Earth's Deep Biosphere - Super Microbes That Survive The Impossible

By: O. Astor

​When someone says unknown, most will think of outer space - far spun galaxies and cosmic star clusters punctuated with devouring black holes or crackling supernovae. Most will think that stepping onto a rocket ship, or some other futuristic space craft, and blasting to the furthest reaches of our universe where no human has ever stepped before. Whilst that is all true, what if I told you there is a whole hidden world, where over 90% of our planet's microbes live, right below our feet? A world even more astonishing, weird and wonderful than you could ever imagine. 
 
Welcome to earth’s deep biosphere, a seemingly unglamourous world swamped by rock and acid and toxic salt compounds. I recently became aware of this fascinating ecosystem whilst doing some habitual and slightly guilty scrolling on You Tube. However, I instead ended up coming across a video by 'Kurzgesagt - In a Nutshell’ (an incredible science channel that I 100% recommend) about a range of ‘extremophiles’ living deep below our planet's crust. I was enthralled by this strange new world, and fell in love with the bizarre and wonderful ways life has persisted and survived in such unforgiving conditions. 
 
Starved of oxygen, choked by acid, throttled by radiation and crushed under the weight of thousands of mountains, life persists. The total biomass of life subsurface has been estimated at 15 to 23 billion tonnes of carbon. This amount of carbon corresponds to ≈ 245 to 385 times the carbon mass of all humans on the surface. At 4000km below the surface, there is almost no free oxygen left, and the average temperature is 120 degrees celsius, though it can reach much higher temperatures if a lava pool is nearby. Here, radioactive elements such as thorium and uranium emit constant waves of radiation, and rocks are peppered with extreme amounts of salt.
 
So, where exactly does this life actually survive? Seemingly solid rocks are filled with tiny fractures or pores. These cracks are opened by the movement of tectonic plates smashing into one another over thousands of years.Here, the bacteria desulforudis audaxviator thrives. It synthesizes its own food by consuming sulphur and carbon found in rock, and transforming them into organic substances. If conditions get too harsh, it kills itself to survive by splitting itself down the middle and breaking into two separate parts (one big and one small) known as an endospore. The big part swallows the small part, forming a cell-like structure. This spore will float around - completely dormant for maybe thousands of years - until it finds a place with suitable conditions to spring to life once again. 
 
Found here too are Altiarchaeum hamiconexum, microbes which are covered in a double membrane that protects them from extremes. They survive by shooting out microscopic ‘’grappling hooks” used to tether themselves across porous rock. Microbes down here have incredibly slow metabolisms. They had a meal when you were born, and are still digesting it now. They spend little and consume little and in this way, are able to essentially ‘’live forever’ (or at least  for millions of years). Contrary to most microbes, these divide and reproduce on average only once in 1000 years due to nutrient scarcity. 
 
Life down here is a twisted, wonderful thing, suspended in perpetual slow motion and something which unfortunately, there is still so much we do not know. For one, finding and collecting deep microbe samples without contaminating them is incredibly difficult, making research into them a huge challenge. Furthermore, once these microbes are back up at the surface, it is hard to replicate these extreme conditions to keep them alive. Therefore, studying them in their natural habitat is an expensive, complicated process. However, advances in science, engineering (or just sheer human creativity) will 
hopefully one day open this almost unreachable world of wonders to us. It baffles me that we are already off exploring distant planets, when so much of our own incredible home is still cloaked in speculation and the unknown.