Jupiter’s Great Red Spot (GRS) is a ten thousand mile wide storm that has been churning in the planet’s atmosphere for centuries, but new data from a couple of studies revealed at a NASA press conference have shown that the GRS and its feeder currents extend deeper into the gas giant than we previously knew.
At Press conference, two teams of astronomers, Scott Bolton and his colleagues, as well as Marzia Parisi and her colleagues, reported that they used microwave radiometry and gravity measurements, respectively, to characterize Jupiter’s atmospheric vortices, including the GRS. Both teams relied on the Juno space probe: Bolton’s group used Juno’s onboard microwave radiometer to characterize the vertical structure of the GRS (as well as two other storms) and found that they extend far below the cloud layer of the planet.
In terms of its footprint, the GRS is more than capable of swallowing the entire Earth. It’s smaller now than it used to be and it’s faded, but it’s still horrible. Conservatively, the maelstrom extends at least 120 miles into the planet, but could be up to 300 miles deep; it could go even further, but that’s as deep as Juno’s radiometer can “see” it. “The Great Red Spot is as deep inside Jupiter as the International Space Station is high above our heads,” said Parisi, a JPL research scientist. But compared to the zonal jets that feed the storm, the GRS is just a whirlpool on the surface. Those zonal currents cut nearly two thousand miles deep into the lightless depths of Jupiter.
Long-lasting, stable, giant storms are a recurring theme on Jupiter, and with Juno we finally get a chance to look under the cloud tops. The planet is mostly hydrogen by mass and does not have a true surface; instead, we believe that it gradually transitions through thicker, denser clouds into opaque ammonia mud with perhaps the density of water. A thousand kilometers below the cloud tops, we observe such extreme cold that the distinction between liquid and gas begins to blur. Hydrogen becomes a transparent supercritical fluid, free of surface tension and capable of floating through solids as a gas rather than seeping out as a liquid. But there is nothing solid on Jupiter. The wind belts blast unobstructed paths through the gas giant’s atmosphere. These stable circulations produce resident storms arranged at the planet’s poles with geometric precision, in a perfect octagon at the north pole and a perfect hexagon at the south. They are believed to produce raindrops of helium, neon, and perhaps even diamonds, which fall into a bottomless ocean of liquid hydrogen that never solidifies, not even in the planet’s core.
As Juno continues to investigate the planet, we will continue to receive updates. Juno is orbiting Jupiter to learn about the origin and evolution of the planet, study its core and magnetic field, and obsessively photograph everything it can. More data is sure to come, as NASA has extended the Juno mission to at least 2025.
“The beauty of Jupiter is not just superficial,” says Bolton, principal investigator for the Juno mission. “And we are seeing, for the first time, the atmosphere in three dimensions.”