The survival of life through Snowball Earth events

Abstract:

Between 600-800 million years ago and about 2.2 billions years ago there were a number of episodes in which the ocean was either nearly or completely covered with ice (Snowball Earth episodes). These extreme departures from clement conditions are important to understand because in some sense they must represent a failure in the mechanisms that have maintained Earth's temperate climate over the past four billion years. Yet despite this failure it is clear that life survived the Snowball Earth events and may have even thrived as a result of them, either indirectly (through associated rises in oxygen) or directly (through evolutionary pressure). In this talk I will focus on the physical conditions that may have allowed life to survive Snowball Earth episodes, and what this can tell us about habitability more generally. I will discuss the hard Snowball Earth (with the ocean essentially completely frozen over) as well as theories for these glaciations involving regions of very thin ice or open ocean that would allow photosynthetic marine life to survive.