Whether water sits in a lake or a glass of water, Earth’s gravity pulls the liquid downward into the shape of the container it’s in.
But in space, gravity’s effects are different. Objects in orbit are indeed affected by gravity, but they are in freefall, moving constantly sideways while falling toward Earth [Learn more ]. This renders them effectively weightless.
Up there, surface tension shapes water into spheres. Magnetic-like molecules on water’s surface cause the surface to behave like an elastic skin. Each molecule is pulled with equal tension by its neighbors.
The tight-knit group forms the smallest possible area — a sphere.