Tyler D Robinson

NASA · Planetary Systems

Brown dwarfs are essential targets for understanding planetary and sub-stellar atmospheres across a wide range of thermal and chemical conditions. As surveys continue to probe ever deeper and as observing capabilities continue to improve, the number of known Y dwarfs—the coldest class of sub-stellar objects, with effective temperatures below about...

Exoplanets on eccentric orbits experience an incident stellar flux that can be markedly larger at periastron versus apoastron. This variation in instellation can lead to dramatic changes in atmospheric structure in regions of the atmosphere where the radiative and advective heating/cooling timescales are shorter than the orbital timescale. To explo...

Exoplanets on eccentric orbits experience an incident stellar flux that can be markedly larger at periastron versus apoastron. This variation in instellation can lead to dramatic changes in atmospheric structure in regions of the atmosphere where the radiative and advective heating/cooling timescales are shorter than the orbital timescale. To explo...

Brown dwarfs are essential targets for understanding planetary and sub-stellar atmospheres across a wide range of thermal and chemical conditions. As surveys continue to probe ever deeper, and as observing capabilities continue to improve, the number of known Y dwarfs -- the coldest class of sub-stellar objects, with effective temperatures below ab...

A critical question in astrobiology is whether exo-Earth candidates (EECs) are Earth-like, in that they originate life that progressively oxygenates their atmospheres similarly to Earth. We propose answering this question statistically by searching for O 2 and O 3 on EECs with missions such as HabEx or LUVOIR. We explore the ability of these missio...

A critical question in astrobiology is whether exoEarth candidates (EECs) are Earth-like, in that they originate life that progressively oxygenates their atmospheres similarly to Earth. We propose answering this question statistically by searching for O2 and O3 on EECs with missions such as HabEx or LUVOIR. We explore the ability of these missions...

The characterization of rocky, Earth-like planets is an important goal for future large ground- and space-based telescopes. In support of developing an efficient observational strategy, we have applied Bayesian statistical inference to interpret the albedo spectrum of cloudy true-Earth analogs that include a diverse spread in their atmospheric wate...

We are now on a clear trajectory for improvements in exoplanet observations that will revolutionize our ability to characterize their atmospheric structure, composition, and circulation, from gas giants to rocky planets. However, exoplanet atmospheric models capable of interpreting the upcoming observations are often limited by insufficiencies in t...

Earthshine is the dominant source of natural illumination on the surface of the Moon during lunar night, and at locations within permanently shadowed regions that never receive direct sunlight. As such, earthshine may enable the exploration of areas of the Moon that are hidden from solar illumination. The heat flux from earthshine may also influenc...

Thousands of planets beyond our solar system have been discovered to date, dozens of which are rocky in composition and are orbiting within the circumstellar habitable zone of their host star. The next frontier in life detection beyond our solar system will be detailed characterization of the atmospheres of potentially habitable worlds, resulting i...

Provided that sufficient resources are deployed, we can look forward to an extraordinary future in which we will characterize potentially habitable planets. Until now, we have had to base interpretations of observations on habitability hypotheses that have remained untested. To test these theories observationally, we propose a statistical comparati...

The habitable zone (HZ) is the region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. The classical HZ definition makes a number of assumptions common to the Earth, including assuming that the most important greenhouse gases for habitable planets are CO2 and H2O, habitable planets orbit main-sequence st...

Ground-based telescopes coupled with adaptive optics (AO) have been playing a leading role in exoplanet direct imaging science and technological development for the past two decades and will continue to have an indispensable role for the next decade and beyond. Over the next decade, extreme AO systems on 8-10m telescopes will 1) mitigate risk for W...

The habitable zone (HZ) is the region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. The classical HZ definition makes a number of assumptions common to the Earth, including assuming that the most important greenhouse gases for habitable planets are CO2 and H2O, habitable planets orbit main-sequence st...

Rotational mapping and glint are two proposed methods to directly detect liquid water on the surface of habitable exoplanets. However, false positives for both methods may prevent the unambiguous detection of exoplanet oceans. We use simulations of Earth as an exoplanet to introduce a combination of multiwavelength, multiphase, time-series direct-i...

The TRAPPIST-1 planetary system provides an unprecedented opportunity to study terrestrial exoplanet evolution with the James Webb Space Telescope (JWST) and ground-based observatories. Since M dwarf planets likely experience extreme volatile loss, the TRAPPIST-1 planets may have highly evolved, possibly uninhabitable atmospheres. We used a versati...

For the first time in human history, technologies have matured sufficiently to enable a mission capable of discovering and characterizing habitable planets like Earth orbiting sunlike stars other than the Sun. At the same time, such a platform would enable unique science not possible from ground-based facilities. This science is broad and exciting,...

The TRAPPIST-1 planetary system provides an unprecedented opportunity to study terrestrial exoplanet evolution with the James Webb Space Telescope (JWST) and ground-based observatories. Since M dwarf planets likely experience extreme volatile loss, the TRAPPIST-1 planets may have highly-evolved, possibly uninhabitable atmospheres. We used a versati...

The Habitable-Exoplanet Observatory (HabEx) is a candidate flagship mission being studied by NASA and the astrophysics community in preparation of the 2020 Decadal Survey. The first HabEx mission concept that has been studied is a large (~4m) diffraction-limited optical space telescope, providing unprecedented resolution and contrast in the optical...

Space-based high contrast imaging mission concepts for studying rocky exoplanets in reflected light are currently under community study. We develop an inverse modeling framework to estimate the science return of such missions given different instrument design considerations. By combining an exoplanet albedo model, an instrument noise model, and an...

Solar and thermal radiation are critical aspects of planetary climate, with gradients in radiative energy fluxes driving heating and cooling. Climate models require that radiative transfer tools be versatile, computationally efficient, and accurate. Here, we describe a technique that uses an accurate full-physics radiative transfer model to generat...

This is a white paper in response to the National Academy of Sciences "Exoplanet Science Strategy" call. We summarize recent advances in theoretical habitability studies and argue that such studies will remain important for guiding and interpreting observations. Interactions between 1-D and 3-D climate modelers will be necessary to resolve recent d...

We use coupled climate-photochemical modeling of TRAPPIST-1 planets to present a variety of evolved environmental states and their spectral discriminants, for use by upcoming M dwarf planet characterization observations.

We present two state-of-the-art models of the solar system, one corresponding to the present day and one to the Archean Eon 3.5 billion years ago. Each model contains spatial and spectral information for the star, the planets, and the interplanetary dust, extending to 50 AU from the sun and covering the wavelength range 0.3 to 2.5 micron. In additi...

Finding life on exoplanets from telescopic observations is the ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is found in future data must be expressed with probabilities, requiring a framework for biosignature assessment...

We use a new generalized, 1D RCE climate model with H2SO4 condensate cycle to model Venus-like climates of newly discovered, likely-terrestrial exoplanets, such as TRAPPIST-1 b and c. This work outputs data used for exoplanet spectral analyses.

Introduction: Atmospheric condensates are common in the Solar System, and on Earth the latent heat exchange during evaporation and condensation of aerosols helps to stabilize our climate. 1D climate models for Earth-like exoplanets typically prescribe Earth's tropospheric lapse rate for water, and sometimes the adiabatic lapse rate of CO2, but igno...

Hazes are common in known planet atmospheres, and geochemical evidence suggests early Earth occasionally supported an organic haze with significant environmental and spectral consequences. The UV spectrum of the parent star drives organic haze formation through methane photochemistry. We use a 1D photochemical-climate model to examine production of...

Recent work has shown that sulfur hazes may arise in the atmospheres of giant exoplanets due to the photolysis of H$_{2}$S. We investigate the impact such a haze would have on an exoplanet's geometric albedo spectrum using a suite of established radiative-convective, cloud, and albedo models, and how it may affect the direct imaging results of WFIR...

Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here we use 1D coupled climate-p...

HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. It will be optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and will also enable a wide range of general astr...

HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. It will be optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and will also enable a wide range of general astr...

Advancements in our understanding of exoplanetary atmospheres, from massive gas giants down to rocky worlds, depend on the constructive challenges between observations and models. We are now on a clear trajectory for improvements in exoplanet observations that will revolutionize our ability to characterize the atmospheric structure, composition, an...

Several concepts now exist for small, space-based missions to directly characterize exoplanets in reflected light. Here, we develop an instrument noise model suitable for studying the spectral characterization potential of a coronagraph-equipped, space-based telescope. We adopt a baseline set of telescope and instrument parameters appropriate for n...

The next generation of ground and space-based telescopes will image habitable planets around nearby stars. A growing literature describes how to characterize such planets with spectroscopy, but less consideration has been given to the usefulness of planet colors. Here, we investigate whether potentially Earth-like exoplanets could be identified usi...

The spectral detection of oxygen (O2) in a planetary atmosphere has been considered a robust signature of life because O2 is highly reactive on planets with Earth-like redox buffers and because significant continuous abiotic sources were thought to be implausible. However, recent work has revealed the possibility that significant O2 may build-up in...

Direct imaging of extrasolar planets with future space-based coronagraphic telescopes may provide a means of detecting companion moons at wavelengths where the moon outshines the planet. We propose a detection strategy based on the positional variation of the center of light with wavelength, "spectroastrometry." This new application of this techniq...

Characterizing the bulk atmosphere of a terrestrial planet is important for determining surface pressure and potential habitability. Molecular nitrogen (N2) constitutes the largest fraction of Earth's atmosphere and is likely to be a major constituent of many terrestrial exoplanet atmospheres. Due to its lack of significant absorption features, N2...

Several concepts now exist for small, space-based missions to directly characterize exoplanets in reflected light. Here, we develop an instrument noise model suitable for studying the spectral characterization potential of a coronagraph-equipped, space-based telescope. We adopt a baseline set of telescope and instrument parameters, including a 2 m...

One of the key factors contributing to planetary habitability is atmospheric mass. An atmosphere must maintain sufficient surface pressure for the stability of liquid water, but atmospheres that are too massive may indicate post-runaway conditions inhospitable to life. Additionally, measurements of atmospheric mass could be used to discriminate bet...

The atmosphere of a brown dwarf or extrasolar giant planet controls the spectrum of radiation emitted by the object and regulates its cooling over time. While the study of these atmospheres has been informed by decades of experience modeling stellar and planetary atmospheres, the distinctive characteristics of these objects present unique challenge...

ExoEarth yield is a critical science metric for future exoplanet imaging missions. Here we estimate exoEarth candidate yield using single visit completeness for a variety of mission design and astrophysical parameters. We review the methods used in previous yield calculations and show that the method choice can significantly impact yield estimates...

We observed Venus with the Apache Point Observatory 3.5 m telescope TripleSpec spectrograph (R = 3500, λ = 0.96-2.47 µm) on 1-3 March 2009 and on 25, 27, 30 November and 2-4 December 2010. With these observations and synthetic spectra generated with the Spectral Mapping and Atmospheric Radiative Transfer (SMART) model, we produce the first simultan...

The search for life on planets outside our solar system will use spectroscopic identification of atmospheric biosignatures. The most robust remotely-detectable potential biosignature is considered to be the detection of oxygen (O_2) or ozone (O_3) simultaneous to methane (CH_4) at levels indicating fluxes from the planetary surface in excess of tho...

Significance Hazes dramatically influence exoplanet observations by obscuring deeper atmospheric layers. This effect is especially pronounced in transit spectroscopy, which probes an exoplanet’s atmosphere as it crosses the disk of its host star. However, exoplanet observations are typically noisy, which hinders our ability to disentangle haze effe...

The Lunar CRater Observation and Sensing Satellite (LCROSS) observed the distant Earth on three occasions in 2009. These data span a range of phase angles, including a rare crescent phase view. For each epoch, the satellite acquired near-infrared and mid-infrared full-disk images, and partial-disk spectra at 0.26-0.65 μm (λ/Δλ ~ 500) and 1.17-2.48...

Distant planets in globally ice-covered, "snowball", states may depend on increases in their host stars' luminosity to become hospitable for surface life. Using a General Circulation Model (GCM), we simulated the equilibrium climate response of a planet to a range of instellations from an F-, G-, or M- dwarf star. The range of instellation that per...

A number of brown dwarfs are now known to be variable with observed amplitudes as large as 10-30% at some wavelengths. While spatial inhomogeneities in cloud coverage and thickness are likely responsible for much of the observed variability, it is possible that some of the variations arise from atmospheric temperature fluctuations instead of, or in...

In this presentation, we discuss the possibility for abiotic processes to produce O2 and O3, and examine how to discriminate between false and true positives.

Oxygen (O2) and Ozone (O3) are two of the more commonly-cited biosignature gases for future life-detection and planet characterization missions. In this presentation, we discuss the possibility for abiotic processes to produce these gases and examine the chemical and stellar contexts for these processes. Specifying these contexts and their observab...

As the possibility of discovering characterizable, habitable, Earth-like planets around Sun-like stars improves, the need for accurate model representations of such systems becomes ever more pressing. The signals of habitability will be buried within spectral information like needles in haystacks, so we present a complete model of the Solar System...

Planetary habitability is determined by the stability of liquid water at the surface, which depends on surface temperature and pressure. While molecular nitrogen (N2) constitutes the bulk of Earth’s atmosphere 78% by volume) and is the biggest contributor to surface pressure, it is also extremely hard to remotely detect. In particular, N2 lacks sig...

The presence of valleys on ancient terrains of Mars suggests that liquid water flowed on the martian surface 3.8Gyr ago or before. The above-freezing temperatures required to explain valley formation could have been transient, in response to the frequent large meteorite impacts on early Mars, or they could have been caused by long-lived greenhouse...

A minimum atmospheric temperature, or tropopause, occurs at a pressure of around 0.1 bar in the atmospheres of Earth, Titan, Jupiter, Saturn, Uranus and Neptune, despite great differences in atmospheric composition, gravity, internal heat and sunlight. In all these bodies, the tropopause separates a stratosphere with a temperature profile that is c...

We present new ground-based measurements of the Venus atmosphere below the lower cloud deck (from 0-45 km in altitude) using the Venus nightside spectral windows between 1.0 and 2.5 μm. The Venus nightside spectral windows are sensitive to minor gas abundances, cloud opacity variations, and surface thermal emission. We observed Venus over six night...

The atmospheres of terrestrial planets are expected to be in long-term radiation balance: an increase in the absorption of solar radiation warms the surface and troposphere, which leads to a matching increase in the emission of thermal radiation. Warming a wet planet such as Earth would make the atmosphere moist and optically thick such that only t...

Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. Here we explore this effect using a one dimensional (1-D), line-by-line, radiative-transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy-balance...

Due to an error at the publisher, several changes and corrections made at the proof stage were not included in the published version of the paper. The final results are not affected significantly. The coefficients used to calculate the habitable zone (HZ) limits have changed slightly (∼1.5%). Accordingly, we have provided the updated values here, a...

We explain a common "0.1 bar tropopause rule" for the thick atmospheres of planets and large moons using physically-based arguments and simple models.

Identifying terrestrial planets in the habitable zones (HZs) of other stars is one of the primary goals of ongoing radial velocity and transit exoplanet surveys and proposed future space missions. Most current estimates of the boundaries of the HZ are based on 1-D, cloud-free, climate model calculations by Kasting et al.(1993). The inner edge of th...

We present an analytic one-dimensional radiative–convective model of the thermal structure of planetary atmospheres. Our model assumes that thermal radiative transfer is gray and can be represented by the two-stream approximation. Model atmospheres are assumed to be in hydrostatic equilibrium, with a power-law scaling between the atmospheric pressu...

The ultimate and final end for Earth as a habitable planet will be the transition to a "runaway greenhouse," an apocalypse triggered by failure of the planet to maintain energy balance.

Exoplanet discoveries are occurring at an ever increasing rate, and ongoing work focuses on the characterization of these worlds. However, current technologies do not provide spatially-resolved observations of exoplanets, and the next generation of exoplanet characterization missions will only acquire disk-integrated photometry and/or spectra of th...

The inability of the Moon to efficiently circulate energy from its day side to its night side leads to large surface temperatures on its illuminated hemisphere. As a result, the Moon can contribute a significant amount of flux to spatially unresolved thermal infrared (IR) observations of the Earth-Moon system, especially at wavelengths where Earth'...

NASA's EPOXI mission observed the disc-integrated Earth and Moon to test techniques for reconnoitering extrasolar terrestrial planets, using the Deep Impact flyby spacecraft to observe Earth at the beginning and end of Northern Hemisphere spring, 2008, from a range of ∼1/6 to 1/3 AU. These observations furnish high-precision and high-cadence empiri...

Large surface temperatures on the illuminated hemisphere of the Moon can lead it to contribute a significant amount of flux to spatially unresolved infrared (IR) observations of the Earth-Moon system, especially at wavelengths where Earth's atmosphere is absorbing. We have paired the NASA Astrobiology Institute's Virtual Planetary Laboratory three-...