Conventionally, intelligence is seen as a property of individuals. However, it is also known to be a property of collectives. Here, we broaden the idea of intelligence as a collective property and extend it to the planetary scale. We consider the ways in which the appearance of technological intelligence may represent a kind of planetary scale transition, and thus might be seen not as something which happens on a planet but to a planet, much as some models propose the origin of life itself was a planetary phenomenon. Our approach follows the recognition among researchers that the correct scale to understand key aspects of life and its evolution is planetary, as opposed to the more traditional focus on individual species. We explore ways in which the concept may prove useful for three distinct domains: Earth Systems and Exoplanet studies; Anthropocene and Sustainability studies; and the study of Technosignatures and the Search for Extraterrestrial Intelligence (SETI). We argue that explorations of planetary intelligence, defined as the acquisition and application of collective knowledge operating at a planetary scale and integrated into the function of coupled planetary systems, can prove a useful framework for understanding possible paths of the long-term evolution of inhabited planets including future trajectories for life on Earth and predicting features of intelligentially steered planetary evolution on other worlds.

Interplanetary spacecraft are assembled with thousands of parts composed of many diverse materials. Little is known on whether any of the spacecraft materials are biocidal to the typical microbiomes that develop on spacecraft during pre-launch processing. During ongoing experiments to examine the interactive effects of solar UV irradiation, solar heating, ionizing radiation, and vacuum, we observed that bacterial spores of three Bacillus spp. were killed when incubated within small vacuum chambers for 5 days – without exposure to the aforementioned factors. Eight potential spacecraft materials were tested within the vacuum chambers for biocidal activities against spores of B. atrophaeus ATCC 9372, B. pumilus SAFR-032 and B. subtilis 168. All three species were fully inactivated (i.e., no survivors detected) by machined parts manufactured from Delrin®; a thermoplastic polyacetal polymer. Although not tested here, it is known that Delrin can off-gas formaldehyde, and thus, we hypothesize that this volatile organic compound (VOC) was responsible for the biocidal activity of the material. Knowledge of the biocidal nature of routinely used spacecraft materials might offer diverse methods to inactivate deeply embedded or shielded microbiota within spacecraft via the release of biocidal VOCs.

Mars analogue environments are some of the most extreme locations on Earth. Their unique combination of multiples extremes (e.g. high salinity, anoxia and low nutrient availability) make them valuable sources for finding new polyextremophilic microbes, and for exploring the limits of life. Mars, especially at its surface, is still considered to be very hostile to life but it probably possesses geological subsurface niches where the occurrence of (polyextremophilic) life is conceivable. Despite their well-recognized relevance, current knowledge on the capability of (facultative) anaerobic microbes to withstand extraterrestrial/Martian conditions, either as single strains or in communities, is still very sparse. Therefore, space experiments simulating the Martian environmental conditions by using space as a tool for astrobiological research are needed to substantiate the hypotheses of habitability of Mars. Addressing this knowledge gap is one of the main goals of the project MEXEM (Mars EXposed Extremophiles Mixture), where selected model organisms will be subjected to space for a period of 3 months. These experiments will take place on the Exobiology facility (currently under development and implementation), located outside the International Space Station. Such space experiments require a series of preliminary tests and ground data collection for the selected microbial strains. Here, we report on the survivability of Salinisphaera shabanensis and Buttiauxella sp. MASE-IM-9 after exposure to Mars-relevant stress factors (such as desiccation and ultraviolet (UV) radiation under anoxia). Both organisms showed survival after anoxic desiccation for up to 3 months but this could be further extended (nearly doubled) by adding artificial Mars regolith (MGS-1S; 0.5% wt/v) and sucrose (0.1 M). Survival after desiccation was also observed when both organisms were mixed before treatment. Mixing also positively influenced survival after exposure to polychromatic Mars-like UV radiation (200–400 nm) up to 12 kJ m−2, both in suspension and in a desiccated form.

A Von Neumann probe is a self-reproducing intelligent device with interstellar capabilities. A space-faring civilization could conceivably use such constructs to occupy much or all of the Milky Way galaxy and perhaps the entire universe. This paper presents several reasons that a civilization might decide to produce and deploy Von Neumann probes. Physically possible interstellar propulsion methods for such devices are discussed, as is a launch strategy minimizing the duration of an interstellar transfer. Various solar system locations could be investigated to determine whether Von Neumann probes are present in our vicinity.

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.

As soon as samples collected from Mars will be brought back to Earth, the samples will be placed inside a receiving facility to check for the presence of life. There is a large number of approaches that were proposed on the techniques to be used to investigate the presence of life and any biological risk in the returned samples. Another interesting approach was reported by Kminek in which suggestions were provided on how to organize the sample analysis sequence within the facility. Finally, another study suggested a long list of techniques capable of measuring biological signatures based on their general characteristics: global, morphological, mineralogical, organic, molecular and biochemical, isotopic analysis. Despite the effort of the cited studies, there is still the need of a critical approach to make an actual comparison between the techniques, with the aim to find a ranking. In this work, we focused on the construction of a correlation matrix with which to correlate biosignatures to analytical techniques. It is known that a number of techniques can detect biological signatures and, at the same time, each technique can be applied to multiple biological signatures. Using this method, it is possible to summarize all this information to be easily consulted, but also to define in a quantitative way how strong each correlation is.

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.

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.

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.

The iconic Viking Landers that landed on Mars in 1976 demonstrated that the Martian surface is an extreme place, dominated by high UV fluxes and regolith chemistry capable of oxidizing organic molecules. From follow-on missions, we have learned that Mars was much warmer and wetter in its early history, and even some areas of Mars (such as crater lakes, possibly with sustained hydrothermal activity) were habitable places (e.g. Grotzinger et al. (2014). Science (New York, N.Y.) 343; Mangold et al. (2021). Science (New York, N.Y.). However, based on the Viking results we have learnt that the search for life and its remains is challenged by abiotic breakdown and alteration of organic material. In particular, the harsh radiation climate at the Martian surface that directly and indirectly could degrade organics has been held accountable for the lack of organics in the Martian regolith. Recent work simulating wind-driven erosion of basalts under Mars-like conditions has shown that this process, comparable to UV- and ionizing radiation, produces reactive compounds, kills microbes and removes methane from the atmosphere. and thereby could equally jeopardize the success of life-seeking missions to Mars. In this review, we summarize and discuss previous work on the role of physical and chemical mechanisms that affect the persistence of organics, and their consequences for the detection of life and/or its signatures in the Martian regolith and in the atmosphere.

If life ever appeared on Mars and if it did refuge into sub-superficial environments when surface conditions turned too hostile, then it should have been periodically revived from the frozen, dormant state in order to repair the accumulated damage and reset the survival clock to zero for the next dormant phase. Thus, unravelling how long Earth dormant microorganisms can cope with high-LET radiation mimicking long-term irradiation is fundamental to get insights into the long-term resilience of a dormant microbial life in the Martian subsurface over geological timescales that might have taken advantage of periodically clement conditions that allowed the repair of the accumulated DNA damage. The exposure of dried cells of the radioresistant cyanobacterium Chroococcidiopsis sp. CCMEE 029 to 2 kGy of heavy-ion radiation (Fe ions) did not significantly reduce its survival, although DNA damage was accumulated. Upon rehydration, DNA lesions were repaired as suggested by the over-expression of genes involved in the repair of double strand breaks (DSBs), oxidized bases and apurinic-apyrimidinic sites. Indeed, the monitoring of repair genes upon rehydration suggested a key role of the RecF homologous recombination in repairing DSBs. While the fact that out of the eight genes of the BER system, only one was up-regulated, suggested the absence of DNA lesions generally induced by UV radiation. In conclusion, the non-significantly reduced survival of dried Chroococcidiopsis exposed to 2 kGy of Fe-ion radiation further expanded our appreciation of the resilience of a putative dormant life in the Martian subsurface. Moreover, it is also relevant when searching life on Europa and Enceladus where the radiation environment might critically affect the long-term survival of dormant, frozen life forms.