There are Several Terraforming Candidates in Our Solar System

Usually, the moon and Mars are the only planets that come to mind when discussing terraforming. Mars is about as Earth-like as the solar system will allow, and the moon is nearby. However, they have cast their net a little further and identified a few candidates, all of which are in our small region of the galaxy.

Of course, Mars is everyone's first preference, but Venus is also a possibility. It initially seems like a bad decision. The temperature is above 800°F, and the atmosphere is 90 times more dense than on Earth.

The planet does, however, have a lot of magnesium and calcium, which, if exposed to CO2 during a terraforming endeavor, may store it. The mood might be changed to a liveable level by adding a few extra components.

Callisto, a moon of Jupiter, has also been proposed as a location for terraforming. The atmosphere could then be made habitable by Jupiter's radiation once the icy surface has been warmed. If you add some bacteria, the environment will be suitable for human existence.

Also suggested as a potential moon for terraforming is Titan. The moon has a plethora of resources that leave the Earth in the dust, therefore it would be a job and a half. Titan is thought to have hundreds of times more hydrocarbon reserves than Earth.