The martians were experts at manipulating gravity. They used gravity the way we use hydrocarbon fuels. In fact, to them our combustion engine would be a mystery. Our mastery of creating plastic from the bones of ancient life would be unbelievable.

They knew they had to expand. In fact, it was their highest purpose. To send their seed to other worlds. And their first target was an inner world.

If they were ever to colonize the third planet they would have to move a lot of water. They planned to use the machine to move planetary bodies from the outer solar system to the inner planets. It worked, but it was a slow process. They decided to expand their efforts.

They built a machine to meet their ever increasing power needs. An inner planetary water pump. It would move water between the planets.