- 4218 -
GANYMEDE - Jupiter’s largest satellite - The
”Juno mission” continues to orbit Jupiter, gathering data on its atmosphere,
composition, gravitational field, magnetic field, and radiation environment.
This data is helping scientists to learn more about the planet’s formation,
internal structure, mass distribution, and what is driving its powerful winds.
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--------------------- 4218 - GANYMEDE - Jupiter’s largest satellite
- The ”Juno mission”spacecraft performs flybys of Jupiter’s largest
satellites (the Galilean Moons), acquiring stunning images and vital data on
their surfaces. These include optical and thermal images of Io’s many active
volcanoes, Europa’s icy terrain, and infrared images of Ganymede.
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- During its last
flyby of Ganymede (June 7th, 2021), Juno collected infrared images and spectra
on the moon’s surface using its “Jovian InfraRed Auroral Mapper” (JIRAM)
instrument. This data revealed the
presence of salt minerals and organic molecules on the icy moon’s surface.
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- The findings could
help scientists better understand the origin of Ganymede, the composition of
its interior ocean, and the way material is exchanged between the surface and
interior. It could help scientists determine if life exists deep inside
Ganymede’s ocean.
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- Since the Voyager
probes buzzed through the system in 1979, the Galilean Moons (Io, Europa,
Ganymede, and Callisto) have been of great interest to scientists. Ganymede,
the largest of the Galileans (and even larger than the planet Mercury), has
attracted much attention because of its interior ocean, which is believed to
house more water than all of Earth’s oceans combined.
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- Ganymede is the
only satellite in the Solar System to have a magnetic field, which is believed
to be due to a molten outer core counter-rotating relative to the moon itself
(similar to Earth).
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- Due to its
composition and structure, a rocky and metallic core surrounded by vast ice
sheets and a liquid water ocean, scientists also speculate that there could be
hydrothermal activity at the core-mantle boundary. This may provide the
necessary chemical ingredients and energy to support life, similar to how
hydrothermal vents are thought to have given rise to Earth’s earliest life
forms. Because Ganymede’s surface crust shows signs of resurfacing events, scientists
have proposed that possible indications of life (“biosignatures”) might exist
on the surface.
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- Previous
spectroscopic observations by NASA’s Galileo spacecraft, the Hubble Space
Telescope, and the European Southern Observatory’s Very Large Telescope (VLT)
in Chile have all hinted at the presence of salts, magnesium sulfate (MgSO4)
and possibly sodium sulfate (Na2SO4) and organic molecules on its surface.
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- On June 7th, 2021,
Juno flew over Ganymede at a minimum altitude of 650 miles and collected data
with its JIRAM instrument to determine
if there are any potential biosignatures to be found on the surface.
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- The JIRAM was
designed to capture the infrared light from deep inside Jupiter and probe the
layered atmosphere down depths of 30 to 45 miles below the cloud tops. The
instrument has also been used to offer insights into the terrain of the
Galilean moons, providing data on the surface terrain and the composition of
the icy crust which consists mainly of frozen water and volatiles like carbon
dioxide, sulfur dioxide, hydrogen sulfate, and organic molecules.
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- During the July
2021 flyby, the JIRAM instrument obtained infrared spectra of unprecedented
spatial resolution, more than 0.62 miles per pixel. As a result, the research
team was able to detect and analyze the unique spectral features of mineral
salts, including hydrated sodium chloride (NaCl), ammonium chloride (NH2Cl),
and sodium bicarbonate (NaHCO3).
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- They also noted
the possibility of “aliphatic aldehydes”, the type of structural units
typically found in biologically active natural products. Each of these
compounds has different implications.
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- The presence of
ammoniated salts suggests that Ganymede may have accumulated materials cold
enough to condense ammonia during its formation. The carbonate salts could be remnants of
carbon dioxide-rich ices.
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- Previous modeling
of Ganymede’s magnetic field, the moon’s equatorial region (up to 40 °latitude)
is shielded from energetic electrons and heavy ion bombardment from Jupiter’s
powerful magnetic field. These particle fluxes are well known to impact salts
and organics negatively. During its June 2021 flyby, the JIRAM instrument
covered a narrow range of latitudes (10 °N to 30 °N) and a broader range of
longitudes (-35 °E to 40 °E) on the moon’s Jupiter-facing side.
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- They found the
greatest abundance of salts and organics in the dark and bright terrains at
latitudes protected by the magnetic field.
This suggests we are seeing the remnants of a deep ocean brine that
reached the surface of this frozen world.
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- The investigation
of the surface of Europa and Ganymede is to find indications of life in their
interiors. This will be evident from chemical markers that were brought to the
surface through resurfacing events and plume activity, both of which are common
on these Galilean Moons.
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- NASA hopes to send
another mission, the “Europa Lander”, to the surface to examine plume activity
and look for biosignatures more closely. This research also previews what other
missions might find in the near future, which will be sent to explore some of
Saturn’s largest moons.
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- These include
Titan, Enceladus, Dione, and Mimas, all of which are believed to be “Ocean
Worlds” that might also harbor life. If any or all of these missions uncover
evidence of biosignatures on these moons, it will confirm that life exists well
beyond Earth and will forever alter our concept of our place in it.
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November 8, 2023
GANYMEDE - Jupiter’s largest satellite 4218
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Monday, November 13, 2023 ---------------------------------
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