Hot super Earths are exoplanets with short orbital periods ($<$ 10 days), heated by their host stars to temperatures high enough for their rocky surfaces to become molten. A few hot super Earths exhibit high geometric albedos ($>$ 0.4) in the Kepler band (420-900 nm). We are motivated to determine whether reflection from molten lava and quenched glasses (a product of rapidly cooled lava) on the surfaces of hot super Earths contributes to the observationally inferred high geometric albedos. We experimentally measure reflection from rough and smooth textured quenched glasses of both basalt and feldspar melts. For lava reflectance values, we use specular reflectance values of molten silicates from non-crystalline solids literature. Integrating the empirical glass reflectance function and non-crystalline solids reflectance values over the dayside surface of the exoplanet at secondary eclipse yields an upper limit for the albedo of a lava-quenched glass planet surface of $\sim $0.1. We conclude that lava planets with solid (quenched glass) or liquid (lava) surfaces have low albedos. The high albedos of some hot super Earths are most likely explained by atmospheres with reflective clouds (or, for a narrow range of parameter space, possibly Ca/Al oxide melt surfaces). Lava planet candidates in TESS data can be identified for follow-up observations and future characterization.
The Kepler mission has made an important observation, the first detection of photons from a terrestrial planet by observing its phase curve (Kepler-10b). This opens a new field in exoplanet science: the possibility to get information about the atmosphere and surface of rocky planets, objects of prime interest. In this letter, we apply the Lava-ocean model to interpret the observed phase curve. The model, a planet with no atmosphere and a surface partially made of molten rocks, has been proposed for planets of the class of CoRoT-7b, i.e. rocky planets very close to their star (at few stellar ra…
JWST MIRI reveals a potential atmosphere on the ultra-hot rocky planet TOI-431b
University of Maryland（马里兰大学）；University of Chicago（芝加哥大学）；Instituto de Astrofísica de Andalucía (IAA-CSIC)（安达卢西亚天体物理研究所）；University of Birmingham（伯明翰大学）；Carnegie Science（卡内基科学研究所）；Space Telescope Science Institute（太空望远镜科学研究所）；Peking University（北京大学）
In this paper we propose an analytic function for the spherical albedo values of airless and near-airless magma ocean planets (AMOPs). We generated 2-D fractal surfaces with varying compositions onto which we individually threw 10,000 light rays. Using an approximate form of the Fresnel equations we measured how much of the incident light was reflected. Having repeated this algorithm on varying surface roughnesses we find the spherical albedo as a function of the Hurst exponent, the geochemical composition of the magma, and the wavelength. As a proof of concept, we used our model on Kepler-10b…
The magma ocean concept was first conceived to explain the geology of the Moon, but hemispherical or global oceans of silicate melt could be a widespread "lava world" phase of rocky planet accretion, and could persist on planets on short-period orbits around other stars. The formation and crystallization of magma oceans could be a defining stage in the assembly of a core, origin of a crust, initiation of tectonics, and formation of an atmosphere. The last decade has seen significant advances in our understanding of this phenomenon through analysis of terrestrial and extraterrestrial samples, p…
Lava worlds belong to a class of short orbital period planets reaching dayside temperatures high enough to melt their silicate crust. Theory predicts that the resulting lava oceans outgas their volatile components, attaining equilibrium with the overlying vapour. This creates a tenuous, silicate-rich atmosphere that may be confined to the permanent dayside of the planet. The launch of JWST will provide the much needed sensitivity and spectral coverage to characterise these worlds. In this paper, we assess the observability of characterisable spectral features by self-consistently modelling sil…
Three-Dimensional Ocean Dynamics and Detectability of Tidally Locked Lava Worlds
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；Department of Earth, Atmosphere and Planetary Science, MIT（麻省理工学院地球、大气与行星科学系）；Peking University（北京大学）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；State Key Laboratory of Dark Matter Physics, Shanghai Jiao Tong University（上海交通大学暗物质物理全国重点实验室）
Super-Earths with solid surfaces such CoRot-7b and Kepler-10b are expected to be extremely hot. It has been suggested that they must be atmosphere-free and that a lava ocean is present on their hot dayside. Here, we use several dedicated thermal models to study how observations with NIRSPEC on the JWST could further confirm and constrain, or reject the atmosphere-free lava ocean planet model for very hot super-Earths. Using CoRoT-7b as a working case, we explore the consequences on the phase-curve of a non tidal-locked rotation, with/without an atmosphere, and for different values of the albed…
The recent first measurements of the reflection of the surface of a lava world provides an unprecedented opportunity to investigate different stages of rocky planet evolution. The spectral features of the surfaces of rocky lava world exoplanets give insights into their evolution, mantle composition and inner workings. However, no database exists yet that contains spectral reflectivity and emission of a wide range of potential exoplanet surface materials. Here we first synthesized 16 potential exoplanet surfaces, spanning a wide range of chemical compositions based on potential mantle material …
Highly volcanic exoplanets, which can be variously characterized as 'lava worlds', 'magma ocean worlds', or 'super-Ios' are high priority targets for investigation. The term 'lava world' may refer to any planet with extensive surface lava lakes, while the term 'magma ocean world' refers to planets with global or hemispherical magma oceans at their surface. 'Highly volcanic planets', including super-Ios, may simply have large, or large numbers of, active explosive or extrusive volcanoes of any form. They are plausibly highly diverse, with magmatic processes across a wide range of compositions, …
Photometric phase curves provide an important window onto exoplanetary atmospheres and potentially even their surfaces. With similar amplitudes to occultations but far longer baselines, they have a higher sensitivity to planetary photons at the expense of a more challenging data reduction in terms of long-term stability. In this work, we introduce a novel non-parametric algorithm dubbed "phasma" to produce clean, robust exoplanet phase curves and apply it to 115 Neptunian and 50 Terran exoplanets observed by Kepler. We stack the signals to further improve signal-to-noise, and measure an averag…
Mantle Convection and Nightside Volcanism on Lava World K2-141 b
University of Oxford（牛津大学）；Bayerisches Geoinstitut, University of Bayreuth（拜罗伊特大学巴伐利亚地球研究所）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；Institute of Geophysics, Department of Earth and Planetary Sciences, ETH Zurich（苏黎世联邦理工学院地球与行星科学系地球物理研究所）；School of Physics and Astronomy, University of Leeds（利兹大学物理与天文学学院）
The energy balance and climate of planets can be affected by the reflective properties of their land, ocean, and frozen surfaces. Here we investigate the effect of host star spectral energy distribution (SED) on the albedo of these surfaces using a one-dimensional (1-D) energy balance model (EBM). Incorporating spectra of M-, K-, G- and F-dwarf stars, we determined the effect of varying fractional and latitudinal distribution of land and ocean surfaces as a function of host star SED on the overall planetary albedo, climate, and ice-albedo feedback response. While noting that the spatial distri…
Inferring and Interpreting the Visual Geometric Albedo and Phase Function of Earth
Lunar & Planetary Laboratory, University of Arizona（亚利桑那大学月球与行星实验室）；Habitability, Atmospheres, and Biosignatures Laboratory, University of Arizona（亚利桑那大学宜居性、大气和生物标志物实验室）；NASA Nexus for Exoplanet System Science Virtual Planetary Laboratory, University of Washington（华盛顿大学NASA系外行星系统科学虚拟行星实验室）
The exploration of the Pluto-Charon system by the New Horizons spacecraft represents the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" of distant ice-rich bodies. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that reveals surface albedo variegations larger than any other Solar System world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0, and the …
Evidence for an Atmosphere on the Ultra-Short Period super-Earth HD 3167 b
University of Chicago（芝加哥大学）；University of Maryland, College Park（马里兰大学帕克分校）；Center for Astrophysics | Harvard & Smithsonian（哈佛与史密森尼天体物理中心）；University of Birmingham（伯明翰大学）
Evolutionary pathways toward survival of a thick CO2- or SO2-rich atmosphere on the lava world TOI-561 b
Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡佩恩天文研究所）；Earth and Planets Laboratory, Carnegie Institution for Science（卡内基科学机构地球与行星实验室）；The Observatories of the Carnegie Institution for Science（卡内基科学机构天文台）；Institute of Astronomy, University of Cambridge（剑桥大学天文学研究所）；School of Physics & Astronomy, University of Birmingham（伯明翰大学物理与天文学院）；Waterloo Centre for Astrophysics and Department of Physics and Astronomy, University of Waterloo（滑铁卢大学天体物理学中心及物理与天文学系）
The Radius, Composition, Albedo, and Absolute Magnitude of Planet Nine Based on Exoplanets with Teq less than 600 K and the Planet Nine Reference Population 3.0
Low-albedo, hydrated objects dominate the list of the largest asteroids. These objects have varied spectral shapes in the 3-$μ$m region, where diagnostic absorptions due to volatile species are found. Dawn's visit to Ceres has extended the view shaped by ground-based observing, and shown that world to be a complex one, potentially still experiencing geological activity. We present 33 observations from 2.2-4.0 $μ$m of eight large (greater than 200 km diameter) asteroids from the C spectral complex, with spectra inconsistent with the hydrated minerals we see in meteorites. We characterize their …
Many of the confirmed short period super-Earths and smaller sub-Neptunes are sufficiently irradiated for the surface silicates to be sustained in a long-lasting molten state. While there is no direct evidence of magma ocean influence on exoplanets, theory suggests that due to outgassing and diverse evolution paths, a wide range of resulting atmospheric compositions should be possible. Atmospheric contamination caused by the outgassing of the underlying magma ocean is potentially detectable using low resolution spectroscopy. The James Webb Space Telescope provides the necessary spectral coverag…
We present EOS, a procedure for determining the Outgoing Longwave Radiation (OLR) and top-of-atmosphere (TOA) albedo for a wide range of conditions expected to be present in the atmospheres of rocky planets with temperate conditions. EOS is based on HELIOS and HELIOS-K, which are novel and publicly available atmospheric radiative transfer (RT) codes optimized for fast calculations with GPU processors. These codes were originally developed for the study of giant planets. In this paper we present an adaptation for applications to terrestrial-type, habitable planets, adding specific physical reci…
Retrieving the Red Edge on Earth-like Planets with Heterogeneous Clouds and Surfaces
Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；ETH Zurich, Institute for Particle Physics & Astrophysics（苏黎世联邦理工学院粒子物理与天体物理研究所）；Centre for Planetary Habitability, Department of Geoscience, University of Oslo（奥斯陆大学地质科学系行星宜居性中心）；Department of Astronomy & Astrophysics, The Pennsylvania State University（宾夕法尼亚州立大学天文与天体物理学系）；Center for Exoplanets and Habitable Worlds, The Pennsylvania State University（宾夕法尼亚州立大学系外行星与宜居世界中心）；Institute for Computational and Data Science, The Pennsylvania State University（宾夕法尼亚州立大学计算与数据科学研究院）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）
Rocky exoplanets orbiting in the habitable zone (HZ) of nearby M dwarfs provide unique opportunities for characterizing their atmospheres and searching for biosignature gases. TRAPPIST-1e, a temperate Earth-sized exoplanet in the HZ of a nearby M dwarf, is arguably the most favorable target for ground- and space-based atmospheric characterization by the extremely large telescopes (ELTs) and the James Webb Space Telescope (JWST). To inform future observations in reflected and emitted lights using these upcoming telescopes, we simulate the high-resolution reflection and emission spectra for TRAP…
We present a comprehensive analysis of planetary phase variations, including possible planetary light offsets, using eighteen quarters of data from the Kepler space telescope. After correcting for systematics, we found fourteen systems with significant detections in each of the phase curve components: planet's phase function, secondary eclipse, Doppler boosting and ellipsoidal variations. We model the full phase curve simultaneously, including primary and secondary transits, and derive albedos, day- and night-side temperatures and planet masses. Most planets manifest low optical geometric albe…
Reflected light photometry of terrestrial exoplanets could reveal the presence of oceans and continents, hence placing direct constraints on the current and long-term habitability of these worlds. Inferring the albedo map of a planet from its observed light curve is challenging because different maps may yield indistinguishable light curves. This degeneracy is aggravated by changing clouds. It has previously been suggested that disk-integrated photometry spanning multiple days could be combined to obtain a cloud-free surface map of an exoplanet. We demonstrate this technique as part of a Bayes…
One of the primary questions when characterizing Earth-sized and super-Earth-sized exoplanets is whether they have a substantial atmosphere like Earth and Venus or a bare-rock surface like Mercury. Phase curves of the planets in thermal emission provide clues to this question, because a substantial atmosphere would transport heat more efficiently than a bare-rock surface. Analyzing phase curve photometric data around secondary eclipse has previously been used to study energy transport in the atmospheres of hot Jupiters. Here we use phase curve, Spitzer time-series photometry to study the therm…
[Abridged] To simulate the kinds of observations that will eventually be obtained for exoplanets, the Deep Impact spacecraft obtained light curves of Earth at seven wavebands spanning 300-1000 nm as part of the EPOXI mission of opportunity. In this paper we analyze disc-integrated light curves, treating Earth as if it were an exoplanet, to determine if we can detect the presence of oceans and continents. We present two observations each spanning one day, taken at gibbous phases. The rotation of the planet leads to diurnal albedo variations of 15-30%, with the largest relative changes occuring …
From life on other planets to virtual classrooms this thesis spans a wide array of research topics all based on how we see other worlds. Our understanding of everything from moon phases, the planets in our Solar System, and exoplanet atmospheres come from our interpretation of light and one day, our knowledge of light will be used as evidence for the discovery of life on another planet. In the time before we scattered rovers, landers, and brave souls across the Solar System we only knew of the planets and moons from the light they reflected from the Sun back to us. We are in much the same situ…
