music; ambience: ice core drilling
To learn what the climate of the Earth was like in prehistoric times, scientists are drilling into the ice sheets of Antarctica. Trapped within the deep layers of ice are bubbles of gas that are half a million years old. The challenge is how to drill without contaminating your samples. I’m Jim Metzner, and this is the Pulse of the Planet.
“Contamination is a big issue when we work in these deep icy systems.”
John Priscu is with the Department of Land Resources and Environmental Sciences at Montana State University at Bozeman.
“When we’re trying to reconstruct paleohistory, in the ice about ten percent of the volume is gas, and they’re in little bubbles inside the ice. You can actually see them. You bring the ice up, you get rid of the outer part that may be contaminated or have micro cracks in it, and then we basically crush the ice sample in a vacuum chamber and extract the gases out of it. Now, another source of contamination that’s really bugging us right now is the microbial contamination. We’re studying this very deep ice that has refrozen into the bottom of the ice sheet. And we do not want to contaminate these samples with bacteria from the surface, so we’ve developed some very elaborate techniques to decontaminate the ice. First step is we use sterile stainless steel scrapers, kind of a crude method, and we scrape away a few millimeters from the outer edge. And then we start doing sterile melts where we will actually wash the core with a Clorox bleach to kill anything, and plus it melts it away. And we go through four steps to where we’re right down to the middle of the ice core. And that is what we call our real sample. This is very precious ice. I hate to see it happen, but we melt away or scrape away half of it and throw it out, before we get what we call a real sample.”
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