The Black Sea sits at the boundary between Europe and Asia and connects to the Mediterranean Sea via a chain of waterways. Its surface often appears dark, but each spring and summer it transforms into a striking expanse of swirling turquoise. The OCI (Ocean Color Instrument) on NASA's PACE (Plankton , Aerosol, Cloud, ocean Ecosystem) satellite captured this image (above) on June 22, 2026. ...read more read less