Impact Theory 
 Death Star 
 Super Nova 
 Verne Shot 


Pros for Supernova Theory


Cons for Supernova Theory

Note: The theory was disproven using isotopic studies. Along with Ir being created in a supernova, there is also Plutonium-244 created (a relatively short lived isotope of plutonium). Pu-244 is not found on the Earth and if found on our planet, its source would definitely be cosmic. Analysis of the boundary layer clay sediments show no signs of Pu-244. If the Ir did need come from a supernova then it should have been accompanied with Pu-244. Therefore the theory has been disproven. Some scientists argue that this alone is not enough proof; and there is not enough data or knowledge about supernovas to conclusively prove or disprove this theory. While others argue, the absence of Pu-244 is conclusive enough. As is always the case in Geology, the debate rages on.