Composition Of Planets Research Articles

Random models for exploring planet compositions I: Uranus as an example

Modeling the interior of a planet is difficult because the small number of measured parameters is insufficient to constrain the many variables involved in describing the interior structure and composition. One solution is to invoke additional constraints based on arguments about how the planet formed. However, a planet’s actual structure and composition may hold clues to its formation which would be lost if this structure were not allowed by the initial assumptions. It is therefore interesting to explore the space of allowable compositions and structures in order to better understand which cosmogonic constraints are absolutely necessary. To this end, we describe a code for generating random, monotonic, density distributions, ρ(r), that fit a given mass, radius, and moment of inertia. Integrating the equation of hydrostatic equilibrium gives the pressure, P(r), at each point in the body. We then provide three algorithms for generating a monotonic temperature distribution, T(r), and an associated composition that is consistent with the ρ−P relation, and realistic equations of state. We apply this code to Uranus as a proof of concept, and show that the ratio of rock to water cannot be much larger than 2.

Tracing pebble drift and trapping using radial carbon depletion profiles in protoplanetary disks

Context. The composition of planets may be largely determined by the chemical processing and accretion of icy pebbles in protoplanetary disks. Recent observations of protoplanetary disks hint at wide-spread depletion of gaseous carbon. The missing volatile carbon is likely frozen in CO and/or CO2 ice on grains and locked into the disk through pebble trapping in pressure bumps or planetesimals. Aims. We aim to measure the total elemental C/H ratio in the outer region of seven disks, four of which have been previously shown to be depleted of carbon gas interior to 0.1 AU through near-infrared spectroscopy. Methods. We present the results of the first successful Atacama Compact Array (ACA) [C I] J = 1−0 mini-survey of seven protoplanetary disks. Using tailored azimuthally symmetric Dust And LInes thermo-chemical disk models, supported by the [C I] J = 1−0 and resolved CO isotopologue data, we determine the system-averaged elemental volatile carbon abundance in the outer disk of three sources. Results. Six out of the seven sources are detected in [C I] J = 1−0 with ACA, four of which show a distinct disk component. Based on the modeling we find severe cold gaseous carbon depletion by a factor of 157+17-15 in the outer disk of DL Tau and moderate depletion in the outer disks of DR Tau and DO Tau, by factors of 5+2-1 and 17+3-2, respectively. The carbon abundance is in general expected to be higher in the inner disk if carbon-rich ices drift on large grains toward the star. Combining the outer and inner disk carbon abundances, we demonstrate definitive evidence for radial drift in the disk of DL Tau, where the existence of multiple dust rings points to either short-lived or leaky dust traps. We find dust locking in the compact, smooth disks of DO Tau and DR Tau, which hints at unresolved dust substructure. Comparing our results with the inner and outer disk carbon depletion around stars of different ages and luminosities, we identify an observational evolutionary trend in gaseous carbon depletion that is consistent with dynamical models of CO depletion processes. Conclusions. The transport efficiency of solids in protoplanetary disks can significantly differ from what we expect based on the current resolved substructure in the continuum observations. This has important implications for our understanding of the impact of radial drift and pebble accretion on planetary compositions.

Forming Planets Around Stars With Non-Solar Elemental Composition

Context. Stars in the solar neighbourhood have refractory element ratios slightly different from that of the Sun. It is unclear how much the condensation of solids and thus the composition of planets forming around these stars is affected. Aims. We aim to understand the impact of changing the ratios of the refractory elements Mg, Si, and Fe within the range observed in solar-type stars within 150 pc of the Sun on the composition of planets forming around them. Methods. We use the GGchem code to simulate the condensation of solids in protoplanetary disks with a minimum mass solar nebula around main sequence G-type stars in the solar neighbourhood. We extract the stellar elemental composition from the Hypatia Database. Results. We find that a lower Mg/Si ratio shifts the condensation sequence from forsterite (Mg2SiO4) and SiO to enstatite (MgSiO3) and quartz (SiO2); a lower Fe/S ratio leads to the formation of FeS and FeS2 and few or no Fe-bearing silicates. Ratios of refractory elements translate directly from the gas phase to the condensed phase for T < 1000 K. However, ratios with respect to volatile elements (e.g. oxygen and sulphur) in the condensates – the building blocks of planets – differ from the original stellar composition. Conclusions. Our study shows that the composition of planets crucially depends on the abundances of the stellar system under investigation. Our results can have important implications for planet interiors, which depend strongly on the degree of oxidation and the sulphur abundance.

The origin of the high metallicity of close-in giant exoplanets

Context. The composition of gas giant planets reflects their formation and evolution history. Revealing the origin of the high heavy-element masses in giant exoplanets is an objective of planet formation theories. Planetesimal accretion during the phase of planetary migration could lead to the delivery of heavy elements into gas giant planets. In our previous paper, we used dynamical simulations and showed that planetesimal accretion during planetary migration occurs in a rather narrow region of the protoplanetary disk, which we refer to as the “sweet spot” for accretion. Aims. Our understanding of the sweet spot, however, is still limited. The location of the sweet spot within the disk and how it changes as the disk evolves were not investigated in detail. The goal of this paper is to reveal the nature of the sweet spot using analytical calculations and to investigate the role of the sweet spot in determining the composition of gas giant planets. Methods. We analytically derived the required conditions for the sweet spot. Then, using the numerical integration of the orbits of planetesimals around a migrating planet, we compared the derived equations with the numerical results. Results. We find that the conditions required for the sweet spot can be expressed by the ratio of the aerodynamic gas damping timescale of the planetesimal orbits to the planetary migration timescale. If the planetary migration timescale depends on the surface density of disk gas inversely, the location of the sweet spot does not change with the disk evolution. We expect that the planets observed inner to the sweet spot include a much greater amount of heavy elements than the planets outer to the sweet spot. The mass of planetesimals accreted by the protoplanet in the sweet spot depends on the amount of planetesimals that are shepherded by mean motion resonances. Our analysis suggests that tens Earth-masses of planetesimals can be shepherded into the sweet spot without planetesimal collisions. However, as more planetesimals are trapped into mean motion resonances, collisional cascade can lead to fragmentation and the production of smaller planetesimals. This could affect the location of the sweet spot and the population of small objects in planetary systems. Conclusions. We conclude that the composition of gas giant planets depends on whether the planets crossed the sweet spot during their formation. Constraining the metallicity of cold giant planets, which are expected to be beyond the sweet spot, with future observations would reveal key information for understanding the origin of heavy elements in giant planets.

A Model Earth-sized Planet in the Habitable Zone of α Centauri A/B

Abstract The bulk chemical composition and interior structure of rocky exoplanets are fundamentally important to understand their long-term evolution and potential habitability. Observations of the chemical compositions of solar system rocky bodies and of other planetary systems have increasingly shown a concordant picture that the chemical composition of rocky planets reflects that of their host stars for refractory elements, whereas this expression breaks down for volatiles. This behavior is explained by devolatilization during planetary formation and early evolution. Here we apply a devolatilization model calibrated with solar system bodies to the chemical composition of our nearest Sun-like stars—α Centauri A and B—to estimate the bulk composition of any habitable-zone rocky planet in this binary system (“α-Cen-Earth”). Through further modeling of likely planetary interiors and early atmospheres, we find that, compared to Earth, such a planet is expected to have (i) a reduced (primitive) mantle that is similarly dominated by silicates, albeit enriched in carbon-bearing species (graphite/diamond); (ii) a slightly larger iron core, with a core mass fraction of 38.4 − 5.1 + 4.7 wt% (see Earth’s 32.5 ± 0.3 wt%); (iii) an equivalent water-storage capacity; and (iv) a CO2–CH4–H2O-dominated early atmosphere that resembles that of Archean Earth. Further taking into account its ∼25% lower intrinsic radiogenic heating from long-lived radionuclides, an ancient α-Cen-Earth (∼1.5–2.5 Gyr older than Earth) is expected to have less efficient mantle convection and planetary resurfacing, with a potentially prolonged history of stagnant-lid regimes.

Making Sense of Chondrite Meteorites

I describe the simplification of multitudes of complex data on hundreds of chondrite meteorites to obtain a fundamental relationship that underlies processes during solar system formation. From the relationship derived, generally, it can be concluded that only three processes, operant during solar system formation, are responsible for the diversity of matter in the solar system, as well as for planetary compositions , internal-structures, dynamics and magnetics: (1) Condensation at very high-pressures; (2) Condensation at very low-pressures; and (3) Scouring of the inner solar system by the T-Tauri eruptions during thermonuclear ignition of the sun.

Ground truth constraints and remote sensing of lunar highland crust composition

AbstractWe review constraints on the magnitude and possible causes of discrepancies, or at least major disparities, among global and near‐global data sets for lunar highland surface composition. When compared with data from other sources, reported mafic mineral abundance results from the Kaguya Spectral Profiler (Kaguya SP) spectral reflectance method for four Apollo 16 soils appear systematically low by a factor of 0.6, or an even more extreme factor (~1/3) if viewed in relation to the soils’ nonglass or CIPW mineralogy. Also, whether evaluated on a global median basis or on the basis of site‐by‐site comparison (for Apollo 16, Luna 20, and Apollo 17), the compositions found by the Kaguya SP technique show discrepancy, or at least disparity, versus other mafic abundance observations by that same factor of ~1/3. Spectral reflectance does not supply a simple bulk analysis of the target soil. The reflectance mineralogical signal is preponderantly determined by the nonglass fraction, and especially the masswise subordinate 10–20 µm grain size fraction. Literature data show that in anorthositic lunar soil, chemical composition is fractionated, more extremely anorthositic, for the nonglass component compared to the glass component. Also, the grain size fraction (10–20 μm) that most closely matches bulk reflectance has a significantly higher abundance of impact/agglutinitic glass than does the coarser material that dominates the soil mass. The Kaguya SP mafic abundance calibration needs adjustment by a factor of nearly 3 if results are to be interpreted as indicative of the mineralogy of the underlying crust. A claimed detection of several hundred lunar 500 m scale purest anorthosite (PAN; ≥98 vol% plagioclase) locales among millions of spectral reflectance observations is dubious, in part because with large data sets, compositional extremes are inevitably exaggerated as a byproduct of analytical uncertainty. Preponderance of PAN composition is rare among terrestrial layered intrusive anorthosites and is neither required nor expected for the flotation crust of a global magma ocean. Buoyant flotation and compaction would not suffice to yield pure plagioclase unless adcumulus growth was negligible, and trace element contents of ferroan anorthosites show that their mafic silicate components are for the most part of adcumulus, not “trapped melt,” derivation. A PAN‐dominated crust would imply a curiously fractionated (low) thorium/aluminum ratio for the crust, an implausibly high mantle/crust Th concentration ratio, and an oddly low Th/Al for the bulk Moon. Remote sensing techniques for planetary regolith composition are not easy to calibrate, particularly near the extremes of composition‐space and sensitivity.

THE NECESSITY FOR THE IMPLEMENTATION OF ENVIRONMENTAL INSURANCE IN THE REPUBLIC OF UZBEKISTAN

Natural disasters and human actions have recently caused a variety of environmental changes around the world. Climate and weather patterns are shifting dramatically across the planet, water and soil composition are getting increasingly polluted, and plant and animal species are becoming extinct.

Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N, and TESS

ABSTRACT We present a precise characterization of the TOI-561 planetary system obtained by combining previously published data with TESS and CHEOPS photometry, and a new set of 62 HARPS-N radial velocities (RVs). Our joint analysis confirms the presence of four transiting planets, namely TOI-561 b (P = 0.45 d, R = 1.42 R⊕, M = 2.0 M⊕), c (P = 10.78 d, R = 2.91 R⊕, M = 5.4 M⊕), d (P = 25.7 d, R = 2.82 R⊕, M = 13.2 M⊕), and e (P = 77 d, R = 2.55 R⊕, M = 12.6 R⊕). Moreover, we identify an additional, long-period signal (>450 d) in the RVs, which could be due to either an external planetary companion or to stellar magnetic activity. The precise masses and radii obtained for the four planets allowed us to conduct interior structure and atmospheric escape modelling. TOI-561 b is confirmed to be the lowest density (ρb = 3.8 ± 0.5 g cm−3) ultra-short period (USP) planet known to date, and the low metallicity of the host star makes it consistent with the general bulk density-stellar metallicity trend. According to our interior structure modelling, planet b has basically no gas envelope, and it could host a certain amount of water. In contrast, TOI-561 c, d, and e likely retained an H/He envelope, in addition to a possibly large water layer. The inferred planetary compositions suggest different atmospheric evolutionary paths, with planets b and c having experienced significant gas loss, and planets d and e showing an atmospheric content consistent with the original one. The uniqueness of the USP planet, the presence of the long-period planet TOI-561 e, and the complex architecture make this system an appealing target for follow-up studies.

Porosity-filling Metamorphic Brines Explain Ceres’s Low Mantle Density

Abstract Recent work has sought to constrain the composition and makeup of the dwarf planet Ceres’s mantle, which has a relatively low density, between 2400 and 2800 kg m−3, as inferred by observations by the Dawn mission. Explanations for this low density have ranged from a high fraction of porosity-filled brines to a high fraction of organic matter. We present a series of numerical thermodynamic models that yield the mineralogy and fluid composition in the mantle as a function of Ceres’s thermal evolution. We find that the resulting phase assemblage could have changed drastically since the formation of Ceres, as volatile-bearing minerals such as serpentine and carbonates would partially destabilize and release their volatiles as temperatures in the mantle reach their maximum about 3 Gyr after Ceres’s formation. These volatiles consist mainly of aqueous fluids containing Na+ and HS− throughout the metamorphic evolution of Ceres and, in addition, high concentrations of CO2 at high temperatures relatively recently. The predicted present-day phase assemblage in the mantle, consisting of partially devolatilized minerals and 13–30 vol% fluid-filled porosity, is consistent with the mantle densities inferred from Dawn. The metamorphic fluids generated in Ceres’s mantle may have replenished an ocean at the base of the crust and may even be the source of the Na2CO3 and NaHCO3 mineral deposits observed at Ceres’s surface.

Geoneutrinos and geoscience: an intriguing joint-venture

The review is conceived to help the reader to interpret present geoneutrino results in the framework of Earth's energetics and composition. Starting from the comprehension of antineutrino production, propagation, and detection, the status of the geoneutrino field is presented through the description of the experimental and technological features of the Borexino and KamLAND ongoing experiments. The current understanding of the energetical, geophysical and geochemical traits of our planet is examined in a critical analysis of the currently available models. By combining theoretical models and experimental results, the mantle geoneutrino signal extracted from the results of the two experiments demonstrates the effectiveness in investigating deep earth radioactivity through geoneutrinos from different sites. The obtained results are discussed and framed in the puzzle of the diverse classes of formulated Bulk Silicate Earth models, analyzing their implications on planetary heat budget and composition. As a final remark, we present the engaging technological challenges and the future experiments envisaged for the next decade in the geoneutrino field.

Planetary Evaporation

Evaporation of magma oceans exposed to space may have played a role in the chemical and isotopic compositions of rocky planets in our Solar System (e.g., Earth, Moon, Mars) and their protoplanetary antecedents. Chemical depletion of moderately volatile elements and the enrichment of these elements’ heavier isotopes in the Moon and Vesta relative to chondrites are clear examples. Evaporation is also thought to be an important process in some exoplanetary systems. Identification of evaporation signatures among the rock-forming elements could elucidate important reactions between melts and vapors during planet formation in general, but the process is more complicated than is often assumed.

Nauyaca: a New Tool to Determine Planetary Masses and Orbital Elements through Transit Timing Analysis

Abstract The transit timing variations method is currently the most successful method to determine dynamical masses and orbital elements for Earth-sized transiting planets. Precise mass determination is fundamental to restrict planetary densities and thus infer planetary compositions. In this work, we present Nauyaca, a Python package dedicated to finding planetary masses and orbital elements through the fitting of observed midtransit times from an N-body approach. The fitting strategy consists of performing a sequence of minimization algorithms (optimizers) that are used to identify high probability regions in the parameter space. These results from optimizers are used for initialization of a Markov chain Monte Carlo method, using an adaptive Parallel-Tempering algorithm. A set of runs are performed in order to obtain posterior distributions of planetary masses and orbital elements. In order to test the tool, we created a mock catalog of synthetic planetary systems with different numbers of planets where all of them transit. We calculate their midtransit times to give them as an input to Nauyaca, testing statistically its efficiency in recovering the planetary parameters from the catalog. For the recovered planets, we find typical dispersions around the real values of ∼1–14 M ⊕ for masses, between 10–110 s for periods, and between ∼0.01–0.03 for eccentricities. We also investigate the effects of the signal-to-noise ratio and number of transits on the correct determination of the planetary parameters. Finally, we suggest choices of the parameters that govern the tool for the usage with real planets, according to the complexity of the problem and computational facilities.

Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program

Context. To understand the formation and composition of planetary systems, it is essential to have insights into the chemical composition of their host stars. In particular, C/O elemental ratios are useful for constraining the density and bulk composition of terrestrial planets. Aims. We study the carbon abundances with a twofold objective. On the one hand, we want to evaluate the behaviour of carbon in the context of Galactic chemical evolution. On the other hand, we focus on the possible dependence of carbon abundances on the presence of planets and on the impact of various factors (such as different oxygen lines) on the determination of C/O elemental ratios. Methods. We derived chemical abundances of carbon from two atomic lines for 757 FGK stars in the HARPS-GTO sample, observed with high-resolution (R ~ 115 000) and high-quality spectra. The abundances were derived using a standard Local Thermodynamic Equilibrium analysis with automatically measured Equivalent Widths injected into the code MOOG and a grid of Kurucz ATLAS9 atmospheres. Oxygen abundances, derived using different lines, were taken from previous papers in this series and updated with the new stellar parameters. Results. We find that thick- and thin-disk stars are chemically disjunct for [C/Fe] across the full metallicity range that they have in common. Moreover, the population of high-α metal-rich stars also presents higher and clearly separated [C/Fe] ratios than thin-disk stars up to [Fe/H] ~ 0.2 dex. The [C/O] ratios present a general flat trend as a function of [O/H] but becomes negative at [O/H] ≳ 0dex. This trend is more clear when considering stars of similar metallicity. We find tentative evidence that stars with low-mass planets at lower metallicities have higher [C/Fe] ratios than stars without planets at the same metallicity, in the same way as has previously been found for α elements. Finally, the elemental C/O ratios for the vast majority of our stars are below 0.8 when using the oxygen line at 6158 Å, however, the forbidden oxygen line at 6300 Å provides systematically higher C/O values (going above 1.2 in a few cases) which also show a dependence on Teff. Moreover, by using different atmosphere models the C/O ratios can have a non-negligible difference for cool stars. Therefore, C/O ratios should be scaled to a common solar reference in order to correctly evaluate its behaviour. We find no significant differences in the distribution of C/O ratios for the different populations of planet hosts, except when comparing the stars without detected planets with the stars hosting Jupiter-type planets. However, we note that this difference might be caused by the different metallicity distributions of both populations. Conclusions. The derivation of homogeneous abundances from high-resolution spectra in samples that are modest in size is of great utility in constraining models of Galactic chemical evolution. The combination of these high-quality data with the long-term study of planetary presence in our sample is crucial for achieving an accurate understanding of the impact of stellar chemical composition on planetary formation mechanisms.

Specific Heat Capacity Measurements of Selected Meteorites for Planetary Surface Temperature Modeling

AbstractSpecific heat capacity Cp(T) is an intrinsic regolith property controlling planetary surface temperatures along with the albedo, density, and thermal conductivity. Cp(T) depends on material composition and temperature. Generally, modelers assume a fixed specific heat capacity value, or a standard temperature dependence derived from lunar basalts, mainly because of limited composition‐specific data at low temperatures relevant to planetary surfaces. In addition, Cp(T) only appears to vary by a small factor across various materials, in contrast with the bulk regolith thermal conductivity, which ranges over ∼3–4 orders of magnitude as a function of the regolith physical state (grain size, cementation, sintering, etc.). For these reasons, the impact of the basaltic assumption on modeled surface temperature is often considered unimportant although this assumption is not particularly well constrained. In this paper, we present specific heat capacity measurements and parameterizations from ∼90 to ∼290 K of 28 meteorites including those possibly originating from Mars and Vesta, and covering a wide range of planetary surface compositions. Planetary surface temperatures calculated using composition‐specific Cp(T) are within 2 K of model runs assuming a basaltic composition. This 2 K range approaches or exceeds typical instrumental noise or other sources of modeling uncertainties. These results suggest that a basaltic assumption for Cp(T) is generally adequate for the thermal characterization of a wide range of planetary surfaces, but possibly inadequate when looking at leveraging subtle trends to constrain subsurface layering, roughness, or seasonal/diurnal volatile transfer.

Molecules with ALMA at Planet-forming Scales (MAPS). I. Program Overview and Highlights

Abstract Planets form and obtain their compositions in dust- and gas-rich disks around young stars, and the outcome of this process is intimately linked to the disk chemical properties. The distributions of molecules across disks regulate the elemental compositions of planets, including C/N/O/S ratios and metallicity (O/H and C/H), as well as access to water and prebiotically relevant organics. Emission from molecules also encodes information on disk ionization levels, temperature structures, kinematics, and gas surface densities, which are all key ingredients of disk evolution and planet formation models. The Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program was designed to expand our understanding of the chemistry of planet formation by exploring disk chemical structures down to 10 au scales. The MAPS program focuses on five disks—around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480—in which dust substructures are detected and planet formation appears to be ongoing. We observed these disks in four spectral setups, which together cover ∼50 lines from over 20 different species. This paper introduces the Astrophysical Journal Supplement’s MAPS Special Issue by presenting an overview of the program motivation, disk sample, observational details, and calibration strategy. We also highlight key results, including discoveries of links between dust, gas, and chemical substructures, large reservoirs of nitriles and other organics in the inner disk regions, and elevated C/O ratios across most disks. We discuss how this collection of results is reshaping our view of the chemistry of planet formation.

Raman spectra of hydrocarbons under extreme conditions of pressure and temperature: a first-principles study

Hydrocarbons are of great importance in carbon-bearing fluids in deep Earth and in ice giant planets at extreme pressure (P)–temperature (T) conditions. Raman spectroscopy is a powerful tool to study the chemical speciation of hydrocarbons. However, it is challenging interpreting Raman data at extreme conditions. Here, we performed ab initio molecular dynamics simulations coupled with the modern theory of polarization to calculate Raman spectra of methane, ethane and propane up to 48 GPa and 2000 K. Our method includes anharmonic temperature effects. We studied the pressure and temperature effects on the Raman bands and identified the characteristic Raman modes for the C–C and C–C–C bonds. To the best of our knowledge, this is the first time that the Raman spectra of hydrocarbons have been calculated at extreme P–T conditions. Our results may help with the interpretation of in situ Raman data of hydrocarbons at extreme P–T conditions, with important implications for studying hydrocarbon reactions in the deep carbon cycle inside Earth and the composition of ice giant planets.

Carbon monoxide gas produced by a giant impact in the inner region of a young system.

Models of terrestrial planet formation predict that the final stages of planetary assembly-lasting tens of millions of years beyond the dispersal of young protoplanetary disks-are dominated by planetary collisions. It is through these giant impacts that planets like the young Earth grow to their final mass and achieve long-term stable orbital configurations1. A key prediction is that these impacts produce debris. So far, the most compelling observational evidence for post-impact debris comes from the planetary system around the nearby 23-million-year-old A-type star HD 172555. This system shows large amounts of fine dust with an unusually steep size distribution and atypical dust composition, previously attributed to either a hypervelocity impact2,3 or a massive asteroid belt4. Here we report the spectrally resolved detection of a carbon monoxide gas ring co-orbiting with dusty debris around HD 172555 between about six and nine astronomical units-a region analogous to the outer terrestrial planet region of our Solar System. Taken together, the dust and carbon monoxide detections favour a giant impact between large, volatile-rich bodies. This suggests that planetary-scale collisions, analogous to the Moon-forming impact, can release large amounts of gas as well as debris, and that this gas is observable, providing a window into the composition of young planets.

A compositional link between rocky exoplanets and their host stars.

Stars and planets both form by accreting material from a surrounding disk. Because they grow from the same material, theory predicts that there should be a relationship between their compositions. In this study, we search for a compositional link between rocky exoplanets and their host stars. We estimate the iron-mass fraction of rocky exoplanets from their masses and radii and compare it with the compositions of their host stars, which we assume reflect the compositions of the protoplanetary disks. We find a correlation (but not a 1:1 relationship) between these two quantities, with a slope of >4, which we interpret as being attributable to planet formation processes. Super-Earths and super-Mercuries appear to be distinct populations with differing compositions, implying differences in their formation processes.

Exploring the link between star and planet formation with Ariel

The goal of the Ariel space mission is to observe a large and diversified population of transiting planets around a range of host star types to collect information on their atmospheric composition. The planetary bulk and atmospheric compositions bear the marks of the way the planets formed: Ariel’s observations will therefore provide an unprecedented wealth of data to advance our understanding of planet formation in our Galaxy. A number of environmental and evolutionary factors, however, can affect the final atmospheric composition. Here we provide a concise overview of which factors and effects of the star and planet formation processes can shape the atmospheric compositions that will be observed by Ariel, and highlight how Ariel’s characteristics make this mission optimally suited to address this very complex problem.