During the war with Tiamat, Mars acquired a hollow moon that could be weaponized in a way that I should not at this time explain.
After the massacre (created by the massive bomb explosions set off on Mars by Tiamat) the surviving Martian royalty called on their allies to help them build an Android army.
The spies from Tiamat reported this to the leaders of Tiamat who decided to turn the protective grid — that the Builder Race had previously created to protect this area of the galaxy — into a weapon of mass destruction. They overestimated their capabilities, however, and it backfired, exploding their own planet and stripping the atmosphere away from Mars.
The piece of Tiamat that wasn't reduced to rubble — the origin of the asteroid belt — was shot out to the position between Venus and Mars and became the Earth. The few remaining inhabitants of the two warring civilizations were transported to the Earth, after millennia of the planet being prepared to sustain life. The Earth was then called 'Bad' (The Place of Death).
To be continued...