A5051408424- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Atmospheric Ozone and Climate
- Astrophysics and Star Formation Studies
- Planetary Science and Exploration
- Spectroscopy and Laser Applications
- Isotope Analysis in Ecology
- Space Science and Extraterrestrial Life
- Space Exploration and Technology
- Atmospheric and Environmental Gas Dynamics
- History and Developments in Astronomy
- Astronomical Observations and Instrumentation
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Spacecraft Design and Technology
- Solar and Space Plasma Dynamics
- Advanced MRI Techniques and Applications
- Advanced Neuroimaging Techniques and Applications
- Atmospheric chemistry and aerosols
- Spaceflight effects on biology
- Paleontology and Stratigraphy of Fossils
- Methane Hydrates and Related Phenomena
- Scientific Research and Discoveries
- SAS software applications and methods
University of Arizona
2022-2025
University of Washington
2013-2025
Northern Arizona University
2017-2024
Jet Propulsion Laboratory
2016-2024
Planetary Science Institute
2014-2024
Baycrest Hospital
2023-2024
Cornell University
2024
NASA Astrobiology Institute
2011-2022
University of Windsor
2022
Western University
2022
Identifying terrestrial planets in the habitable zones (HZs) of other stars is one primary goals ongoing radial velocity and transit exoplanet surveys proposed future space missions. Most current estimates boundaries HZ are based on 1-D, cloud-free, climate model calculations by Kasting et al.(1993). The inner edge al.(1993) was determined loss water, outer maximum greenhouse provided a CO2 atmosphere. A conservative estimate for width from this our Solar system 0.95-1.67 AU. Here, an...
Abstract Nine transiting Earth-sized planets have recently been discovered around nearby late-M dwarfs, including the TRAPPIST-1 and two by MEarth survey, GJ 1132b LHS 1140b. These are smallest known that may atmospheres amenable to detection with James Webb Space Telescope ( JWST ). We present model thermal emission transmission spectra for each planet, varying composition surface pressure of atmosphere. base elemental compositions on those Earth, Titan, Venus calculate molecular assuming...
The search for life on planets outside our solar system will use spectroscopic identification of atmospheric biosignatures. most robust remotely detectable potential biosignature is considered to be the detection oxygen (O2) or ozone (O3) simultaneous methane (CH4) at levels indicating fluxes from planetary surface in excess those that could produced abiotically. Here we an altitude-dependent photochemical model with enhanced lower boundary conditions necessary carefully explore abiotic O2...
The atmosphere of a brown dwarf or extrasolar giant planet controls the spectrum radiation emitted by object and regulates its cooling over time. While study these atmospheres has been informed decades experience modeling stellar planetary atmospheres, distinctive characteristics objects present unique challenges to forward modeling. In particular, complex chemistry arising from molecule-rich molecular opacity line lists (sometimes running 10 billion absorption lines more) multiple...
Abstract Hazes are common in known planetary atmospheres, and geochemical evidence suggests that early Earth occasionally supported an organic haze with significant environmental spectral consequences. The UV spectrum of the parent star drives formation through methane photochemistry. We use a 1D photochemical-climate model to examine production fractal on Archean Earth-analogs habitable zones several stellar types: modern Sun, AD Leo (M3.5V), GJ 876 (M4V), ϵ Eridani (K2V), σ Boötis (F2V)....
The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of 2030s. For first time in human history, technologies have matured sufficiently enable an affordable space-based telescope mission capable discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars order search for signs habitability biosignatures. Such a can also equipped with instrumentation that will broad exciting general astrophysics planetary science not possible...
Surrogate-based-optimization methods provide a means to achieve high-fidelity design optimization at reduced computational cost by using model in combination with lower-fidelity models that are less expensive evaluate.This paper presents provably convergent trust-region model-management methodology for variableparameterization models: is, which the parameters defined over different spaces.Corrected space mapping is introduced as method map between variable-parameterization spaces.It then...
When Earth-mass extrasolar planets first become detectable, one challenge will be to determine which of these worlds harbor liquid water, a widely used criterion for habitability. Some the observations consist disc-averaged, time-resolved broadband photometry. To simulate such data, Deep Impact spacecraft obtained light curves Earth at seven wavebands spanning 300–1000 nm as part EPOXI mission opportunity. In this paper, we analyze disc-integrated curves, treating if it were an exoplanet,...
The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric moderate resolution near-infrared (NIR) spectroscopic observations Earth. These remote provide a rigorous validation whole-disk Earth model simulations used better understand remotely detectable extrasolar planet characteristics. We have these data upgrade, correct, validate NASA Astrobiology Institute's Virtual Planetary Laboratory...
Planetary climate can be affected by the interaction of host star spectral energy distribution with wavelength-dependent reflectivity 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 seasonally varying, 1-D energy-balance model. A three-dimensional general circulation is also used atmosphere's response changes in incoming stellar radiation, or instellation, surface albedo. Using...
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, may have highly-evolved, possibly uninhabitable atmospheres. We used a versatile, 1D terrestrial-planet climate model line-by-line radiative transfer mixing length convection (VPL Climate) coupled photochemistry simulate environmental states for...
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 25, 27, 30 November 2–4 December 2010. With these observations synthetic spectra generated Spectral Mapping Atmospheric Radiative Transfer model, we produce first simultaneous maps of cloud opacity, acid concentration, water vapor (H2O), hydrogen chloride (HCl), carbon dioxide (CO), carbonyl sulfide (OCS), sulfur (SO2) abundances in Venusian lower...
Abstract 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 exoplanet albedo model, noise and ensemble Markov chain Monte Carlo sampler, we explore retrievals atmospheric planetary properties Earth twins as a function signal-to-noise ratio (S/N) resolution (...
We investigate the chemical stability of CO2-dominated atmospheres desiccated M dwarf terrestrial exoplanets using a one-dimensional photochemical model. Around Sun-like stars, CO2 photolysis by Far-UV (FUV) radiation is balanced recombination reactions that depend on water abundance. Planets orbiting stars experience more FUV radiation, and could be depleted in due to dwarfs' prolonged, high-luminosity pre-main sequences. show that, for water-depleted planets, catalytic cycle relying H2O2...
HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration the 2020 Decadal Survey Astronomy and Astrophysics possible launch 2030s. It will optimized direct imaging spectroscopy potentially habitable exoplanets, also enable a wide range general astrophysics science. aims fully characterize planetary systems around nearby solar-type stars first time, including rocky planets, water worlds, gas giants, ice faint circumstellar debris...
Several concepts now exist for small, space-based missions to directly characterize exoplanets in reflected light. Here, we develop an instrument noise model suitable studying the spectral characterization potential of a coronagraph-equipped, telescope. We adopt baseline set telescope and parameters appropriate near-future planned like WFIRST-AFTA, including 2 m diameter primary aperture, operational wavelength range 0.4-1.0 um, resolution 70, apply our variety models different planet types,...
Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Cen orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or not be habitable. Here, we use 1-D coupled climate-photochemical models generate self-consistent atmospheres for several scenarios, including high-O2, high-CO2, more Earth-like atmospheres, with both oxic...
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 rare crescent view. For each epoch, satellite acquired near-infrared mid-infrared full-disk images, partial-disk spectra at 0.26-0.65 microns (R~500) 1.17-2.48 (R~50). Spectra show strong absorption features due to water vapor ozone, which is biosignature gas. We perform significant recalibration UV-visible provide first...
ExoEarth yield is a critical science metric for future exoplanet imaging missions. Here we estimate exoEarth candidate using single visit completeness variety of mission design and astrophysical parameters. We review the methods used in previous calculations show that method choice can significantly impact estimates as well how responds to introduce method, called Altruistic Yield Optimization, optimizes target list exposure times maximize yield, adapts maximally changes parameters,...
Abstract Solar system observations that serve as analogs for exoplanet remote sensing data can provide important opportunities to validate ideas and models related environments. Critically, unlike true observations, solar analog benefit from available high-quality ground- or orbiter-derived “truth” constraints enable strong validations of interpretation tools. In this work, we first present a versatile atmospheric retrieval suite, capable application reflected light, thermal emission,...
High-altitude clouds and hazes are integral to understanding exoplanet observations, proposed explain observed featureless transit spectra. However, it is difficult make inferences from these data because of the need disentangle effects gas absorption haze extinction. Here, we turn quintessential hazy world, Titan, clarify how high-altitude influence We use solar occultation observations Titan's atmosphere Visual Infrared Mapping Spectrometer aboard National Aeronautics Space...