Solar system

Abstract:

Analysing observations of Jupiter made by VLT/MUSE (0.475 – 0.933 μm), Cassini/VIMS (0.40 – 5.15 μm), and Juno/JIRAM (2 – 5 μm), we present early results of a new combined cloud-ammonia profile model for Jupiter's equatorial atmosphere. We find this model to be consistent with all observations considered, at a range of observation geometries, within the Equatorial Zone (EZ), the North Equatorial Belt (NEB) and a North Equatorial Dark Feature (NEDF), also known as a '5-micron-hotspot'. Preliminary results suggest the presence of three main layers: 1) a deep 'Cloud-1' at 1-2 bar; 2) an upper 'Cloud-2' in the upper troposphere based at ~0.55 bar; and 3) a layer of chromophore particles situated within the Cloud-1 layer, responsible for the blue-absorption at visible wavelengths.  Our best-fit ammonia profile is closely linked with our cloud profile, with Cloud-1 coinciding with a sharp drop in ammonia abundance, perhaps associated with the formation of a H2O-NH3 'mushball' cloud, or an ammonium hydrosulphide (NH4SH) cloud, or both, and Cloud-2 coinciding with the ammonia condensation level.We find the bulk of the cloud opacity in Jupiter’s atmosphere to be in the Cloud-1 layer, based at 1-2 bar and composed of relatively large particles (r ~ 10 μm), which are highly scattering at visible wavelengths to allow sunlight to penetrate and be Rayleigh-scattered from the deeper atmosphere, but more absorbing at 5 μm. The belt/zone difference at 5 μm is accounted for by changes in the opacity of Cloud-1 and also the single-scattering albedo of these particles. We find the Cloud-2 layer, based at the ammonia condensation level, to be approximately 10 times less opaque than Cloud-1 and have an absorption band near 3 μm, which is consistent with this layer having a significant opacity of large (r ~ 10 μm) ammonia ice particles.We will present preliminary insights into the spatial distribution of these clouds over the regions considered and their implications for our understanding of Jupiter’s chromophores and upper-level hazes.

Abstract:

We present a calibrated catalog of Cassini Visible and Infrared Mapping Spectrometer (VIMS) observations of Jupiter, together with the processing workflow used to generate the final publicly available products. Starting from the raw VIMS cubes, the workflow produces radiometrically consistent multiextension Flexible Image Transport System files and includes a revised visible-channel calibration, a revised infrared-channel calibration that resolves a subset of problematic cases not satisfactorily treated by the standard Integrated Software for Imagers and Spectrometers pipeline, corrections for pointing-related misalignments between spectral cubes and geometric backplanes, and customized dark signal correction strategies. The final products include calibrated spectral cubes together with geometry backplanes and wavelength information for subsequent scientific analysis. We assess the consistency of the calibrated products through internal validation tests and comparisons with independent reference spectra from the literature. The resulting products provide a uniform and validated data set of Cassini VIMS Jupiter observations for community use. The full catalog is available as a public dataset at doi:10.5281/zenodo.19223781.

Abstract:

The main belt asteroid (52246) Donaldjohanson (DJ) is a likely member of the Erigone asteroid family. This implies that DJ is a fragment of a larger parent body that was destroyed in a collision about 155 million years ago. We report observations taken during a flyby of DJ by the Lucy spacecraft. We found that DJ is composed of two heavily cratered lobes, connected by a smoother neck, with overall dimensions 8.8 kilometers (km) by 4.4 km by 3.1 km. The crater density is consistent with the Erigone family's age, except for craters <0.4 km, which have been preferentially erased. DJ rotates slowly in a tumbling state, likely owing to spin-down by radiative forces. Surface spectra show iron-bearing phyllosilicates, indicating moderate aqueous evolution on the parent body.

Abstract:

Remote spectroscopy is used to characterize the mineralogy and infer the history of planetary bodies. Carbonaceous asteroids, such as B‐type (101955) Bennu, represent the earliest stages of planet formation. B types have a blue (negative) spectral slope and comprise <5% of asteroids. Samples from Bennu returned by the OSIRIS‐REx spacecraft complement remote observations of this rare population. We show here, using laboratory spectra that are directly comparable to spacecraft data, that OSIRIS‐REx accurately determined Bennu's dust content and most of its surface composition. However, spectra of the asteroid exhibit stronger water absorptions than those of bulk samples, possibly due to hydrous, Mg‐rich phosphate or solar wind implantation at Bennu's uppermost surface. Bennu samples spectrally resemble the most aqueously altered carbonaceous meteorites and samples of (162173) Ryugu, indicating similarly pervasive aqueous alteration. However, one carbon‐enriched Bennu stone does not appear to have a spectral analog among Ryugu samples or meteorites. Our findings demonstrate the leverage obtained using a wide range of wavelengths and that sample analysis anchors the interpretations of remote sensing, leading to more robust characterization of planetary surface composition and evolution.

Abstract:

The origin of the red colouration in Jupiter's Great Red Spot (GRS) is a long-standing question in planetary science. While several candidate chromophores have been proposed, no clear conclusions have been reached regarding its nature, evolution, or relationship to atmospheric dynamics. In this work, we perform microphysical simulations of the reddish haze over the GRS and quantify the production rates and timescales required to sustain it. Matching the previously reported chromophore column mass and effective radius in the GRS requires column-integrated injection fluxes in the range 1×10⁻¹²–7×10⁻¹² kg m⁻² s⁻¹, under low upwelling velocities in the upper troposphere (v<inf>trop</inf>≲1.5×10⁻⁴ m s⁻¹) and particle charges of at least 20 electrons/μm. Such rates exceed the mass flux that standard photochemical models of Jupiter currently supply via NH<inf>3</inf>–C<inf>2</inf>H<inf>2</inf> photochemistry at 0.1–0.2 bar, the most popular chromophore pathway in recent literature. We find a lower limit of 7 years on the haze formation time. We also assess commonly used size and vertical distribution parameterisations for the chromophore haze, finding that eddy diffusion prevents the long-term confinement of a thin layer and that the extinction is dominated by particles that can be represented by a single log-normal size distribution.