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Deeper than anyone else: Interview to Yasuhiro Yamada, director of exploration of the drilling vessel Chikyu

Author: Beatriz Martínez-Rius (Sorbonne Université, Paris)

Imagine a hole where you can fit 25 Eiffel Towers, one above the other. And now, imagine this hole under 2.500 meters of seawater. This is the drilling capacity of the Chikyu, the most advanced drilling vessel in the world. By dropping a pipe up to 10 kilometers (longer than the Mount Everest), it can drill and obtain samples from the seafloor deeper than any other vessel has done before.

The Chikyu, which in Japanese means “The Earth”, was built in 2005, and since then it has been operated by the Japanese Agency for Marine-Earth Science and Technology (JAMSTEC). The research carried out on-board the Chikyu is astonishing: reaching the core of faults, where the earthquakes are produced; studying life proliferating at thousands of meters deep, in extreme environments; and even working to reach the mantle of the Earth, where no one has ever gotten there.

During our last Saltgiant meeting in Trieste, in June 2019, we had the opportunity to meet Yasuhiro Yamada, director of exploration and R&D of the Chikyu at the JAMSTEC. Yasuhiro presented us the Chikyu’s characteristics and the cutting-edge research that the Japanese team is doing, thanks to the unique drilling capacity of the vessel. Moreover, they are collaborating with the International Ocean Discovery Program (IODP), a scientific project that, from the 1970, has brought together scientists from around the world to explore the seafloor. 

With the aim to make known this extraordinary research projects and technologies, we interviewed Yasuhiro Yamada.

Q: First of all, can you talk us a little bit about your background, what are you doing in the JAMSTEC and how are you managing the project of the Chikyu?

A: I started my career in oil and gas industry. I did my degree in geology, and then I joined the oil and gas industry as an exploration geologist to look for gas and oil fields subsurface. I worked for an oil company during sixteen years, in an exploration department. While working at the industry, I got the opportunity to obtain a scholarship to study abroad and do a PhD research. I contacted several professors and supervisors, and one of them suggested me that a three-year funding is enough to finish a PhD research in the UK. So I stayed there during three years doing research. It was during that time that I learned a lot on the European style of research, of science, on the industry’s situation, and so on.

After coming back to Japan I wrote the thesis and I got the PhD from the University. It was while I was studying abroad when my eyes opened to see in a much wider sense. I really wanted to do something more from subsurface exploration, that has huge advantages for the oil industry. I really wanted to apply those techniques and methods to something more, because they could be useful for the scientific research. So a university professor invited me to become a University member, and then I changed my career from the industry to the Academia. I spent twelve years as a professor, and it was good, because the University gave me freedom to do everything. So I worked on the estimation of stability issues of the subsurface and the environment. I have been using geological modeling techniques to subsurface exploration and for analyzing the development of forces of the strata, I mean: folding or deforming. Geology is deforming on time, so that’s my mission: by looking and by doing geological modelling with students, we have measured the dynamics of the subsurface deformations, and found out that this aspect can be compared with real subsurface borehole data. That is the reason why I participate into scientific drilling.

Scientific drilling is an excellent work: it is an international enterprise, where you can find the state of the art science and technology. I realized that there was such a beauty, in the scientific drilling world. While I was doing my activities at university, the JAMSTEC’s president invited me to move to his institution, in order to lead the scientific drilling projects of the Chikyu. I decided to move there and, since then, I have been taking this leading role. Currently, my research is assigned by JAMSTEC’s president. We are working seriously towards the drilling of the mantle Moho, because that ship was initially constructed for that purpose, although we have not started this activity yet. But now it is the time to begin this activity of drilling the Moho, and that is on what I’m working right now.

Q: You have mentioned that the JAMSTEC owns one of the few drilling vessels of the world, the Chikyu. What are the characteristics of the Chikyu, which make it a unique drilling vessel in the world?

A: The Chikyu is unique and the only one scientific drilling infrastructure in the world that has a riser capability. Having a riser means that something can be raised from the borehole, for example cuttings (that are rock fragments produced by the drill bit while drilling). The riser consists on a pipe, a huge pipe, that is connected to the ship and to the ocean floor through a small structure called well head.So the riser pipe connects the borehole to the ship, and it is separated from the seawater. That is why the drilling fluid, that we call mud, can be circulated from the ship to the borehole and then going back to the ship. When the mud goes back up, it includes cuttings, water… So by using that riser system, anything from the borehole can come to the ship and can be monitored and analyzed.

Riserless vessel (left) and the Chikyu, with its riser system (right). BOP: Blower Out Preventer (avoids oil and gas spills, that can set into danger the vessel and the environment).

Also, that is actually great for drill really deep holes, because we can choose and change the drill mud that is suitable for the particular subsurface environment, in order to stabilize the borehole. If the borehole wall is not stable, we cannot go deeper, and something must be done to maintain the stability walls. For that purpose, the riser system is vital to drill deeper.

Q: You know that scientific drilling is not always seen in a good light by the public’s perception. There is a general concern regarding to the impacts of the ocean drilling in the marine environment, and I would like to ask you: what is the real environmental impact of scientific ocean drilling? And which measures do you take in order to mitigate this impact?

A: Yes, I agree, pollution is the main concern for the oil and gas industry, because they are drilling exploration wells in the subsurface (I mean, onshore and offshore) and the environmental impact of drilling is a huge issue. In the case of the Chikyu, since the riser capability can separate the drilling fluid (the mud) from the seawater, it is a very clean technology. We don’t need to waste or dump those fluids and cuttings to the seawater, because they are separated. So the riser system is an environmental friendly system to drill holes.

Another thing is that this people is aware of the marine mammals, like whales or dolphins, that are living there. Sometimes the ship operations produce noise, that could be harmful for the marine mammals living nearby the vessel. So we also need to be careful on not to make unnecessary noise, unnecessary loud vibrations or any kind of sound that could be dangerous to such potential marine fauna.

Q: We, in the Saltgiant Project, are very interested in exploring the Messinian Salinity Crisis in the Mediterranean, and understand how the Mediterranean salt giant was formed. But, to do so, it is essential to drill those evaporite layers. So, in which sense do you think that the Chikyu can contribute to enhance the knowledge of the Mediterranean basin? Is it envisioned to bring the Chikyu to the Mediterranean, in a nearby future?

A: Yes, I think that the possible contribution of the Chikyu to the study of the Saltgiant can be huge, and this is again because the ship can use a riser system. That means that we can use an extremely high salinity drilling fluid, which will lower the possible dissolution of the salt layer by the drilling; and we can also stabilize the borehole, which is important to avoid the possible collapse of the borehole. So whereas we can drill as fast as possible the salt layer, we can install a still pipe in the rock. Then, the space in between the case and the rock is fixed by cement, stabilizing the borehole. By doing that, we can collect a lot of samples from salt and other rock material, that can be used for various purposes such as microbiology, geochemistry and other studies. We can also date the rock by using isotope analysis.  It will be a very good method to obtain much more dataset and information from the rock sample. In this way, I think we can contribute to the Saltgiant project.

But also, since we can drill through the salt, we can reach the sequence underneath the evaporites, which should help us to explain which was the paleoenvironment just before such a massive salt deposition. So again, that could be a great information for the people living by the Mediterranean Sea area: how our land was formed in the past, and also why such a salt deposition process occurred. All this can be learned from drilling and sampling the salt. So the Chikyu can contribute to answer those questions, and that is why I’m fascinated to participate in the Saltgiant project. I’m looking forward.

During the last years, the Chikyu’s activity has been focused on exploring the offshore areas nearby Japan. Source:

Q: We are all expecting that as well! So you mentioned the microbes. As you know, in our project we are trying to study the Messinian Salinity Crisis from a multidisciplinary approach, and some of our fellows are dealing with microbial life in extreme environments. The JAMSTEC is pioneering a great amount of studies in microbiology related with the conditions of life in deep environments. Can you explain us why do you study this kind of microbiota, and how this ways of life can contribute to the scientific knowledge of further environments?

Microbial life found at 2466 meters below the ocean floor during the Chikyu’s exploration 337 (scale of the bar: 5 µm). Source:

A: Yes, in fact microbiology research is an emerging field in sciences. When we drill deep and we look for life, in many cases they are there, we find life there. And that is fascinating, because we don’t know what they are doing in such deepness, many things around them are unknown. Discovering their role in such depths is important because microbiological activity consists on changing something into something else. In the past, people believed that many reactions happened by chemical processes, but now we think that those same reactions are done by the microbiological activity in the subsurface. So many things can change if we start to think about subsurface processes as the result of microbiological activity, instead of chemical reactions. And why this is so important? Because if a reaction depends on the microbiological activity, the reaction will be active as far as the microbes are active; and this activity can be determined by many factors, such as the temperature or the material circulation system.

Life can survive only by providing something: People need food and water, and we produce something of waste, that’s the life cycle. The same happens with microbes in such deepness: they need something to eat, and they should be producing something of waste. Their life cycle should be contributing to the circulation of the material in a sense that is still unknown. This processes, produced by microbes, should be determined by the environment and the temperature, or the water supply, or the material supply. Understanding those reactions as the result of life, and how they are determined, is very different from understanding them as chemical process.

Q: When we look at the history, we find out that from the beginnings of marine geosciences exploration, in the 1960s and 1970s, the oil industry has constituted, in many cases, a trigger for the scientific research. I think that there is a close relationship between the development of offshore scientific research and the industry that has been essential, since studying the ocean seafloor requires so many resources that (at least at the beginning) could only be provided by the oil industry. But, on the other hand, I think that it is a complex relation that tends to be oversimplified by the wider public, being seen as a straightforward relationship from the industry to sciences. So I would like to know, from your point of view, how is this relationship and how one can contribute to the other (how the oil industry contributes to sciences and vice-versa)?

A: Yes, it is true. Well, since I have a working experience in the industry and also at the University Academia, I know both mentalities (laughs). True, in the past years the industry has financed with money and has provided data to do some research at the University Academia. But it is not a simple situation. The company wants to know something very new or fundamental in sciences, and it cannot be done by the company’s activity. That is why the companies have been providing money and data to the university: to understand something new or interesting, or still not very well understood by the industry.

But nowadays I think that this relation is going to the next phase. The companies are doing their activity in their own way and they are making an economic profit from it, but they might not be producing anything new, so they really need innovation. This innovation is always born from the collaboration between the academic people and the industry persons, or technology-developing persons, and so on. It is always a collaboration that emerges on a particular subject or even just from a chat after lunch or so, while you are just talking about particular things, and both sides understand: “Oh, this could be something new”. And then it starts the discussion about what you need or what I need. While doing such a speaking, both sides find out that that could be a merit for both sides, and then this collaboration starts. This is the current status of the industry and University collaborations. I think that it is beneficial for both sides, and that is why this kind of collaboration is increasing. Also the Government, the ministries, have understood that this kind of collaboration is important to innovation. Innovation is the key to go further, to go beyond the current knowledge and current technology, so many governments agencies are giving funding to stimulate that innovation. Japan, and I think also the UK, Germany… Are stimulating it. That is very important, and not only in one way, but in both sides… But it is not to say both sides, it is to say: A collaboration, where we are sitting in the same table and we speak a lot, freely, trying to find out what could be useful for both sides, until we say: “Nice idea!”. Then, the next stage will be born in such a collaboration and discussion.

Q: I would like to finish by asking you which is your biggest project, the one which you are dreaming to achieve?

A: Definitely, my biggest project is to drill into the mantle Moho. That is a big hole, the humankind has never gone to such a deepness. But although the mantle Moho is very far away, by using the current technology of the ship I think it is possible to drill it.

So to drill into the Mantle Moho is our biggest target, and not only because we haven’t gone there yet, but also because to drill the Moho surface is to understand the dynamics of this planet. The mantle Moho was discovered by the professor Mohorovičić by reflection seismology, and it suggested acoustic impedance differences: the rock types, or the different properties of the rocks above and below, should be different. The seismic technologies could detect this boundary surface.

The people believe that the Moho is a kind of a plain surface in the Earth interior, but I think that it is not true. The temperature of the planet Earth is cooling down and while cooling down, the planet produces several earth boundary surfaces in its interior, being the Moho one of them. So the Moho is the crust and mantle boundary, and the mantle and the core has also a boundary. All those boundaries mean that the inside and outside material is different. But that boundary should not be stable, because the planet is cooling. So that means that the Moho surface should go down, I mean, go deeper: then, it is just a reaction surface. The material just above and below the Moho surface is producing some chemical reactions, so it is a reaction surface that goes down very slowly, and not just a simple surface. It is a complex structure that constitutes a transit zone, which might have hundreds of meters of thickness; and we need to understand it: which kind of rocks are there, which kind of reactions are produced, how and why the Moho is moving… For doing that, we need to measure the temperature, the pressure, the rock type, the fluids and the gas, among many other things. Understanding what is going on at the Moho surface will contribute to explain what is going on in terms of the planet history. So going down to the Moho means understanding the dynamics processes of this Earth. So it is not just to say: “This is the Moho rock, the mantle rock”, and bring it to a museum. Well, we could do that, but that will be just a rock. Drilling the Moho surface is far beyond that, it means to understand the dynamics of the Earth; and that is why I really want to go there. That should bring a huge amount of knowledge to everyone.

More information about the Chikyu and the current projects of the JAMSTEC and the IODP can be found at:


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