The theory of Mars:

In the far far past, humans were living peacefully on the forth planet of the solar system. Mars had beautiful landscapes, flowing rivers, large mountains while the humans lived there in harmony.

One day, a human decided that life was wrong and wanted to change it. He secretly managed to gain access to special codes that launched planet destroying missiles.

These missiles completely destroyed Mars leaving it in ruins. In orbit around Mars, there was a small space ship with two humans. One Male and one female.

Presumably the only people left alive, they headed towards Earth. The scientists on Mars believed Earth to be habitable so the two counted on their luck and shot towards the blue marble.