Imagine yourself at the bottom of the ocean able to withstand more than 200 times the pressure you’re experiencing right now, near freezing temperatures, and of course being able to see in the dark.
Now imagine that you’re not just anywhere on the sea floor. Imagine youself staring at a towering rock structure glittering with fools gold and spewing what looks like black smoke into the surrounding seawater. You are now staring at one of the thousands of hydrothermal vent chimneys that are found in particular locations on the ocean floor.
Some say life on Earth originated at hydrothermal vents. Others speculate that geological features like hydrothermal vents likely exist elsewhere in our solar system on places like Jupiter’s volcanically active moon Europa. For these reasons hydrothermal vents here on earth are often used as analogue environments to help astrobiologists figure out how best to look for extraterrestrial life.
So why are these vents so important, and why should we attempt to better understand inner space life in order to better look for life in outer space?
As you all know, we depend on the sun’s energy to power photosynthesis which enables plants and other organisms to produce the bioligical material (or biomass) that is the foundation of most food chains in most ecosystems on Earth. Not all ecosystems though...
At hydrothermal vents something very different happens, and it is this something that we think might be happening on other worlds that are too far away from the sun or covered in ice and therefore unable to be able to use the sun's energy to generate biomass. By any definition these vent chimneys represent extreme environments... extreme pressures, temperatures up to 400°C, near complete darkness, and it is in these extreme environments that microbes harness energy from chemicals spewing from the earth, rather than energy from the sun in a process called chemosynthesis to create living material.
This process, of chemosynthesis, could -in theory- occur and form the basis of food chains and ecosystems anywhere there is volcanic activity and water. In hydrothermal vents on Earth microbes garner energy from gasses like methane, sulfide, sulfate, or hydrogen.
One major reason that hydrothermal vents are my favorite thing to think about and study is that the process of doing so is inherently interdisciplinary.
We need geologists to tell us how seawater gets entrained in the seafloor, how it interacts chemically with the crustal rock and transforms in to hot, metal-rich hydrothermal fluids, and how it is then responsible for the awe inspiring structures I had you visualize a minute ago.
We need chemists and bioenergetic modelers to look at the composition of these fluids and predict what chemical reactions are favorable that might provide energy life.
And we need biologists (like me!) to look for life in and on the walls of these chimneys and tell us who is there and what they are actually doing.
We also need engineers to help us build instruments and vehicles that can access these environments and collect the samples we need.
So, by studying how microbes eek out a living in one of the most extreme environments on Earth, by asking questions about how specifically they generate biomass, what metabolisms they carry out, and what are the factors that limit life in these extreme enviromnents, we may actually be learning how alien microbes are surviving or even thriving on distant worlds.