From russet reds to mellow yellows, fall colors are spreading across the Carpathian Mountains in Eastern Europe. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite observed the changes along the semi-circle shaped mountain range from October 5, 2018 (left) to October 14, 2018 (right).

The Carpathian Mountains are the second largest mountain range in Europe, spanning five countries; more than half of the range is located in Romania. The mountains are home to a large population of brown bears and lynxes, as well as one of the largest undisturbed forests in Europe. The region is a top destination for viewing fall colors.

Every autumn, the leaves on deciduous trees change colors as they lose chlorophyll, the molecule that plants use to synthesize food. Chlorophyll is not a stable compound, and plants have to continuously produce it—a process that requires ample sunlight and warm temperatures. When temperatures drop and days shorten with the changing seasons, levels of chlorophyll do as well.

Chlorophyll makes plants appear green because it absorbs red and blue sunlight when it strikes leaf surfaces. As concentrations of chlorophyll drop, the green fades, offering a chance for other leaf pigments—particularly carotenoids and anthocyanins—to show off their colors. Carotenoids absorb blue-green and blue light, appearing yellow; anthocyanins absorb blue, blue-green, and green light, appearing red.

NASA Earth Observatory images by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kasha Patel.