Solar system

Abstract:

ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 μm), and sub-millimetre sounding (near 530-625 GHz and 1067-1275 GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet.

Abstract:

In this study, we present the evolution of the properties and vertical distribution of the hazes in Jupiter's Great Red Spot (GRS), its surroundings and Oval BA from 2015 to 2021. To retrieve the main atmospheric parameters, we model the spectral reflectivity of a number of dynamically and/or spectrally interesting regions with a radiative transfer tool that uses an optimal estimator scheme. The spectra of the selected regions are obtained from high-resolution Hubble Space Telescope Wide Field Camera 3 images that cover the spectral range from 200 to 900 nm. The a priori model atmosphere used to describe the various Jovian regions is taken from Anguiano-Arteaga et al. (2021, https://doi.org/10.1029/2021JE006996) for each corresponding area. We find that the biggest variations in the GRS occur in the optical thickness of the stratospheric and tropospheric haze layers starting in 2019 and in the mean size of the tropospheric haze particles in 2018. The absorption spectra of both hazes show little variations among the analyzed regions and years, with the stratospheric haze properties seeming compatible with the chromophore proposed by Carlson et al. (2016, https://doi.org/10.1016/j.icarus.2016.03.008). We report a color change of Oval BA from red to white during these years that, according to our models, can be mostly explained in terms of a decrease in the stratospheric haze optical depth.

Abstract:

The Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter (TGO) spacecraft has been studying Mars' atmosphere since 2018. The sensitivity of the middle infrared channel (MIR) allows it to address many ardent topics and it is capable of improving and establishing upper limits for many trace species. In this work we present analysis of transmittance spectra in the 3332.5–3338.6 cm⁻¹ range with 30,000 resolution (λ∕Δλ), covering absorptions lines of three nitrogen-bearing species: ammonia (NH₃), hydrogen cyanide (HCN) and cyanoacetylene (HC₃N). According to existing models, all of those are not expected to be present in a CO₂-rich Martian atmosphere, but outgassing or unknown chemistry sources cannot be discounted. The upper limits of 14, 1.5 and 11 ppbv are obtained for NH₃, HCN and HC₃N from individual occultation measurements during the warm and dusty perihelion season of martian year 36. For the ammonia and hydrogen cyanide the upper limits are improved compared to previously published results. A search for cyanoacetylene on Mars is reported for the first time.

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 atmospheric dynamics, chemistry, and formation. We propose a novel 2D temperature parametrization consisting of a dayside and a nightside to retrieve information from near-infrared phase curves and apply the method to phase curves of WASP-43b observed by HST/Wide Field Camera 3 and Spitzer/Infra-Red Array Camera. In our scheme, the temperature is constant on isobars on the nightside and varies with cosⁿ(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 Global Circulation Model and find that 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 mixing ratio at ∼10⁻⁶.