Unlike Earth and the other inner planets, which are made of rocky material, Jupiter and the other gas giants are mostly – if not entirely – huge balls of gas. Jupiter’s enormous mass allows it to continue holding onto all of the gases it accumulated when it was forming. Since its gases haven’t changed in four billion years, studying its composition is a way to investigate our solar system’s history.
With the exception of its solid core, Jupiter’s interior is probably well mixed, meaning that the composition of its outer atmosphere is likely a good indication of what’s deeper in the planet. By measuring the amount of water in its atmosphere, we can estimate the amount of oxygen – a key component of water – inside Jupiter, a vital step in understanding the planet’s formation.
For example, knowing how much oxygen Jupiter has will help us determine how far away from the sun it was when it formed. Jupiter was initially thought to have been born roughly where it orbits today. But when NASA’s Galileo spacecraft visited the gas giant in the 1990s, it dropped a probe into the planet’s clouds and discovered evidence that suggested otherwise. The probe found more heavy elements – carbon, nitrogen, sulfur, argon, krypton, and xenon – than expected. This finding was a surprise because chemicals with these elements could only have formed in extremely low temperatures, and they were mixed with materials that form in warmer conditions.
One possible explanation for the abundance of heavier elements is that Jupiter actually formed farther away from the Sun than its present orbit. There, it was able to collect these materials that had condensed in the frigid regions beyond the orbit of Neptune. Then, Jupiter migrated inward to its present orbit. Another theory allows for Jupiter to have formed where it is now. In this scenario, the heavier materials were trapped inside ice crystals that populated Jupiter’s neighborhood. As the planet formed, it gobbled up these crystals.
It turns out that the two theories predict different amounts of water in Jupiter. Juno’s Microwave Radiometer and JIRAM instruments will measure this water content and determine which theory is correct – or if we have to come up with entirely new ideas to explain Jupiter’s composition.
Because the existence of Earth and of life depends on the presence of oxygen and these other heavier elements, learning how Jupiter acquired these materials can also tell us something about our very own origin.
With the exception of its solid core, Jupiter’s interior is probably well mixed, meaning that the composition of its outer atmosphere is likely a good indication of what’s deeper in the planet. By measuring the amount of water in its atmosphere, we can estimate the amount of oxygen – a key component of water – inside Jupiter, a vital step in understanding the planet’s formation.
For example, knowing how much oxygen Jupiter has will help us determine how far away from the sun it was when it formed. Jupiter was initially thought to have been born roughly where it orbits today. But when NASA’s Galileo spacecraft visited the gas giant in the 1990s, it dropped a probe into the planet’s clouds and discovered evidence that suggested otherwise. The probe found more heavy elements – carbon, nitrogen, sulfur, argon, krypton, and xenon – than expected. This finding was a surprise because chemicals with these elements could only have formed in extremely low temperatures, and they were mixed with materials that form in warmer conditions.
One possible explanation for the abundance of heavier elements is that Jupiter actually formed farther away from the Sun than its present orbit. There, it was able to collect these materials that had condensed in the frigid regions beyond the orbit of Neptune. Then, Jupiter migrated inward to its present orbit. Another theory allows for Jupiter to have formed where it is now. In this scenario, the heavier materials were trapped inside ice crystals that populated Jupiter’s neighborhood. As the planet formed, it gobbled up these crystals.
It turns out that the two theories predict different amounts of water in Jupiter. Juno’s Microwave Radiometer and JIRAM instruments will measure this water content and determine which theory is correct – or if we have to come up with entirely new ideas to explain Jupiter’s composition.
Because the existence of Earth and of life depends on the presence of oxygen and these other heavier elements, learning how Jupiter acquired these materials can also tell us something about our very own origin.