Lunar Capture

Origins of the Earth's Moon

Background

Several models for the formation of the Earth-Moon system have been carefully delineated by scientists over the past hundred years. The model presented here is not a new origin model but instead is an insertion of an additional, though later step or preferably “event” into the history of the Earth-Moon system. This event could have followed any of the accepted origin models. This secondary event, however, has significantly contributed to the history of the Earth-Moon system. It will be shown that evidence for this event is wide spread on both the Earth and Moon.

The Binary, Fission and Collision models are three of the four primary models of lunar origin. The first two models have the Earth and Moon forming out of the original solar nebula. The Collision Model places the event of formation of the system in the very earliest years just as the Earth is reaching its final form. The Capture Model, the fourth model, in its’ classical sense, views the Moon as a planet orbiting the Sun which is then brought into a geocentric, or Earth centered, orbit. Unlike the other models, Capture, could have potentially happened at a later time, independent of the actual formation of the Earth.

The Close Approach Lunar Model presented here, though favoring a “Gerstenkorn” type capture event, is not particularly wed to any one origin model. It is theoretically possible that any of the four primary origin models for the Earth-Moon system could have resulted in the secondary heating event described here. Regardless of how the Earth-Moon system formed, the  CALM assumes that the Moon was orbiting the Earth some 4 plus billion years ago. This is a treatise on the subsequent evolution of the Earth-Moon system.

The CALM investigates the possibility that both the dark spots on the Moon (mare) and the continental flood basalts on Earth could have been caused by the same event. EarthriseWe know when Earth’s greatest flood basalts were formed (at the P-T Boundary 250 million years ago) because we have Earth’s geologic table readily accessible. Is it possible that the mare were formed around the same time by the same forces? There are similarities between lunar flood basalts and the Earth flood basalts that have long intrigued lunar observers. With this premise in mind, the dating of the lunar mare becomes very important.

Dating of the Lunar Mare

Prior to the Apollo mission scientists were limited to visual inspection of the Moon from Earth. The cratering dichotomy between the dark lunar mare and the bright lunar highlands was particularly revealing. The highlands are cratered so intensely that it is difficult to identify one crater from another whereas the lunar mare is very sparsely cratered. Scientists counted the craters on the freshly formed mare and used their best approximation of the current cratering flux, the rate of meteorite impact, to obtain ages for these fresh secondary lunar surfaces. Pre-Apollo crater dating of the lunar mare using this method set the age at less than 1 billion years old and possibly as young as 700 million years. (2) Since the mare had far fewer craters than the highlands, it made sense that it was much younger.

Scientific Inquiry Alters its Course

Apollo 14Once the Apollo mission brought back rocks from the Moon, isotopic dating drastically revised the age of the mare to more than 3 billion years. This re-dating of the mare after Apollo caused an abrupt change in the direction of scientific inquiry. Rather than resolving a number of lunar origin mysteries, as expected, this paradigm shift instead created new contradictions and deepened existing questions, especially as we learn more about cratering on Mars and other planetary bodies in the solar system.

But what if the isotopic dating is wrong? It is important to point out that there was no real debate over the lunar mare dating. The isotopic dating was accepted carte blanche. It is at this exact point that lunar science lost the scent of the hunt. The scientific literature clearly shows that the hunt for the answers to the origin of the Moon was to only become more confused as time proceeded. Ultimately the greatest scientific disappointment of the Apollo program was its failure to settle the question of how our Moon came to be.

Compared to the engineering/technology effort that brought us to the Moon, the earth science of the time was still rather primitive. If we had known then what we know now the conclusions of the Apollo program may have been quite different. Plate tectonics, the dinosaur impact extinction, tidal heating (volcanic activity) in the solar system, and planetary cratering including secondary cratering, were all in their embryonic form at the time of the Apollo missions. It was unlikely that scientists could put the whole picture together at the time without these missing pieces of the puzzle.

Did you know?

Two rather important papers by two of the most important lunar scientists (3,4) were published just as the new isotopic dates from Apollo were being released and contain apologies as footnotes because they were still using young 1 b.y. crater dating ages of the lunar mare.

The Model of Intense Bombardment (MIB)

All current lunar origin models, including the most widely accepted collision model, do not attempt to answer the lunar mare dating question and generally accept the isotopic dating. What the isotopic dating did not do was change the reality of the low number of craters found on the mare. The model of intense bombardment was constructed in an attempt to reconcile the low crater count findings, once thought to indicate a young mare, with an ancient formation of the mare as now proposed by the isotopic dating. The MIB did this by assuming an early and intense bombardment of the Moon’s highlands during a brief period prior to mare formation, followed by very low cratering as seen on the mare since then.

The Model of Intense Bombardment

  • Ancient placement of mare formation
  • Crowds pre-mare cratering into first tenth of lunar history
  • Based on isotopic dating of Apollo mare rock

If we apply the MIB to the Moon then of course we must also apply it to the entire solar system. However, recent findings on Mars make it more difficult to support the MIB and bring the isotopic dating into question.
Receding Moon

Mysteries Solved

The historical lunar orbit suggests that the Moon approached the Earth at sometime less than 1.3 to 1.8 billion years ago. If the Moon and Earth got close enough to each other, the close gravitational interaction of these two massive planetary bodies would have caused tidal heating in the same time frame on both the Earth and Moon, resulting in the simultaneous formation of the lunar mare and Earth’s continental flood basalts.

Mysteries in the Earth-Moon System
  • The Moon does not orbit around the Earth’s spin axis as would be expected.
  • The Moon is retreating from the Earth
  • The Moon is tidally locked to the Earth, ie. Always shows the same face.
  • The Earth has an unstable rotation full of wobbles and processions.
  • The Earth is tilted 22 1/2 degrees.

If we are willing to consider the possibility that the isotopic dating is not accurately dating the lunar mare and consider a more recent formation of the mare, things start to fall into place and anomalies in the Earth-Moon system begin to be understood. Earth’s unexplained wobble and axial motion, the Moon’s tidal lock and retreat from the Earth, modern plate tectonics, Earth’s continental flood basalts, and the Permian Extinction all can be explained by a gravitational interaction between the Earth and Moon.