In the last entry we reviewed the debate currently swirling around the question of how the moon formed. Lunar soil samples brought back from Apollo astronauts show compositions extremely similar to that of Earth, making the standard lore less attractive that a single giant impact striking at a glancing blow produced the Moon.
In the formation scenario presented last time, the Moon was formed as a result of series of smaller impacts. According to the simulations, such a series of events would take a long time to play out. In this case, the Moon's birth certificate would state it to be about 100 million years younger than the Earth.
We can test this hypothesis by going out and measuring the ages of each body. Unfortunately, such age-dating measurements do not help us, as some results show a difference in formation age of 100 million years while others put the Moon at a more contemporaneous difference of only tens of millions of years.
It is not unreasonable to think that the Earth and Moon should have an age separation somewhere in between these two extremes, say of about 60 million years. There is a competing study in which exactly this age difference is forwarded. The researchers of this study assert that such a 'fast' formation of the Moon is actually possible given trace amounts of zircon grains which are most likely to form deep in lunar magma.
Finally, a third competing scenario also makes use of trace components in the lunar composition, this time citing that certain lunar soil minerals are commonly associated with wet environments. In this picture, the early Moon contained water which encouraged the production of the minerals and then later the water escaped into space.
In this growing list of potential stories, the real answer is out there waiting to be discovered. Perhaps very soon we will be confident about how the Moon was sculpted.