Geology Reports⌕ Search
Home/Archive/USGS

USGS · 70017746

O2 on ganymede: Spectral characteristics and plasma formation mechanisms

W. M. Calvin·R.E. Johnson·J.R. Spencer
View original source ↗Export metadata ↓

Abstract

Weak absorption features in the visible reflectance spectrum of Jupiter's satellite Ganymede have been correlated to those observed in the spectrum of molecular oxygen. We examine the spectral characteristics of these absorption features in all phases of O 2 and conclude that the molecular oxygen is most likely present at densities similar to the liquid or solid γ-phase. The contribution of O 2 to spectral features observed on Ganymede in the near-infrared wavelength region affects the previous estimates of photon pathlength in ice. The concentration of the visible absorption features on the trailing hemisphere of Ganymede suggests an origin due to bombardment by magnetospheric ions. We derive an approximate O 2 formation rate from this mechanism and consider the state of O 2 within the surface.

Explore related subjects

Geophysical Research LettersArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

W. M. Calvin, R.E. Johnson, J.R. Spencer. 1996-03-15. O2 on ganymede: Spectral characteristics and plasma formation mechanisms. https://doi.org/10.1029/96gl00450

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Evolution of summit magma pressure during the 2018 caldera collapse at Kılauea volcano

We utilized geodetic data from the 16 May to 4 August 2018 caldera collapse sequence to refine the geometries and pressure evolution of two summit reservoirs at Kīlauea volcano: the shallower Halema‘uma‘u (HMM) and deeper South Caldera (SC) reservoirs. We modeled magma reservoirs as pressurized spheroidal cavities and constrained reservoir geometries with Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar displacements. Inverting high-rate GPS and borehole tilt time series recovered time-dependent reservoir pressure changes and caldera ring fault shear stress. During the collapse sequence, the HMM reservoir accommodated episodic, co-collapse pressure increases of 1.9 MPa (median) and a net 5.8 MPa (median) decrease. Simultaneously, the SC reservoir underwent monotonic depressurization of 6.7 MPa (median). Negligible co-collapse pressure changes in the SC reservoir imply it was not exclusively supplying magma to the eruption vent. These results provide a coherent view of magma reservoir pressure evolution during the 2018 eruption.

Hawaii↗
USGS2026

EMIT reveals elevated calcite signatures in shorelines of Lake Powell and Lake Mead exposed by drought and Colorado River management

Nearly half of Earth’s seasonal freshwater storage variability occurs in human-managed reservoirs, resulting in large areas of reservoir-bed that are episodically inundated or subaerially exposed. Here we use hyperspectral data from NASA’s Earth Surface Mineral Dust Source Investigation (EMIT) mission to map calcite mineral assemblages across exposed surfaces in two large U.S. reservoirs, Lake Mead and Lake Powell. Results show distinct patterns in the occurrence of carbonate, clay, and mica minerals. Reservoir-deposited sediments exhibited significantly higher calcite proportions than adjacent, lithologically similar, non-inundated terrestrial surfaces. These differences likely reflect hydrologically-driven calcite precipitation, wherein warm, clear, productive reservoir waters drive calcium carbonate out of solution. We also detect reductions in calcite proportions in areas of the shoreline disturbed by human recreation. EMIT's imaging capabilities enable rapid, high-resolution mineralogical inventories across vast areas where field sampling is infeasible. We find EMIT is a scalable tool for monitoring geochemical changes associated with large water level fluctuations.

Arizona, Nevada, Utah↗
USGS2026

First application of a coastal-dune model (AeoLiS) to simulate fluvial-aeolian morphodynamics

Quantifying aeolian processes is important to decision-making in river management and for optimizing strategies for ecosystem conservation, natural resource management, and recreation. We applied the AeoLiS aeolian transport model, originally developed for coastal environments, to a dryland river corridor to evaluate its ability to simulate sediment dynamics in a fluvial-aeolian system. The model reproduced spatial and temporal patterns of geomorphic change at a Grand Canyon sandbar, including aeolian dune formation, observed in field data. The model effectively captured trends in observed sediment movement in the spring and summer months. Thus, despite assuming a single grain-size, static vegetation, and not directly accounting for variable sediment supply from fluvial sources, the model performs well at capturing aeolian processes in a complex fluvial-aeolian system. AeoLiS demonstrates strong potential for dryland river applications and management, due to its flexibility and compatibility with coupled modeling frameworks.

Arizona↗