Step 4: Fire railgun for approximately a crapload of years, changing Ceres' orbit to collide with Mars.
If you get the math Really Quite Spot On, you may be able to slow Ceres while putting the ice projectiles on a highly elliptical orbit that will also hit Mars. Get the final collision right as well, and you could spin up Mars a bit (closer to 24hr days, though I think I'd like 28 better TBH), or slow it's orbit down a bit.
It'd probably take a couple centuries, and the cool down period might take the same, but when you're done you've got loads of water, a touch more mass, and a great little bootstrapped planet.
Step 2: Build Very Large Railgun™
Step 3: Make Ice Block Harvesting Robots
Step 4: Fire railgun for approximately a crapload of years, changing Ceres' orbit to collide with Mars.
If you get the math Really Quite Spot On, you may be able to slow Ceres while putting the ice projectiles on a highly elliptical orbit that will also hit Mars. Get the final collision right as well, and you could spin up Mars a bit (closer to 24hr days, though I think I'd like 28 better TBH), or slow it's orbit down a bit.
It'd probably take a couple centuries, and the cool down period might take the same, but when you're done you've got loads of water, a touch more mass, and a great little bootstrapped planet.