The research team consisted of astronomers from the Center for Space Physics (CSP) at Boston University, the Division of Geological and Planetary Sciences (GPS) at Caltech, the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Earth and Planetary Science at the UC Berkeley, Large Binocular Telescope Observatory (LBT), the Southwest Research Institute (SwRI), the Planetary Science Institute (PSI), the Leibniz-Institute for Astrophysics Potsdam (AIP), and NASAs Goddard Space Flight Center. The two research studies, entitled “The Optical Aurorae of Europa, Ganymede, and Callisto” and “Ios Optical Aurorae in Jupiters Shadow,” appeared on February 16th in the Planetary Science Journal.
Over the years, astronomers have also detected faint aurorae in the environments of Jupiters largest moons (aka. These are likewise the outcome of interaction, in this case, between Jupiters magnetic field and particles emanating from the moons environments.
Identifying these faint aurorae has actually always been a challenge due to the fact that of sunlight reflected from the moons surfaces totally cleans out their light signatures. In a series of recent papers, a team led by the University of Boston and Caltech (with assistance from NASA) observed the Galilean Moons as they passed into Jupiters shadow.
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Galilean Family Portrait. Credit: NASA/JPL
The teams observations integrated information from the Keck Observatorys High-Resolution Echelle Spectrometer (HIRES) with high-resolution spectra from the Large Binocular Telescope (LBT) and the Apache Point Observatory (APO). These observations were timed to see Io, Europa, Ganymede, and Callisto when they got in Jupiters shadow to prevent disturbance from sunlight reflected off their surfaces. This data revealed important information concerning the composition of the moons atmospheres, that included oxygen gas (as expected).
Katherine de Kleer, a Caltech teacher and the lead author of one of 2 documents, described in a Keck Observatory press release:
” These observations are difficult due to the fact that in Jupiters shadow the moons are nearly unnoticeable. The light discharged by their faint aurorae is the only verification that weve even pointed the telescope at the best place. The brightness of the different colors of aurora inform us what these moons atmospheres are most likely comprised of. We find that molecular oxygen, much like what we breathe here on Earth, is most likely the main constituent of the icy moon atmospheres.”
All four Galilean Moons showed the exact same oxygen aurorae, similar to what we see with the Aurora Borealis and Australis (the Northern and Southern Lights) here in the world. In the case of Europa, Ganymede, and Callisto, the oxygen material of their atmospheres is because of photolysis, a process where water ice is and sublimates broken down by solar radiation into its hydrogen gas and oxygen. In Ios case, the oxygen is caused by sulfur dioxide (spewed from the numerous volcanoes that dot its surface) interacting with solar radiation to form sulfur monoxide and elemental oxygen.
Since of their much thinner atmospheres, this oxygen glows in the deep red and (for Europa and Ganymede) in infrared wavelengths– the latter being undetected to the human eye. Because of Ios volcanic activity, salts like salt chloride and potassium chloride are also present in the environment, where they are also broken down by solar radiation. This leads to aurorae on Io releasing a yellow-orange radiance (triggered by salt) and radiant in the infrared (triggered by potassium).
Artists depiction of oxygen aurora on Jupiters moon Ganymede, the biggest moon in the planetary system, as observed by the twin Keck Observatory telescopes. Credit: Julie Inglis
All 3 moons are thought to have interior oceans underneath their icy surfaces, and theres even some tentative proof that water vapor in Europas atmosphere might result from plume activity. These plumes are thought to be connected to the moons interior ocean or liquid reservoirs within its icy shell.
The observations also showed how Jupiters slanted magnetic field causes aurorae to differ in brightness as the gas giant turns. The tilt of this field, approximately 10 ° from Jupiters axis of rotation compared to Earths 11 ° tilt, means that the moons will experience greater interaction at particular times of their orbit. Finally, they likewise kept in mind how the atmospheres responded rapidly to temperature level modifications triggered by the transition in between direct exposure to sunlight and passing within Jupiters shadow. Said Carl Schmidt, a teacher of astronomy at Boston University and the lead author of the 2nd paper:
” Ios salt ends up being very faint within 15 minutes of getting in Jupiters shadow, however it takes numerous hours to recuperate after it emerges into sunshine. These brand-new qualities are really insightful for comprehending Ios climatic chemistry. Its neat that eclipses by Jupiter provide a natural experiment to find out how sunshine impacts its environment.”
Over the years, astronomers have actually also found faint aurorae in the environments of Jupiters largest moons (aka. These are likewise the result of interaction, in this case, in between Jupiters magnetic field and particles emanating from the moons atmospheres.
” These observations are tricky due to the fact that in Jupiters shadow the moons are nearly invisible. They also noted how the environments reacted rapidly to temperature level modifications triggered by the shift between direct exposure to sunlight and passing within Jupiters shadow. In the coming years, area companies will send more robotic explorers to Europa and Ganymede– NASAs Europa Clipper and the ESAs JUpiter ICy moon Explorer (JUICE).
In the coming years, area firms will send out more robotic explorers to Europa and Ganymede– NASAs Europa Clipper and the ESAs JUpiter ICy moon Explorer (JUICE). These objectives will perform several flybys of these moons, collect information on the structures of their surfaces and environments, and effort to find indications of possible life in their interiors (” biosignatures”).
More Reading: Keck Observatory
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