By Peter Weiss
In the era before multicelled animals appeared some 550 million years ago, extreme cold may have clutched Earth in a death grip for millions of years. According to the controversial snowball Earth theory, the planet swung between deep freeze and feverish heat several times during a 200-million-year period preceding the multicellular explosion.
Offering an alternative to the snowball theory’s ice-engulfed planet, a team of researchers from Texas and Canada now demonstrates that a swath of liquid ocean may have hugged the planet’s midriff even during the chilliest episodes.