The concept of life beyond the borders of our tiny little rock has been a staple in science fiction for over a hundred years and humanity has long been asking if we are alone in the vastness of the Universe. The answer is that there surely must be life out there. The Universe is so big that it would seem to be an impossible coincidence for there not to be. Whether we will ever discover it and prove its existence, however, is another matter. Nonetheless, there currently exists some compelling evidence that life does indeed exist out there.
1 – Planets around Other Stars
Although scientists have always assumed that our star, the Sun, is not unique in that it hosts a number of planets, it was not until 1992 that the first planet orbiting another star was confirmed. Since then, and thanks to advances in technology and detection methods, many hundreds more have been discovered and it is now believed that these exoplanets number in the billions in the Milky Way galaxy alone. That exoplanets exist and in huge numbers too, dramatically boosts the chance of finding life beyond Earth.
2 – Not All Life Is Dependent on Sunlight
Until a few decades ago, it was assumed that all life on Earth was dependant, directly or indirectly, on sunlight. Even organisms living several miles beneath the surface of the oceans, far below where any sunlight can reach, are indirectly dependent on sunlight due to the nutrients they receive which comes from life forms closer to the surface. However, there also exist completely independent biological communities around hydrothermal vents, using these undersea geographical formations entirely for their energy requirements. It is now believed that similar forms of life could exist in underground oceans on Jupiter’s moon, Europa, among various other places in the Solar System.
3 – Water Is Not that Uncommon
Not so long ago, there was no definitive evidence that there was water anywhere else in the Solar System other than on Earth. It is now known that water is actually very widespread, at least in the form of ice. Liquid water may even flow in small amounts in the depths of some of the craters on Mars although, the surface pressure is generally so low that it would evaporate instantly. However, the ubiquity of water has now been proven and it is assumed that it exists on numerous astronomical bodies in our own planetary system and beyond. Water, of course, is the key ingredient for all life as we know it.
4 – Martian Meteorites
We may have even discovered extraterrestrial life already. There are currently well over a hundred meteorites discovered on Earth which originated from Mars in the distant past. The Allan Hills meteorite, discovered in 1984 in Antarctica, for example, is believed to be around four billion years old when Mars was likely a lot more hospitable than it is now. Electron microscope images show evidence that this rock has microbial fossils in it. Another famous one is the Nakhla meteorite, which contains amino acids which may have originated from ancient Martian life.
5 – Evidence for Alternative Biochemistries
There does not appear to be any substantial reason why all life should be carbon-based and rely on water. Just because this is the case on Earth, does not necessarily mean that there cannot be completely different biochemistries. It has long been proposed, for example, that life could also be silicon-based or even based on boron or sulphur rather than carbon. Instead of relying on water, life may, for example, rely on methane. Saturn’s moon Titan, as the only body in the Solar System beyond Earth to boast surface liquids and the only moon with more than a trace atmosphere, has become particularly interesting in the search for life. This alien world has lakes and rivers of liquid methane as well as methane rain and snow rather than water.
So, in light of this information…aliens exist!