Mars has 635,000 craters one km in diameter or larger....
Mars has six craters 400 km in diameter. Hellas Planitia is 2300 km in diameter and 9 km deep indicating an impact by a dense object approximately 300,000 km in diameter, or 20% of the Sun's diameter.
Planet X, or Nibiru, the claimed long orbit brown dwarf of our solar system may be real and the cause of Mars, and previous Earth extinction events.