Earth and Planetary Astrophysics
The Limits of Tidal Circularization and Atmospheric Escape for Mini-Neptunes and Super-Earths: The Case of TOI-2257 b
M. K. A. Olohoy, Y. A. D. Gelani and R. Barnes
With a 35-day orbital period and $\sim$0.5 eccentricity, TOI-2257 b occupies a sparsely populated corner of transiting mini-Neptune parameter space and may lie near the orbital distance at which tidal and atmospheric escape process become negligible. To test this hypothesis, we performed simulations of the combined stellar, tidal, and atmospheric
evolution and confirmed that TOI-2257 b does lie near this boundary, regardless of whether it formed with or without a primordial hydrogen envelope. In the mini-Neptune scenario, we find that all cases retain an envelope of at least 0.02 M$_\oplus$ for 8 Gyr, but that the envelope mass can be halved if it was initially larger than 0.2 M$_\oplus$. We find that tidal
evolution only occurs for cases with initial envelope masses larger than 0.02 M$_\oplus$ because their radii are large enough to generate significant torques. In the super-Earth scenario, the
planet could lose $\sim$10 Earth ocean masses of surface water during the $\sim$75 Myr pre-main sequence and therefore could be habitable if it formed with $\gtrsim$2x Earth's surface water mass. The predicted tidal heating surface flux tends to be similar to Io, with no cases approaching the flux required to drive a runaway greenhouse. We find that if the
planet is rocky, then eccentricities larger than 0.62 today are strongly disfavored, implying that larger eccentricities could confirm the gaseous nature of the
planet. These results suggest that TOI-2257 b could provide valuable constraints on mini-Neptune properties and new insight into the radius valley shape as a function of eccentricity.
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Earth and Planetary Astrophysics
Paleo-heat flux estimates across Enceladus derived from flexural response of the ice shell
Chelsea Eakins, Francis Nimmo and Paul Schenk
Saturn's moon Enceladus has active plumes suggestive of locally high heat fluxes at present, and the present-day heating is reasonably well characterized. However, the moon's thermal history is not well understood. In this study, we model flexural deformation of chasmata and dorsae in various regions of Enceladus to find the effective elastic thickness of the ice shell and constrain temporal and spatial variations in heat flux. We find paleo-heat fluxes of 60-$\geq$350 mWm$^{-2}$, with most clustered around 125-200 mWm$^{-2}$. Present day measured heat fluxes at the South Polar Terrain (SPT) are comparable to our estimated paleo-heat fluxes in non-SPT regions. Our paleo-heat fluxes, however, are significantly higher than the corresponding present day heat fluxes for the same locations inferred from shell thickness maps. This suggests that regions outside the SPT experienced a past episode of heating (heat fluxes in excess of 100mWm$^{-2}$) followed by a cooling and thickening ice shell. A relatively constant paleo-heat flux for terrains of different ages (determined from crater densities) supports the "resonance locking" hypothesis of dissipation in Saturn and might imply a long-lived resonance between Enceladus and Dione. Our results suggest that Enceladus's tidal heating appears to have been consistent over time. Consistent peak heating at Enceladus could support a long-lived subsurface ocean, which has important consequences for astrobiology and the habitability of the outer solar system.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR
Chandra-JWST Probing the Effects of Moderate X-Ray Superflares on Protoplanetary Disks
Konstantin V. Getman, Kevin L. Luhman, Bayron Portilla-Revelo et al. (+17 more)
Powerful X-ray
flares from young
stars may rapidly alter the physical and chemical conditions of their
planet-forming disks, but direct observational tests remain scarce. We present a Chandra-JWST/NIRSpec study of infrared spectral variability associated with pre-main-sequence (PMS) X-ray
flares in the Orion Nebula. Combining six Chandra/ACIS-I observations with three NIRSpec-MOS visits, we analyze two-epoch spectra of 10 X-ray
Flare stars and 12 matched non-flaring Controls among 84 observed disk-bearing PMS
stars. We investigate three diagnostics: narrow 2.8-4.3 micron features, HI Br-alpha, and the CO fundamental band.
Flare stars show tentative evidence for relatively fewer variable narrow features at longer wavelengths than Controls, while feature incidence decreases strongly with projected distance from the dominant ionizing O
star Theta1 Ori C. Most classifiable features appear in absorption. These properties suggest that at least some features may arise in externally irradiated disk atmospheres and/or associated photoevaporative flows, with their apparent epoch-to-epoch variability potentially reflecting spatial sampling of such locally structured material rather than intrinsic temporal changes. Br-alpha behaves differently:
flare stars show systematically stronger variability and uniquely exhibit absorption-core profiles, suggesting control by magnetospheric
accretion and stellar
magnetic processes rather than disk irradiation. The CO fundamental band shows no significant
flare-associated variability, consistent with thermochemical models predicting weak responses to moderate X-ray superflares. This pilot study demonstrates the potential of coordinated Chandra-JWST observations to probe how young stellar
magnetic activity affects
planet-forming environments, motivating future monitoring to build larger superflare samples and extend them into the rare X-ray mega-
flare regime.
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All authors Konstantin V. Getman, Kevin L. Luhman, Bayron Portilla-Revelo, Christian Rab, Valentin Brunn, Eric D. Feigelson, Arjan Bik, Jan Forbrich, Jenny Frediani, Thomas J. Haworth, Charles J. Law, Marco Padovani, Maria Claudia Ramirez-Tannus, Andrew J. Winter, Vladimir S. Airapetian, L. Ilsedore Cleeves, Sergio A. Dzib, Michael A. Kuhn, Abygail R. Waggoner, Rens Waters
Earth and Planetary Astrophysics
Science-Driven Performance Requirements for UV Coronagraph Design: Implications for O$_3$ Detection in Earth-like Atmospheres
Amber V. Young, Giada Arney, Shawn Domagal-Goldman et al. (+6 more)
Detecting biosignatures on Earth-like
exoplanets from the Proterozoic era requires instrumentation capable of probing near-ultraviolet (NUV) spectral features, particularly ozone (\ce{O3}), which serves as an indirect proxy for molecular oxygen (\ce{O2}) when direct detection is challenging. Using a combination of photochemical-
climate modeling and atmospheric
retrieval simulations, we quantify fiducial instrument performance requirements for robust \ce{O3} detection and assess the risk of spectral false positives from sulfur dioxide (\ce{SO2}). Our analysis demonstrates the \ce{O3} abundances for Proterozoic Earth-like
planets with \ce{O2} as low as 0.1% the present atmospheric level, can be constrained to within an order of magnitude at 1\,$\sigma$ confidence using three adjacent photometric bandpasses at a signal-to-noise ratio of 10 at 0.366\,$\upmu$m, each with a 15% width, and a short wavelength cutoff for those observations near 0.26\,$\upmu$m. The self-consistent steady state atmospheric modeling results show that \ce{SO2} buildup is difficult in a habitable environment with appreciable amounts of water vapor in its atmosphere and would require volcanic outgassing rates at least two orders of magnitude above present-day Earth to reach surface abundance levels comparable to Proterozoic Earth-like abundances of \ce{O3}. Even under these high \ce{SO2} flux scenarios, \ce{SO2} remains largely unconstrained with the recommended observational configuration, reinforcing the need for NUV coverage in coronagraphic instruments. Our findings support the inclusion of UV-optimized optics and detectors on the Habitable Worlds Observatory (HWO) to enable biosignature detection strategies sensitive to atmospheric conditions across key phases of Earth's geological history.
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All authors Amber V. Young, Giada Arney, Shawn Domagal-Goldman, Tyler D. Robinson, Roser Juanola-Parramon, Christopher Stark, Renyu Hu, Armen Tokadjian, Mario Damiano
Earth and Planetary Astrophysics
Thermodynamically consistent equation of state tables for use in giant planet and brown dwarf interior modeling
Emily Sandford and Yamila Miguel
Equation of state (EOS) tables used in giant
planet modeling exhibit regions of strong thermodynamic inconsistency, or disobedience to the first law of thermodynamics. These generally result from smooth interpolation over physical discontinuities or between thermodynamic sub-domains governed by different physical models. The effect of thermodynamic inconsistency on structure models of
planets evolved with these EOS has never been studied in detail, although it is understood to introduce spurious sources or sinks of energy or
entropy in the models, leading to inaccuracies. Here, we present a method for improving the thermodynamic consistency of an existing EOS table, based on constructing a Helmholtz free energy $F(\rho,T)$ covering the EOS domain and deriving all the other necessary EOS quantities from it. This method produces EOS tables with roughly thousandfold better thermodynamic consistency across the EOS domain of interest, as quantified by three thermodynamic consistency metrics derived from the first law. We also present a controlled experiment comparing giant
planet models evolved with MESA using the original EOS and the $F$-derived, thermodynamically consistent versions, and find that the models can differ by up to $5\%$ in radius at an age of 5 Gyr, and by up to $25\%$ in luminosity at earlier stages of
evolution; thermodynamic consistency is thus an especially important consideration for characterising young directly imaged
planets. We present the $F$-derived, thermodynamically consistent versions of the tables for download at \href{https://doi.org/10.5281/zenodo.21103561}{https://doi.org/10.5281/zenodo.21103561}, along with example MESA inlists to reproduce our
evolution models.
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Earth and Planetary Astrophysics
Simulations of the Evolving Ozone Layer: Implications for the Early Earth, Exoplanets, and the Search For Life
Akhil Kumar and Gregory J. Cooke
Over 4 billion years, Earth's atmosphere has been transformed from a composition devoid of molecular oxygen (O$_2$) to one where O$_2$ is now 21% of our modern atmosphere by volume. With high quantities of O$_2$, an ozone (O$_3$) layer can form and partially shield the surface from biologically harmful ultraviolet radiation (UV). The
evolution of the O$_3$ layer has previously been simulated under the modern Sun by independent groups with separate models. Here, we present simulations of Earth's atmosphere from four open-source one-dimensional (1D) photochemical models and a 3D chemistry-
climate model, focussing on O$_3$. We find that the O$_3$ layer thickness exhibits a clear deviation between the 1D models and the 3D model due to several factors, including treatments of O$_2$ photolysis, chemical networks, H$_2$O microphysics and 3D transport. We find that 1D models introduce a bias for unobserved
climate states and show how these biases may propagate to calculations of biological UV damage and surface habitability. We show that when applied to specific
exoplanet atmospheres, these discrepancies can become more pronounced, propagating through to observational predictions for the next generation of
telescopes, such as HWO and LIFE, that will search for habitable and inhabited
exoplanets.
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Earth and Planetary Astrophysics
Peering into the Midplane of the DM Tau Disk using N2H+ and DCO+
Amina Diop, Kevin Flaherty, Chunhua Qi et al. (+7 more)
Planets form in the midplanes of protoplanetary disks, thus investigating the properties of the midplane region can shed light on the physical and chemical processes governing the
evolution of planetary systems. In this work, we study the conditions near the midplane of the disk around DM Tau using 0."3 (~43 au) ALMA observations of N2H+ (J = 3 - 2) and DCO+ (J = 4 - 3). The radial profiles reveal that DCO+ is centrally peaked, with a depression near 120 au, while N2H+ exhibits a central depression and a peak near 100 au. In addition, both molecules display extended emission out to 400 au. Using parametric models to interpret our observations, we note that a fiducial model based on CO-derived parameters captures the features within 200 au, but fails to reproduce the outer disk emission. We explore various mechanisms that could account for this extended emission and conclude that it is best reproduced by an increased external UV penetration and
cosmic ray/X-ray ionization rate, possibly enhanced by radial drift. These processes affect the precursors of N2H+ and DCO+ : increased UV leads to the photodesorption of CO and N2, while ionization enhances H3+ abundance. Besides, the observed N2H+ and DCO+ features are broadly consistent with previous CO snowline constraints, but can also be shaped by processes such as ionization, CO depletion, and multiple chemical pathways. Thus, using these molecular ions as robust CO snowline tracers requires additional constraints from complementary molecular tracers and detailed chemical modeling.
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All authors Amina Diop, Kevin Flaherty, Chunhua Qi, Ilse Cleeves, A. Meredith Hughes, Agnes Kospal, Sean Andrews, David J. Wilner, Jacob B. Simon, Deryl E. Long
Earth and Planetary Astrophysics
A Spatial Map of the Atmospheric Limb of a Hot Jupiter
Lili Alderson, Hannah R. Wakeford, David Grant et al. (+18 more)
Planets are inherently three-dimensional objects shaped by their thermal structure and dynamics. Observations of transiting
exoplanets have begun to uncover this three-dimensional nature, with JWST measuring their dayside atmosphere structure with eclipse mapping, and exploring spectroscopic asymmetries in the limbs of
planets during transit. We apply the novel mapping method of transmission strings to the hot Jupiter WASP-17b. With this method, we are not only able to extract hemispheric limb asymmetries from east-to-west, but can map equator-to-pole variations around the transmitting atmosphere as a function of angle, spanning 0.6-12$\mu$m. We find a clear transition in the thermal scale height around the limb of the atmosphere, with a $\sim$650K temperature difference between the morning (T=858$^{+434}_{-233}$K) and evening (T=1522$^{+116}_{-114}$K). These results are consistent with both nightside emission and dayside eclipse mapping measurements, and represent a fully comprehensive set of observations for a transiting
exoplanet. We are also able to constrain the abundances of H$_2$O and CO$_2$ to constant values around the limb, providing observational constraints to results from global circulation models. The transmission string technique combined with the outstanding observability of WASP-17b pushes the study of
exoplanet atmospheres further into a three-dimensional understanding of hot Jupiter dynamics and chemistry
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All authors Lili Alderson, Hannah R. Wakeford, David Grant, Nikole K. Lewis, Avinash Verma, Jayesh Goyal, Mark Hammond, Daniel Valentine, Natalie H. Allen, Ana Glidden, Amélie Gressier, Jingcheng Huang, Maura Lally, Dana R. Louie, Jacob Lustig-Yaeger, Cathal Maguire, Elijah Mullens, Kristen S. Sotzen, Jeff A. Valenti, Roeland P. van der Marel, Tiffany Kataria
Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR
Star spots mimic the proposed abundance signatures of planet formation
Andrew R. Casey, Megan Bedell, Adam Wheeler et al. (+2 more)
Trends with stellar elemental abundances and condensation temperature have been proposed as a possible tracer of rocky
planet formation. Here we present an alternative explanation, where we show that stellar activity (
star spots) can also cause apparent abundance changes in refractory elements preferentially over volatile elements. This effect arises naturally from atomic physics: refractory (rocky; high-$T_c$) elements preferentially have low first-ionization potentials, with strong transitions that are most sensitive to the cooler, magnetically-perturbed spot conditions, making any spot-induced change in line strength correlated with $T_c$. We re-examine literature on Sun-like
stars in the Solar neighborhood and find that the $\log{R'_{HK}}$ stellar activity indicator is correlated with the so-called $T_c$ slope: the gradient of chemical abundances with respect to condensation temperature. Using 1D LTE Korg.jl simulations of the Sun with spots of varying size and contrast, we show that a wide range of spot configurations can manifest as abundance patterns that mimic a signal of abundance trends with condensation temperature. Finally, we conduct a line-by-line differential analysis of an ambient Solar spectrum relative to a Solar sunspot umbra to represent an extreme case, where we find that elements with high condensation temperature can show a factor of three (0.5 dex) increase. We discuss implications that stellar activity poses for precision spectroscopy, and provide some direction on how this effect might be mitigated.
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All authors Andrew R. Casey, Megan Bedell, Adam Wheeler, Julianne Dalcanton, Lily Zhao
Earth and Planetary Astrophysics
On the Orbital Evolution of Giant Planet Pair Embedded in a Gaseous Disk. III. simultaneous gas accretion and the final mass ratio
Bixuan Zhao, Hui Zhang, Yinhao Wu et al. (+1 more)
Recent
exoplanet surveys reveal a systematic trend in the mass ratios of giant
planet pairs ($> 30 M_\oplus$). Although the $M_{outer}/M_{inner}$ is broadly centered near unity, it exhibits a dependence on orbital separation. Compact pairs tend to have comparable masses, whereas widely separated pairs show outer-heavy configurations. To investigate the origin of this trend, we perform two-dimensional hydrodynamic simulations that couple gas
accretion and orbital migration of two giant
planet embryos with initial masses of $15-30 M_\oplus$. We explore the effects of disk viscosity, surface density slope, and initial mass ratio on the coupled
evolution of planetary growth and migration. We find that convergent migration drives the
planets to open a common gap, restructuring the gas flow. This configuration induces asymmetric
accretion, in which the inner
planet becomes starved as gap clearing suppresses its gas supply, while the outer
planet continues to accrete from the high-density region at the outer gap edge. Consequently, the system naturally evolves toward mass-ratio convergence, and in many cases produces an inversion of the initial core-mass hierarchy. We further show that migration outcomes are highly sensitive to initial conditions. Systems with initially more massive inner cores tend to diverge, whereas steeper surface density profiles and more massive outer cores favor convergent migration and subsequent resonance capture. Overall, our results identify common-gap-driven asymmetric
accretion as a unified mechanism linking orbital architecture, resonant capture, and the observed mass-ratio demographics of giant
planet pairs.
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All authors Bixuan Zhao, Hui Zhang, Yinhao Wu, Ya-Ping Li
Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR
The EBLM project - XX. Absolute dynamical masses of five low-mass eclipsing binaries, and an evaluation of mass estimation methods
Adam T. Stevenson, Yasmin T. Davis, Daniel Sebastian et al. (+8 more)
Eclipsing binaries consisting of a solar-type primary and an M dwarf secondary are key laboratories to study objects at the bottom of the main sequence. Fundamental parameters of such
stars have a direct impact upon exoplanetary studies, as searches for temperate Earth-sized
planets focus on M dwarf hosts. Eclipsing binaries are essential to measure these parameters. However for stellar masses $<$ 0.35 M$_\odot$ , few double-lined eclipsing systems are known. Thus, stellar
evolution models and empirical relations have had to rely on single-lined eclipsing binaries, for instance those from the EBLM project (Eclipsing Binary - Low Mass). Using high resolution spectroscopy to extract the weak signal of the secondary (flux ratio $<$ 1 per cent in the optical), we transform five more systems from single to double-lined, deriving absolute masses for both
stars. We then compare methods typically employed to estimate stellar masses for field
stars or single-lined binaries with the absolute dynamical masses we obtain, to assess their accuracy. Our results for SB1 and SB2 analyses are mostly consistent within 1-$\sigma$, though we identify a small systematic overestimation of SB1 masses derived from a combination of radial velocities and eclipse photometry. We show that the bias originates from primary radius overestimation during isochronal analysis, wherein the secondary light reduces photometric magnitudes and impacts the recovered radii by modifying the spectral energy distribution. With proper calibration, we can ensure the accuracy of using the full EBLM SB1 sample to constrain mass-radius-luminosity relationships for the smallest, yet most abundant,
stars in the
Galaxy
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All authors Adam T. Stevenson, Yasmin T. Davis, Daniel Sebastian, Amaury H. M. J. Triaud, Pierre F. L. Maxted, Alix V. Freckelton, Thomas A. Baycroft, Neda Heidari, David V. Martin, Nicola J. Miller, Alexandre Santerne
Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR
The EBLM Project - XIX. The absence of radius inflation in a homogeneous analysis of 66 Northern low-mass eclipsing binaries
Yasmin T. Davis, Amaury H.M.J. Triaud, David V. Martin et al. (+30 more)
Precise and accurate measurements of host
stars are crucial in the search for Earth-like
exoplanets, and M-dwarfs are favourable targets in this quest. Low-mass eclipsing binaries offer unique opportunities to empirically determine stellar masses and radii for low-mass
stars where stellar models may be systematically biased. We present results from the EBLM-North sample, the largest homogeneous study of low-mass eclipsing binaries with secondary characterisation yet, combining high-resolution and high-precision radial velocities from SOPHIE and TESS photometry. We measure a median precision for stellar companions of 4.2% in radius and 8.6% in mass within a sub-sample of 50 high-quality binaries, all with orbital periods $P_{\rm bin} > 5\,\rm days$. We compare our data to the Baraffe and MIST isochrones, and find our sample is statistically consistent with those models, producing reduced chi-squared values, $\chi^2_\nu\sim 1$. Our measured radius inflation is $0.3\pm 1.6$% indicating no statistically significant trend. We likewise detect no significant trend with
metallicity, despite having the precision to identify such a relationship. As such, our observations do not appear to follow the general
metallicity trend predicted in MIST. A $\chi_\nu^2 \sim 1$ indicates the scatter in our results is commensurate with our uncertainties alone. These results constrain the scope for unmodelled effects on the mass-radius relation that would produce radius deviations greater than 4.2%. However, our secondary effective temperatures do not reproduce this high level of agreement with the models, and we do not recover the predicted trends with
metallicity.
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All authors Yasmin T. Davis, Amaury H.M.J. Triaud, David V. Martin, Alix V. Freckelton, Jenni R. French, Adam T. Stevenson, Annelies Mortier, Karen Collins, Pierre F. L. Maxted, Daniel Sebastian, Aleyna Adamson, Thomas A. Baycroft, Isabelle Boisse, Gavin A. L. Coleman, Georgina Dransfield, Yilen Gómez Maqueo Chew, Leslie Hebb, Neda Heidari, Vedad Kunovac, James McCormac, Nikki J. Miller, Richard Nelson, Martin Nielsen, Alexandre Santerne, Madison G. Scott, Owen Scutt, Alexis M. S. Smith, Matthew R. Standing, Amalie Stokholm, Matthew I. Swayne, Mathilde Timmermans, Peter J. Wheatley, Emma Willett
Earth and Planetary Astrophysics
3D Global Climate Simulations of Synthetic Mars Warming
Tom N. Landefeld and Harald Lesch
Artificial warming via engineered aerosols presents a novel pathway to bypass volatile scarcity on modern Mars. Utilizing the Generic Planetary
Climate Model, we evaluate the physical feasibility of aerosol-induced terraforming over a full Martian year (669 Sols). Unlike previous approaches that added aerosols to background dust or assumed continuous nanoparticle injection, we simulate the complete substitution of natural dust with a single-injection profile of radiatively active aluminium nanoparticles without continuous dumping. This tests whether initial infrared greenhouse forcing can overcome the severe ice-albedo cooling induced by a massive regional water-ice sheet ($3400 \text{ kg/m}^2$) localized in the Hellas Basin. Comparing this scenario against an unperturbed control run, we analyze surface temperature dynamics, sublimation fluxes, and water vapour concentration. Our 3D global
climate simulations quantify the radiative-dynamical feedback thresholds and determine whether engineered aerosol forcing can trigger a self-sustaining water-vapour greenhouse effect or remains fundamentally limited by regional ice-albedo suppression in Hellas.
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Earth and Planetary Astrophysics
Physical characterization of Earth's quasi-satellite 2025 PN7
Grigori Fedorets, Zuri Gray, Mikael Granvik et al. (+1 more)
A hypothetical origin as lunar ejecta for Earth's quasi-satellites (QS) has gained initial support in recent years, but there is scarce photometric and/or spectroscopic data to support the premise due to the rare observational windows to obtain such data for these small objects. One of the key pieces of evidence supporting the lunar-origin hypothesis, the lunar-like, very red reflectance spectrum of QS (469219) Kamo'oalewa, was recently found to be flawed. We present reflectance spectroscopy of Earth's QS 2025~PN$_7$ obtained with FORS2 at UT1-Antu of the ESO Very Large
Telescope. This is only the second QS that has ever been characterized, the first being (469219) Kamo'oalewa, the sample-return target of the Tianwen-2 mission. Our results indicate that 2025~PN$_7$ exhibits a near-solar, flat visual spectrum, most consistent with the B-type in the Bus-DeMeo taxonomy. Our results therefore still support an asteroid-belt origin for most of Earth's QSs. The lunar-ejecta hypothesis can only be formally rejected with a larger sample of spectroscopically characterized QSs.
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All authors Grigori Fedorets, Zuri Gray, Mikael Granvik, Eric MacLennan
Earth and Planetary Astrophysics
Radiation limits on amino acid preservation and chiral measurement at Oxia Planum
Dimitra Atri
Amino acid enantiomeric excess (EE) is a potential biosignature, but its measurement requires sufficient surviving material as well as preserved chirality. We derive a criterion that separates abundance-limited from racemization-limited preservation and apply it to the Mars Organic Molecule Analyzer (MOMA) on the ExoMars Rosalind Franklin rover. The model combines
cosmic-ray and radiogenic doses with laboratory destruction kinetics and assumed ratios of interconversion to destruction rates. For an initially homochiral population of 1000~ppmw, the surviving EE is 58% or 25% when the total abundance reaches 1~ppmw for rate ratios of 0.04 or 0.10, respectively. This abundance criterion does not ensure that both enantiomers can be quantified. Applying provisional estimates of 1~ppmw per enantiomer and 10% EE, serine at 2~m requires initial concentrations of 340 and 960~ppmw after
cosmic-ray exposures of $10^{7}$ and $10^{8}$~yr, respectively, under transferred fused-silica–perchlorate kinetics and a 1.57-MGy radiogenic dose. These concentrations exceed measured meteoritic serine abundances, but do not predict the initial Oxia inventory. For organics retained in a closed host since deposition 3.9~Ga ago, the modeled radiogenic dose is 1.6–5.6~MGy across the adopted compositions. In the lower-dose case, drilling to 2~m reduces the total dose by only a factor of 1.5 after $10^{7}$~yr. The boundaries depend on mineral kinetics and organic residence time; they distinguish preserved chirality from a measurable excess.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR
A breath of fresh air: Oxygen enhancement from silicate sublimation during early protostellar evolution
F.J. Ballieux, M.K. McClure, Ł. Tychoniec et al. (+5 more)
Recently, an analog to the t = 0 moment of our Solar System's meteoritic record was identified for the first time around the Class I protostar HOPS-315. Crystalline silicates were found to recondense from SiO gas that cools as it advects upward from a hot thermostat region in the inner midplane. This t=0 moment may be associated with the formation of the first planetesimals in this disk. We explore whether HOPS-68, a Class I protostar with similar properties and system geometries, is engaged in such refractory recondensation as well. A detection of cooler gas-phase SiO in absorption above a hot disk midplane would allow us to achieve this goal, thanks to a previous detection of crystalline silicates. HOPS-68 was observed with the JWST MIRI and NIRSpec, showing multiple bands of molecular absorption. We use local thermal
equilibrium slab models to measure the temperature, column density, velocity, and radial location of these bands. The molecular absorption bands of gaseous SiO, H2O, CO2, and 13CO trace a warm molecular inversion layer (300-500 K) at mid-altitudes above the hot disk midplane from 0.3-16 AU, which is consistently blue-shifted with respect to the system velocity by 33-53 km/s. Atacama Large Millimeter/submillimeter Array (ALMA) observations of HOPS-68 kinematically resolve an SiO-rich jet and wind. We confirm that HOPS-68, like HOPS-315, is undergoing an epoch analogous to the t=0 moment in the Solar System's
planet formation timeline. The detected warm molecular layer traces the base of a disk wind, which carries sublimated material from the thermostat region near 2 AU up into the outer disk. As for HOPS-315, the molecular layer in the inner few AU of HOPS-68 is enhanced in bulk oxygen as a result of this sublimation. Since HOPS-68 is less evolved than HOPS-315, this may indicate a prolonged epoch in protostellar
evolution in which such oxygen enhancement occurs.
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All authors F.J. Ballieux, M.K. McClure, Ł. Tychoniec, L. Francis, A. Egliene, E.A. Bergin, M.R. Van 't Hoff, E.F. Van Dishoeck
Earth and Planetary Astrophysics
Rattling Resonant Chains with Dynamical Tides and Parametric Resonance Passage
Mohammad Farhat and Eugene Chiang
Close-in sub-Neptunes are born in mean-motion resonant chains that break apart on a timescale of $\sim$100 Myr. If the chains are first ”rattled” — have their free eccentricities excited to a few percent — then breaking occurs on the required timescale. We propose that chains are rattled by internal oscillations tidally driven by the
star in the innermost
planet. Unlike other proposals, there is no need to invoke any reservoir of planetesimals or external perturbers — the chain unravels from within. We develop a
Hamiltonian theory (and an accompanying toy model) which predicts a parametric instability whereby chain librations exponentially amplify when the tidal forcing frequency equals the sum of the internal mode frequency and the chain libration frequency. We also introduce a new eigenmode solver for rotating
planets, $\texttt{MAQAM}$, that in combination with the evolutionary code $\texttt{ORCHARD}$ enables us to track the frequency
evolution of pressure,
gravity, and inertial modes in cooling sub-Neptunes. Inertial modes in the gas envelope and fluid mantle can evolve to become momentarily parametrically resonant. Passage through a single parametric resonance can raise the free eccentricities in the chain to a few percent within a few tens of Myrs.
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Earth and Planetary Astrophysics
Size, atmospheric, and ring constraints on the large Kuiper belt object (55565) Aya from a stellar occultation
Ko Arimatsu, Hidekazu Hanayama, Satoshi Takita et al. (+3 more)
We aim to constrain the projected size,
geometric albedo, possible atmosphere, and possible ring material of the mid-sized trans-Neptunian object (55565) Aya from the stellar occultation of 2024 May 10 (UT). We observed the event from three Japanese sites with high-cadence optical imaging. We combined one positive occultation chord with an informative prior on the shadow centre derived from orbital and astrometric uncertainties, and inferred the body radius with
Bayesian Markov chain Monte Carlo modelling. We constrained a possible atmosphere by fitting refraction models for pure CH$_4$, N$_2$, and CO atmospheres to multi-band light curves, and searched for ring-like extinction signatures in unbinned and binned high-time-resolution photometry. We derive an equivalent radius, i.e., the radius of the circle fitted to the projected shadow, of $r=401^{+28}_{-40}$ km for Aya, corresponding to a
geometric albedo of $p_V=0.101^{+0.023}_{-0.013}$. This estimate is insensitive to the adopted ephemeris solution and is consistent with an ephemeris-independent analysis that makes no assumption about the position of the shadow centre. We obtain 3$\sigma$ upper limits on the atmospheric surface pressure of $p_0=60$, 90, and 80 nbar for pure CH$_4$, N$_2$, and CO compositions, respectively. No significant ring-like extinction is detected over projected distances of about 430-8060 km sampled by the three stations, and our most sensitive data exclude dense narrow features with apparent opacity $p'\gtrsim0.1$ and radial widths of a few kilometres or larger over $\sim3r$-$14r$. This is the first stellar occultation by Aya ever observed. In addition to constraining Aya's size and albedo and finding no ring-like extinction, we place a stringent atmospheric upper limit that supports diversity in atmospheric states among similarly sized trans-Neptunian objects.
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All authors Ko Arimatsu, Hidekazu Hanayama, Satoshi Takita, Fumi Yoshida, Tsutomu Hayamizu, Jun-ichi Watanabe
Earth and Planetary Astrophysics
Tracing the Influence of Distant companions on Exoplanetary Systems (TIDES) I. Highly Eccentric and Misaligned Binary Companions to Hot Jupiters
Marvin Morgan, Jerry W. Xuan, Brendan P. Bowler et al. (+9 more)
The origin of hot Jupiters remains an open question. A significant fraction reside in binary or multiple
star systems, suggesting that stellar companions may play an important role in shaping their present-day architectures. However, the orbits of the vast majority of these stellar companions remain poorly constrained, leaving their role in hot Jupiter
evolution an open question. We present the Tracing the Influence of Distant companions on Exoplanetary Systems (TIDES) survey, a campaign to map the orbits of stellar companions in systems hosting hot Jupiters to assess the extent to which binaries play a role in hot Jupiter formation and migration. Here, we introduce our survey design and new orbital fits for the first six systems in our sample—$\tau$ Boo, WASP-2, WASP-11, WASP-76, HAT-P-14, and HAT-P-16—by combining previous observations of the stellar companions together with new Keck/NIRC2 imaging and Keck/KPIC relative radial velocities. Among these six systems, the four with the most precisely constrained orbits exhibit high eccentricities ($e \geq 0.8$), and three of these systems also display significant
planet–binary misalignments ($\Delta i \geq 20^\circ$). This suggests the orbital properties of stellar companions to hot Jupiter host
stars are qualitatively different than field binaries and binaries hosting inner transiting small
planets. These orbital architectures are consistent with stellar companions shaping the
evolution of hot Jupiters, either through high-eccentricity migration or by participating in an earlier episode of dynamical
evolution that ultimately led to hot Jupiter formation. Continued orbital monitoring of the full sample will reveal whether outer stellar companions play a causal role in the
evolution of hot Jupiters.
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All authors Marvin Morgan, Jerry W. Xuan, Brendan P. Bowler, Kyle Franson, Michael C. Liu, Konstantin Batygin, Heather A. Knutson, Björn Benneke, Julianne Cronin, Luke Finnerty, Chih-Chun Hsu, Aniket Sanghi
Earth and Planetary Astrophysics
Dynamically Coupled Three-dimensional Cloud-Chemistry in Rapidly Rotating Irradiated Atmospheres: an Application to the Compact White Dwarf-Brown Dwarf system ZTFJ0038+2030
Yanhong Lai, Xianyu Tan, Daphne Broski-Laing et al. (+7 more)
Clouds and disequilibrium chemistry shape the observable properties of substellar and planetary atmospheres, and JWST time-resolved spectroscopy now enables direct tests of their three-dimensional structures. We present an update to the 3D atmospheric framework ADAM, coupling the dynamical core to a miniature kinetic chemistry scheme (mini-chem) and a saturation-relaxation tracer cloud module. Using this framework, we investigate the atmosphere of the brown dwarf orbiting the white dwarf ZTFJ0038+2030 in a 10-hour orbit. The brown dwarf receives stellar irradiation comparable to its internal heat flux, placing the atmosphere in a regime where the circulation is characterized by a standing Matsuno–Gill wave response and equatorial superrotation. Rapid rotation confines these structures closer to the equator, producing more symmetric broadband light curves with smaller hotspot offsets than canonical hot Jupiters, in agreement with recent JWST observations of this system. Although most species are globally homogenized, rapid rotation limits global-scale horizontal mixing and allows circulation-driven vertical transport to maintain strong CO and CO$_2$ inhomogeneities in the photosphere. These chemical inhomogeneities produce asymmetric phase curves in the CO and CO$_2$ absorption bands, which could qualitatively explain the observed CO$_2$ light-curve asymmetry. When clouds are included, Na$_2$S clouds dominate the photosphere and weaken the large-scale circulation, lowering photospheric CO and CO$_2$ abundances, while MgSiO$_3$ and Fe clouds rain out at deeper levels. Because the dominant Na$_2$S clouds reside mostly above the quench region, cloud-driven convection has limited impact on the quenched abundances, which are instead regulated mainly by large-scale circulation.
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All authors Yanhong Lai, Xianyu Tan, Daphne Broski-Laing, Yifan Zhou, Sarah L. Casewell, Jenni R. French, Elspeth K. H. Lee, Joshua D. Lothringer, Vivien Parmentier, Shang-Min Tsai
Earth and Planetary Astrophysics
Experimental evidence for physical alteration of fine regolith on near-Sun asteroids
Jooyeon Geem, Mikael Granvik, Georgios Tsirvoulis et al. (+5 more)
The surfaces of airless bodies evolve through processes such as (micro)meteoroid impacts and thermal fatigue, which modify physical properties such as grain size, porosity, and mineral texture. These properties provide clues to surface
evolution and are necessary for interpreting telescopic observations. Near-Sun asteroids (NSAs), which reach heliocentric distances of $\lesssim$0.2 au, are notable targets, as their surfaces are likely modified by intense solar radiation. However, experimental studies of how radiative heating modifies the physical properties of carbonaceous asteroid surfaces remain scarce compared with studies of thermally induced compositional and spectral changes. We investigate these modifications experimentally. Near-Sun conditions at heliocentric distances $0.09<r<0.19$ au are simulated using the Space and High-Irradiance Near-Sun Simulator. CM-type carbonaceous chondrite simulants are irradiated under
vacuum. Brightness is monitored in situ with a
video camera during heating, and morphological changes are examined using a stage microscope and a scanning electron microscope (SEM). The irradiated samples show initial darkening followed by brightening, consolidation, and morphological modifications from sub-micrometer to millimeter scales. The observed brightness modifications are more consistent with changes in the absorption properties of the sample than with variations in surface roughness. SEM imaging of the heated samples shows structures similar to those formed by sintering, which are completely absent in unheated samples. These results suggest that sintering is a likely candidate for the mechanism responsible for the observed consolidation and morphological changes. This work provides experimental evidence to help constrain the surface
evolution of NSAs in general, and supports sintering as a possible mechanism proposed for (3200) Phaethon in particular.
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All authors Jooyeon Geem, Mikael Granvik, Georgios Tsirvoulis, Leonard Schirner, Marianna L. Kemell, Antti Penttila, Axel Hagermann, Athanasia Toliou