DAY 16: THE DEEP BIOSPHERE

Follow the link for more about Ingunn Thorseth and the very interesting twists in her career path, and her discoveries which have put her in the forefront of the development of geomicrobiology.  Ingunn added considerably more insight for this lay cruise member on life beneath the surface.text and photos by Courtney Flanagan

A theme that is intrinsic to this cruise with its international team of specialists was well expressed by Ingunn: "You can't chop up science." This multi-faceted approach to science has become increasingly important as scientists have focused more on exploring the Deep Biosphere. Within the last twenty years they have come to know that there is life beneath the surface, a lot of life. Possibly in fact, the biomass below the surface is as big as, or bigger, than what exists on the surface! To truly comprehend how our planet works therefore, it is crucial to understand these subsurface processes.

Very simply put, energy for life above the earth's surface comes from the sun. When we take a sample of the sediment below the sea floor however we are looking into a totally dark environment. And yet we find life. When we look at rocks formed from magma, either those created below the surface (gabbros)* or above the surface after magma has bubbled up through a vent or from a volcano(basalt), we also find microbes. So, where does the energy come from? Clearly there is life, its building blocks, organic compounds, created from reactions between water and rock. What is the energy source? Since water has oxygen, when it reacts with minerals that have iron, the iron is oxidized and hydrogen is released. Hydrogen has a lot of energy. Could there be a food chain based on hydrogen, just as the one all schoolchildren understand that is built around sunlight? Bacteria are found on the vents. Scientists believe they "feed" on methane. What other gasses contribute to life? Indeed what is life? Should our definitions change? And how do the chemical processes work, and with what activity. For example, we are now very concerned about greenhouse gases, one of which is carbon dioxide. Knowledge of the release of that gas, and the entire cycle of carbon, both above and below the surface, on land and in the oceans, is clearly crucial for the planet.

Currently there is a new subfield in biology: astrobiology, a multidisciplinary field combining geobiology and planetary science. There are obvious parallels between seeking life on other planets with seeking life under the surface in the Deep Ocean; both are extreme environments. Just as there is life under the earth, there is probably life under the surface of other planets. Knowing more about the chemical processes of life here will inform the astrobiologists as well. Ingunn told us that she thinks it is most crucial to learn first about life on earth before we try to understand other planets.

And understanding how that life works, all of it on the planet, is so important for all of us. It is only through understanding how life's processes work that we can make sure we are making wise choices as humans. "We need to learn how to treat the planet wisely so that we will all continue to have a good place to live."

* The very slow spreading plates of the Mid-Atlantic Ridge tend to bring more of these gabbros, or mantle rocks to the surface than are found in the Pacific. This is what makes the Atlantic often a particularly good place to look for keys to the magma.