A final challenge to any hypothesis is the weight of supportive evidence, or in this case - similar circumstantial or factual examples. Throughout the project I have looked for what material gave weight the possibility of the Earth having a second moon - be it captured, opposed to another formed through impact (debris) accretion. 

  The size of the body that struck the Earth heavily suggested a Mars size planet striking ours, and which has been discussed and is not in my mind in dispute. By weight of current (professional) evidence, it does strongly favour that our moon came into being as a result of, first impact then through the process of gradual accretion.

  The analysis of Mars two moons, Phobos and Deimos, provides a case in study by comparing relationship to their actual size and mass to the planet itself. These moons themselves, long believed to have been captured into the planets orbit (from the asteroid belt between Mars and Jupiter) therein stands favourable for a moon the size of Miranda having been captured by the Earth itself.

  It has been determined that Phobos is drawing nearer to Mars at a rate of approximately five metres every hundred years, as well as recognizing its decaying orbit, the moon is also speeding up in this process - the inevitable (secular acceleration) results when a body moves into a tighter orbit around its primary. It is anticipated that Phobos will crash into Mars between 40 and 70 million years from now, whether the moon remains in it current solid state until it impacts is open to conjecture - it may well be torn apart earlier by tidal interactions with the planet - if torn apart prior, Mars could acquire a minor ring system produced by the resulting debris.

  Taking this comparison further, the moon Charon (when likewise) compared to the physical size of it primary Pluto pairs up well with the Earth and Moon. The recent discovery of two additional moons surrounding this ninth planet provides some weight to the fact (in similarities) that these orbiting moons provide circumstantial evidence for the possibility of our planet having once had a second moon ? For Pluto, its open to debate whether these moons formed by accretion or are simply captured Kuiper Belt bodies.

  I have proposed the theory that the planets five major extinctions had been caused by the breaking apart of a captured moon similar in size and mass to that of Uranus's moon Miranda which I believe orbited Earth for approx. 800 million years, before the eventual gravitational tug of the primary and the Moon forced it to fracture - its elliptical orbit periodically (based on the density of pieces) falling into similar decaying orbits like Phobos - causing the periodic extinctions.

  Throughout the project I've touched on all five of these major extinctions giving additional coverage to the Cretaceous-Tertiary extinction 65 million years ago - believing this may well have been the final piece of the moon to fall to Earth. Or could there be another piece ?

A simulated view of the Earth, Moon and  broken up second moon orbiting the planet

  Without the aid of these major extinction's, life as we know it on Earth today would have been much different. These impacts wiped out huge numbers of species, giving advantage to those that could adapt to the changing global conditions. The impacts represented a significant loss of biodiversity - though recoveries happened reasonably quick on a geological time scale at least.  For some species these changing conditions provided advantage while significant disadvantage to others, assuming that the surviving life forms migrated to fill the previous habitats and resources occupied by those that went extinct.

  The discovery of the layer rich in Iridium; which as discussed earlier - is found in high concentrations in extraterrestrial bodies such as asteroids and comets. The impact crater at Chicxulub dating back 65 million years is believed have been generated from a major impact body heavy in it (atomic No 77), which dispersed this material throughout the planets atmosphere when the impacter vaporized. Also from the same period,  the discovery of a heavy soot layer indicating evidence of widespread forest fires. In essence, the impact had global significance.

  It obviously therein raises the question; if a moon had actually broken up and fell to Earth in several large pieces over hundreds of millions of years, then why is there not five distinct layers of Iridium in our geological history ?

  If we can (for the point of discussion) accept a second moon had been made up along the same lines as Miranda, then perhaps this moon itself was also made up of differently amalgamated materialized constituents (perhaps the majority of pieces lacked Iridium) and having remained in there original state due to failed accretion, resulted in only one impact leaving this element significant in our geological history.

  The Earth continues to this day to be struck periodically from space - as these two examples indicate; June 30th, 1908, an explosion occurred in the skies over Tunguska, Siberia.  This huge explosion happened between six-to-eight kilometers above the ground, the resultant shockwave laid waste to a vast region of pine forest over some 2,150 square kilometers, felling more than 60 million trees. In 1972, an estimated 1000 ton object skimmed upon the edge of Earth's atmosphere over the Grand Tetons National Park in Wyoming, and then skipped back out into space; somewhat like a skimming-stone off water.

  What these incidents actually reveal is that the Earth still remains a virtual dartboard from extraterrestrial bodies. There is absolute evidence that there is literally millions of ice, rock, iron and various other amalagments of debris still in circulation around solar system.

  So when can we expect the next huge impact ? There is no doubt from today's observations that there's ample candidates lurking around just outside our comfortable atmospheric cocoon !

  Throughout this research, I have looked for possible celestial examples to support the second moon hypothesis. The reader has seen that moons can be captured - like those orbiting Mars. There is the example of the 470 km un-accreted moon (Miranda) orbiting around Uranus. The example of Charon accreted from a collision with Pluto - while recently the discovery of two additional moons. How did the Mars size object impact on the Earth ? It had to have had an elliptic orbit - the same perhaps has Pluto shares with Neptune. Although these to planets cannot collide due to their respective orbital plan, That Mars size planetoid had to have shared a dissecting orbit with Earth - so why not the suggestion of a captured moon !

  Is it possible for a moon that size (470 km) to have been captured by the Earth?

  The moon was likely captured and drawn into an elliptical orbit; with the Earth possessing (even at that time) a thick and widely extended atmosphere, the friction may have slowed down the passing body enough for the planets gravity to hold it in orbit. As mentioned above, initially the captured body 'would' have followed a pronounced elliptical path around the planet, but due to the moon fracturing - it was never taken into a circularized orbit.

  In the end, the reader will have to make their own judgement on the merit of this theory; and whether these mass extinctions resulted from impacts of a fractured moon.

  Perhaps this rogue moon could be termed - 'a Genesis facilitator'.

  Even the 'strangest theories' do sometimes lead to serendipitous discoveries.

Karina Hall
May 2006