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Philippa M. Molyneux

Publications and source records attributed to Philippa M. Molyneux.

5 recordsLinked to original sources
arXiv2026

The Ultraviolet Spectrograph on ESA's Jupiter Icy Moons Explorer Mission (JUICE-UVS)

The Jupiter Icy Moons Explorer (JUICE) mission, led by ESA, has an Ultraviolet Spectrograph (JUICE-UVS) contributed by NASA and built at Southwest Research Institute. JUICE-UVS is designed to provide a diversity of measurements to further our understanding of the potential habitability of icy ocean worlds at Jupiter and to study Jupiter and the Jovian system as an archetype for gas giants. JUICE-UVS observes photons in the 50-204 nm wavelength range at moderate spectral and spatial resolution along a 7.5 deg slit composed of 7.3 deg x 0.1 deg and 0.2 deg x 0.2 deg contiguous sections. JUICE-UVS performs a comprehensive study of icy satellite atmospheres, plumes, surfaces, and local space environments; Jupiter's atmosphere and aurora; Io and its Io Plasma Torus; and other Jupiter system targets (rings, small moons, etc.) as available. The variety of observational techniques employed include: nadir push-broom imaging, disk scans, limb stares, stellar and solar occultations, Jupiter transit observations, and neutral cloud/plasma torus stares and scans. This paper describes the UVS investigation's science plans, instrument details, concept of operations, and data formats in the context of the JUICE mission's habitability and Jupiter system goals.

astro-ph.EP↗
arXiv2023

Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer

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 $μ$m), 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.

astro-ph.EP↗
arXiv2023

Probing Ganymede's atmosphere with HST Ly$α$ images in transit of Jupiter

We report results from far-ultraviolet observations by the Hubble Space Telescope of Jupiter's largest moon Ganymede transiting across the planet's dayside hemisphere. {Within} a targeted campaign on 9 September 2021 two exposures were taken during one transit passage to probe for attenuation of Jupiter's hydrogen Lyman-$α$ dayglow above the moon limb. The background dayglow is slightly attenuated over an extended region around Ganymede, with stronger attenuation in the second exposure when Ganymede was near the planet's center. In the first exposure when the moon was closer to Jupiter's limb, the effects from the Ganymede corona are hardly detectable, likely because the Jovian Lyman-$α$ dayglow is spectrally broader and less intense at this viewing geometry. The obtained vertical H column densities of around $(1-2)\times 10^{12}$~cm$^{-2}$ are consistent with previous results. Constraining angular variability around Ganymede's disk, we derive an upper limit on a local H$_2$O column density of $(2-3)\times 10^{16}$~cm$^{-2}$, such as could arise from outgassing plumes in regions near the observed moon limb.

astro-ph.EP↗
arXiv2021

A sublimated water atmosphere on Ganymede detected from Hubble Space Telescope observations

Ganymede's atmosphere is produced by charged particle sputtering and sublimation of its icy surface. Previous far-ultraviolet observations of the O{\small I\,}1356-Å and O{\small I\,}1304-Å oxygen emissions were used to infer sputtered molecular oxygen (O$_2$) as an atmospheric constituent, but an expected sublimated water (H$_2$O) component remained undetected. Here we present an analysis of high-sensitivity spectra and spectral images acquired by the Hubble Space Telescope revealing H$_2$O in Ganymede's atmosphere. The relative intensity of the oxygen emissions requires contributions from dissociative excitation of water vapor, indicating that H$_2$O is more abundant than O$_2$ around the sub-solar point. Away from the sub-solar region, the emissions are consistent with a pure O$_2$ atmosphere. Eclipse observations constrain atomic oxygen to be at least two orders of magnitude less abundant than these other species. The higher H$_2$O/O$_2$ ratio above the warmer trailing hemisphere compared to the colder leading hemisphere, the spatial concentration to the sub-solar region, and the estimated abundance of $\sim$10$^{15}$ H$_2$O/cm$^{2}$ are consistent with sublimation of the icy surface as source.

astro-ph.EP↗