Galileo Archives

Water ice on the surface of Europa is dissociated by radiolysis to form O2 and H2. These gases can migrate both inwards towards the subsurface ocean or escape the surface by thermal desorption or direct sputtering to form its atmosphere. The lighter H2 occupies a more extended region than heavier O2, which remains closer to the surface. A portion of the neutrals in the atmosphere are ionized and picked up by the magnetospheric plasma. Juno observes these PUIs, with the relative abundances driven by the various processes described here. The radiolysis dissociation inset was adapted from ref. 2. Particles shown are O2 (blue), H2 (pink) and H2+ (grey). -- NASA/Nature Astronomy

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Europa, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Jupiter, Press Release

Juno Measures The Rate Of Oxygen Production At Europa

by Keith CowingMarch 4, 2024March 4, 2024

Scientists with NASA’s Juno mission to Jupiter have calculated the rate of oxygen being produced at the Jovian moon Europa to be substantially less than most previous studies.

Color–color plot from the 1990 Galileo encounter with Earth showing brightness ratios in the RED/VIOLET and IR-6560/VIOLET SSI filters. The colorbar on the right indicates sxub-spacecraft west longitude, with important features marked along that colorbar. Larger values along either axis indicate redder colors. The overall color of Earth changes in a cyclical fashion as it rotates underneath the spacecraft. The strongest redward deviation occurs when the Sahara and Amazon rainforest were in view while the strongest blueward deviation occurs when the Pacific Ocean is in view. -- astro-ph.EP

Analog Studies, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Status Report, Water/Hycean Worlds & Oceanography

Exoplanet Analog Observations Of Earth From Galileo Mission Disk-integrated Photometry

by Keith CowingFebruary 6, 2024February 6, 2024

The Galileo spacecraft had distant encounters with Earth in 1990 and 1992. Limited Solid State Imager (SSI) data acquired during these encounters has been previously presented, but the majority of […]

(a) Time-Energy-Differential Number Flux (DNF) spectrogram of the JADE-E data recorded during Juno’s 12th perijove. (b) Magnetic projection of Juno’s position onto the orbital plane of the Galilean moons (green curves) and Juno’s M-Shell (red curves) calculated with JRM33+KK2005 (dashed lines) and JRM33+CON2020 (plain lines). Vertical blue lines at 09:15:42 and 09:20:46 highlight the magnetic flux tubes crossings of Europa and Io, respectively. Juno’s position and velocity with respect to Jupiter are indicated below the sub-panel (b). -- astro-ph.EP

Callisto, Europa, Ganymede, Io, Jupiter, Status Report

Influence Of The Jovian Current Sheet Models On The Mapping Of The UV Auroral Footprints Of Io, Europa, And Ganymede

by Keith CowingJanuary 19, 2024January 19, 2024

The in-situ characterization of moon-magnetosphere interactions at Jupiter and the mapping of moon auroral footpaths require accurate global models of the magnetospheric magnetic field.

Galileo imagery of Earth -- Carl Sagan et al / NASA /Nature

Biosignatures & Paleobiology, Habitable Zones, Imaging & Spectroscopy, Mapping, Geodesy, Cartography, Bathymetry, Missions & Hardware, Press Release, Water/Hycean Worlds & Oceanography

A Search For Life On Earth From The Galileo Spacecraft (Carl Sagan et al 1993)

by Keith CowingOctober 23, 2023October 23, 2023

In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part […]

Biosignatures & Paleobiology, Callisto, Europa, Ganymede, Gas Giants, Icy Worlds, Imaging & Spectroscopy, Io, Jupiter, Missions & Hardware, Status Report, Water/Hycean Worlds & Oceanography

Jupiter Science Enabled by ESA’s Jupiter Icy Moons Explorer

by Keith CowingMay 7, 2023April 14, 2024

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 […]

Astrogeology, Europa, Icy Worlds, Missions & Hardware, Press Release, Water/Hycean Worlds & Oceanography

Ocean Currents May Affect Rotation of Europa’s Icy Crust

by Keith CowingMarch 13, 2023March 13, 2023

Research reveals a new explanation for how the icy shell of Jupiter’s moon Europa rotates at a different rate than its interior. NASA’s Europa Clipper will take a closer look.

Astrochemistry, Europa, Icy Worlds, Imaging & Spectroscopy, Missions & Hardware, Press Release

Constraining Europa’s Subsolar Atmosphere With A Joint Analysis Of HST Spectral Images And Galileo Magnetic Field Data

by Keith CowingAugust 30, 2022September 4, 2022

We constrain Europa’s tenuous atmosphere on the subsolar hemisphere by combining two sets of observations: oxygen emissions at 1304 Å and 1356 Å from Hubble Space Telescope (HST) spectral images, […]

An artist’s depiction of our world when the Earthshine measurements were taken, enhanced to show the “red edge” from vegetation. A distant astronomer on another planet would see the spectral signatures of our oxygen atmosphere, water, and chlorophyll from land plants. [enlarge] Credit: John Walker’s “Earth Viewer,” Christine Lafon, (Harvard-Smithsonian Center for Astrophysics).

Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Imaging & Spectroscopy, Press Release, Water/Hycean Worlds & Oceanography

Astronomers Find Life On Earth

by Keith CowingOctober 30, 2002January 20, 2026

Now that the discovery of extrasolar planets, or planets around distant stars, has become relatively routine, scientists are now tackling the next step: finding life-bearing worlds. To do this, observers […]