Humankind has been pushing the boundaries of discovery for millennia, sending instruments to outer space, to the moon, and from other planets to the depths of our oceans. However, the interior of the Earth itself has remained relatively unexplored. That is set to change in the next decade, with a team of Japanese and UK scientists developing a $1 billion project to drill through the six kilometre layer of crust to reach the Earth’s mantle, a highly viscous layer of our planet lying between the outer core and the crust, and retrieve a sample. This new project, called The Integrated Ocean Drilling Program (IODP), comes after many previous attempts that yielded little success when it came to actually reaching the mantle of the Earth.
The mission is being carried out in one of three possible locations in the Pacific Ocean, all of which were chosen because the thickness of the Earth’s crust in these spots is very small, about six kilometres, as opposed to a thickness of about 60 kilometres over land. In addition to the technological problem of building the required drill, being able to transport it to the bottom of the ocean is also a big challenge. The latter task is being undertaken by a Japanese-built deep-sea drilling vessel. Dubbed ‘Chikyu’, meaning ‘Earth’, this vessel was first launched in 2002 and is capable of carrying up to ten kilometers of drilling pipes. It possesses on-board research facilities such as borehole observation, microbiological analysis, sampling processes, testing laboratories, and other equipment.
Damon Teagle of the University of Southampton, UK, is one of the researchers on the project. He described the procedure of drilling all the way to the mantle as trying to align a steel tube the width of a human hair with a 1/10mm hole when it’s at the bottom of a swimming pool. This is a massive technological feat, and considering the enormous amount of money and effort put into the mission, one can safely say that the samples collected would rival moon rocks in terms of scientific rarity.
The drill for the project will be used to bore a hole just 30 centimeters wide, which is itself an engineering feat. Since the idea is to retrieve a sample, the drill would have to be used without a riser (drills that use double pipes for venting gas), meaning they would have to pump seawater down through the hole with enough pressure to force a bit of the mantle back up to the surface. The drill bits for the operation would have to be used under extreme conditions of temperature and pressure (300 ˚C and 2,000 atmospheres). As such, with existing technology, these drill bits have a lifespan of only about 50-60 hours under these conditions. This means that it could take years to drill all the way down, unless technology improves.
The first mission to reach the mantle was undertaken by a team of US scientists in the early 1960s. “Project Mohole”, named after Andrija Mohorovicic, a Croatian meteorologist who first discovered the boundary between the crust and the mantle, was initially given recognition, even from President John F. Kennedy, but was shut down in 1966.
Why all this fuss just to get a bit of molten rock, you ask? After all, one can just wait for the next volcano to happen and retrieve some mantle sample that has come straight to us, instead of digging to get some. However, scientists wish to find a representation of the physical conditions within the mantle, and this is not provided by volcanic rock. This information will help us deduce the reason behind earthquakes, tsunamis, eruptions and other seismic movement, as well as the origins of the Earth itself. Also, the nature of the Moho layer, a transitional layer between the crust and the mantle will be explored. In addition to the structure and composition of the mantle, the project will focus on searching for evidence of microbial life on the way down to the mantle. One might think this is unlikely considering the high temperatures, but previous instances of life existing at temperatures up to 120˚C have been recorded.
If all goes well, the IODP hopes to start the drilling process by 2020. With the information ultimately obtained, we hope to glean a little more insight about the working of our planet and the universe, and proudly check off another box in our long list of achievements.
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