The detection and atmospheric characterization of potentially habitable, temperate terrestrial exoplanets using a space-based mid-infrared nulling interferometer is a major goal of contemporary astrophysics. A central part of the analysis of such an instrument is the treatment of correlated errors arising from perturbations in the system. While previous studies have often accounted for their effects in a limited manner, we aim to treat them comprehensively here, and we argue that data whitening based on the covariance of these errors is a suitable method to mitigate their impact. We present a framework that quantitatively connects instrumental perturbations to performance metrics, and we develop two computational tools to support our analysis: PHRINGE , for the generation of synthetic nulling data, and LIFE sim MC, a new Monte Carlo–based end-to-end simulator for the Large Interferometer For Exoplanets. Applying our framework to a reference observation of an Earth twin orbiting a Sun twin at 10 pc, we find that whitening is not only essential for a correct interpretation of the detection metric used in hypothesis testing, but also improves the estimates of the planetary properties. Moreover, our approach enables an estimation of the spectral covariance of the extracted planetary spectra, providing valuable additional input for future atmospheric retrievals. We therefore recommend incorporating the framework into performance assessments and requirement derivations for future nulling interferometers.

Context. The Enhanced Resolution Imager and Spectrograph (ERIS) is the new adaptive optics (AO) assisted infrared instrument at the Very Large Telescope (VLT). Its refurbished integral field spectrograph (IFS) SPIFFIER leverages a new AO module, enabling high-contrast imaging applications and giving access to the orbital and atmospheric characterisation of super-Jovian exoplanets. Aims. We tested the detection limits of ERIS, and demonstrate its scientific potential by exploring the atmospheric composition of the young super-Jovian AF Lep b. Additionally, we improved its orbital solution by measuring its radial velocity relative to its host star. Methods. We present new spectroscopic observations of AF Lep b in K-band at R similar to 11 000 obtained with ERIS/SPIFFIER at the VLT. We reduced the data using the standard pipeline together with a custom wavelength calibration routine, and removed the stellar point spread function using principal component analysis along the spectral axis. We computed molecular maps by cross-correlating the residuals with molecular spectral templates and measured the radial velocity of the planet relative to the star. Furthermore, we computed contrast grids for molecular mapping by injecting fake planets. Results. We detect a strong signal from H2O and CO but not from CH4 or CO2. This result corroborates the hypothesis of chemical disequilibrium in the atmosphere of AF Lep b. Our measurement of the RV of the planet yields Delta v(R, P star) = 7.8 +/- 1.7 km s(-1). This enables us to disentangle the degeneracy of the orbital solution; specifically, the correct longitude of the ascending node is Omega = 248(-0.7)(+0.4) deg and the argument of periapsis is omega = 109(-21)(+13) deg. Our detection limits reach a contrast of Delta K = 11.5 mag at 0 ''.12 for the spectral templates of H2O and CO, significantly extending the parameter space available to moderately high spectral resolution towards small angular separation. Conclusions. Our results demonstrate the competitiveness of the new ERIS/SPIFFIER instrument for the orbital and atmospheric characterisation of exoplanets at high contrast and small angular separation.

One of the primary objectives in modern astronomy is to discover and study planets with characteristics similar to Earth. This pursuit involves analyzing the spectra of exoplanets and searching for biosignatures. Contamination of spectra by nearby objects (e.g., other planets and moons in the same system) is a significant concern and must be addressed for future exo-Earth searching missions. The aim is to estimate, for habitable planets, the probability of spectral contamination by other planets within the same star system. This investigation focuses on the Large Interferometer For Exoplanets (LIFE). Since the Rayleigh criterion is inapplicable to interferometers such as those proposed for LIFE, we present new criteria based on the principle of parsimony that take into account two types of issues: contamination or blending of point sources and cancellation of point sources due to destructive interference. We define a new spatial resolution metric associated with contamination or cancellation that generalizes to a broader family of observing instruments. In the current baseline design, LIFE is an X-array architecture nulling interferometer. Our investigation reveals that its transmission map introduces the potential for two point sources to appear as one, even if they do not appear in close proximity. We find that LIFE has a spatial resolution comparable to that of a traditional telescope with a diameter of D = 600 m, observing at λ = 4 μ m. Our survey of a star system population shows that, out of 73.4 expected habitable planets detected, 71.3 are not contaminated, on average.

The main challenge of exoplanet high-contrast imaging (HCI) is to separate the signal of exoplanets from their host stars, which are many orders of magnitude brighter. HCI for ground-based observations is further exacerbated by speckle noise originating from perturbations in Earth’s atmosphere and imperfections in the telescope optics. Various data postprocessing techniques are used to remove this speckle noise and reveal the faint planet signal. Often, however, a significant part of the planet signal is accidentally subtracted together with the noise. In the present work, we use explainable machine learning to investigate the reason for the loss of the planet signal for one of the most used postprocessing methods: principal component analysis (PCA). We find that PCA learns the shape of the telescope point-spread function for high numbers of PCA components. This representation of the noise captures not only the speckle noise but also the characteristic shape of the planet signal. Building on these insights, we develop a new postprocessing method (4S) that constrains the noise model to minimize this signal loss. We apply our model to 11 archival HCI data sets from the Very Large Telescope NACO instrument in the L ’ band and find that our model consistently outperforms PCA. The improvement is largest at close separations to the star (≤4 λ / D ), providing up to 1.5 mag deeper contrast. This enhancement enables us to detect the exoplanet AF Lep b in data from 2011, 11 yr before its subsequent discovery. We present updated orbital parameters for this object.

Identifying key observables is essential for enhancing our knowledge of exoplanet habitability and biospheres, as well as improving future mission capabilities. While currently challenging, future observatories such as the Large Interferometer for Exoplanets (LIFE) will enable atmospheric observations of a diverse sample of temperate terrestrial worlds. Using thermal emission spectra that represent conventional predictions of atmospheric CO _2 variability across the habitable zone (HZ), we assess the ability of the LIFE mission—as a specific concept for a future space-based interferometer—to detect CO _2 trends indicative of the carbonate–silicate (Cb–Si) weathering feedback, a well-known habitability marker and potential biological tracer. Therefore, we explore the feasibility of differentiating between CO _2 trends in biotic and abiotic planet populations. We create synthetic exoplanet populations based on geochemistry-climate predictions and perform retrievals on simulated thermal emission observations. The results demonstrate the robust detection of population-level CO _2 trends in both biotic and abiotic scenarios for population sizes as small as 30 exo-Earth candidates (EECs) and the lowest assessed spectrum quality in terms of signal-to-noise ratio, S/N = 10, and spectral resolution, R = 50. However, biased CO _2 partial pressure constraints hinder accurate differentiation between biotic and abiotic trends. If these biases were corrected, accurate differentiation could be achieved for populations with ≥100 EECs. We conclude that LIFE can effectively enable population-level characterization of temperate terrestrial atmospheres and detect CO _2 trends driven by the Cb–Si cycle as habitability indicators. Nevertheless, the identified biases underscore the importance of testing atmospheric characterization performance against the broad diversity expected for planetary populations.

We present aperture masking interferometry (AMI) observations of the star HIP 65426 at 3.8 μ m, as part of the JWST Direct Imaging Early Release Science program, obtained using the Near Infrared Imager and Slitless Spectrograph instrument. This mode provides access to very small inner working angles (even separations slightly below the Michelson limit of 0.5 λ / D for an interferometer), which are inaccessible with the classical inner working angles of the JWST coronagraphs. When combined with JWST’s unprecedented infrared sensitivity, this mode has the potential to probe a new portion of parameter space across a wide array of astronomical observations. Using this mode, we are able to achieve a 5 σ contrast of Δ m F380M ∼ 7.62 ± 0.13 mag relative to the host star at separations ​​​​​≳0 . ″ 07 , and the contrast deteriorates steeply at separations ≲0 . ″ 07. However, we detect no additional companions interior to the known companion HIP 65426b (at separation ∼0 . ″ 82 or 8 7 − 31 + 108 au ). Our observations thus rule out companions more massive than 10–12 M Jup at separations ∼10–20 au from HIP 65426, a region out of reach of ground- or space-based coronagraphic imaging. These observations confirm that the AMI mode on JWST is sensitive to planetary mass companions at close-in separations (≳0 . ″ 07), even for thousands of more distant stars at ∼100 pc, in addition to the stars in the nearby young moving groups and associations, as stated in previous works. This result will allow the planning and successful execution of future observations to probe the inner regions of nearby stellar systems, opening an essentially unexplored parameter space.

Energy limits that delineate the `habitable zone' for exoplanets depend on a given exoplanet's net planetary albedo (or `Bond albedo'). We here demonstrate that the planetary albedo of an observed exoplanet is limited by the above-cloud atmosphere - the region of the atmosphere that is probed in remote observation. We derive an analytic model to explore how the maximum planetary albedo depends on the above-cloud optical depth and scattering versus absorbing properties, even in the limit of a perfectly reflective grey cloud layer. We apply this framework to sub-Neptune K2-18b, for which a high planetary albedo has recently been invoked to argue for the possibility of maintaining a liquid water ocean surface, despite K2-18b receiving an energy flux from its host star that places it inside of its estimated `habitable zone' inner edge. We use a numerical multiple-scattering line-by-line radiative transfer model to retrieve the albedo of K2-18b based on the observational constraints from the above-cloud atmosphere. Our results demonstrate that K2-18b's observed transmission spectrum already restricts its possible planetary albedo to values below the threshold required to be potentially habitable, with the data favouring a median planetary albedo of 0.17-0.18. Our results thus reveal that currently characteriseable sub-Neptunes are likely to be magma-ocean or gas-dwarf worlds. The methods that we present are generally applicable to constrain the planetary albedo of any exoplanet with measurements of its observable atmosphere, enabling the quantification of potential exoplanet habitability with current observational capabilities.

With the astrophysics community working toward the first observations and characterizations of Earth-like exoplanets, interest in space-based nulling interferometry has been renewed. This technique promises unique scientific and technical advantages by enabling direct mid-infrared observations. However, concept studies of nulling interferometers often overlook the impact of systematic noise caused by instrument perturbations. Earlier research introduced analytical and numerical models to address instrumental noise; building on these results, we reproduce key simulations and report that the noise in the differential output of nulling interferometers follows a non-Gaussian distribution. The presence of non-Gaussian noise challenges the validity of classical hypothesis tests in detection performance estimates, as their reliance on Gaussian assumptions leads to overconfidence in detection thresholds. For the first time, we derive the true noise distribution of the differential output of a dual Bracewell nulling interferometer, demonstrating that it follows iterative convolutions of Bessel functions. Understanding this noise distribution enables a refined formulation of hypothesis testing in nulling interferometry, leading to a semianalytical prediction of detection performance. This computationally efficient instrument model, implemented in a publicly available codebase, is designed for integration into science yield predictions for nulling interferometry mission concepts. It will play a key role in refining key mission parameters for the Large Interferometer For Exoplanets.

Future telescopes will survey temperate, terrestrial exoplanets to estimate the frequency of habitable ( η _Hab ) or inhabited ( η _Life ) planets. This study aims to determine the minimum number of planets ( N ) required to draw statistically significant conclusions, particularly in the case of a null result (i.e., no detections). Using a Bayesian framework, we analyzed surveys of up to N = 100 planets to infer the frequency of a binary observable feature ( η _obs ) after null results. Posterior best fits and upper limits were derived for various survey sizes and compared with predicted yields from missions like the Large Interferometer for Exoplanets (LIFE) and the Habitable Worlds Observatory (HWO). Our findings indicate that N = 20–50 “perfect” observations (100% confidence in detecting or excluding the feature) yield conclusions relatively independent of priors. To achieve 99.9% upper limits of η _obs ≤ 0.2/0.1, approximately N ≃ 40/80 observations are needed. For “imperfect” observations, uncertainties in interpretation and sample biases become limiting factors. We show that LIFE and HWO aim for sufficiently large survey sizes to provide statistically meaningful estimates of habitable environments and life prevalence under these assumptions. However, robust conclusions require careful sample selection and high-confidence detection or exclusion of features in each observation.

The atmospheric characterization of a significant number of terrestrial exoplanets is a major goal of 21st century astrophysics. However, none of the currently adopted missions worldwide has the technical capabilities to achieve this goal. Here we present the LIFE mission concept, which addresses this issue by investigating the scientific potential and technological challenges of an ambitious mission employing a formation-flying nulling interferometer in space working at mid-infrared wavelengths. LIFE, in synergy with other planned future missions, will for the first time in human history enable us to understanding global biosignatures and planetary habitability in the context of the diversity of planetary systems. Breakthroughs in our understanding of the exoplanet population and relevant technologies justify the need, but also the feasibility, for future atmosphere characterization and life detection missions to investigate one of the most fundamental questions of humankind: how frequent and diverse are global biospheres in the galaxy?

Close-by Earth analogs and super-Earths are of primary importance because they will be preferential targets for the next generation of direct imaging instruments. Bright and close-by G-to-M type stars are preferential targets in radial velocity surveys to find Earth analogs. We present an analysis of the RV data of the star HD 20794, a target whose planetary system has been extensively debated in the literature. The broad time span of the observations makes it possible to find planets with signal semi-amplitudes below 1 m/s in the habitable zone. We monitored the system with ESPRESSO. We joined ESPRESSO data with the HARPS data, including archival data and new measurements from a recent program. We applied the post-processing pipeline YARARA to HARPS data to correct systematics, improve the quality of RV measurements, and mitigate the impact of stellar activity. Results. We confirm the presence of three planets, with periods of 18.3142 +/- 0.0022 d, 89.68 +/- 0.10 d, and 647.6 +/- 2.6 d, along with masses of 2.15 +/- 0.17 MEarth, 2.98 +/- 0.29 MEarth, and 5.82 +/- 0.57 MEarth respectively. For the outer planet, we find an eccentricity of 0.45 +/- 0.10, whereas the inner planets are compatible with circular orbits. The latter is likely to be a rocky planet in the habitable zone of HD 20794. From the analysis of activity indicators, we find evidence of a magnetic cycle with a period around 3000 d, along with evidence pointing to a rotation period around 39 d. We have determined the presence of a system of three planets orbiting the solar-type star HD 20794. This star is bright (V=4.34 mag) and close (d = 6.04 pc), and HD 20794 d resides in the stellar habitable zone, making this system a high-priority target for future atmospheric characterization with direct imaging facilities.

The ESA Voyage 2050 report (https://www.cosmos.esa.int/web/voyage-2050) names the “characterisation of temperate exoplanets in the mid-infrared, through a first spectrum of direct thermal emission from exoplanet atmospheres to better understand if they harbour truly habitable surface conditions” as one of the top three priorities for future large-scale missions. This is the goal of the mission concept LIFE - Large Interferometer For Exoplanets (https://life-space-mission.com/). The LIFE initiative is currently investigating the scientific potential and technological challenges of an ambitious mission using a formation-flying nulling interferometer in space operating at mid-infrared wavelengths. The poster will outline the basic concept of the LIFE mission and present predictions for the discovery yield of exoplanets in our neighborhood as well as recent key results regarding the detectability of biosignatures and indicators of habitability.

Context: Warm, terrestrial exoplanets represent a key component in the exoplanet population when exploring the diversity of planets and investigating the properties of potentially habitable worlds [1]. Subsequently, the LIFE Collaboration is presenting a mission concept for the Large Interferometer for Exoplanets (LIFE) capable of directly imaging the thermal emission of terrestrial exoplanets in the mid-infrared using the technique of nulling interferometry [2]. Since LIFE will explore the previously disfavored parameter-space of mature planets close to their host stars, it needs to spend 2.5 yrs of its 5 yrs mission on detecting previously inaccessible planets. This so-called search phase will provide the sample of exoplanets from which suitable targets for in-depth follow-up observations will be selected. The scientific success of the mission hinges on its capacity to observe a sufficiently large sample of potentially habitable worlds to allow for the formulation of statistically significant results regarding the existence of life in the Universe. These kinds of results are further needed to constrain exoplanet populations and make results comparable to theoretical predictions. Aim: We aim to predict the exoplanet yield of the LIFE mission search phase in total numbers of detected planets and properties of the planetary sample. Our predictions are based on the assumption of the measurement principle of LIFE and all pertinent astrophysical sources of noise (stellar leakage, local zodiacal, and exozodiacal dust) degrading the quality of the measurements. While our current simulations only account for random background noise, we aim to include an implementation of instrumental noise sources once a preliminary mission design has been developed. Methods: The prediction of the search phase yield can be subdivided into three steps. First, a catalog of nearby stars [2] is populated with synthetic planets drawn based on Kepler statistics [3]. For each of these planets, a nulling inteferometric observation with LIFE is simulated under the assumption of the astrophysical noise contributions mentioned above. Lastly, the time available in the search phase is distributed among the targets such that the total number of detected planets is maximised. Results: We predict that LIFE will be able to detect roughly 230 terrestrial exoplanets within the 2.5 yrs search phase. Figure 1 shows the distribution of this sample in the planet radius and insolation plane. LIFE will be most efficient in finding warm, super-Earth-sized planets (as defined in [4]), but enables detections ranging from 0.5-6 R⊕ in radius and 10-1-103 S⊕. We find that the exoplanet yield is a strong function of the mirror size and that the uncertainties are dominated by uncertainties in the underlying planet population. We show that the properties of the exoplanet sample do not only depend on the characteristics of the instrument, but furthermore on the distribution of the available observing time among stellar targets. Figure 2 demonstrates that a distribution optimized towards detecting planets in the habitable zone of their parent star (scenario 2) can increase the total number of these potentially habitable planets by ~60%. However, such optimizations come at the cost of a reduced number of detections in other planet categories. Depending on the optimization scenario, 27-43 of the detected planets will reside in the empirical habitable zone [5] of their host stars. This is thought to be a sufficient number of planets to effectively constrain the ratio of terrestrial planets in the habitable zone which provide conditions for liquid water to exist on their surface [6]. Since a significant fraction of these planets will be around M-type stars, a discussion of the habitability potential in those conditions [7] needs to be revised with the help of JWST observations. The value that the LIFE mission will add to the sample of known exoplanets is significant. Figure 3 demonstrates how the detection capability of LIFE for terrestrial exoplanets reaches to significantly smaller planets, covering the region in parameters space occupied by the four terrestrial planets in the Solar System. We are able to demonstrate that in terms of number of detections, LIFE will provide a potential similar to that of the LUVOIR concept and superior to that of the HabEx concept. Lastly, we raise the following discussion point: We have shown that the number of predicted detections depends not only on the instrument performance, but also on the underlying synthetic exoplanet sample and the distribution of the observing time. Since the assumptions for the latter two points likely deviate between mission concepts, we reiterate a performance measure which can decouple and display the instrument performance. References:[1] Committee on Exoplanet Science Strategy: NASA Exoplanet Science Strategy, The National Academy of Sciences, 2018[2] LIFE Collaboration et al.: Large Interferometer For Exoplanets (LIFE): I. Improved exoplanet detection yield estimates for a large mid-infrared space-interferometer mission, arXiv, 2021[3] Kammerer, Jens, and Quanz, Sascha P.: Simulating the Exoplanet Yield of a Space-Based Mid-Infrared Interferometer Based on Kepler Statistics, Astronomy and Astrophysics, Vol. 609, 2018[4] Kopparapu, Ravi Kumar, et al.: Exoplanet Classification and Yield Estimates for Direct Imaging Missions, The Astrophysical Journal, Vol. 856, 2018[5] Kopparapu, Ravi Kumar, et al.: Habitable Zones around Main-Sequence Stars: Dependence on Planetary Mass, The Astrophysical Journal Letters, Vol. 787, 2014[6] Quanz, Sascha P., et al.: Atmospheric Characterization of Terrestrial Exoplanets in the Mid-Infrared: Biosignatures, Habitability & Diversity, ESA Voyage 2050 White Paper, arXiv, 2019[7] Shields, Aomawa L., et al.: The habitability of planets orbiting M-dwarf stars, Physics Reports, Vol. 663, 2

Summary: Studying the atmospheres of a statistically significant number of rocky, terrestrial exoplanets -- including the search for habitable and potentially inhabited planets -- is one of the major goals of exoplanetary science and possibly the most challenging question in 21st century astrophysics. However, despite being at the top of the agenda of all major space agencies and ground-based observatories, none of the currently planned projects or missions worldwide has the technical capabilities to achieve this goal. In this contribution we present new results from the LIFE Mission initiative, which addresses this issue by investigating the scientific potential and technological challenges of an ambitious mission employing a formation-flying nulling interferometer in space working at mid-infrared wavelengths [1,2,3]. We will focus on new yield estimates and the release of our simulator software as well as improvements on our input catalog. Advances in our knowledge of the exoplanet population as well as significant progress in relevant technologies justify the need, but also the feasibility for a future mission like LIFE to investigate one of the most fundamental questions of mankind: How unique is the phenomenon we call life in the universe?Artist's impression of the LIFE concept.Context: One of the long-term objectives of exoplanet research is the investigation of the atmospheric properties for a large number (~100) of terrestrial exoplanets. This is partially driven by the idea to search for and identify potential biosignatures. But such a statistically significant dataset is - in a more general sense - invaluable for understanding the diversity of planetary bodies. While exoplanet science is omnipresent on the roadmaps of all major space agencies and ground-based observatories and first steps in this direction will be taken in the coming 10-15 years with funded or selected ground- and space-based projects and missions, none of them will be able to deliver such a comprehensive and consistent, big data set. An alternative to the mainly discussed large space-based coronographic missions or the starshade concept is to separate the light emitted by the planet from that of its host star by means of an interferometer. In [4] for example we showed that Proxima Centauri b is a prefectly suited target for a space-based nulling interferometer with relatively small apertures.LIFE is a project initiated in Europe with the goal to consolidate various efforts and define a roadmap that eventually leads to the launch of a large, space-based MIR nulling interferometer. This mission should be able to investigate the atmospheric properties of a large sample of (primarily) terrestrial exoplanets. Centered around clear and ambitious scientific objectives the project will define the relevant science and technical requirements. The status of key technologies will be re-assessed and further technology development will be coordinated. LIFE is based on the heritage of ESA/Darwin and NASA/TPF-I, but significant advances in our understanding of exoplanets and newly available technologies will be taken into account in the LIFE mission concept.New Results and Progress: In a previously presented work [5], we used Monte Carlo simulations to demonstrate that a MIR space-based nulling interferometer like LIFE, could yield at least as many exoplanet detections as a large, single aperture optical/NIR telescope. Here we will present an elaborate update on this first study. A key aspect that we have investigated more closely is the specific treatment of stellar leakage and exozodical light in our simulations. We also had a critical look at the stellar input sample and its properties with a specific focus on multiplicity. The details and exact number of planets depend on the assumed technical specifications and the underlying exoplanet populations, but from an exoplanet science perspective such an interferometer should be considered an attractive mission concept, at least complementary if not superior to an optical/NIR mission.We will present our newest data simulator that incorporates various telescope sizes and a new noise model that takes into account all astrophysical noise sources. This enables us to systematically study our mission requirements in order to optimize our observing strategy. As most detected planets will be warmer than Earth, going as short as 3 μm seems useful; at the red end 25 μm seems sufficient. This wavelength range features absorption bands of CO2, H2O, O3, CH4, (N2)2, and N2O and also contains windows to probe surface emission. The spectral resolution (R ~ 20-100) is very likely to be driven by the need to avoid line contamination of certain molecules such as N2O and CO2 around 4.15 μm, as well as CH4 and also N2O and H2O between 7.7 and 8 μm. In another submission to this conference (Konrad et al. 2020) we discuss more details on our progress in spectral retrieval.Future steps: Our analysis also shows that getting a better handle on the overall planet statistics is crucial for planning larger future missions. We are therefore working on a detailed simulation of the impact on scheduling for the survey and characterisation phases of the LIFE mission. In this context we are also currently investigating modern machine learning methods that crucial to scale up front to end simulations of the full LIFE survey. This in turn will not only inform aforementioned scheduling consideration but also help to define sensitivity, wavelength coverage and spectral resolution requirements on the technology side.References: [1] Quanz, S. P., Kammerer, J., Defrère, D., et al. 2018, Optical and Infrared Interferometry and Imaging VI, 10701,107011I. [2] Defrère, D., Léger, A., Absil, O., et al. 2018, Experimental Astronomy, 46, 543. [3] Quanz,S. P.,et al. 2019. , arXiv e-prints arXiv:1908.01316. [4] Defrère, D., Léger, A., Absil, O., et al. 2018, Optical and Infrared Interferometry and Imaging VI, 10701,107011H. [5] Kammerer, J., & Quanz, S. P. 2018, A&A, 609, A4

We present the database of potential targets for the Large Interferometer For Exoplanets (LIFE), a space-based mid-infrared nulling interferometer mission proposed for the Voyage 2050 science program of the European Space Agency (ESA). The database features stars, their planets and disks, main astrophysical parameters, and ancillary observations. It allows users to create target lists based on various criteria to predict, for instance, exoplanet detection yields for the LIFE mission. As such, it enables mission design trade-offs, provides context for the analysis of data obtained by LIFE, and flags critical missing data. Work on the database is in progress, but given its relevance to LIFE and other space missions, including the Habitable Worlds Observatory (HWO), we present its main features here. A preliminary version of the LIFE database is publicly available on the German Astrophysical Virtual Observatory (GAVO).

Context. Inferring atmospheric properties of exoplanets from observed spectra is key to understanding their formation, evolution, and habitability. Since traditional Bayesian approaches to atmospheric retrieval (e.g., nested sampling) are computationally expensive, a growing number of machine learning (ML) methods such as neural posterior estimation (NPE) have been proposed. Aims. We seek to make ML-based atmospheric retrieval (1) more reliable and accurate with verified results, and (2) more flexible with respect to the underlying neural networks and the choice of the assumed noise models. Methods. First, we adopted flow matching posterior estimation (FMPE) as a new ML approach to atmospheric retrieval. FMPE maintains many advantages of NPE, but provides greater architectural flexibility and scalability. Second, we used importance sampling (IS) to verify and correct ML results, and to compute an estimate of the Bayesian evidence. Third, we conditioned our ML models on the assumed noise level of a spectrum (i.e., error bars), and thus made them adaptable to different noise models. Results. Both our noise-level-conditional FMPE and NPE models perform on a par with nested sampling across a range of noise levels when tested on simulated data. FMPE trains about three times faster than NPE and yields higher IS efficiencies. IS successfully corrects inaccurate ML results, identifies model failures via low efficiencies, and provides accurate estimates of the Bayesian evidence. Conclusions. FMPE is a powerful alternative to NPE for fast, amortized, and parallelizable atmospheric retrieval. IS can verify results, helping to build confidence in ML-based approaches, while also facilitating model comparison via the evidence ratio. Noise level conditioning allows design studies for future instruments to be scaled up; for example, in terms of the range of signal-to-noise ratios.

The sample of planet-forming disks observed by high-contrast imaging campaigns over the last decade is mature enough to enable the demographical analysis of individual star-forming regions. We present the full census of Taurus sources with VLT/SPHERE polarimetric images available. The whole sample sums up to 43 targets (of which 31 have not been previously published) corresponding to one-fifth of the Class II population in Taurus and about half of such objects that are observable. A large fraction of the sample is apparently made up of isolated faint disks (equally divided between small and large self-shadowed disks). Ambient signal is visible in about one-third of the sample. This probes the interaction with the environment and with companions or the outflow activity of the system. The central portion of the Taurus region almost exclusively hosts faint disks, while the periphery also hosts bright disks interacting with their surroundings. The few bright disks are found around apparently older stars. The overall picture is that the Taurus region is in an early evolutionary stage of planet formation. Yet, some objects are discussed individually, as in an intermediate or exceptional stage of the disk evolution. This census provides a first benchmark for the comparison of the disk populations in different star forming regions.

In this study, we treat Earth as an exoplanet and investigate our home planet by means of a potential future mid-infrared space mission called the Large Interferometer For Exoplanets (LIFE). We combine thermal spectra from an empirical data set of disk-integrated Earth observations with a noise model for LIFE to create mock observations. We apply a state-of-the-art atmospheric retrieval framework to characterize the planet, assess the potential for detecting the known bioindicators, and investigate the impact of viewing geometry and seasonality on the characterization. Our key findings reveal that we are observing a temperate habitable planet with significant abundances of CO _2 , H _2 O, O _3 , and CH _4 . Seasonal variations in the surface and equilibrium temperature, as well as in the Bond albedo, are detectable. Furthermore, the viewing geometry and the spatially and temporally unresolved nature of our observations only have a minor impact on the characterization. Additionally, Earth’s variable abundance profiles and patchy cloud coverage can bias retrieval results for the atmospheric structure and trace-gas abundances. Lastly, the limited extent of Earth’s seasonal variations in biosignature abundances makes the direct detection of its biosphere through atmospheric seasonality unlikely. Our results suggest that LIFE could correctly identify Earth as a planet where life could thrive, with detectable levels of bioindicators, a temperate climate, and surface conditions allowing liquid surface water. Even if atmospheric seasonality is not easily observed, our study demonstrates that next generation space missions can assess whether nearby temperate terrestrial exoplanets are habitable or even inhabited.

The Large Interferometer For Exoplanets (LIFE) is a proposed space-based mid-infrared nulling interferometer featuring an array of formation-flying collectors and a central beam combiner. Its primary objective is the direct detection of dozens of temperate, terrestrial exoplanets and the investigation of their atmospheres to understand their composition and identify potential biosignatures. To get a realistic performance estimate of LIFE and derive technical requirements, a comprehensive understanding of all major noise sources impacting the mission performance is essential. Previous studies on the performance of LIFE have focused on fundamental noise from astrophysical sources and assumed the impact of instrumental noise to be non-dominant. Here, we report on our ongoing effort to explicitly model instrumental noise for LIFE. We consider two different methods: one providing a numerical solution by explicitly propagating the instability-induced errors in Monte Carlo simulations, and one providing an analytical solution using a second-order approximation of the leakage from instrumental instability noise. We give an overview of the two methods and argue in favor of the numerical method to support the efforts of the LIFE initiative in the ongoing concept phase, due to its flexibility for different observatory architectures, its fidelity in modeling the correlation of errors and fewer limitations concerning the parameter space of potential errors sources.

This study aims to identify exemplary science cases for observing N$_2$O, CH$_3$Cl, and CH$_3$Br in exoplanet atmospheres at abundances consistent with biogenic production using a space-based mid-infrared nulling interferometric observatory, such as the LIFE (Large Interferometer For Exoplanets) mission concept. We use a set of scenarios derived from chemical kinetics models that simulate the atmospheric response of varied levels of biogenic production of N$_2$O, CH$_3$Cl and CH$_3$Br in O$_2$-rich terrestrial planet atmospheres to produce forward models for our LIFEsim observation simulator software. In addition we demonstrate the connection to retrievals for selected cases. We use the results to derive observation times needed for the detection of these scenarios and apply them to define science requirements for the mission. Our analysis shows that in order to detect relevant abundances with a mission like LIFE in it's current baseline setup, we require: (i) only a few days of observation time for certain very near-by "Golden Target" scenarios, which also motivate future studies of "spectral-temporal" observations (ii) $\sim$10 days in certain standard scenarios such as temperate, terrestrial planets around M star hosts at 5 pc, (iii) $\sim$50 - 100 days in the most challenging but still feasible cases, such as an Earth twin at 5pc. A few cases for very low fluxes around specific host stars are not detectable. In summary, abundances of these capstone biosignatures are detectable at plausible biological production fluxes for most cases examined and for a significant number of potential targets.