Mapping Earth Analogs From Photometric Variability: Spin-Orbit Tomography for Planets in Inclined Orbits

Fujii, Yuka; Kawahara, Hajime

doi:10.1088/0004-637x/755/2/101

Cited by 95 publications

(99 citation statements)

References 44 publications

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“…In order to show the diurnal variations together with the yearly variations in one panel, the spin period is artificially set to 100 hours while the orbital period is set at 1 Earth year in Figures 9 and 11; diurnal variations with 24 hour periodicity would be smeared out when the horizontal axis spans 365 days (see Figure 3 in Fujii & Kawahara 2012 for an example of a 24 hour period). All of the parameters discussed above can be modified to fit a particular planet.…”

Section: A3 Topographic Reconstructionsmentioning

confidence: 99%

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

Way

Aleinov

Amundsen

et al. 2017

ApJS

142

141

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Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics(ROCKE-3D) is a 3-Dimensional General Circulation Model (GCM) developed at the NASA Goddard Institute for Space Studies for the modeling of atmospheres of Solar System and exoplanetary terrestrial planets. Its parent model, known as ModelE2 (Schmidt et al. 2014), is used to simulate modern and 21st Century Earth and near-term paleo-Earth climates. ROCKE-3D is an ongoing effort to expand the capabilities of ModelE2 to handle a broader range of atmospheric conditions including higher and lower atmospheric pressures, more diverse chemistries and compositions, larger and smaller planet radii and gravity, different rotation rates (slowly rotating to more rapidly rotating than modern Earth, including synchronous rotation), diverse ocean and land distributions and topographies, and potential basic biosphere functions. The first aim of ROCKE-3D is to model planetary atmospheres on terrestrial worlds within the Solar System such as paleo-Earth, modern and paleo-Mars, paleo-Venus, and Saturn's moon Titan. By validating the model for a broad range of temperatures, pressures, and atmospheric constituents we can then expand its capabilities further to 2 those exoplanetary rocky worlds that have been discovered in the past and those to be discovered in the future. We discuss the current and near-future capabilities of ROCKE-3D as a community model for studying planetary and exoplanetary atmospheres.3

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Section: A3 Topographic Reconstructionsmentioning

confidence: 99%

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

Way

Aleinov

Amundsen

et al. 2017

ApJS

142

141

View full text Add to dashboard Cite

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“…To construct a more comprehensive climate model, many additional planetary characteristics must be known. An optical mission could constrain rotation rate (Pallé et al 2008;Oakley & Cash 2009) and obliquity , 2011Fujii & Kawahara 2012). Furthermore, the presence of oceans could be inferred via their colors (Ford et al 2001;Cowan et al 2009Fujii et al 2010), polarization (Zugger et al 2010(Zugger et al , 2011, and/or specular reflection (Williams & Gaidos 2008, but confounding effects include clouds, Robinson et al 2010, andsnow, Cowan et al 2012).…”

Section: Constraining the Climate Of Hz Exoplanetsmentioning

confidence: 99%

Thermal Phases of Earth-Like Planets: Estimating Thermal Inertia From Eccentricity, Obliquity, and Diurnal Forcing

Cowan

Voigt

Abbot

2012

ApJ

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In order to understand the climate on terrestrial planets orbiting nearby Sun-like stars, one would like to know their thermal inertia. We use a global climate model to simulate the thermal phase variations of Earth analogs and test whether these data could distinguish between planets with different heat storage and heat transport characteristics. In particular, we consider a temperate climate with polar ice caps (like the modern Earth) and a snowball state where the oceans are globally covered in ice. We first quantitatively study the periodic radiative forcing from, and climatic response to, rotation, obliquity, and eccentricity. Orbital eccentricity and seasonal changes in albedo cause variations in the global-mean absorbed flux. The responses of the two climates to these global seasons indicate that the temperate planet has 3× the bulk heat capacity of the snowball planet due to the presence of liquid water oceans. The obliquity seasons in the temperate simulation are weaker than one would expect based on thermal inertia alone; this is due to cross-equatorial oceanic and atmospheric energy transport. Thermal inertia and cross-equatorial heat transport have qualitatively different effects on obliquity seasons, insofar as heat transport tends to reduce seasonal amplitude without inducing a phase lag. For an Earth-like planet, however, this effect is masked by the mixing of signals from low thermal inertia regions (sea ice and land) with that from high thermal inertia regions (oceans), which also produces a damped response with small phase lag. We then simulate thermal light curves as they would appear to a high-contrast imaging mission (TPF-I/Darwin). In order of importance to the present simulations, which use modern-Earth orbital parameters, the three drivers of thermal phase variations are (1) obliquity seasons, (2) diurnal cycle, and (3) global seasons. Obliquity seasons are the dominant source of phase variations for most viewing angles. A pole-on observer would measure peak-to-trough amplitudes of 13% and 47% for the temperate and snowball climates, respectively. Diurnal heating is important for equatorial observers (∼5% phase variations), because the obliquity effects cancel to first order from that vantage. Finally, we compare the prospects of optical versus thermal direct imaging missions for constraining the climate on exoplanets and conclude that while zero-and one-dimensional models are best served by thermal measurements, second-order models accounting for seasons and planetary thermal inertia would require both optical and thermal observations.

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“…Using a large number of space telescopes (for instance, 3 m aperture × 150), as proposed by Labeyrie (1999), is one possibility to resolve the nearby exoplanets. Even if one cannot resolve the planet directly, the reflected light curve from the Earth-like planets itself contains information on the habitat on the planetary surface, such as clouds, soil, ocean, and vegetation since they have different reflectivity (Ford et al (2001), Cowan et al (2009), Oakley & Cash (2009, , Fujii et al (2011), , Cowan et al (2011), Fujii & Kawahara (2012, and references therein). Our goal is to develop an inversion technique of annual reflected light curves to sketch a two-dimensional albedo map of the exoplanets, which will enable us to indirectly resolve the planet with a single space telescope.…”

Section: How Can We Take a Spatially Resolved Image Of An Earth-like mentioning

confidence: 99%

“…Using this fact, we developed the inversion method to retrieve the reflectivity map from the time series of reflected light curve. Since we use diurnal and annual variation of the reflected light, we call our method Spin-Orbit Tomography (SOT; , ), Fujii & Kawahara (2012). The SOT of the mock Earth light curve primary provides cloud distribution since clouds dominate reflected light as shown in Figure 1.…”

Section: Spin-orbit Tomography: Inversion Technique Of the Planetary mentioning

confidence: 99%

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Image Retrieval of Earth-like Planets from Light Curves

Kawahara

Fujii

2012

Proc. IAU

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Abstract. Surface environment of habitable exoplanets will be important for astrobiologists on exoplanets in near future. Diverse surface environments on the Earth including continents, ocean, and meteorological condition (clouds and rains) serve as the backbone of biodiversity. One of the promising approaches to know the landscape of the terrestrial exoplanets is to use scattered light of the planet through direct imaging.Since spin rotation and orbital revolution change illuminating area on planetary surface and cause time variation to disk-integrated brightness, light curves carry spatial information on the planetary surface. We propose an inversion technique of annual reflected light curves to sketch a two-dimensional albedo map of exoplanets, named the spin-orbit tomography (SOT). Applying the SOT to realistic simulations of the reflected light of an Earth-twin, we demonstrate how the SOT works. The mean cloud and continental distributions can be roughly obtained with single band photometry and difference of two-bands photometry, respectively. The SOT retrieves the planetary image without actually resolving the planet, which can be used to know the habitat of the exoplanets in near future.

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Mapping Earth Analogs From Photometric Variability: Spin-Orbit Tomography for Planets in Inclined Orbits

Cited by 95 publications

References 44 publications

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics (ROCKE-3D) 1.0: A General Circulation Model for Simulating the Climates of Rocky Planets

Thermal Phases of Earth-Like Planets: Estimating Thermal Inertia From Eccentricity, Obliquity, and Diurnal Forcing

Image Retrieval of Earth-like Planets from Light Curves

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