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Dr. Tim Shank is an associate scientist in the Biology Department of the Woods Hole Oceanographic Institution, which he joined in 1999. He earned a B.A. in biology from the University of North Carolina, Chapel Hill, and a Ph.D. in marine ecology and evolution from Rutgers University. His current research focuses on understanding the ecology and evolution of species living on the ocean floor. Shank's lab at Woods Hole investigates deep-sea habitats by studying both the molecular genetics of the creatures that live there and the physical, chemical, geological, and ecological processes that affect them. Shank has participated as chief scientist, principal investigator, or graduate student on over 30 oceanographic cruises using deep-submergence vehicles, including more than 60 dives in Woods Hole's Alvin submarine. His most recent field expeditions include a 2007 remote exploration of the Arctic Ocean's Gakkel Ridge, and a 2009 voyage that successfully sent a robotic vehicle over six miles down to the Mariana Trench, the deepest part of the world's oceans. When he's not on the high seas, Shank is an avid piano player and Revolutionary War buff. Thanks to his line of work, he no longer eats shellfish. "As soon as I began working on marine invertebrates, I found I just couldn't enjoy eating them," he says. |
On August 24, 2009, Tim Shank answered selected viewer questions about the biology of the Gakkel Ridge, the challenges of undersea exploration, and more. Please note we are no longer accepting questions, but see Exploring the Arctic Seafloor and our Links & Books section for more information. Q: Dear Dr. Shank, We know the ingredients of life here on Earth, but what if life on another planet is made up of different chemical building blocks? How do we create tools to sniff out what we're not even sure we're looking for? A: Dear K.S., This is a great question. This reminds me of the story where native North Americans standing on the New England shore did not see the Mayflower approaching land because their minds were not conditioned to "see" a large ship on the water. Scientists have asked whether the search for life should really include alternative forms of life, but if we can't define what that full range of alternatives might be, then how can we search for them? Scientists have considered alternative life-hosting biochemistries that use elements other than carbon (like silica, nitrogen and phosphorous, sulfur, and even arsenic) for its basic structural and physiological functions and/or use solvents (like ammonia) other than water. The problem with these is often either a structural one (ability to maintain a complex atomic configuration) or a reactive one (they react with other elements to break down quickly). The techniques microbiologists use to detect life on Earth, like staining for DNA, sequencing DNA, and culturing microbes in the lab, assume that the target microbes have the normal biochemistry. According to many microbiologists, less than 1 percent of Earth microbes have been cultured—the rest may be considered "unculturable". This means that an alternative form of microbial life (even ones similar to the ones we know) may go readily undetected. Interestingly, astrobiologists refer to these forms of life as "shadow life", and that constructing (and testing) means of detecting this life is particularly more difficult on an Earth contaminated by pollution than on other planets. Biochemists are now thinking that a promising future is to explore extreme environments that are beyond the reach of conventional life, such as ultra-dry deserts, ice sheets, the upper atmosphere, or the hottest hydrothermal vents. The reality is that we can search for the realm of what we do know, at least as a first pass. Q: How soon do you think technology will allow us to go to Europa to look for life under the ice? A: Dear Carolyn, Most estimates suggest that the full technology to deliver a vehicle that will land on the icy surface, tunnel through the 80 to 170 km of ice and deploy itself in the Europan Ocean is more than 15 years away. This is a highly rough estimate in my opinion as this timing in many ways depends on the space exploration priorities set forward by governments around the world. Q: You say in the show that essential ingredients for life include water, rock, and a heat source. Isn't it possible that life as-we-don't-know-it may have formed without, say, water? Have researchers looked into that possibility, and, if so, what have they found? Thank you. A: Dear Joaquin, Yes, some planetary scientists have pondered that liquid ammonia, methane, or hydrocarbons might be capable of incubating the formation of life. As you may know, water has a variety of properties that allow and even promote life, including being a medium (with different phases) that facilitates chemical reactions, the very existence of molecular structures, dissolving byproducts, and the long list goes on. Liquid ammonia is a strong non-aqueous solvent, which could serve as a medium to support life, but it is actually only liquid over a ~30° range, and when it freezes, it becomes very heavy. Methane and hydrocarbons can be highly abundant on other planetary bodies, like forming lakes on Titan. The problem with this is that the temperature at which these exist is more than 100 degrees below zero. Chemical reactions would likely be either non-existent or too slow to support the machinery of life as we can conceive of it. Also, in methane and hydrocarbon, the essential elements of life (as we know it), amino acids, could not freely exist. For these reasons, scientists in general currently believe that life finds water essential. Q: Hi, Tim, Since the expedition, have you learned anything more in the lab about the yellow microbial fluff on the Gakkel Ridge? Is there anything like it other places on Earth? A: Dear Danielle, Yes, we have learned a great deal more. There is a high diversity of microbes living in the mat, many iron-loving. This makes sense given our observations of "rust-colored" alteration of the rocks around the mats. They are relatively different from most other microbial species living at vents along the global mid-ocean ridge system. In general, they resemble closely those microbes found in deep-sea iron-rich environments (similar to the Gakkel Ridge depth of 4000m) in the Pacific. We have a lot more to learn. We still want to know why animal life is not more abundant in the mats if it is an effective food source. This will require additional tests and a return trip the slowest spreading center on Earth. Q: Dear Dr. Shank, What did it feel like to be exploring a place that no one had ever seen before? What were the most exciting moments for you personally during the expedition? A: Dear Anonymous, The thrill of true exploration is hard to put into words. I have been very fortunate to have had many opportunities in my profession to explore unknown places on Earth, and feeling what any of us have felt in a completely new environment (just take a walk in unexplored woods with a flashlight at night). I recently returned from an expedition where we utilized a high-tech robot to reach the bottom of the Mariana Trench, the deepest place on Earth—over 7 miles deep, deeper than Mount Everest is high. Along with curiosity, the thirst and thrill for discovery is what drives scientists to think past what we know. I have had more than 40 research expeditions, and the ones I always love and remember most are those where we drove past the boundaries of the map, past the boundaries of our knowledge. The Gakkel Ridge stands out as perhaps my most favorite because of the challenges we overcame with building new vehicles and making them work with all kinds of solutions (from complex wiring to using C-clamps to hold the hydraulic system together). Most exciting moments? Seeing the most otherworldly and beautiful glassy seafloor terrain I have ever seen. There is no place on Earth that looks quite like the Gakkel Ridge seafloor 200 miles from the North Pole. I once thought that Vasco de Gama, Ferdinand Magellan, and other explorers had found all there was to discover. Not true. The full map of Earth's continents can be made almost daily from satellite images. However, less than 1 percent of our ocean floor has been mapped over the past 140 years. Q: Hi, Dr. Shank, Are scientists any closer to figuring out how life might have begun on Earth, that is, how the very first life-form made the leap from a bunch of chemicals to a single cell? Thanks! A: Dear Tyler, This is a good question and a hard one. I think we "know" more today about the possible and likely conditions, the timing, and the sequence of events that are considered to be the "chemical evolution of life". There are hypotheses and theories presented each year refining and exploring the boundaries of the conditions, timing, and how it might have happened. I am not an expert on this, but I would encourage you read a recent popular article in Discover Magazine that explains some of the most compelling experiments ever conducted in science: http://discovermagazine.com/2008/feb/did-life-evolve-in-ice/article_view?b_start:int=0&-C= Q: Was the fact that the Gakkel ridge is similar to Europa the main reason you guys went there, or were there other reasons to explore it? A: Dear Anonymous, The similarity of the ice-covered oceans above a mid-ocean ridge in the Arctic and on Europa is just one of the reasons why we went there. As an evolutionary biologist, my goal was (and still is) to find out how life living on the deep Arctic seafloor evolved in what we believe to be complete isolation from communities in other oceans. There are very few places in our ocean that we know have been isolated in the past. The Gakkel Ridge has been geographically and oceanographically isolated from other mid-ocean ridges for at least the last 28 to 53 million years. By this time the Arctic seafloor starting spreading (with likely hydrothermal venting activity), [and] the deep Arctic Ocean was isolated to the north Atlantic by a shallow sill or saddle and the shallow Bering Strait. Whatever animals adapted to life in "toxic" thermal springs two and a half miles below the ocean surface did so in isolation, likely resulting in new life forms with novel adaptations. The probability of discovering novel species, physiologies, ecologies, and symbioses (animals living with microbes that would detoxify the toxic fluids) is extremely high. Consequently, exploring for and locating life on the Gakkel Ridge could (and may still) reveal fundamental clues as to how evolution has produced such wonderful biodiversity in our oceans. Q: In the NOVA scienceNOW program, one expert noted that the Gakkel Ridge has been isolated from other oceans for millions of years. How is that so? Don't ocean currents flow all around the globe? A: Dear Mark, In short, it is generally believed that the deep (~4200 meter) Arctic Ocean has been and can be considered isolated in terms of a deep-water connection to the Atlantic or to the Pacific. The Arctic's connection with the Pacific Ocean is narrow and shallow, so the major exchange of water is with the Atlantic Ocean through the Fram Strait. Atlantic surface waters communicate freely and a strong subsurface current brings warm water from the Atlantic into the Arctic basin, [but] exchange of deeper waters is prevented by sills and submarine ridges. The bottom of the Arctic Ocean is very cold and relatively stagnant. So the isolation is due to the shallow Fram Strait, the narrow passage between Greenland and Spitsbergen that serves as a shallow choke point for water getting into and out of the Arctic from the Atlantic. The other major choke point is in the southern Chukchi Sea, which provides only shallow northern access to the Pacific Ocean via the Bering Strait between North America and Russia. Q: What's the deepest you've ever been in a submarine? A: Dear Anonymous, My deepest dive was in the submersible Alvin along the Mid-Atlantic Ridge where we dove to a depth of 3730m (almost 2.5 miles). The deepest that Alvin can currently dive is 4500m, and the deepest hydrothermal vent site we know of so far (just north of the equator in the Atlantic) is 4150 meters deep. Q: What is the strangest thing—animal or otherwise—you've ever encountered on the ocean floor? A: Dear Jacob, I feel I have seen many strange (or at least unusual) things at more than 1 mile down, like a white, freshly-dead "dumbo" octopus the size of a beach ball being devoured by a squat lobster crab; giant (~6 feet long) hydrothermal vent tube worms "Riftia" spawning clouds of eggs and sperm into the water column; two male octopuses (of different species) trying to mate—but in reality, the mere presence of animals like clams, mussels, and tubeworms bathed in hydrothermal vent fluids (toxic to you and me) never ceases to amaze me. Also, at these same depths, I've unfortunately seen toilets, piping, beer cans, magazines, and even cigarette butts. Most recently, I've seen pieces of plastic at almost 7 miles down. Q: Dear Dr. Shank, What can studying deep-sea ecosystems like those at hydrothermal vents tell us about the general health of the world's oceans? The "climate" at those depths seems pretty similar (cold and dark) no matter where you are on the planet, so I'm wondering if global climate change has a noticeable effect on those regions. A: Dear Julie, This is an interesting question and the short answer would appear to be "nothing", given the remoteness of these ecosystems directly to atmospheric climate. The reality is that these ecosystems are intimately connected to volcanic processes on Earth—they have evolved to live on earth's largest linear volcano, thriving in eruptive areas where lava frequently spews out on the seafloor and where seafloor vents are created. From Earth's geologic past, we know that volcanism has a tremendous affect on the health of our planet, frankly impacting our atmospheric chemistry, controlling mass extinctions of terrestrial and marine life. So, while a close connection between monitoring the "health of our ocean" and the state of hydrothermal vent ecosystems has yet to be made, it seems clear that increasing global oceanic temperatures are changing the acidity of the ocean (shallow and deep) and the ability of the deep ocean to store carbon. The change in deep-ocean chemistry will change levels of oxygen (that vent animals require) and pH that would impact the ability of certain animals to physiologically function properly, like make their shells. Q: Dr. Shank, Weren't you a little nervous about sailing through miles of solid ice? The Arctic Ocean is a long way from any rescue if something happened to the ship! A: Dear Suni, Yes, our location, less than 200 miles from the north pole was remote, and there are many courageous historical accounts of being shipwrecked and lost on the Arctic ice for months (these stories are frequently discussed when "up on the ice"). However, although isolated, we did have a long-range helicopter and modern day technology to contact other ships that might be able to reach us in an emergency. The Icebreaker Oden and ship's crew are well trained and prepared with life rafts and emergency equipment to handle any unfortunate mishaps. I don't think any of us felt unsafe at any time, even though the vast white ice covering was a continuous reminder of our extreme remoteness. Q: Dear Tim, Is it possible to explore the Gakkel using manned submarines? I know some Navy subs can cruise below the polar ice, and a Russian one even planted a flag on the ocean floor below the North Pole. A: Dear Anthony, Yes, manned submersible exploration of the Ridge is "possible", but I (and colleagues with whom I have discussed this possibility with) currently consider it a much too unreasonable risk. The risk is not being able to recover the vehicle from the moment the vehicle is released from the ship, and after many hours of exploration and returning to the surface due to the cover of ice, as well as having life-support and other vital systems as currently designed freeze during the launch or recovery due to the cold/wet air. I don't think it is a sufficiently safe exercise given how rapidly ice can move into a cleared hole (something that would need to be maintained by ships breaking and moving ice). It is true the U.S. and other countries have submarines with capable duration to transit away and clear from ice cover, and this is likely done more times than we know. In July 2007, the Russian sub MIR did make a short dive to the pole in order to "plant a flag" for their nation. It's not clear whether or not they were able to explore away from the open ice hole they created. Like I first mentioned, I think that it is "possible" to use human occupied vehicles under the ice, but the margin of safety is currently much too narrow. Alternatively, there are remotely operated vehicles currently being designed and field tested that can transit tens of kilometers under the ice with a light microfiber tether, and others that can be operated completely without a tether,using commands sent by sound through the water to communicate with the vehicle. I think this is the future of under-ice exploration in the Arctic. |
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© | Created June 2009 |
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