Science/Medicine : The Atmospheric Debate

A widely publicized study showing the oxygen content of Earth’s atmosphere has dropped sharply since the era of the dinosaurs was disputed last week at the American Geophysical Union meeting in San Francisco.

But the author of the original study, Yale University geochemist Robert Berner, insisted his findings are correct in showing Earth’s air 80 million years ago contained 32% oxygen, compared to 21% today.

Both Berner and Scripps Institution of Oceanography geologist Harmon Craig, who presented his contradictory study, measured the gas content of bubbles trapped in amber, which is yellow-colored, fossilized resin from ancient trees, a substance different from watery tree sap.

The finding was significant because it purportedly was the first direct look at Earth’s atmosphere during the era of the dinosaurs, and because scientists had always thought the atmosphere then had about the same makeup as it does today. Oxygen sustains animal life on Earth.

But Harmon said that when he and Scripps chemist Yoshio Horibe crushed 80-million-year-old Canadian amber, they found it contained no oxygen.