1. Introduction

In his short story entitled Genesis (Genèse), Francis Carsac, a geologist from the University of Bordeaux (France), has created a tale around the ancient concept of panspermia, or the possible propagation of life throughout space. This idea can be traced back to Anaxagorus in the 5th century B.C. (O’Leary, 2008), and has been evoked over the ages by Benoît de Maillet in 18th century, by Lord Kelvin and Hermann von Helmholtz in the 19th century, and by Svante Arrhenius (1908/2009), Francis Crick and Leslie Orgel (Crick and Orgel, 1973), and Sir Fred Hoyle and Chandra Wickramasinghe, (2000), in the 20th century, and yet again in the 21st century by Rhawn Joseph and Rudolf Schild (Joseph and Schild, 2010a,b) who have devloped elaborate genetic and astrobiological mechanisms which they believe explain the origin and evolution of life and its dispersal throughout the cosmos (Joseph 2000, 2009a,b).

Carsac has written his tale with flair, without claiming to offer a full explanation of the origin of life on Earth, or even of life in general. He simply asserts as a prior condition the existence of organic compounds in the seas of our planet, essential to the emergence of the first living organisms. Where did these “building blocks” come from? Earth or space? Were they the result of natural processes or the design of some intelligence? Carsac chooses not to answer a question which does not belong to the realm of science fiction, a question belonging partly to science and partly to philosophy.

What makes Carsac’s story original is that he considers possibilities which are usually not addressed by science, with perhaps the notable exception of Crick and Orgel (1973) who envisioned the purposeful seeding of life on Earth, i.e. "Directed Panspermia." In Carsac's tale, the first life forms did not appear on Earth after a random intergalactic or interplanetary voyage aboard a meteorite (as asserted by the lithopanspermia and ballistic panspermia hypotheses); nor were they purposefully sent or deposited by an advanced extraterrestrial civilisation (directed panspermia); rather, they were born from microbes dwelling in the spit of a space traveller. As disturbing, vulgar or even sacrilegious as this idea may seem, its primary and principal interest here is to remind us that in spite of all the research which has provided a scientific basis for panspermia, there is, as of yet, nothing to disprove the scenario imagined by Carsac, nor to make the hypothesis a scientific certainty. If we can imagine that we have descended from extraterrestrial beings, or as others before us believed they were born from the thigh of Jupiter, we should also accept less glorious hypotheses of much more modest, even highly improbable, ancestors.

2. Cosmic Origin and Beyond

Thanks to current research in the field of astrobiology which has demonstrated that bacteria can survive ejection from the surface of a planet, a journey through space, and a crash landing onto the surface of a planet (Burchell et al. 2004; Horneck et al. 1994, 1995), and current research in genetics which indicates life on Earth has a genetic ancestry of at least ten billion years (Joseph and Schild 2010a,b), and couple that with the complete improbability that life could have been fashion on Earth (Joseph and Schild 2010a), panspermia must be taken seriously and take its rightful place in the world of ideas. However, panspermia also has important implications for the evolution of life on Earth (Joseph 2000, 2009b,c) and offers a third alternative to “Creationism versus Darwinism” (Klyce & Wickramasinghe, 2003).

Brig Klyce and Chandra Wickramasinghe (Klyce & Wickramasinghe, 2003) are of the view that the question of the origin of life, and the concept of a beginning, are best addressed by panspermia. It is not my purpose to scientifically evaluate the reach and the relevance of their proposal; I only want to underline how this hypothesis helps reveal the limits of the other two alternatives (creationism vs abiogenesis) when human conscience, intelligence and reason seek an answer to the question of the origin of life. One of these limits has been acknowledged and repeated again and again by naturalists, including one of the greatest, Charles Darwin. In Darwin's autobiography, the English naturalist wrote: “The mystery of the beginning of all things is insoluble to us; and I for one must be content to remain an Agnostic.” In asserting the panspermic hypothesis as an explanation for how life emerged on Earth, Klyce and Wickramasinghe take Darwin’s observation into account and implicitly acknowledge that in the question of life on Earth, there is a wall of unknowing, like Planck’s Wall which prevents access to the initial time of the “Big Bang”.

To keep this incomprehension from feeding more radical ideological stances or dogmatic solutions (Arnould, 2009), and to avoid carelessly mixing biological research into philosophical and theological debates, and to confine it to the accessible earthly domain until we have obtained real scientific data from space, Klyce and Wickramasinghe (2003) propose the scientifically-admissible hypothesis of a cosmic ancestor and a process of dissemination or dispersal of life throughout interplanetary, intersidereal and intergalactic space (see also Gibson and Wickramasinghe 2010; Joseph and Schild 2010b; Napier and Wickramasinghe 2010; Wickramasinghe et al., 2010).

Life is a phenomenon and reality which is complex enough to withstand this type of treatment, i.e. the extremely limited scope which the human scientific mind can comprehend and the belief in "endings and beginning." Consider that Darwin called magnum opus The Origin of Species (1859), and given his agnostic position regarding the “beginning”, it is important to point out that he did not in fact cover the origin but rather the transformation of the species. The term “origin” does not mean exactly the same thing as the term “beginning”. “Origin” designates not just the appearance of a reality or being, or the start of a process or action; it also designates that which supports the being in its existence, that in which it consists in its particular manner of being a part of both spatial and temporal reality, that which gives it its stability and movement. Understood in this way, the term “origin” can refer to the processes Darwin described which led to the transformation of the species, from an inaccessible first living organism, and then from the closest common ancestor. Darwin wrote of this ancestor which biologists today refer to as LUCA, the Last Universal Common Ancestor. No one can fail to see the complexity of these processes, and biologists are still trying to gather pieces to a puzzle which is certainly as boundless as our universe, hidden deep in both space and time.

To a certain extent, panspermia acknowledges this way of looking at the essential character of life, that which Pierre Larousse, the “inventor” of the most famous French dictionary, made the motto of his work: “I sow to all winds” (“Je sème à tous vents”). Life, too, sows to all winds, including cosmic winds, so argue the believers in panspermia.

There is now evidence suggestive of past life on Mars (Levin 2010; McKay et al., 1996). Microbes known as extremophiles have been discovered living in every conceivable environment no matter how hostile to life. And when exposed to hostile conditions never before experienced on this planet, including poisons, pharmaceutical and antibiotics, life immediately adapts, which is why microbes can even survive space vacuum conditions and cosmic radiation (Joseph 2009b; Joseph and Schild, 2010b). Life and living organisms, are like a vast ocean whose sources are too far off and which may remain forever unknown to us. Life can be like a river which sometimes flows calmly but more often rushes wildly, which is why it can suddenly evolve into myriad forms.

In speaking of life and its evolution, the English biologist Richard Dawkins also employed the image of the river; a river in the midst of which all living beings, including ourselves, were mere machines created by our genes to reproduce and ensure their own propagation. For Dawkins, there is no doubt: the predominant quality to be expected of a gene is merciless selfishness (Dawkins, 1976, 1995). It is certain that Dawkins enjoyed provoking those who would advocate conservation, restraint and altruism over dissemination, excess and selfishness. In any case, he held that nature is not necessarily in accordance with human culture, morals or values. As stated in his book The Selfish Gene: “If you wish, as I do, to build a society in which individuals cooperate generously and unselfishly towards a common good, you can expect little help from biological nature.”

As debatable as Dawkins' position may be, and it has been incessantly debated, I think it is relevant in any attempt to seriously consider the question of panspermia in order to analysis it.

3. Cosmic Future

Over the last 100 years, the theory of panspermia has evolved from implausible hypothesis to a recognition of the need for "planetary protection" policies should soil samples be brought to Earth from other planets, or to prevent the contamination of other celestial bodies via launchers, satellites or exploration probes (Alby et al., 2007). The possibility of contamination was taken seriously enough to convince a French popular science magazine to run an issue with a cover headline reading “Life on Mars!”, followed by the subtitle: “Brought by Man.” In fact, the experts willingly distinguish sensu stricto contamination (i.e. depositing structures, entities or beings in places which are foreign to them) from proliferation (the reproduction and dissemination of these forms).

Joseph (2000, 2009a,b; Joseph and Schild 2010a,b) has argued that only one microbe needs to survive a journey through space and once on a habitable world orbiting in the habitable zone, could cover the planet with bacterial offspring. However, while it is possible that exploratory missions may have contaminated Mars Earthly organisms, it is unknown if these organisms would be able to reproduce and proliferate in the conditions on Mars. But who can be sure that the conditions on a celestial body which may now be unfavourable to the proliferation of earthly organisms will not become favourable in the future? Joseph (2009b) argues that that microbes can genetically engineer the environment and biologically terraform a planet, creating a biosphere conducive to the evolution of increasingly complex life forms. As proof, he offers us Earth and what has taken place over the last 4.5 billion years.

In any event, with regard to these future risks, the scientific community and all space agencies believe it is necessary to take the greatest possible precaution in order to avoid contaminating Earth or the celestial bodies being explored. Indeed, COSPAR (Committee on Space Research) was mandated by the United Nations to establish appropriate recommendations: “Although the existence of life elsewhere in the solar system may be unlikely, the conduct of scientific investigations of possible extraterrestrial life forms, precursors, and remnants must not be jeopardized. In addition, the Earth must be protected from the potential hazard posed by extraterrestrial matter carried by a spacecraft returning from another planet. Therefore, for certain space mission/target planet combinations, controls on contamination shall be imposed, in accordance with issuances implementing this policy” (COSPAR, 2005).

Not only it is now recognized that life may be brought from other planets to our world, but the inherent dangers of contamination are also understood. Microbes from other worlds might kill us. Could the panspermic process one day become a deliberate human act, providing a whole new form of space conquest (Mautner, 2010)? My aim here is not to give too definite an answer to this question, nor even to provide the scientific and technical information needed to arrive at such an answer; I will merely attempt to discuss the philosophical and ethical implications of contaminating other worlds with life.

It is certain that in order for the idea of active or deliberate panspermia to be analysed, critiqued and debated, we must first define the concept of nature and humankind which serves as its ideological basis. Moreover, this concept cannot be merely theoretical; it must necessarily be practical. For example, if humans in the past could have an anthropocentric view which was entirely theoretical (even on the scales of time and space they had at the time), our anthropocentrism must now be practical. We humans must assume real responsibility not just for Earth and its ecosystems, but for other planets which we might contaminate with life, thus destroying whatever life may already dwell on these other worlds. Today we have the means to willingly disseminate life forms elsewhere than on Earth; there is nothing to stop us from contaminating other worlds, perhaps to terraform them to make them fit someday for colonization, or to destroy potential competitors already dwelling on these planets. But do we have the right?

Similar questions have been raised in the debates surrounding genetic engineering: to what extent do genetic techniques surpass what natural processes could accomplish, even over long time periods? Is it possible to take genes beyond the limits of evolution, to design hybrids that cannot be obtained by natural processes? In other words, does humanity have the right? Can we take the risk of diverging from the possibilities offered by nature to enter the realm of what is, in the strictest sense, artificial? Deliberate, directed panspermia raises similar questions: should we cast earthly organisms outside our planet? What if, in so doing we destroy extraterrestrial life forms or intelligent beings? How far can we overstep the boundaries in interplanetary, interstellar and intergalactic space? In debating these issues and considering these questions, there often emerges a recurring notion which is shared by many cultures – that of the sacred; life is endowed with a sacred quality. Should this "sacred" quality slow or stop all our attempts to control, modify or manipulate life, or to use it for cosmic development? These questions strike me as judicious, but are also associated with the notion of transgression as presented by the French philosopher Roger Caillois (Caillois, 1939); in this sense, the human being is prompted and encouraged to become fully aware of the act he commits, so as to choose not to act.

Discussing the possibility of directed panspermia does not necessarily mean blindly obeying genes as selfish replicators, but rather perhaps, taking part in a trend which is followed by life in general. Following in the steps of Carl Sagan and Francis Crick, Michael Meot-Ner and Gregory Matloff defend this type of undertaking as a possible means of facilitating the conquest of new habitats using earthly life forms (Meot-Ner & Matloff, 1979; Mautner, 2010). In their view, it is essential to consider the risks involved in potential encounters with other life forms, but these risks have to be looked at in terms of the level of development: they argue that while primitive life forms would perhaps face extinction, those more evolved would certainly be able to survive the dissemination, or intrusion, of earthly life forms. However, is this true? Might it be exactly the reverse? Moreover, the two researchers argue that the use of panspermia would allow us to create, in essence, a “Noah’s Ark” designed to ensure the survival of species threatened by drastic changes in the earthly ecosystem, or even foreseeable changes in the solar system such as the eventual death of our sun.

However, for as much, if we want to take the place of Noah, we have to remember that the principal threats for terrestrial living species are coming from human activities. Before being cosmic and panspermic, human responsibility and ethics have to be terrestrial!

4. Conclusion

What began as a hypothetical idea, panspermia, now provides a unique perspective in how we consider life. Setting aside the question of how life began, the concept of panspermia provides us with a framework to achieve a clearer understanding of the mechanisms aimed today at managing the emergence, extinction, preservation and transformation of the many living beings that inhabit our Earth. The mechanisms of panspermia are just beginning to be understood (Joseph and Schild 2010b; Napier and Wickramasinghe 2010). Panspermia and the development of astronautic techniques for visiting other worlds, support the idea that humanity could, on its own, proceed to disperse organic and living elements to other planets and even other solar systems. Is this reasonable, desirable, sustainable? For the time being, many scientists oppose the idea of contamination, wanting to avoid jeopardizing attempts to find and study extraterrestrial life forms; I share their opinion. This is a wise decision, and one that shows, as did Dawkins, that the human being is not driven solely by the “selfish” motivations of its genes; it is also and above all a cultural being. The fact there can be an ongoing debate on the possibility of directed panspermia at least goes to show that, while strictly speaking there is no exploration gene, the humans instilled with the love of knowledge, a thirst for exploration and a propensity for conquest, are beings who are responsible for their choices and acts.