New Study Points to Extraterrestrial Causes for Past Mass Extinctions

October 23, 2015 – In Monthly Notices of the Royal Astronomical Society a new paper argues that periodic mass extinctions in the past can be linked to comet and asteroid encounters with Earth. The idea of extraterrestrial causes was first proposed by a father-son team, Luis and Walter Alvarez. They hypothesized that a space rock striking the area near the Yucatan Peninsula in Mexico caused the death of the dinosaurs. They provided evidence in the form of isotopic iridium found in space rocks and not formed here on Earth, distributed in rock layers at the boundary between the Cretaceous and Tertiary geological periods. That evidence was disputed by many geologists.

The revival of the Alvarez hypothesis in this new paper provides evidence of correlation between dating of surface impact sites and known extinction events from the geological record. One of the craters is Chicxulub, the one in the Yucatan dated to 65 million years ago. In addition the authors describe five other impact craters that correlate with known extinction events covering the last 260 million years. It doesn’t end there. The authors studied 37 craters, finding eight recognized marine and three terrestrial extinctions to correlate with impact sites, plus two suspects which the authors believe are crater sites that have been poorly dated.

The paper was submitted by Michael Rampino, New York University, and Ken Caldeira, Carnegie Institution’s Department of Global Ecology. The theory is mass extinctions are cyclic caused by the motion of our Solar System as it passes through the mid-plane of the Milky Way. This causes disturbances in the Oort Cloud at the extreme edge of the Solar System leading to perturbations in the orbit of its constituent members who then get pulled into the inner Solar System where some end up striking the Earth.

The graph below illustrates the cyclic nature of these Oort Cloud disturbances and points out the correlation with extinction events catalogued from the geological record.

In their conclusions the authors state that “the hypothesis of periodic extraterrestrial impacts as a contributing cause of periodic extinctions of life, while controversial, is still viable.”