(being continued from 16/05/16)
a)Is Jupiter’s moon Io gradually losing mass because of all the volcanic activity? And if so, what will be the moon’s final fate?
Much of the material spewed from Io’s volcanoes never leaves the moon’s gravitational influence. Instead, it falls back to the surface, creating rings of material that circle Io’s volcanoes, such as those that appear around Pele and Tvashtar Catena in these Galileo spacecraft images.
NASA/JPL/University of Arizona
Yes, Io is losing mass because of its volcanic activity, but not as much as you’d think. Several of Io’s volcanoes spray gas and particles high above the surface, but most of that material falls back down to the surface, creating colorful and bright ring deposits. However, some material does eventually escape the influence of Io’s gravity and enters Jupiter’s. This material may stay in orbit around Jupiter as part of the Io Plasma Torus, a ring of electrons and ions produced by Io and heated by Jupiter’s magnetic field as it rotates.
Results from the Galileo spacecraft show that the total mass loss rate from Io is about 2,200 pounds (1,000 kilograms) per second. At this rate, the total mass lost by Io over the lifetime of the solar system is about 7×1020 pounds (3×1020 kg). This is 0.33 percent of Io’s total mass. So only a tiny percentage of Io’s mass will disappear over the lifetime of the solar system, leaving the moon intact as the Sun and the solar system age.
Senior Scientist, Planetary Science Institute,
b)These Bright Spots Are Alien Volcanoes
Proof that Jupiter’s moon Io does lava better than Earth
Io, in all its volcanic glory, as seen in infraredNASA / JPL-CALTECH / SWRI / ASI / INAF / JIRAM / ROMAN TKACHENKO
As Voyager 1 approached Jupiter in the 1970s, scientists expected the spacecraft to find a world not unlike our moon. Io, the innermost of Jupiter’s largest moons, is about the same size and mass as the moon. It seemed reasonable to predict Io would turn out to be a cold, rocky world studded with craters, too.
Instead, Voyager found a world alive with volcanoes. The first plume was spotted by Linda Morabito, an engineer on Voyager’s imaging team at nasa’s Jet Propulsion Laboratory, as she sorted through the spacecraft’s data. The photograph was the first evidence of volcanic activity somewhere besides Earth.
Today, Io is known to be the most volcanically active place in the solar system. The moon is teeming with hundreds of volcanoes, some of which can spew lava dozens of miles into the moon’s thin atmosphere of sulfur dioxide, a chemical compound that is sometimes used to preserve foods on Earth.
A number of different nasa spacecraft have flown by Io since Voyager and captured their own photographs of the moon. But one of the best views of Io is outside of the capabilities of the typical camera.
The photo at the top of this story shows Io in all its volcanic glory in infrared light, which the human eye can’t see, captured by the Juno spacecraft’s Jovian Infrared Auroral Mapper instrument. Each bright spot is the glow from a volcanic feature on the moon’s surface. The image was created by Roman Tkachenko, an amateur astronomer and music producer in Kursk, Russia, and one of the dozens of people who assembles raw data from the Juno spacecraft, which has been orbiting Jupiter since 2016, to produce beautiful photos of the planet and its moons.
Tkachenko took it a step further and identified the features, all 25 of them:
NASA / JPL-CALTECH / SWRI / ASI / INAF / JIRAM / ROMAN TKACHENKO
Io’s volcanism is the result of a phenomenon known as tidal heating. Io orbits between Jupiter and the planet’s other large moons, Europa and Ganymede. This configuration means Io is constantly experiencing the gravitational pull of both its parent planet and its sibling moons. The tugging heats up Io’s interior and melts rock to produce magma that spews out from beneath the surface when it can find a crack.
The magma, free to move over Io’s surface, pours into existing impact craters and buries them under a fresh new layer of rock as it solidifies. The flowing lava regularly renews the surface of Io, erasing the evidence of violent collisions that are permanently etched on the faces of other celestial bodies, like our moon.
The first images of Io from spacecraft gave no indication that the moon was rolling in volcanoes. Here’s the shot taken by Pioneer 11, one of two nasaprobes launched in 1973 to study the asteroid belt between Jupiter and Saturn, at left. Pioneer’s instruments helped scientists to estimate Io’s mass, which then allowed them to determine the moon was made of mostly rock, not ice.
A few years later, in 1979, Voyager 1 caught one of Io’s volcanoes in action. “It was so remarkable it was almost shocking,” Morabito said in 2002, recalling her discovery of the plume. “I had expected yet another dead, [cratered] moon, and yet this seemed alive.”
JPL / NASA
Other nasa spacecraft have documented Io since, including Galileo, which orbited Jupiter for seven years, Cassini, which orbited Saturn for 13 years, and New Horizons, currently on its way to a ring of icy objects beyond Neptune. Photos of Io in true color reveal a world of pale yellows and greens that resembles moldy cheese. Moldy, volcanic cheese.
MARINA KOREN is a senior associate editor at The Atlantic.
c)The Oxygen Neutral Cloud Surrounding Jupiter’s Volcanic Moon
Japan’s Hisaki satellite takes measurements of faint oxygen emissions from Io.
SOURCE: Journal of Geophysical Research: Space Physics
A montage of New Horizons images of Jupiter and its volcanic moon Io, taken during the probe’s flyby in early 2007. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/GSFC
By Kate Wheeling 20 June 2018
Lakes of lava and hundreds of volcanoes dot the surface of Jupiter’s moon Io, some spewing lava dozens of kilometers into the air. Only slightly larger than our own planet’s moon, Io is the most volcanically active place in the solar system. Its thin atmosphere is made up largely of sulfur oxides. As Io orbits, neutral gas particles escape its atmosphere and collide with electrons, giving rise to a donut-shaped cloud of ionized particles around Jupiter, known as the Io plasma torus.
Exactly how those neutral gases escape Io’s atmosphere is not well understood, however. Previous studies have shown that most atomic oxygen and sulfur escape Io’s atmosphere by colliding with energetic particles, such as torus ions, which bump the particles out of the atmosphere in a process known as atomic sputtering. Some of the particles escape from Io’s gravity and form clouds of neutral sulfur and oxygen. Here Koga et al. provide new insights into the role of the neutral cloud in the Io plasma torus.
The team took advantage of data collected by Japan’s Hisaki satellite, which launched in 2013 and became the first space telescope to observe planets like Mars and Jupiter from Earth’s orbit. The researchers used spectrographic data from the Extreme Ultraviolet Spectroscope for Exospheric Dynamic (EXCEED) instrument aboard the satellite to measure atomic emissions at 130.4 nanometers around Io’s orbit. The measurements were collected over 35 days between November and December 2014, a relatively calm volcanic period for the moon.
The authors found that Io’s oxygen cloud has two distinct regions: a dense area that spreads inside Io’s orbit, called the “banana cloud,” and a more diffuse region, which spreads all the way out to 7.6 Jovian radii (RJ). The team plugged the satellite observations into an emissions model to estimate the atomic oxygen number density. They found more oxygen inside Io’s orbit than previously thought, with a peak density of 80 atoms per cubic centimeter at a distance of 5.7 RJ. The team also calculated a source rate of 410 kilograms per second, which is consistent with previous estimates.
This study provides the first good look at Io’s neutral cloud, which has historically been too dim to measure. Neutral particles from Io’s atmosphere are one of the primary sources for charged particles in Jupiter’s massive magnetosphere. Ultimately, the authors note, a better understanding of the neutral cloud will provide important insights into the gas giant’s magnetosphere. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2018JA025328, 2018)
—Kate Wheeling, Freelance Writer
Citation: Wheeling, K. (2018), The oxygen neutral cloud surrounding Jupiter’s volcanic moon, Eos, 99,https://doi.org/10.1029/2018EO100631. Published on 20 June 2018.
Text © 2018. The authors. CC BY-NC-ND 3.0