(20 kg) of ice would be needed today for the same study.
Researchers are now seeking even older ice in Antarctica, hoping to find some dating back as far as 1.5 million years.
Because krypton-81 (and krypton in general) is quite rare in the atmosphere, using the gas for dating requires a lot of material — 220 lbs.
(100 kilograms) of ice, in the case of the Antarctic ice-dating study that the researchers published in April 2014 in the journal Proceedings of the National Academy of Sciences.
These ice samples hold clues about the ancient climate and atmosphere at the time when the snow fell.
Far from the glaciers of Antarctica, krypton-81 has also been used to date amazing old groundwater in the Sahara Desert.
Carbon-14 is great for dating organic objects that date back tens of thousands of years, but many elements of the Earth are far older, Buizert said.
He and his colleagues have used a krypton isotope, krypton-81, with a half-life of 230,000 years to date ice cores in the Antarctic back to 120,000 years old.
This timed decay creates an atomic "clock," not unlike carbon-14, a radioactive element with a half-life of about 5,000 years.(The oldest Antarctic ice ever found fell as snow 800,000 years ago.) Bubbles in the ice trap atmospheric gases as they were when the snow fell, Buizert told Live Science.By measuring the levels of krypton-81 and comparing them to the current atmosphere, researchers can use the known rate of decay of the isotope to determine the ice's age.Tweet You know how some people have that “Sartorial Elegance” gene?You know the one where you can just randomly choose clothes out of the tumble dryer and look like you have walked off a catwalk in Milan?
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These lasers can produce a pulse of energy 500 times as strong as the entire U. electrical grid in just four-billionths of a second, according to Chemicool. Those experiments were conducted in 2009; since then, researchers have boosted the laser-driven speeds to 1,180 km/s.