Let's say that an advanced civilisation once existed on Mars millions of years ago at a time when water existed in liquid form and that life was abundant on the planet. (Say this civilisation is a Type 1 according to the Kardashev scale)
As the planet approached the lifeless state that it is now, this ancient civilisation decided that it would build a device that would reverse the effects of the planets transformation and revive it into a habitable world.
The device was solidly built and hidden under the surface of Mars and meant to last millions of years. However, due to internal wars over resources, the civilisation collapsed and the device was never activated.
Fast forward to the year 2060 A.D. and a human expedition to Mars has found this device and decided it would activate it.
My question is, what would this device be, how big would it have to be, what would it have to do, and how long would it take, to terraform Mars?
- Could this device give Mars a magnetosphere?
- Could this device alter Mars gravity?
- Could this device create liquid water oceans on the surface?
- What other things would this device have to do?