We all know about oxygen. But what is this dark oxygen? Where is it from and what’s so special about it? This is a latest discovery and yet need to be studied further. Let’s just understand this concept in a simple way.
Dark oxygen is produced by polymetallic nodules. But what is this polymetallic nodules? Polymetallic nodules is formed over million of years. Millions of years ago in the ocean floor, contained dirt and also volcanic ash. Dirt or clay and this volcanic ash combine to form a microparticle, even finer than the sand particle. This contributes to the formation of this nodule. As we know deep ocean waters contain numerous metal. Mn, Ni, Co, Fe are some of the examples of such metals. Precipitation of metals in the seawater, onto this microparticle is how polymetallic nodules are formed. It is a extremely slow process. A few mm per million years is the growth rate. That’s how slow the process is.
Image source: https://dsmobserver.com/2019/12/a-primer-on-polymetallic-nodule-fields/
IN A BIT MORE DETAIL
Deep ocean water contains manganese but it is in oxidized state (Mn2+). It also contains oxygen via cyanobacteria and other living organisms and of course H2O. All these 3 reacts to form MnO2, manganese dioxide, which is in the form of a solid. This MnO2 combines with the microparticle. Similarly other oxidized elements that exist within the deep ocean water combines with this particle to form polymetallic nodules.
HOW DOES THIS PRODUCE THE SO CALLED DARK OXYGEN?
Splitting seawater to produce oxygen is how it is explained. Polymetallic nodules found in the ocean floor is surrounded with salty sea water. It works both as an anode and a cathode at the same time due to the presence of various metals comprising it and also the seawater surrounding it. Water acting as an electrolyte provides hydrogen ion to the anode and what remains is oxygen. This is how dark oxygen is formed without the presence of any living organisms or sunlight says an ex assistant professor pursuing PhD in Astrophysics.
AN ACCIDENTAL DISCOVERY
Years back in 2013 Andrew Sweetman, a researcher from the Scottish Association for Marine Science was studying a region called Clarion – Clipperton zone of the Pacific (a seabed larger than India) and noticed something strange on the ocean floor. His team send down machines to know about the oxygen levels deep down and also to know how its concentration changes over a period of several days. What came shocking to him was the results that the instrument showed. Sequestered water became richer in the oxygen levels over time instead of being consumed leading to only one conclusion – something was producing oxygen.
At first when analyzing the data produced, they thought that the sensor might be faulty and told his students to throw it away because all the study ever performed in the deep sea has produced results exact opposite to the one in hand i.e. being used rather than produced. They concluded it as bad data. But 8 years later he went on another research and stumbled on the same result. For this research they employed a different measurement method but got the same results. He then realized he might be ignoring something very important and fascinating.
DISCOVERING THE TRUTH ABOUT DARK OXYGEN
In order to know what was really happening, the team recreated the same conditions of the seafloor in a laboratory on board their ship. They sterilized the samples of nodules and seafloor sediment so as to remove any organism hat could produce oxygen to make sure that no other source existed for oxygen generation within their samples or equipments used.
- By enclosing the samples in air tight containers they monitored the oxygen levels over a period of several days.
- The team observed that the oxygen levels gradually increased within the containers. It increased 3 times to the background concentration and then slowly plateauing after a few days.
- For a deeper analysis, crates of samples were shipped to Franz Gigers (Sweetmans colleague, chemistry professor at Northwestern University) laboratory.
- From the surface of a single nodule, the team measured voltages for up to 0.95 V.
- In a study published, it was stated that the geo-battery hypothesis was supported by the link between dark oxygen production and the average nodule surface area (the bigger the nodule get the more oxygen they seem to produce).
In conclusion, this is a new discovery and there are only little other theories being put forward. Dark oxygen has been discovered but still have to be studied deeply and many more hypothesis and arguments are yet to come. However, if it turns out to be the way how it is put right now then it points out that oxygen can not only be produced by living organisms or in the presence of sunlight but also be done by these rock like substances found in the deep depths of dark water.
Written by Gayathri Gopinadh