The beginning of life on this planet is believed to have all commenced from within the oceans. The abundance of life observed within Earth’s atmosphere makes it difficult to imagine anything less, yet there are zero detections of life-forms anywhere outside of planet Earth, meaning that as far as evidence goes, the rest of the solar system and beyond are devoid of life.

Hard to believe, right?

Well, during the search for extra-terrestrial life, there are three specific parameters considered for the existence of animals, which consist of: source of energy (for photosynthesis, chemosynthesis); liquid water (as a solution for chemical reactions to occur, as well as, to allow movement of cells internally); and chemical elements (for structural backbone of organisms).

Potential for life existing within the solar system

Other planets and moons, particularly the ones in our solar system, do not have optimal conditions that the Earth has, for common life as we know it to exist.

The proximity of planets and their moons to the Sun narrow down the possibility for life and recent discoveries of tidal activity for example on Europa (one of Jupiter’s moons) suggest that the frozen surface potentially has oceans hidden deep beneath the thick layer of ice. Similar findings on Titan (a moon of Saturn) suggest that liquid methane oceans exist within its stable atmosphere. Enceladus (another of Saturn’s moons) has been observed to have jets of water shooting from between fissures in it’s ice surface and scientists strongly believe a global ocean exists beneath.

This opens the door to search for organisms that can exist within the extreme environments on other planets in the universe. This is becoming more feasible as a result of the extreme conditions that organisms are found inhabiting, within the oceanic depths of our very own planet.

The Mariana Trench

To the south of Japan and east of the Philippines, in the western Pacific Ocean, lies the Mariana Trench, a crescent-shaped fracture in the Earth’s crust that measures more than 1,500 miles long and approximately 43 miles wide.

Comparison between the depth of the Mariana Trench compared to other famous locations for their size. (Sourced).

Laying at its base is Challenger Deep with extreme depths; measuring a whopping 10,994 metres deep. That is 6.83 miles. Mount Everest could be placed inside with over a mile to spare above its peak. 13 of the tallest building in the world, Burj Khalifa, stacked on top of each other wouldn’t even scratch the surface, quite literally.

The most extreme marine conditions exist within this massive oceanic abyss, including: massive pressures; both low and high temperatures; no sunlight; highly toxic regions.

Environmental conditions and the life existing within the Mariana Trench

Pressure

The pressure of the air at sea level is 14.70 pounds per square inch (psi) or 1 atmosphere (atm), what us humans feel acting on us every single day. We do not notice any pressure as we have become so accustomed to it.

Pressure increases with depth of the water; meaning each and every 10m down in the water column; the pressure rises by 1 atm (14.7 psi). The pressure down at the lowest point of the Mariana Trench exerts approximately 15,750 pounds per square inch (psi) – that equates to 8 tonnes (E-I-G-H-T TONNES for every square inch).

That pressure is unimaginable. If, somehow, you were placed down there, it would feel like 50 jumbo jets were placed on top of you…  yet organisms are still able to thrive here.

A recently captured CT scan of a Mariana Snailfish skeleton; the deepest living fish ever to be discovered. A crustacean is present within its stomach, revealing an organism it feeds upon. Photograph taken by Adam Summers. (Sourced)

A recent breaking discovery is that of the Mariana Snailfish (Pseudoliparis swirei), the deepest living fish to ever be discovered. The snailfish inhabits the Mariana Trench reaching depths of up to 8,178 metres. This is an astonishing depth for any vertebrate to successfully live in, considering the extreme pressures these fish are exposed to. On top of the unbelievable pressure, these fish are exposed to the cold temperatures of the deep, plus no light to search for food.

Light

It is eternally dark at these colossal depths, since no light from the Sun can penetrate beyond 1000m deep. This means that no photosynthesis takes place, so any photosynthetic organisms cannot survive down here, meaning zero herbivores can exist. Instead the primary producers of such environments are chemosynthetic organisms such as bacteria.

Hydrothermal Vents

Hydrothermal vents are another challenging environment within the Mariana Trench, producing large amounts of pollution from the hydrogen sulphide and heavy metals expelled which create a toxic environment, along with very high temperatures (above 400˚C).

Organisms are able to convert the toxic pollutants expelled from hydrothermal vents. Bacteria are chemosynthetically adapted to convert the hydrogen sulphide from the vents (smokers) into energy. The bacteria promote animal life around the smokers as they form a symbiotic relationship with giant tube worms, converting the toxic pollutants into energy (within the specialised organ; trophosome) for both organisms.

 

How do these environments relate to the search for alien life?

The Mariana Trench and other environments within the deep-sea allow astro-biologists to extend the parameters of their searches to include more factors and therefore include a greater number of planets and moons. One such limitation involves photosynthetic life such as plants and their ability to convert sunlight into energy, which an entire ecosystem will benefit from. But now since the discoveries of symbiotic relationships animals have with chemosynthetic bacteria in different environments, a higher abundance of planets residing outside of the habitable zone (Optimal range in distance that the planet or moon is from the Sun) can be considered as potential habitations for life, as well as methane- or sulphide-rich atmospheres.

In conclusion, the oceans cover a significant part (70%) of the planet and only recent technological advances have enabled extensive oceanic exploration and research. Still, less than 5% of the oceans have been explored, thus, 95% remains undiscovered. The sheer amount left to be explored on Earth limits humanity’s understanding of life outside of the planet.

 

 

 

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