Today begins our last dive – however this one will be a dosey.  We are planning on about 54 hours of bottom time for this dive.  We will be mapping and collecting rocks and sediments, as well as making heat flow measurements.  We had to completely re-configure Jason’s dive basket to accommodate all the rock boxes we wished to bring.  We’ll see if we find as many rocks as we have baskets!

Our second to last dive, which ended last night, went seamlessly.  We were again pumping fluids for our fluid program people, and also did some pressure data downloading from Hole 1383C.  We also got some great news about “the B Hole”, Hole 1383B:  pressure data indicate that this CORKed observatory is officially sealed!  There is no way to tell this definitely based on just visual observations that it looks like it installed properly – you need the pressure data to see the difference between bottom pressure prior to sealing and borehole data after sealing.  The data are conclusive on this front and we are all thrilled.

We are making plans for Cinco de Mayo – this will mark the end of our dive series and seems like a good enough reason to call for celebration!  We are planning a BBQ and piñata.  The piñata will be constructed of materials we have on hand and fashioned as a CORK.  Not just any CORK this will be Hole 395A.  This is the CORK that we decapitated during installation operations during Expedition 336 last fall.  There was a failure when we tried to unhook from the wellhead and we simply sheared the head right off that CORK.  So since we broke that CORK once so we might as well break it again in celebration in part to the successful installation of the B Hole.  Pictures to follow!

We are back in the water and pumping the heck out the seafloor. Yay our favorite activity! Which brings me to our fave theme sound for these CORKing operations:

“Letting the days go by, let the water hold me down
Letting the days go by, water flowing underground
Into the blue again after the money’s gone
Once in a lifetime water flowing underground….

Water dissolving and water removing
There is water at the bottom of the ocean
Remove the water, carry the water
Remove the water from the bottom of the ocean…”

—Talking heads

Yes that is what we do out – remove the water and carry the water and yes there IS water at the bottom of the ocean – below the bottom of the ocean in fact.

Its looking like we will be able to get all of our major objectives completed out here, with the completion of this dive. Oh sure there is still a lot more to do – mapping, more rock collecting and of course more fluid samples – but in a pinch we’d be just fine with what we’ve accomplished.

I’ve talked a lot about rocks and fluids but we also have a sediment program out here. Part of it is in compliment to the sediment coring that we did onboard the Joides Resolution last fall. This is because the technique we use on the drill ship, advanced piston coring (APC) fails to recover the upper most meters of the sediment pile. Here, we use short cores barrels that are operated by Jason in order to capture that delicate sediment – water interface. Cores are then profiled in-situ for oxygen, and otherwise are processed for shore-based chemical and biological analysis. We are also making heat flow measurements. Understanding the heat flow helps us to constrain the fluid flow underneath the pond. And that is pretty much the sediment program. It does keep things interesting to have different sample types to deal with – don’t want to get bored! Not that there is much likelihood of that.

One of our fluid sampling devices, the “fast-flow OsmoSampler.”

Another one of our fluid sampling devices, the “geomicrobe sled.”

Yes, very much so out here at North Pond. We’ve so far had one flying fish commit suicide on deck and other than that we are really alone out here. There are not even contrails in the sky – planes do not make it over North Pond. Gives me pause sometimes to think about the fact that we are 5 days from anywhere out here. For this reason, the German research council requires that we sail a doctor. This turned out to be pretty handy last time I was out here on the Merian – we had a number of medical mishaps – but this time we are so far (knock on wood) in the clear we little more that a common cold that has been circulating to report.

We may be alone out here but Jason is never alone at the bottom of the ocean. Jason is tethered to Media, his somewhat homely wife. Media takes up the slack of the ship heave and also always has her eye on Jason down there. They are in a marriage of necessity, and it is also quite useful to have a birds eye view of Jason during operations.

We’ve been holed up for a couple days –weather delays. We are very ready to dive tomorrow and will have a very long dive planned. The list of operations we have planned is daunting, but necessary. We are just past hump day now, or the mid point of the cruise. We have still many critical operations to complete before we can call this an official success, but I’m not worried that that day is coming soon. We try to get all of our most important operations out of the way first, so that if anything happened – to the ship, the science party, the ROV – we’d still have our most important tasks completed. Treat each dive as though it were potentially the last, it the motto we operate by out here!

One of our major objectives for this cruise is to get a better geological context for the North Pond vicinity.  This is accomplished in part by mapping – we are mapping from the ship every night all night – and accomplished in part via our rock sampling program.  I’ve already mentioned how much I like rocks, as a biologist.  Yesterday one of our scientists Sam Hulme was doing logging operations in the van.  Logging is basically sitting with a computer and taking notes of what all is happening during the dive.  We pre-program the computer for certain categories of operations.  Such as geology operations, biology operations, and etc.  Sam asked me how it is that I could classify rocks as biology samples?  I pointed out that of course they are biology samples!  Home to millions and millions of the tiniest life forms on the planet, the mighty microbes.  Sometimes I feel a bit like Horton from Horton hears a who, standing up for the existence and importance of microbiota that thrives in and on the rocky matrix that makes up most of Earth.  But though I see rocks through a biologists eyes, I have to acknowledge that they do of course play an important, if not critical role in developing an understanding of how our planet formed, and in the case of our objectives out here, how North Pond formed.

Yesterday we got some tremendous rocks from the flanks of the pond.  Tremendously cool but also tremendous in size.  Two of them so large they barely fit in our sample boxes on Jason, and then barely fit on my rock sampling box.  Needless to say there was plenty of sample for both geological and biological examinations and analyses.  Wolfgang wasn’t quite sure how to classify these rocks – he’ll have to spend a bit of time really looking closely at them to figure this out.  To me they look a bit like breccia – a mixed up aggregate of different lithologies that are brought together by tectonic forces.  Wolfgang was quite pleased with our takings, as was I.  Particularly because these rocks broke up fairly readily, despite their massive size!

Today is a slow day for me but a busy one for our fluid sampling program people – Pete Girguis, Tina Lin, Oliver Hakka, Brian Glazer, and Ulli Jaekel.  We are spending most of the day operations with Jason pumping fluids – we will collect fluids in sample bags, do some in-situ filtration, and collect samples into gas-tight samplers from Hole 1382A.  We’ll also be making in-situ electrochemistry measurements on fluids to get an idea of the presence and concentration of different redox sensitive analytes – chemical compounds that can either accept or donate electrons.  After a long day of fluid sampling our fluid people will be up most of the night processing samples.  But that will complete our operations for this site – we’ll get some video of this hole then move over to Hole 395A (only 50 meters away) for some more video logging and then say good bye to Site 1382 till next year.

I will have some work to do this evening because we are recovering an OsmoSampler from the wellhead of 1382A.  This was deployed along with my FLOCS last fall during Expedition 336.  So Beth Orcutt and I will have to break down the FLOCS and process these samples once the OsmoSampler comes up on the mini-elevator.  It is exciting to recover experiments from the bottom of the ocean!

I am still basking in the glory of our successful CORKing operations.  So I thought I’d take a few minutes to explain in more detail what CORKs are and why we bother with them.

CORKs were originally conceived of for hydrogeological and geophysical studies of the seafloor.  Basically scientists wanted to take an open hole into hard rock basement and seal it up so that conditions would resume to “pre drilling” in terms of the hydrological state of the rock formation.  The reason to do this is that whenever you drill into basement, creating a hole that can communicate with the overlying seawater, communication is exactly what happens.  For example, when you first drill a hole, you do so by pumping surface (cold) seawater into the borehole.  Introduction of this cold water into a warmer basement formation introduces a perturbation to the system.   Often times a warm formation that would normally expel hydrothermal fluids will turn around and instead suck in seawater due to this perturbation.  Sometimes the hole may turn around again and begin expelling fluids from the borehole but in either case, this is not representative of the native state of the basement.  So the idea is to patch that hole and allow the system to rebound.  The original designers of the CORK put pressure loggers into the sealed hole in order to monitor conditions in-situ to figure out what the real signal of the formation was – overpressured, underpressured – as well as monitor pressure as a function of geophysical events such as earthquakes.  Its like putting a stethoscope onto the heart of the oceanic crust.

Meet the FLOCerS

After these original designs, it became rapidly recognized that these CORKs could be used additionally to collect fluid samples in-situ to monitor the biogeochemical state of the formation as well.  These fluid sampling systems are called OsmoSamplers and use an osmotically-driven pump to collect a continuous record of fluids that can then be analyzed to get a picture of how the chemistry of the borehole changed and equilibrated as it returns to its native biochemical state.  Finally, along come the microbiologists.  The microbiologists, myself begin one of them, want to use these sealed boreholes as active experimental chambers, to look as how communities of microbes populate these hard rock habitats.  We ask questions such as “who is there and when are they there?”; “what kind of minerals do different microbial populations prefer?”; “how does the population ecology change over time?” and “what is the effect that these microbes have on chemistry and mineralogy of the formation?”.  The systems that we use to study these questions are called FLOCS for FLow through Osmo Colonization System.  Out here on the ship then, a lot of our preparations involve getting these OsmoSamplers and FLOCS ready for deployment.  We have 2/3 of our installations done and just 1/3 left to go.  The hard work involved in Osmo and FLOCS prep is almost done!