Sulfur and chlorine isotopes in Io’s environment point out that it has been volcanically lively for the whole 4.57 billion-year historical past of the Photo voltaic System.
This international view of Io was obtained in January 1999 by NASA’s Galileo spacecraft. Picture credit score: NASA / JPL / College of Arizona.
Jupiter’s moon Io is essentially the most volcanically lively physique within the Photo voltaic System.
Io’s volcanic exercise is the results of tidal heating from friction generated throughout the moon’s inside as it’s pulled between Jupiter and its neighboring moons of Europa and Ganymede.
Nonetheless, how lengthy this moon has hosted such intensive volcanism isn’t absolutely understood.
As a result of moon’s present degree of volcanic exercise, the floor of Io is consistently being reworked, leaving a geological file of solely the newest million years of its historical past.
Steady isotopic measurements of unstable components in Io’s environment may present info on the historical past of volcanism on Io.
“Io is a moon of Jupiter and is essentially the most volcanically lively physique in our Photo voltaic System,” mentioned Dr. Ery Hughes, a volcanic fluid geochemist at GNS Science.
“Io is in orbital resonance with two different massive moons of Jupiter, Europa and Ganymede.”
“Each time Ganymede orbits Jupiter as soon as, Europa orbits twice, and Io orbits 4 occasions.”
“This configuration causes Io’s orbit round Jupiter to be elliptical quite than round, cyclically altering Jupiter’s gravitational pull on Io.”
“This transformation in gravitational pull causes what we name tidal heating in Io, identical to how the Moon causes ocean tides on Earth, which then causes the volcanism.”
“Nonetheless, it’s unclear lengthy volcanism has been occurring on Io and the way this conduct might need diversified over Io’s 4.57-billion-year historical past.”
“Io has volcanism on such an excessive scale that Io’s floor renews on a regular basis, leaving little hint of the previous.”
“Fortunately, investigating sulfur and its isotopes permits us to probe again in time on Io.”
Within the new research, Dr. Hughes, Caltech researcher Dr. Katherine de Kleer and their colleagues used the Atacama Giant Millimeter/submillimeter Array (ALMA) to look at the gases in Io’s tenuous environment and decide the steady isotopic radios of sulfur- and chlorine-bearing molecules.
The scientists discovered that each components are extremely enriched in heavy isotopes in comparison with common photo voltaic system values because of the lack of lighter isotopes from the higher environment as materials is repeatedly recycled between Io’s inside and environment.
The findings point out that Io has misplaced 94% to 99% of the sulfur that undergoes this outgassing and recycling course of.
This might require Io to have had its present degree of volcanic exercise for its complete lifetime.
“Sulfur is launched from Io’s inside to the environment by tidal heating by way of volcanism,” Dr. Hughes mentioned.
“A few of the sulfur is misplaced to area attributable to Jupiter’s magnetosphere, a bunch of charged particles whirling round Jupiter that hit Io’s environment repeatedly.”
“The sulfur that’s left behind is finally buried again into Io’s inside, prepared to start out the cycle once more.”
“Isotopes of the identical component have completely different weights to one another and due to this fact can behave barely completely different throughout this cycle.”
“It seems that the sulfur that’s misplaced to area on Io is just a little bit isotopically lighter than the sulfur that’s recycled again into Io’s inside.”
“Due to this, over time, the sulfur left on Io will get isotopically heavier and heavier. How a lot heavier depends upon how lengthy volcanism has been occurring for.”
“We discovered way more isotopically-heavy sulfur in Io’s environment than the solar-system common. This requires Io to have misplaced virtually all of its unique sulfur.”
“Based mostly on numerical modelling, this implies Io has been volcanically lively for billions of years, which means tidal heating and the orbital resonance has additionally been occurring for many of Io’s historical past.”
“Sooner or later, the variability of the sulfur isotopic composition of the environment might assist us to quantify the typical tidal heating charge on Io.”
The research seems within the journal Science.
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Katherine de Kleer et al. Isotopic proof of long-lived volcanism on Io. Science, revealed on-line April 18, 2024; doi: 10.1126/science.adj0625
