Search Publications
Accurate Machine-learning Atmospheric Retrieval via a Neural-network Surrogate Model for Radiative Transfer
Arney, Giada N.; Domagal-Goldman, Shawn D.; Harrington, Joseph +8 more
Atmospheric retrieval determines the properties of an atmosphere based on its measured spectrum. The low signal-to-noise ratios of exoplanet observations require a Bayesian approach to determine posterior probability distributions of each model parameter, given observed spectra. This inference is computationally expensive, as it requires many exec…
A New UV Spectral Feature on Europa: Confirmation of NaCl in Leading-hemisphere Chaos Terrain
Alday, Juan; Roth, Lorenz; Brown, Michael E. +6 more
Recent visible-wavelength observations of Europa's surface obtained with the Hubble Space Telescope (HST) revealed the presence of an absorption feature near 450 nm that appears spatially correlated with leading-hemisphere chaos terrain. This feature was interpreted to reflect the presence of irradiated sodium chloride ultimately sourced from the …
An Open-source Bayesian Atmospheric Radiative Transfer (BART) Code. III. Initialization, Atmospheric Profile Generator, Post-processing Routines
Cubillos, Patricio E.; Blecic, Jasmina; Challener, Ryan C. +12 more
This and companion papers by Harrington et al. and Cubillos et al. describe an open-source retrieval framework, Bayesian Atmospheric Radiative Transfer (BART), available to the community under the reproducible-research license via https://github.com/exosports/BART. BART is a radiative transfer code (transit; https://github.com/exosports/transit; R…
Mid-ultraviolet Hubble Observations of Europa and the Global Surface Distribution of SO2
Alday, Juan; Roth, Lorenz; McGrath, Melissa A. +6 more
We present spatially resolved reflectance spectra of Europa's surface in the wavelength range of 210-315 nm obtained by the Hubble Space Telescope Imaging Spectrograph in 2018 and 2019. These data provide the first high-quality, near-global spectral observations of Europa from 210 to 240 nm. They show that the reflectance of Europa's leading, trai…
The Influence of Temperature and Photobleaching on Irradiated Sodium Chloride at Europa-like Conditions
Brown, Michael E.; Denman, William T. P.; Trumbo, Samantha K.
Europa's leading-hemisphere chaos regions have a spectral feature at 450 nm that has been attributed to absorption by crystal defects in irradiated sodium chloride, known as F-centers. Some discrepancies exist between the laboratory data of irradiated sodium chloride and the observations, including a ~10 nm shift in central wavelength of the F-cen…
Orbits and Occultation Opportunities of 15 TNOs Observed by New Horizons
Singer, Kelsi N.; Stern, S. Alan; Fraser, Wesley C. +10 more
We present high-precision orbits for 15 trans-Neptunian objects (TNOs) that have been observed by NASA's New Horizons spacecraft at distances from 0.092 to 2.2 au. We also give predictions of 66 future opportunities to observe stellar occultations by them in late 2021-2029, eight of which are possible to observe from the United States. Observation…
Dust Evolution in the Coma of Distant, Inbound Comet C/2017 K2 (PANSTARRS)
Kolokolova, Ludmilla; Zhang, Qicheng; Ye, Quanzhi +1 more
C/2017 K2 (PANSTARRS) is an Oort Cloud comet previously observed to be active at heliocentric distances r > 20 au on what is likely its first passage through the inner solar system. We observed the comet on 2021 March 19-20 at r = 6.82 au preperihelion and 8.°35 phase angle with the Hubble Space Telescope (HST), and obtained high spatial resolu…
Spectroscopic Mapping of Io's Surface with HST/STIS: SO2 Frost, Sulfur Allotropes, and Large-scale Compositional Patterns
Brown, Michael E.; Trumbo, Samantha K.; Davis, M. Ryleigh +1 more
Io's intense volcanic activity results in one of the most colorful surfaces in the solar system. Ultraviolet and visible-wavelength observations of Io are critical to uncovering the chemistry behind its volcanic hues. Here, we present global, spatially resolved ultraviolet-visible spectra of Io from the Space Telescope Imaging Spectrograph on the …
Ultraviolet Spectroscopy of Lucy Mission Targets with the Hubble Space Telescope
Emery, Joshua P.; Grundy, Will M.; Humes, Oriel A. +1 more
The recently launched Lucy mission aims to understand the dynamical history of the solar system by examining the Jupiter Trojans, a population of primitive asteroids co-orbital with Jupiter. Using the G280 grism on the Hubble Space Telescope's Wide Field Camera 3, we obtained near-ultraviolet spectra of four of the five Lucy mission targets-(617) …