Lets say the carving of this asteroid was commissioned after the destruction of Tiamat. It would follow the same logic as Enki ordering a lion be carved after the great flood. The Annunaki or Progenitors could have ordered it to denote who was responsible for Tiamat's destruction or to have a record of what species occupied that planet. Its reflective characteristics was compared to charcoal which must be unusual for an asteroid. Maybe it contains a library or record of what happened in the solar system. Another theory is the Reptilians carved it into the shape of a human skull to instill fear into the occupants of Mars, Tiamat or Earth. 2015 TB145 - Wikipedia