Space Colonization. We will not travel alone

Various estimates put Earth’s carrying capacity for Homo sapiens at or below eight billion. We have just crossed that boundary, one more, so choices are necessary.

An alternative to degrowth is to create more living space, e.g., habitats orbiting Earth or on the Lunar or Martian surface. The idea of space travel and humans living in space dates to at least 1608. After the invention of the telescope Johannes Kepler had a dream, and he wrote to Galileo in 1610:

“Let us create vessels and sails adjusted to the heavenly ether, and there will be plenty of people unafraid of the empty wastes. In the meantime, we shall prepare, for the brave sky-travellers, maps of the celestial bodies.”

More than 400 years later we are still working to make that dream a reality, and no, I am not going to write about Musk (nor Bezos).

Dr Paul Lister Smith, Honorary Senior Associate Teacher at Bristol University, and founder of Botannical Investigations, a consultancy, has just published a paper on the question concerning Extraterrestrial nature reserves (ETNRs)(1), as envisaged in Douglas Trumbull’s 1972 film Silent Running(2).

A case is made for developing a contained facsimile, old growth forest on Mars, providing an oasis, proffering vital ecosystem functions (a forest bubble). It would serve as an extraterrestrial nature reserve (ETNR), psychological refuge and utilitarian botanic garden, supporting species of value to colonists for secondary metabolites (vitamins, flavours, perfumes, medicines, colours and mood enhancers).

Paul argues that a contained extretaterrestrial reserve could be established on Mars, as a first step to terraforming the planet. Assuming containment can provide tolerable conditions, Mars offers gravity, atmosphere, sufficient sunlight for photosynthesis and water (ice), while proximity to Earth allows management.

Relative characteristics of Earth and Mars

But the key question Paul Smith discusses in the paper is related to the living orgamisms that will be part of the journey.

The sailing ships of past explorers were not sterile. They carried animals for food and as living cargo, for companionship and as pests. Sometimes, animals were released or escaped onto foreign shores where some thrived or became problematic, examples of accidental, incidental and deliberate dispersal of Terran species. Goats were once purposely liberated on remote islands by mariners, as a self-renewing food resource. Such attitudes may become necessary during space exploration, creating oases on barren but habitable planets. Spacecraft will carry multiple species complements, contributing life support for long journeys and on arrival at lifeless destinations.

Consideration of the necessary species complement of an ETNR supports a view that it is not humanity alone that is reaching out to space. We need plants as chemical factories, producing secondary metabolites with greater ease and more autonomy than industry.

We will not travel alone because we did not evolve in isolation. Homo sapiens was shaped, over aeons, by other species and will travel with a mutually supportive system of Terran organisms amongst which we fit, exchanging metabolites as we have evolved to do.

It is not humanity that is reaching out from Earth, it is life.

Unless of course, singularitarians and the coming race of superintelligent robots do not have a different idea.


(1) Smith, Paul L. ‘Extraterrestrial Nature Reserves (ETNRs)’. International Journal of Astrobiology, 24 November 2022, 1–39.

It is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (, which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.

(2) Silent Running is the only reference to science fiction I’ve found in the paper.

Featured Image: Silent Running


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