Upon some further checking and such, my calcs for the BFRed seem to indicate a yield of 560 gigatons per second. the beam lasts for 7 seconds so this results in 3 teratons, 960 gigatons. Since the Sathanas has four BFReds, this results in a total firepower of 15680 gigatons, or 15.680 teratons.
When I think about it, it's not really a wonder that I think a Sathanas might be able to fight a Star Destroyer. Ignoring the stupid KLUNE WARRS crap and the positively, absolutely HORRID EU, evidence from the movies seems to suggest that warsie ships typically give out single digit teraton yields for their shields and their guns.
Oh and Mars? You want to utterly vape a planet to the point of utter annihilation? Think yottatons. Death Star level.
That kind of firepower is sufficient to destroy a large portion of the planet's mass and scatter the rest.