Researchers on board the JOIDES Resolution gathered the core samples, which emerged from approximately 2,600 feet below the seafloor. The silt initially appeared to be dense, gray, and ancient, just like any other. However, the inhabitants had not moved in more than 100 million years.
Those bacteria were carefully brought back to life by Yuki Morono and his colleagues at JAMSTEC in the summer of 2020. They were neither dead cells nor preserved fossils. Despite being inactive, they were living things. After being given nutrition in the lab, they woke up and started growing. Nor at a leisurely pace. They flowered, as germs are known to do.
Not only had life endured for so long, but it had done so with so little, which was especially amazing. These microorganisms had been trapped in sediment that had never been exposed to light for entire epochs, entombed beneath the seabed. The oxygen was almost gone. It was almost devoid of energy. Before Tyrannosaurus ever set foot on the ground, the sediment had been deposited.
In a different 2020 study that was published in Communications Biology, other scientists discovered whole bacterial colonies residing inside solid volcanic rock, nestled inside tiny clay-filled fissures. These survivors weren’t solitary individuals. They drew energy from the iron molecules in the clay itself to form stable communities. No sunlight. No sweets. Just chemistry and fortitude.
| Item | Details |
|---|---|
| Location | Sediments and volcanic rock deep beneath the ocean floor |
| Depth | Hundreds to thousands of feet below seabed |
| Age of organisms | Up to ~100 million years |
| Energy source | Chemical reactions, not sunlight |
| Discovery methods | Deep-sea drilling, sediment cores, lab revival |
| Scientific impact | Expands known limits of life and longevity |
| Broader relevance | Guides search for life beyond Earth |
Even more astounding was the finding of sophisticated creatures—tiny worms and snails—living beneath hydrothermal vents. These organisms, which were previously believed to be limited to the vent holes themselves, were suddenly discovered tunneling through subseafloor spaces, creating vast ecosystems that relied only on chemical energy.
After reading the previous section, I stopped and wondered how many other kinds of life we have overlooked because we have been looking in the wrong place.
This isn’t a random discovery. The consequences are astounding. Not only has life been found in ancient rock and deep ocean mud, but it has also been found in the mineral-rich upper mantle layers. The existence of microorganisms in mantle rocks that were pushed to the surface by tectonic movements was verified by experts in 2015. Amazingly, in total darkness, the hydrogen produced by the reaction of these pebbles with seawater powered microbial activity.
The International Ocean Discovery Program provided scientists with access to one of the planet’s final frontiers by utilizing drilling techniques that had been honed over decades. An important layer of knowledge was provided by Jason Sylvan and his team at Texas A&M, who showed that bacteria that were previously believed to be extinguished are actually active and metabolizing in real time. Despite being only a millimeter in size, one microbe had far-reaching consequences.
What we know about the boundaries of life is essentially broadened by these discoveries. Additionally, they change the parameters for where we ought to look for it. Lava tubes are ancient on Mars. It is thought that beneath its ice exterior, Europa harbors a saltwater ocean. The moon of Saturn, Enceladus, uses cryovolcanic eruptions to shoot organic molecules into space. Why wouldn’t microbial life flourish in the solid rock beneath the oceans on Earth?
Crucially, the microorganisms’ capacity to thrive on inorganic resources like iron or hydrogen instead of organic nutrition reflects the type of metabolic adaptation that scientists anticipate discovering elsewhere in the solar system. Their perseverance is not only remarkable, but also educational.
The notion of a “deep biosphere” was purely theoretical over a century ago. It is now mapped, documented, and still expanding. Once thought to be geologically inert, the deep ocean crust is today understood to be a thriving microbial domain that covers the entire planet.
Researchers are still working to improve techniques for more accurate and in-depth sampling. Deeper understanding of microbial behavior is being made possible by techniques like DNA analysis, isotopic tracing, and methane measurements. A subject of curiosity has developed into a full-fledged scientific frontier.
However, there are restrictions. Scaling up the research is still both technically and financially difficult, and these creatures have not yet been significantly replicated outside of the lab. The notion of the habitable zone of life has, however, been substantially expanded.
The notion that hostile conditions are devoid of life is challenged by every sample that is taken from beneath the ocean floor. Conversely, they appear to act as survival nurseries. Life continues in the face of adversity, time, and darkness.
In addition, it subtly changes our understanding of the origins of life and its potential hiding places.
