Taken from an oblique angle and looking toward the southwest, this astronaut photograph shows parts of northern Italy, Corsica, Sardinia, the Adriatic Sea, and the Mediterranean. Over part of the Alps, skies are clear, but elsewhere, the view of the land and sea is largely obscured. Bright white clouds cover much of the region, but over northern Italy, the “clouds” are different. There, dingy, gray-blue haze hangs over the Po River Valley.
The Po River, Italy’s longest river, runs approximately 650 kilometers (400 miles) from the southwestern Alps to the Adriatic Sea, passing indirectly through Milan, and through Turin. As Turin is an industrial center of a heavily urbanized region, pollutants often cloud the skies overhead. In fact, northern Italy is one of Europe’s pollution hotspots, and the smog often grows thick enough to be seen from space. Smog in this area is so persistent that astronauts on the International Space Station have photographed other images of it, in October 1997 and February 2003. Recurring accumulations of smog in the Po River Valley, however, result from more than just the industrial emissions from the area around Turin. In this area, smog is often trapped at the base of the Alps by high atmospheric pressure.