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CLOCKWISE FROM TOP LEFT: YUZHEN YAN (2); PRESTON COSSLETT KEMENY/PRINCETON UNIVERSITY DEPARTMENT OF GEOSCIENCES

Ancient Antarctic

Ice Is Discovered

❯

AMERICAN GEOSCIENTISTS have discovered

2.7 million-year-old ice — the oldest ever by

1.7 million years, researchers announced at

the annual Goldschmidt conference in August. The

sample was drilled from Antarctica’s Allan Hills

“blue ice” area, where unusually old glacial ice is

closer to the surface, making it more accessible.

Trapped bubbles can offer snapshots of past

carbon dioxide and methane levels. This latest

sample reveals Earth’s climate history beyond

a critical benchmark when, 1 million years ago,

glacial cycles shifted from 40,000- to 100,000-

year periods. Understanding temperature and

greenhouse gas shifts through those ice ages could

also offer insights into Earth’s future climate.

 KATHERINE MAST

Bubbles trapped in ice (above) hold ancient air, giving

geoscientists like John Higgins of Princeton University

(right) a way to date glacial ice in Antarctica. He

and his team drilled at three sites, hauling tents and

equipment, such as a drill bit filled with an ice core.

The team camped at Allan Hills (below), where old ice

is unusually accessible.