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 thirteenth blog post. To track her research ship's current position, click here. To see all her posts, see "60 Seconds in North Pond."

SOMEWHERE ABOVE THE NORTH POND (March 4, 2009)—Four cores in one day! This is our record, and not likely to be repeated. Tomorrow, we must finish operations at 7 P.M. local time to begin our transit back. So we are in the final haul to collect as many samples as possible, which we will keep working on during our transit to Dakar, Senegal.

Everyone is totally wiped out. From deck operations to microbiological and chemical processing, we have all pulled between 16 and 20 hours today. Tomorrow won't be much easier, but from where I stand right now, the three cores we think we can achieve seem much more reasonable compared to four.

It didn't help that we started our day with yet another fender bender. We bent the core barrel fitting and had to switch it out before continuing operations. (These are so-called gravity cores: We are not exactly drilling so much as dropping a long barrel with a big weight on top of it. If the ocean bottom is harder than the core barrel, look out.)

Because we are looking for evidence of water flow under the North Pond, we want to get as deep as possible. The "ultimate" goal is to find the dividing line between rock and sediments, but that is pretty tricky around here and relies on luck to a large degree.

We had been using 12 meters (39 feet) of core barrel, and we had some good success, but the region we are operating in now is too hard for that length. (The longer the barrel, the more likely it is that it will bend.) The clay is really compacted in places and, in addition, there are sandy layers that are like hitting a brick wall.

So, we have had to switch to six meters [19.5 feet] of core length, which worked well for the other three cores. But when your core is half the usual length, you have to do twice as much coring to get the regular length of sample, which is one of the reasons today was sooooo long.

Tomorrow will be easier: Not only will we have just three cores, but it is ice cream day (Thursday). Food traditions are highly regimented on the Merian. Thursdays and Sundays are ice cream with lunch, and cake with 3 P.M. coffee. Sundays are also a big meal day, with formal settings at noon. Saturday noon meal is a stew and Friday dinner is fish.

The only meal that appears to be free of regimen is breakfast, which is eggs to order; pancakes with jam, or rolls; cheese; assorted meats and jams. Two big hot meals a day are a bit much for me, so for dinner I usually opt for the "cold plates" of some salad, meats, cheese and assorted dark breads. The German tradition appears to be a hot meal followed by bread and cheese.

Time to hit the pillow. Tomorrow comes early again!

Photos of scientists working with a probe and of a water sampling device 30 meters below the surface, courtesy Katrina Edwards/USC