The Black Sea Just Turned Turquoise: Here’s What NASA Found

For most of the year, the Black Sea looks exactly like its name suggests: a wide, dark stretch of water separating Europe and Asia. But on 22 June 2026, NASA’s PACE satellite captured a very different scene, with large sections of the sea glowing in pale turquoise and milky blue.

The image came from the Ocean Color Instrument aboard PACE, a NASA mission built to study oceans, the atmosphere and ecosystems from orbit. In the picture, swirling turquoise patterns spread across much of the Black Sea’s surface, shaped by currents and shifting conditions below.

According to NASA, the colour change is most likely tied to blooms of coccolithophores, microscopic phytoplankton coated in plates made of calcium carbonate. When large numbers of these organisms multiply at once, sunlight reflects off their plates and turns the water a pale, almost milky shade.

These blooms are usually invisible to the naked eye on an individual level, but together they can stain enormous areas of ocean visible even from space. NASA notes that late spring and early summer are typically when coccolithophores become most abundant in the Black Sea.

The sea’s appearance does not stay the same across the year. At other times, diatoms, a different type of phytoplankton with silica-based shells, tend to dominate instead. Their presence usually darkens the water rather than brightening it, producing a very different look from the turquoise conditions seen in June.

NASA says these colour shifts reflect changing biological activity within the sea itself rather than any change in the water’s composition. Coccolithophore blooms are also useful to scientists, since their brightness makes them easy to track by satellite, helping researchers monitor marine ecosystems across areas that are difficult to sample directly.

NASA Earth Observatory/by Michala Garrison