Are We a Unique Species on a Unique Planet?

There are billions of planets orbiting billions of stars in our Galaxy, and there are countless of other galaxies in the universe. However, this does not necessarily say anything about how abundant life may be. We just simply don’t know – yet. And the deeper one digs into the question, the more superficial it seems to argue, as has been done for millennia, that  because “there are billions of stars orbited by planets in our Galaxy (and beyond), then there must also be countless of planets where life will have arisen and eventually developed into some kind of intelligent beings”. In order to find “the scientific answer”, we need to identify the processes that are important for the elements to organize themselves into a living organism, what is required for it to happen, and eventually what it actually means “to be alive”. These are questions the various speakers in this unique conference addressed from each their background, to eventually bring us closer to the difficult question “are we a unique species on a unique planet?” – the answer is far from obvious.

Why this conference and why now?

The idea of making such a conference has been a dream for me during many years. When I started at the university one of my main interests in astronomy was the question “is there life out there? What is life and what does it require to exist?”, but my university teachers found it just a branch of science fiction and concluded that “speculations about UFOs does not belong to Universities”. When I started lecturing during the early 1990s I therefore had to “keep it secret” that I taught astrobiology, and called the course I introduced for “the formation of the elements” which true enough, in my view, is part of astrobiology – how did it all originate -- but the rest of the story: “how did these elements managed to organize themselves into intelligent lifeforms” was in my view a fascinating and important part of astrobiology too. Now, many years later, I realize that this way of “sneaking” astrobiology into the university curriculum was the same for many of my colleagues throughout the world, and the students were equally fascinated with the subject as I was. Today astrobiology has become one of the most rapidly growing areas of astronomy -- time has matured for it.

Why ask if we are Unique? –Copernicus and the anthropic principle taught us that we live at a random place and time in the universe, with no special role for just us -maybe.

Lots of the reason that astrobiology became an accepted field was the discovery of more and more exoplanets, but they were surprisingly different from the planets in our own solar system. In the beginning this was mainly thought to be an observational bias, but the more the observations develop and we don’t find anything just remotely similar to “ourselves” the more the question presses on: “Is our solar system and the Earth unique in any aspects, and could it have influenced why we are exactly here?” – it would be a strong break with the anthropic principle that we use to believe in. Are we now on our way away from this “cosmic modesty”, demanding a more central place for ourselves, maybe even starting to believe that “the Universe deserves” that we spread our existence to other planets and beyond to larger parts of the cosmos? It is this wide ranging perspective I have tried to address in the conference –“are we and our solar system unique in any cosmic sense? –and if so, then why and in which way?”

Proceedings of the conference: full length videos and an overview text.

I am extremely happy and thankful that a great number of the absolute world-leading scientists in complementary fields associated to this question said yes to come. As the preparation for the conference moved forward and the program became more and more exciting, I decided that we had to film the talks, such that a much larger audience can get the opportunity to see and hear them too. The subject has a broad appeal in the public, but this does not necessarily mean that an understanding of the various aspects that goes into this interdisciplinary question are easy. I have therefore in the following tried my best to give a slightly more popular overview about what the main points of the various talks are and how they connect to one another. I myself may of course have misunderstood some of the points, in particular in the fields complementary to my own background. Instead of letting (and loading) the speakers with reading the text before to upload it here, I decided to upload it as it is. After all the full-length talks are here too, so I don’t risk to claim somebody has said exactly what I write, only to potentially expose my own ignorance. The text below, with the associated videos, is therefore to be understood as a somewhat unusual “proceedings” of the conference, that I hope can be an inspiration for other future conferences too. I hope it will be interactive in the sense that the speakers, as well as other experts, will improve my understanding of the field by correcting me where I may have misunderstood what was said or meant. I have added a little bit of background here and there too, and hope that all in all the combined text and films will appeal to a broader audience, and maybe will enlighten all of us about sides of this complex interdisciplinarity, which surely is part of the solution to the fascinating question “are we really unique – or are we after all  just an ordinary Galactic standard organisms among billions of similar others out there in the vastness of cosmos?”

Some statistical evidences for and against uniqueness.

A popular way of estimating how many technologically civilizations there may exist in the Galaxy we live in, is to quote the famous “Drake Equation”, but we have to remind ourselves how little was actually known when Frank Drake formulated his equation in the early 1960s. In particular one of the invited speakers, Helmut Lammer, addressed in detail how to modernize the equation, and the result seems quite depressing for those of us that want to believe that the universe is teaming with life – too many of the factors we now know of as needed for life to arise and develop to something we can communicate with, are quite small. The accumulated conclusion points toward that we after all are quite alone, at least among civilizations that can potentially speak to one another. Another speaker, Ian Crawford, in his talk together with Dirk Schulze-Makuch, pointed at that in Frank Drake’s most optimistic view all the factors in his equation are set close to 1 (except the civilization’s lifetime), i.e. that one new star is born per year today (and more in the beginning), all stars have on average one Earth-like planet in the habitable zone, and once the physical conditions are right for life to originate and develop it will do so, and sooner or later become a technologically advanced civilization. The only reason that we don’t see or hear them all the time would then be that technological civilizations have a relatively short lifetime. If it is 1000 years and one new star is born per year, there would be 1000 technological civilizations in our Galaxy, enough that we with an eager search sooner or later will find one or more of them. However, throughout the lifetime of the Galaxy, hundreds of billions of stars have lived through their life, and if they all gave rise to a technological civilization at some time of their life, hundreds of billions of technological civilizations have then existed during the history of the Galaxy. Even if only one single of these billions of technological civilizations had spread like we are at the brink of doing, they would already long time ago have been here (and everywhere else). The average age of stars in the Milky Way is estimated to be a bit more than 7 billion years, so average lifeforms on a habitable-zone exoplanet orbiting an average star would already now have had 3 billion years more to arise and develop a civilization of intelligent beings capable of colonizing the Galaxy. Why did not a single one of them develop like us, spreading into space? So, even in this optimistic view of the abundance of life, we are unique – somewhere in the process there is a stopping block to become like us, and we are unique by starting the Galactic colonization process.

Alfred R. Wallace himself, the co-inventor of the theory of evolution, thought the stopping block was on the state from the first cell to advanced lifeforms, and he estimated (in his book from 1904; long before the formulation of Drake’s equation) that the step from the first microbes to intelligent beings has a likelihood of only 1 over 10 to the power 14 to happen through evolution. Dirk Schulze-Makuch was somewhat disagreeing with this conclusion, pointing out that there are many different routes from primitive life to intelligent lifeforms, as exemplified by intelligent birds, cephalopods (octopuses), cetaceans (whales), and primates. Therefore, we have many different intelligent lifeforms just on Earth, and with a greater variety of habitable environments we should expect a greater variety in “the cosmic zoo” (as his new book is called). If this is true, it obviously leaves us the question about where the stopping block then is; after all neither Venus or Mars developed an intelligent civilization, in spite of originally having been habitable; is it the first origin of the first cell that has almost zero probability?

The origin and early development of life on Earth

Our knowledge about the first life on Earth was reviewed by Pascale Ehrenfreund together with a description of ongoing and coming space projects related to increased understanding of the pre-biological conditions during the early solar system. Some people think life on Earth could have arisen as early as 4.2 billion years ago, while the most accepted view today is that it arose somewhere between 3.5 and 3.7 billion years ago. What did it look like, and where did the building blocks for it arise? Our present knowledge about the kind of organic material that existed on Earth close to its birth resides in studies of comets and carbonaceous meteorites, the most pristine (i.e. “original”) material left over from the early solar system (and from interstellar chemistry, as explained in Paola Caselli’s talk described below). However, it gave rise to a lively debate when the question came up how far toward a living cell the organic material was that rained on Earth in its childhood, and I think the clear conclusion was that there are different opinions on this issue, as can be most clearly experienced in the video from the discussion session of day 3

What happened after the first life arose was addressed by several speakers, notably in the invited talks by David Catling and by Don Canfield and the contributing talk by Johan Andersen-Ranberg. They all addressed the central role of oxygen in the development of complex life forms, and how the oxygen production started with photosynthesis in cyanobacteria that arose in an oxygen-free atmosphere and later developed into several different forms, including those that sits inside our own body in the form of mitochondria.  During eons of time, the bacteria slowly (in fact surprisingly slowly) reduced the carbon abundance and increased the oxygen abundance in Earth’s atmosphere, to make oxygen respiration possible such as we know it today, and at the same time affecting the Earth’s climate markedly by reducing the abundances of the strong greenhouse gasses methane (CH4) and carbon-dioxide (CO2) on the cost of increasing the abundance of the optically transparent oxygen (O2) gas. These changes were not a smooth and continuous function, but rather they were stepwise, rapid and strong whenever they happened. With intervals there were even large swings up and down in the oxygen and methane abundances over timescales as short as thousands of years.

A relatively high oxygen abundance is necessary for multicellular organisms to arise. Its energy production per chemical reaction in the cell (in the form of number of ATP units produced) is many times greater than that of non-oxygen (anaerobic) related processes, therefore allowing a much larger cellular complexity of the involved species (and allowing for cholesterol in the cell wall, which makes it possible to grow the cell larger). Edward Schwietermann explained how the requirement for oxygen implies that the habitable zone where complex life can exist is substantially smaller than the general habitable zone (i.e. where water can be on liquid form), and hence reduces the number of planets substantially where it could be meaningful to look for advanced civilizations that we potentially can communicate with (Nikku Madhusudhan, on the other hand, argued for widening the habitable zone, as discussed below). Even though the computation of this “complex-life habitable zone” is difficult, the reason for it is simple: too little oxygen will prevent the existence of eukaryotic cells (i.e. large complex cells), and too much oxygen will destroy advanced life forms (for example, it will self-ignite wood, create unwanted chemical reactions in the biological cells, etc). Oxygen is also necessary for fire, and one could speculate whether the first steps from multicellular organisms to technological development can at all take place without energy to produce the first technological machinery, and whether this energy could come from anything other than fire. Similar constraints exist for the abundance of CO2 in the atmosphere that would allow for complex lifeforms and the existence of a technological civilization, so all in all the requirements on exoplanetary size and orbital radius becomes much more restricted than just the “standard habitable zone” that is defined as the right physical conditions for the existence of liquid water (i.e. “the possible existence of just any type of life”).

How to find extraterrestrial life, or even “just” the planets where it resides?

Realizing how difficult it is to understand how life arose and developed on our own Earth, and how many unsolved central questions are still open for debate, it may seem a hopeless task to try to understand how life arose and developed on other planets, but in fact the studies of life elsewhere may well be the only way to reach a deeper understanding of life on our own planet, and how life in general (including us) interacts with the surroundings. In order to proceed we need to travel to other bodies in our own solar system to study them in detail, build better instruments, construct larger telescopes that can see the surface of exoplanets, develop more advanced and realistic numerical modelling tools, etc. During the first talks of the conference the speakers addressed the question “how do we find the planets around other stars, and how do we estimate whether their conditions are such that life as we know it, or even life as we don’t know it, could thrive there – i.e. whether the planets are habitable, which is not to be confused with habitated which means whether someone actually lives there, which is a next step for the (near) future to answer.

Anne-Marie Lagrange opened the conference by giving an excellent overview of the methods in use for finding exoplanets, and in particular focused on the development of techniques and instruments that makes it possible to directly observe the exoplanets themselves. Until now, most observations have only drawn conclusions about the exoplanets from their effects on the stars they orbit. Lagrange had already predicted the existence, and calculated the orbit, of an exoplanet in the Beta Pictoris system some years before the first “official” exoplanet discovery in 1995, and later confirmed the predicted data by the first direct photos of an exoplanet, obtained by her group in 2005. Some years later enough photos had been accumulated to make a real “film” showing its full orbit around its star (which can be seen in the video of her talk). But substantial development of this technique is needed in order to routinely take direct images of exoplanets of the kind where we think life as we understand it can exist.

If the star is bright enough, it is possible to obtain an indirect spectrum of the planet, even when we can in fact only see the star. The most used technique for doing this, the so-called retrieval method, was developed by the second speaker, Nikku Madhusudhan. Here one takes a spectrum of the star when the planet is in front of the star (i.e. when it eclipses or transits the star), and again when the planet is away. Then one subtract the two spectra from one another. The difference is the amount of the star light that was absorbed in the rim of the planet’s atmosphere when it stood in front of the star. By experimenting with which molecules at which temperature and pressure could give the obtained spectrum, one can figure out what the planetary atmosphere must consist of. An obvious question would be “does any known Earth-like exoplanets show traces of gasses that could have been produced by biological activity at the planet?”. And here the first surprising result comes in: among the several thousands of exoplanets known today, at maximum a handful have size and temperature somewhat similar to Earth. There are no more than these among the known many where we can even in theory search for life as we know it, and they may even in praxis be too small for revealing their spectra with even our best telescopes. Madhusudhan’s first goal was therefore to try to expand the search to “life-as-we-don’t-know-it”, by including planets a bit out-of-the-box, and it opened up a whole new class of objects, now known as hycean worlds (hydrogen-rich-ocean-covered exoplanets), and the first spectra of them have shown the existence of CH4 and CO2 in their atmospheres, and maybe DMS molecules which on Earth are produced only by life. If life can exist on hycean exoplanets, it expands our concept of the habitable zone, bringing many more known exoplanets into it, and opens the central question of what we actually mean by ‘life’ -- which kind of beings could potentially exist on planets in such an expanded habitable zone, and are we ready to accept them as “life”?

Another invited speaker, Kate Adamala, went as far as to say that if we do find traces of life as we know it from Earth on another planet, then it is for sure contaminations from Earth, and we should ignore it. Life has, in her opinion, so many different ways of manifesting itself, that the likelihood that it, on another planet, should happen to function in the same way as on Earth is infinitely small. Her research is centered on studying the basic structure and functionality of artificial life-like cells that are not real life, but produced in the laboratory or in a computer simulation. The perspective of this exciting research is to bring new light on the basic principles behind living cells, and on top of this to be able to transmit for example custom made medicine via laser beams to remote areas of Earth, to spaceships and eventually to the first colonies on Mars and elsewhere. This sounds as futuristic and science-fiction like as it would probably had sounded to a horse-riding postman in the 17^th century claiming that one day we will send letters in the form of electrons at the speed of light, but Adamala think that the “new science fiction” is less than a decade from reality. Maybe one day we ourselves can be transported this way to remote exoplanets.

What determines the composition of exoplanetary atmospheres, and whether life can exist there?

It is certainly not only the planetary size and its place in the habitable zone (i.e. the amount of energy it receives from its star) that determines whether it is suitable for life to arise and evolve. Even the rocky interior of its solid composition has to be within a “habitable composition zone” of its own. In the invited talk by Lena Noack, she explained why planetary mass as well as its interior composition is completely essential for the possibility to form and atmosphere where life can exist on the planet’s surface. In a first approximation, the primordial atmosphere of most planets will have consisted of hydrogen and helium, but unless the planet is large (such as Jupiter and Saturn) this atmosphere will soon after escape to space. The secondary atmosphere, such as the one we have on Earth today, is a result of outgassing from the interior, biological activity, and collision with volatile objects (such as comets and carbonaceous chondrite meteorites). While we cannot predict the collisional and biological contribution to exoplanet atmospheres in general, Noack explained how the planetary mass and its formation distance from its host star influence what the mantel composition below the crust will be, and therefore which gasses can outgas to form the secondary atmosphere. The amount of outgassing depends, however, strongly on whether the crust is “mobile” (such as in the Earth’s continental drift case) or “immobile” (such as Mars’ thick crust; acting as a stagnant lid over the interior magma). Not only the kind of outgassing but also the amount influences the chemical composition of the final atmosphere. High mass atmospheres will in general be dry, and might even consist of pure H2, while secondary atmospheres of Earth-like pressure often will be wet and consist of CO2, methane and nitrogen, and in extreme cases even abiotic oxygen. In the contributing talk by Hayang Wang, he looked into what different host star compositions can tell us about the most likely interior composition of exoplanets formed at different distances from the star, taking into account also the known relation between refractories and volatiles in different known objects in our own solar system. For exoplanets where the orbit, mass and radius of the planet has been measured and the host star properties are known, one can then use Noack’s models to predict what the atmospheric composition aught to be, and hence, at least in principle, be able to isolate which of observed planets in the habitable zone are most likely to have an atmosphere where life as we know it can develop. This would also help us estimate whether potentially observed oxygen on an exoplanet is to be understood as a sign of biology or of volcanic outgassing from the mantel.

The effect of the interior stretches, however, beyond the amount and composition of the outgassing atmosphere. The relatively small differences between Mars, Earth and Venus’ interior compositions illustrate this clearly. Mars seems to once have had a substantial atmosphere with sufficient greenhouse gasses to make it habitable at the time when the first life originated on Earth. Both Mars and Earth had a zone of molten core that created a magnetic field that prevented the solar wind from eroding the atmosphere away. Mars, however, was too little to keep its core molten, so it soon lost its magnetic field and hence most of its atmosphere too, and the surface then became boon dry and extremely cold compared to its original state. Felix Arens studied how microorganisms on Earth have adopted to the extremely dry conditions of the Atacama desert, and Miguel Salinas-Garcia measured the metabolic activity of microorganisms collected in the cold and dry environments (“the arctic desert”) of North-Eastern Greenland and identified the gaseous waste products of their metabolism, which could potentially be identified as biomarkers on the outer edge of the habitable zone (in exoplanets or on Mars).

In contrast to Mars, Venus was big enough for creating a lasting molten inner iron region, but its slow rotation prevented the formation of a magnetic dynamo. Instead, however, the outgassing became so substantial that a tremendous greenhouse effect drove its surface temperature beyond the limits for life, but high up in Venus’ cloud cover the conditions are quite Earth-like. On Earth microbes live “everywhere”, including the clouds where they transform the freezing point to such an extend that it, if well modelled, could serve as a clear biosignature on remote exoplanets. In his invited talk, Kai Finster reviewed the processes that allow microbes to live and drift with the clouds, adjust the cloud physics, and hereby have an important influence on the atmospheric structure of exoplanets, and on Earth’s climate and upper structure too. When the air is supersaturated with respect to ice but sub-saturated with respect to water, bacteria will control the ice-cloud formation at relatively high temperatures (above -15 deg.C) while mineral particles will control it only at temperatures colder than minus 15 deg. Could life once have originated in such high clouds on Venus? Or can life only originate in a small warm pond at the surface, as Darwin suggested, and from there mutate to inhabit further from its origin? During their contributing talks, Gergely Friss discussed computations of which atmospheric conditions must be fulfilled in order to form “small little ponds” on the surface of the planets, while Marrick Braam and Sven Kiefer discussed other aspects of the exoplanetary atmospheric modelling and Helena Lecoq-Molinos discussed the microphysics of non-biological cloud formation processes.

The solar system is unusual compared to other known (exo)planetary systems -- is it just a statistical deviation, or is it real and of importance for why we are here?

Our modern theories about how planetary systems form were reviewed in a longer talk by Michiel Lambrechts, while shorter talks by Peter Woitke, Inga Kamp, Pooneh Nazari and Helene Rousseau, revealed what the most recent observations of the planet forming disks around other stars have shown us. We think, or at least thought, that we have a relatively good understanding of how our own solar system formed, but the more we study it, we realize that it could also have happened in several other ways, and potentially only few of the ways would allow life to arise. Before the first exoplanets were observed, it was the general belief that all planetary systems (if any) had formed in the same way as the Solar system itself: A big interstellar cloud would collapse, the star (“sun”) would form in its central region and the remaining gas and dust would “hang around” as a disk around the star for a long time while clumps of material collapsed and slowly collided to build up planet sized objects in each their separated regions of the disk. In the inner part close to the warm proto-star, only high temperature condensates, such as rocks and metal clumps, would exist in solid form, explaining why the Earth and the other terrestrial planets are rocky with an iron core. In the outer regions, ice would condense (just as when it snows on Earth) and because there were so much ice in the cold regions of the disk, a big proto-planetary core of ices would quickly form, and subsequent gas-collapses on top of the ice-cores would eventually have lead to the formation of Jupiter, Saturn, Uranus and Neptune.

In the present picture, as presented at the conference, planet formation is dominated by small cm-sized dust and ice pebbles which during their inward drift through the disk grows to large objects that ends up becoming the planets as we know them. The composition can therefore end in a larger and more complex variety of outcomes than in the old model that was based on our knowledge of the solar system only and our belief that the planets had formed where they are now. One of the surprising new results from recent observations was that parts of some disks are dominated by carbon-rich gasses rather than oxygen-rich molecules. Whether this has any practical importance for the planet formation is still unknown, but one can speculate whether planets condensing out of a carbon-rich cloud will be made of carbonates such as diamond and graphite. The rocks in our Earth are all based on oxygen (i.e. “silicates”). The bulk of the mass of our own body is also oxygen rich (in the form of water), but the active life ingredients such as the cell wall, the proteins, and the DNA and RNA molecules are all based on carbon. What kind of influence, if any, the disk chemistry could have on the formation of life on the planets that form in disks of various chemical compositions is still only speculation, but the basis for a realistic understanding is laid right now through new observations and improved theory, and it all indicates that a large variety of possible formation scenarios exist.

In the invited talk by Paola Caselli, she took us on a tour through how the atoms and simplest molecules in the cold interstellar space builds more complexity by reactions on the cold grain surfaces. There hydrogen atoms will stick to the grain to form H2 (that most often leave the grains again and creates the interstellar H2 gas), reacting further via H3+ to the very reactive OH molecule, water and other molecules and ions. Through simple movements around on the grain surface, but also often though so-called quantum tunneling, the molecules will build up to form many different complex organics, including all the nuclear bases in RNA and DNA as we later on will find them in primitive meteorites. When water molecules stick to the grain surface they will build up layers of ice. CO can build ices too, that can be as cold as 6 Kelvin. When the cold interstellar grains become part of the warmer collapsing protoplanetary disks the ices will sublimate, and together with the organics, CH4, NH3 and other molecules form a mixture of collapsing gas and dust on their way to become planets – and perhaps the building blocks for the first life.  In his contributing talk, Jan Hendrik Bredehoft underlined the importance of radiation and ionization in all these reactions, and stressed that the basic principles that drives the molecules toward higher complexity, and to eventually becoming living cells, are universal. So, we are back at the same question: “does the process that leads to the first primitive life always happen once the physical conditions are right, and was Wallace right when he more than hundred years ago claimed that the stopping block in abundance of technological civilization isn’t the formation of the first bacteria, but rather the impossibility of evolving the first cells to complex life?

Why are not all planetary systems identical to one another?

The interstellar medium is relatively homogeneous, all collapsing clouds follow the same physical laws, and the chemistry is bound to basic reaction rates that are explained by the laws of quantum mechanics. Yet, the final outcome is widely different from system to system. Very few systems have the relatively high number of giant planets that our planetary system has, some people find it unusual that we are lacking the common sub-Neptune exoplanets that are found in large abundance elsewhere (although ‘Planet-9’ in our solar system may also be such one), and some indications point at that we have unusually many planets in our system. The solar system seems to have formed relatively calm and quietly, leading to a high stability, while some of the exoplanetary systems seem to indicate a more violent formation history, where planets have been thrown into highly elliptical orbits, or even into their host star or all the way back into the interstellar space. Some people think that the latter scenario is even the most common, and there is an upcoming branch of exoplanet research aiming at determining the abundance of expelled free-floating exoplanets, perturbed out of the system where they formed. Already Newton noticed that our solar system has a very high degree of stability, although he found that it is slightly unstable, and concluded that in order to make it likely that we are here, God probably intervenes now and then with long intervals whenever the planetary system needs to be re-balanced. One could wonder if Newton, if he had known about the many exoplanets we now know of, had concluded that God forgot many of the other systems, or just intentionally made our system particularly stable in order for us to be here.

Fifteen years ago, a small group of scientists that included one of the invited speakers, Bengt Gustafsson, noticed that details of the solar abundance is systematically different from the average of sun-like stars (i.e. stars with almost the same mass, radius, age, and bulk chemical composition as the Sun). The discovery has led to a wide discussion, and so far more than 300 papers in the scientific literature tries to explain the difference. The Sun is underabundant (compared to the average of other ‘Sun-like’ stars) in the elements that formed the rocky planets in our solar system, including the Earth, and simple calculations reveal that if one collided Earth, Mars, Venus and Mercury into the present-day Sun, the planets would evaporate and change the solar spectrum to become similar to the rest of the sun-like stars. Does that mean that we were “just lucky” that the Sun didn’t engulf the Earth? Gustafsson didn’t find this the most likely explanation of the observed differences, but abstained from pointing at one specific theory among the many to be a clear winner.  Åke Nordlund presented his own ideas about what caused the differences, and explains them as the Sun being just one random outcome of many statistically possible, supporting the anthropic view that we are at a random place at a random time among all the possible ones. Hans Rickmann explained how the precise evolution of a planetary system depends on the environment of nearby stars in the stellar cluster that the system forms in, and noticed that some outcome of his simulations of our solar system’s birth place made the Earth form boon dry, and hence deprived from life as we know it, while some came out with water on its surface as we know it on Earth. Hans Zinneker focused on the fact that no other planets we know of are orbited by such a large moon (relative to the planet) as we are, and discussed theories for how the existence of the Moon affects the Earth’s tides, magnetic field, and the continental drift, issues that all may have been important for the origin and development of life on Earth, and may even in itself have contributed to the increase of the abundance of oxygen in the Earth’s atmosphere.

Where does the human civilization stand in a cosmic perspective?

Life on other planets than Earth, and in particular complex and technologically intelligent life, may be very rare, and potentially even non-existing, but if we believe that we are not unique, and other species like us exist out there in the Galaxy, then Earth will one day get visitors. The encounter with an alien technologically advanced civilization is likely to be the most transformative event in human history, in particular if they suddenly arrive, just like we one day in the relatively near future will start building cities on Mars, and in the further future will do the same on Earth-like exoplanets orbiting other stars. Are we prepared for it?

What rights, responsibilities and possibilities does it impose on us if it turns out that we are truly unique? Do we have a moral responsibility to spread intelligence throughout the Galaxy? Will it affect the way we feel obliged to behave toward one another? – and visa versa, what will we do different if we suddenly find that our cosmic surrounding is teaming with highly intelligent life forms we have not yet noticed? The talks during the last day of the conference were all centered around aspects of it, and presented enlightening input to the debate.

The first invited speaker of the last day, Steven Dick, has a background in both astronomy, astrobiology and history of science, and discussed which consequences we could expect from discovery of extraterrestrial life. The suspicion in 1996 that the Mars meteorite ALH84001 showed traces of extinct Mars microbes steered huge political and economic attention. The US President insisted to be the one to announce the discovery to the world, and the World Economic Forum later had a dedicated session. The effect would no doubt have been multifold larger if we had found intelligent aliens or, as Dick argues for as a realistic possibility, that we one day realize that we live in a universe where we may be unique as a biological intelligent civilization, but which is teaming with super-intelligent AI civilizations that are not easy for us to notice the existence of – the post-biological universe. Dick raised the question about which effect it could have on religion, culture and self-esteem if we figure out that humanity is just one among many equally (or even superior) intelligent species; should we suggest to baptize intelligent ETs? Would they want it? Are they altruistic, and what does it mean to be human are some of the many cultural questions a contact would rise, with large impact on our view of ourselves, on our philosophy, theology, our ethical behavior, and on science, including not just potential new discoveries and game changing inventions, but also such fundamental questions as how universal our perspective on science is; is mathematics discovered and universal or is it invented? The impact all depends on which kind of life we may encounter and in which way, but Dick’s thoughts go so fundamentally beyond a traditional science-fiction imagination.

We would also need to consider how we, as scientists, would like to explain such a discovery to the global political authorities and to the public, and Katien Kolenberg presented a full talk about the communication and interaction between science, public, media, technology, and art, so-called STEAM. The speaker that probably addressed most directly the question of how we communicate and prepare ourselves for an encounter with super-intelligent species was Ian Crawford. Although he had already argued in his talk together with Dirk Schulze-Makuch that it seems unlikely that there are any other intelligent (biological) civilizations in the Galaxy, we may be wrong, and the impact on our existence would potentially be so huge that we need to pro-actively to a potential encounter form international bodies with the necessary power to make binding treaties about how to react in the name of humanity, in order to change a potential encounter from a disaster for humanity to a stepping stone forward. If the astrobiology community was able to establish such an organization on this quite non-political subject, we may help inspiring the world proceed toward establishment of other similar bodies addressing global challenges of more political character, to the benefit of humanity’s common future and co-existence. The discussion of aliens could hence benefit everybody, even should aliens turn out not to exist.

The final speaker of the conference, Robert Zubrin, agreed with the point of view that the interaction with other worlds would have enormous impact on our civilization, but from a different point of view, addressing the tremendous benefits our civilization would encounter from starting colonization of otherwise un-inhabited worlds, beginning with colonization and terraforming of Mars. Zubrin saw an enormous acceleration in the extraterrestrial colonization once, in a few years, re-usable large rockets become for sale on the open marked, just as used cars are sold routinely between people today. Colonies on Mars would flourish and the colonies that offered the best conditions for the inhabitants will attract most people and survive as “the fittest”, as an inspiration for how to structure our nations and societies on Earth as well. To the common question of “what shall they live from on barren and in-hospitable Mars?”, Zubrin had a well thought out and clear answer, “resources is nothing that exist per se, it is something we create”.

Uffe Gråe Jørgensen,

Head of Centre for ExoLife Sciences, and main organizer of the Conference, Niels Bohr Institute, October 2024.

----with humble thankfulness to all those that made this conference possible: the speakers, the participants, the friends and colleagues that invested a huge effort to help, eminently Morten Bo Madsen, Helena Baungaard-Sørensen, Anders Prieme, Nanna Bach-Møller, Anja Andersen, and Zofia Kohring. The conference was generously supported by The Centre for ExoLife Sciences at the Niels Bohr Institute, the Novo Nordisk Foundation, the Carlsberg Foundation, the Marie Curie Double degree network CHAMELEON, and the Niels Bohr Institute Foundation. The videos were produced by Mathias Mouridsen, and the animation artworks in the end of each video were made by Francisco Antonio Escobar-Orellana (3DDA).