Posted by: adorsk | January 10, 2008

Smokin’ Science

I’m here on the Knorr in the middle of the South Atlantic, floating about 4,000 above the sea floor. This week’s post is about black smokers and AUV robots

Black Smokers

No, I’m not referring to aboriginal tobacco users. Instead I’m talking about one of the main scientific interests of this cruise, hydrothermal vents, aka black smokers. The scientists are hoping to use the AUVs to find and map black smokers.

So what is a black smoker? Black smokers are holes in the seafloor through which hot chemical plumes shoot out into the ocean. They are called black smokers because the chemicals form black columns in the water which look like smoke. Black smokers are commonly found near mid-ocean ridges because there is lots of geological activity just below the crust. The geological activity creates pressure and heat, which forces steam up through the crust. Black smokers are the underwater equivalent of geysirs. Wikipedia has more: Wikipedia on Black Smokers

Scientists are interested in them for a number of reasons. Some scientists want to know how they support animals that survive without light, including tube worms, clams, and shrimp. Other scientists want to know about the chemicals they put out. There are some theories which posit that the chemicals from black smokers are associated with the origins of life. And of course they’re just cool to look at!

But before you can study hydrothermal vents, you have to find them. That’s what we’ve been doing so far on this cruise. Step one is to make a reasonably detailed map of the seafloor. We used the ship’s multibeam sonar system to do this. The map gives you depths and lets you get a feel for the geology of the area. Step two is to look for black smokers with a CTD. The CTD is equipped with special sensors that can detect black smoker plumes. It gets lowered close to the bottom (this is the other reason why you need a good map first), and then towed slowly by the ship. This type of CTD cast is called a ‘tow-yo’, because the CTD goes up and down so that it doesn’t hit the bottom.

Here are some of the scientists looking at the map:

vent field map

The third step is to send in the robots. This is what is special about this cruise. After a target area for black smokers has been identified by the map and CTD casts, the robots are given a target area. Hopefully they will map the entire area with high-resolution photographs and sensor readings.

Send in the Bots

We had our first robot dive last night. Things didn’t go exactly as planned. The first deployment was a bit rattling…the science party and deck crew were doing a test deployment of Puma (one of the robots). As it was being raised back onto the deck, itbumped into the side of the ship. Fortunately it was ok.

Puma then started its first dive. In the beginning it had navigation problems. One of the goals of the cruise is to test how the robots perform with a new navigation system called “LBL” (long base line ) navigation. It wasn’t working for Puma, but she was able to continue her dive.

Later, the scientists weren’t able to communicate with Puma. Finally they got a signal in which made the robot rise to the surface. It didn’t work exactly as planned, but it did get a lot of useful data anyway.

Puma coming out of the water:

Puma Recovery

C & J using a laptop to talk to the Puma over an acoustic modem  (a cat call?)

Cat Call

Ship Life

Ship life has been fairly regular for this cruise. The weather is almost always the same: slightly hazy during the morning and afternoon, then clear during the day & night. Always about 27 deg C (80 F). The time is flying by. There are only 6 more days of science left before we have to steam to Ascension island. The food continues to be excellent. Tonight’s dinner was seafood crepes with ice cream bonbons and berries for dessert.

And the return of the  Friday evening cookout:

Cookout in the South Atlantic

A, our steward, at the grill

a at the grill

S in the science party has been making a great website for the cruise. Check it out:

The ship is expected to pull in to Ascension island on the 17th.  We’ll be there for three days before departing for Charleston, S.C.  Check back in a week or so to find out the rest of the cruise goes.

Thanks for reading.

Miscellaneous Pictures

Robot abstractions

propellor  cat shells robot face

Sunset in the South Atlantic

South Atlantic Sunset


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