June 21, 2024
1 Solar System Way, Planet Earth, USA

Io has been volcanically active throughout its history

Jupiter's moon Io is a volcanic powerhouse. It is the most geologically active world in the Solar System, with more than 400 volcanoes and vents on its surface. It has always been like this? A team of planetary scientists say yes, and they have the chemical receipts to prove it.

In a recent paper, the team led by CalTech scientist Katherine de Kleer cites data from millimeter observations of elemental isotopes found in Io's eruptions. They discovered that chemicals such as chlorine and sulfur exist in greater quantities on Io than in comparable places in the Solar System. Analysis shows that Io has not started erupting recently, but has been happening for most of its history. And it is so volcanic that it practically resurfaces approximately every million years.

The discovery of volcanism on Io was one of the main results of the Voyager mission. When the two spacecraft passed by Jupiter in 1979, their images revealed Io's volcanic features and plumes. Since then, the Galileo, Cassini-Huygens, New Horizons and Juno missions have also sent images. The Jovian system and its moons are also frequent targets of ground and space observatories, including Hubble Space Telescope and JWST.

Facts about Io

Io is the fourth largest Jovian moon and is one of the four Galilean satellites. It orbits closer to Jupiter and is pulled by a gravitational tug-of-war between Jupiter and the other Galilean moons. The result is a process called “tidal heating” in the depths of Io, produced by friction. That generates heat, which melts Io's interior and opens vents so heat and melted material can escape to the surface.

Artist's concept of the interior of Io.  By Kelvinsong - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31526383
Artist's concept of the interior of Io. By Kelvinsong – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31526383

This small moon is mainly silicate rock on an iron or iron sulfide core. The surface is scarred by volcanoes and deformed by compression forces beneath the crust. The most obvious features are the volcanic mountains, columns and lava flows. Currently, Io's volcanoes resurface the landscape at a rate of about 0.1 to 1.0 cm per year. They also paint their surface in an amazing variety of colors. During Voyager 2's flyby, people often compared its appearance to a pizza. The colors come mainly from sulfur and sulfur compounds deposited in the landscape.

Normally, geologists would look at its surface and count the craters to get an idea of ​​its age. But, since volcanic flows erase craters, there is no easy visual way to determine how long volcanic features have existed. However, it turns out that the abundance of certain isotopes of sulfur and other elements could provide a good record of the history of volcanism on Io.

Analyzing the chemistry of Io

Io has probably lost mass in space throughout its history. de Kleer and his colleagues point out that their supply of volatile elements should be highly enriched in heavy stable isotopes. This is because atmospheric escape processes generally favor the loss of lighter isotopes. They suggest that measurements of stable isotopes of volatile elements, such as sulfur and chlorine, could provide precise details about the history of volcanism on Io. So it makes sense now to do a thorough chemical analysis of Io's volcanic emissions and extrapolate it.

Understanding Io's current chemistry requires, among other things, a good idea of ​​its mass loss history. Io's mass loss occurs due to collisions between atmospheric molecules and energetic particles trapped in Jupiter's magnetosphere. If this continued throughout Io's history, then its chemistry should provide evidence of the volcanic past. In their paper, the team discusses the assumptions they made, including estimates of Io's initial sulfur inventory, as well as possible early rates of mass loss that could affect its current abundances of sulfur and chlorine, two elements that help determine volcanism. past and present. .

To get that story, the team used the Atacama Large Millimeter Array to observe gases in Io's atmosphere. The objective was to measure SO2, SO, NaCl and KCl in various forms and determine the proportions of 3. 4Yes to 32Sand 37Cl a 35Cl. After analyzing the data, the team found that Io has lost at least 94 to 99 percent of its available sulfur over time. Additionally, measurements show enriched levels of chlorine. This probably indicates that Io has been volcanically active over time. It is also possible that this small moon experienced higher rates of outgassing and mass loss earlier in its history. More measurements should help scientists further limit Io's volcanic activity.

For more information

Isotopic evidence for long-lived volcanism on Io
Violent volcanoes have devastated Jupiter's moon Io for billions of years

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