites.
http://apod.gsfc.nasa.gov/apod///ap001228.html
John Curtis