We Finally Know How Life Exists In One Of The Most Inhospitable Places On Earth

Nevertheless, as a renowned mathematician once said, “life, uh, finds a way.” And now, a little bit more than before, we know how.

“Our findings provide foundational understanding of the subsurface serpentinite-hosted biosphere in the Mariana forearc,” boasts a recent paper from researchers at the University of Bremen, Germany, and Woods Hole Oceanographic Institution, Massachusetts. 

“The lipid biomarker transitions from pelagic sediment into serpentinite mud highlight the resilience of microbial communities,” the authors write, with the organisms “finely tuned to shifting geochemical gradients, with extremophiles becoming dominant as conditions deviate from pelagic sediment norms.”

So, what’s going on? We’re talking about the Mariana forearc here – the bit of the ocean floor between the active volcanic arc of the same name and the deepest, narrowest part of the Mariana trench. It’s not exactly a place you’d choose to live: it’s extremely alkaline, near-freezing, and spotted by mud volcanoes that seep iron-rich rocks out into the dark water. There, under intense pressure and alkaline conditions, these rocks react and transform into rare native element minerals like awaruite or native iron – a process known as serpentinization. 

In much of the Mariana trench, this is a rather violent process. The reaction produces hundreds of degrees of heat; hydrogen, methane, and hydrogen sulfide are released into the water, creating a series of hot hydrothermal vents – and it’s likely thanks to these that anything can survive at all. 

But in the forearc, things are different: despite the mud volcanoes, the floor stays cold – and, as far as anyone knew for sure, barren. “Until now, the presence of methane-producing microorganisms in this system has been presumed,” explained Florence Schubotz, organic geochemist at the Center for Marine Environmental Sciences (MARUM) at the University of Bremen and co-author of the study, in a statement this week. “[But it] could not be directly confirmed.”

That’s for a handful of reasons, but it mostly boils down to this: the whole environment is just too hostile to life for DNA to be detected, even if it’s there. It may be true that some kind of life is hanging on despite the super-high pH, the extreme salinity, the lack of almost any nutrients, the icy-cold temperatures, and everything else – but, put simply, you need a minimum density of cells to be able to find it with traditional methods. Otherwise, they just won’t show up.

So, instead, the researchers looked for something else.

“We were able to detect fats,” said Palash Kumawat, first author of the paper and currently a PhD candidate in Bremen’s Geosciences Department. It’s the equivalent of figuring out a house is occupied by looking in the trash: it meant that the team could not only infer the microbes’ existence, but also how they manage to survive at all under these most trying of conditions.

And the answer? Rather than surviving on gases and minerals vented out from the floor in the serpentinization process, the microbes take a more direct route, extracting energy from these same sources, still locked within the rocks. From this, they produce methane – an important greenhouse gas, but also the basis for countless deep ocean ecosystems. 

“What is fascinating about these findings is that life under these extreme conditions, such as high pH and low organic carbon concentrations, is even possible,” Schubotz said. Indeed, the environment is, for want of a better term given the conditions, flourishing: the lipid analysis showed that multiple microbial communities are thriving there, and have for a long time.

How long, exactly? Well, if the team’s hunch proves correct, about as long as it’s possible to be. 

“[W]e suspect that primordial life could have originated at precisely such sites,” Schubotz said.

“[I]t is simply exciting to obtain insights into such a microbial habitat.”

The study is published in the journal Communications Earth & Environment.