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Open research questions in Astro and Planetary Science

35 unresolved questions extracted from the limitations and future-work sections of 501 Astro and Planetary Science papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • Only KELT-20 b clearly prefers the presence of OH features, but the OH abundance constraints are limited by the low opacity of this species in the K band. Our efforts to constrain C/O ratios were limited by the impact of thermal dissociation and the sensitivity of the C/O ratio inference to the exact vertical mixing treatment.

    Atmospheric Characterization of Six Ultrahot Jupiters from <i>K</i> -band High-resolution Spectroscopy · 2026 · DOI

  • The Uranian moons Ariel, Umbriel, Titania, and Oberon are enriched in CO2 mixed with CO, but the origin(s) of these carbon oxides, be they primarily native or radiolytic, remains uncertain.

    Tracing the source of carbon oxides on the large moons of Uranus · 2026

  • This decoupling emerges directly from the simulation data, showing that a single characteristic impact velocity is insufficient to represent the full dynamical interactions. The results from all three figures establish that mean velocities are insufficient to characterize dust–planet interactions. Together, these findings demonstrate that mean impact velocities are insufficient to characterize dust–planet interactions; the full velocity distribution must be considered when assessing impact-driven surface modification, exosphere generation, and volatile delivery across the terrestrial planets.

    Modeling and Analysis of Main-belt Asteroidal Dust Flux and Velocity Distribution at Inner Planets · 2026 · DOI

  • Our derived photometric parameters reproduce established correlations from both targeted studies and surveys using sparse data: strong G1 − G2 anti-correlation, albedo dependencies, and clear taxonomic separation in the G1, G2 parameter space.

    Single-Apparition Phase Curves from ATLAS survey: Photometric Parameter Determination · 2026 · DOI

  • Through this work we have presented new physical and astro- metric constraints derived from stellar occultations for 101 target asteroid systems observed between October 2023 and February 2026. This study represents the first dedicated effort targeting intermediate-size objects in the 5–100 km range through a co- ordinated occultation strategy, rather than isolated single-object campaigns. In particular, the occultation of (5044) Shestaka on October 23, 2024, gathered an unprecedented number of partic- 100101102103Diameter (km)05101520253035404550Total number of chordsArchived Occultations database (Herald+2020)GaiaMoons Occultations (this work)(5044) Shestaka(1127) Mimi(35420) 1998AG6(36882) 2000SW155 A&A proofs: manuscript no. output via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/ A+A/.. Additional data not included in this article but part of the overall Gaiamoons occultation observation dataset will be avail- able in the thesis manuscript of the corresponding author that will be published in late 2026. aw data of this study are available from the corresponding author upon request. Acknowledgements. This work was supported by the project GaiaMoons of the Agence Nationale de Recherche (France), grant ANR-22-CE490002. The GaiaMoons team gratefully acknowledges the amateur communities of IOTA, IOTA/ES, IOTA/EA, TTOA, and Planoccult for their essential support, ded- ication, and significant contributions to this work. The properties of Solar System Object are from the service SsODNet.ssoCard of the Space Service (SE-OP) of Laboratoire Temps Espace at Paris Observatory through its So- lar System Portal (https://ssp.imcce.fr) (Berthier et al. 2023) with the python library rocks (https://github.com/maxmahlke/rocks). We made use of Astropy, a community-developed core Python package for Astron- omy (Astropy Collaboration et al. 2013). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www. cosmos.esa.int/Gaia), processed by the Gaia Data Processing and Anal- ysis Consortium (DPAC, https://www.cosmos.esa.int/web/Gaia/dpac/ consortium). The authors would like to thank the Action Pluriannuelle In- citative (API) Pro-Am initiated and supported by Paris Observatory in the ROADIES program context. Z. Liu and D. Hestroffer thank the Academie Spatial program for their support. Part of observations were funded by the Scientific Research Projects Coordination Unit of Istanbul University with project numbers: BAP-3685 and FBG-2017-23943. Felipe Braga-Ribas ac- knowledges CNPq grant 316604/2023-2 and the financial support of the NAPI “Fenômenos Extremos do Universo” of Fundação de Apoio à Ciência, Tecnologia e Inovação do Paraná. M.A. thanks grants CNPq 427700/2018- 3, 310683/2017-3, and 473002/2013-2, and FAPERJ E-26/210.705/2024. Y. Kilic, J.L. Ortiz, N. Morales and P. Santos-Sanz acknowledge financial support from the Severo Ochoa grant CEX2021-001131-S funded by MI- CIU/AEI/10.13039/501100011033. P. Santos-Sanz and Y. Kilic acknowledge fi- nancial support from the Spanish I+D+i project PID2022-139555NB-I00 (TNO- JWST) funded by MCIN/AEI/10.13039/501100011033. TUG100 Telescope at the Antalya TUG Site of the Türkiye National Observatories has been utilised, and we express our gratitude for the support provided by the Türkiye National Observatories and all its staff. The authors would like to thank the following ob- servers who participated and provided data for the events: R. Leiva, A. Ossola, A. Catapano, B. Lade, R. Prentice, S. Whitehurst, E. Goni, E. Namur Neto, J. Delin- cak, J. Talbot, J. A. Berlanga, J. Collada Barcena, K. Harrison, M. Skrutskie, M. Gutekunst, N. Karaman, N. Wakefield, V. Cucchiaro, X. Dupont, T. Legault, S. Kidd, P. Le Cam, J.-N. Ferrier, G. Vanwalleghem, E. Vauthrin, F. Thill, B. Lott, D. Tamonis, and A. Maury.

    Detection and characterisation of binary asteroid candidates through stellar occultations · 2026 · DOI

  • The grainy and jumping migration scenarios proposed for Neptune (Nesvorný & Vokrouhlický 2016; Nesvorný & Morbidelli 2012) are mentioned as alternative to smooth exponential migration, but the paper provides no numerical simulations testing how discontinuous or episodic migration events affect capture efficiency and final population distributions in individual mean motion resonances.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • The primordial planetesimal disk is inferred to extend to 60-70 au based on order-of-magnitude agreement between theory and observations for MMRs between 1:2 and 1:4, but this inference lacks direct observational constraints on the actual density profile and sharp density drop-off characteristics at these distances during the late stages of giant planet migration.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • The discrepancy between theoretical predictions and observations for the 1:2 MMR is attributed to poorer resonant island stability and fragmentation at low inclinations, but the paper lacks direct frequency analysis calculations showing the eigenfrequency differences and dynamical timescale comparisons between the 1:2 and 2:3 MMRs under the same initial conditions.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • The exponential migration model presented assumes that planetesimal density and eccentricity excitation (σe) are spatially uniform, but Equation 6 is noted to require extension when these parameters vary as functions of semimajor axis. The paper does not provide numerical implementations or results for how differential planetesimal density profiles across the primordial disk affect capture probabilities in different Neptune resonances.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • The distant mean motion resonances beyond the 1:4 MMR (particularly the 1:6 MMR and others in that region) currently lack observational data and population estimates. The paper identifies that resonant sticking effects may dominate over Neptune migration capture in these regions, but no simulations directly compare capture predictions from migration-based mechanisms versus resonant sticking mechanisms at these remote semimajor axes.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • The 3:4 and 4:5 mean motion resonances interior to the 1:2 MMR show theoretical predictions that consistently exceed observational values by more than the confidence intervals, yet the paper lacks specific dynamical stability analysis quantifying how proximity to Neptune affects resonant island fragmentation and long-term stability timescales for these inner resonances compared to the 2:3 MMR.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • The constant migration rate model used for calculating capture into Neptune's mean motion resonances has not been validated against exponential decay migration patterns or grainy migration scenarios. The authors propose that their methodology can be extended to variable migration rates but provide only a preliminary exponential migration model example without numerical results comparing predicted populations against observations under these more realistic migration assumptions.

    Numerical estimation of the capture ability of Neptunian mean motion resonances · 2026 · DOI

  • However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information content of the data resulted in high sensitivity to the varying assumptions made in the treatment of instrument systematics and the atmospheric retrieval analysis 3–12 .

    A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b · 2023 · DOI

  • Moreover, these reflected objects are out-of-rank, that is, they have not yet been determined with respect to the ranks of xenolandscape formations, similarly formed due to the synergy of influences and interactions of different strengths, but genetically the same initial xenolandscape-forming factors of material and energy-field xenonaturals.

    Mercury's xenolandscapes · 2023 · DOI

  • They have been imaged at more than 285 unique locations from August 2018 (when the atmosphere was clearing as the PEDE decayed) to August 2019, about half (157) of which are locations where RSL have not been documented previously.

    Mars: Abundant Recurring Slope Lineae (RSL) Following the Planet‐Encircling Dust Event (PEDE) of 2018 · 2021 · DOI

  • Using the lightcurve inversion method, the combination of our lightcurves and the sparse data from ATLAS{HKO and ATLAS-MLO, we also found the sidereal period, indicating a retrograde rotation of the asteroid, with two possible mirrored pole solutions.

    The physical and dynamical characteristics of the asteroid 4940 Polenov · 2021 · DOI

  • **Causal Hypotheses:** The current evidence establishes spatial over-representation; determining whether this reflects early Holocene astronomical observation, deliberate geodetic design, environmental adaptation, or residual selection effects remains an open scientific question.

    A Geometric Derivation of the 47.1° Vector: Spatial Clustering and Early Holocene Obliquity Correlations · 2026 · DOI

  • Abstract There are many different theoretical explanations for the formation of high-density Mercury-like planets, but concrete evidence for any of these formation mechanisms remains elusive.

    The Maximum Density of a Collisionally-Produced Planet is A Function of its Mass and Orbital Period · 2026 · DOI

  • Nevertheless, embedding coupled magma-atmosphere models directly within Bayesian retrievals enables quantitative assessment of degeneracies and sensitivities, establishing a pathway for directly connecting atmospheric spectra to magma composition in this underexplored exoplanet regime.

    Coupling Magma–Ocean and Atmospheres in Spectral Retrievals of Sub-Neptunes · 2026 · DOI

  • Double-diffusive convection in the ``fuzzy'' cores of giant planets has been widely discussed as a mechanism for redistributing heavy elements, but its efficiency in evolutionary models remains uncertain.

    Self-Consistent Evolution Models Show Weak Double-Diffusive Mixing in Jupiter and Saturn · 2026

  • The early states of terrestrial planets are expected to be dominated by the thermal and rotational outcomes of giant impacts, but critical parameters that control internal processes, such as the pressures and temperatures of core formation, are not fully understood.

    Thermal and rotational effects of giant impacts during terrestrial planet accretion · 2026

  • There are limited data in the literature presenting Centaur colors in the SDSS filter system for a direct comparison with 450P.

    JWST and Gemini Observations of the Active Centaur 450P/LONEOS: Nucleus and Coma Characterizations · 2026 · DOI

  • The physical and geochemical differences between Earth and Mars provide fundamental constraints on terrestrial planet formation, yet a self-consistent framework linking dynamical and chemical aspects remains elusive.

    Coupling dynamical accretion and chemical differentiation: A unified framework for the diversity of Earth and Mars · 2026 · DOI

  • While secondary processes related to atmospheric entry and post-impact evolution are investigated, quantitative constraints on P-T-time paths during these processes are not fully established.

    A Petrographic and Micro-Analytical Framework for the Study and Classification of Meteorites · 2026 · DOI

  • The comparative framework among ordinary chondrites is developed but lacks systematic comparison with carbonaceous, enstatite, and achondritic meteorite groups.

    A Petrographic and Micro-Analytical Framework for the Study and Classification of Meteorites · 2026 · DOI

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35 open questions have been extracted from the limitations and future-work passages of 501 Astro and Planetary Science papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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