If you ever hike through the Alps in summer, you might see something strange — patches of snow blushing pink, as if the mountains have caught the sunset.
Locals call it “watermelon snow” because of its rosy colour and faint scent. But this unusual shade isn’t caused by dust or minerals — it’s alive.
The colour comes from microscopic algae that live in the snow. These tiny organisms, called Chlamydomonas nivalis, contain a natural pigment that protects them from sunlight. In winter, they lie dormant, buried under ice. But when the snow begins to melt, the algae wake up, multiply, and tint the snow around them red or pink.
Scientists say the pigment acts like sunscreen, shielding the cells from harmful ultraviolet rays at high altitudes. The red coating also helps the algae absorb warmth — but it has a downside. Darker snow absorbs more heat and melts faster, which means these little organisms may actually speed up melting in mountain regions.
This phenomenon isn’t limited to the Alps; pink snow has also been seen in Greenland, the Himalayas, and even Antarctica. For hikers, it’s a stunning sight — but for researchers, it’s a reminder of how even the smallest life forms can influence an entire ecosystem.
Tiny but tough
The algae survive freezing temperatures, thin air, and strong sunlight.