Extraterrestrial life has been theorized to exist for centuries. From planets and moons within our own solar system, to planets orbiting in other star systems spread across the galaxy, the thought of alien life has fueled both science fiction and science fact. But is there really life out there somewhere or is it just us here on planet Earth?
Aliens in Science Fiction
Aliens have been written about in science fiction since True History by Lucian of Samosata was published in the second century BCE. Today, many science fiction movies and novels paint a picture of Earthlings and aliens living and working together to achieve common goals. Star Trek, Star Wars, Babylon 5, Farscape, among others give us some ideas of what aliens may look like, how they may interact, how they live within their civilizations, and how our civilization would benefit from these friendships.
Others such as War of the Worlds, Independence Day, and Invasion of the Body Snatchers show aliens coming to Earth to abolish life on our planet (and of course, since these stories were created by Earthlings, it only makes sense that humans triumph over the alien threat). I wonder if Earth really were to be attacked by aliens coming in large starships, what would our fate actually be?
Scientists for Aliens
Many scientists have long believed in life existing on other planets and moons. Scientists such as Carl Sagan popularized the search for extra terrestrial life bringing it more into science rather than simply science fiction and Frank Drake even created an equation that may suggest the number of civilizations that we may be able to communicate with (although many of the variables in the equation are quantified by guesses and hypothetical situations). The SETI (Search for ExtraTerrestrial Intelligence) Institute, founded in 1984, specializes in astrobiology and understanding the origin and nature of life in the universe.
Scientists used to be thought of as ridiculous to even think that life existed anywhere other than our planet, similarly to how many were shunned to even think that the Earth wasn’t at the center of the universe. But when science fact and technology catch up to science fiction, the once impossible is now probable and even very likely.
Life in our Solar System
We know that life does in fact exist within our Solar System as evident by this article being written and it being read by you. For generations, our neighboring planet Mars has been looked to as a possible place where life may exist. From Edgar Rice Burroughs’ Princess of Mars to H. G. Wells’ War of the Worlds and from The Day the Earth Stood Still to Mars Attacks, life on Mars has been portrayed many different ways. But does life actually exist on Mars? While there is no plant or animal life on Mars, there are organic molecules that have been discovered on Mars. These organic molecules may be some of the building blocks of life but they are not life in of themselves.
In addition to Mars, Enceladus, Titan, and Europa are primary locations to search for life. Enceladus and Titan are moons of Saturn and Europa a moon of Jupiter. Enceladus and Europa are both water rich moons in which the water is both in liquid and solid forms. Both moons experience tidal forces from their parent planets that keep their interiors warm and their water in liquid form beneath the icy surfaces. Geysers of liquid water have even been observed on Enceladus. There are potential plans to send missions to both Europa and Enceladus in order to search more closely for conditions necessary for life.
The Huygens probe, which plunged through Titan’s atmosphere in January 2005, revealed features similar to Earth. A thick methane and nitrogen rich atmosphere that is believed to be similar to the atmosphere of a very young Earth also covers Titan. Lakes, rivers, and seas of methane have also been found over the surface of Titan, similar to the lakes, rivers, and seas of water on Earth. And as with Europa and Enceladus, a large liquid ocean is believed to exist beneath the surface. The methane that is found in various forms on Titan is also a building block for life as methane is typically produced from organic materials.
There are several other bodies within our solar system that are being studied in order to determine if life ever or could exist. But so far, no little green men have been found.
Exoplanets and Potential Life
Exoplanets, short for extrasolar planets, are planets that are in orbit around other stars. At current count, there are over 3300 confirmed exoplanets with nearly 2500 still waiting to be confirmed just from the Kepler Space Telescope. While very few of the known exoplanets could be habitable, techniques for discovering new exoplanets are constantly improving. Also improving is our understanding of these alien worlds and what we can look for in order to detect habitable conditions.
There are several methods to search for and discover exoplanets from directly taking an image of the planet by blocking the light of its sun, to observing the effects that the planet has on its host star however, amateur astronomers and enthusiasts would struggle to find such planets with brand-name retail telescopes due to their limitations. There are also several ideas for how we can search for life on these distant planets. And while the technology isn’t quite there, scientists are not giving up on continuing their search for life in the universe. The first step is to determine if the planet is rocky, then if it is in the habitable zone of the star (where liquid water would exist), then if it has an atmosphere that has signs of gases that by our standards would be indicative of life.
Another method made popular by the movie based on Carl Sagan’s novel Contact is listening for a signal coming from outer space using radio telescopes. Assuming that life on other planets is similar to or more advanced than our civilization, signals should be broadcasting from the planet, such as those for television and radio. The wavelength of these signals would be picked up from radio telescopes on Earth, assuming they were pointed in the correct direction.
Will we ever find another advanced civilization?
With all of our searching for life within our own solar system and on planets in other star systems, will we ever find it? Planets around other stars have gone from fantasy to commonplace with more Earth-like planets being discovered within their parent star’s habitable zone. Technology is improving so that we can both study our nearby neighbors in greater detail and eventually be able to discover telltale signs a distant planet has or had life.
We may not have found any alien life as of yet, but technology and the human desire to search will never cease. Ellie Arroway, the head scientist in Contact, stated it best when she said, “The universe is a pretty big place. It’s bigger than anything anyone has ever dreamed of before. So if it’s just us … seems like an awful waste of space. Right?”