VPLANET MagmOc is a versatile magma ocean model with erosion of water vapour in the open source VPLANET framework. Wepresent here a major improvement of this model that includes now a) thermal emission calculated with a full radiative transfer code and b) simultaneous outgasing of H2O and CO2 with full feedback on outgassing informed by planet formation models.We derived evolution tracks of an outgassed mixed H2O/CO2 atmosphere on TRAPPIST-1e, f and g. We find that all planets, in particular TRAPPIST-1 g, run the risk to evolve into Exo-Venuses with thick CO2 atmospheres after the magma ocean stage for an intial water budget of more than 10 terrestrial ocean (TO) of water within tens of million years.At the inner edge of the habitable zone, on TRAPPIST-1 e, we find that the combination of H2O atmosphere loss and CO2 outgassing reduces the thermal emission on the planet such that the magma ocean stage can be almost doubled from tens of million years to 80 million years for 10 TO intial water.We thus conclude that careful consideration has to be given to the various geophysical feedback effects as these can have a profound impact on the magma ocean evolution stage and thus on the overall water budget and the secondary atmosphere.

Aims. We investigate the impact of CO2 on the distribution of water on TRAPPIST-1 e, f, and g during the magma ocean stage. These potentially habitable rocky planets are currently the most accessible for astronomical observations. A constraint on the volatile budget during the magma ocean stage is a key link to planet formation and also to judging their habitability. Methods. We expanded the MagmOc module of the VPLanet environment to perform simulations with 1-100 terrestrial oceans (TOs) of H2O with and without CO2 and for albedos 0 and 0.75. The CO2 mass was scaled with initial H2O by a constant factor between 0.1 and 1. Results. The magma ocean state of rocky planets begins with a CO2-dominated atmosphere but can evolve into a H2O dominated state, depending on initial conditions. For less than 10 TO initial H2O, the atmosphere tends to desiccate and the evolution can end with a CO2 dominated atmosphere. Otherwise, the final state is a thick (>1000 bar) H2O-CO2 atmosphere. Complete atmosphere desiccation with less than 10 TO initial H2O can be significantly delayed for TRAPPIST-1 e and f, when H2O has to diffuse through a CO2 atmosphere to reach the upper atmosphere, where photolysis due to extreme ultra violet irradiation occurs. As a consequence of CO2 diffusion-limited water loss, the time of mantle solidification for TRAPPIST-1 e, f, and g can be significantly extended compared to a pure H2O evolution by up to 40 Myrs for an albedo of 0.75 and by up to 200 Mys for an albedo of 0. The addition of CO2 further results in a higher water content in the melt during the magma ocean stage. Thus, more water can be sequestered in the solid mantle. However, only up to 6% of the initial water mass can be stored in the mantle at the end of the magma ocean stage. Our compositional model adjusted for the measured metallicity of TRAPPIST-1 yields for the dry inner planets (b, c, d) an iron fraction of 27 wt%. For TRAPPIST-1 e, this iron fraction would be compatible with a (partially) desiccated evolution scenario and a CO2 atmosphere with surface pressures of a few 100 bar. Conclusions. A comparative study between TRAPPIST-1 e and the inner planets may yield the most insights about formation and evolution scenarios by confronting, respectively, a scenario with a desiccated evolution due to volatile-poor formation and a volatile-rich scenario with extended atmospheric erosion.

Lightning has been suggested to play a role in triggering the occurrence of bio-ready chemical species. Future missions (PLATO, ARIEL, HWO, LIFE) and ground-based ELTs will investigate the atmospheres of potentially habitable exoplanets. We aim to study the effect of lightning on the atmospheric chemistry, how it affects false-positive and false-negative biosignatures, and if its effect would be observable on an exo-Earth and on TRAPPIST-1 planets. We use a combination of laboratory experiments, photochemical and radiative transfer modelling. With spark discharge experiments in N2-CO2-H2 gas mixtures, representing a range of possible rocky-planet atmospheres, we investigate the production of potential lightning signatures (CO, NO), possible biosignature gases (N2O, NH3, CH4), and important prebiotic precursors (HCN, Urea). Photochemical simulations are conducted for oxygen-rich and anoxic atmospheres for rocky planets in the habitable zones of the Sun and TRAPPIST-1 for a range of lightning flash rates. Synthetic spectra are calculated using SMART to study the atmosphere's reflectance, emission, and transmission spectra. Lightning enhances the spectral features of NO, NO2, and, in some cases, CO; CH4 and C2H6 may be enhanced indirectly. Lightning at a flash rate slightly higher than on modern Earth can mask the ozone features of an oxygen-rich, biotic atmosphere, making it harder to detect the biosphere. Lightning flash rates at least ten times higher than on modern Earth can mask the presence of ozone in the anoxic, abiotic atmosphere of a planet orbiting a late M dwarf, reducing the potential for a false-positive life-detection. The threshold lightning rates to eliminate oxygen and ozone false positive biosignatures on planets orbiting ultra-cool dwarfs is up to ten times higher than the modern flash rate, suggesting that lightning cannot always prevent these false-positive scenarios.

VPLANET MagmOc is a versatile magma ocean model with erosion of water vapour in the open source VPLANET framework. Wepresent here a major improvement of this model that includes now a) thermal emission calculated with a full radiative transfer code and b) simultaneous outgasing of H2O and CO2 with full feedback on outgassing informed by planet formation models. We derived evolution tracks of an outgassed mixed H2O/CO2 atmosphere on TRAPPIST-1e, f and g. We find that all planets, in particular TRAPPIST-1 g, run the risk to evolve into Exo-Venuses with thick CO2 atmospheres after the magma ocean stage for an intial water budget of more than 10 terrestrial ocean (TO) of water within tens of million years. At the inner edge of the habitable zone, on TRAPPIST-1 e, we find that the combination of H2O atmosphere loss and CO2 outgassing reduces the thermal emission on the planet such that the magma ocean stage can be almost doubled from tens of million years to 80 million years for 10 TO intial water.We thus conclude that careful consideration has to be given to the various geophysical feedback effects as these can have a profound impact on the magma ocean evolution stage and thus on the overall water budget and the secondary atmosphere.

The potentially habitable planets in the TRAPPIST-1 system (e,f,g) may have experienced a prolonged magma ocean phase during which volatiles were partitioned between the molten interior and the atmosphere. The duration of the magma ocean phase is determined by 1) the incident stellar radiation, 2) atmospheric heating due to the greenhouse effect, 3) water photolysis and hydrogen escape, 4) tidal heating, 5) radiogenic heating, and 6) the magma ocean’s initial temperature. We simulate these phenomena simultaneously with the VPLanet software package, including a new module called MagmOc that treats the thermal and geochemical evolution (water, O2, and CO2) of the magma ocean. We find the TRAPPIST-1 planets’ evolution depends on initial water content and distance from the host star. In a “dry” scenario (initial water content < 5TO, for planet g), the atmosphere after magma ocean solidification is desiccated and devoid of abiotically generated O2. In an “intermediate” scenario (initial water content between 5 and 50TO), the post magma ocean atmosphere still contains water. XUV photolysis of this water leads to abiotic O2 build-up. For “extremely wet” cases (initial water content > 50 TO) or extreme internal heating, the magma ocean lifetime can be extended and quench oxygen build up. The currently inferred high water content of the planets favors the extremely wet scenario for TRAPPIST-1 g and f, i.e. they likely ended their magma ocean state with large amounts of water vapor in their atmospheres but potentially avoid the build-up of large amounts of oxygen. TRAPPIST-1 e, on the other hand, could have experienced the intermediate scenario and is therefore even less likely to possess large amounts of abiotically created atmospheric O2.

A key first step to constrain the impact of energetic particles in exoplanet atmospheres is to detect the chemical signature of ionization due to stellar energetic particles and Galactic cosmic rays. We focus on GJ 436, a well-studied M dwarf with a warm Neptune-like exoplanet. We demonstrate how the maximum stellar energetic particle momentum can be estimated from the stellar X-ray luminosity. We model energetic particle transport through the atmosphere of a hypothetical exoplanet at orbital distances between a = 0.01 and 0.2 au from GJ 436, including GJ 436 b's orbital distance (0.028 au). For these distances, we find that, at the top of atmosphere, stellar energetic particles ionize molecular hydrogen at a rate of zeta(StEP,H2) similar to 4 x 10(-10) to 2 x 10(-13) s(-1). In comparison, Galactic cosmic rays alone lead to zeta(GCR,H2) similar to 2 x 10(-20)-10(-18) s(-1). At 10 au, we find that ionization due to Galactic cosmic rays equals that of stellar energetic particles: zeta(GCR,H2) = zeta(StEP,H2) similar to 7 x 10(-18) s(-1) for the top-of-atmosphere ionization rate. At GJ 436 b's orbital distance, the maximum ion-pair production rate due to stellar energetic particles occurs at pressure P similar to 10(-3) bar, while Galactic cosmic rays dominate for P > 10(2) bar. These high pressures are similar to what is expected for a post-impact early Earth atmosphere. The results presented here will be used to quantify the chemical signatures of energetic particles in warm Neptune-like atmospheres.

Lightning can produce bioavailable nitrogen oxides, but it is unknown whether this was a substantial nutrient source for Earth's earliest biosphere. Comparison of nitrogen isotope measurements from spark discharge experiments to those from the rock record suggests that lightning was likely not the main source of bioavailable nitrogen for the biosphere throughout most of Earth's history.

Bioavailable nitrogen is thought to be a requirement for the origin and sustenance of life. Before the onset of biological nitrogen fixation, abiotic pathways to fix atmospheric N 2 must have been prominent to provide bioavailable nitrogen to Earth’s earliest ecosystems. Lightning has been shown to produce fixed nitrogen as nitrite and nitrate in both modern atmospheres dominated by N 2 and O 2 and atmospheres dominated by N 2 and CO 2 analogous to the Archaean Earth. However, a better understanding of the isotopic fingerprints of lightning-generated fixed nitrogen is needed to assess the role of this process on early Earth. Here we present results from spark discharge experiments in N 2 −CO 2 and N 2 −O 2 gas mixtures. Our experiments suggest that lightning-driven nitrogen fixation may have been similarly efficient in the Archaean atmosphere, compared with modern times. Measurements of the isotopic ratio (δ 15 N) of the discharge-produced nitrite and nitrate in solution show very low values of −6‰ to −15‰ after equilibration with the gas phase with a calculated endmember composition of −17‰. These results are much lower than most δ 15 N values documented from the sedimentary rock record, which supports the development of biological nitrogen fixation earlier than 3.2 billion years ago. However, some Paleoarchean records (3.7 billion years ago) may be consistent with lightning-derived nitrogen input, highlighting the potential role of this process for the earliest ecosystems.

&lt;p&gt;Nitrogen is an essential building block of DNA, RNA, and proteins and, subsequently, it must have been bioavailable since the origin of life. On modern Earth, biological sources are mostly responsible for making nitrogen bioavailable via N&lt;sub&gt;2&lt;/sub&gt; fixation with only a few percent coming from abiotic sources. On early Earth, before the origin of life and the onset of biological nitrogen fixation, these abiotic sources such as lightning must have been the dominant producer of bioavailable nitrogen. Previous experiments have shown that in N&lt;sub&gt;2&lt;/sub&gt;-dominated atmospheres lightning leads to the formation of nitrate (NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;) and nitrite (NO&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;), which could not only have facilitated the origin of life but also sustained the earliest ecosystems. This hypothesis has been difficult to test with the available rock record because geochemical fingerprints of this fixed nitrogen source have not been developed. We present new results from spark discharge experiments in varying atmospheric compositions corresponding to different points of time in Earth&amp;#8217;s evolution. We find substantial amounts of nitrate are produced in an N&lt;sub&gt;2&lt;/sub&gt;/CO&lt;sub&gt;2&lt;/sub&gt; atmosphere. Furthermore, we investigate the effect of lightning on the isotopic composition of the resulting nitrogen oxides in solution. Our fixed nitrogen is depleted in heavy &lt;sup&gt;15&lt;/sup&gt;N in comparison to atmospheric N&lt;sub&gt;2&lt;/sub&gt;, in line with rock samples older than 3.2 billion years. For the first time we can assess to what degree lightning chemistry may have influenced the origin and early evolution of life. However, the spark in our experiment is much smaller and cooler than lightning channels in Earth&amp;#8217;s atmosphere. To extrapolate our experimental results to full-scale planetary atmospheres we plan to complement them with simulations of the atmospheric chemistry of exoplanets and Earth. This will allow us to extend our experiments to real lightning conditions and develop observable tracers for lightning chemistry in exoplanetary atmospheres. Being able to predict the bioavailability of nitrogen on other worlds will be another factor determining the potential habitability of these worlds.&lt;/p&gt;

Hot Jupiters provide valuable natural laboratories for studying potential contributions of high-energy radiation to prebiotic synthesis in the atmospheres of exoplanets. HD 189733b, a hot Jupiter orbiting a K star, is one of the most studied and best observed exoplanets. We combine XUV observations and 3D climate simulations to model the atmospheric composition and kinetic chemistry with the STAND2019 network. We show how XUV radiation, cosmic rays (CR), and stellar energetic particles (SEP) influence the chemistry of the atmosphere. We explore the effect that the change in the XUV radiation has over time, and we identify key atmospheric signatures of an XUV, CR, and SEP influx. 3D simulations of HD 189733b's atmosphere with the 3D Met Office Unified Model provide a fine grid of pressure-temperature profiles, consistently taking into account kinetic cloud formation. We apply HST and XMM-Newton/Swift observations obtained by the MOVES programmewhich provide combined X-ray and ultraviolet (XUV) spectra of the host star HD 189733 at 4 different points in time. We find that the differences in the radiation field between the irradiated dayside and the shadowed nightside lead to stronger changes in the chemical abundances than the variability of the host star's XUV emission. We identify ammonium (NH4+) and oxonium (H3O+) as fingerprint ions for the ionization of the atmosphere by both galactic cosmic rays and stellar particles. All considered types of high-energy radiation have an enhancing effect on the abundance of key organic molecules such as hydrogen cyanide (HCN), formaldehyde (CH2O), and ethylene (C2H4). The latter two are intermediates in the production pathway of the amino acid glycine (C2H5NO2) and abundant enough to be potentially detectable by JWST. Ultimately, we show that high energy processes potentially play an important role in prebiotic chemistry. P Barth et al., MOVES IV. Modelling the influence of stellar XUV-flux, cosmic rays, and stellar energetic particles on the atmospheric composition of the hot Jupiter HD 189733b, Monthly Notices of the Royal Astronomical Society, in press, DOI:10.1093/mnras/staa3989

The TRAPPIST-1 system contains seven roughly Earth-sized planets locked in a multiresonant orbital configuration 1 , 2 , which has enabled precise measurements of the planets’ masses and constrained their compositions 3 . Here we use the system’s fragile orbital structure to place robust upper limits on the planets’ bombardment histories. We use N -body simulations to show how perturbations from additional objects can break the multiresonant configuration by either triggering dynamical instability or simply removing the planets from resonance. The planets cannot have interacted with more than ~5% of one Earth mass ( M ⊕ ) in planetesimals—or a single rogue planet more massive than Earth’s Moon—without disrupting their resonant orbital structure. This implies an upper limit of 10 −4 M ⊕ to 10 −2 M ⊕ of late accretion on each planet since the dispersal of the system’s gaseous disk. This is comparable to (or less than) the late accretion on Earth after the Moon-forming impact 4 , 5 , and demonstrates that the growth of the TRAPPIST-1 planets was complete in just a few million years, roughly an order of magnitude faster than that of the Earth 6 , 7 . Our results imply that any large water reservoirs on the TRAPPIST-1 planets must have been incorporated during their formation in the gaseous disk.

We propose a classification of exoplanet atmospheres based on their H, C, O, and N element abundances below about 600 K. Chemical equilibrium models were run for all combinations of H, C, O, and N abundances, and three types of solutions were found, which are robust against variations of temperature, pressure, and nitrogen abundance. Type A atmospheres contain H2O, CH4, NH3, and either H2 or N2, but only traces of CO2 and O2. Type B atmospheres contain O2, H2O, CO2, and N2, but only traces of CH4, NH3, and H2. Type C atmospheres contain H2O, CO2, CH4, and N2, but only traces of NH3, H2, and O2. Other molecules are only present in ppb or ppm concentrations in chemical equilibrium, depending on temperature. Type C atmospheres are not found in the Solar System, where atmospheres are generally cold enough for water to condense, but exoplanets may well host such atmospheres. Our models show that graphite (soot) clouds can occur in type C atmospheres in addition to water clouds, which can occur in all types of atmospheres. Full-equilibrium condensation models show that the outgassing from warm rock can naturally provide type C atmospheres. We conclude that type C atmospheres, if they exist, would lead to false positive detections of biosignatures in exoplanets when considering the coexistence of CH4 and CO2, and suggest other, more robust non-equilibrium markers.

In the 1950s, Stanley Miller and Harald Urey proved in their famous experiment that an electric discharge in an abiotic atmosphere of CH 4 , H 2 , NH 3 , and H 2 O can lead to the formation of amino acids [1]. Even though the Earth’s primordial atmosphere is expected to have been mildly oxidizing rather than reducing [2], this experiment shows the important role of lightning as an energy source in the formation of prebiotic molecules. Subsequent work has shown that in an N 2 dominated atmosphere, lightning can initiate abiotic nitrogen fixation through the formation of nitrate (NO 3- ) and nitrite (NO 2- ) [3]. These forms of nitrogen could not only have facilitated the origin of life but also sustained the early biosphere. So far, however, this hypothesis has been difficult to test with the available rock record, because geochemical fingerprints of this nitrogen source have not been developed. We will present new results from spark discharge experiments in varying atmospheric compositions corresponding to different points in time of Earth’s evolution. We show how the production of nitrate and nitrite depends on the O 2 /N 2 and CO 2 /N 2 -ratio in the gas phase. Furthermore, we investigate the effect of lightning on the isotopic composition of nitrogen in the produced nitrate. We find that the isotopic fractionation between N 2 gas and aqueous nitrate depends on atmospheric composition and on other parameters of the experiment such as the electric field strength. By comparison to the sedimentary nitrogen isotope record from the Archean Earth our results allow us to assess for the first time to what degree the origin and early evolution of life may have been influenced by lightning chemistry.

Recent observations of the potentially habitable planets TRAPPIST-1 e, f, and g suggest that they possess large water mass fractions of possibly several tens of weight percent of water, even though the host star's activity should drive rapid atmospheric escape. These processes can photolyze water, generating free oxygen and possibly desiccating the planet. After the planets formed, their mantles were likely completely molten with volatiles dissolving and exsolving from the melt. To understand these planets and prepare for future observations, the magma ocean phase of these worlds must be understood. To simulate these planets, we have combined existing models of stellar evolution, atmospheric escape, tidal heating, radiogenic heating, magma-ocean cooling, planetary radiation, and water-oxygen-iron geochemistry. We present MagmOc, a versatile magma-ocean evolution model, validated against the rocky super-Earth GJ 1132b and early Earth. We simulate the coupled magma-ocean atmospheric evolution of TRAPPIST-1 e, f, and g for a range of tidal and radiogenic heating rates, as well as initial water contents between 1 and 100 Earth oceans. We also reanalyze the structures of these planets and find they have water mass fractions of 0-0.23, 0.01-0.21, and 0.11-0.24 for planets e, f, and g, respectively. Our model does not make a strong prediction about the water and oxygen content of the atmosphere of TRAPPIST-1 e at the time of mantle solidification. In contrast, the model predicts that TRAPPIST-1 f and g would have a thick steam atmosphere with a small amount of oxygen at that stage. For all planets that we investigated, we find that only 3-5% of the initial water will be locked in the mantle after the magma ocean solidified.

Hot Jupiters provide valuable natural laboratories for studying potential contributions of high-energy radiation to pre-biotic synthesis in the atmospheres of exoplanets. In this fourth paper of the Multiwavelength Observations of an eVaporating Exoplanet and its Star (MOVES) programme, we study the effect of different types of high-energy radiation on the production of organic and pre-biotic molecules in the atmosphere of the hot Jupiter HD 189733b. Our model combines X-ray and UV observations from the MOVES programme and 3D climate simulations from the 3D Met Office Unified Model to simulate the atmospheric composition and kinetic chemistry with the STAND2019 network. Also, the effects of galactic cosmic rays and stellar energetic particles are included. We find that the differences in the radiation field between the irradiated dayside and the shadowed nightside lead to stronger changes in the chemical abundances than the variability of the host star's XUV emission. We identify ammonium (NH4+) and oxonium (H3O+) as fingerprint ions for the ionization of the atmosphere by both galactic cosmic rays and stellar particles. All considered types of high-energy radiation have an enhancing effect on the abundance of key organic molecules such as hydrogen cyanide (HCN), formaldehyde (CH2O), and ethylene (C2H4). The latter two are intermediates in the production pathway of the amino acid glycine (C2H5NO2) and abundant enough to be potentially detectable by JWST.

We present WASP-43b climate simulations with deep wind jets (down to 700 bar) that are linked to retrograde (westward) flow at the equatorial day side for p < 0.1 bar. Retrograde flow inhibits efficient eastward heat transport and naturally explains the small hotspot shift and large day-night-side gradient of WASP-43b (P-orb = P-rot = 0.8135 d) observed with Spitzer. We find that deep wind jets are mainly associated with very fast rotations (P-rot = P-orb = 1.5 d) which correspond to the Rhines length smaller than 2 planetary radii. We also diagnose wave activity that likely gives rise to deviations from superrotation. Further, we show that we can achieve full steady state in our climate simulations by imposing a deep forcing regime for p > 10 bar: convergence time-scale tau(conv) = 10(6)-10(8) s to a common adiabat, as well as linear drag at depth (p = 200 bar), which mimics to first-order magnetic drag. Lower boundary stability and the deep forcing assumptions were also tested with climate simulations for HD 209458b (P-orb = P-rot = 3.5 d). HD 209458b simulations always show shallow wind jets (never deeper than 100 bar) and unperturbed superrotation. If we impose a fast rotation (Porb = Prot = 0.8135 d), also the HD 209458b-like simulation shows equatorial retrograde flow at the day side. We conclude that the placement of the lower boundary at p = 200 bar is justified for slow rotators like HD 209458b, but we suggest that it has to be placed deeper for fast-rotating, dense hot Jupiters (P-orb <= 1.5 d) like WASP-43b. Our study highlights that the deep atmosphere may have a strong influence on the observable atmospheric flow in some hot Jupiters.

We describe a software package called VPLanet that simulates fundamental aspects of planetary system evolution over Gyr timescales, with a focus on investigating habitable worlds. In this initial release, eleven physics modules are included that model internal, atmospheric, rotational, orbital, stellar, and galactic processes. Many of these modules can be coupled simultaneously to simulate the evolution of terrestrial planets, gaseous planets, and stars. The code is validated by reproducing a selection of observations and past results. VPLanet is written in C and designed so that the user can choose the physics modules to apply to an individual object at runtime without recompiling, i.e., a single executable can simulate the diverse phenomena that are relevant to a wide range of planetary and stellar systems. This feature is enabled by matrices and vectors of function pointers that are dynamically allocated and populated based on user input. The speed and modularity of VPLanet enables large parameter sweeps and the versatility to add/remove physical phenomena to assess their importance. VPLanet is publicly available from a repository that contains extensive documentation, numerous examples, Python scripts for plotting and data management, and infrastructure for community input and future development.

We present WASP-43b climate simulations with deep wind jets (reaching at least 700~bar) that are linked to anti-rotating (westward) flow at the equatorial day side for $p 10$~bar: a smaller convergence time scale $tau_{conv}=10^6-10^8$~s to ensure the convergence to a common adiabat, a deep lower boundary of $p=700$~bar, as well as linear drag at depth ($pgeq 200$~bar), which mimics to first order magnetic drag. Lower boundary stability and the deep forcing assumptions were also tested with climate simulations for HD~209458b ($P_{text{orb}}=P_{text{rot}}=3.5$~days). HD~209458b simulations with deep forcing assumptions imposed show shallow wind jets (never extending deeper than 100~bar into the interior) and full superrotation. If we impose a very fast rotation ($P_{text{orb}}=P_{text{rot}}=0.8135$~days), also the HD~209458b-like simulation shows equatorial anti-rotation at the day side. We conclude that the placement of the lower boundary at $p=200$~bar is justified for slow rotators like HD~209458b, but it has to be placed deeper for fast-rotating hot Jupiters ($P_{text{orb}}leq 1.5$~days) like WASP-43b. Our study highlights that the deep atmosphere and lower boundary conditions may have a strong influence on the observable atmospheric flow in hot Jupiters.