Orbiting

orbiting

Attending Token2049 in Singapore was an illuminating experience for anyone involved in crypto, blockchain, or decentralized finance (DeFi). The conversations, debates, and innovative ideas shared across the event provide insight into the rapidly evolving landscape of the digital economy. At Token2049 Singapore, the DeHealth team had the opportunity to present our cutting-edge blockchain protocol designed to empower users with full control over their medical data. Our decentralized storage solution ensures that users can securely store, access, and manage their health information while maintaining complete ownership and privacy. By utilizing private keys, our technology not only guarantees data confidentiality but also enables seamless integration with eHealth applications. With this protocol, we aim to set a new industry standard for data security and user control, paving the way for widespread adoption in the healthcare sector. In this article, I’ll break down some of the most impactful themes and conclusions from the conference—particularly in regard to the challenges and opportunities facing both public and private markets and the key takeaways that all innovators in this space need to be aware of. The Shift from Public to Private Markets One of the most profound insights from Token2049 was Santiago R Santos’s assertion that “there’s little money in public markets, but plenty in private ones.” It’s a sentiment that reflects the current state of the crypto sector, where early-stage venture capital (VC) investment is robust, but liquidity in public markets is increasingly scarce. This imbalance leads to inflated valuations in early rounds that deflate quickly upon token unlocks and release to the public. The challenge now is to stimulate liquidity in public markets, but the strategies being used—primarily through increasing user activity and total value locked (TVL)—are short-term solutions. As we’ve seen with airdrops, meme coins, and token-based incentives, these mechanisms can initially draw in users, but they fail to establish long-term sustainability. Eventually, projects fall into a “death spiral,” especially when driven by unsustainable APY (annual percentage yield) races. Crypto: The Next Evolution of Financial Instruments There’s a prevailing belief that crypto is pushing the boundaries of financial efficiency at a “supra-national” level. Similar to how developed countries have succeeded by creating transparent systems of property rights that accelerate capital markets, crypto projects are building autonomous systems of digital ownership that expand capital markets for online assets—everything from digital currency to art and intellectual property. These projects are also developing infrastructure that can function independently from state-level risks. Layer-1 (L1) and Layer-2 (L2) networks with varying balances of transparency and privacy are solving different business problems. Simultaneously, bridges, wallets, and decentralized finance (DeFi) infrastructures aim to scale and simplify user experiences while attempting to address the growing market fragmentation. The “East vs. West” Divide in Crypto Projects One fascinating theme at Token2049 was the cultural and operational divide between crypto projects originating in the West versus those in the East. Western projects tend to be tech-heavy but struggle with user adoption, whereas Eastern projects attract massive user bases but often lack cutting-edge technological innovation. As a result, both sides remain somewhat insular, each orbiting within its own ecosystem. One interesting case is the growing trend around Telegram Mini Apps (TMA), which allow the release of meme coins and other high-traffic, low-tech initiatives in the Eastern market. While this strategy brings millions of users, the sustainability of these users—who are often chasing quick financial rewards—is questionable. The Rise of Real-World Assets (RWA) in Crypto Another hot topic at Token2049 was the rise of real-world assets (RWA) in the crypto space. Despite stablecoins being the most practical RWA use case (with 75% of daily transactions on the crypto market linked to them), the potential for tokenizing real-world assets like treasury bills and commercial obligations is massive. Yet, legal and regulatory hurdles remain significant barriers to scaling this segment. Privacy vs. Transparency: An Ongoing Debate A major point of contention at the conference was the balance between privacy and transparency in blockchain. Representatives from projects like Arbitrum, Solana, and Partisia agreed that it’s nearly impossible to fully combine both. You’re either private and non-transparent (which introduces regulatory risk, as we’ve seen with Tornado Cash) or transparent and, therefore, vulnerable to regulation targeting project founders. The Growing Fragmentation of Crypto Infrastructure The rapid growth of L1 and L2 networks has led to significant fragmentation, which has become a critical challenge for the sector. Liquidity is being split across multiple platforms, making it difficult for users to navigate different networks without complex bridges, wallets, and protocols. This not only makes the user experience more cumbersome but also introduces additional risks—particularly around security and liquidity. The DeFi Renaissance DeFi projects were some of the most discussed at Token2049. Despite challenges around TVL (Total Value Locked) and yield generation, DeFi remains one of the few segments within crypto where real business models, internal economies, and decentralization are actively developing. However, these projects are also starting to position themselves more like centralized finance (CeFi) entities to avoid regulatory scrutiny, which could eventually force many DeFi protocols to adopt more traditional financial obligations. The Future of Ethereum and Solana Lastly, much attention was paid to the future of Ethereum and Solana. Ethereum’s growth continues, but liquidity and fees are being siphoned off to Layer 2s, which are now essential to the network’s future. Solana, on the other hand, is advancing rapidly, attracting both mass users and corporate players like PayPal. Both ecosystems have their strengths—Ethereum’s being its established user base and developer support, while Solana is faster, cheaper, and has the potential to scale more broadly. How these platforms evolve will play a key role in shaping the broader crypto landscape over the next few years. As we continue to monitor the development of crypto, DeFi, and tokenization, the key themes from Token2049 Singapore highlight the necessity for both innovation and sustainability. Crypto is no longer just about creating technology for the sake of technology. The focus is shifting toward building practical, scalable systems that can integrate into the global financial ecosystem, all while addressing the unique challenges of privacy, transparency, and regulation. It’s an exciting time to be at the forefront of this transformation! Attending Token2049 in Singapore was an illuminating experience for anyone involved in crypto, blockchain, or decentralized finance (DeFi). The conversations, debates, and innovative ideas shared across the event provide insight into the rapidly evolving landscape of the digital economy. At Token2049 Singapore, the DeHealth team had the opportunity to present our cutting-edge blockchain protocol designed to empower users with full control over their medical data. Our decentralized storage solution ensures that users can securely store, access, and manage their health information while maintaining complete ownership and privacy. By utilizing private keys, our technology not only guarantees data confidentiality but also enables seamless integration with eHealth applications. With this protocol, we aim to set a new industry standard for data security and user control, paving the way for widespread adoption in the healthcare sector. DeHealth In this article, I’ll break down some of the most impactful themes and conclusions from the conference—particularly in regard to the challenges and opportunities facing both public and private markets and the key takeaways that all innovators in this space need to be aware of. The Shift from Public to Private Markets One of the most profound insights from Token2049 was Santiago R Santos’s assertion that “there’s little money in public markets, but plenty in private ones.” It’s a sentiment that reflects the current state of the crypto sector, where early-stage venture capital (VC) investment is robust, but liquidity in public markets is increasingly scarce. This imbalance leads to inflated valuations in early rounds that deflate quickly upon token unlocks and release to the public. The challenge now is to stimulate liquidity in public markets, but the strategies being used—primarily through increasing user activity and total value locked (TVL)—are short-term solutions. As we’ve seen with airdrops, meme coins, and token-based incentives, these mechanisms can initially draw in users, but they fail to establish long-term sustainability. Eventually, projects fall into a “death spiral,” especially when driven by unsustainable APY (annual percentage yield) races. Crypto: The Next Evolution of Financial Instruments There’s a prevailing belief that crypto is pushing the boundaries of financial efficiency at a “supra-national” level. Similar to how developed countries have succeeded by creating transparent systems of property rights that accelerate capital markets, crypto projects are building autonomous systems of digital ownership that expand capital markets for online assets—everything from digital currency to art and intellectual property. These projects are also developing infrastructure that can function independently from state-level risks. Layer-1 (L1) and Layer-2 (L2) networks with varying balances of transparency and privacy are solving different business problems. Simultaneously, bridges, wallets, and decentralized finance (DeFi) infrastructures aim to scale and simplify user experiences while attempting to address the growing market fragmentation. The “East vs. West” Divide in Crypto Projects One fascinating theme at Token2049 was the cultural and operational divide between crypto projects originating in the West versus those in the East. Western projects tend to be tech-heavy but struggle with user adoption, whereas Eastern projects attract massive user bases but often lack cutting-edge technological innovation. As a result, both sides remain somewhat insular, each orbiting within its own ecosystem. One interesting case is the growing trend around Telegram Mini Apps (TMA), which allow the release of meme coins and other high-traffic, low-tech initiatives in the Eastern market. While this strategy brings millions of users, the sustainability of these users—who are often chasing quick financial rewards—is questionable. The Rise of Real-World Assets (RWA) in Crypto Another hot topic at Token2049 was the rise of real-world assets (RWA) in the crypto space. Despite stablecoins being the most practical RWA use case (with 75% of daily transactions on the crypto market linked to them), the potential for tokenizing real-world assets like treasury bills and commercial obligations is massive. Yet, legal and regulatory hurdles remain significant barriers to scaling this segment. Privacy vs. Transparency: An Ongoing Debate A major point of contention at the conference was the balance between privacy and transparency in blockchain. Representatives from projects like Arbitrum, Solana, and Partisia agreed that it’s nearly impossible to fully combine both. You’re either private and non-transparent (which introduces regulatory risk, as we’ve seen with Tornado Cash) or transparent and, therefore, vulnerable to regulation targeting project founders. The Growing Fragmentation of Crypto Infrastructure The rapid growth of L1 and L2 networks has led to significant fragmentation, which has become a critical challenge for the sector. Liquidity is being split across multiple platforms, making it difficult for users to navigate different networks without complex bridges, wallets, and protocols. This not only makes the user experience more cumbersome but also introduces additional risks—particularly around security and liquidity. The DeFi Renaissance DeFi projects were some of the most discussed at Token2049. Despite challenges around TVL (Total Value Locked) and yield generation, DeFi remains one of the few segments within crypto where real business models, internal economies, and decentralization are actively developing. However, these projects are also starting to position themselves more like centralized finance (CeFi) entities to avoid regulatory scrutiny, which could eventually force many DeFi protocols to adopt more traditional financial obligations. The Future of Ethereum and Solana Lastly, much attention was paid to the future of Ethereum and Solana. Ethereum’s growth continues, but liquidity and fees are being siphoned off to Layer 2s, which are now essential to the network’s future. Solana, on the other hand, is advancing rapidly, attracting both mass users and corporate players like PayPal. Both ecosystems have their strengths—Ethereum’s being its established user base and developer support, while Solana is faster, cheaper, and has the potential to scale more broadly. How these platforms evolve will play a key role in shaping the broader crypto landscape over the next few years. As we continue to monitor the development of crypto, DeFi, and tokenization, the key themes from Token2049 Singapore highlight the necessity for both innovation and sustainability. Crypto is no longer just about creating technology for the sake of technology. The focus is shifting toward building practical, scalable systems that can integrate into the global financial ecosystem, all while addressing the unique challenges of privacy, transparency, and regulation. It’s an exciting time to be at the forefront of this transformation!

Token2049 Singapore: Key Takeaways from the Future of Crypto and DeFi

Table of Links Abstract and 1. Introduction 2. Methods 2.1. Modeling Panspermia and Terraformation 2.2. Identifying the Presence of Terraformed Planets and 2.3. Software and Availability 3. Results 3.1. Panspermia can increase the correlation between planets’ compositions and positions 3.2. Likely terraformed planets can be identified from clustering 4. Summary and Discussion 5. Acknowledgements and References APPENDIX A. Appendix 2.1. Modeling Panspermia and Terraformation We created an agent-based model to simulate life[2] spreading between planets orbiting different host stars. The model is initialized with 1000 planets (1 of which is terraformed/panspermia-capable), fixed in a frame of reference, and uniformly randomly distributed in a continuous 3D volume. All planets are assumed to be in different star systems (i.e., we assume one planet per star). “Planets” have compositions representing the observable characteristics of the planet, and “life” agents have compositions representing the observable characteristics of the planet which the life originates from. During simulation, terraformed planets [3] emit life towards a target non-terraformed planet at a constant velocity [4]. The target planets are selected based on proximity in position and in composition (see Sec. 2.1.4). When life arrives at a planet, the planet’s composition is modified (terraformed) based on both the initial composition of the planet and the composition of the incoming life. Life originating from that terraformed planet will then reflect its new composition. We assume that the time required for terraformation is negligible compared to the time required to travel between planets. Terraformed planets emit life at a fixed rate, provided suitable target planets exist (see Sec. 2.1.4). The simulation ends when all planets are terraformed, or no suitable target planets remain (Fig. 1B). 2.1.2. Compositions and Terraformation Both “life” and “planets” have compositions represented by vectors of 10 real numbers (each element ∈ [0, 1]). In our model, these compositions are abstractions, used as a means to compare the compatibility of any given life and planet. While we might in the abstract think of one vector representing the observable characteristics of a planet, this same vector would not represent the same observable characteristics of life compatible with that planet. For life, it instead represents the kind of planetary observable characteristics which are compatible with that life. For example, perhaps a planet’s composition vector V corresponds to an atmosphere composed of 95% CO2 and 5% N2. The same composition vector V in the context of life is used to refer to a kind of life which could be compatible with a planet with an atmospheric composition of 95% CO2 and 5% N2. This does not mean that life on such a planet is literally composed of 95% CO2 and 5% N2. This captures the idea that if a life and a planet have identical composition vectors, then that life will surely be able to terraform the planet[5]. Correspondingly, a life’s composition is identical to the planet from which it emits. Depending on the simulation parameters, initial compositions of each planet are randomly drawn from a uniform distribution. This is a loose approximation of the unknowns surrounding the distribution of diversity of planets between planetary systems (Tasker et al. 2020; Pacetti et al. 2022). Planet compositions are modified by the process of terraformation, where a mixing function determines how to generate the terraformed composition based on the non-terraformed planet composition and the incoming life’s composition. We apply a mixing function inspired by horizontal gene transfer, but other mixing functions could also be used. The most important feature we aim to capture is the bi-directional feedback between the terraforming life, and the terraformed planet—such that future life emitted from the terraformed planet will inherit the post-terraformation characteristics of that planet. We keep n = 1 randomly chosen element from the planet’s pre-terraformed composition, and the rest of the terraformed composition is inherited from the terraforming life (Fig. 1C). 2.1.3. Model Stepping 2.1.4. Target Planet Selection The destination selection aims to balance the need of identifying a target planet that is both compositionally similar, and physically near, the parent planet. This is based on the assumption that life directing panspermia would want to minimize travel time and terraformation energy costs. In the context of lithopanspermia, this could be interpreted as an assumption that beyond a certain positional distance capture becomes vanishingly unlikely, and beyond a certain compositional distance compatibility becomes vanishingly unlikely. Authors:
(1) Harrison B. Smith, Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan, and Blue Marble Space Institute of Science, Seattle, Washington, USA (hbs@elsi.jp);
(2) Lana Sinapayen, Sony Computer Science Laboratories, Kyoto, Japan and National Institute for Basic Biology, Okazaki, Japan (lana.sinapayen@gmail.com). This paper is available on arxiv under CC BY-NC-ND 4.0 Deed license. [2] In this work, we use life specifically to refer to an agent (used strictly in the “entity” sense of the word agent) traveling from a parent terraformed planet to a target non-terraformed planet, and whose arrival at the target planet triggers terraformation. [3] We specifically avoid saying living planets, because our methodology cannot distinguish between living planets incapable of panspermia and non-living planets. [4] This approach is most similar to directed panspermia by intelligent life, but could also be envisioned as undirected lithopanspermia, where we refrain from burdening the simulations with agents that won’t ever be able to interact with planets under the rules of our model. [5] This is an extreme example where technically life wouldn’t even need to terraform the planet, because it implies that the planet’s observable characteristics already perfectly match the planet from where the life originated. Table of Links Abstract and 1. Introduction Abstract and 1. Introduction 2. Methods 2.1. Modeling Panspermia and Terraformation 2.1. Modeling Panspermia and Terraformation 2.2. Identifying the Presence of Terraformed Planets and 2.3. Software and Availability 2.2. Identifying the Presence of Terraformed Planets and 2.3. Software and Availability 3. Results 3.1. Panspermia can increase the correlation between planets’ compositions and positions 3.1. Panspermia can increase the correlation between planets’ compositions and positions 3.2. Likely terraformed planets can be identified from clustering 3.2. Likely terraformed planets can be identified from clustering 4. Summary and Discussion 4. Summary and Discussion 5. Acknowledgements and References 5. Acknowledgements and References APPENDIX APPENDIX A. Appendix A. Appendix 2.1. Modeling Panspermia and Terraformation We created an agent-based model to simulate life[2] spreading between planets orbiting different host stars. The model is initialized with 1000 planets (1 of which is terraformed/panspermia-capable), fixed in a frame of reference, and uniformly randomly distributed in a continuous 3D volume. All planets are assumed to be in different star systems (i.e., we assume one planet per star). “Planets” have compositions representing the observable characteristics of the planet, and “life” agents have compositions representing the observable characteristics of the planet which the life originates from. During simulation, terraformed planets [3] emit life towards a target non-terraformed planet at a constant velocity [4]. The target planets are selected based on proximity in position and in composition (see Sec. 2.1.4). When life arrives at a planet, the planet’s composition is modified (terraformed) based on both the initial composition of the planet and the composition of the incoming life. Life originating from that terraformed planet will then reflect its new composition. We assume that the time required for terraformation is negligible compared to the time required to travel between planets. Terraformed planets emit life at a fixed rate, provided suitable target planets exist (see Sec. 2.1.4). The simulation ends when all planets are terraformed, or no suitable target planets remain (Fig. 1B). 2.1.2. Compositions and Terraformation 2.1.2. Compositions and Terraformation Both “life” and “planets” have compositions represented by vectors of 10 real numbers (each element ∈ [0, 1]). In our model, these compositions are abstractions, used as a means to compare the compatibility of any given life and planet. While we might in the abstract think of one vector representing the observable characteristics of a planet, this same vector would not represent the same observable characteristics of life compatible with that planet. For life, it instead represents the kind of planetary observable characteristics which are compatible with that life. For example, perhaps a planet’s composition vector V corresponds to an atmosphere composed of 95% CO2 and 5% N2. The same composition vector V in the context of life is used to refer to a kind of life which could be compatible with a planet with an atmospheric composition of 95% CO2 and 5% N2. This does not mean that life on such a planet is literally composed of 95% CO2 and 5% N2. This captures the idea that if a life and a planet have identical composition vectors, then that life will surely be able to terraform the planet[5]. Correspondingly, a life’s composition is identical to the planet from which it emits. Depending on the simulation parameters, initial compositions of each planet are randomly drawn from a uniform distribution. This is a loose approximation of the unknowns surrounding the distribution of diversity of planets between planetary systems (Tasker et al. 2020; Pacetti et al. 2022). Planet compositions are modified by the process of terraformation, where a mixing function determines how to generate the terraformed composition based on the non-terraformed planet composition and the incoming life’s composition. We apply a mixing function inspired by horizontal gene transfer, but other mixing functions could also be used. The most important feature we aim to capture is the bi-directional feedback between the terraforming life, and the terraformed planet—such that future life emitted from the terraformed planet will inherit the post-terraformation characteristics of that planet. We keep n = 1 randomly chosen element from the planet’s pre-terraformed composition, and the rest of the terraformed composition is inherited from the terraforming life (Fig. 1C). 2.1.3. Model Stepping 2.1.3. Model Stepping 2.1.4. Target Planet Selection 2.1.4. Target Planet Selection The destination selection aims to balance the need of identifying a target planet that is both compositionally similar, and physically near, the parent planet. This is based on the assumption that life directing panspermia would want to minimize travel time and terraformation energy costs. In the context of lithopanspermia, this could be interpreted as an assumption that beyond a certain positional distance capture becomes vanishingly unlikely, and beyond a certain compositional distance compatibility becomes vanishingly unlikely. Authors: (1) Harrison B. Smith, Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan, and Blue Marble Space Institute of Science, Seattle, Washington, USA (hbs@elsi.jp); (2) Lana Sinapayen, Sony Computer Science Laboratories, Kyoto, Japan and National Institute for Basic Biology, Okazaki, Japan (lana.sinapayen@gmail.com). Authors: Authors: (1) Harrison B. Smith, Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan, and Blue Marble Space Institute of Science, Seattle, Washington, USA ( hbs@elsi.jp ); hbs@elsi.jp (2) Lana Sinapayen, Sony Computer Science Laboratories, Kyoto, Japan and National Institute for Basic Biology, Okazaki, Japan ( lana.sinapayen@gmail.com ). lana.sinapayen@gmail.com This paper is available on arxiv under CC BY-NC-ND 4.0 Deed license. This paper is available on arxiv under CC BY-NC-ND 4.0 Deed license. available on arxiv [2] In this work, we use life specifically to refer to an agent (used strictly in the “entity” sense of the word agent) traveling from a parent terraformed planet to a target non-terraformed planet, and whose arrival at the target planet triggers terraformation. [3] We specifically avoid saying living planets, because our methodology cannot distinguish between living planets incapable of panspermia and non-living planets. [4] This approach is most similar to directed panspermia by intelligent life, but could also be envisioned as undirected lithopanspermia, where we refrain from burdening the simulations with agents that won’t ever be able to interact with planets under the rules of our model. [5] This is an extreme example where technically life wouldn’t even need to terraform the planet, because it implies that the planet’s observable characteristics already perfectly match the planet from where the life originated.

A Biosignature Based on Modeling Panspermia and Terraformation: Modeling

Thermodynamic Limits Around M-dwarf Stars: Acknowledgements

Thermodynamic Limits on Oxygenic Photosynthesis Around M-dwarf Stars: Abstract and Introduction

(1) Samir Chitnavis, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK;
(2) Thomas J. Haworth, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK;
(3) Edward Gillen, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK;
(4) Conrad W. Mullineaux, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK;
(5) Christopher D. P. Duffy, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK (Email: c.duffy@qmul.ac.uk). Table of Links Abstract and Introduction
2 Methodology
2.1 Local spectral irradiance as a function of stellar temperature
2.2 Thermodynamic model of an oxygenic light-harvesting system
2.3 Lattice model of an oxygenic light-harvesting system
3 Results
3.1 Orbital distances and incident spectral fluxes
3.2 Thermodynamic antenna model: Increasing antenna size in limited PAR
3.3 Lattice antenna model: Increasing the size of a “flat” antenna in limited PAR
3.4 Lattice antenna model: Improving antenna efficiency with an energetic ’funnel’
4 Discussion
Acknowledgements, Author Contribution Statement, Authors disclosure statement and References 4 Discussion The results of our generalized antenna models suggest that the oxygenic photosynthesis is likely feasible on exo-planets orbiting low mass M-dwarf stars, though there are some restrictions. A light-harvesting system similar to PSII of vascular plants (but with a larger antenna) would be severely entropy-limited even before we factor in local limitations like water scarcity, atmospheric attenuation of light, etc. However, this reflects the fact that plants are evolved to deal with highly variable irradiance [Vialet-Chabrand et al., 2017, Li et al., 2021] rather than constant low light. One of the major risks to plants is actually excessive illumination which can cause oxidative damage to PSII, a metabolically costly phenomenon known as photoinhibition, and one that should be familiar to anyone who has suddenly moved a houseplant into full sun. To mitigate photoinhibition [Aro et al., 1993], plants possess regulatory mechanisms that suppress photon absorption and down-regulate the antenna [Ruban, 2016, Ruban and Wilson, 2021]. Therefore it is unsurprising that such a system does not perform well in severely PAR-depleted light. However, by introducing an energetic gradient to the antenna (the energy funnel) we were able to significantly improve antenna efficiency and electron output. Of the branched and hexagonal antenna topologies the former performs better, able to match the performance of the latter but with fewer LHC subunits and a shallower energetic gradient. Fewer LHC subunits is perhaps the most important factor as it is directly related to the metabolic “cost” of the antenna. Of course, there are countless other modifications that could be made to the antenna. For example, one could increase pigment density which would increase the overall cross-section of each LHC and enhance inter-pigment energy transfer. The pigment concentration in LHCII is already very high, approximately 1 mol dm−3 , and the protein scaffold enforces highly specific inter-pigment distances and relative orientations to avoid dissipative processes such as concentration quenching [Liu et al., 2004]. However, one could imagine an adaptation similar to the chlorosome antenna of green sulphur bacteria [Oostergetel et al., 2010]. This structure is a solid aggregate of ∼ 300, 000 BChls encapsulated in a membrane sheath, effectively the densest pigment packing possible, and it facilitates (anoxygenic) photosynthesis in extremely low illumination. It should be noted however that such as structure is is a significant metabolic investment and one that is not seen in any large multi-cellular organism. Alternatively, one could replace Chl a and b with pigments with larger intrinsic cross-sections and/or absorption widths, which would increase the rate of photon absorption, γi . Since intermolecular energy transfer depends on the oscillator strengths and spectral overlap of the pigments involved, this may also enhance the intrinsic transfer rates, (Ki,j ) −1 . Still, the branched, funnel antenna strategy is a plausible one because it explicitly addresses the fundamental thermodynamic limits inherent in light-harvesting. More importantly, such an antenna actually exists on in Earth in the form of the phycobilisome of oxygenic cyanobacteria [Saer and Blankenship, 2017]. Like our model, the phycobilisome is modular and can adapt to changes in irradiance. Kolodny et al. [2022] recently showed that cyanobacteria in deep water, where light is very blue-shifted, will lenghten their phycobilisome rods by adding more terminal PE subunits and will increase overall antenna efficiency, ϕF , by tuning pigment content (and possibly density). The most important result, however, is the recent work of Battistuzzi et al. [2023] who showed that cyanobacteria could comfortably adapt to the the light typical of M-dwarf stars. Moreover, they used a sophisticated starlight simulator setup which models atmospheric attenuation of light, meaning their cyanobacteria were likely subject to ever scanter illumination than we consider here. Interestingly, they also considered pure “far red” (700−800 nm) illumination and found that this retarded growth rate relative to the M-dwarf light, implying that, as in our model, the organism was adapting its antenna to intercept more photons in the depleted PAR region.It should be noted that they also considered on the red-adapted strains described in the introduction that fared equally well in M-dwarf and far red light. Strictly, both our modelling and the experimental work of Kolodny et al. [2022]. concerns the acclimation of an existing antenna to an unusual lightenvironment rather than the ground-up evolution of an antenna structure specifically optimized to it. Nevertheless, Kolodny’s work demonstrates that oxygenic photosynthesis is, in principle, possible around very low mass stars and our findings indicate that the key consideration is overcoming a fundamental entropic barrier to light-harvesting. This paper is available on arxiv under CC 4.0 license. (1) Samir Chitnavis, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK; (2) Thomas J. Haworth, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK; (3) Edward Gillen, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK; (4) Conrad W. Mullineaux, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK; (5) Christopher D. P. Duffy, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK (Email: c.duffy@qmul.ac.uk). (1) Samir Chitnavis, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK; (2) Thomas J. Haworth, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK; (3) Edward Gillen, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK; (4) Conrad W. Mullineaux, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK; (5) Christopher D. P. Duffy, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK (Email: c.duffy@qmul.ac.uk). Table of Links Abstract and Introduction 2 Methodology 2.1 Local spectral irradiance as a function of stellar temperature 2.2 Thermodynamic model of an oxygenic light-harvesting system 2.3 Lattice model of an oxygenic light-harvesting system 3 Results 3.1 Orbital distances and incident spectral fluxes 3.2 Thermodynamic antenna model: Increasing antenna size in limited PAR 3.3 Lattice antenna model: Increasing the size of a “flat” antenna in limited PAR 3.4 Lattice antenna model: Improving antenna efficiency with an energetic ’funnel’ 4 Discussion Acknowledgements, Author Contribution Statement, Authors disclosure statement and References Abstract and Introduction Abstract and Introduction 2 Methodology 2.1 Local spectral irradiance as a function of stellar temperature 2.1 Local spectral irradiance as a function of stellar temperature 2.2 Thermodynamic model of an oxygenic light-harvesting system 2.2 Thermodynamic model of an oxygenic light-harvesting system 2.3 Lattice model of an oxygenic light-harvesting system 2.3 Lattice model of an oxygenic light-harvesting system 3 Results 3.1 Orbital distances and incident spectral fluxes 3.1 Orbital distances and incident spectral fluxes 3.2 Thermodynamic antenna model: Increasing antenna size in limited PAR 3.2 Thermodynamic antenna model: Increasing antenna size in limited PAR 3.3 Lattice antenna model: Increasing the size of a “flat” antenna in limited PAR 3.3 Lattice antenna model: Increasing the size of a “flat” antenna in limited PAR 3.4 Lattice antenna model: Improving antenna efficiency with an energetic ’funnel’ 3.4 Lattice antenna model: Improving antenna efficiency with an energetic ’funnel’ 4 Discussion 4 Discussion Acknowledgements, Author Contribution Statement, Authors disclosure statement and References Acknowledgements, Author Contribution Statement, Authors disclosure statement and References 4 Discussion The results of our generalized antenna models suggest that the oxygenic photosynthesis is likely feasible on exo-planets orbiting low mass M-dwarf stars, though there are some restrictions. A light-harvesting system similar to PSII of vascular plants (but with a larger antenna) would be severely entropy-limited even before we factor in local limitations like water scarcity, atmospheric attenuation of light, etc. However, this reflects the fact that plants are evolved to deal with highly variable irradiance [Vialet-Chabrand et al., 2017, Li et al., 2021] rather than constant low light. One of the major risks to plants is actually excessive illumination which can cause oxidative damage to PSII, a metabolically costly phenomenon known as photoinhibition, and one that should be familiar to anyone who has suddenly moved a houseplant into full sun. To mitigate photoinhibition [Aro et al., 1993], plants possess regulatory mechanisms that suppress photon absorption and down-regulate the antenna [Ruban, 2016, Ruban and Wilson, 2021]. Therefore it is unsurprising that such a system does not perform well in severely PAR-depleted light. However, by introducing an energetic gradient to the antenna (the energy funnel) we were able to significantly improve antenna efficiency and electron output. Of the branched and hexagonal antenna topologies the former performs better, able to match the performance of the latter but with fewer LHC subunits and a shallower energetic gradient. Fewer LHC subunits is perhaps the most important factor as it is directly related to the metabolic “cost” of the antenna. Of course, there are countless other modifications that could be made to the antenna. For example, one could increase pigment density which would increase the overall cross-section of each LHC and enhance inter-pigment energy transfer. The pigment concentration in LHCII is already very high, approximately 1 mol dm−3 , and the protein scaffold enforces highly specific inter-pigment distances and relative orientations to avoid dissipative processes such as concentration quenching [Liu et al., 2004]. However, one could imagine an adaptation similar to the chlorosome antenna of green sulphur bacteria [Oostergetel et al., 2010]. This structure is a solid aggregate of ∼ 300, 000 BChls encapsulated in a membrane sheath, effectively the densest pigment packing possible, and it facilitates (anoxygenic) photosynthesis in extremely low illumination. It should be noted however that such as structure is is a significant metabolic investment and one that is not seen in any large multi-cellular organism. Alternatively, one could replace Chl a and b with pigments with larger intrinsic cross-sections and/or absorption widths, which would increase the rate of photon absorption, γi . Since intermolecular energy transfer depends on the oscillator strengths and spectral overlap of the pigments involved, this may also enhance the intrinsic transfer rates, (Ki,j ) −1 . Still, the branched, funnel antenna strategy is a plausible one because it explicitly addresses the fundamental thermodynamic limits inherent in light-harvesting. More importantly, such an antenna actually exists on in Earth in the form of the phycobilisome of oxygenic cyanobacteria [Saer and Blankenship, 2017]. Like our model, the phycobilisome is modular and can adapt to changes in irradiance. Kolodny et al. [2022] recently showed that cyanobacteria in deep water, where light is very blue-shifted, will lenghten their phycobilisome rods by adding more terminal PE subunits and will increase overall antenna efficiency, ϕF , by tuning pigment content (and possibly density). The most important result, however, is the recent work of Battistuzzi et al. [2023] who showed that cyanobacteria could comfortably adapt to the the light typical of M-dwarf stars. Moreover, they used a sophisticated starlight simulator setup which models atmospheric attenuation of light, meaning their cyanobacteria were likely subject to ever scanter illumination than we consider here. Interestingly, they also considered pure “far red” (700−800 nm) illumination and found that this retarded growth rate relative to the M-dwarf light, implying that, as in our model, the organism was adapting its antenna to intercept more photons in the depleted PAR region.It should be noted that they also considered on the red-adapted strains described in the introduction that fared equally well in M-dwarf and far red light. Strictly, both our modelling and the experimental work of Kolodny et al. [2022]. concerns the acclimation of an existing antenna to an unusual lightenvironment rather than the ground-up evolution of an antenna structure specifically optimized to it. Nevertheless, Kolodny’s work demonstrates that oxygenic photosynthesis is, in principle, possible around very low mass stars and our findings indicate that the key consideration is overcoming a fundamental entropic barrier to light-harvesting. This paper is available on arxiv under CC 4.0 license. This paper is available on arxiv under CC 4.0 license. available on arxiv

Thermodynamic Limits Around M-dwarf Stars: Discussion 

Transcendence Volume I, Book 1: Introduction

Discussing the Impact of Our Exoplanet Study: How This Impacts Everything

This paper is available on arxiv under CC 4.0 license. Authors: (1) Andrew Ridden-Harper, Department of Astronomy and Carl Sagan Institute, Cornell University & Las Cumbres Observatory; (2) Stevanus K. Nugroho, Astrobiology Center & Japan & National Astronomical Observatory of Japan; (3) Laura Flagg, Department of Astronomy and Carl Sagan Institute, Cornell University; (4) Ray Jayawardhana, Department of Astronomy, Cornell University; (5) Jake D. Turner, Department of Astronomy and Carl Sagan Institute, Cornell University & NHFP Sagan Fellow; (6) Ernst de Mooij, Astrophysics Research Centre, School of Mathematics and Physics & Queen’s University Belfast; (7) Ryan MacDonald, Department of Astronomy and Carl Sagan Institute; (8) Emily Deibert, David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto & Gemini Observatory, NSF’s NOIRLab; (9) Motohide Tamura, Dunlap Institute for Astronomy & Astrophysics, University of Toronto (10) Takayuki Kotani, Department of Astronomy, Graduate School of Science, The University of Tokyo, Astrobiology Center & National Astronomical Observatory of Japan; (11) Teruyuki Hirano, Astrobiology Center, National Astronomical Observatory of Japan & Department of Astronomical Science, The Graduate University for Advanced Studies; (12) Masayuki Kuzuhara, Las Cumbres Observatory & Astrobiology Center; (13) Masashi Omiya, Las Cumbres Observatory & Astrobiology Center; (14) Nobuhiko Kusakabe, Las Cumbres Observatory & Astrobiology Center. Table of Links Abstract & Introduction Observation Data Reduction and Processing Model Spectra Cross-Correlation Method Results Clouds and Hazes Implications for JWST Conclusion and Acknowledgement Appendix & References ABSTRACT Terrestrial exoplanets orbiting M-dwarf stars are promising targets for transmission spectroscopy with existing or near-future instrumentation. The atmospheric composition of such rocky planets remains an open question, especially given the high X-ray and ultraviolet flux from their host M dwarfs that can drive atmospheric escape. The 1.3 R⊕ exoplanet GJ 486b (Teq ∼ 700 K), orbiting an M3.5 star, is expected to have one of the strongest transmission spectroscopy signals among known terrestrial exoplanets. We observed three transits of GJ 486b using three different high-resolution spectrographs: IRD on Subaru, IGRINS on Gemini-South, and SPIRou on the Canada-France-Hawai’i Telescope. We searched for atmospheric absorption from a wide variety of molecular species via the cross-correlation method, but did not detect any robust atmospheric signals. Nevertheless, our observations are sufficiently sensitive to rule out several clear atmospheric scenarios via injection and recovery tests, and extend comparative exoplanetology into the terrestrial regime. Our results suggest that GJ 486b does not possess a clear H2/He-dominated atmosphere, nor a clear 100% water-vapor atmosphere. Other secondary atmospheres with high mean molecular weights or H2/He-dominated atmospheres with clouds remain possible. Our findings provide further evidence suggesting that terrestrial planets orbiting M-dwarf stars may experience significant atmospheric loss. : Exoplanet atmospheres (487) — Planetary atmospheres (1244) — Exoplanets (498) — Exoplanet atmospheric composition (2021) Keywords 1. INTRODUCTION Exoplanets that transit M-dwarf stars produce relatively deep transits due to their high planet-star radius ratios. Consequently, it may be possible to detect biosignatures in the atmospheres of terrestrial exoplanets with existing or near-future instrumentation (e.g., Snellen et al. 2013; Wunderlich et al. 2019). However, the long-term habitability of such planets depends crucially on the stability of their atmospheres, which are subject to high X-ray + extreme UV (XUV) emissions during the pre-main-sequence phase of their M-dwarf hosts (e.g., Shkolnik & Barman 2014; Peacock et al. 2020) as well as flare events (e.g., Neves Ribeiro do Amaral et al. 2022) that can drive atmospheric escape (e.g., Vidal-Madjar et al. 2003; Bourrier et al. 2017a; Airapetian et al. 2017). Terrestrial exoplanets are expected to exhibit a rich diversity in atmospheric compositions. Exoplanets with Rp < 1.4 R⊕ and orbital periods < 100 days likely form as gas-rich sub-Neptunes that subsequently lose their primordial atmospheres due to photoevaporation (Rogers & Owen 2021). The amount of primordial atmosphere retained depends on several factors, such as their host star’s spectral energy distribution and activity levels, along with how much gas they accrete during formation (e.g., Bolmont et al. 2017; Owen et al. 2020). Should the primordial hydrogen-dominated atmosphere be lost, a secondary atmosphere may be retained. The composition of secondary atmospheres depends on a variety of processes, including interior outgassing, impact delivery, erosion, atmosphere-surface exchange, weathering, and volatile sequestration (e.g., Rogers et al. 2011). Driven by these processes, hot terrestrial planets (T & 1500 K) are predicted to have atmospheres containing atoms and ions, such as Na or Ca+, produced by surface vaporization (Schaefer & Fegley 2009) — though other hydrogen- or nitrogen-rich compositions are possible (Miguel 2019). However, cooler terrestrial planets are likely rich in molecular species, such as H2O, CO2, CO, O2, C2H2, and CH4 (e.g., Ramirez & Kaltenegger 2014; Madhusudhan et al. 2016; Kite & Schaefer 2021). Given the range of theoretical possibilities, observational constraints on the composition of terrestrial exoplanet atmospheres are crucially needed. While there have been several attempts to detect the atmospheres of a few terrestrial exoplanets, these have only yielded constraints from nondetections. For example, 55 Cancri e is a 1.9 R⊕ exoplanet with a temperature of approximately 2400 K due to its 17 hr orbit around its G8V host star (Morris et al. 2021). Hubble Space Telescope observations suggest that 55 Cancri e may possess a thick atmosphere (Tsiaras et al. 2016). However, phase curve observations with the Spitzer space telescope (Demory et al. 2016) and ground-based high-resolution transmission spectroscopy point toward 55 Cancri e not possessing a thick atmosphere or having no atmosphere at all (Ridden-Harper et al. 2016; Esteves et al. 2017; Jindal et al. 2020; Deibert et al. 2021a; Zhang et al. 2021). A similar result was found for the cooler 1.3 R⊕ exoplanet LHS 3844 b, which has an equilibrium temperature of 800 K and orbits an M5 host star (Vanderspek et al. 2019). Kreidberg et al. (2019) observed the phase curve of LHS 3844 b with the Spitzer space telescope and found that thick atmospheres with surface pressures greater than 10 bar could be ruled out, while less massive atmospheres would be susceptible to erosion by the stellar wind. Additionally, they found that a bare rock model fit their data well. Another candidate for atmospheric characterization that orbits an M-dwarf is GJ 1132b, which has a radius, mass, and equilibrium temperature of 1.1 R⊕, 1.7 M⊕, and 580 K, respectively (Berta-Thompson et al. 2015). Using transit observations from the Hubble Space Telescope (HST), Swain et al. (2021) inferred that GJ 1132b possesses a H/He-rich atmosphere with large-amplitude spectral features. However, using the same HST data, Libby-Roberts et al. (2022) and Mugnai et al. (2021) independently found a featureless transmission spectrum, possibly indicating an atmosphere with a high mean molecular weight (MMW), a high-altitude aerosol layer, or a near-total lack of an atmosphere. These contrasting results highlight the difficulty of characterizing the atmospheres of small planets, even with space-based instrumentation. Comprehensive searches for the atmospheres of the seven approximately Earth-sized planets that transit the M8V star TRAPPIST-1 have also been carried out. These transit observations with the Hubble and Spitzer space telescopes all point toward the absence of extended hydrogen-dominated atmospheres. However, denser, potentially habitable atmospheres are consistent with the observational limits for some TRAPPIST-1 planets (de Wit et al. 2016; Bourrier et al. 2017b,a; de Wit et al. 2018; Zhang et al. 2018; Wakeford et al. 2019; Gressier et al. 2022). GJ 486b[1] is a 1.3 R⊕ and 2.8 M⊕ exoplanet with an equilibrium temperature of about 700 K, an M3.5 V host star of J-band magnitude 7.2, and an orbital period of 1.5 days (Trifonov et al. 2021). These system properties make GJ 486b well suited to atmospheric characterization with transmission spectroscopy, as reflected by it having one of the largest transmission spectroscopy metrics (as defined by Kempton et al. 2018) of all known terrestrial planets (Trifonov et al. 2021). Therefore, GJ 486b is an ideal observational target to inform our understanding of terrestrial planets around M-dwarf stars. Previous studies have surmised that a wide range of atmospheric compositions are possible for GJ 486b. Caballero et al. (2022) refined GJ 486b’s mass and radius, and presented a suite of interior and atmospheric models. They showed that possible atmospheres include: (i) a H/He-dominated atmosphere with solar abundances; (ii) a H/He atmosphere with enhanced metallicity (e.g., 100x solar abundances); (iii) a H2O-dominated atmosphere; (iv) a CO2-dominated atmosphere; or (v) bare rock with a tenuous atmosphere, possibly containing Na. Geochemical models based on initial conditions representative of a range of possible planets suggest that a H2O-dominated atmosphere is the most likely outcome for a 3 M⊕ planet like GJ 486b (Ortenzi et al. 2020). However, carbonaceous chondrite outgassing measurements suggest that CO2-dominated atmospheres could also evolve on terrestrial planets (Thompson et al. 2021). Differentiating between these scenarios requires spectroscopic observations. Molecular species such as those expected to be in GJ 486b’s atmosphere produce dense forests of spectral lines that can be individually resolved with high-resolution spectroscopy. The signals from these lines can be combined, even if they are individually hidden in the noise, by cross-correlating the data with a template containing the molecular lines (e.g., Snellen et al. 2010; Birkby 2018). This powerful technique has facilitated the detection of species such as H2O, CO, HCN, CH4, NH3, and C2H2 in the transmission spectra of hot Jupiters (e.g., Giacobbe et al. 2021). As high-resolution spectroscopy probes line cores, which contain information about the upper (low-pressure) regions of exoplanet atmospheres, it is highly complementary to low-resolution observations from telescopes such as the JWST, which probe higher pressures (Brogi & Line 2019). JWST is scheduled to observe two transits and eclipses of GJ 486b in programs GO 1981[2] (P.I.: K. Stevenson) and GO 1743[3] (P. I.: M. Mansfield), respectively. Here, we present the first high-resolution transmission spectroscopy observations of GJ 486b. We use three transits to constrain GJ 486b’s atmospheric composition. In what follows, in Sections 2 and 3 we describe our observations and data reduction approach. Section 4 describes our model spectra, while Section 5 describes our cross-correlation methodology. Section 6 presents our results, while Section 8 discusses the implications of our results for the upcoming JWST observations. Finally, Section 9 offers concluding remarks. [1] Alternative names include Wolf 437b and TOI 1827b. [2] program-information.html?id=1981 https://www.stsci.edu/jwst/science-execution/ [3] program-information.html?id=1743 https://www.stsci.edu/jwst/science-execution/

High-Resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b: Abstract & Intro

This paper is available on arxiv under CC 4.0 license. Authors: (1) Andrew Ridden-Harper, Department of Astronomy and Carl Sagan Institute, Cornell University & Las Cumbres Observatory; (2) Stevanus K. Nugroho, Astrobiology Center & Japan & National Astronomical Observatory of Japan; (3) Laura Flagg, Department of Astronomy and Carl Sagan Institute, Cornell University; (4) Ray Jayawardhana, Department of Astronomy, Cornell University; (5) Jake D. Turner, Department of Astronomy and Carl Sagan Institute, Cornell University & NHFP Sagan Fellow; (6) Ernst de Mooij, Astrophysics Research Centre, School of Mathematics and Physics & Queen’s University Belfast; (7) Ryan MacDonald, Department of Astronomy and Carl Sagan Institute; (8) Emily Deibert, David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto & Gemini Observatory, NSF’s NOIRLab; (9) Motohide Tamura, Dunlap Institute for Astronomy & Astrophysics, University of Toronto (10) Takayuki Kotani, Department of Astronomy, Graduate School of Science, The University of Tokyo, Astrobiology Center & National Astronomical Observatory of Japan; (11) Teruyuki Hirano, Astrobiology Center, National Astronomical Observatory of Japan & Department of Astronomical Science, The Graduate University for Advanced Studies; (12) Masayuki Kuzuhara, Las Cumbres Observatory & Astrobiology Center; (13) Masashi Omiya, Las Cumbres Observatory & Astrobiology Center; (14) Nobuhiko Kusakabe, Las Cumbres Observatory & Astrobiology Center. Table of Links Abstract & Introduction Observation Data Reduction and Processing Model Spectra Cross-Correlation Method Results Clouds and Hazes Implications for JWST Conclusion and Acknowledgement Appendix & References 9. CONCLUSION In this study, we searched for the atmosphere of the 1.3 R⊕ exoplanet GJ 486b using high-resolution transmission spectroscopy. Our resultant atmospheric constraints additionally offer an improved understanding of the possible atmospheres for terrestrial planets orbiting M-dwarf stars. We observed three transits of GJ 486b with the spectrographs IRD, IGRINS, and SPIRou, and searched for absorption by its atmosphere with the high-resolution cross-correlation method. We searched for C2H2, CH4, CO, CO2, FeH, H2O, HCN, H2S, K, Na, NH3, PH3, SiO, TiO, and VO, but did not detect any robust atmospheric signals. Our best potential detection was H2O at the 3σ level, seen only in the IGRINS data set. However, this potential signal is likely an artifact of imperfectly removed H2O lines in the stellar spectrum. We suggest that it may be possible to improve the suppression of these stellar lines by using 3D models of stellar convection, as shown by Chiavassa & Brogi (2019). Nevertheless, we derived informative upper limits on the abundances of many chemical species by performing signal injection and recovery tests. Our recovery tests allow us to rule out a clear H2/He-dominated atmosphere with solar molecular abundances to a confidence of >5σ, while also ruling out a clear 100% water atmosphere to a confidence of 3σ. Since a water-dominated atmosphere is often considered to be the most likely possibility for 3 M⊕ planets like GJ 486b (e.g., Ortenzi et al. 2020), our results could have important implications for planetary interior models. We also investigated the implications of our findings for the upcoming JWST transit observations of GJ 486b. We found that these observations will be especially sensitive to the presence of CO2, but with weaker sensitivity to H2O, highlighting the complementary capabilities of high-resolution and JWST observations. In summary, our results indicate that GJ 486b does not possess a cloud-free H/He-dominated atmosphere that has solar abundances. However, it may possess a secondary atmosphere with high mean molecular weight or a H2/He-dominated atmosphere with clouds. Our findings provide further evidence suggesting that terrestrial planets orbiting M-dwarf stars experience significant atmospheric loss. ACKNOWLEDGMENTS We thank the anonymous reviewer for constructive comments. We are also grateful to Hajime Kawahara for helpful suggestions. This research is based [in part] on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical, and natural significance in Hawaii. This work used the Immersion Grating Infrared Spectrometer (IGRINS) that was developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the Mt. Cuba Astronomical Foundation, of the US National Science Foundation under grants AST-1229522 and AST-1702267, of the McDonald Observatory of the University of Texas at Austin, of the Korean GMT Project of KASI, and of the Gemini Observatory. Based on observations obtained at the international Gemini Observatory, a program of NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), the National Research Council (Canada), Agencia Nacional de Investigaci´on y Desarrollo (Chile), Ministerio de Ciencia, Tecnolog´ıa e Innovaci´on (Argentina), Minist´erio da Ciˆencia, Tecnologia, Inova¸c˜oes e Comunica¸c˜oes (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Based on observations obtained at the CanadaFrance-Hawaii Telescope (CFHT), which is operated from the summit of Maunakea by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea which is a significant cultural and historic site. Based on observations obtained with SPIRou, an international project led by Institut de Recherche en Astrophysique et Plan´etologie, Toulouse, France. This research has made use of the Extrasolar Planet Encyclopaedia, NASA’s Astrophysics Data System Bibliographic Services, and the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. M.T. is supported by JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. S. K. N. is supported by JSPS KAKENHI grant No. 22K14092. J.D.T’s support for this work was provided by NASA through the NASA Hubble Fellowship grant #HSTHF2-51495.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5- 26555. : 8.2 m Subaru telescope (IRD), 8.1 m Gemini-South telescope (IGRINS), 3.6 m Canada France Hawai’i Telescope (SPIRou) Facilities : Astropy (Astropy Collaboration et al. 2013, 2018); SciPy (Virtanen et al. 2020); NumPy (Harris et al. 2020); petitRADTRANS (Molli`ere et al. 2019); SpectRes (Carnall 2017). Software

High-Resolution Transmission Spectroscopy: Conclusion and Acknowledgement

This paper is under CC 4.0 license. available on arxiv Authors: (1) Prajwal Niraula, Department of Earth, Atmospheric and Planetary Sciences; (2) Julien de Wit, Department of Earth, Atmospheric and Planetary Sciences; (3) Benjamin V. Rackham, Department of Earth, Atmospheric and Planetary Sciences; (4) Elsa Ducrot, Astrobiology Research Unit, University of Li`ege; (5) Artem Burdanov, Department of Earth, Atmospheric and Planetary Sciences; (6) Ian J. M. Crossfield, Kansas University Department of Physics and Astronomy; (7) Valerie Van Grootel´, Space Sciences, Technologies and Astrophysics Research (STAR) Institute, University of Li`ege; (8) Catriona Murray, 5Cavendish Laboratory; (9) Lionel J. Garcia, Astrobiology Research Unit, University of Li`ege; (10) Roi Alonso, Instituto de Astrof´ısica de Canarias & Dpto. de Astrof´ısica, Universidad de La Laguna; (11) Corey Beard, Department of Physics & Astronomy, The University of California; (12) Yilen Gomez Maqueo Chew, Instituto de Astronom´ıa, Universidad Nacional Aut´onoma de M´exico, Ciudad Universitaria; (13) Laetitia Delrez, Astrobiology Research Unit, University of Li`ege, Space Sciences, Technologies and Astrophysics Research (STAR) Institute, University of Li`ege & 0Observatoire de lUniversit´e de Gen`eve; (14) Brice-Olivier Demory, University of Bern, Center for Space and Habitability; (15) Benjamin J. Fulton, NASA Exoplanet Science Institute/Caltech-IPAC; (16) Michael Gillon, Astrobiology Research Unit, University of Li`ege; (17) Maximilian N. Gunther, Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology; (18) Andrew W. Howard, California Institute of Technology; (19) Howard Issacson, Department of Astronomy, University of California Berkeley; (20) Emmanuel Jehin, Space Sciences, Technologies and Astrophysics Research (STAR) Institute, University of Li`ege; (21) Peter P. Pedersen, Cavendish Laboratory; (22) Francisco J. Pozuelos, Astrobiology Research Unit, University of Li`ege & Space Sciences, Technologies and Astrophysics Research (STAR) Institute, University of Li`ege; (23) Didier Queloz, Cavendish Laboratory; (24) Rafael Rebolo-Lopez, Instituto de Astrof´ısica de Canarias & Dpto. de Astrof´ısica, Universidad de La Laguna'; (25) Sairam Lalitha, School of Physics & Astronomy, University of Birmingham; (26) Daniel Sebastian, Astrobiology Research Unit, University of Li`ege (27) Samantha Thompson, Cavendish Laboratory; (28) Amaury H.M.J. Triaud, School of Physics & Astronomy, University of Birmingham. Table of Links Abstract & Introduction Observation Analysis and Validation Future Prospects & References ABSTRACT We report on the discovery of a transiting Earth-sized (0.95R⊕) planet around an M3.5 dwarf star at 57 pc, K2-315b. The planet has a period of ∼3.14 days, i.e. ∼π, with an instellation of 7.45 S⊕. The detection was made using publicly available data from K2’s Campaign 15. We observed three additional transits with SPECULOOS Southern and Northern Observatories, and a stellar spectrum from Keck/HIRES, which allowed us to validate the planetary nature of the signal. The confirmed planet is well suited for comparative terrestrial exoplanetology. While exoplanets transiting ultracool dwarfs present the best opportunity for atmospheric studies of terrestrial exoplanets with the James Webb Space Telescope, those orbiting mid-M dwarfs within 100 pc such as K2-315b will become increasingly accessible with the next generation of observatories. stars: individual (2MASS J15120519-2006307, EPIC 249631677, TIC 70298662, K2-315b) – planets and satellites: detection Keywords: 1. INTRODUCTION The redesigned Kepler mission, K2 (Howell et al. 2014), has been a success by adding almost 400 confirmed planets to the 2,348 discovered by the original mission[1]. Building upon Kepler (Borucki et al. 2010), K2 expanded the search of planets around brighter stars, covered a wider region of sky along the ecliptic, and studied a variety of astronomical objects . Together, these endeavors have revolutionized the field of exoplanetary science by quadrupling the number of exoplanets known at the time, while K2 in particular has led to exciting discoveries, such as disintegrating planetesimals around the white dwarf WD-1145 (Vanderburg et al. 2015), multi-planet systems around bright stars like GJ 9827 (K2-135) (Niraula et al. 2017; Rodriguez et al. 2018), and resonant chains of planets like the K2-138 system with five planets (Christiansen et al. 2018). Space-based platforms such as Kepler can provide high-quality continuous monitoring of targets above the Earth’s atmosphere. The simultaneous photometric monitoring of tens of thousands of stars enables finding rare configurations (e.g., WD-1145) and answering science questions regarding planetary populations that are more statistical in nature such as how unique our own Solar System is, or what are the most common type of planets (e.g. Fressin et al. 2013; Fulton et al. 2017). Ground-based facilities, on the other hand, often detect fewer planets while operating at a lower cost. These planets frequently exhibit larger signal-to-noise ratios (SNRs) in various metrics (e.g., transmission), thereby allowing for these planets to be characterized further. One such example is the TRAPPIST-1 planetary system (Gillon et al. 2016, 2017), discovered by the TRAPPISTUltra Cool Dwarf Transiting Survey, a prototype survey for the SPECULOOS Survey (Gillon et al. 2013). The goal of the SPECULOOS Survey is to explore the nearest ultracool dwarfs (Teff <3000 K) for transits of rocky planets (Burdanov et al. 2018; Delrez et al. 2018; Jehin et al. 2018; Sebastian et al. in prep.). Although few systems are expected (Delrez et al. 2018; Sebastian et al. in prep.), their impact on the field will be significant as they should provide most of the temperate Earthsized exoplanets amenable for atmospheric studies with the next generation of observatories such as JWST (e.g. Gillon et al. 2020). Beyond the SPECULOOS Survey, which monitors nearby late-M dwarfs for terrestrial planets, the SPECULOOS telescopes have been used to study the planetary population around mid- and late-M dwarfs. In that context, SPECULOOS facilities have been involved in following up and validating planetary candidates, notably from TESS (G¨unther et al. 2019; Kostov et al. 2019; Quinn et al. 2019). Next to confirming planetary candidates that cross detection thresholds, we have started to investigate weaker signals. For this work, we revisited K2 data, a mission which ended only in 2019. We reanalyzed the light curves of stars with Teff < 3500 K, a Kepler magnitude < 15, and a log g > 4.5. While these criteria were motivated particularly to look for planets around ultra-cool dwarfs, they were relaxed in order to allow room for errors in the stellar properties and improve completeness of the analysis. Among the 1,213 stars fitting these criteria, EPIC 249631677 presented the strongest periodic transit-like signal. In this paper, we report the discovery of an Earthsized K2 planet in a close-in orbit around EPIC 249631677. The paper is structured as follow; observations (Section 2), analysis and validation (Section 3), and the discussion in regards to future prospects for characterization (Section 4). In this paper, we report the discovery of an Earthsized K2 planet in a close-in orbit around EPIC 249631677. The paper is structured as follow; observations (Section 2), analysis and validation (Section 3), and the discussion in regards to future prospects for characterization (Section 4). [1] https://exoplanetarchive.ipac.caltech.edu

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