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Sally Walker wonders where have all the fossils gone?

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While the seafloor below Antarctic sea ice has plenty of life, core samples from layers of sediment below the surface have very few fossils. AAAS Fellow Sally Walker is among the scientists trying to discover what happened to them. (Photo: Marsha Walton)

Even though Sally Walker's first science experiment was technically a success, it did not get great reviews.

"I used to draw on my walls in my bedroom. I was around five or six, and I made a crayon remover. I used my mother's Chanel N°5, mixed with some olive oil," she laughs."I was so proud of it, but my mother wasn't, because I used all her perfume."

Those early do-it-yourself skills have certainly paid off. Walker often finds herself conducting experiments using improvised materials in the coldest place on Earth—Antarctica. "It's amazing what you can do with hand warmers, duct tape, and bungee cords!" she says.

A professor at the University of Georgia in Athens, Walker specializes in taphonomy: how organisms become fossils. The creatures she investigates are in frigid waters at the bottom of the earth, a sort of "CSI-Antarctica."

"All these sea stars we call starfish, they are moving everywhere. And these scallops are clapping their valves, and fish are moving everywhere and the Weddell seals and the penguins—it's just an amazing place, teeming with life," says Walker.

She studies how organisms—from sea spiders to microscopic creatures called Foraminifera—live and die, and what affects their getting into the fossil record.

She's trying to solve a mystery in a place that's been locked in ice for 34 million years.

While the seafloor below Antarctic sea ice has plenty of life, like those starfish and other echinoderms, core samples from layers of sediment below the surface have very few fossils. Walker is among the scientists trying to discover what happened to them.

"With all this diversity, what happens when they die? Is there ocean acidification? Do the bones and shells decay, and dissolve really rapidly because of these cold, polar waters?"

There's one clue in something called "anchor ice," which may be responsible for relocating some of the sea life.

"Anchor ice forms on the sea floor, around the organisms," explains Walker. "This ice is less dense than the seawater. Eventually what happens is, this plucks everything up off the sea floor.

"What I'm interested in is, how much of this anchor ice gets up to the bottom of the sea ice, then becomes part of the top of the sea ice, breaks up, moves around? And how does that affect what potentially gets into the fossil record?" she says.      

Walker described an "ice scour," a periodic event that may also disturb the process of fossilization: "An iceberg comes in here once in a while and macerates everything into pieces,"she said.

Other possibilities? Predators, such as ribbon worms called nemerteans, could be devouring some Antarctic fauna. Scientists also are looking at parasites that live on shells that could cause them to dissolve faster.

Chemical interactions in the water also are up for future study: "In looking at dissolution, there are some brine-sulfide interactions, some really weird things. I'd love to go back with a geochemist to find out what's going on!" she says.

Adapting her research for the frozen continent has brought unanticipated rewards and challenges, she says: "The polar regions are really keen in our imaginations. It is extremely cold and quiet. There are no smells, no birds, except for an occasional penguin. When you first get to the continent, it is extremely cold, so it's kind of hard to breathe. So nothing really prepares you for an Antarctic experience," she says.

Walker gives much credit for her research success to courageous ice divers. "They are amazing. They helped design equipment for deploying, did all the photography, put out the experiments," she says. "And they first have to drill through 10 to 15 feet of ice!"

Like many polar researchers, facing relentless deadlines and threatening weather, resourcefulness and creativity are essential. "I guess, like a MacGyver, you don't have all the equipment that you need, but you come up with ways of making your experiments work," she quips.

Walker used sewing skills learned at 4-H camp to create protective mesh bags for some experiments. And her team designed a durable stand to secure a sonde device for critical water measurements.

Walker's survival and adaptation skills were put to a harrowing test in October 2000. She was aboard a 747 that crashed in Taipei, killing 83 people onboard.  It took months of working with an emotional trauma specialist to get her back on her feet.

"I had to turn myself inside out, then work my way back out," she says. "The therapy was difficult, but effective.

Walker's experiences in Antarctica may have helped give her the strength to recover. They certainly give her plenty to talk about as she shares her passion for science with people of all ages.

It's not yet clear how the Antarctic fossil mystery will be solved. But Walker's work could lead to new insights about Antarctica's past.

"I'm just really glad to be here," Walker says.

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While the seafloor below Antarctic sea ice has plenty of life, core samples from layers of sediment below the surface have very few fossils. AAAS Fellow Sally Walker is among the scientists trying to discover what happened to them. (Photo: Marsha Walton)
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