The numbers cease to make sense when you attempt to visualize the bottom of the Mariana Trench. Eleven kilometers below. Eight tons of pressure are applied to each square inch. It was completely dark, with temperatures barely above freezing. The human brain almost immediately rejects this type of environment as being uninhabitable, but there are living things down there. not merely getting by. flourishing.
Scientists’ preconceived notions about the limits of life have been subtly rearranged by the results of NOAA’s ongoing investigation of the Mariana Trench. The deepest part of the ocean, below 6,000 meters, is known as the hadal zone. Researchers using robotic landers and remotely operated vehicles have been recording organisms there that seem completely unaffected by conditions that would destroy human biology in a matter of seconds. The way life keeps appearing where it has no right to be has an almost stubborn quality.
Green, fuzzy mats clinging to rocky outcrops on the seafloor were an unexpected discovery made by scientists investigating the Sirena Deep section of the trench during the 2012 DEEPSEA CHALLENGE expedition. not silt. not a remnant of geology. living microbial communities that appear to be consuming chemicals created by chemosynthesis, a process that occurs when seafloor rocks react with water. These microbes are not dependent on sunlight or anything that was previously dependent on sunlight, in contrast to almost every other organism on the planet. In essence, they have left the food chain that the rest of life on Earth inhabits.
Beyond the spectacle, the molecular chemistry involved is what makes this truly fascinating. University of Leeds researchers have been studying how deep-sea organisms survive under conditions that cause the water’s structure to be distorted. The hydrogen bonds that hold water molecules together start to break at very deep depths, which interferes with the biochemical reactions that take place inside living cells. It ought to be lethal.
Usually, it is. However, a molecule known as TMAO, or trimethylamine N-oxide, is present in high concentrations in many deep-sea species, and it seems to counteract this effect by stabilizing cellular water under crushing external pressure. The organism tends to carry more TMAO in deeper habitats. Although evolution obviously lacks foresight, it reads almost like a biological adaptation created with the environment in mind. It simply functions.
The scientific community is starting to take this wider implication seriously. Both Jupiter’s moon Europa and Saturn’s moon Enceladus contain subterranean oceans that are cold, pressurized, and lightless, according to NASA astrobiologist Kevin Hand, who co-authored the DEEPSEA CHALLENGE study. The theoretical case for microbial life in those alien oceans becomes much more compelling if chemosynthetic communities can flourish in the Sirena Deep without any connection to the sun. The expedition was framed somewhat poetically by James Cameron, who took part in it: a glimpse of how life might exist right now, billions of miles away. Maybe it’s a stretch. However, it’s not irrational.
The extent of these communities is still unknown. Although researchers haven’t yet taken a direct physical sample from the microbial mats themselves, the evidence they have gathered thus far—images, water samples, and sediment—strongly suggests life. The identification is regarded as credible by scientists such as Jenn Macalady, a geomicrobiologist at Penn State who has seen similar formations in underwater caverns. Confirmation is still pending. That distinction is important in science.
It’s difficult to ignore the recurrent theme in this field’s development: life appears whenever scientists push instruments into the planet’s most hostile regions. Even though they don’t always appear in ways that are simple to categorize or even completely explain. Once considered a sort of geological curiosity, the Mariana Trench now resembles a laboratory that has been conducting its own experiments for millions of years, long before anyone considered sending a submarine down to study them.
