In the context of the Ocean Drilling Project Expedition 399an international team aboard the research vessel JOIDES Resolution he managed to pierce the Earth’s mantle to a depth never reached before on the floor of the North Atlantic Ocean, west of the Mid-Atlantic Ridgethe very long underwater relief that crosses it. The sample extracted from the seabed is well over 100 meters long. 1268 msix times more than those obtained previously: it can provide very important information on the composition of the mantle and on the dynamics of the plates, but also on theorigin of life on Earth.
The site where the new drilling was done
The mantle is the layer that separates the crust from the core of the Earth and is the one that occupies the largest volume of our planet. Because of its depth, our knowledge of this layer is mostly based on indirect knowledge obtained thanks to the study of seismic waves. However, there are areas of the ocean floor where the rocks of the solid upper mantle emerge. This is what happens in correspondence with a submarine mountain called Atlantis Massifnear the Mid-Atlantic Ridge, where the North American, Eurasian and African plates meet. For this reason, in 2023 researchers carried out drilling on the southern side of the Massif, at the so-called Lost City Hydrothermal Field: this is an area where you have hydrothermal manifestations which consist of the escape of superheated water from the magma at depth and which provide the ideal living conditions for many microorganisms.
Sample extraction and analysis
The JOIDES Revolution managed to extract a rock sample much deeper than expected (well 1268 m) thanks to the unexpected ease with which the drilling took place. The extracted rock cylinder, of diameter equal to 6.5 cmwas found to be free of interruptions and was analyzed for months by researchers.
The sample has provided new information on the chemical composition of the mantle and on the phenomena that underlie the movements of the lithospheric plates. Not only that: it could be fundamental for understanding the processes at the origin of life. The cylinder shows traces of the transformations that the rocks of the upper mantle undergo, called peridotiteswhen they come into contact with sea water. The process, called serpentinizationtransforms them into serpentinites (which resembles green marble) and releases gases such as hydrogen, which microorganisms feed on. These emissions make these types of environments the probable places of origin of life on the planet.
Future prospects
Unfortunately, the research program that was part of the drilling is coming to an end, so JOIDES Resolution will not be providing any more samples in the near term. However, in the future, we may have the tools to access more “pristine” portions of the mantle, which have not been transformed by interaction with seawater, with other research vessels.
