It was probably one of the pieces of defunct planets that was supposed to used to build Earth, but somehow it got lost during the creation. When Elohim finally found it, he just threw it down here.
I can buy "stuff" from outside the solar system impacting here; it has happened a lot of times over the eons, including some that had a huge impact, no pun intended.
Spaceship? Not buying it ... wait, maybe it is a spaceship from Kolob, manned by the Moon Quakers, who have come to tell us all the church is truuuuuuuueeee and we can all bear testimony. Or not. :p
I favor the notion that life on Earth sprang from a bilge dump from an RV passing through our solar system during a Spring Break being celebrated by fraternity brothers from at least three different intelligent species, one of which had 8 arms and no legs.