Terraforming Mars presents profound ethical, legal, and scientific challenges requiring structured analysis. This paper introduces exoethics, a novel framework integrating principles of planetary dignity, precautionary stewardship, distributive cosmic justice, life-centered ethics, and governance. It evaluates terraforming proposals through case studies, addressing issues such as planetary protection, biological contamination, and corporate monopolization. The paper highlights gaps in current space law, emphasizing the need for regulatory evolution and responsible planetary stewardship. As humanity stands on the threshold of extraterrestrial transformation, ethical foresight and international collaboration are essential to ensuring Mars’ future aligns with the highest standards of sustainability and justice.