The Juno mission was making its 51st flyby of the gas giant planet and its moons when it viewed the 'tortured moon' Io in stunning detail.
 |
Io as seen by NASA's Juno probe during a close flyby of
Jupiter on May 16, 2023. (Image credit: NASA/Kevin M. Gill) |
NASA's Juno mission has made its 51st close flyby of
Jupiter, catching stunning images of its moon Io, in the process.
Juno flew past Io on Tuesday, May 16, on a flyby that
brought it closer to the volcanic moon of Jupiter than ever before. The
spacecraft passed with just 22,060 miles (35,500 kilometers) of the Jovian
moon's surface.
If this Jovian moon appears tranquil in these images (which
NASA's Planetary Science Division released via Twitter on May 18), then
appearances can be deceptive. Io isn't just the most volcanic moon orbiting the
gas giant; it also happens to be the most volcanic world in the entire solar
system.
Some of the detailed images taken by Juno and its visible
light imager JunoCam show the Io's red-hued surface scarred by its fiery
volcanoes. An infrared view of the moon captured earlier during a May 1 flyby
by Juno's JIRAM (Jovian InfraRed Auroral Mapper) shows the source of this
scarring, revealing multiple hotspots of volcanic activity over the surface of
the moon.
 |
An image of Io taken by NASA's Juno probe during a close
flyby of Jupiter on May 16, 2023. (Image credit: NASA/Kevin M. Gill) |
"Io is the most volcanic celestial body that we know of
in our solar system," Juno principal investigator Scott Bolton said in a
statement prior to the flyby. "By observing it over time on multiple
passes, we can watch how the volcanoes vary — how often they erupt, how bright
and hot they are, whether they are linked to a group or solo, and if the shape
of the lava flow changes."
 |
Juno observed Jupiter's moon Io in visible and infrared
light during a May 1, 2023 flyby, yielding this composite view showing hot
spots across the surface of the solar system's most volcanically active world.
(Image credit: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM) |
NASA estimates that there are hundreds of actively erupting
volcanoes over the surface of Io, the third largest moon of Jupiter, and the
fifth from the gas giant located at around at 262,000 miles (422,000 kilometers)
from its surface. These volcanoes can blast lava dozens of miles into the thin
water-less atmosphere of Io, which itself is around the size of Earth's moon.
 |
Jupiter and Io as seen by NASA's Juno probe during a close
flyby on May 16, 2023. (Image credit: NASA/JPL-Caltech/SwRI/MSSS Image
processing: Kevin M. Gill (CC BY)) |
This extreme volcanic activity is believed to arise as a
result of the tremendous gravitational influence of Jupiter, the most massive
planet in the solar system, as it plays a game of "tug-of-war" with
Io against its fellow large Jovian moons Europa and Ganymede. This gives rise
to tremendous tidal forces that have the effect of squashing and squeezing Io,
causing its surface to bulge up and down, or in and out, by as much as 330 feet
(100 meters).
Even before the 51st flyby of Jupiter, since arriving at the
gas giant in 2016, the Juno spacecraft had traveled over 510 million miles
making close encounters with the three of the four largest moons of the planet,
the icy moons Europa and Ganymede, and fiery moon Io. The four large moons,
including frozen Callisto, are collectively known as the "Galilean
moons" after Italian astronomer Galileo Galilei, who first observed them
in 1610.
"We are entering into another amazing part of Juno's
mission as we get closer and closer to Io with successive orbits. This 51st
orbit will provide our closest look yet at this tortured moon," said
Bolton. "Our upcoming flybys in July and October will bring us even
closer, leading up to our twin flyby encounters with Io in December of this
year and February of next year when we fly within 1,500 kilometers of its
surface."
Juno wasn't actually designed to study these moons; rather,
its instruments and sensors were intended to investigate Jupiter's atmosphere
and interior. Yet despite this, during its 50 flybys of the gas giant, the NASA
craft has been able to collect vital data about the Jovian moons and, as this
flyby illustrates, some incredible images.
"All of these flybys are providing spectacular views of
the volcanic activity of this amazing moon," Bolton concluded. "The
data should be amazing."
Jupiter's large moons will be under further intense scrutiny
when the JUpiter Icy Moon Explorer (JUICE) reaches them in 2031. Juice will
search for the conditions on the ocean-bearing moons of Europa and Ganymede
that would be needed to support the existence of life.