From “How Life Might Have Survived ‘Snowball Earth’” (ScienceDaily Oct. 13, 2011), we learn:
Many scientists believe Earth became a giant snowball two or three times between 800 million and 550 million years ago, with each episode lasting about 10 million years. These all preceded the Cambrian explosion about 530 million years ago, when life on Earth rapidly expanded, diversified and became more complex.
But simple photosynthetic plankton turn up in the fossil record before and after the “snowball Earth” events, leading scientists to wonder how that could happen if Earth’s oceans were completely encased in ice.
Campbell said it is assumed the algae survived these episodes, “unless they re-evolved each time, which creates a whole different problem for evolutionary biology.”
Adam Campbell and fellow researchers think that a Red Sea-like environment might have enabled photosynthetic algae to survive. Snowball Earth is one thing. Icicle life, another. Here’s the paper.