Invited Talks

Jacques Arnould, French Space Agency (CNES), France “The challenging implications for theology and ethics”

Until now, there has been no evidence of the existence of life forms other than on Earth; the philosophical, ethical and theological corpus that has been built up on this subject over several millennia is therefore based on a thought experiment or a posture of belief. Between dealing with a heresy and applying the precautionary principle, extraterrestrials represent a special opportunity to question the boundaries of our systems of thought, and sometimes to shake up dogmatism.

Stephen Baxter, Science Fiction Writer, UK “Anticipating the Alien: Creating visionary science fiction”

At its best, the imaginative literary genre known as science fiction can help us visualise future developments, anticipate their impact, and perhaps guide our response. This kind of visualisation has been essential in terms of the SETI project, for it had to be possible to imagine the extraterrestrial alien before the enterprise of searching for it could be envisaged. But how can such visualisations be constructed?

This paper is a discussion of a famous example of this process: how, in the last years of the nineteenth century, and in the context of the scientific knowledge of that era, HG Wells imaginatively created our modern vision of the alien, and indeed anticipated the devastating wars of the twentieth century.

Steve Croft, University of California at Berkeley, USA “The future of SETI”

The modern era of observational SETI began over six decades ago at the Green Bank Observatory, with a survey of two stars using a single-channel receiver. Present day state-of-the-art radio SETI programs have deployed billion-channel receivers to the world’s most powerful telescopes, and are surveying millions of targets, generating petabytes of data in the process. SETI has entered the era of big data, and the continuing growth of telescope capabilities and computing power means that data volumes, and the associated region of parameter space that can be probed, will continue to grow in future.

Observational SETI is also expanding across the frequency spectrum. Time domain optical surveys, including the upcoming Legacy Survey of Space and Time (LSST), will provide a synoptic view of the sky that has the potential to find anomalous Solar System objects, unusual stellar variability, and many more weird and wonderful objects. Meanwhile, spectroscopic surveys could detect signs of laser communication or propulsion, or even the modification of exoplanet atmospheres from industrial activity.These rich datasets represent our best chance yet to find a bona fide technosignature, but also entail daunting challenges. Finding the needle of a convincing candidate in the haystack of interference from our own technology, and distinguishing artificial signals from astrophysical outliers, requires us to develop new analysis techniques. Artificial intelligence is playing a growing role in this effort, and may well be the key to discovery of life beyond Earth.New results, new instruments, new techniques, and new investment mean that the future of SETI is bright, and our chances of answering humanity’s most profound question have never been better.

Kathryn Denning, York University, Canada “The Problem/s of Preparation: On ambiguity, proliferating possibilities, Eureka’s shadows, and unspectacular pragmatism”

Decades of anticipation concerning the discovery of extraterrestrial life have generated periodic flurries of concern, multiple meetings, myriad predictions and recommendations, but minimal visible sustained action… and noteworthy diffusion of responsibility.  Where should we focus now in terms of preparation, faced as we are with an increasingly impressive range of potential discovery types with diverse ethical and practical implications, the varying timelines and epistemic forms of those discovery types, a space environment with ever-more players, and a media/communications landscape of unprecedented complexity and speed? Several foci are obvious: (1) Previous examples of putative ETL discoveries hold valuable lessons, as do the challenging experiences of scientists involved in other high-profile science in recent years. (2) Existing policy and protocols concerning extraterrestrial life are presently underspecified or insufficient. Change and development is possible, but not simple. (3) Social research is an essential but remarkably underutilized tool for understanding the concerns, beliefs, wishes, and communication habits of Earth’s publics and stakeholders in relation to extraterrestrial life and its environments. (4) Most importantly, I advocate pragmatic and perpetual attention to some essential basics: safety for scientists and science communicators, and the creation and maintenance of resource hubs robust and resilient enough to act as vital conduits of accurate information (or the best of our evolving knowledge) to enormous audiences, when potential discoveries occur.

Nadia Drake, California, USA “The media: friend or foe? Exploring the cosmic narrative, from a science journalist’s perspective”

We are now in an age where we have the tools to answer one of humankind’s most profound unanswered questions — are we alone in the universe, or is the cosmic ocean as richly populated  as Earth’s seas? As our search for life in the cosmos intensifies, we need to think about the complexities associated with communicating and reporting potential discoveries; in that realm, science journalists are a crucial conduit between primary science and public understanding. This talk will offer a behind-the-scenes look at how journalists choose and craft stories, and how (at least in an ideal world) we’d approach a topic as large and as fraught with uncertainty as looking for life beyond Earth.

John Elliott, University of St. Andrews, UK “Preparing for the discovery of extra-terrestrial life – The SETI Post Detection Hub”

Advances in technology have enabled us to realise that whenever we see a pinpoint of light in the night sky, regardless of which one we choose, there is a good chance that there is a planet nearby. This knowledge now significantly supports the likelihood that we are not alone in our galaxy, and more clarity to estimations for fp[i] and ne[ii] of the Drake equation. Will we ever discover life on these other Worlds? Will we ever receive a message from E.T? We do not know. We also do not know when this could happen. However, we do know that we cannot afford to be ill prepared – scientifically, socially, and politically rudderless – for an event that will have such a profound effect on us and one that we cannot afford to mismanage.

To meet this challenge, the SETI Post-Detection Hub was launched at the University of St Andrews in November 2022, providing a long overdue permanent ‘home’ for coordinating the development of a fully comprehensive operational framework. The Hub brings together a mix of long-established SETI expertise and new voices from the wider academic communities, to work on topics ranging from message decipherment and data analytics to the development of comprehensive post detection protocols, space law, and societal impact strategies. Science that also has much that can contribute to answering terrestrial questions, as well as reflecting on what makes us Human.

Exploring these new horizons – our known, unknowns and unknown, unknowns – challenges us to the limit (and beyond) of our current knowledge, perceptions, and technology, whilst endeavouring to avoid any limiting conceits:  a process that is and will be ever evolving. We look at aspects related to this challenge and preparations for such a discovery.

[i] fp = the fraction of those stars that have planets.

[ii] ne = the average number of planets that can potentially support life per star that has planets.

Jacob Haqq Misra, Blue Marble Space Institute of Science, USA “Escaping the Great Filter: The future of civilisation and the search for technosignatures”

Human civilisation continues to experience rapid growth in energy consumption, while projections of population stabilisation remain uncertain. A continued trajectory of exponential energy use would cause direct heating of the planet by ~2300 — also coinciding with our transition to a Kardashev type-I civilisation. If our patterns of energy consumption are typical for other technological civilisations, then the lack of evidence for extraterrestrial life suggests that we may be among the first. This implies that a “Great Filter” may exist in our near future, which would mark a critical juncture of whether we become a spacefaring civilisation or extinct. Any extant technological civilisations are likely those that have achieved long-term equilibrium with energy consumption and population growth. The search for technosignatures by ongoing ground- and space-based observatories will provide a way to test the Great Filter hypothesis and examine the extent to which energy-intensive civilisations occur in the galaxy.

Arwen Nicholson, University of Exeter, UK “How probable is Gaia?”

Life is deeply embedded in our planet, from the rocks and oceans to the atmosphere; it plays a pivotal role in the carbon cycle – Earth’s thermostat. A lifeless Earth would be a very different planet to the home we know today. This inseparable relationship between Earth and life is known as “Gaia”.  But how likely was Gaia to emerge in the first place? Under what scenarios can Gaian-planets emerge and what prevents so-called “anti-Gaian” dynamics – where life destroys rather than maintains habitable conditions on its planet. In this talk I will discuss the ways in which life has transformed our planet from an alien world we could not have survived into a planet capable of supporting life such as ourselves, how Gaia might emerge and persist, and what Gaia Theory implies for the search for alien life beyond our solar system. 

Giovanna Tinetti, University College London, UK “Exoplanet atmospheres in the era of JWST and ARIEL”

The search for exoplanets has often been driven by the goal to discover life in the Universe. We know today there are billions of worlds out there, and small planets are the most numerous… So there is hope! We have come a long way from the prejudice that only an Earth’s twin can host life: our galactic cousins appear more diverse, complex and interesting that we ever thought, and perhaps for this reason, many of the great exoplanetary discoveries have been obtained serendipitously and with modest facilities. 

While the role of flagship missions to advance the study of habitable worlds is unquestioned, alone they risk creating a scientific ecosystem based on a monoculture.  To foster a diverse, rich and sustainable approach, which will also enable the best use of the flagships, we are pursuing dedicated, moderate size missions that will provide a much needed scientific complement to the largest facilities. A keystone of this approach is the Ariel Space Telescope, to be launched in 2029 by ESA. Ariel is the first mission dedicated to the determination of the chemical composition of hundreds of exoplanets, enabling planetary science far beyond the boundaries of the Solar System. 
We are at the same time pursuing an innovative, commercial approach to the delivery of high-performance, small-size scientific satellites through the company Blue Skies Space Ltd, that will further contribute to a thriving, diverse and sustainable scientific ecosystem.

Stephen Webb, Science Writer, UK “The Great Silence reconsidered: Reexamining the Fermi Paradox in the age of discovery”

Almost three quarters of a century after Enrico Fermi posed the question “Where is Everybody?”,  convincing evidence for the existence of extraterrestrial intelligence remains absent. Absence of evidence does not imply evidence of absence, of course, but might the continuing silence be telling us something profound about our place in the cosmos? Following a brief review of the Fermi paradox, and of some of the solutions that have been proposed in recent years, we consider Dick’s “Intelligence Principle” in the context of the paradox and explore what this might mean for the future of humanity.

Frances Westall, CNRS-Center for Molecular Biophysics, France “Life out there, expectations and reality”

Either life is relatively common in the Universe, or it is rare, depending upon how readily life can be created from the simple ingredients available in the Universe (Bains + Schulze-Makuch, 2016). Moreover, perhaps we should be looking for weird forms of life on weird planets (Schulze-Makuch + Irwin, 2018). Exoplanet specialists are particularly interested in atmospheric biosignatures or even technosignatures, while Solar System specialists have reduced their expectations phototrophs (Mars) or simply chemotrophs (the icy satellites) or life forms in the clouds of Venus.

My approach to the search for life elsewhere is conservative and solidly based on my studies of the early Earth. Life based on organic molecules with water as the solvent is probably common on rocky planets with water (either ocean planets, planets like Earth, or land-locked planets) for the reason that the ingredients of life were readily available (Westall + 2023a). In the Solar System, we may be looking for protocells or simple organisms using metabolisms based on chemotrophy. Possibly anoxygenic phototrophs developed on Venus if it was ever habitable, less likely on Mars because of the lack environments with long term, continuous habitability (several hundreds of My). More than a billion years were needed for oxygenic photosynthesis to appear on Earth, a continuously habitable planet with an equable environment.

Our best chance at finding extraterrestrial life presently is Mars, although the environments presently being examined seem to be rather sterile. If, for instance, we strike lucky and Perseverance does manage to return a sample that contains potential biosignatures, to what lengths do we need to go to establish that they are really traces of life and not some artefact or terrestrial contamination? Experiences related to trying to establish evidence for the most ancient traces of life on Earth, as well as the example of the Allen Hills 84001 meteorite (McKay + 1996; Westall + 2021) warn me that there will be huge debate among the scientists for many years until a consensus is arrived at. In the meantime, the general public will be wanting to know, is there life on Mars or not? And we will not be able to answer that question easily, even with samples in hand.

Contributed Talks

Armando Azua-Bustos, Centro de Astrobiologia, Spain “What are we actually looking for as evidence of life on Mars?”

Identifying unequivocal signs of life on Mars is one of the most important objectives for sending missions to the red planet. Here I will present Red Stone, a 163-100 My alluvial fan-fan delta that formed under arid conditions in the Atacama Desert, rich in hematite and mudstones containing clays such as vermiculite and smectites, and therefore geologically analog to Mars. In addition to find an important number of microorganisms with an unusual high rate of phylogenetic indeterminacy, we found a mix of biosignatures from extant and ancient microorganisms that can be barely detected with state-of-the-art laboratory equipment. Strikingly, the analyses by testbed instruments that are on or will be sent to Mars unveiled that similarly low levels of organics will be hard, if not impossible to detect in Martian rocks depending on the instrument and technique used. This brought to the question on what are actually looking for as evidences of life on Mars?, to which I will try to answer by discussing alternatives from movement to fractal mathematics analyses.

David Clements, Imperial College London, UK “Venus Phosphine: Updates and lessons learned”

The discovery of phosphine in the atmosphere of Venus provides many useful lessons for the search for life elsewhere. Following the discovery paper in 2020 there were numerous discussions and challenges regarding both the data analysis used and the interpretation of the data. The detection has so far survived all of these and has acquired additional independent support through the use of archival data from Pioneer Venus Probe. The presence of phosphine, PH3, in the highly oxidising environment of Venus is perplexing, compounded by comprehensive studies that have ruled out all known abiotic sources. More data is needed to solidify the detection and understand the origin of the gas. This leads to the JCMT-Venus project, a programme for long term monitoring of the atmosphere of Venus at mm wavelengths with much improved sensitivity and bandwidth compared to previous data, allowing multiple species to be studied simultaneously. This has the potential to reveal how phosphine varies in relation to other species such as water and SO2, providing clues to its chemical (or potentially biological) origin. We will present the latest results and updates from the JCMT-Venus programme. The original discovery paper and subsequent papers were explicit that this discovery did not constitute evidence for life, only evidence of phosphine and its potential sources. The media and public reaction to the discovery of phosphine, its implications, and the possibility of life on Venus provides useful lessons for future life searches, as does the reaction of the scientific community. How this was handled by the Venus Phosphine team, by the media, and by the general public will be reviewed. Lessons learned from this will be discussed.

Niklas Döbler, University of Bamberg, Germany “Searching for false negatives: On the necessity of extraterrestrial participation for human recognition and beyond”

SETI may have already succeeded, even though we are not aware of it. By limiting the human search to a presupposed configuration of expected signals, SETI was always constrained and made possible by the same factors. These presumptions are necessary to start the search in the first place but can also be causally responsible for producing false negatives. Humanity may already possess data that has not been adequately interpreted yet. Abstracted from the technological details, the mechanism at work is that extraterrestrials must participate in a shared consensual space of established behavior, customs, and conventions to be detectable. Although it encompasses other earthly life forms, this space is necessarily an irreducible anthropocentric for humans. Hypothesizing contact scenarios with fast-paced information exchange or visual contact, it becomes evident that from the human perspective, extraterrestrial, or to be more precise, mutual participation, is not only necessary for recognition, i.e., detection, but lays down the foundation for successful communication, understanding, interaction and moral valuation. Within practical SETI, mutual participation means an alignment of technosignatures and detection devices. Applied to a framework of interspecies communication, this aspect refers to the necessity to observe behavioral expression of counterparts as meaningful. The ascribed meaning is likely to determine the assigned interactional status. We seek to elucidate the relevant factors that constitute the possibility of reliable and mutual participation. Understanding these factors serves a preparational purpose for a successful contact to (and interaction with) other species.

Chris Impey, University of Arizona, USA “Extraterrestrial intelligent life: What the public believes”

Astrobiologists are moving purposefully towards a detection of extraterrestrial intelligence through the radio and optical methods of SETI. Meanwhile, members of the general public have formed their own opinions, only partially informed by science. In the United States, two thirds of all adults believe there is intelligent life beyond Earth, and a substantial minority believe we have already made contact. Opinions about the existence and nature of aliens are part of a complex landscape of beliefs that includes pseudoscience and superstition and extends to conspiracy theories. Widespread belief that UFOs represent visits by ETI is at the center of this landscape. Beliefs about ETI are also shaped by films, TV shows, and popular culture. This chapter summarizes what the public believes about ETI and presents possible explanations for these beliefs. Data comes from polls by Reuters, Gallup, Ipsos, and CBS News. International comparisons are presented. The author has surveyed the opinions and beliefs of thousands of students on topics relating to life beyond Earth and the data give insights into the thinking of the college-age population. People are not “blank canvasses” when it comes to their expectations of ETI, and this must be taken into account by the scientists who are preparing for eventual, actual contact.

Saeed Jafari, Space Generation Advisory Council, Iran “Using linguistics and information theory to assess the diversity, complexity and decoding of interstellar messages”

This abstract explores the application of quantitative information theory measures and linguistic features to analyze animal communication systems and extends this methodology to contemplate the possibilities of interstellar communication as a part of CETI practice. We will assess some early findings by using information theory on social species with sophisticated acoustic communication abilities, such as bottlenose dolphins and humpback whales (Hanser, Sean F., et al.) as well as birds, as examples of how the complex interplay between notions, data, and misinterpretations can become established as reliable knowledge and cognition about and understanding of an ETI civilization and culture. The study also looks into the potential implications of extraterrestrial contact. Given the diversity of language instances in Earth’s evolutionary history, we discuss the choice of syntactic complexity of an “intelligent message” for potential alien civilizations. The central point of this talk is to examine the advantages and limitations of acoustic and visual communication, considering linguistical and mathematical constraints that may apply universally. Next, we contemplate the two main scenarios in which humans might communicate with extraterrestrial intelligences – decoding alien signals and facilitating two-way communication. This analysis draws upon our understanding of interspecies communication on Earth, highlighting the challenges of decoding alien languages and the need for a ‘Rosetta Stone’ equivalent to bridge the transmission gap.

Sohan Jheeta, NoRCEL, UK “Emergence of life: Importance of formation of organic molecules of life”

It is believed that some of the necessary organic molecules may have been formed in specific areas of space (namely dark molecular clouds, e.g. Horsehead nebula) and delivered on to the Earth during the early heavy bombardment period of its history, approximately 4.3-4.0 billion years ago. These organic molecules may have played a pivotal role in the formation of life on Earth. In addition, it is believed that life on Earth was formed within a very short geological time frame of only 200-300 million years. So, it is not unreasonable to suppose that these molecules were initially made in space which in effect could be, metaphorically speaking, a huge chemical laboratory.

The research (drawn from my own experimental astrochemistry) highlighted during this oral presentation focuses on the formation of molecules under a variety of simulated space conditions (e.g. different temperatures, levels of radiation energies and types of impinging radiations). There are two sorts of chemistry that take place in space, solid and gas phase, and although only 25% of the chemistry in space occurs in the solid phase, this will be the focus of my oral presentation.

Pallavi Kajrekar, University of Edinburgh, UK “Surviving the cosmos: Biomolecule stability beyond the Earth”

The origin of life on earth has long fascinated scientists and laymen alike. One of the leading theories, supported by Carl Sagan, says that life on Earth started via cometary delivery of organic molecules. If that’s the case, we run into a huge problem. How did delicate biomolecules bonded only by covalent bonds (e.g., sugars, amino acids, lipids, etc.) survive such a hostile journey through the interstellar and extra stellar medium. Hostile conditions in outer space include cosmic rays, vacuum and extreme conditions of temperature and pressure. We might be able to answer the survivability of these biomolecules by looking at their stability. By using computational interdisciplinary models, we can see the bond breaking thresholds for important biomolecules on exposure to hostile conditions over astrophysical timescales. It will in turn help us understand the chemistry of life on Earth in a much more detailed manner. This approach also has potential to reveal the seemingly miraculous jump that life on Earth made from abiotic organics to functioning biotic systems.

Kevin Knuth, University of Albany, USA “Simulating the characteristics of extra-terrestrial civilizations that encounter Earth”

Given what is now known about the populations of planets, and the generation, prevalence and distribution of complex organic molecules in space, it is generally believed that it is unlikely that our civilization is alone in this galaxy. This idea is central to the concept of the Search for Extraterrestrial Intelligence (SETI), which has focused mainly on searching for radio signals originating from extraterrestrial communications, since it is expected that extraterrestrial craft visiting Earth would be an extremely unlikely event. However, the fact that we have explored the major bodies of our solar system and are now working toward sending probes to the Alpha Centauri system by 2069, a century after the first Moon landings, suggests that other civilizations may make similar efforts. Therefore, it is reasonable to contemplate what characteristics we might expect of an interstellar civilization that is capable of encountering Earth.

One way to evaluate those expectations is to use our knowledge of physics to simulate a large number of colonizing civilizations across the galaxy, and to compile statistics for all the civilizations that happen to encounter Earth. The problem is that given the difficulty of space travel, the immense distances involved, and the enormous number of star systems to explore, we expect that such encounters will be extremely rare with successful civilizations occupying a very small region of the civilization parameter space. This makes sampling extremely difficult. To surmount this difficulty, we rely on the nested sampling algorithm to focus exploration on the relevant regions of parameter space from which we can then obtain unbiased statistics on hypothetical, yet physically-plausible, space-faring civilizations capable of discovering, visiting, and possibly even establishing a presence on, Earth.

Eva Mateo-Martí, Centro de Astrobiologia, Spain “From laboratory simulation facilities to the search for life beyond Earth”

While space missions and space telescopes provide fundamental and unique insights to explore our own Solar System, they are always costly and time-consuming. Planetary atmospheres can now be examined for signs of life by focusing on data derived from these new technologies. However, due to technical and economic constraints on space exploration, laboratory simulations are one of the most feasible research options to advance both space and planetary science and a consistent description of the origin of life. Planetary Atmosphere and Surfaces Chamber (PASC) is able to simulate atmosphere and surface temperature of most planetary objects and is especially appropriate to study physico-chemical and biological changes induced in a particular sample due to in-situ irradiation in a controlled environment. Number of relevant applications in planetary exploration will be described in order to provide an understanding about the potential and flexibility of planetary simulation chamber system: mainly, stability and presence of certain minerals on Mars surface; UV-photocatalytic N2 fixation process on mineral surfaces; photochemistry process on molecules, identifications of spectroscopic fingerprints corresponding to relevant molecular/minerals in Mars environments and microorganisms potential habitability under planetary environmental conditions have been studied. Therefore, simulation chambers assess several multidisciplinary and challenging planetary and astrobiological studies. Furthermore, they will be a promising tool and a necessary platform to design future space mission and validate in-situ measurements from orbital or rover observations, searching for spectroscopic fingerprints to correlate with plausible signs of life.

Anthony Milligan, King’s College London, UK “Equivocal encounters: ‘Oumuamua and the prospects for disagreement about artifacts”

Discussions about the possibility of human encounters with intelligent alien life have been plagued by a tendency to sideline our normal standards of evidence. One thing looks a little like something else, and some overly strong conclusion is then drawn: e.g., the Tunguska event looks a little like a nuclear explosion, therefore it was probably the result of an alien craft blowing up (at a suitable height). Identifying pseudoscience about alien encounters is simple. But what would good science in support of an alien encounter look like? This is a harder question but also one that we should at least try to answer. After all, the legitimacy of dismissing familiar kinds of pseudoscience on the grounds of its lack of proper standards, presupposes that some appropriate set of standards really could be specified. At least, this holds for the most likely form of actual encounter. We will assume that the most likely encounter would be with a derelict rather than a functioning ship, or with some other artefact rather than in the flesh aliens. This assumption is based upon the familiar point that the timescales required for interstellar travel, using known physics, really would pose a massive obstacle for human-live alien encounters. But when it comes to derelicts and artifacts in general, it may be less than clear cut that we have encountered something alien rather than a naturally occurring phenomenon. This is one of the take-away lessons from the discussions around the interstellar object ‘Oumuamua. If we were to follow a popular contemporary approach to the Fermi Paradox, i.e., a dark forest approach, then genuine artifacts could, in theory, be disguised to look (from a distance) like naturally occurring phenomena precisely in order to evade detection. Again, any encounter from a distance may be equivocal. At best, we may have good but less than compelling scientific grounds for affirming the genuineness of an alien encounter. Divisions across scientific communities are a likely outcome and broader societal attitudes can hardly be expected to be more univocal. In this paper, we will try to do two things. First, we will try to clarify a ‘standards of evidence’ problem as a problem concerned with (a) range of evidence rather than one decisive consideration; and (b) probabilities rather than criteria for a definitive binary judgement. Second, we will respond to the standards of evidence problem in the light of the ‘Oumuamua discussion, and the way in which it raised practical and tractable questions about what would count as sufficient evidence for the genuineness of an artifact. We will argue that, even given the strong likelihood of scientific disagreement, a broad scientific research program can be built around the hypothesis that ‘Oumuamua, or any other particular interstellar object, is an alien craft and that, even in the case of an equivocal encounter, there are well-ordered and disciplined standards of evidence which may be applied.

Raghav Narasimha Ponnaganti, Indian Institute of Astrophysics “Making habitable worlds: Planets versus megastructures”

In 2015, the star KIC 8462852 caught the world’s attention due to a paper authored by citizen scientists who observed unexplainable brightness variations. Subsequently, a forward theory was suggested that KIC 8462852 is surrounded by a Dyson Sphere, a megastructure built by extraterrestrial intelligence (ETI) to collect all the energy output from their star. However, a detailed analysis of its light-curve revealed chromaticity which is more consistent with interplanetary dust than a solid object, but the world was woken up to the idea of megastructures. When the concept of megastructures was initially introduced by Dyson in 1960, our knowledge was confined to the planets within our own Solar System. It took over three decades to comprehend that nature has no problem making planets and does it with a flair. Besides, to construct just an 8-cm thick shell around the sun at Earth’s radius would require all of the Solar System’s rocky material including Earth, destroying any possible life, which goes against the principle of Planetary Protection – UN policies governing the preservation of Solar System bodies. The total number of planets in our galaxy is estimated to be in billions, with such an abundance of planets, there would be no need to destroy the entire planetary system to make one sphere. Instead, ETI can relocate planets into the habitable zone of the system, or even a free-floating planet can be moved into the system. These shifts can be performed at a constant low-thrust acceleration using high-power directional lasers, resulting in a gradual spiral transfer from one orbit to another. We propose to search for ETI by looking for such high-power laser technosignatures and consider the merits of such technosignatures. We suggest that planetary systems with strange exoplanetary architectures (SEA), could be the result of ETI moving planets intentionally to suit their needs.

Julie Nekola Nováková, Charles University, Czech Republic “Teaching by imagining Life Beyond Us: Science fiction for outreach and education”

I will present educational materials and outreach strategies stemming from the ‘Life Beyond Us’ anthology project by the European Astrobiology Institute (EAI), bringing topics such as planetary protection closer to the classroom and the public. The book itself utilizes science-inspired science fiction stories, each accompanied by a science essay written by an expert in the topic present in the story (be it planetary protection, major evolutionary transitions, habitability of ocean planets, SETI and many more). Stephen Baxter contributed an introduction to the anthology, while other renowned authors wrote the stories, and expert scientists penned the essays.

Science fiction, due to its wide popularity, has the potential to reach more communities, even those as-of-yet less represented in science. Moreover, narrative-based learning has shown potential for creating interest and facilitating memory, although more research is needed to show its actual efficacy (and to carefully distinguish the many different approaches falling under this generalized label). Stories in ‘Life Beyond Us’ (and its preceding e-book anthology ‘Strangest of All’) were developed to showcase different aspects of astrobiology, spark interest in the readers and thus create greater motivation for learning through the science essays.

Astrobiology, itself popular among the public, is perfect for communicating news and concepts from the many fields it encompasses. But it is also prone to widespread misunderstandings about finding alien life, with many people thinking it has already been reliably found or harboring misconceptions about how it could be found. More scientifically realistic science fiction stories, combined with further materials (essays in the book, plus freely available online materials for educators), can help correct misconceptions, while retaining the sense of wonder connecting people to the field. I will present the outcomes, advantages and disadvantages of our approach, insights learned at the recent ESA Brainstorming in Astrobiology, and planned future steps for creating a European network of astrobiology researchers, educators and artists active (not only) in the science fiction genre across media.

Luke Sellers, University of California at Los Angeles (UCLA), USA “Searching for intelligent life in gravitational wave signals”

LIGO’s ability to detect gravitational waves (GWs) from astrophysical sources, such as binary black hole mergers, also provides the potential to detect extraterrestrial mega technology, such as Rapid and/or Massive Accelerating spacecraft (RAMAcraft). We discuss how LIGO is sensitive to RAMAcraft of 1 Jupiter mass accelerating to a fraction of the speed of light (e.g. 30%) around our Galaxy or a Moon mass within our solar neighborhood. Moreover, we will be able to probe the entire Local Group and beyond with upcoming detectors such as DECIGO or BBO. We calculate the waveforms for linearly-accelerating RAMAcraft in a form suitable for LIGO, Virgo, and KAGRA searches and provide the range for a variety of masses and accelerations. While existing SETI searches can probe on the order of ten thousand stars for human-scale technology (e.g. radio waves), LIGO can probe all stars in the Milky Way for RAMAcraft. We therefore expect that the current and upcoming GW detectors will soon become an excellent complement to the existing SETI efforts.

Shirin Shater Zadeh Yazdi, Shahid Beheshti University, Iran “Finding intelligent life and first contact scenario: Towards public awareness and engagement and the impact of discovery”

The prospect of human contact with extraterrestrial intelligence (ETI) carries profound societal implications, far surpassing the impact of discovering non-sentient microbes on distant planets. Such an encounter would reverberate throughout human society, challenging established beliefs, including theological doctrines, and reshaping our cosmic perspective. During the last decade, the search for extraterrestrial intelligence (SETI) and non-intelligent extraterrestrial life has received notable attention in digital media and newspapers and influenced public thoughts and perceptions about astrobiology, SETI and planetary science fields. This talk takes a science communication and society perspective, evaluating our current decision-making processes and policies in anticipation of potential discoveries and their consequential interactions with varying forms of extraterrestrial life, including public attitudes, news dissemination and rumour control, and decoding and messaging ETIs. We explore various types of ET life and phases (during searches, upon discovery, and post-discovery), drawing insights from established public communication management and media analysis methodologies. We will underscore the essentiality of public awareness, engagement, and understanding in response to the profound societal implications of discovering extraterrestrial intelligence. This provides a structured framework for raising awareness about SETI and science communication activities, with defined aims and intended outcomes. We finally overview the lessons learned from outreach projects such as SETI@home, A Sign in Space, Galaxy Zoo, etc., and reflect effective actions on future initiatives.

Philipp Spillmann, University of Cambridge, UK “How weird is ‘weird’ life?”

In the astrobiological literature, the search for life is often portrayed as a dilemma between searching for ‘earth-like’ life and ‘earth-unlike’ or ‘weird’ kinds of life. However, there is little scientific or philosophical clarity as to what exactly ‘earth-likeness’ and ‘earth-unlikeness’ is supposed to amount to, how it should be measured, and to what phenomena it can be applied. In this talk, I present a framework for classifying, measuring, and evaluating different ways in which life can (meaningfully said to) be ‘weird’, that is, ‘unlike’ life on Earth.

In a first step, I introduce some ways in which alien life have been conceptualized as potentially different from life on Earth. In the literature, we encounter a quite heterogenous set of notions, such as ‘unfamiliar life’, ‘weird life’, ‘life as we don’t know it’, etc. I argue that notions like these tend to be used in a vague or ambiguous manner to refer to a variety of traits, facts, or phenomena that are often not clearly connected or clearly in opposition to Earth-like life. This lack of clarity, as I argue, obscures the way we think (a) about the limits of our own current knowledge of life and (b) about false positives and false negatives in the search for extraterrestrial life. Unless talk about unknown kinds of life is meant to be merely metaphorical, we need to be careful to think of alternative kinds of life in a consistent and precise way.

In a second step, I present a framework for analysing different kinds of ‘weird life’ and ‘weirdness’. To begin with, we should distinguish between naturalistic ‘kinds of life’ (which focus on traits) and epistemic ‘kinds of life’ (which focus on our scientific knowledge of such traits). I argue that notions such as ‘unfamiliar life’ or ‘weird life’ cannot be properly understood in a naturalistic way, that is, they do not properly translate into a coherent set of physical, chemical, biological, or ecological differences that may or may not distinguish life on Earth from life on other planets. ‘Weirdness’, as I claim, is best understood as an epistemic notion, referring to the way we scientifically inquire and theorize about life. I argue that we must distinguish between first-order weirdness (which focuses on knowledge claims that express scientific facts or counterfactuals about life) and second-order weirdness (which focuses knowledge claims that express facts or counterfactuals about the scientific study of life). Both types of weirdness come in degrees. 1st order weirdness: Some kinds of alien life can be weirder than others with respect to life on Earth either (i) by sharing a smaller number of characteristics with life on Earth that are fundamental for life on Earth or (ii) by having more characteristics that life on Earth cannot have. 2nd order weirdness: Some kinds of alien life can be weirder than others with respect to life on Earth (iii) by having more characteristics than others that life should not have according to our currently best-justified scientific knowledge.

In a final step I briefly discuss how weirdness translates into problems of prediction and confirmation in the search for extraterrestrial life. Namely, I argue that degrees in weirdness do not correspond to degrees in unpredictability: It is not necessarily true that the less characteristics alien life shares with life on Earth, the less well we can identify that kind of life (i.e. distinguish it reliably from non-life). Neither do the weirdest kinds of life do have to be the least predictable ones, nor do the least weird kinds of life have to be the most predictable ones.

Peter Vickers, Durham University, UK “Just when have we discovered life beyond Earth?”

Potential biosignatures that offer the promise of extraterrestrial life (past or present) are to be expected in the coming years and decades, whether from within our own solar system, from an exoplanet atmosphere, or otherwise. With each such potential biosignature, the degree of our uncertainty will be the first question asked. Have we really identified extraterrestrial life?How sure are we? In Vickers et al. 2023 we address these questions, considering the so-called “problem of unconceived alternative explanations”. We stress that articulating our uncertainty requires an assessment of the extent to which we have explored the relevant possibility space. It is argued that, for most conceivable potential biosignatures, we currently have not explored the relevant possibility space very thoroughly at all. Not only does this severely limit the circumstances in which we could reasonably be confident in our detection of extraterrestrial life, it also poses a significant challenge to any attempt to quantify our degree of uncertainty. The discussion leads us to the following recommendation: when it comes specifically to an extraterrestrial life detection claim, the astrobiology community should follow the uncertainty assessment approach adopted by the Intergovernmental Panel on Climate Change (IPCC).

Amri Wandel, Hebrew University of Jerusalem, Israel “Extending the habitable zone due to subglacial water”

The circumstellar region with a potential for liquid water is extended well beyond the conservative boundaries of the classical Habitable Zone. According to the model of Wandel (2023a,b) it is shown how liquid water could survive on tidally locked planets closely orbiting an M-dwarf host. In addition, subglacial liquid water could extend the Habitable Zone beyond its outer boundary. It is argued that the probable recent JWST detection of atmospheric water vapor on the rocky Earth-sized exoplanet GJ 486 b, along with earlier detections of water on other planets orbiting M-dwarf stars gives an empirical answer to the much-argued question, of whether such planets can support liquid water, organic chemistry and eventually life.