There are good reasons to think that Earth and Mars
originally formed a single planet outside the orbit of Jupiter. Early in Solar System history, Jupiter’s powerful gravitational field pulled this planet past the gas giant. As the planet neared Jupiter, tidal friction heated it to the melting point, and Jupiter tore Mars away from Earth, leaving the Pacific Basin and an array of evidence on both planets. Earth and Mars then sped off into the inner solar system.
How Do We Know This?