This is Scientific Americans, 60-Second Science, I'm Karen Hawking.

Wintering in the northernmost regions of Alaska is no walk in the park.

It's cold and dark and sometimes snowy, but that didn't stop dinosaurs from nesting

there during the Cretaceous period.

Dinosaurs were not only just living in the Arctic 70 million years ago in what's now

northern Alaska, but they were actually capable of reproducing there as well.

Patrick Truckenmiller, the University of Alaska Fairbanks, and the director of the University

of Alaska Museum of the North.

In discovering that they were reproducing there, it has an important implication that strongly

suggests that they were actually year-round residents in the Arctic.

Now, the Arctic wasn't as chilly then as it is today, but it was below freezing.

It was 10th dipping down to around 14 degrees Fahrenheit, occasional bouts of snowfall,

and of course, four months of winter darkness.

If living in those conditions seems daunting, so was obtaining the study samples.

In order to get and reach our field sites, we actually have to drive from Fairbanks about

500 miles north up to Prudo Bay in the oil field.

From there we board small planes and helicopters and we fly out to our field site, and then

we put together a couple of boats, and then we use the rivers up there as our highways.

When they spot a rock that looks particularly promising, usually in a bluff or cliff

face along the river, they climb up and start collecting sediment, which then gets hauled

back to the lab to be processed and examined.

We wash it, we screen it, we sieve it, and we collect and save every particle larger than

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