Physical Sciences and Mathematics Commons^™

Patchy Forsterite Clouds In The Atmospheres Of Two Highly Variable Exoplanet Analogs, Johanna M. Vos, Ben Burningham, Jacqueline K. Faherty, Sherelyn Alejandro, Eileen Gonzales, Emily Calamari, Daniella Bardalez Gagliuffi, Channon Visscher, Xianyu Tan, Caroline V. Morley, Mark Marley, Marina E. Gemma, Niall Whiteford, Josefine Gaarn, Grace Park

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We present an atmospheric retrieval analysis of a pair of highly variable, ∼200 Myr old, early T type planetary-mass exoplanet analogs SIMP J01365662+0933473 and 2MASS J21392676+0220226 using the Brewster retrieval framework. Our analysis, which makes use of archival 1–15 μm spectra, finds almost identical atmospheres for both objects. For both targets, we find that the data is best described by a patchy, high-altitude forsterite (Mg2SiO4) cloud above a deeper, optically thick iron (Fe) cloud. Our model constrains the cloud properties well, including the cloud locations and cloud particle sizes. We find that the patchy forsterite slab cloud inferred from our …

Probing The Extent Of Vertical Mixing In Brown Dwarf Atmospheres With Disequilibrium Chemistry, Sagnick Mukherjee, Jonathan J. Fortney, Natasha E. Batalha, Theodora Karalidi, Mark S. Marley, Channon Visscher, Brittany E. Miles, Andrew J. I. Skemer

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Evidence of disequilibrium chemistry due to vertical mixing in the atmospheres of many T- and Y-dwarfs has been inferred due to enhanced mixing ratios of CO and reduced NH3. Atmospheric models of planets and brown dwarfs typically parameterize this vertical mixing phenomenon with the vertical eddy diffusion coefficient, Kzz. While Kzz can perhaps be approximated in the convective regions in the atmosphere with mixing length theory, in radiative regions, the strength of vertical mixing is uncertain by many orders of magnitude. With a new grid of selfconsistent 1D model atmospheres from Teff of 400–1000 K, computed with a new radiative-convective …

A Comparative L-Dwarf Sample Exploring The Interplay Between Atmospheric Assumptions And Data Properties, Eileen C. Gonzales, Ben Burningham, Jacqueline K. Faherty, Nikole K. Lewis, Channon Visscher, Mark Marley

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Comparisons of atmospheric retrievals can reveal powerful insights on the strengths and limitations of our data and modeling tools. In this paper, we examine a sample of five L dwarfs of similar effective temperature (Teff) or spectral type to compare their pressure–temperature (P-T) profiles. Additionally, we explore the impact of an object's metallicity and the signal-to-noise ratio (S/N) of the observations on the parameters we can retrieve. We present the first atmospheric retrievals: 2MASS J15261405+2043414, 2MASS J05395200−0059019, 2MASS J15394189−0520428, and GD 165B increasing the small but growing number of L dwarfs retrieved. When compared to the atmospheric retrievals …

The Extent, Nature, And Origin Of K And Rb Depletions And Isotopic Fractionations In Earth, The Moon, And Other Planetary Bodies, Nicolas Dauphas, Nicole X. Nie, Marc Blanchard, Zhe J. Zhang, Hao Zeng, Justin Y. Hu, Merlin Meheut, Channon Visscher, Robin Canup, Timo Hopp

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Moderately volatile elements (MVEs) are depleted and isotopically fractionated in the Moon relative to Earth. To understand how the composition of the Moon was established, we calculate the equilibrium and kinetic isotopic fractionation factors associated with evaporation and condensation processes. We also reassess the levels of depletions of K and Rb in planetary bodies. Highly incompatible element ratios are often assumed to be minimally affected by magmatic processes, but we show that this view is not fully warranted, and we develop approaches to mitigate this issue. The K/U weight ratios of Earth and the Moon are estimated to be 9704 …

The Sonora Substellar Atmosphere Models. Ii. Cholla: A Grid Of Cloud-Free, Solar Metallicity Models In Chemical Disequilibrium For The Jwst Era, Theodora Karalidi, Mark Marley, Jonathan J. Fortney, Caroline Morley, Didier Saumon, Roxana Lupu, Channon Visscher, Richard Freedman

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Exoplanet and brown dwarf atmospheres commonly show signs of disequilibrium chemistry. In the James Webb Space Telescope (JWST) era, high-resolution spectra of directly imaged exoplanets will allow the characterization of their atmospheres in more detail, and allow systematic tests for the presence of chemical species that deviate from thermochemical equilibrium in these atmospheres. Constraining the presence of disequilibrium chemistry in these atmospheres as a function of parameters such as their effective temperature and surface gravity will allow us to place better constraints on the physics governing these atmospheres. This paper is part of a series of works presenting the Sonora …

All I Want For Christmas..., Channon Visscher

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"JWST [the James Webb Space Telescope] will let us see clearer and further into the ancient and beautiful story of creation."

Posting about new developments in spacecraft from In All Things - an online journal for critical reflection on faith, culture, art, and every ordinary-yet-graced square inch of God’s creation.

https://inallthings.org/all-i-want-for-christmas/

Following The Lithium: Tracing Li-Bearing Molecules Across Age, Mass, And Gravity In Brown Dwarfs, Ehsan Gharib-Nezhad, Mark S. Marley, Natasha E. Batalha, Channon Visscher, Richard S. Freedman, Roxana E. Lupu

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Lithium is an important element for the understanding of ultracool dwarfs because it is lost to fusion at masses above ∼68 MJ. Hence, the presence of atomic Li has served as an indicator of the nearby H-burning boundary at about 75 MJ between brown dwarfs and very low mass stars. Historically, the “lithium test,” a search for the presence of the Li line at 670.8 nm, has been a marker if an object has a substellar mass. While the Li test could, in principle, be used to distinguish masses of later-type L–T dwarfs, Li is predominantly no longer found as …

Cloud Busting: Enstatite And Quartz Clouds In The Atmosphere Of 2m2224-0158, Ben Burningham, Jacqueline K. Faherty, Eileen C. Gonzales, Mark S. Marley, Channon Visscher, Roxana Lupu, Josefine Gaarn, Michelle Fabienne Bieger, Richard Freedman, Didier Saumon

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We present the most detailed data-driven exploration of cloud opacity in a substellar object to-date. We have tested over 60 combinations of cloud composition and structure, particle-size distribution, scattering model, and gas phase composition assumptions against archival 1–15μm spectroscopy for the unusually red L4.5 dwarf 2MASSW J2224438-015852 using the Brewster retrieval framework. We find that, within our framework, a model that includes enstatite and quartz cloud layers at shallow pressures, combined with a deep iron cloud deck fits the data best. This model assumes a Hansen distribution for particle sizes for each cloud, and Mie scattering. We retrieved particle effective …

Kinds Of Science And Exploring The Past, Channon Visscher

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"Working alongside experimental and observational work, historical science helps us continue to learn the unfolding story of how a beautiful universe, created by a loving God, came to be as we see it today."

Posting about scientific methods from In All Things - an online journal for critical reflection on faith, culture, art, and every ordinary-yet-graced square inch of God’s creation.

https://inallthings.org/kinds-of-science-and-exploring-the-past/

Mapping Jupiter's Mischief, Channon Visscher

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New results (Grassi et al., 2020, https://doi.org/10.1029/2019JE006206) from analysis of Juno Jovian Infrared Auroral Mapper (JIRAM) 4‐ to 5‐μm observations provide updated latitudinal abundance profiles and measurements of the spatial distribution of H2O, NH3, PH3, GeH4, and AsH3 in Jupiter's troposphere near the 3‐ to 5‐bar level. The observed compositional variations provide new constraints on processes shaping chemical abundances in the cloud‐forming region of the troposphere, including vertical and horizontal atmospheric mixing, meteorology and cloud formation, transport‐induced quenching, and photochemistry. Along with recent results from the Juno Microwave Radiometer (MWR) for NH3 and H2O abundances far below the clouds, the …

Retrieval Of The D/Sdl7+T7.5p Binary Sdss J1416+1348ab, Eileen C. Gonzales, Ben Burningham, Jacqueline K. Faherty, Colleen Cleary, Channon Visscher, Mark S. Marley, Roxana Lupu, Richard Freedman

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We present the distance-calibrated spectral energy distribution (SED) of the d/sdL7 SDSS J14162408+1348263A (J1416A) and an updated SED for SDSS J14162408+1348263B (J1416B). We also present the first retrieval analysis of J1416A using the Brewster retrieval code base and the second retrieval of J1416B. We find that the primary is best fit by a nongray cloud opacity with a power-law wavelength dependence but is indistinguishable between the type of cloud parameterization. J1416B is best fit by a cloud-free model, consistent with the results from Line et al. Most fundamental parameters derived via SEDs and retrievals are consistent within 1σ for both …

Beyond Equilibrium Temperature: How The Atmosphere/Interior Connection Affects The Onset Of Methane, Ammonia, And Clouds In Warm Transiting Giant Planets, Jonathan J. Fortney, Channon Visscher, Mark S. Marley, Callie E. Hood, Michael R. Line, Daniel P. Thorngren, Richard S. Freedman, Roxana Lupu

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The atmospheric pressure–temperature profiles for transiting giant planets cross a range of chemical transitions. Here we show that the particular shapes of these irradiated profiles for warm giant planets below ∼1300 K lead to striking differences in the behavior of nonequilibrium chemistry compared to brown dwarfs of similar temperatures. Our particular focus is H2O, CO, CH4, CO2, and NH3 in Jupiter- and Neptune-class planets. We show that the cooling history of a planet, which depends most significantly on planetary mass and age, can have a dominant effect on abundances in the visible atmosphere, often swamping trends one might expect based …

From Thermal Dissociation To Condensation In The Atmospheres Of Ultra Hot Jupiters: Wasp-121b In Context, Vivien Parmentier, Mike R. Line, Jacob L. Bean, Megan Mansfield, Laura Kreidberg, Roxana Lupu, Channon Visscher, Jean-Michel Desert, Jonathan J. Fortney, Magalie Deleuil, Jacob Arcangeli, Adam P. Showman, Mark S. Marley

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Context. A new class of exoplanets has emerged: the ultra hot Jupiters, the hottest close-in gas giants. The majority of them have weaker-than-expected spectral features in the 1.1−1.7 μm bandpass probed by HST/WFC3 but stronger spectral features at longer wavelengths probed by Spitzer. This led previous authors to puzzling conclusions about the thermal structures and chemical abundances of these planets.

Aims. We investigate how thermal dissociation, ionization, H− opacity, and clouds shape the thermal structures and spectral properties of ultra hot Jupiters.

Methods. We use the SPARC/MITgcm to model the atmospheres of four ultra hot Jupiters and discuss …

Mapping The Neutrino Floor For Direct Detection Experiments Based On Dark Matter-Electron Scattering, Jason Wyenberg, Ian M. Shoemaker

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We study the discovery reach of future Dark Matter (DM) Direct Detection experiments using DM-electron scattering in the presence of the solar neutrino background. At these low energies traditional methods for nuclear and electronic recoil discrimination fail, implying that the neutrino- nucleusscattering background can be sizable. We calculate discovery limits based on ionization values of signal and background, and quantify the dependence on the ionization model. Moreover, we explore how the dependence of the DM cross section discovery limits varies with exposure, electronic/nuclear recoil discrimination, DM form factors, and DM astrophysical uncertainties.

Against Common Sense, Channon Visscher

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"Scientific inquiry... allows for the exploration of phenomena that would otherwise remain beyond human intuition."

Posting about ­­­­­­­­beauty and truth in creation from In All Things - an online journal for critical reflection on faith, culture, art, and every ordinary-yet-graced square inch of God’s creation.

https://inallthings.org/against-common-sense/

An L Band Spectrum Of The Coldest Brown Dwarf, Caroline V. Morley, Andrew J. Skemer, Katelyn N. Allers, Mark S. Marley, Jacqueline K. Faherty, Channon Visscher, Samuel A. Beiler, Brittany E. Miles, Roxana Lupu, Richard S. Freedman, Jonathan J. Fortney, Thomas R. Geballe, Gordon L. Bjoraker

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The coldest brown dwarf, WISE 0855, is the closest known planetary-mass, free-floating object and has a temperature nearly as cold as the solar system gas giants. Like Jupiter, it is predicted to have an atmosphere rich in methane, water, and ammonia, with clouds of volatile ices. WISE 0855 is faint at near-infrared wavelengths and emits almost all its energy in the mid-infrared. Skemer et al. (2016) presented a spectrum of WISE 0855 from 4.5–5.1 µm (M band), revealing water vapor features. Here, we present a spectrum of WISE 0855 in L band, from 3.4–4.14 µm. We present a set of …

Retrieval Of Atmospheric Properties Of Cloudy L Dwarfs, Ben Burningham, M. S. Marley, M. R. Line, R. Lupu, Channon Visscher, C. V. Morley, D. Saumon, R. Freedman

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We present the first results from applying the spectral inversion technique in the cloudy L dwarf regime. Our new framework provides a flexible approach to modelling cloud opacity which can be built incrementally as the data require and improves upon previous retrieval experiments in the brown dwarf regime by allowing for scattering in two-stream radiative transfer. Our first application of the tool to two mid-L dwarfs is able to reproduce their near-infrared spectra far more closely than grid models. Our retrieved thermal, chemical and cloud profiles allow us to estimate Teff=1796−25+23" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; …

High Temperature Condensate Clouds In Super-Hot Jupiter Atmospheres, H. R. Wakeford, Channon Visscher, Nikole K. Lewis, Avi M. Mandell

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Deciphering the role of clouds is central to our understanding of exoplanet atmo- spheres, as they have a direct impact on the temperature and pressure structure, and observational properties of the planet. Super-hot Jupiters occupy a temperature regime similar to low mass M-dwarfs, where minimal cloud condensation is expected. However, observations of exoplanets such as WASP-12b (Teq∼2500 K) result in a transmission spectrum indicative of a cloudy atmosphere. We re-examine the temperature and pressure space occupied by these super-hot Jupiter atmospheres, to explore the role of the initial Al- and Ti-bearing condensates as the main source of cloud material. Due …

On The Composition Of Young, Directly Imaged Giant Planets, Julianne I. Moses, Mark S. Marley, K. Zahnle, M. R. Line, Jonathan J. Fortney, T. S. Barman, Channon Visscher, Nikole K. Lewis, M. J. Wolff

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The past decade has seen significant progress on the direct detection and characterization of young, self-luminous giant planets at wide orbital separations from their host stars. Some of these planets show evidence for disequilibrium processes like transport-induced quenching in their atmospheres; photochemistry may also be important, despite the large orbital distances. These disequilibrium chemical processes can alter the expected composition, spectral behavior, thermal structure, and cooling history of the planets, and can potentially confuse determinations of bulk elemental ratios, which provide important insights into planet-formation mechanisms. Using a thermo/photochemical kinetics and transport model, we investigate the extent to which disequilibrium …

Lunar Stories: The Violence Of Creation, Channon Visscher

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"Tales of the moon’s creation abound in myth, legend, history and science. Given its conspicuous brightness and nearness, we should not be surprised that the moon has captured the imagination since the dawn of human consciousness."

Posting about how the moon was made ­­­­­­­­from In All Things - an online hub committed to the claim that the life, death, and resurrection of Jesus Christ has implications for the entire world.

http://inallthings.org/lunar-stories-the-violence-of-creation/

Hunt For Planet Nine: Atmosphere, Spectra, Evolution, And Detectability, Jonathan J. Fortney, Mark S. Marley, Gregory Laughlin, Nadine Nettelmann, Caroline V. Morley, Roxana E. Lupu, Channon Visscher, Pavle Jeremic, Wade G. Khadder, Mason Hargrave

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We investigate the physical characteristics of the solar system's proposed Planet Nine using modeling tools with a heritage of studying Uranus and Neptune. For a range of plausible masses and interior structures, we find upper limits on the intrinsic , from ~35 to 50 K for masses of 5–20 M _⊕, and we also explore lower values. Possible planetary radii could readily span from 2.7 to 6 R _⊕, depending on the mass fraction of any H/He envelope. Given its cold atmospheric temperatures, the planet encounters significant methane condensation, which dramatically alters the atmosphere away from simple Neptune-like …

Atmospheric Circulation Of A Nine-Hot-Jupiter Sample: Probing Circulation And Chemistry Over A Wide Phase Space, Tiffany Kataria, David K. Sing, Nikole K. Lewis, Channon Visscher, Adam P. Showman, Jonathan J. Fortney, Mark S. Marley

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We present results from an atmospheric circulation study of nine hot Jupiters that comprise a large transmission spectral survey using the Hubble and Spitzer Space Telescopes. These observations ex-hibit a range of spectral behavior over optical and infrared wavelengths which suggest diverse cloud and haze properties in their atmospheres. By utilizing the specific system parameters for each planet, we naturally probe a wide phase space in planet radius, gravity, orbital period, and equilibrium tem-perature. First, we show that our model “grid” recovers trends shown in traditional parametric studies of hot Jupiters, particularly equatorial superrotation and increased day-night temperature contrast with …

Leech Exoplanet Imaging Survey: Characterization Of The Coldest Directly Imaged Exoplanet, Gj 504 B, And Evidence For Super-Stellar Metallicity, Andrew J. Skemer, Caroline V. Morley, Neil T. Zimmerman, Michael F. Skrutskie, Jarron Leisenring, Esther Buenzli, Mickael Bonnefoy, Vanessa Bailey, Philip Hinz, Denis Defrere, Simone Esposito, Daniel Apai, Beth Biller, Wolfgang Brandner, Laird Close, Justin R. Crepp, Robert J. De Rosa, Silvano Desidera, Josh Eisner, Jonathan Fortney, Richard Freedman, Thomas Henning, Karl-Heinz Hofmann, Taisiya Kopytova, Roxana Lupu, Anne-Lise Maire, Jared R. Males, Mark Marley, Katie Morzinski, Apurva Oza, Jenny Patience, Abhijith Rajan, George Rieke, Dieter Schertl, Joshua Schlieder, Jordan Stone, Kate Su, Amali Vaz, Channon Visscher, Kimberly Ward-Duong, Gerd Weigelt, Charles E. Woodward

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As gas giant planets and brown dwarfs radiate away the residual heat from their formation, they cool through a spectral type transition from L to T, which encompasses the dissipation of cloud opacity and the appearance of strong methane absorption. While there are hundreds of known T-type brown dwarfs, the first generation of directly-imaged exoplanets were all L-type. Recently, Kuzuhara et al. (2013) announced the discovery of GJ 504 b, the first T dwarf exoplanet. GJ 504 b provides a unique opportunity to study the atmosphere of a new type of exoplanet with a ∼500 K temperature that bridges the …

Chemistry Of The Protolunar Disk And Volatile Depletion Of The Moon, Channon Visscher, Robin M. Canup, Julien Salmon, Bruce Fegley Jr.

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In the giant impact theory for lunar origin, the Moon forms from a circumterrestrial disk of silicate debris produced by the collision of a planetary-sized impactor with the early Earth. Recent accretion models suggest that the final 10-60% of the lunar mass may be provided by the accretion of melt material spreading outward from the inner (Roche-interior) disk over the first ~102 years following the giant impact. The chemical and thermal evolution of the inner disk material is thus expected to strongly influence the bulk chemical composition of the Moon.

In a previous study we explored the chemistry of the …

Protolunar Disk Evolution And The Depletion Of Volatile Elements In The Moon, Robin M. Canup, Channon Visscher, Julien Salmon, Bruce Fegley Jr.

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We explore how the evolution of the protolunar disk could lead to a depletion in K, Na, and Zn in the Moon relative to Earth even in the absence of escape.

Identification Of Magnetite In Lunar Regolith Breccia 60016: Evidence For Oxidized Conditions At The Lunar Surface, Katherine H. Joy, Channon Visscher, Michael E. Zolensky, Takashi Mikouchi, Kenji Hagiya, Kazumasa Ohsumi, David A. Kring

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Lunar regolith breccias are temporal archives of magmatic and impact bombardment processes on the Moon. Apollo 16 sample 60016 is an ‘ancient’ feldspathic regolith breccia that was converted from a soil to a rock at ~3.8 Ga. The breccia contains a small (70 × 50 μm) rock fragment composed dominantly of an Fe-oxide phase with disseminated domains of troilite. Fragments of plagioclase (An95-97), pyroxene (En74-75, Fs21-22,Wo3-4) and olivine (Fo66-67) are distributed in and adjacent to the Fe-oxide. The silicate minerals have lunar compositions that are similar to anorthosites. Mineral chemistry, synchrotron X-ray Absorption Near Edge Spectroscopy (XANES) and X-ray Diffraction …

Compositional Diversity In The Atmospheres Of Hot Neptunes, With Application To Gj 436b, J. I. Moses, M. R. Line, Channon Visscher, M. R. Richardson, N. Nettleman, J. J. Fortney, T. S. Barman, K. B. Stevenson, N. Madhusudhan

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Neptune-sized extrasolar planets that orbit relatively close to their host stars—often called "hot Neptunes"—are common within the known population of exoplanets and planetary candidates. Similar to our own Uranus and Neptune, inefficient accretion of nebular gas is expected produce hot Neptunes whose masses are dominated by elements heavier than hydrogen and helium. At high atmospheric metallicities of 10-10,000 times solar, hot Neptunes will exhibit an interesting continuum of atmospheric compositions, ranging from more Neptune-like, H₂-dominated atmospheres to more Venus-like, CO₂-dominated atmospheres. We explore the predicted equilibrium and disequilibrium chemistry of generic hot Neptunes and find that …

Chemistry Of Impact-Generated Silicate Melt-Vapor Debris Disks, Channon Visscher, Bruce Fegley Jr.

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In the giant impact theory for lunar origin, the Moon forms from material ejected by the impact into an Earth-orbiting disk. Here we report the initial results from a silicate melt-vapor equilibrium chemistry model for such impact-generated planetary debris disks. In order to simulate the chemical behavior of a two-phase (melt+vapor) disk, we calculate the temperature-dependent pressure and chemical composition of vapor in equilibrium with molten silicate from 2000 to 4000 K. We consider the elements O, Na, K, Fe, Si, Mg, Ca, Al, Ti, and Zn for a range of bulk silicate compositions (Earth, Moon, Mars, eucrite parent body, …