Galileo Archives

Locations (yellow circles) of ROIs that include paterae, potential flows, and cryovolcanic candidate regions (K. Stephan et al. 2021a) on top of the global geological map of Ganymede from G. C. Collins et al. (2013). Mercator projection. -- The Planetary Science Journal

Astrogeology, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Ganymede, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Missions & Hardware, Status Report

Potential Cryovolcanic Regions on Ganymede: A Priority Target for JUICE

by Keith CowingJune 7, 2026June 26, 2026

One of the Jupiter Icy Moons Explorer (JUICE) mission goals of the European Space Agency, launched in 2023 April, is the detailed characterization of Ganymede, Jupiter’s largest moon and a […]

Comparison of (left) absolute and (right) normalized mineral and artificial reflectance spectra with the photosynthetic red edge. Spectra on the right were vectornormalized here to facilitate visualization of spectral features rather than overall reflectance. All spectra were also subjected to Gaussian smoothing with standard deviation 3. (a) sulfide mineral spectra from Table 1 (database source: stibnite, ECOSTRESS | chalcopyrite, ECOSTRESS | cinnabar, USGS | realgar, ECOSTRESS) alongside the green leaf spectrum used to model the VRE/PRE; (b) silicate mineral spectra from Table 1 (database source: lazurite, USGS | sodalite, ECOSTRESS | zircon, ECOSTRESS | nontronite, ECOSTRESS) -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

Mineral False Positives in the Search for Exoplanet Surface Biosignatures

by Keith CowingMay 13, 2026May 13, 2026

In the search for life in the cosmos, biopigments on exoplanet surfaces are a critical target.

Time-resolved IR spectra from electron irradiation of CaCO3 at 50, 100, and 120 K under two electron fluxes, normalized to the preirradiation CaCO3 baseline and truncated to the 4.2–4.3 μm region to highlight the CO2 ν3 band. Vertical dashed lines mark the central wavelengths of the CO2 doublet, determined from double Gaussian fits to the continuum-removed spectra (gray). CO2 absorptions appear upon irradiation and gradually saturate. The strongest absorptions occur at 50 K under high flux. At higher temperatures, the absorptions are weaker, but radiolytic CO2 production is still apparent. -- astro-ph.EP

Astrochemistry, Astrogeology, Europa, Icy Worlds, Imaging & Spectroscopy, Status Report

Formation And Trapping Of CO2 From Cryogenic Irradiation Of Carbonate

by Keith CowingMay 2, 2026May 2, 2026

The detection of CO2 on the Jovian satellite Europa by Galileo NIMS and recent mapping of the leading side by JWST has revealed that it is most concentrated in geologically […]

Bond albedo (a) and thermal inertia (b) maps derived from PPR measurements in this study. Background is the USGS Europa Voyager Galileo SSI Global Mosaic of Europa (Becker et al. 2010). -- astro-ph.EP

Analog Studies, Arctic / Antarctic / Alpine, Europa, Icy Worlds, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Status Report, Water/Hycean Worlds & Oceanography

Thermophysical Properties of Europa’s Surface Constrained by Galileo Photopolarimeter-Radiometer Temperature Measurements

by Keith CowingApril 18, 2026April 18, 2026

Thermal measurements constrain the physical properties of icy satellite surfaces, including grain size, porosity, and regolith structure. On Europa, analyses of the Galileo Photopolarimeter-Radiometer (PPR) dataset revealed thermal inertia heterogeneities, […]

In this composite image, red pixels mark locations on Europa’s surface where ammonia-bearing compounds were detected; purple indicates no such detection. Captured by NASA’s Galileo mission in 1997, the data is overlaid on a black-and-white mosaic that zooms in on a portion of the moon’s surface. NASA/JPL-Caltech

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Europa, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Press Release, Water/Hycean Worlds & Oceanography

NASA’s Galileo Mission Points to Ammonia at Europa, Recent Study Shows

by Keith CowingJanuary 29, 2026January 29, 2026

New analysis of decades-old data has turned up a significant result: the first discovery of ammonia-bearing compounds on the surface of Jupiter’s moon Europa. Ammonia is a nitrogen-bearing molecule, and […]

The 0.6-GHz data are much brighter due to reflected synchrotron emission and are, therefore, shown with a different colour scale. The terminator was at approximately 10° W longitude, with the right-hand side in sunlight for these maps. The approximate sounding depth (50% contribution for pure, solid ice) is shown in the lower right of each map, and a typical beam size is shown in the lower left of each map. -- Nature

Analog Studies, Astrogeology, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Europa, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report

Europa’s Ice Thickness And Subsurface Structure Characterized By The Juno Microwave Radiometer

by Keith CowingJanuary 5, 2026January 2, 2026

Jupiter’s moon Europa is thought to harbour a saltwater ocean beneath a variously disrupted ice shell, and it is, thus, one of the highest priority astrobiology targets in the Solar […]

A composite view of Europa’s spider-like Manannán Crater (right), taken by NASA’s Galileo spacecraft in May 1998. Credit: NASA/JPL/University of Arizona

Analog Studies, Arctic / Antarctic / Alpine, Astrogeology, Biosignatures & Paleobiology, Caves, Craters, Mountains, Subsurface, Lava Tubes, Europa, Exploration Gear & Tech, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Impact events, Mapping, Geodesy, Cartography, Bathymetry, Mars, Missions & Hardware, Origin & Evolution of Life, Polar / Alpine Expeditions, Press Release, Water/Hycean Worlds & Oceanography

Europa’s Spider-like Features And The Potential For Life

by Keith CowingDecember 5, 2025December 5, 2025

From Europa to other icy moons, scientists are studying how surface features form and what they might reveal about the potential for life.

Astrogeology, Biogeochemical Cycles & Geobiology, Callisto, Ganymede, Icy Worlds, Mapping, Geodesy, Cartography, Bathymetry, Press Release

Conditions For Accretion Favoring An Unmelted Callisto And A Differentiated Ganymede

by Keith CowingMay 13, 2025May 13, 2025

Analysis of Callisto’s moments of inertia, derived from Galileo’s gravity data, suggests that its structure is not fully differentiated.

Net yield of fluorescence photons per unit 248.6 nm laser energy per concentration (ppb) on Europa, given a radiolytic constant of 0.034 MGy−1 , at three exposure times to degradation mechanisms: (a) 10 years, (b) 20 years, and (c) 50 years. # denotes the total number of emitted fluorescence photons.-- astro-ph.EP

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Europa, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Radiation, Status Report, Water/Hycean Worlds & Oceanography

Fluorescent Biomolecules Detectable in Near-Surface Ice on Europa

by Keith CowingMarch 11, 2025April 29, 2025

Europa, Jupiter’s second Galilean moon, is believed to host a subsurface ocean in contact with a rocky mantle, where hydrothermal activity may drive the synthesis of organic molecules.

Callisto’s crater-covered surface may be hiding a liquid water ocean. Credit: NASA/JPL-Caltech/Kevin M. Gill, CC BY 2.0 Source: AGU Advances

Astrogeology, Biosignatures & Paleobiology, Callisto, Icy Worlds, Jupiter, Press Release, Water/Hycean Worlds & Oceanography

Callisto Is Very Likely an Ocean World

by Keith CowingFebruary 21, 2025February 21, 2025

More pocked with craters than any other object in our solar system, Jupiter’s outermost and second-biggest Galilean moon, Callisto, appears geologically unremarkable. In the 1990s, however, NASA’s Galileo spacecraft captured […]