Unraveling Io’s Evolutionary Secrets: The Role of Heavy Isotopes in Modern Eruptions

Io, one of Jupiter’s largest moons, is experiencing modern eruptions that are expected to be enriched in heavier isotopes of chemical elements. This is due to the escape of lighter isotopes into space over time. By measuring the ratios of heavy isotopes to lighter isotopes in Io’s atmosphere, researchers can calculate how long it took for Io to reach its current state from its original underground reservoir of compounds.

Recently, a team of researchers used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe gases in Io’s atmosphere, particularly sulfur. They estimated the moon’s original reservoir of isotopes using ancient meteorites and found that Io has lost 94 to 99 percent of its original sulfur reservoir. This indicates that the moon has been erupting for approximately 4.5 billion years.

This finding aligns with existing models of Jupiter’s evolution and the inner moons’ history. Despite the chaotic dynamics of planetary satellites, Io, Ganymede, and Europa have been orbiting in a similar pattern for billions of years. This long history of orbital dance suggests that Io’s current state is representative of its evolution over time.