Good questions, I love looking at this kind of stuff. Either way, wonderfully interesting
I want to know what these things/structures are on the moon that are casting shadows?
The most accepted reason for the moon always showing us one side:
Tidal Friction:. The Earth's gravity pulls on the closest tidal bulge, trying to keep it aligned with Earth. As the Moon turns, feeling the Earth's
gravity, this creates friction within the Moon, slowing the Moon's rotation down until its rotation matches its orbital period exactly, a state we
call tidal synchronization. In this state, the Moon's tidal bulge is always aligned with Earth, which means that the Moon always keeps one face
Other planets raise tides on their moons, too, so almost all the moons in the Solar System are tidally synchronized. There's even one planet that is
sychronized to its moon! Charon, Pluto's moon, is so large and so close to Pluto that the planet and moon are both locked into the same rotational
rate. The Moon slows the Earth's rotation, too, but at a very slow rate, increasing the length of the day by a couple of milliseconds each century.
source - curious.astro.cornell.edu...
Info From NASA on our Solar System's moons:
Usually the term moon brings to mind a spherical object, like Earth's Moon. The two moons of Mars, Phobos and Deimos, are different. While both have
nearly circular orbits and travel close to the plane of the planet's equator, they are lumpy and dark. Phobos is slowly drawing closer to Mars and
could crash into the planet in 40 or 50 million years. Or the planet's gravity might break Phobos apart, creating a thin ring around Mars.
Jupiter has 50 known moons (plus 16 awaiting official confirmation), including the largest moon in the solar system, Ganymede. Many of Jupiter's
outer moons have highly elliptical orbits and orbit backwards (opposite to the spin of the planet). Saturn, Uranus and Neptune also have some
irregular moons, which orbit far from their respective planets.
Saturn has 53 known moons (plus 9 awaiting official confirmation). The chunks of ice and rock in Saturn's rings (and the particles in the rings of
the other outer planets) are not considered moons, yet embedded in Saturn's rings are distinct moons or moonlets. These shepherd moons help keep the
rings in line. Saturn's moon Titan, the second largest in the solar system, is the only moon with a thick atmosphere.
In the realm of the ice giants, Uranus has 27 known moons. The inner moons appear to be about half water ice and half rock. Miranda is the most
unusual; its chopped-up appearance shows the scars of impacts of large rocky bodies.
Neptune has 13 known moons. And Neptune's moon Triton is as big as the dwarf planet Pluto and orbits backwards compared with Neptune's direction of
Pluto's large moon Charon is about half the size of Pluto. Like Earth's Moon, Charon may have formed from debris resulting from an early collision
of an impactor with Pluto. In 2005, scientists using the Hubble Space Telescope to study Pluto found two additional, but very small, moons. The little
moons Nix and Hydra are about two to three times as far from Pluto as Charon and roughly 5,000 times fainter than Pluto. Eris, another dwarf planet
even more distant than Pluto, has a small moon of its own, named Dysnomia. Haumea, another dwarf planet, has two satellites, Hi'iaka and Namaka.
source - solarsystem.nasa.gov...