The late astrophysicist Dr. Thomas VanFlandern had a more compelling though less conventional theory. He called it the “Exploded Planet Hypothesis”, or “EPH” — for more information, see http://metaresearch.org/solar%20system/cydonia/mrb_cydonia/new-evidence.asp
TVF had a consistent model for dealing with certain data, and a possible, still hypothetical mechanism -- but no actual evidence that planets have gone missing, including during the past 10 million years. He also was his own worst enemy, this garbage -- PROOF THAT THE CYDONIA FACE ON MARS IS ARTIFICIAL.