starlord wrote:

I've read some good articles about the forming of our moon, it is not
uniform in make up, the otherside is made up of lighter rock than the earth
facing side. The 'seas' where made from when large impacts happened and it
remelted the vast areas which flooded the area. No Volcanos where ever on
the moon.
(snip)

The apparent lack of volcanism fits with the Earth impact hypothesis
of lunar formation. That hypothesis assumes that the entire lunar
mass was ejected into the vacuum of space in molten or vapor form,
which would allow anything gaseous to be separated from the rocky
material (and either be swept away in the solar wind, or reabsorbed
into Earth's atmosphere), before it coalesced into a moon. The
resultant body would be very deficient in high vapor pressure
materials, so there would be no gas pressure to drive any volcanic
expulsions. If the hardened crust were broken by impact, the surface
would just sink into the lava below the molten subsurface and a new
surface would harden. This is what the Maria look like.

Io is just the opposite extreme, with a great bounty of volatile
material in its makeup, so lots of explosive eruptions.

--
John Popelish