Imagine coming face face to face with an alien. What would it like look like? We could have a clue. The universe is a vast and mysterious place. It is hardly believable that we, Earthlings, might be the only ones living in it. There are around 40 to 60 billion earth-sized planets orbiting in the habitable zones in the Milky Way galaxy alone.
The odds of finding extraterrestrial life on one of these planets remain high, but how can we determine their appearance? In movies and science fiction novels, aliens are mostly depicted as humanoids. Very much like us because that is the simplest form our brains can process. But whether aliens are small or big, thin or thick, tall or short, have multiple limbs or noses, all can be guessed based on the environment they live in.
Not only that planets are so different from each other in size and environment, the rules of Physics and Chemistry across the universe might not always be the same, meaning that creatures potentially face different challenges when trying to survive.
One such aspect is gravity. If a planet has high gravity, the living creatures would have a hard time lifting itself from the ground. Even if it manages to do so, it will still be challenging to keep its balance. That is why it might evolve extra limbs to help it stand, balance, and move. For example, KEPLER452B which is often called a cousin of Earth, has very high gravity.
If some creatures live on it, it is possible that they will be flat, close to the ground, like worms. On the contrary, in places with low gravity, the creatures could easily glide. Here, they might need a few extra hands to hold on to things to prevent them from flying off. They could also be taller than the creatures of Earth, just like how astronauts grow taller in zero gravity.
Another influence comes from AIR DENSITY. If the air is too thick, more living creatures can fly, just like we swim in the water here on Earth. On the other hand, if the air is lighter and full of oxygen, living creatures might evolve to produce more energy and have energy demanding powers. Just like humans, extraterrestrial life would also require generating its own energy.Humans do this by eating and generating energy from food. Aliens could evolve very different ways to gain energy, which could influence the way they look. For instance, they might feed off cosmic rays like one type of bacteria on Earth that lives on radiation from uranium.
It is possible that in places with little energy available is many times smaller. But it does not mean it won’t be as complex. The world outside the planet and the planet itself can also influence how life turns out. Some planets that orbit around their stars might not be round, but elliptical instead. The winters there are long and very cold because the planet travels far from the sun for a long time.
There are many ways for life to adapt to such harsh conditions just like animals do on Earth with fur. If the planet would get too much radiation, aliens on it could look more like plants that can quickly roll up and hide when solar flares happen. The planet might not have a star, in that case, it will be dark and cold, but life could still thrive. On Earth, in the darkest places where there is no sunlight and the temperature is very low like the bottom of the ocean, there exist microbes, worms, clams, and shrimps. At the same time, different aliens could still compete against each other, driven by natural selection.
The fight for energy could lead to the emergence of predators and prey. This means that some aliens could have developed ways to hunt other aliens down, same as Earth predators have fangs or strong muscles to chase their preys. The preys would also develop ways to protect themselves like camouflage. But when is it that we will finally meet our extraterrestrial neighbors and we will even be able recognize them?
We might find out through missions like the TESS MISSION which is studying potentially inhabited plants outside our Solar system, and NASA’s mission to EUROPA which will explore the fascinating moon of Jupiter that has more liquid water than Earth.
Nevertheless, we cannot know for sure what aliens would look like unless we see them. Thus, regardless of all predictions, we might be in for a big surprise.
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