Read more here.
"Snowball Earth" proponents, who say that Earth's oceans were long ago covered by thick ice, explain the survival of life by hypothesizing the existence of small warm spots, or refugia. On the other side, supporters of a "Slushball Earth" say the planet included large areas of thin ice or open ocean, particularly around the equator.
Now, scientists who applied innovative techniques to previously unexamined rock formations have turned up strong evidence to support the "Slushball Earth" side of the decades-long scientific debate.
I'm not so sure that I'd say 'decades-long scientific debate'. Last I heard this was a relatively new hypothesis (as in the last decade).