The burden of travelling between Mars and Earth comes from the distance. If the planets were closer, life could spread to Mars more easily, ensuring the survival of the intelligent lifeforms. What would it take to pull the two planets closer each other? How much energy would be required? Would it even be possible to move planets without losing the stability of the orbit? Is this manipulation of orbits possible even in theory?
To give some numeric data, the average orbit radius of Mars from Sun is about 1.5 times the orbit radius of Earth (1 AU). The distance between Mars and Earth varies from 0.5 AU to 2.5 AU. For reference, the distance between Moon and Earth is about 0.003 AU. The orbital period of Mars is 687 days and Earth 365 days. The mass of Mars is about 0.11 Earths.