Logging 395A

One of the goals of our visit to 395A was to deploy an experimental logging tool known as the Dark Energy Biosphere Investigative Tool, or DEBI-T, for short. Logging tools are instruments designed to scan a borehole, after it has been drilled, to gain a better understanding of the characteristics of that hole. These instruments are lowered through the drill pipe and into the hole to measure characteristics such as density, porosity and conductivity. The logging in 395A was different in two respects: first, 395A was already drilled, and second, the instrument suite included DEBI-T, an instrument we designed to assess how many bacteria might be within the borehole.

We began logging operations early Saturday morning. We managed to get about 60 meters into the hole before hitting an obstruction that we could not get past. After several attempts, we came back up so that the drillers could use a bit at the bottom of the pipe to push through the obstruction. Afterwards, we were able to go back through the pipe and into 395A to start logging. We finished logging early Sunday morning, a little over 24 hours after we started! Needless to say, we are all tired, but in good spirits because DEBI-T performed well. We’re currently studying all the data to find out how many microbes are living down there.

cleaning the DEBI-t 

Comments

Science Rocks

How long are your days? Do you work at night? Have you ever hit oil? Do the bacteria produce methane? Do you get vacations? Do you have another job? What is the most interesting you ever discovered?
We Love Science!
PCDS science class 7-2

Hello PCDS, We typically work

Hello PCDS,

We typically work 12 hour days on the ship. However, right now I am analyzing all of the data that DEBI-T collected, so the days are a little longer. Normally I stop working around midnight, go exercise (the ship has a gym!) read a book and go to sleep (sounds pretty boring, right?). I get up around 9 and go back to work. I don't normally work these hours, but we're on a ship, and there isn't really anywhere to go.
This particular ship is not designed to look for oil. Indeed, if we ever got a hint that there might be hydrocarbons, we would not drill because the JR is not equipped to handle them. So, alas, no, we've never struck oil.
Some bacteria do produce methane, and there is some molecular evidence from samples that were collected on other cruises that there might be methane producing bacteria in the ocean crust. That is a current area of investigation for several research labs.
Yes, I do get vacations. My job is pretty flexible, so I can take whatever time I need off.
This is actually my "other" job. My real job is to do research for NASA. I work at Caltech-JPL, in Pasadena. The research I do is based in developing biosensors and organic detectors that can be used on rovers or remote sensing probes. We also make handheld devices that can be used to detect bacteria on various surfaces.
The most interesting (scientific) thing I have discovered so far is that we can use our lasers to tell the difference between bacteria that are doing different things. Normally, you need to do things like genetics or proteomics to do that. In this case, all we have to do is shine a laser and we can tell the difference between a microbe that is breathing oxygen and one that is fermenting, for example. What that means is that one day we might have a device that is similar to a tri-quarter. If you don't know what that is, ask your teacher, I'm sure they will know.
Thanks for the questions!

science does rock!

you guys had a lot of questions, so I'm working on getting them answered. check out our Q&A page to see when they get posted: http://joidesresolution.org/node/925

DEBI T : "How do it know????"

Can you explain what sort of instrument DEBI T is? How does the DEBI-T scan a borehole? Does it have sensors or is it a camera of some kind? How does it determine the number of bacteria? Thank you !

Julie K

Hi Julie, DEBI-T is a

Hi Julie,

DEBI-T is a fluorescence-based biosensor. DEBI-T shines a 224nm laser onto the surface and excites the organic molecules that are on that surface. When those molecules fluoresce, the detectors in DEBI-T record that fluorescence. DEBI-T has a small sapphire window that allows the laser pulse to exit the instrument and fluorescence signal to pass back into the instrument. When you use this type of laser, bacteria emit a specific type of fluorescence. That's how we know when we detect a microbe.

DEBI-T has both a camera and sensors. That camera records what DEBI-T is "seeing" so that we have context for what the fluorescence sensors detect. That way, we know how dirty the water was, or what kind of rocks we might have been scanning, etc. The camera uses the same sapphire window to look outside.

DEBI-T works the same way that other logging instruments work. These instruments are lowered and raised in the borehole and collect information as they travel up and down. In DEBI-T's case, the laser shines on the surface and causes the organic molecules to fluoresce. That fluorescence is recorded by detectors in DEBI-T. Because we know where in the borehole DEBI-T is, we know where the different fluorescence signals come from.

Before deploying DEBI-T, we did some calibration tests in the lab. We used known concentrations of bacteria to make a curve that told us how bright the signal would be given a certain number of microbes. In general, the more intense, or bright, the fluorescence signal, the more bacteria there are. We can then use that curve to make an estimate of how many bacteria we might have seen, based on the fluorescence intensity.

Sweet - DEBI-t in action!

Hi Everett! Can't wait to see the results! (Rosalynn, USC)

Hey! Yeah! We're looking at

Hey!
Yeah! We're looking at the raw data now! Hope to have something in a few days.