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Terraforming and Colonizing Mars

Giancarlo Genta

Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy

Abstract

Humankind is on the verge of becoming a multiplanet species, but the main obstacle it has to face in this endeavour is that the environment of all celestial bodies in the solar system is very harsh, completely unsuitable for terrestrial-type (and hence, human) life. To colonize the planets, moons and asteroids of the solar system we must create artificial and enclosed environments, where we can live in shirt sleeves conditions. If on one side we are used to live in artificial environments since the neolithic revolution, in particular in some particularly harsh parts of our own planet, it is true that the colonization of the solar system could be made easier only if we start terraforming the places we aim to live in.

For many reasons, the first candidate of this terraforming effort is Mars, since the closest places (the Moon and Venus) are even worse. Terraforming Mars is a huge enterprise, which will take possibly hundreds years and very high costs. The essential aspects of this endeavour, scientific-technological, economical and ethical, are here discussed. In particular, an ethical problem is related to the possibility of existence of indigenous life: if on Mars there are indigenous living beings, most likely at the bacterial level, any effort aimed to terraform the planet likely would cause their extinction. Before any terraforming endeavour is started, a deep study aimed to exclude their existence must be undertaken.

Keywords: Mars terraforming, Mars colonization, greenhouse gases, multiplanet species, extraterrestrial life, planetary contamination, planetary atmospheres

1.1 Introduction

The human species has always experienced an urge to explore and to settle new territories. On Earth, it evolved in a small area in East Africa and from that beginning it expanded on much of the planet, at least in regions which could be easily reached just by walking on land.

It is likely that most of the individuals who participated in this process were completely unaware of it: a band of humans moving its camp by just 10 m each year (always in the same direction) would find itself 10,000 km from its original place in one million years.

However, things were not as easy as this: in many regions the climate was too harsh for humans to survive, and above all the climate in the various regions of our planet was changing continuously, with terribly cold ice ages and hot interglacial periods, and a continuous alternance of dry and wet periods.

To go through all this humans had to develop specific technologies, and also to adapt themselves with continuous evolutionary changes [1.11]. While the first process was quick enough to allow survival in a continuously changing environment, the latter were too slow and likely played a small role, to the point that in the last few hundred thousands years a single species, Homo Sapiens, emerged.

Homo Sapiens developed technologies which allowed to survive in the most harsh climates, particularly in cold climates, which are most difficult for a species developed in the hot African plains. It was observed that the wooden goggles that Inuit wear since the palaeolithic to prevent snow blindness and the multilayer skin garments they use in the open, and without which life would be impossible in these conditions, are as complex as the visor of a space helmet or the space suit we have to wear to explore space.

Apart from the technologies humans had to develop to survive in environments which were very different from those to which they were naturally adapted, later on in their expansion on the planet they had to develop transportation means which were essential for reaching, exploring and colonizing new lands. The most impressive examples are the boats and the navigation techniques developed in Neolithic times by Polynesians, which allowed them to settle practically all the islands of the Pacific Ocean, and the ships that at the turn between the Middle Ages and the Modern Age allowed the era of the geographic discoveries [1.4], [1.5].

Today humankind is at the beginning of a new era of exploration and colonization, and again it must develop enabling technologies to pursue its goals. From one side, the complexity of this new endeavour is unheard of, since, at least in the solar system, the environments in which the new human settlements will be located are much harsher than any environment of our planet, but from the other modern scientific technology, as opposed to the ancient technology based on trial-and-error attempts, is such a powerful tool that we can be reasonably sure that we have all the required means to succeed [1.11].

The point is thus not whether the human species, which developed on Earth, will be able to explore and colonize the nearby celestial bodies, transforming itself into a spacefaring, or multiplanet, species, but when this process will start (Figure 1.1).

1.2 Earth: A Terraformed Planet

Before starting considering these topics, particularly in the view of speaking of terraforming, i.e. modifying the surface and the atmosphere of a planet to make it suitable to human life, we must however go back in time to make some considerations about our own planet.

Our planet is roughly 4.5 billion years old. In the first half a billion years, the whole solar system was undergoing its process of formation, with continuous collisions of planetesimals and red-hot nuclei of planets which were forming. Then everything slowly settled out and our Earth cooled down, developing a solid surface, covered (completely or partially) by an ocean filled with the water carried here by innumerable comets. If we could land on our planet at that time we would find a planet completely unsuitable for human (and in general animal) life [1.9], [1.18].

Figure 1.1 Mars Base. Design by Martin Kornmesser and image courtesy of ESA.

The atmosphere of our planet would have been unbreathable, being composed by nitrogen and carbon dioxide, with no oxygen at all.

It was at that time, roughly 3.7 billion years ago, that the first life appeared, most likely in the oceans. And life started evolving in those conditions. The archeobacteria, and the other forms of life which followed, started using the huge amounts of carbon dioxide present in the atmosphere, producing oxygen. This slowly changed the composition of the planetary atmosphere making it suitable for supporting forms of life breathing oxygen, including human beings (Figure 1.2).

We can thus say that the first planet to be terraformed was Earth itself, and the actors of this transformation were the primitive forms of life like unicellular algae, which started the process, and then, in half a billion years, the plants which developed in the ocean to migrate later on dry land, which gave the finishing touch.

Figure 1.2 Relative abundance of CO2 and O2 (relative to the present one) as a function of time. Note the logarithmic scale [1.12], [1.13].

During most of this process, the planet had the aspect of a lifeless word - all life was concentrated in the oceans - and the only sign that Earth was a living planet was the presence of oxygen in its atmosphere.

This consideration, developed for Earth, holds for any planet and bear three important consequences.

• The only planets having an atmosphere which is breathable for humans and other animals are planets on which life - or better, Earth-like life - developed to become a very widespread phenomenon, so widespread that it changed completely the initial characteristics of the planet. Moreover, to have a breathable atmosphere, a planet must still have life: if for any reason life disappears from the planet, owing to the high reactivity of oxygen, sooner or later the atmosphere would revert to its pristine conditions.
• The presence of oxygen in the atmosphere of a planet is a marker for the presence of (Earth-like) life.
• During the process of formation of a breathable atmosphere the anaerobic lifeforms of a planet are substituted by aerobic lifeforms, i.e., the living beings which are the actors of this change are very likely to get extinct, or at least to become a marginal part of the biosphere of the planet.

1.3 Planetary Environments

The idea that the planets of the solar system - and also what now we call extrasolar planets, as soon as it was realized that the stars are other suns and likely they have planets - host forms of life is very old, dating back to Greek natural philosophy. Most seventeenth century scientists were of this opinion, even if Galileo Galilei warned that if extraterrestrial bodies are inhabited, the beings living there must be not only different from those we meet on Earth, but even different from what our wildest imagination can predict [1.7], [1.9].

Following this line of thought it was a common opinion that the environments we could find, once we will be able to reach the planets, would be more or less comfortable, but at any rate would allow us to live there.

In the solar system the two closest planets, Mars and Venus, were thought to be habitable. Mars was assumed to be a cold desert, owing to the fact that it is more far from the Sun than Earth, while Venus was thought to be covered by hot and wet jungles, with huge insects, owing to its proximity to the Sun.

In the second half of the 19th century three great astronomers - the...