Urban Dynamics Blog

Classifying cities on other planets

By Matt Johnson

Human cities are thousands of years old. The first small cities probably emerged not long after the transition from foraging (hunter and gatherer) groups to horticultural groups to agricultural societies. They also more than likely emerged around some sort of body of water like a river, a lake, or adjacent to an ocean or sea body.

A Tycho City

A Tycho City – Urban Dynamics

In fact, many of the great human cities in human history in South America, Africa, Asia, Scandinavia, and North America (both in ancient and modern times) emerged around a body of water. This is because water is the life-blood of all the species on this planet and humanity is no exception. If one accepts the scientific theories of Charles Darwin and Alfred Russel Wallace, then one accepts the importance, the magnitude, and the role that water plays in the survival of all the species on this planet. However, humans have taken the importance and application of water a few steps further.

Since water is so important, it will play a big role in the expansion of the human species as it expands throughout the solar system and beyond. Space agencies such as NASA, the ESA, and the China National Space Agency (CNSA) will be thinking about where to land astronauts and water will play an intricate role in this decision. And if history is any indicator, cities will eventually emerge around these landing sites.

Moving forward into this exploration of terrestrial cities and extraterrestrial cities, I would like to provide this study and examination with some much-needed classification language. Like Carl Linnaeus’ classification system for biological species, I believe that a classification system is needed to provide a more scientific discussion of cities.

For example, there are thousands of cities that reside on this planet. There are small cities, medium size cities, and large cities. Is there a taxonomical difference between these cities? What happens if a city emerges on Luna (the Moon) or on Mars or on Ceres? How would we refer to these cities? How would they be different? How would they be the similar?

An Exo City - Urban Dynamics

An Exo City – Urban Dynamics

And what about exo-cities? Those are the human cities that will exist on exoplanets (planets in other solar systems) far into the future. How will these cities be different or similar to those cities on Mars or Ceres, or cities here on Earth? Time will tell, but an early and rough classification system will provide urban dynamicists and astro-urban dynamicists with an immediate language to study and discuss these cities.

I submit that cities can be classified and described in three general areas. First, cities can be classified and described in the terrestrial notion. Those are the cities that already exist here on Earth. I will refer to these cities as Terran (from the Latin) cities.

Second, cities can be classified and described in the extraterrestrial notion. But more specifically, in Sol’s (our parent star) solar system notion. That is, those cities that will emerge and reside on Luna, Ceres, Mars, and possibly other planetary bodies in this solar system. These cities should emerge within the next 100 to 300 years depending on human motivation and ingenuity, political and government motivation, and technology.

Third, and finally, cities can be classified and described in the exoplanet notion. This is where cities emerge on planets in other solar systems. This study and examination is much more speculative and dependent on recent and future exoplanet hunters, what they find, and what the composition of the planets found. These cities probably won’t exist for another few hundred years to probably a thousand years depending on human motivation and ingenuity, political and government motivation, and technology.

Here is the first draft and submission of The Big Picture of city classification:

  • Terran City – A city that resides on Earth.
  • Tycho City – A city that resides on a planetary body or moon in the Sol system (our solar system).
  • Exo City – A city that resides on an exoplanet in a solar system outside of this solar system; for example, Kepler 186, Kepler 438, Kepler 442, Gliese 581, and Gliese 667 provide strong possibilities for future ex0-city sites. Here is the list of current and potential exoplanets.

For further reading on this subject, I invite you to read Tycho City, A City on Mars, and A City on Mars: A Response to Elon Musk. Remember, you are always welcome, and encouraged, to post your comments, thoughts, and predictions below. Feedback is always appreciated.


Matt Johnson is a writer for The Systems Scientist and the Urban Dynamics blog; and is a mathematical scientist. He has also contributed to the Iowa State Daily and Our Black News.

You can connect with him directly in the comments section, and follow him on Twitter or on Facebook

You can also follow The Systems Scientist on Twitter or Facebook as well. 



Copyright ©2016 – The Systems Scientist

2 replies »

  1. Is city classification at this level to small of scope? In the dynamics of extraterrestrial exploration and settlement would colony and planetary classification not be a more pressing method? While I get what you mean here I would argue that classification other than city is irrelevant, unless it is classification based on primary function. Think of it like continents. The Brits did not call new cities in Australia something other than a name, or there is little in names of terrestrial cities to specifically point at thier locations other than language….and world knowledge. So maybe we will just have to know that New Minneapolis is on Mars.

    Liked by 1 person

    • Thanks for the comment, brother! I don’t believe so. For someone thinking about cities, I believe it is at the right level. Here’s why.

      In regards to a colony, urban history indicates that cities emerge from forts or settlments. Minneapolis and Fort Snelling, and Detroit and Fort Wayne, which Fort Lernoult before that and Fort Detroit before that dating back to 1700 or so, are examples of this very idea. With that said, a strategic landing site would come first followed by some sort of base, then a settlement or colony, and then eventually a city. If we use Minneapolis and Detroit again as examples, then this new city would take between 100 to 300 years to become a city.

      In regards to city classifications, I must admit my biases on this point. I will leave planetary classifications to the astronomers and planetary scientists. They are doing a rather superb job and thus making my job much easier. I don’t believe it is every to early to begin speculation of something that will more than likely in the future. To evoke a bit of leadership theory into this conversation, Tom Rath and Barry Conchie argue in their 2008 book ‘Strengths Based Leadership’ that Futuristic is one of 34 StrengthFinder Themes. As they explain, “People strong in the Futuristic theme are inspired by the future nd what could be. They inspire others with their visions of the future” (171).

      By no means is it empirical, but I believe there is some truth to the argument and exercise. I believe my hero Gene Roddenberry had this ability. I imagine that most science fiction writers do, especially the good ones.

      With that said, I think this conversation is worthwhile and could lead to productive strategic and logistical thinking, and possibly even planning, with respect to future landing sites on other planets. It certainly is possible that a mission to mars could end up like a mission to the moon; that is, astronauts go, survey, grow potatoes like Mark Watney in the book ‘The Martian,’ and then return to Earth. However, maintaining a base of operations is also an option. It depends on the economic, political, and social motivation.

      But if they decide to stay?


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