arXiv subjects

Alyssa R. Rhoden

Publications and source records attributed to Alyssa R. Rhoden.

5 recordsLinked to original sources

arXiv2026

Active moons in our Solar System and beyond -- Io, Europa, Enceladus, Triton, and exomoons

The outgassing signatures of Io, Europa, Enceladus, Triton, and Io-like exomoons are the focus of this review chapter. The rocky volcanic world of Io is unique in our Solar System, with plumes reaching to hundreds of kilometres in altitude. Io-like exomoons could leave signatures strong enough to be detected with ground-based telescopes. The icy moons Europa and Enceladus, with their subsurface oceans, are currently the best candidates for life. Triton is different in many ways and raises unexplored questions. Our knowledge of these active moons is derived from space- and ground-based observations. To understand their origin, we discuss moon formation in general, before examining evidence and signatures of plumes on these moons. Given the accessibility of subsurface oceanic material through the occurrence of plumes, we expand on possibilities to investigate biosignatures.

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arXiv2024

Candidate Distant Trans-Neptunian Objects Detected by the New Horizons Subaru TNO Survey

We report the detection of 239 trans-Neptunian Objects discovered through the on-going New Horizons survey for distant minor bodies being performed with the Hyper Suprime-Cam mosaic imager on the Subaru Telescope. These objects were discovered in images acquired with either the r2 or the recently commissioned EB-gri filter using shift and stack routines. Due to the extremely high stellar density of the search region down stream of the spacecraft, new machine learning techniques had to be developed to manage the extremely high false positive rate of bogus candidates produced from the shift and stack routines. We report discoveries as faint as r2$\sim26.5$. We highlight an overabundance of objects found at heliocentric distances $R\gtrsim70$~au compared to expectations from modelling of the known outer Solar System. If confirmed, these objects betray the presence of a heretofore unrecognized abundance of distant objects that can help explain a number of other observations that otherwise remain at odds with the known Kuiper Belt, including detections of serendipitous stellar occultations, and recent results from the Student Dust Counter on-board the New Horizons spacecraft.

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arXiv2020

Formation, Composition, and History of the Pluto System: A Post-New-Horizons Synthesis

The Pluto-Charon system provides a broad variety of constraints on planetary formation, composition, chemistry, and evolution. Pluto was the first body to be discovered in what is now known as the Kuiper belt, its orbit ultimately becoming a major clue that the giant planets underwent substantial orbital migration early in Solar System history. This migration has been linked to an early instability in the orbits of the giant planets and the formation of the Kuiper belt itself, from an ancestral trans-Neptunian planetesimal disk that included Pluto. Pluto-Charon is emblematic of what are now recognized as small or dwarf planets. Far from being a cold, dead, battered icy relic, Pluto displays evidence of a complex geological history, with ongoing processes including tectonism, cryovolcanism, solid-state convection, glacial flow, atmospheric circulation, surface-atmosphere volatile exchange, aeolian processes, and atmospheric photochemistry, microphysics, and haze formation. Despite Pluto's relatively modest scale, the combination of original accretional heat, long-term internal radiogenic heat release, and external solar forcing, when combined with sufficiently volatile (and thus mobile) materials, yields an active world. Pluto may have inherited a large organic mass fraction during accretion, which may responsible, in part, for its surface and atmospheric volatiles. Charon, Pluto's major moon, displays evidence of extensive early tectonism and cryovolcanism. Dwarf planets are thus truly planetary in terms of satellite systems and geological and atmospheric complexity (if not ongoing activity). What they may lack in mass is made up in number, and the majority of the Solar System's dwarf planets remain undiscovered.

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arXiv2017

Vital Signs: Seismology of ocean worlds

Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could probe their transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes, and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with the Moon, that detectable seismic activity on tidally flexed ocean worlds should occur frequently. Their ices fracture more easily than rocks, and dissipate more tidal energy than the <1 GW of the Moon and Mars. Icy ocean worlds also should create less thermal noise for a due to their greater distance and consequently smaller diurnal temperature variations. They also lack substantial atmospheres (except in the case of Titan) that would create additional noise. Thus, seismic experiments could be less complex and less susceptible to noise than prior or planned planetary seismology investigations of the Moon or Mars.

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arXiv2015

Linking Europa's plume activity to tides, tectonics, and liquid water

Much of the geologic activity preserved on Europa's icy surface has been attributed to tidal deformation, mainly due to Europa's eccentric orbit. Although the surface is geologically young (30 - 80 Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa's south pole suggests that it may be geologically active. Initial observations indicated that Europa's plume eruptions are time-variable and may be linked to its tidal cycle. Saturn's moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa's tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on Europa and Enceladus.

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