Terraforming

What Mars would likely look like if it were terraformed.

This is what Venus would look like if it was terraformed.

Terraforming is the process of modifying a planet's environment to make it more like Earth's. Longterm terraforming efforts on Mars and Venus have been proposed.

Terraforming in Science Fiction

In science fiction, the term can apply to any effort to modify a planet's environment, even if the goal is to make it resemble another alien world rather than Earth.