(ORDO NEWS) — Jupiter is well known for its spectacular auroras, thanks in no small part to the Juno orbiter and recent images taken by the James Webb Space Telescope (JWST).
As on Earth, these dazzling phenomena result from the interaction of charged solar particles with Jupiter’s magnetic field and atmosphere.
Over the years, astronomers have also detected faint auroras in the atmospheres of Jupiter’s largest moons (also known as the “Galilean moons”).
They are also the result of an interaction, in this case, between Jupiter’s magnetic field and particles emanating from the atmospheres of the moons.
Detecting these faint auroras has always been a challenge due to sunlight reflecting off the surface of the moons. completely washes away their light signatures.
In a series of recent papers, a team led by Boston University and Caltech (supported by NASA) observed the Galilean moons as they passed in Jupiter’s shadow.
These observations showed that Io, Europa, Ganymede, and Callisto are experiencing oxygen auroras in their atmospheres.
What’s more, these auroras are deep red and nearly 15 times brighter than the usual green patterns we see on Earth.
The research team included astronomers from the Center for Space Physics (CSP) at Boston University, the Department of Geological and Planetary Sciences (GPS) at the California Institute of Technology, the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Earth and Planetary Sciences at the University of California at Berkeley, Large Binocular Telescope Observatory (LBT), Southwestern Research Institute (SwRI), Institute for Planetary Science (PSI), Leibniz Institute for Astrophysics Potsdam (AIP), and NASA Goddard Space Flight Center.
The team’s observations combined data from the Keck Observatory’s 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 as they entered Jupiter’s shadow to avoid interference from sunlight reflected off their surfaces.
These data provided valuable information about the composition of the atmospheres of satellites, which, as expected, include gaseous oxygen.
Katherine de Kleer, professor at Caltech and lead author of one of the two papers, explained in a press release from the Keck Observatory:
“These observations are difficult because in the shadow of Jupiter, the moons are almost invisible.
The only evidence for this is the light emitted by their faint auroras. that we even pointed the telescope to the right place.
The brightness of the different colors of the aurora tells us what the atmospheres of these moons are likely to be made of.
We found that molecular oxygen, like what we breathe here on Earth, is probably the main constituent of the icy lunar atmosphere.”
All four of the Galilean satellites showed the same oxygen auroras, similar to what we see in the northern and southern lights (Northern and Southern Lights) here on Earth.
In the case of Europa, Ganymede, and Callisto, the oxygen content in their atmospheres is due to photolysis, a process in which water ice is sublimated and split by solar radiation into hydrogen gas and oxygen.
In Io’s case, oxygen comes from sulfur dioxide (spewed from the many volcanoes that dot its surface) interacting with solar radiation to form sulfur monoxide and elemental oxygen.
But due to their much thinner atmosphere, this oxygen glows in deep red and (for Europa and Ganymede) in infrared wavelengths, the latter indistinguishable to the human eye.
Due to Io’s volcanic activity, salts such as sodium chloride and potassium chloride are also present in the atmosphere, where they are also destroyed by solar radiation.
This causes the auroras on Io to emit a yellow-orange glow (caused by sodium) and glow in the infrared (caused by potassium).
Astronomers have observed this infrared glow for the first time in the atmospheres of these moons.
What’s more, the new measurements also revealed minimal evidence of water vapor, which was previously thought to be a component of the atmospheres of Europa, Ganymede and Callisto.
Theoretically, under all three satellites there are internal oceans. their icy surfaces, and there is even some preliminary evidence that the water vapor in Europa’s atmosphere could be the result of plume activity.
These plumes are thought to be connected to the moon‘s interior ocean or liquid reservoirs within its icy shell.
The observations also showed how Jupiter’s tilted magnetic field causes the brightness of the auroras to change as the gas giant rotates.
The tilt of this field by about 10° from Jupiter’s axis of rotation compared to the Earth’s 11° tilt means that the satellites will experience more interaction during certain periods of their orbit.
Finally, they also noted how the atmosphere reacted quickly to changes in temperature caused by the transition from being exposed to sunlight to being in Jupiter’s shadow.
Says Carl Schmidt, professor of astronomy at Boston University and lead author of the second paper:
“Sodium Io becomes very weak within 15 minutes of re-entry.
The shadow of Jupiter, but recovery after exposure to sunlight takes several hours.
These new features are very useful for understanding the chemistry of Io’s atmosphere.
Jupiter’s eclipses are a natural experiment to learn how sunlight affects its atmosphere.”
These latest observations have added excitement to an already very exciting area of research.
In the coming years, space agencies will send more robotic explorers to Europa and Ganymede – NASA’s Europa Clipper and ESA‘s JUpiter ICy Moon Explorer (JUICE).
These missions will conduct several flybys of these moons, collect data on the composition of their atmospheres and surfaces, and try to detect signs of possible life in their interiors (“biosignatures”).
Seeing these bright red auroras up close will be simply amazing!
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