HCO+ Dissociative Recombination: A Significant Driver of Nonthermal Hydrogen Loss at Mars

Journal of Geophysical Research Planets American Geophysical Union (AGU) 128:1 (2023)

Authors:

Bethan S Gregory, Rodney D Elliott, Justin Deighan, Hannes Gröller, Michael S Chaffin

An intense narrow equatorial jet in Jupiter's lower stratosphere observed by JWST

NATURE ASTRONOMY (2023)

Authors:

Ricardo Hueso, Agustin Sanchez-Lavega, Thierry Fouchet, Imke de Pater, Arrate Antunano, Leigh N Fletcher, Michael H Wong, Pablo Rodriguez-Ovalle, Lawrence A Sromovsky, Patrick M Fry, Glenn S Orton, Sandrine Guerlet, Patrick GJ Irwin, Emmanuel Lellouch, Jake Harkett, Katherine de Kleer, Henrik Melin, Vincent Hue, Amy A Simon, Statia Luszcz-Cook, Kunio M Sayanagi

Clouds and spots

ASTRONOMY & GEOPHYSICS 64:6 (2023) 8-8

Testing 2D temperature models in Bayesian retrievals of atmospheric properties from hot Jupiter phase curves

Monthly notices of the Royal Astronomical Society

Authors:

Jingxuan Yang, Patrick G.J. Irwin, Joanna K. Barstow

Abstract:

Spectroscopic phase curves of transiting hot Jupiters are spectral measurements at multiple orbital phases, giving a set of disc-averaged spectra that probe multiple hemispheres. By fitting model phase curves to observations, we can constrain the atmospheric properties of hot Jupiters such as molecular abundance, aerosol distribution and thermal structure, which offer insights into their dynamics, chemistry, and formation. In this work, we propose a novel 2D temperature scheme consisting of a dayside and a nightside to retrieve information from near-infrared phase curves, and apply the scheme to phase curves of WASP-43b observed by HST/WFC3 and Spitzer/IRAC. In our scheme, temperature is constant on isobars on the nightside and varies with cos^n(longitude/ϵ) on isobars on the dayside, where n and ϵ are free parameters. We fit all orbital phases simultaneously using the radiative transfer package NEMESISPY coupled to a Bayesian inference code. We first validate the performance of our retrieval scheme with synthetic phase curves generated from a GCM, and find our 2D scheme can accurately retrieve the latitudinally-averaged thermal structure and constrain the abundance of H2O and CH4. We then apply our 2D scheme to the observed phase curves of WASP-43b and find: (1) the dayside temperature-pressure profiles do not vary strongly with longitude and are non-inverted; (2) the retrieved nightside temperatures are extremely low, suggesting significant nightside cloud coverage; (3) the H2O volume mixing ratio is constrained to 5.6×10^−5--4.0×10^−4, and we retrieve an upper bound for CH4 at ∼10^−6.

A two-Martian years survey of the water vapor saturation state on Mars based on ACS NIR/TGO occultations

Journal of Geophysical Research: Planets American Geophysical Union 128:1 (2022) e2022JE007348

Authors:

Anna Fedorova, Franck Montmessin, Alexander Trokhimovskiy, Mikhail Luginin, Oleg Korablev, Juan Alday, Denis Belyaev, James Holmes, Franck Lefevre, Kevin Olsen, Andrey Patrakeev, Alexey Shakun

Abstract:

On Mars, condensation is the major factor constraining the vertical distribution of water vapor. Recent measurements of water and temperature profiles showed that water can be strongly supersaturated at and above the level where clouds form during the aphelion and perihelion seasons. Since 2018, the near-infrared spectrometer (NIR) of the Atmospheric Chemistry Suite onboard the Trace Gas Orbiter has measured H2O and temperature profiles using solar occultation in the infrared from below 10 to 100 km of altitude. Here, we provide the first long-term monitoring of the water saturation state. The survey spans 2 Martian years from Ls = 163° of MY34 to Ls = 170° of MY36. We found that water is often supersaturated above aerosol layers. In the aphelion season, the water mixing ratio above 40 km in the mid-to-high latitudes was below 3 ppmv and yet is found to be supersaturated. Around the perihelion, water is also supersaturated above 60 km with a mixing ratio of 30–50 ppmv. Stronger saturation is observed during the dusty season in MY35 compared to what was observed in MY34 during the Global Dust Storm and around the perihelion. Saturation varied between the evening and morning terminators in response to temperature modulation imparted by thermal tides. Although water vapor is more abundant in the evening, colder morning temperatures induce a daily peak of saturation. This data set establishes a new paradigm for water vapor on Mars, revealing that supersaturation is nearly ubiquitous, particularly during the dust season, thereby promoting water escape on an annual average.