- 3950 -
MOONS OF JUPITER
- and more. The Galilean moons of Jupiter: Io, Europa,
Ganymede, and Callisto.
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--------------------------- 3950
- MOONS OF
JUPITER - and ,more
- Enceladus
is geologically active, which was very surprising given how tiny it is. It is spewing jets of ice and water vapor
into space. It is giving us free samples of its interior. We can analyze the composition of the ocean
(and even look for life) without having to drill through the ice.
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- Saturn’s
sixth-largest moon, Enceladus, was discovered in 1789 by William Herschel, and
whose diameter is approximately the size of the State of Arizona. Enceladus possesses geysers that discharge
ice and water vapor from a series of fissures known as “tiger stripes”.
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- These
geysers were first observed by NASA’s Cassini spacecraft during its mission in
the 2000s, and Cassini even flew through them to test their composition,
finding water vapor, a variety of salts, methane, and carbon dioxide.
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- Io is the
innermost of the Galilean satellites of Jupiter. Discovered by Galileo Galilei in January of
1610, Io is the most geologically active of all of the moons of our Solar
System. A Laplace orbital resonance with Jupiter’s other moons Europa and
Ganymede results in tidal flexing and heating of Io’s interior, producing an
enormous amount of energy that powers over 400 volcanoes on Io’s surface.
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- Io’s
volcanic activity, which manifests as both lava flows and lava lakes in
caldera-like craters, and in explosive eruption plumes that shoot silicate ash,
dust, and sulfur-bearing gases hundreds of kilometers above the surface,
results in a world without any large impact craters. This indicates that Io has
the geologically youngest surface in the Solar System. Io serves as an example of potentially
active, volcanic lava planets discovered around other stars in our Galaxy.
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- Io, was
first visited by NASA’s Pioneer 10 and 11 in December 1973 and December 1974,
but only one image was taken by Pioneer 11 during the brief flyby.
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- It wasn’t
until Voyager 1 and 2 flew through the Jupiter system in 1979 that scientists
got their first real look at this mysterious moon, revealing a crater-less
surface and was the first planetary object other than Earth to be observed
exhibiting volcanic activity, which is due to the tidal heating between Io and
the much more massive Jupiter, along with Europa orbiting just beyond Io.
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- Proteus is
a small moon of Neptune. Compared to Neptune’s large active moon, Triton, it
seems reasonable to neglect battered little Proteus. But, Proteus is in the
same size range as Mimas and Enceladus (around Saturn), and Miranda (around
Uranus), which are much more round and brighter than Proteus.
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- Enceladus
is geologically active with very high heat flows and plumes at its South Pole.
And yet, Proteus is heavily cratered, with so many large craters that it
doesn’t even look spherical anymore.
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- Proteus is
Neptune’s second-largest moon, and was discovered by Voyager 2 in 1989 when the
spacecraft flew through the Neptune system. Despite its non-spherical shape,
Proteus shows no signs of current geologic activity, unlike Neptune’s much
larger moon, Triton, and is one of the darkest objects in the Solar System.
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- There is so
much that we still don’t know about Triton.
Very fundamental questions like whether or not it has an internal ocean,
whether or not the bizarre features on the surface are cryovolcanic and whether
or not the surface and the sub-surface ocean interact. What is the composition
of the bright south polar region? How are different ices distributed across the
surface?
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- Triton was
discovered by William Lassell in 1846. It is the largest of Neptune’s 13 moons,
and possibly the most intriguing, with its cantaloupe terrain and dark streaks
from geysers across its surface, which Voyager scientists determined to be
geysers when Voyager 2 flew past in 1989, Triton could possibly contain an
interior liquid ocean.
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- Despite the
very brief flyby, scientists learned a great deal about this small moon, whose
diameter is approximately one-half the width of the United States at 1,680
miles.
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- Europa is
the sixth-largest moon in the solar system.
Europa has evidence of an ocean of water below the moon’s icy surface.
Europa, therefore, may have the necessary ingredients for life: water, energy,
and complex molecules known as organics.
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- Like Io,
Jupiter’s second Galilean moon, Europa, was discovered by Galileo Galilei in
1610, and also exhibits a crater-less surface due to tidal heating, as well.
But instead of extreme volcanism, Europa harbors an interior ocean that is
estimated to contain more than twice the volume of all of Earth’s oceans
combined despite Europa being smaller than Earth’s Moon.
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- Europa was
first explored up close by Voyager 1 and 2 in 1979, which presented strong
evidence of an interior ocean beneath the Europa’s ice shell.
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- Titan is
particularly awesome. Titan’s
subsurface liquid water mantle makes it an Ocean World, like Europa, Ganymede,
and Enceladus. But at the same time Titan is one of just four places that we
know of in the entire universe that sport both a solid surface and a thick
atmosphere, along with Venus, Earth, and Mars.
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- Only Earth
and Titan have lakes and seas of surface liquid, and it’s just Earth and Titan
again that have extensive water in the vicinity of complex organic molecules.
All of these make Titan a logical choice for future exploration.
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- We are
sending the “Dragonfly relocatable lander” to Titan to investigate possibly
prebiotic chemistry, to ascertain its habitability, and to search for chemical
signatures of potential life there. Dragonfly launches in 2027 June and will
arrive at Titan after a 6.5-year space cruise, after which it will fly in
Titan’s air to more than 20 different landing sites as a nearly one-ton
octocopter. It arrives by 2034!
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- Saturn’s
largest moon, Titan, which is also the second largest moon in the Solar System,
was discovered by Christiaan Huygens in March 1655, and is the only moon to
possess a dense atmosphere comprised of a thick haze that cameras in the
visible spectrum cannot penetrate.
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- Titan was
first explored by NASA’s Pioneer 11 and later by Voyager 1 and 2, but none of
the spacecraft possessed the equipment to penetrate the thick atmosphere and
see the surface.
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- It wasn’t
until NASA’s Cassini mission with its radar and infrared instruments that
scientists were able to see the surface for the first time, revealing countless
lakes of liquid methane and ethane, making Titan the only known planetary body
other than Earth to have bodies of liquid on its surface.
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- During the
mission, Cassini deployed the “Huygens probe” that landed on Titan’s surface, becoming
the first spacecraft to land on a planetary body in the outer Solar System.
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- Ganymede
would be called a planet if it wasn’t a moon around Jupiter, he’s quick to
point out that Ganymede wouldn’t have stayed a planet if it didn’t form around Jupiter
in the first place.
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- Ganymede has
a highly geologically complex outer shell of water ice, showing both ancient
and relatively recent regions. Beneath that shell is an ocean of liquid water
up to 900 kilometers deep. More likely, instead of a single water ocean,
there’s a layer of high-pressure ice at the base of a somewhat thinner ocean.
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- It’s even
possible that there are interleaved layers of ocean and ice, forming an
onion-like interior beneath the icy exterior. And then, under all the ice and
water is a rocky planetary body about the same size of the Moon. And that rocky
body must surely be differentiated, just like the Moon, and Earth, Venus, Mars,
and Mercury, because the rocky interior of Ganymede has at its center a liquid
iron core, the movement of which generates a modern magnetic field.
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- That
magnetic field makes Ganymede one of only three rocky bodies in the Solar
System to generate a modern magnetic field, the other two being Earth and
Mercury.
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- Much like Io
and Europa, Jupiter’s third Galilean moon, Ganymede, was also discovered by
Galileo Galilei in 1610, and is the largest moon in the Solar System, even
bigger than the planet Mercury and the dwarf planet Pluto.
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- Ganymede
was first visited by NASA’s Pioneer 10 and then Pioneer 11, but received its
first up close study from Voyager 1 and 2 in 1979, with Voyager 1 imaging a
surface that had a combination of craters and smooth terrain, which contrasts
both Io and Europa’s respective surfaces.
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- The “Galileo
spacecraft” became the first spacecraft to orbit Jupiter and was able to
provide the most in-depth analyses of Ganymede, including the identification of
a magnetosphere and close images revealing a very diverse surface. The Hubble Space Telescope later provided
evidence that Ganymede harbors an interior ocean much like Europa.
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April 7, 2023 MOONS OF
JUPITER - and more 3950
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--- Monday, April 10, 2023 ---------------------------
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