The 12th Planet, by Zechariah Sitchin is about alien landings on Earth, starting about 500,000 years ago. It makes references to the book of Genesis of the Bible, and the clay tablets of ancient Sumer. First published in 1976, the book makes some remarkable statements about the composition of the solar system, and the origin of mankind on Earth. 

The 12 planets are: the Sun, Mercury, Venus, Earth, Earth’s Moon, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, and Marduk. Having 12 bodies in the solar system is important religiously, according to Sitchin. There seemed to always be a Pantheon of 12 gods and goddesses in every culture including Sumaria, prior to the more recent ideal of monotheism. The 12th planet has an orbit like a comet. It orbits around near the sun once every 3,600 Earth years. It travels in the outer reaches of the solar system during most of its orbit. In spite of this, the planet is warm and habitable, probably from radioactivity in its surface. Marduk is about the size of Neptune. It may be a brown dwarf.

Marduk is the name usually used for the 12th Planet in the book, the 12th Planet, although this planet is often called Nibiru. Nibiru, comes up from the south, once an age, and crosses the planetary plane between the orbits of Mars and Jupiter. The plane of Nibiru’s orbit is retrograde and at right angles to the orbits of the other planets. Far in antiquity the 12th planet collided with Tiamat, (the planet that once existed between Mars and Jupiter) dragging a big piece of it and its Moon to Earth orbit. There was originally an empty space where  Earth and its Moon are now.

The rest of Tiamat’s mass (about 4 times the earth total) created the asteroid belt. The planets, other than Earth, were fully formed and most of them already had life on them during the time the earth was forming. The evolution of mankind and agriculture on Earth were advanced by tutoring from, and breeding with, an advanced alien culture from the 12th Planet. Homo sapiens on Earth would have taken much longer to develop had it not been seeded by the Anunnaki from Nibiru. Agriculture, and its many domesticated plants and animals would have taken much longer to develop if Earth wasn’t visited by an advanced culture and gifted with its domesticated plants, trees and animals. 

When Nibiru is close to Earth, the Nephilum (or Anunnaki) make their way to Earth using rockets. They mine our precious metals for themselves (or force us to do it.) Many or most of them leave and return to Nibiru by the time their planet is gaining momentum Southward, after its passing around the sun. When it is not in the lower solar system, Nibiru is difficult or impossible to see, because it hides in front of the bright stars of the milky way. The  lifespans of the Anunnaki are longer than ours, but any children or grandchildren they leave behind eventually become indistinguishable from the rest of us. 

According to Zechariah Sitchin, in the 12th Planet, every reference to God, Elohim, or Yahweh in the book of Genesis is actually a reference to a space alien from Marduk. These aliens are the gods. The obvious source material for the book of Genesis in the Sumarian clay tablets is unabashedly polytheistic, with gods discussing and arguing among themselves, while Genesis has apparently been edited to make it appear as if there is only one god.

I do not agree that space aliens are gods. They are humans like us, but coming from an advanced culture when earthlings were still relatively primitive may have made them appear godlike. That being said, there is a real God and He is Spirit. I needed to remind myself this while reading Sitchin, because every biblical reference to God, and the Sumarian references also, are interpreted as referring to aliens. 

The “gods” wanted laborers to work the precious metals mines in Africa, so they manipulated the humanoids on Earth at the time to be more like themselves. Although there was a genetic modification described, the easiest way to modify the humanoids of Earth at the time, the Homo Erectus, into beings with enough intelligence, communication ability and manual dexterity for mining and other tasks, was for the male aliens to impregnate the female humanoids. Soon there were modern humans in Africa, Sumaria and elsewhere, used as laborers by the aliens. A couple, Adam and Eve, were placed in the garden of Eden near Sumaria (Iraq). They were there to care for the plants and trees in the garden. They were asked not to eat the fruit of the tree of knowledge but they did anyway, realized they were naked, and were banished from the garden. 

One of the appearances of Nibiru was associated with severe flooding. That appearance was approximately 11000 BC. and caused, first droughts and food shortages, then massive flooding and solar disturbances, during the approximately 1000 Earth years while the planet was close. Atlantis was destroyed in 9577 BC, during that same time of upheavals. Subsequent appearances of Nibiru (and the Anunnaki) were associated with rapid improvements in human culture: rapid advances in pottery approximately 7400 BC, a sudden Sumarian civilization developed around 3800 BC. The last appearance was around 200 BC, and the next is expected approximately 3400 AD.

The book was interesting to read. The points made, although controversial, were very convincing. A PDF is available online as a free download: https://www.booksfree.org/zecharia-sitchin-the-12th-planet-pdf-free-download/