A Catalog of Spectra, Albedos, and Colors of Solar System Bodies for Exoplanet Comparison

Madden, Jack; Kaltenegger, Lisa

doi:10.1089/ast.2017.1763

Cited by 33 publications

(17 citation statements)

References 43 publications

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“…Table 2 lists the albedos of several Solar System bodies. The rocky bodies in the Solar System generally have low albedos (Madden & Kaltenegger 2018). E-type asteroids 2 are an interesting exception to the general trend of dark solar system rocks, with albedos > 0.3.…”

Section: Which Surface Compositions Are Expected Tomentioning

confidence: 99%

Identifying Atmospheres on Rocky Exoplanets through Inferred High Albedo

Mansfield

Kite

et al. 2019

ApJ

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The upcoming launch of the James Webb Space Telescope (JWST ) means that we will soon have the capability to characterize the atmospheres of rocky exoplanets. However, it is still unknown whether such planets orbiting close to M dwarf stars can retain their atmospheres, or whether high-energy irradiation from the star will strip the gaseous envelopes from these objects. We present a new method to detect an atmosphere on a synchronously rotating rocky exoplanet around a K/M dwarf, by using thermal emission during secondary eclipse to infer a high dayside albedo that could only be explained by bright clouds. Based on calculations for plausible surface conditions, we conclude that a high albedo could be unambiguously interpreted as a signal of an atmosphere for planets with substellar temperatures of T sub = 410-1250 K. This range corresponds to equilibrium temperatures of T eq = 300-880 K. We compare the inferred albedos of eight possible planet surface compositions to cloud albedo calculations. We determine that a layer of clouds with optical depths greater than τ = 0.5 -7, would have high enough albedos to be distinguishable from a bare rock surface. This method of detecting an atmosphere on a rocky planet is complementary to existing methods for detecting atmospheres, because it provides a way to detect atmospheres with pressures below 1 bar (e.g. Mars), which are too tenuous to transport significant heat but thick enough to host high-albedo clouds.

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Section: Which Surface Compositions Are Expected Tomentioning

confidence: 99%

Identifying Atmospheres on Rocky Exoplanets through Inferred High Albedo

Mansfield

Kite

et al. 2019

ApJ

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“…If time-resolved observations are available, broadband photometric and polarimetric phase curves may be sensitive to the presence of liquid water oceans and land (Cowan & Strait 2013;Fujii et al 2017;Trees & Stam 2019). Other efforts have been proposed using high-resolution spectra and phase curves to probe atmospheric composition (Wolf et al 2019;Chen et al 2019), colors to identify qualitative planet type (Madden & Kaltenegger 2018), and albedo measurements to probe the existence of atmospheres (Mansfield et al 2019;Koll & Cronin 2019). However, all of these analyses either used 1D models that cannot capture the spatial heterogeneity of realistic climates, or relied on a relatively small number of model climates, making it difficult to quantify their robustness to model parameterizations and assumptions.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Challenges to Remote Sensing of Exo-Earths

Paradise,

Menou,

Lee

et al. 2021

Preprint

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Inferring the climate and surface conditions of terrestrial exoplanets in the habitable zone is a major goal for the field of exoplanet science. This pursuit will require both statistical analyses of the population of habitable planets as well as in-depth analyses of the climates of individual planets. Given the close relationship between habitability and surface liquid water, it is important to ask whether the fraction of a planet's surface where water can be a liquid, 𝜒 hab , can be inferred from observations. We have produced a diverse bank of 1,874 3D climate models and computed the full-phase reflectance and emission spectrum for each model to investigate whether surface climate inference is feasible with high-quality direct imaging or secondary eclipse spectroscopy. These models represent the outcome of approximately 200,000 total simulated years of climate and over 50,000 CPU-hours, and the roughly-100 GB model bank and its associated spectra are being made publicly-available for community use. We find that there are correlations between spectra and 𝜒 hab that will permit statistical approaches. However, spectral degeneracies in the climate observables produced by our model bank indicate that inference of individual climates is likely to be model-dependent, and inference will likely be impossible without exhaustive explorations of the climate parameter space. The diversity of potential climates on habitable planets therefore poses fundamental challenges to remote sensing efforts targeting exo-Earths.

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“…Our chosen value of 0.1 for the surface albedo is based on solar system findings that rocky bodies without an extended atmosphere and icy surface are dark. For instance, the Bond albedos of Mercury, the Moon and Ceres are all within 0−0.2 (Lundock et al 2009;Madden & Kaltenegger 2018). Also, potential surface materials for exoplanets are thought to possess low albedos (Hu et al 2012;Mansfield et al submitted).…”

Section: Comments On the Modeling Set-upmentioning

confidence: 99%

Analyzing Atmospheric Temperature Profiles and Spectra of M Dwarf Rocky Planets

Malik

Kempton

Koll

et al. 2019

ApJ

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The highly anticipated launch of the James Webb Space Telescope (JWST ) will open up the possibility of comprehensively measuring the thermal emission spectra of rocky exoplanets orbiting M dwarfs to detect and characterize their atmospheres. In preparation for this opportunity, we present model atmospheres for three terrestrial M-dwarf planets particularly amenable to secondary eclipse spectroscopy -TRAPPIST-1b, GJ 1132b, and LHS 3844b. Using three limiting cases of candidate atmospheric compositions (pure H 2 O, pure CO 2 and solar abundances) we calculate temperaturepressure profiles and emission and reflection spectra in radiative-convective equilibrium, including the effects of a solid surface at the base of the atmosphere. Our results differ appreciably from simpler parameterized models of super-Earth atmospheres in terms of the overall temperatures and the temperature gradient, which has important observational consequences. We find that the atmospheric radiative transfer is significantly influenced by the cool M-star irradiation; H 2 O and CO 2 absorption bands in the near-infrared are strong enough to absorb a sizeable fraction of the incoming stellar light at low pressures, which leads to temperature inversions in the upper atmosphere. The non-gray band structure of gaseous opacities in the infrared is hereby an important factor. Opacity windows are muted at higher atmospheric temperatures, so we expect temperature inversions to be common only for sufficiently cool planets. We also find that pure CO 2 atmospheres exhibit lower overall temperatures and stronger reflection spectra compared to models of the other two compositions. We estimate that for GJ 1132b and LHS 3844b we should be able to distinguish between different atmospheric compositions with JWST. The emission lines from the predicted temperature inversions are currently hard to measure, but high resolution spectroscopy with future Extremely Large Telescopes may be able to detect them.

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A Catalog of Spectra, Albedos, and Colors of Solar System Bodies for Exoplanet Comparison

Cited by 33 publications

References 43 publications

Identifying Atmospheres on Rocky Exoplanets through Inferred High Albedo

Identifying Atmospheres on Rocky Exoplanets through Inferred High Albedo

Fundamental Challenges to Remote Sensing of Exo-Earths

Analyzing Atmospheric Temperature Profiles and Spectra of M Dwarf Rocky Planets

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