Terraforming Mars may be more realistic than scientists once thought

Terraforming is the process of reshaping a planet or moon so it can support humans and other Earth-like life. In theory, that means changing an alien world's atmosphere, climate, and surface to more closely resemble Earth's by adding oxygen, creating stable bodies of liquid water, and producing temperatures suitable for life. Mars has long been considered the leading candidate, with proposals ranging from releasing greenhouse gases to warm the planet to using microorganisms that could slowly generate oxygen over many centuries.