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2016 Annual Science Report

Massachusetts Institute of Technology Reporting  |  JAN 2016 – DEC 2016

Executive Summary

Complex Life and Environmental Evolution
Daniel Rothman has been studying the major environmental perturbations in the geologic past,
including those associated with mass extinctions. By transforming geochemical signals to
physical variables, he has found that mass extinctions are associated with rates of environmental
change that exceed a limit imposed by mass conservation in a normal carbon cycle. This work
also suggests that external perturbations of the carbon cycle, such as extensive volcanism, can
excite responses that breach this threshold. The time scale and magnitude of these responses to
perturbation decrease over the Phanerozoic, which may be related to the evolution—-and
strengthening—-of the biological pump. These observations point to a way in which the
coevolution of life and the environment, one of astrobiology’s principal themes, leads towards
increasing stability in both the biosphere and geosphere.

Kristin Bergmann, graduate student Marjorie Cantine and Andy Knoll ... Continue reading.

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