Aristotle is believed to be one of the first to give a written account of red snow or watermelon snow, over 2,000 years ago. He attributed the redness of the snow to the colour of worms and larva of an insect.
According to modern-day scientists, it is an algae species, Chlamydomonas nivalis chlamydomonas which exists in the snow in the polar and glacial regions and carries a red pigment to keep itself warm.
Algae contain chlorophyll (green pigment) as well as a red carotene layer in their cells which mixes with the green colour to cause snow to look like “raspberry jam”.
The intensity of the redness increases with the dense presence of the algae.
The darker tinge leads to more absorption of heat by the snow. Subsequently, the ice melts faster. The melting is good for the microbes that need the liquid water to survive and thrive but it is bad for already melting glaciers.
This layer helps the algae to protect themselves from the sun's ultraviolet radiation.
These algae change the snow’s albedo that is, the amount of light or radiation the snow surface is able to reflect back.
