In the book of Job you will find the phrase : And the morning stars sang together. This refers to the first generation of super massive stars that formed after the 300,000 years matter-radiation decoupling period. These MONSTER stars quickly went supernova and began the heavy element seeding process. Their shock waves also created the "soap bubble" texture of galactic formation. Searching for these first stars is at the very edge of observation limits right now. We KNOW they were there, but they haven't been SEEN yet(extreme Z).
As to iron 56, that's at the bottom of the nuclear force binding energy curve. It is a ball of Fe56 nuclei at the core of a supernova that gets hammered into a neutron star or black hole. You knew that didn't you? The heavier elements are created in the explosion but some 299 out of 300 energy units of a supernova go into the neutrino burst of the core getting hammered into a sea of neutrons(from protons).
It's a complex subject and the writer doesn't have a full grasp yet of all the facts of astrophysics. As to this nonsensical Impact-Splash theory, another illustration of right brain off the wall theorizing vs reality. We wouldn't even BE here as water rich critters if a mars had hit the earth 4.4 billion years ago : no OCEANS! Where did the earth's OCEANS come from? The clue is in Gen 2:6.
See my bio page. ..... 8<)