Thursday, May 28, 2015

Will humans populate the exo-planets?

Picture of MarsThe more I read about the strangeness of our universe, the more I wonder if humanity will ever colonize other planets. There's not much chance we'll settle on a diamond planet and I have to wonder how we'd go on many of the 'earthlike' planets already pinpointed. We are such fragile entities, we humans.

Like all other animals we are closely attuned to our environment, more so than many of us realize anymore. In these days of electricity we can heat or cool our homes, spend half the night watching TV or reading books, source food from all over the world so nothing is ever out of season, cross distances that took years in days. Yet we cannot escape the environment which shaped us.

I think there are five vital factors we will not easily overcome.


Time is relative. When it's 8am on a Thursday where I live, it's 6pm the previous day in New York. Yet it's the same 'time'. However, the elements that we use to measure time have a profound impact on our bodies. By that I mean the rotation of our planet, and its orbit around the sun. Whether we think the sun is rising where we are, or setting, our bodies are built to expect a 'day' of twenty-four hours or so, because that's how long it takes the Earth to revolve on its axis. What's more, if we are suddenly wrenched from one time of day to another, as happens with long distance air travel, it takes time for our bodies to adjust. (It's called jet lag.)


We have evolved to suit the amount of force the planet exerts upon is. The advent of space travel and weightlessness has proved how important gravity is to our ability to function. Without gravity our bones lose density and muscles atrophy. Returning astronauts struggle to rebuild their bodies. In science fiction space ships have ways of providing gravity, either by centrifugal force, like the rotating space station in 2001: a Space Odyssey, or via an unspecified means of creating artificial gravity, found in Star Wars, Star Trek and the like. Long periods on a planet with low gravity is sure to have similar effects. Mars and the Moon are obvious examples. Sure, you can bounce around. But what happens if you come back to Earth? Or move on to another planet with much stronger gravity than Earth?


Most of our atmosphere is nitrogen, with twenty-three percent oxygen and a bunch of other gases in smaller quantities, including carbon dioxide. It also has a level of density. There's more of it at lower altitude (see gravity). See what happens to mountain climbers if they climb before becoming acclimatised. Their bodies can't cope. And if that mixture of gases changes past a certain level of tolerance, then what? Sure, we can wear space suits. But that's not ideal if you're colonizing a new planet.


Humans exist in an apparently wide range of climates, providing they can find protection from the elements. But the range is actually not that wide in the scheme of things. This article in New Scientist speculates that global warming of only about 11° would render many places on our own planet 'unlivable'.


Earth orbits a G class star which emits light towards the red end of the spectrum. We're used to seeing colors in that light. If we lived on a world orbiting a cooler star with redder light, or a brighter star with more bluish light, we'd see colors differently. For example, with light from a red star, blues and greens would be brighter, and reds and oranges more subdued.

Humans are adaptable. That's why the species has been so successful. But even so, we've only ever had to adapt to the extremes of one planet. If humans are to venture to other planets I believe we will have two choices; terraform the planet into another Earth or modify the settlers to cope with the conditions. That would mean physically very different races of humanity occupying different planets.

And here again, SF can offer plenty of examples. Elizabeth Moon's Serrano series has terraformed planets, as does Jack McDevitt's universe in Slow Lightning. A different approach is taken in Moon and McCaffrey's joint effort, Sassinak, where members of the Star Fleet have different body characteristics, depending on which planet they come from.

I admit I don't take that route in my own writing. Like the Star Treks and Star Wars of this world, I simply assume all planets are earthlike, with only small variations in light, heat, time and gravity. I reckon I'm in pretty good company. Come on SF fans and writers, what do you do, what do you prefer? Can you think of other limiting factors? Or do you think I'm pessimistic?


  1. I think you're right on, Greta. The effect of gravity on a body is explored in a Deep Space Nine episode where Basheer develops a crush on a station crew member from a planet with lighter gravity. The Earth-like gravity of Bajor and the station are wreaking havoc on her body and she's in a wheelchair most of the time.

    I do the Wars/Trek thing too, with artificial gravity on my ships and Earth-like planets. We are adaptable as a species, but it only goes so far. While I can see a future humanity exploring planets unlike Earth, I don't see any ability to set up a long-term colony or create a civilization there. The odds are just too much to overcome.

    1. Yes, unless we become something other than the humans we are today, I agree with you. Thank you for engaging.

  2. Lots of SF authors had fun with humans adapting to other worlds, either slowly by evolution or the quick way by genetic engineering. I seem to recall a Star Trek Next Gen episode where a small, slender man had extraordinary strength because he came from a heavy-gravity world. In my Central Galactic Concordance series, they only terraform planets that are earthlike, though minor variations in orbit period, day length, and gravity are allowed. Saves me endless trouble explaining things. ;-)

    1. I think there will be plenty of earthlike planets out there. And yes, endless trouble ;)

  3. I've got terraformed planets, a runaway terraformation on Mars, and some planets with extreme conditions where humans have to wear "survival" suits for protection.
    The time to get to a planet is the main limitation, and terraforming with oxygen-generating bacteria is possible but would take many years.

    1. Travel time is a huge consideration right now, agreed.

  4. I think the degree of difference--in gravity, temperature, light, etc.--will determine which planets are selected for long-term colonization and how successful those efforts will be. As you say, Greta, humans are amazingly adaptable and have acclimated to a wide variety of environments on THIS planet--from subzero to tropical, desert to rainforest, sea level to high mountain. I believe we can adapt to conditions on another planet in the same way, as long as the adaptation is truly long-term, that is, that the colonist is not going back and forth between Earth and new planet. At first heavy use of our technology might be required to allow us to function; within generations that might not be the case. But then, I'm an optimist. :-)

    1. I think it will happen - but the people who populate other planets may well not look like us - ie genetic engineering. Of course, if we find truly earthlike planets, that won't be necessary.


Comments set on moderation - all spammers will be exterminated!

About Spacefreighters Lounge

Hosted by 5 Science Fiction Romance authors with 8 RWA Golden Heart finals and a RITA final between them. We aim to entertain with spirited commentary on the past, present, and future of SFR, hot topics, and our take on Science Fiction and SFR books, television, movies and culture.