Red snow puzzled the ancient Greeks, too

What would you think if you saw a large patch of red-colored snow while hiking in the mountains? Perhaps someone spilled his cherry soda?

It may be "watermelon snow." And while this snow is red on the ground, it did not fall from the sky that color.

This puzzled people for centuries. Two thousand years ago, the Greek philosopher Aristotle mentioned red snow in his writings. In the 1800s, scientists thought it was caused by mineral deposits staining the snow.

Today, researchers say that watermelon snow's color moves upward from the ground. It's caused by any of about 350 species of "snow algae" that thrive in freezing water and melting snow.

Brian Duval, a microbiologist at the Massachusetts Department of Environmental Protection in Worcester, studies watermelon snow. He says that it's not just the color, but the odor that gives watermelon snow its name. "It does have a faint smell of watermelon," he says. He warns people against tasting it, though.

The color comes from brilliant red pigments that protect the algae against ultraviolet rays from the sun. As soon as the snow starts to melt, the microscopic algae "swim" to the surface of the snow using a pair of slender tails.

Snow algae are widespread, but don't bother looking for watermelon snow in your backyard. It is generally only found at elevations of 10,000 feet or more.

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