People: Astrobiology Graduate Student Directory

Loren Ballanti
Biology

One of the fundamental aims of Astrobiology is to understand the long-term evolution of a biosphere, using Earth as a model for any world on which life may develop. However, our picture of terrestrial life's history is obscured by a lack of primary evidence that spans billions of years, its earliest paleoecology forever inscrutable. Only since the evolution of metazoans large enough to be seen, and having developed the ability to secrete mineralized skeletons, has there been a fossil record of sufficient quality to illustrate evolution over millions of years.

The most striking feature of this history preserved in stone is the periodic occurrence of mass extinctions. While species have a finite shelf life and a constant, background level of extinction persists through time, mass extinctions are catastrophic events that represent severe and prolonged disturbance on a global scale. Working with Peter Ward, I study the most ruinous of these events, the Permian-Triassic cataclysm, a two part disaster that culminated about 251 million years ago with the demise of over 90% of marine species and similar estimated losses on land.

While all taxa clearly suffered at this time, the patterns of survival and recovery reveal a selectivity that is not easily explained away. Thus, I am doing paleophysiology on a variety of marine invertebrates to try and reveal the rules of survival across the P/T boundary by demonstrating differential susceptibility to conditions known to be in play in the late Permian, particularly hypercapnia. Currently, I seek to explain the decline of articulate brachiopods relative to their bivalve molluscan counterparts.

While I am consequently probably well characterized as a marine paleobiologist, such a title fails to capture the essence of myriad related interests and the proper context for thinking about life.