We Just Discovered ＂Dark＂ Oxygen on Earth - Breakthrough Explained
Scientists have just discovered a "Dark" Oxygen source at the bottom of the ocean, opening questions about deep sea mining and the origin of life on Earth!
Category
📚
LearningTranscript
00:00The ocean can be a dark and mysterious place, and the deeper you go, the weirder it gets.
00:06As a species, we've only explored about 5% of the cold, dark void that covers our planet,
00:12and it just got even stranger. 5000m below the surface, in the pitch black,
00:18a mysterious source of oxygen has just been discovered. Has the call of Cthulhu finally
00:24been answered? Probably not, but the truth is much more perplexing and may change science
00:30forever. And it was all discovered by accident.
00:37Back in 2013, Andrew Sweetman, a researcher from the Scottish Association for Marine Science,
00:43noticed something strange on the ocean floor. He was studying a region of marine ecosystems
00:48located between Hawaii and Mexico called the Clarion-Clipperton Zone, a seabed that is larger
00:55than the country of India. As part of his research, Sweetman's team sent down machines
01:00designed to measure the oxygen levels within this environment. Once at the bottom, these
01:04automated seafloor landers sealed off sections of seabed with cylinders about 22cm square in size,
01:12and measured how the concentrations of oxygen in the seawater changed over a period of several
01:18days. From their previous research in areas around the world, Sweetman and his team expected
01:22to see a gradual decline in oxygen levels as organisms within the seawater consumed the oxygen
01:28through respiration. The rate of consumption could be an indicator of the amount and health
01:34of marine microorganisms in the sample, and could indicate the health of the seabed overall.
01:40But on this particular trip, something strange happened instead, that Sweetman had never seen
01:45before. The instruments showed that the sequestered water became richer in oxygen over
01:51time. Rather than being consumed, something was producing oxygen. This discovery of dark oxygen
01:57was announced a couple of days ago. What is happening here, and what does it mean, and why
02:02on earth did they decide to call it dark oxygen? These findings are really interesting, so I want
02:07to cover how oxygen usually works in the deep sea, what the researchers found, and their leading
02:13theory as to what they think is causing it. But first, I have to thank today's video sponsor,
02:19Shortform. For viewers of this channel, I think you've already clocked that I'm equally fascinated
02:22by space as it approaches diffusion, why bats are so weird, and how to make the world's hardest
02:26puzzle. My problem is that I never have enough time to read about all these topics. That's why
02:31I really like Shortform. It's like a book summary on steroids, providing a synopsis and explanation
02:36of the key ideas clearly and efficiently. I was just rereading Carl Sagan's Cosmos, where he
02:42celebrates the victories of scientific endeavor and talks about some of the biggest questions
02:46humanity can ponder. Shortform does a great analysis that breaks it down into key ideas,
02:51and ideas are powerful. If you're interested in speeding up your learning, check out Shortform
02:55with my link in the description down below, shortform.com forward slash drben, to get a free
03:00trial and 20% off your subscription. Thank you Shortform for sponsoring this channel, now let's
03:05get into the video. I want to start with how oxygen usually makes its way down into the
03:13deepest parts of our oceans. Almost all of earth's oxygen is produced by photosynthesis, carried out
03:19by plants, algae, and certain types of bacteria. You're likely already pretty familiar with this
03:24process, it occurs in chloroplasts within plant cells which contain a green pigment called
03:29chlorophyll. This pigment captures sunlight, splits water and carbon dioxide, and produces
03:35sugar, and importantly for life like us, gaseous oxygen as a waste product. Oxygen produced on land
03:42is spread across the planet through atmospheric circulation, but how it gets deep into the oceans
03:47is more complicated. At the surface, oxygen from the atmosphere can diffuse directly into the
03:53surface of water, assisted by winds and the mixing effect that increases the water's surface area.
03:58In the topmost layers, water can also be filled with photosynthetic microorganisms that are
04:03producing oxygen directly into the water. In fact some estimates indicate that phytoplankton alone,
04:09which occur in water, produce around 50% of the entire planet's oxygen. However,
04:13sunlight entering the water can only ever travel down about a thousand meters into the ocean under
04:18perfect conditions, but usually more like 200 meters or so. This means that photosynthesis
04:24and oxygen availability rapidly fall off beyond this depth. So how does oxygen reach deeper layers
04:30of water? That mostly relies on the fact that gases dissolve better in cold water than warm
04:36water, and that cold water is also denser than warmer water, so it sinks. This allows polar water
04:43to soak up and hold onto large amounts of oxygen, and then be drawn down to the ocean floor,
04:49creating a convection current called the thermohaline circulation. This drives a global
04:55conveyor belt moving oxygen-rich waters across the ocean floor over a surprisingly long and slow
05:01process, circulating on timescales between a hundred and a thousand years. This provides a
05:07constant low level of oxygen to the ocean floor, enabling life to thrive, even if it does sometimes
05:13look a little weird. This idea that oxygenated ecosystems are only possible through photosynthesis
05:19and that all other ecosystems are kind of lucky to receive some of the offshoot oxygen has been
05:24the foundation of how we understand why life has evolved the way it has on these systems and on
05:30Earth as a whole. Sweetman's discovery that actually there may be a source of oxygen on
05:36the ocean floor potentially could rewrite our understanding of what is possible on our planet.
05:42Initially, when Sweetman and his team actually retrieved their data, they actually thought that
05:47the sensors they were using were faulty, because every study ever done in the deep sea has only
05:53ever seen oxygen being consumed rather than produced. They put the result down simply to
05:59bad data and moved on with other experiments. It wasn't until eight years later in 2021 that
06:06Sweetman went on another research cruise and again found the same result. For this experimental
06:12run however, the researchers used a different measurement method. So now two independent
06:17approaches had produced data sets that both showed the same result. It was at this point that Sweetman
06:24realized that for the last eight or nine years he may have been ignoring this hugely groundbreaking
06:30process occurring 4,000 meters down on the ocean floor. Further still, the amount of oxygen being
06:36produced wasn't insignificant. The concentrations in these chambers began to exceed the oxygen
06:43level normally observed in surface waters rich with photosynthetic organisms. So what was actually
06:50going on here? This is where a unique feature of the clarion-cliperton zone comes into play.
06:55In this area of the Pacific, the seafloor is covered with small rock-like clusters rich in metallic deposits called polymetallic nodules.
07:02You may have heard of these clusters before, they are the resources often targeted by deep sea mining companies as they're full of valuable materials like cobalt, manganese and nickel,
07:08critical for various industries from battery technologies to consumer electronics.
07:13These polymetallic nodules were unique to the clarion-cliperton zone because they were
07:18critical for various industries from battery technologies to consumer electronics.
07:23These polymetallic nodules were unique to the clarion-cliperton zone that Sweetman was studying,
07:28suggesting that these rocks may have an important role. In September of 2023, Sweetman contacted his
07:34colleague Franz Geiger, a professor of chemistry at Northwestern University, to discuss possible
07:40explanations for this oxygen source. The result of this work was the pair coined the term dark
07:46oxygen because like all good scientists, when faced with a mysterious phenomena that can't be
07:50explained, you just prefix it with dark. Geiger though did have experience investigating novel
07:55oxygen sources and had previously found that under certain conditions, saltwater in the presence of
08:01rusted metal can generate small electric currents. Could it be that these metallic nodules were
08:07performing a simple form of electrolysis, splitting water into its components of hydrogen and oxygen
08:13through some rudimentary form of naturally occurring battery?
08:21To understand what was actually happening, the team recreated the conditions found on the sea
08:26floor in a laboratory on board their ship. The researchers began by sterilizing their samples
08:31to remove possible oxygen producing organisms from the samples of nodules and seafloor sediment
08:38to ensure that no other sources of oxygen generation existed in their experimental
08:42equipment. By enclosing the samples in airtight containers, they monitored the oxygen levels over
08:48a period of several days. Consistent with their observations on the ocean floor, the team observed
08:54again that the oxygen levels slowly increased in the containers, despite no photosynthetic life
09:00being present. Interestingly, oxygen levels increased to three times the background
09:05concentration, ultimately then slowly plateauing after a few days. To provide a deeper analysis,
09:12the pair then shipped crates of samples to Geiger's laboratory at Northwestern University,
09:17and what they found was shocking. Literally. From the surface of a single nodule, the team
09:23measured voltages of up to 0.95 volts. For context here, it takes about 1.5 volts of electricity,
09:30about the same as a standard AA battery, to split seawater through the process of electrolysis.
09:36So here we have some kind of interesting facts starting to come together. We have evidence of
09:41some voltage generation. The oxygen produced in their experiment plateaus, which could indicate
09:46that the energy that drives the splitting of these water molecules becomes somehow depleted. So maybe
09:51the team is correct in that somehow there is a form of geological battery in operation. Polymetallic
09:57nodules are pretty strange structures, typically forming over millions of years as metals from
10:04seawater precipitate onto a nucleating point, usually something like a fragment of shell,
10:09a bone, or a rock. And most of the estimates that I've seen say they grow at a rate of 1 to 10
10:14millimeters per million years. In the paper, they hypothesize that the dark oxygen production
10:21may have partly resulted from seawater electrolysis, with the necessary energy coming
10:27from the potential difference between metal ions within the nodule layers, leading to an internal
10:32redistribution of electrons. They go on to say that the geobattery hypothesis is further supported by
10:39the link between the dark oxygen production rate and the average surface area of a nodule. What does
10:45that mean? That just means the bigger these nodules get, the more oxygen they seem to produce. This
10:50connection could be due to an increased abundance of anode and cathode sites, or a greater abundance
10:55of high nickel or copper dendritic porous layers in the larger nodules. However that kind of opens
11:01up more questions, like why didn't this process deplete a long long time ago? A battery in
11:07practice is actually a very hard thing to get right. I appreciate here that this is still very
11:12early work, but this feels like kind of a weak argument to me, because many mechanisms could be
11:16surface area dependent. At the moment, we just don't really know what is actually happening here.
11:22One point I did find interesting though, was that there was a theory put forward by the researchers
11:27that potentially the initially very high oxygen production rates that ultimately then plateaued,
11:33may have been related to the bow wave of the landing vehicles removing sediments from the
11:39surface of these nodules and exposing electrochromically active sites. This again is kind
11:45of surprising to me, and I'm not entirely sure that I'm convinced by that as an explanation.
11:50In my mind, the rate at which these nodules grow is so incredibly slow that the idea that sediment
11:56deposition or removal of that sediment is ultimately the rate limiting step just doesn't
12:01really feel that reasonable to me. But as of yet, we have very little further information.
12:06We do know though that oxygen, it looks like, is being produced, and actually that's a really
12:12awkward realization for the deep sea mining companies that partly funded this research.
12:18If we do find that these polymetric nodules provide essential sources of oxygen for deep sea life,
12:24but potentially also for our planet as a whole, then maybe mining these deposits for resources
12:30could turn out to be a really bad idea. In response to this study, Patrick Downs, a representative of
12:36the Metals Company, one of these deep sea mining companies that funded the work, said he has serious
12:41reservations about the findings, adding that his own analysis suggests Sweetman's results are due
12:47to oxygen contamination from external sources, which would be very convenient say if you were
12:52a mining company that didn't want its operations to ultimately be disturbed. Apparently a rebuttal
12:58article is on its way from this group so we'll just have to wait and see. However this is something
13:02we should take seriously. Back in 2016 marine biologists visited sites that were mined in the
13:071980s and found that not even bacteria had recovered in the mined areas, whereas in unmined
13:14regions nearby marine life continued to flourish. Why such dead zones persist for decades is still
13:21kind of unknown. However this should put a major asterisk onto strategies for deep sea floor mining
13:28as the faunal diversity on nodule-rich areas is actually even higher than the most diverse
13:34tropical rainforests. A deeper understanding of how these oxygen generation mechanisms work
13:40and if they are significant to oxygen levels on our planet, either now or at any time in our past,
13:46could be influential to understanding not only how life evolved on our planet but also how we
13:52look out to our universe to determine if what we are seeing out there are actually signs of life.
13:58If oxygen can be created easily and commonly without the need for life, our studies looking
14:03for molecular oxygen on exoplanets might turn up nothing more than just a bunch of space rocks.
14:09This is a really fascinating and deep topic and if you are interested in it we actually did a
14:13video very recently with literally one of the pioneers of research in this field looking for
14:18signs of alien life that are out there in the universe. I'll leave a link somewhere or down in
14:22the description so you can find out more. I want to know what you think about this breakthrough.
14:27I think at the moment there are very little credible other theories being put forward but I
14:32don't entirely believe this battery argument because the mechanics and complexity of actually
14:37making working batteries that don't instantaneously deplete themselves is pretty tricky to get right.
14:43What else could be causing this? Tell me what you think in the comments down below. Do you agree
14:47with this geobattery hypothesis? Personally, like I said, I'm not convinced. If you guys really
14:54enjoyed this video and you'd like to support the channel more than you already are by watching,
14:58feel free to check out our Patreon page that we literally just launched.
15:02Thank you as always for tuning in, see you guys next week, goodbye.