Microgravity Impairs Sperm Navigation

A new study using a 3‑D clinostat to simulate microgravity found mouse and human sperm retain motility but lose directional navigation, and mouse egg fertilization fell ~30% after four hours; adding progesterone partially restored navigation. The researchers will test intermediate gravities (Moon, Mars) to see if effects scale or hit a threshold. — If microgravity or reduced gravity meaningfully lowers fertilization or early embryo development, plans for permanent lunar/Martian settlements face biological, ethical, and policy constraints about reproduction and population sustainability.