Earth has not always been so hospitable to live. During several ice ages, the planet's surface was almost completely frozen over, creating what has been dubbed "Snowball Earth".

Earth has not always been so hospitable to live. During several ice ages, the planet's surface was almost completely frozen over, creating what has been dubbed "Snowball Earth". Liquid water appears ...

Earth has not always been so hospitable to live. During several ice ages, the planet's surface was almost completely frozen over, creating what has been dubbed "Snowball Earth". Liquid water appears ...

The climate near the equator at the time resembled modern-day Antarctica. Yet even in such extreme conditions, life found a way to keep evolving.

When the Earth froze over, where did life shelter? MIT scientists say one refuge may have been pools of melted ice that dotted the planet's icy surface.