For centuries, the notion of extraterrestrial life has captivated the human imagination. When we imagine life on other planets, we often envision creatures similar to those found on Earth, breathing in the same air and reliant on oxygen. However, recent scientific discoveries and groundbreaking research have challenged the long-held assumption that alien life forms require oxygen to exist.
In other words, aliens shouldn’t have to breathe oxygen. Although humans need oxygen to survive, our planet’s atmospheric layers are composed of various gases, not just oxygen. If we look at the volume of gasses, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Our atmosphere, together with other essential factors, allows for life on Earth to exist.
But on a distant alien planet, this may not be the case. In fact, for all we know, an alien species in a potentially habitable world could generate carbon dioxide and produce oxygen. Humans breathe oxygen and produce carbon dioxide. For all we know, aliens can survive in a vacuum. We know that microbes can, and even organisms on Earth called Tardigrades–also known as Water Bears–can survive in space.
Take Tardigrades as an example
Tardigrades are teeny tiny micro-animals known to exist nearly everywhere, from mountaintops to volcanos, from tropical rainforests to the freezing climate in Antarctica. These little creatures are nearly indestructible. Tardigrades can resist a vacuum’s extremely low pressure and very high pressures–more than 1,200 times atmospheric pressure. Suppose animals on Earth, such as water bears, can survive in unimaginable places where humans can’t. Doesn’t that tell us–at least in theory–that alien life on distant worlds could survive just as Tardigrades do in extreme environments?
Astronomers are looking for similar words
When astronomers search for exoplanets in the Galaxy, we look for certain similarities that those plants might have with Earth. For example, experts believe life is more likely to exist on exoplanets that orbit their host stars in the so-called Goldilocks or habitable zone. This area around the star is perfect for liquid water to exist on the surface. This is important because we believe there could be life where there is water. This is because so far, the only life we know is hurt carbon-based life, and without water, it would be possible. That’s why it is reasonable to assume that exoplanets with water on their surface may have also developed life.
As of May 12, 2023, there are 5,347 confirmed exoplanets and 9,618 candidates. Many of these worlds orbit their stars in the habitable zone, and a green number of exoplanets are similar to Earth, at least in size and mass. This doesn’t necessarily mean there could be life on those worlds, but the more similar an exoplanet is to Earth, the more likely it is to contain life, as we are concerned.
There are no rules for finding alien life
Although this is logical thinking, maybe we should look for what’s not entirely logical and start looking for exoplanets that are, in fact, the entire opposite of Earth. There are no rules as far as we are concerned when it comes to alien life. Until we confirm the existence of extraterrestrial organisms on a planet in our solar system, exoplanet, or satellite, we can assume that life can come in all sizes and colors. By that, I mean that there could be alien life forms out there that are so different from anything we are accustomed to seeing here on Earth that we could practically not even notice or process their existence.
The universe is a massive place
William Borucki, the principal investigator for NASA’s Kepler mission, explained, “If we find lots of planets like ours… we’ll know it’s likely that we aren’t alone and that someday we might be able to join other intelligent life in the universe.” However, if we don’t find a bunch of exoplanets similar to Earth, we probably should know that we are not the only planet with life and that we are not alone out there. The universe is a massive place. Our Galaxy is enormous, and our solar system has barely been explored.
Do aliens need oxygen to survive?
The idea that aliens don’t necessarily need oxygen or even the conditions that carbon-based life needs are backed up by a study published in Nature Astronomy. The authors say that we should start looking for planets that are not necessarily similar to Earth in size and mass and whose atmospheres are different from Earth, based, for example, on hydrogen and no oxygen. For all we know, alien life could need hydrogen, not oxygen, to survive.
For a rocky planet to have gravity strong enough to have a hydrogen atmosphere, it must be a “super-Earth” with a mass about two to ten times that of planet Earth. A chemical reaction between water and iron could also release hydrogen.
Alien life could need hydrogen to survive
This study demonstrated that alien life could need hydrogen to survive. Through a series of observations, the researchers discovered that the E. coli bacteria could survive and multiply under a hydrogen atmosphere without oxygen. According to studies, there is a “diversity” of dozens of gases produced by these bacteria, which would increase the chances of recognizing signs of life on an exoplanet dissimilar to Earth.
Looking at Earth’s “impossible” life
However, plenty of other microbes on Earth live within our planet’s crust and can survive by metabolizing hydrogen. Furthermore, teachers have even discovered multicellular organisms that can survive in an oxygen-free zone on the floor of the Mediterranean. Although the above is not evidence that alien life must exist in such worlds, it is a good argument that tells us that we might need to change our approach when looking for distant worlds that could harbor life.