What Would Extraterrestrial Life Look Like?

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There are at least one sextillion stars in the observable universe, so it only seems rational to think about extraterrestrial life, what it might look like and how we’ll find it. We might have yet to see any direct evidence that life on other planets exists, but then we hadn’t even discovered the first planet beyond our solar system until the confirmation of the existence of one orbiting a distant pulsar back in 1992. Today, we’re getting closer and closer to discovering the life beyond the borders of our world, and there’s a pretty good chance that we’ll discover it in our own solar system before we have definitive evidence of the existence of life amongst the stars.


Dubbed a super Earth, Kepler-62f is one of the more likely candidates for extraterrestrial life. However, being significantly bigger than Earth, and home to a very different environment, any life there will likely be very unfamiliar to us.

Complete Fantasy, Pure Speculation or an Educated Guess?

Almost all popular representations of extraterrestrial life, particularly of the intelligent kind, fall into the realms of complete fantasy. Filmmakers, for example, typically want to create characters that people can relate to, and they also have budgetary constraints to think about when it comes to special effects and the like. As such, most aliens depicted in film are humanoid and, in the case of Star Trek, seem to breathe oxygen and, even more incredibly, speak English. In other cases, alien lifeforms are designed to look as terrifying as possible to compliment the theme of the story, such as the infamous xenomorph in the Alien series.

Pure speculation takes a rather fantastical approach as well, albeit not for the same reasons and, to an extent, it’s usually rooted in some sort of science. For example, just as a person would swat a fly, there may be aliens out there that are so much more advanced than ourselves that we couldn’t possibly relate to them and vice versa. As such, they might swat us aside as we would swat aside the fly. Similarly, there may entirely different biochemistries which, instead of being carbon-based, may be based on other elements that can form the complex molecules required for life, such as silicon, boron or even sulphur. Ultimately, however, we simply don’t have a clue, hence the pure speculation.

Now we get to the interesting part, interesting because it is tangible, something we can relate to and something we can actually find. In the search for life on other planets, we need to look for what we’re familiar with, and that means that science must lead the way. As such, it’s perhaps better to redefine our search for extraterrestrial life into the search for Earth-like extraterrestrial life. And no, that doesn’t mean looking for space hippies or tribbles; it means looking for that which we can define as life, whether it’s microbial or something much, much bigger. In other words, that means looking for the building blocks of all life as we know it:

  • The necessary elements for biological chemical processes to take place
  • DNA and RNA, or something equivalent, for encoding genetic information
  • A solvent, such as water, to allow the chemicals of life to develop
  • An energy source, such as the Sun or deep-sea hydrothermal vents
  • An environment that’s stable for long enough for life to develop

Fortunately, the basic building blocks for life are thought to be plentiful throughout the universe and, indeed, in our own solar system. There’s also a possibility that certain elements which, while critical to all life on Earth, may be substituted by something else. For example, arsenic may take the place of phosphorous as an essential building block for life. The methane seas of Saturn’s moon Titan may take water’s place as the solvent necessary to promote the chemical reactions required to form the molecules that make up living things. On Jupiter’s moon Europa, the hydrothermal vents could sustain life independently of the Sun. Such environments have more in common with our own than you might imagine.

Based on the above, it’s easy to assume that life on other planets would look much like that here on Earth, but nothing could be further from the truth. After all, life on Earth is incredibly versatile, and there are countless millions of different species, and more are being discovered all the time. Added to that is the fact that life on Earth has been going strong for at least 3.5-billion years, seeing countless extinctions in the process. Ultimately, there’s not much in common between a prehistoric bilateral sea pen-like creature and you or I. In other words, you only need to pay a visit to your nearest zoo to see just how different our own critters look.

Should life develop on a planet that shares very similar characteristics to life on Earth, which would be quite a coincidence if it happened in a solar system anywhere near our own, it stands to reason that many among its lifeforms would look similar to our own, at least in terms of fundamental characteristics. We have yet to find any evidence of a truly Earth-like planet, but that certainly doesn’t mean that life can only develop on an Earth analogue. Because all potentially habitable planets we’ve seen are not really very Earth-like at all, any possible life on them will be very different to what we’re used to, since it will be an evolutionary product of its unique environment.

The sensationalist media loves to talk about so-called habitable zones around stars, where the surface temperature of a planet should be about the right temperature to accommodate life as we know it. However, this hypothesis fails to consider just about every other possible variable. For example, Europa is far beyond the habitable zone of our own star, yet its subsurface ocean, kept liquid by tidal heating from Jupiter, presents by far the most promising environment for life in our solar system. On Mars, which is just outside the habitable zone, certain microbes from Earth can live and may even be able to reproduce.

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