The First Dive to the Lost City
The bizarre hydrothermal vent field discovered a little more than two years ago surprised scientists not only with vents that are the tallest ever seen --the one that's 18 stories dwarfs most vents at other sites by at least 100 feet -- but also because the fluids forming these vents are heated by seawater reacting with million-year-old mantle rocks, not by young volcanism. The field is unlike any seen before, according to chief scientist Deborah Kelley, a University of Washington associate professor of oceanography, and co-chief scientist Jeff Karson, a Duke University professor of earth and ocean sciences. Both have visited fields of black-smoker hydrothermal vents that scientists have been studying since the 1970s.
Now the two scientists who were the first to travel in a submersible to the field after its serendipitous discovery Dec. 4, 2000, are leading a National Science Foundation-funded expedition to map and further investigate the field. The 'Atlantis Diaries' chronicles the expedition returning with 24 scientists onboard an exploration vessel, the Atlantis, during their 32-day expedition that spans April 21 to May 22.
Friday, April 25
Entry by Mausmi Mehta
We awoke on our fifth day of transit to slightly rougher seas, but the sun was still out and the sky was blue. The weather made playing Ping-Pong (a favorite on the ship) a little more challenging.
|Alvin, the submersible to explore the Lost City, on board the Atlantis
At the science meeting today, Gavin introduced us to Alvin's extensive video systems. We then heard from Tim Shank, an evolutionary biologist, about some of the macrofauna that we might see at Lost City. It's not as densely populated with animals like mid-ocean ridge hydrothermal vents often are, at least as far as we know. But there are many different kinds of corals and sponges, and even some amphipods, soft urchins, pink shrimp, nematodes, and polychaete worms.
Then Dave Butterfield told us about the chemistry of the hydrothermal fluids at Lost City. One of the key chemical characteristics of Lost City fluids are that they have very high pH compared to the acidic fluids from mid-ocean ridge (MOR) hydrothermal vents. There also appears to be some hydrogen sulfide present.
The microbiologists on board are all set up and awaiting the first rock and fluid samples from Lost City. We will be preserving samples in order to count the number of cells and use microscopic techniques to determine whether they are Bacteria or Archaea. We will also be freezing samples to extract DNA and RNA once we are back on land.
One of our main shipboard activities will be trying to grow microorganisms from Lost City in tubes containing a growth media, at various temperatures ranging from room temperature to 90 degrees Celsius. Finally, we have two in-situ colonization experiments: the set-up allows for water to flow over rocks in the chamber, and when we recover the experiments a few days later, hopefully there'll be lots of microbes growing on the rocks.
Saturday, April 26
Entry by John Hayes
When the captain welcomed the scientists on board, he said this would be "A long, long, LONG cruise." It certainly has been a long transit from Barbados to our dive site. The distance is 2,597 km and the ship, built and operated for economy, travels at 23.2 km per hour (12.5 knots).
|The mapping project involves global, regional, local and ultimately microscopic--from the great to the small
From our networked computers, we have access to "underway plots" that show the ship's longitude and latitude as a function of time. We've watched the latitude creep steadily northward toward our goal of just over 30 degrees north. We've felt the temperature decline from the tropical warmth of Barbados to this afternoon's 20 degrees Celsius (68 degrees Fahrenheit).
When we arrive this evening at about 6 PM, the first thing we'll do is establish signposts. Thanks to the global positioning system, it is easy enough to know where you are on Earth's surface. But what if you want to know where you are - exactly where you are - when you're more than 700 m below the surface of the ocean? You locate yourself relative to some underwater signposts, and you take care that you know the latitude and longitude of each of those signposts. Our signposts are sonar transponders. If struck by a particular sound - a ping from one of our submarines- they respond with a sound. By listening and sensing the direction and distance to each transponder, the submarine determines its precise location.
Sunday April 27
Entry by Gretchen Früh-Green
The day we have all been waiting for has finally arrived. We are on site, the transponders are in place, and the first dive day has begun.
Almost everyone was outside to watch Alvin being launched this morning at 0800. It is a fascinating thing to watch. The Alvin was rolled out of its hanger, the Avon (a small rubber motor boat) was put overboard, and the "Swimmers," Gavin and Raul, were in their wetsuits ready to unhook the Alvin after it was lowered into the water.
|The rack of transponders for the Lost City expedition on board Atlantis
Kelley and Tim were the first to dive in the Alvin this cruise, and Bruce was their pilot. Those of us left on the ship followed their progress, either through updates given by the bridge or on lighted displays in the labs. After about 1530, we anxiously awaited the horn that signals that Alvin will be surfacing. The horn finally sounded, and the Avon was once again lowered into water. Phil and Gavin were ready as Swimmers this time and Jerry drove the boat.
The Alvin surfaced at a distance in front of the ship and the Avon approached them. There is a telephone just above the hatch on the Alvin, and one of the Swimmers climbed aboard and let the scientists inside know that the ship was coming. It seemed to take forever for the ship to slowly approach the sub, but then we got there and it was towed in and lifted up onto deck. Everyone was excited to know how the dive went and to see the samples that were collected.
Debbie and Tim were pleased with the dive. They got the samples they wanted, and in the labs everyone was suddenly very busy. The first measurements were made on the fluids, and the vent structures were sampled for microbiological studies and organic geochemical measurements.
Mitch photographed all the samples; then each was measured, weighed, and described. Before we knew it, it was time for dinner and a quick science meeting. Tim and Debbie reviewed how the dive went and showed us some pictures of the structures.
Tonight at about 2045 we launched ABE, the Autonomous Benthic Explorer, for a test run. If all goes well it will stay in the water for a few hours and then will be followed by another conductivity- temperature-depth (CTD) run. For the next few weeks, we will have round-the-rock operations, collecting a tremendous amount of data.
April 28, 2003
Entry by Debbie Kelley
It was with a bit of anxiousness and lots of excitement that I climbed back into Alvin for the first time in nearly three years to visit the Lost City Field again. All the planning and hard work was focused into yesterday morning. Mainly I wondered, "Will we be able to find the vents again without hours of wandering around the Atlantis Mountain?" Pilot Bruce Strickrott and biologist Tim Shanks were also on the dive and our goals were to find the field, conduct an initial exploration, and take rock, fluid, and biological samples.
By 0800 Alvin was in the water. With only 25 to 30 minutes of descent time (instead of the typical 1 to 1 1/2 hours in other areas), we had to rapidly stow our gear and get our minds set to explore the field. As the sub was lowered into the water, the windows were engulfed in a familiar wash of bright blue water. Upon descent, this rapidly changed into darkness and small bioluminescent organisms with fantastically diverse shapes floated by the windows. It looked like hundreds of stars on a clear night.
Within about 10 minutes we had come upon the monster tower called Poseidon, the nearly 200 foot tall structure that we had first visited in 2000. We ascended to the top of the edifice and visited two of the active pinnacles where Bruce, using the two manipulator arms of Alvin, obtained samples. With Tim onboard, I got to learn about some of the amazing animals that live around the vents. For example, there are swarms of flea-like critters called amphipods and small shrimp that dart in and out of the field of view.
In many ways the landscape that we visited left me in even more awe than the discovery dive. This area must be one of the most remarkable places on Earth, but it is difficult to describe. The field is extremely complex with vertical spires that rise up farther than you can see, bounded by rock cliffs that extend downward for hundreds of feet. Out of the sides of the cliffs are delicate, snow-white carbonate deposits that look like upturned hands -- each finger composed of numerous delicate intergrowths. In other places along the wall, huge white carbonate pinnacles rise vertically for many tens of feet.
We saw structures that looked like the magic rocks we grew in fish bowls as kids, and encountered gigantic pieces of chimneys that had toppled from above and slid down the steep cliff faces. White intertwining scars marked places of recent venting along the sides of the towers. It was a rare, remarkable experience that I will remember for a long time. We surfaced at 1545 grinning ear to ear, with a basket load of samples.
The anxiousness and excitement for the day, however, had not yet ended because after the dive, the free-swimming robotic vehicle ABE was scheduled for its first dive. After exhaustive testing, ABE was deployed into the waves. Its flashing beacon lit the night as it slowly submerged under the white caps, and ABE dove beneath the seas to begin a night of detailed mapping.
The project includes scientists, engineers and students from the University of Washington, Duke University, Woods Hole Oceanographic Institution, U.S. National Oceanic and Atmospheric Administration, Switzerland's Institute for Mineralogy and Petrology and Japan's National Institute of Advanced Industrial Science and Technology. Collaborators include: Jeff Karson, Duke University, Co-PI and diver during the discovery; Matt Schrenk (an astrobiology graduate student at the UW School of Oceanography); P.J. Cimino (a NASA Space grant undergraduate); and John Baross, also a faculty member in astrobiology and oceanography.