Pub Date : 2022-08-26DOI: 10.1017/S1473550422000325
Kensei Kobayashi, Philippe Nauny, Y. Takano, Chiho Honma, Taihei Kurizuka, Yuto Ishikawa, Shusuke Yogosawa, Y. Obayashi, T. Kaneko, Y. Kebukawa, H. Mita, M. Ogawa, K. Enya, Yoshitaka Yoshimura, C. Mckay
Abstract Microbiological activities can be detected in various extreme environments on Earth, which suggest that extraterrestrial environments, such as on Mars, could host life. There have been proposed a number of biomarkers to detect extant life mostly based on specific molecules. Because terrestrial organisms have catalytic proteins (enzymes), enzymatic activity may also be a good indicator to evaluate biological activities in extreme environments. Phosphatases are essential for all terrestrial organisms because phosphate esters are ubiquitously used in genetic molecules (DNA/RNA) and membranes. In this study, we evaluated microbial activity in soils of the Atacama Desert, Chile, by analysing several biomarkers, including phosphatase activity. Phosphatases extracted with Tris buffer were assayed fluorometrically using 4-methylumbelliferyl phosphate as a substrate. The horizontal distribution of phosphatase activity and other parameters in soils from the Atacama Desert showed that phosphatase activity was positively correlated with amino acid concentration and colony-forming units and negatively correlated with precipitation amount. We found consistent that biochemical indicators including phosphatase significantly decreased in the extreme hyper-arid zone where rainfall of <25 mm year−1. The results were compared with phosphatase activities detected in extreme environments, such as submarine hydrothermal systems and Antarctic soils, as well as soils from ordinary environments. Overall, our results suggested that phosphatase activity could be a good indicator for evaluating biological activities in extreme environments.
{"title":"Biomarkers in the Atacama Desert along the moisture gradient and the depth in the hyperarid zone: Phosphatase activity as trace of microbial activity","authors":"Kensei Kobayashi, Philippe Nauny, Y. Takano, Chiho Honma, Taihei Kurizuka, Yuto Ishikawa, Shusuke Yogosawa, Y. Obayashi, T. Kaneko, Y. Kebukawa, H. Mita, M. Ogawa, K. Enya, Yoshitaka Yoshimura, C. Mckay","doi":"10.1017/S1473550422000325","DOIUrl":"https://doi.org/10.1017/S1473550422000325","url":null,"abstract":"Abstract Microbiological activities can be detected in various extreme environments on Earth, which suggest that extraterrestrial environments, such as on Mars, could host life. There have been proposed a number of biomarkers to detect extant life mostly based on specific molecules. Because terrestrial organisms have catalytic proteins (enzymes), enzymatic activity may also be a good indicator to evaluate biological activities in extreme environments. Phosphatases are essential for all terrestrial organisms because phosphate esters are ubiquitously used in genetic molecules (DNA/RNA) and membranes. In this study, we evaluated microbial activity in soils of the Atacama Desert, Chile, by analysing several biomarkers, including phosphatase activity. Phosphatases extracted with Tris buffer were assayed fluorometrically using 4-methylumbelliferyl phosphate as a substrate. The horizontal distribution of phosphatase activity and other parameters in soils from the Atacama Desert showed that phosphatase activity was positively correlated with amino acid concentration and colony-forming units and negatively correlated with precipitation amount. We found consistent that biochemical indicators including phosphatase significantly decreased in the extreme hyper-arid zone where rainfall of <25 mm year−1. The results were compared with phosphatase activities detected in extreme environments, such as submarine hydrothermal systems and Antarctic soils, as well as soils from ordinary environments. Overall, our results suggested that phosphatase activity could be a good indicator for evaluating biological activities in extreme environments.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"329 - 351"},"PeriodicalIF":1.7,"publicationDate":"2022-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47999300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-08-17DOI: 10.1017/s1473550422000295
Slobodan Perović
I outline a general thermodynamic condition for the earliest steps in the origin of life based on fluctuation theorems developed in the last two decades. I argue that the exponentially developing loop of asymmetric autocatalysis and thermodynamic tail-wind condition (TTC) in the prebiotic clutter was a key to a particular trajectory of decluttering via a sequence of early symmetry breaking events. Such decluttering was bound to result, most prominently, in homochiral amino acids and homochiral sugars composing nucleotides as the TTC exponentially favoured asymmetric autocatalytic processes over catalytic and symmetric autocatalytic processes in the clutter. I describe the loop's structure, including its chemical and physical properties, and explain that the TTC/asymmetric autocatalysis loop intersected with multiple chemical, geological and climatological feedback loops, thus providing conditions for the propagation of living systems as we know them.
{"title":"Prebiotic decluttering: the thermodynamic tail-wind to asymmetric autocatalysis","authors":"Slobodan Perović","doi":"10.1017/s1473550422000295","DOIUrl":"https://doi.org/10.1017/s1473550422000295","url":null,"abstract":"\u0000 I outline a general thermodynamic condition for the earliest steps in the origin of life based on fluctuation theorems developed in the last two decades. I argue that the exponentially developing loop of asymmetric autocatalysis and thermodynamic tail-wind condition (TTC) in the prebiotic clutter was a key to a particular trajectory of decluttering via a sequence of early symmetry breaking events. Such decluttering was bound to result, most prominently, in homochiral amino acids and homochiral sugars composing nucleotides as the TTC exponentially favoured asymmetric autocatalytic processes over catalytic and symmetric autocatalytic processes in the clutter. I describe the loop's structure, including its chemical and physical properties, and explain that the TTC/asymmetric autocatalysis loop intersected with multiple chemical, geological and climatological feedback loops, thus providing conditions for the propagation of living systems as we know them.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45842635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-08-12DOI: 10.1017/S1473550422000271
A. Maris, L. Favero, Wentao Song, D. Lv, L. Evangelisti, S. Melandri
Abstract The identification and quantification of molecules in interstellar space and atmospheres of planets in the solar systems and in exoplanets rely on spectroscopic methods and laboratory work is essential to provide the community with the spectral features needed to analyse cosmological observations. Rotational spectroscopy in particular, with its intrinsic high resolution, allows the unambiguous identification of biomolecular building blocks and biosignature gases which can be correlated with the origin of life or the identification of habitable planets. We report the extension of the measured rotational transition frequencies of dimethylsulphoxide and its 34S and 13C isotopologues in the millimetre wave range (59.6–78.4 GHz) by use of an absorption spectrometer based on the supersonic expansion technique. Hyperfine patterns related to the methyl group internal rotation were analysed in the microwave range region (6–18 GHz) with a Pulsed Jet Fourier Transform spectrometer at extremely high resolution (2 kHz) and reliable predictions up to 116 GHz are provided. The focus on sulphur-bearing molecules is motivated by the fact that sulphur is largely involved in the intra- and inter-molecular hydrogen bonds in proteins and although it is the 10th most abundant element in the known Universe, understanding its chemistry is still a matter of debate. Moreover, sulphur-bearing molecules, in particular dimethylsulphoxide, have been indicated as possible biosignature gases to be monitored in the search of habitable exoplanets.
{"title":"Searching for biosignatures by their rotational spectrum: global fit and methyl group internal rotation features of dimethylsulphoxide up to 116 GHz","authors":"A. Maris, L. Favero, Wentao Song, D. Lv, L. Evangelisti, S. Melandri","doi":"10.1017/S1473550422000271","DOIUrl":"https://doi.org/10.1017/S1473550422000271","url":null,"abstract":"Abstract The identification and quantification of molecules in interstellar space and atmospheres of planets in the solar systems and in exoplanets rely on spectroscopic methods and laboratory work is essential to provide the community with the spectral features needed to analyse cosmological observations. Rotational spectroscopy in particular, with its intrinsic high resolution, allows the unambiguous identification of biomolecular building blocks and biosignature gases which can be correlated with the origin of life or the identification of habitable planets. We report the extension of the measured rotational transition frequencies of dimethylsulphoxide and its 34S and 13C isotopologues in the millimetre wave range (59.6–78.4 GHz) by use of an absorption spectrometer based on the supersonic expansion technique. Hyperfine patterns related to the methyl group internal rotation were analysed in the microwave range region (6–18 GHz) with a Pulsed Jet Fourier Transform spectrometer at extremely high resolution (2 kHz) and reliable predictions up to 116 GHz are provided. The focus on sulphur-bearing molecules is motivated by the fact that sulphur is largely involved in the intra- and inter-molecular hydrogen bonds in proteins and although it is the 10th most abundant element in the known Universe, understanding its chemistry is still a matter of debate. Moreover, sulphur-bearing molecules, in particular dimethylsulphoxide, have been indicated as possible biosignature gases to be monitored in the search of habitable exoplanets.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"405 - 422"},"PeriodicalIF":1.7,"publicationDate":"2022-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41598050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-08-02DOI: 10.1017/S1473550422000283
R. Barbieri, B. Cavalazzi
Abstract In the only salt evaporation pond retaining its natural setting of the historic Salina di Cervia (Italy), the northernmost salterns of the Mediterranean area, a number of potentially preservable textures derive from the interactions between photosynthetic mat producers and the sedimentary substrate. These morphologies occur at the beginning of the taphonomic processes when repeated emerged-submerged conditions take place. In these conditions the cohesive nature of the diatom- and cyanobacterial-derived mucilage favours the stabilization of otherwise ephemeral structures. Surface micromorphologies for which diatoms and cyanobacteria have played some active role when still living in the soft microlayer and down to the sediment-water interface, such as during the gliding motility, can overcome the surface layer of most intense mixing (i.e., the taphonomically active zone) and keep traces of them in the fossil record either as body fossils or as texture contributors. Tiny microbial-derived remnants, such as filaments and biofilm strands of halotolerant microorganisms, while fragile upon their formation, can therefore stabilize as biosignatures when combined with salt precipitation. Halophilic and halotolerant ecosystems are models for life in extreme environments (analogue sites) with similarity to those strongly suspected to occur and/or have occurred on Mars and on other planetary bodies. The study of hypersaline systems such as Salina di Cervia which harbour diverse and abundant microbial life, can be relevant for astrobiology since it allows the investigation of potential biosignatures and their preservation, and of further understand the range of conditions and the planetary processes sustaining potentially habitable systems.
在地中海地区最北端的盐沼——意大利历史悠久的Cervia盐沼(Salina di Cervia)，唯一保留其自然环境的盐蒸发池中，许多潜在的可保存纹理来自光合作用席生产者和沉积基质之间的相互作用。这些形态发生在埋藏过程的开始，当反复出现的淹没条件发生时。在这些条件下，硅藻和蓝藻衍生的黏液的凝聚力有利于稳定其他短暂的结构。硅藻和蓝藻在生活在软质微层及沉积物-水界面时，如在滑动运动期间，对表面微形态发挥了积极作用，它们可以克服最强烈混合的表层(即埋藏活跃带)，并作为体化石或纹理贡献物在化石记录中留下痕迹。微生物衍生的微小残留物，如耐盐微生物的细丝和生物膜链，虽然在形成时很脆弱，但当与盐沉淀结合时，可以作为生物特征稳定下来。嗜盐和耐盐生态系统是极端环境(模拟地点)中的生命模式，与强烈怀疑在火星和其他行星上可能发生和/或已经发生的生命模式相似。研究高盐系统，如Salina di Cervia，它拥有多样化和丰富的微生物生命，可以与天体生物学相关，因为它允许调查潜在的生物特征及其保存，并进一步了解维持潜在宜居系统的条件范围和行星过程。
{"title":"Early taphonomic processes in a microbial-based sedimentary system from a temperate salt-pan site (Cervia salterns, Italy)","authors":"R. Barbieri, B. Cavalazzi","doi":"10.1017/S1473550422000283","DOIUrl":"https://doi.org/10.1017/S1473550422000283","url":null,"abstract":"Abstract In the only salt evaporation pond retaining its natural setting of the historic Salina di Cervia (Italy), the northernmost salterns of the Mediterranean area, a number of potentially preservable textures derive from the interactions between photosynthetic mat producers and the sedimentary substrate. These morphologies occur at the beginning of the taphonomic processes when repeated emerged-submerged conditions take place. In these conditions the cohesive nature of the diatom- and cyanobacterial-derived mucilage favours the stabilization of otherwise ephemeral structures. Surface micromorphologies for which diatoms and cyanobacteria have played some active role when still living in the soft microlayer and down to the sediment-water interface, such as during the gliding motility, can overcome the surface layer of most intense mixing (i.e., the taphonomically active zone) and keep traces of them in the fossil record either as body fossils or as texture contributors. Tiny microbial-derived remnants, such as filaments and biofilm strands of halotolerant microorganisms, while fragile upon their formation, can therefore stabilize as biosignatures when combined with salt precipitation. Halophilic and halotolerant ecosystems are models for life in extreme environments (analogue sites) with similarity to those strongly suspected to occur and/or have occurred on Mars and on other planetary bodies. The study of hypersaline systems such as Salina di Cervia which harbour diverse and abundant microbial life, can be relevant for astrobiology since it allows the investigation of potential biosignatures and their preservation, and of further understand the range of conditions and the planetary processes sustaining potentially habitable systems.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"308 - 328"},"PeriodicalIF":1.7,"publicationDate":"2022-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44253278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-08-01DOI: 10.1017/S1473550422000301
A. Ellery
In the early 1980s, Carl Sagan and Frank Tipler published a series of articles in the pages of the Quarterly Journal of the Royal Astronomical Society on ETI that became a cause celebre at the time. Whilst reading for an MSc in Astronomy at the University of Sussex in the early 1990s, I expressed my interest in SETI as a staunch Saganite (influenced not only by the phenomenal Cosmos TV series, recently re-vamped by Neil de Grasse Tyson, but also by Sagan’s preceding Royal Institution Christmas lecture series) to Professor John Barrow who introduced me to the relevant chapter in the book The Anthropic Cosmological Principle that he co-authored with Frank Tipler (I still recommend the entire book for its visionary scope). I immediately went to source material and was struck by the von Neumann or self-replicating probe concept under discussion (I shall use the latter term to avoid conflation with von Neumann machine which has a well-established meaning in computer engineering). This was my road to Damascus in converting me from ETI believer to skeptic (but by the power of scientific argument rather than any epiphany). Thence, I decided to pursue a PhD in space engineering specialising in space robotics (though my research project was rather more mundane than self-replicating probes). Yet, despite its foundational importance, the Sagan-Tipler debate is almost forgotten today despite the fact that it exposes the root-and-branch of the SETI venture. However, every now and then, there is still the occasional paper on self-replicating probes but they appear to be sidestream to the SETI programme. This special issue seeks to re-focus the self-replicating probe back into the SETI mainstream where it belongs. There are four papers in this special issue. Dobler’s (2022) paper provides the ideal contextual discussion of the Fermi paradox that extant ETI are not here now. He suggests that any optimistic interpretation must accept that there must be a low probability of contact and that this state of affairs shall continue. He suggests that, although no one explanation can account for the Fermi paradox, perhaps a suite of explanations applicable to different categories of ETI are sufficient to cover the universality of the problem. And this will remain so. This is reminiscent of the “wedges” approach to combatting climate change (Pacala & Solow 2004). It does require that the explanatory wedges, even if they shift their weightings over time due to dynamic factors, must retain their universal coverage of non-contact. Nevertheless, from an instrumental viewpoint, this differs not from the assertion that ETI do not exist as Dobler (2022) points out. Only stable factors such as implausibility of interstellar travel are universal enough to account for the existence of ETI with the persistent lack of evidence. This dovetails neatly into Matloff’s (2022) paper who addresses issues associated with the selfreplicating probes including propulsion for interstellar flight.
{"title":"The prospect of von neumann probes and the implications for the sagan-tipler debate","authors":"A. Ellery","doi":"10.1017/S1473550422000301","DOIUrl":"https://doi.org/10.1017/S1473550422000301","url":null,"abstract":"In the early 1980s, Carl Sagan and Frank Tipler published a series of articles in the pages of the Quarterly Journal of the Royal Astronomical Society on ETI that became a cause celebre at the time. Whilst reading for an MSc in Astronomy at the University of Sussex in the early 1990s, I expressed my interest in SETI as a staunch Saganite (influenced not only by the phenomenal Cosmos TV series, recently re-vamped by Neil de Grasse Tyson, but also by Sagan’s preceding Royal Institution Christmas lecture series) to Professor John Barrow who introduced me to the relevant chapter in the book The Anthropic Cosmological Principle that he co-authored with Frank Tipler (I still recommend the entire book for its visionary scope). I immediately went to source material and was struck by the von Neumann or self-replicating probe concept under discussion (I shall use the latter term to avoid conflation with von Neumann machine which has a well-established meaning in computer engineering). This was my road to Damascus in converting me from ETI believer to skeptic (but by the power of scientific argument rather than any epiphany). Thence, I decided to pursue a PhD in space engineering specialising in space robotics (though my research project was rather more mundane than self-replicating probes). Yet, despite its foundational importance, the Sagan-Tipler debate is almost forgotten today despite the fact that it exposes the root-and-branch of the SETI venture. However, every now and then, there is still the occasional paper on self-replicating probes but they appear to be sidestream to the SETI programme. This special issue seeks to re-focus the self-replicating probe back into the SETI mainstream where it belongs. There are four papers in this special issue. Dobler’s (2022) paper provides the ideal contextual discussion of the Fermi paradox that extant ETI are not here now. He suggests that any optimistic interpretation must accept that there must be a low probability of contact and that this state of affairs shall continue. He suggests that, although no one explanation can account for the Fermi paradox, perhaps a suite of explanations applicable to different categories of ETI are sufficient to cover the universality of the problem. And this will remain so. This is reminiscent of the “wedges” approach to combatting climate change (Pacala & Solow 2004). It does require that the explanatory wedges, even if they shift their weightings over time due to dynamic factors, must retain their universal coverage of non-contact. Nevertheless, from an instrumental viewpoint, this differs not from the assertion that ETI do not exist as Dobler (2022) points out. Only stable factors such as implausibility of interstellar travel are universal enough to account for the existence of ETI with the persistent lack of evidence. This dovetails neatly into Matloff’s (2022) paper who addresses issues associated with the selfreplicating probes including propulsion for interstellar flight.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"197 - 199"},"PeriodicalIF":1.7,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45839036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-08DOI: 10.1017/S1473550422000246
A. Ellery
Abstract The self-replicating machine has high utility by virtue of its universal construction properties and its productive capacity for exponential growth. Their capacity is unrivalled. They can be deployed to the Moon to industrialize it using local in-situ resources in the short term to open up the solar system and thence deployed on interstellar spacecraft to explore the entire Galaxy by exploiting in-situ stellar system resources. Nevertheless, there are significant concerns regarding the inherent safety of self-replicating machines. We consider the general problem of runaway population growth in physical self-replicating machines to prevent the grey goo problem, the number of offspring spawned by self-replicating machines may be controlled at a genetic level. We adopt a biologically-inspired approach based on telomeres, DNA endcaps that are progressively shortened during cellular replication. This acts as a counter that imposes a limit to the number of replication cycles (Hayflick limit). By examining the biological process in detail, we can obtain some insights in implementing similar mechanisms in self-replicating machines. In particular, we find that counting mechanisms are vulnerable to cancerous runaway.
{"title":"Curbing the fruitfulness of self-replicating machines","authors":"A. Ellery","doi":"10.1017/S1473550422000246","DOIUrl":"https://doi.org/10.1017/S1473550422000246","url":null,"abstract":"Abstract The self-replicating machine has high utility by virtue of its universal construction properties and its productive capacity for exponential growth. Their capacity is unrivalled. They can be deployed to the Moon to industrialize it using local in-situ resources in the short term to open up the solar system and thence deployed on interstellar spacecraft to explore the entire Galaxy by exploiting in-situ stellar system resources. Nevertheless, there are significant concerns regarding the inherent safety of self-replicating machines. We consider the general problem of runaway population growth in physical self-replicating machines to prevent the grey goo problem, the number of offspring spawned by self-replicating machines may be controlled at a genetic level. We adopt a biologically-inspired approach based on telomeres, DNA endcaps that are progressively shortened during cellular replication. This acts as a counter that imposes a limit to the number of replication cycles (Hayflick limit). By examining the biological process in detail, we can obtain some insights in implementing similar mechanisms in self-replicating machines. In particular, we find that counting mechanisms are vulnerable to cancerous runaway.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"243 - 259"},"PeriodicalIF":1.7,"publicationDate":"2022-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42962797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-08DOI: 10.1017/S1473550422000234
A. Ellery
Abstract In the early 1980s, the Sagan-Tipler debate raged regarding the interpretation of the Fermi paradox but no clear winner emerged. Sagan favoured the existence of ETI on the basis of the Copernican principle and Tipler favoured the non-existence of ETI on the basis of the Occam's razor principle. Tipler's stance was an expansion of the similar but earlier Hart declaration. However, crucial to the Tipler argument was the role played by self-replicating interstellar robot probes. Any technologically capable species will develop self-replication technology as the most economical means of exploring space and the Galaxy as a whole with minimal investment. There is no evidence of such probes in our solar system including the asteroid belt, ergo, ETI do not exist. This is a powerful and cogent argument. Counter-arguments have been weak including Sagan's sociological explanations. We present a Copernican argument that ETI do not exist – humans are developing self-replication technology today. We are developing the ability to 3D print entire robotic machines from extraterrestrial resources including electric motors and electronics as part of a general in-situ resource utilization (ISRU) capability. We have 3D-printed electric motors which can be potentially leveraged from extraterrestrial material that should be available in every star system. From a similar range of materials, we have identified a means to 3D print neural network circuitry. From our industrial ecology, self-replicating machines and indeed universal constructors are feasible. We describe in some detail how a self-replicating interstellar spacecraft may be constricted from asteroidal resources. We describe technological signatures of the processing of asteroidal material (which is expected to be common to most star systems), and the excess production of certain types of clay and other detritus materials. Self-replication technology is under development and imminent – if humans are pursuing self-replication technology, then by the Copernican principle, so would any technologically savvy species elsewhere. There is no evidence that they have.
{"title":"Self-replicating probes are imminent – implications for SETI","authors":"A. Ellery","doi":"10.1017/S1473550422000234","DOIUrl":"https://doi.org/10.1017/S1473550422000234","url":null,"abstract":"Abstract In the early 1980s, the Sagan-Tipler debate raged regarding the interpretation of the Fermi paradox but no clear winner emerged. Sagan favoured the existence of ETI on the basis of the Copernican principle and Tipler favoured the non-existence of ETI on the basis of the Occam's razor principle. Tipler's stance was an expansion of the similar but earlier Hart declaration. However, crucial to the Tipler argument was the role played by self-replicating interstellar robot probes. Any technologically capable species will develop self-replication technology as the most economical means of exploring space and the Galaxy as a whole with minimal investment. There is no evidence of such probes in our solar system including the asteroid belt, ergo, ETI do not exist. This is a powerful and cogent argument. Counter-arguments have been weak including Sagan's sociological explanations. We present a Copernican argument that ETI do not exist – humans are developing self-replication technology today. We are developing the ability to 3D print entire robotic machines from extraterrestrial resources including electric motors and electronics as part of a general in-situ resource utilization (ISRU) capability. We have 3D-printed electric motors which can be potentially leveraged from extraterrestrial material that should be available in every star system. From a similar range of materials, we have identified a means to 3D print neural network circuitry. From our industrial ecology, self-replicating machines and indeed universal constructors are feasible. We describe in some detail how a self-replicating interstellar spacecraft may be constricted from asteroidal resources. We describe technological signatures of the processing of asteroidal material (which is expected to be common to most star systems), and the excess production of certain types of clay and other detritus materials. Self-replication technology is under development and imminent – if humans are pursuing self-replication technology, then by the Copernican principle, so would any technologically savvy species elsewhere. There is no evidence that they have.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"212 - 242"},"PeriodicalIF":1.7,"publicationDate":"2022-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46789639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-06DOI: 10.1017/S1473550422000180
A. Cassaro, C. Pacelli, M. Baqué, A. Maturilli, U. Boettger, R. Moeller, A. Fujimori, J. D. de Vera, S. Onofri
Abstract The question about the stability of certain biomolecules is directly connected to the life-detection missions aiming to search for past or present life beyond Earth. The extreme conditions experienced on extraterrestrial planet surface (e.g. Mars), characterized by ionizing and non-ionizing radiation, CO2-atmosphere and reactive species, may destroy the hypothetical traces of life. In this context, the study of the biomolecules behaviour after ionizing radiation exposure could provide support for the onboard instrumentation and data interpretation of the life exploration missions on other planets. Here, as a part of STARLIFE campaign, we investigated the effects of gamma rays on two classes of fungal biomolecules–nucleic acids and melanin pigments – considered as promising biosignatures to search for during the ‘in situ life-detection’ missions beyond Earth.
{"title":"Nucleic acids and melanin pigments after exposure to high doses of gamma rays: a biosignature robustness test","authors":"A. Cassaro, C. Pacelli, M. Baqué, A. Maturilli, U. Boettger, R. Moeller, A. Fujimori, J. D. de Vera, S. Onofri","doi":"10.1017/S1473550422000180","DOIUrl":"https://doi.org/10.1017/S1473550422000180","url":null,"abstract":"Abstract The question about the stability of certain biomolecules is directly connected to the life-detection missions aiming to search for past or present life beyond Earth. The extreme conditions experienced on extraterrestrial planet surface (e.g. Mars), characterized by ionizing and non-ionizing radiation, CO2-atmosphere and reactive species, may destroy the hypothetical traces of life. In this context, the study of the biomolecules behaviour after ionizing radiation exposure could provide support for the onboard instrumentation and data interpretation of the life exploration missions on other planets. Here, as a part of STARLIFE campaign, we investigated the effects of gamma rays on two classes of fungal biomolecules–nucleic acids and melanin pigments – considered as promising biosignatures to search for during the ‘in situ life-detection’ missions beyond Earth.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":"21 1","pages":"296 - 307"},"PeriodicalIF":1.7,"publicationDate":"2022-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47133043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-05DOI: 10.1017/s1473550422000192
Alvin L. Smith, Ryan C. Hendrickson
There is increased interest in exploring planetary bodies that have ocean worlds, and planetary protection (PP) practices for spacecraft are important to avoid harmful biological contamination of these sensitive environments. In the autumn of 2018 a diverse set of subject matter experts were assembled to examine the environmental input parameters (e.g. space radiation, Europa surface turnover) and biological input parameters that are referenced by the Europa Clipper project probabilistic risk model, to assess the < 1 × 10−4 probability of contamination requirement derived from NASA Procedural Requirements 8020.12D. A joint NASA–JPL lead workshop entitled, ‘Europa Clipper Planetary Protection Workshop’ was convened on 13–15 November 2018, to validate probability model input values, current Europa Clipper PP requirements and implementation strategy, and identify future PP research topics. The three objectives for the 3 day workshop were: (1) to validate the probability of contamination modelling framework for Europa Clipper PP; (2) to agree on probability of contamination model input values, or on a plan to derive/identify appropriate model inputs and (3) to develop workshop concurrence regarding future PP research plans and their priority. Workshop participants engaged in detailed scientific and engineering discussions focusing on Clipper mission objectives and trajectories, Europan ice shell geophysics and understanding the impact of initial microbial bioburdens and spacecraft cleanliness with all three objectives being successfully completed by the end of the workshop.
{"title":"Protecting ocean worlds: Europa Clipper planetary protection inputs to a probabilistic risk-based approach","authors":"Alvin L. Smith, Ryan C. Hendrickson","doi":"10.1017/s1473550422000192","DOIUrl":"https://doi.org/10.1017/s1473550422000192","url":null,"abstract":"\u0000 There is increased interest in exploring planetary bodies that have ocean worlds, and planetary protection (PP) practices for spacecraft are important to avoid harmful biological contamination of these sensitive environments. In the autumn of 2018 a diverse set of subject matter experts were assembled to examine the environmental input parameters (e.g. space radiation, Europa surface turnover) and biological input parameters that are referenced by the Europa Clipper project probabilistic risk model, to assess the < 1 × 10−4 probability of contamination requirement derived from NASA Procedural Requirements 8020.12D. A joint NASA–JPL lead workshop entitled, ‘Europa Clipper Planetary Protection Workshop’ was convened on 13–15 November 2018, to validate probability model input values, current Europa Clipper PP requirements and implementation strategy, and identify future PP research topics. The three objectives for the 3 day workshop were: (1) to validate the probability of contamination modelling framework for Europa Clipper PP; (2) to agree on probability of contamination model input values, or on a plan to derive/identify appropriate model inputs and (3) to develop workshop concurrence regarding future PP research plans and their priority. Workshop participants engaged in detailed scientific and engineering discussions focusing on Clipper mission objectives and trajectories, Europan ice shell geophysics and understanding the impact of initial microbial bioburdens and spacecraft cleanliness with all three objectives being successfully completed by the end of the workshop.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45079841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-30DOI: 10.1017/s1473550422000052
Medha Prakash, J. Weber, L. E. Rodriguez, R. Sheppard, L. Barge
Carbon reduction is an important process for Earth-like origins of life events and of great interest to the astrobiology community. In this paper, we have collected experimental results, field work and modelling data on CO and CO2 reduction in order to summarize the research that has been carried out particularly in relation to the early Earth and Mars. By having a database of this work, researchers will be able to clearly survey the parameters tested and find knowledge gaps wherein more experimentation would be most beneficial. We focused on reviewing the modelling parameters, field work and laboratory conditions relevant to Mars and the early Earth. We highlight important areas addressed as well as suggest future work needed, including identifying relevant parameters to test in both laboratory and modelling work. We also discuss the utility of organizing research results in such a database in astrobiology.
{"title":"Database on mineral mediated carbon reduction: implications for future research","authors":"Medha Prakash, J. Weber, L. E. Rodriguez, R. Sheppard, L. Barge","doi":"10.1017/s1473550422000052","DOIUrl":"https://doi.org/10.1017/s1473550422000052","url":null,"abstract":"\u0000 Carbon reduction is an important process for Earth-like origins of life events and of great interest to the astrobiology community. In this paper, we have collected experimental results, field work and modelling data on CO and CO2 reduction in order to summarize the research that has been carried out particularly in relation to the early Earth and Mars. By having a database of this work, researchers will be able to clearly survey the parameters tested and find knowledge gaps wherein more experimentation would be most beneficial. We focused on reviewing the modelling parameters, field work and laboratory conditions relevant to Mars and the early Earth. We highlight important areas addressed as well as suggest future work needed, including identifying relevant parameters to test in both laboratory and modelling work. We also discuss the utility of organizing research results in such a database in astrobiology.","PeriodicalId":13879,"journal":{"name":"International Journal of Astrobiology","volume":" ","pages":""},"PeriodicalIF":1.7,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42024714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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