Even though humans have pondered the moon since the first of us looked skyward, there is still much we don't know about it.

“That will permit scientists to retrace the geological processes that shaped the Moon from its start as a ball of molten rock, which gradually cooled off by releasing its internal heat into space.

It shows the underground plumbing system that provides molten and partly molten rock to the magma chamber beneath the Mount Rainier volcano in Washington state. The scale at left is miles depth.