Editor's Note: University of Southern California geobiologist Katrina Edwards is taking part in a three-week drilling project at the Atlantic's North Pond—a sediment-filled valley on the ocean floor—designed to locate and study what she calls the “intraterrestrials”: the myriad microbial life-forms living inside Earth's crust. This is her twelfth blog post. To track her research ship's current position, click here. To see all her posts, see "60 Seconds in North Pond."

SOMEWHERE IN THE NORTH POND (March 3, 2009)—Today we continue our coring operations, following a night and an extra morning of heat-flow measurements. Heiner Villinger, our chief scientist from Bremen, who doubles as the heat-flow guru of our group, has been very patient with us microbiologists and biogeochemists. He and his group like to generate nice straight lines of complete data sets, and we keep requesting that they drill off-course. This, so we can fill in the data at sites we are particularly interested in and where we need additional measurements.

Then, in addition to that, we ask for more risky drill sites to prod with their highly valued instruments. We did indeed hit rock again today with the heat-flow probe—Ouch! No damage done though, luckily, and our colleagues appear to be taking it in good stride.

Why do we keep running pipe and probes into the rocks, you ask? Really, as I mentioned in an earlier blog, we are not intentionally on a path of destruction just for the heck of it (though seeing a bent coring pipe was kinda cool).

See, most of the water that we know is flowing into the rock beneath the North Pond is probably leaking out from those big mountains around the rim—somewhere. But it is remarkably difficult to figure out exactly where. In fact, I would say it is probably impossible.

Hot vents are much easier to find—not only do they often belch black smoke, but they emit various chemical signals into the water column that scientists can measure far, far away from the vent itself. As with a game of "hot and hotter," the concentrations of those chemicals go up as you get closer to the vents.

But at North Pond, good luck. Chemistry isn't going to help us, and neither is there likely to be a chemical signature that can be detected. It is a "needle in a haystack" kind of problem. But, though we may not ever know all the exit points exactly, if we can figure out the general direction of flow underneath the North Pond, we will have much better confidence that we can place our "CORKed observatories" somewhere near the on-ramp and the off-ramp of the superhighway of fluids flowing underneath.

Now that is a more tractable problem. The heat-flow measurements point the way, and the chemistry of the core samples tells us if we're close to an entry or exit point. We've got one corner of the pond pretty well nailed, and now we are feeling our way around the other warm zone, hunting for evidence. Better find it soon—we only have two more days!

Photo of the Posidonia, an instrument hooked on the line to the coring device (above), and sampling clay and sand (below), courtesy Katrina Edwards/USC