Real Images Of What Nasa Discovered On Jupiter's Hellish moon Io
Something happened on January 1610. A smart guy, called Galileo Galilei, was pointing
his telescope at the sky. More precisely, he was trying to point it
towards Jupiter. He knew exactly how to do in order to observe
it: the day, the time, the setup. The only thing he didn't know was he was going
to discover something special. We are talking about the discovery of Jupiter's
moons. Just like an explorer finds new lands after
much navigating, Galileo found 4 objects orbiting around the giant gaseous planet. Today we
call them “Galileian moons”, and they are Io, Europa, Ganymede and Callisto.
To be fair, Jupiter has actually something like 80 moons orbiting around it, it is like
the King of the moons in our solar system. But the most known are for sure Io, Europa,
Ganymede and Callisto.
Just imagine it. It's 1610, and you point your telescope to the sky, and find the first
evidence of moons beside the Earth-moon, and they are orbiting around another planet.
What would you do if you were Galileo? Do you think you could believe your eyes?
I think I would have started to cry.
In this video, we are going to talk about Jupiter's moon Io, the probes who visited
it, and other amazing things such as the features of its atmosphere and volcanoes. Let's go!
Since Galileo's discovery, we understood a lot of things about Io.
We got to know it better, and now we think we have a very good vision of it.
First of all, Io was not Io before. It was just known as Jupiter I (Jupiter first)
or “the first satellite of Jupiter”. But then Io was adopted.
Do you know who gave the name to it? It was a famous astronomer, Simon Marius.
In 1614, he published his work Mundus Iovialis describing the planet Jupiter and its moons.
In his work, he claimes to have discovered the planet's four major moons a month before
Galileo. Because of Galileo's stature in the scientific
community, for nearly 300 years, Marius's reputation was tainted by Galileo accusations
of plagiarism. However, a jury in the Netherlands in 1903
examined the evidence extensively and ruled in favour of Marius's independent discoveries.
Regardless of priority, the mythological names by which these satellites are known today
(Io, Europa, Ganymede and Callisto) are those given them by Marius. He wrote:
Io, Europa, Ganimedes puer, atque Calisto lascivo nimium perplacuere Iovi
Which is the Latin for Io, Europa, the boy Ganymede, and Callisto
greatly pleased lustful Jupiter.
In Greek mythology, Io is the daughter of Inachus (the river god of Argus) and the Oceanid
Melia. As of today, we know that Io orbits Jupiter
at a distance of 421,700 km from Jupiter's centre and 350,000 km from its cloud tops.
It is the innermost of the Galilean satellites of Jupiter.
Including Jupiter's inner satellites, Io is the fifth moon out from Jupiter. It takes
Io about 42.5 hours to complete one orbit around Jupiter. Io orbits around Jupiter and
shows always the same face, as our moon does with the Earth. Surrounding Io (at a distance
of up to six Io radii from its surface) is a cloud of neutral sulfur, oxygen, sodium,
and potassium atoms. These particles originate in Io's upper atmosphere, and we will see
how.
However, for the next two and half centuries after Galileo's discovery, Io remained an
unresolved, 5th magnitude point of light in an astronomer's telescope, meaning that we
could not see its features at all because our technology was not that good yet.
In the 19th century, things changed. Technology in that years allowed astronomers to resolve
(that is, see as distinct objects) large scale surface features on Io.
Then, with the advent of spectroscopy, scientists found that Io's surface was devoid of water
ice. This seemed weird since it was the only Galilean
satellite to lack water. The same type of observations was also suggesting
that Io's surface is largely dominated by sodium salts and sulfur.
But things really got interesting when we decided to send spacecraft on their way to
Io. In doing this, we took photos. These pictures
are now stuck in our minds, and every time we see one of them, we could not believe that
those are pictures of the same moon that Galileo saw for the first time in January 1610.
The first-ever spacecraft to pass by Io were the Pioneer 10 and 11 probes.
It was a cold December 1973 here on Earth. With the help of a radio-tracking technology,
Pioneer helped us to estimate the moon's mass, which, along with the best available information
of its size, suggested the composition of mainly silicate rock rather than water ice.
But another interesting feature was the presence of a thin atmosphere and intense radiation
belts near Io's orbit. Here's the Pioneer 11 picture from that mission.
It is showed the north polar region of Io. This is the only Pioneer image, taken by Pioneer
11, of Io of any quality. The quality is not the best, but it shows some albedo features.
Close up images were also planned during pioneer 10's encounter, but those were unfortunately
lost because of the high radiation environment.
Then, in 1977, NASA decided to send two probes
to visit Pluto. Those were the Voyager probes. The journey would have been long, because
of the long distance to cover in order to reach it.
When the twin probes Voyager 1 and Voyager 2 passed by Io in 1979, their more advanced
imaging system allowed for far more detailed images. It was March 1979. Voyager 1 flew
past Io at a distance of about 20.000 km: veeeery close!
The precious images taken showed a multi-coloured landscape devoid of impact craters.
It was such a strange surface! The highest resolution images showed Io was a relatively
young object, with mountains taller than Mount Everest and features resembling volcanic lava
flows. Navigation engineer Linda A. Morabito noticed
a plume emanating from the surface in one of the images.
Further analysis showed nine such plumes scattered across the surface, and that was the final
evidence for volcanic activity on the moon. This was actually a confirmation for a theory
that has been proposed before the Voyager mission took place. Astriophysicyst Stan Peale
calculated that Io's interior must experience something called “Tidal Heating”. This
process on Io is caused by an orbital resonance with Europa and Ganymede.
Such heating is dependent on Io's distance from Jupiter, its orbital eccentricity, the
composition of its interior, and its physical state.
The tidal forces experienced by Io are about 20,000 times stronger than the tidal forces
Earth experiences due to the moon. The friction or tidal dissipation produced
in Io's interior due to this varying tidal pull, which, without the resonant orbit, would
have gone into circularizing Io's orbit instead, creates significant tidal heating within Io's
interior, melting a significant amount of Io's mantle and core.
The huge amount of energy produced is released in the form of volcanic activity, generating
the observed heat flow. Other moons in the Solar System are also tidally
heated, and they too may generate additional heat through the friction of subsurface magma
or water oceans. This ability to generate heat in a subsurface ocean increases the chance
of life on bodies like Europa. When Voyager two passed by Io in July 1979,
it took some pictures as well. When scientists compared images taken by the two spacecraft,
they noticed that several surface changes had occurred in the four mounts between the
encounters. This makes IO one of the most hellish moons
of our solar system!
Finally, in 1995, the Galileo spacecraft arrived at Jupiter.
Galileo mission was entirely dedicated to the study of Jupiter and its moons.
Ladies and gentlemen, prepare yourself because you are going to take a look at the most breathtaking
pictures we have of Io. Here they are.
Despite the lack of close-up imaging and mechanical problems that greatly restricted the amount
of data returned, several significant discoveries were made during Galileo's primary mission.
For example, we observed the major eruption at Pillan Patera volcano and confirmed that
volcanic eruptions are composed of silicate magmas with magnesium-rich compositions.
Another important revelation we had from Galileo mission was that Io doesn't own a magnetic
field.
But the game was not over! After some years, another interplanetary space
probe was launched by NASA. It lifts off on January 2006.
Its name was New Horizon, and it was the fastest man-made object ever launched from Earth.
New Horizon, again, was meant for Pluto. But of course...if you happen to pass near to
Jupiter, you won't miss your chance to take some beautiful pictures of it and its moons.
It made its closest approach on February 28, 2007.
The Jupiter flyby provided a gravity assist that increased New' Horizon's speed.
In doing this, we gained more data about the planet's atmosphere, moon and magnetosphere.
New Horizons also captured images of a volcano near Girru Patera in the early stages
of an eruption, and several volcanic eruptions that have occurred since Galileo.
Here is a Jupiter and Io montage took by New Horizon.
Instead here are shown changes on Io's surface.
And we also have a plume fall!
The last important spacecraft that gifted our eyes with beautiful pictures of Jupiter
and its moons was the Juno spacecraft. It was primarily aimed at improving our understanding
of Jupiter's interior, aurorae and polar atmosphere, and in order to do so, it has a highly inclined
orbit that helped better characterize Jupiter's polar regions.
Juno was launched in 2011 and reached its orbit around Jupiter in 2016.
During several orbits, it has observed IO from a distance using Juno-Cam, a wide-angle,
visible-light camera, to look for volcanic plumes.
Here's a visible-domain image of Io from JunoCam, showing a volcanic plume illuminated beyond
the terminator of Io. The image was taken on 21 December 2018, during the 17th flyby
of Jupiter by Juno.
While the new Juno images were taken a lot farther away from Io than the previous ones,
there is still a lot of information that scientists can obtain from them. For instance, they can
provide new insights into how Jupiter interacts with its five moons – causing phenomena
such as Io’s volcanic activity or the freezing of the moon’s atmosphere during an eclipse.
Even though Io is very small, its gravitational interaction with Jupiter drives the moon’s
volcanoes, which produce huge umbrella-like plumes of sulfur dioxide gas and extensive
lava fields. That “stretching” causes friction and intense heat in Io’s interior,
sparking massive eruptions across its surface.
Juno was the last mission that took pictures of Io.
What about future missions?
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Future missions such as JUICE (which stands for Jupiter Icy Moon Explorer) could help
us better understand the wonders of Jupiter's moons.
JUICE is an ESA mission to the Jovian system, and it is intended to end up in Ganymede orbit.
It is scheduled for launch in 2022, with an arrival planned for July 2031. This mission
will use instruments to monitor Io's volcanic activity.
Another amazing mission will be the Europa Clipper one, a NASA mission to Jupiter focused
on Europa. It is scheduled to launch in 2024 and, if
everything works out well, it will arrive at Jupiter in 2030.
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