In Jupiter's swirling Great Red Spot, NASA spacecraft finds hidden depths
Enlarge this image toggle caption NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstad/Sean Doran (c) CC NC SA NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstad/Sean Doran (c) CC NC SA
Jupiter is the largest planet in the solar system. However, it also hosts the most powerful storm. It is known as the Great Red Spot. This vortex has been swirling for hundreds of years. It is larger than our planet and yet, we don't know much. Scientists could only see the spot from far away until now. We now have a glimpse inside Jupiter's storm thanks to the NASA spacecraft that was launched 10 years ago.
The Great Red Spot looks like a supersized storm here on Earth. Paul Byrne is a planetary scientist at Washington University. It's not that different from the kinds of phenomena we know as hurricanes, cyclones, or typhoons here on Earth.
The Great Red Spot, which measures 10,000 miles in size, is the largest storm in the solar system. It has been continuously observed for approximately 200 years. However, it has been around longer. Compare that to the large storms on Earth which typically last only a few days or even weeks.
Scott Bolton, NASA's Juno mission principal investigator who sent a spacecraft to the moon, stated that "we believe this thing" is very old. It is not clear how it can last this long.
Scientists could only see the storm from far away before Juno. They could see the storm changing in shape and shrinking from afar.
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NASA's Juno mission was launched from Cape Canaveral Space Force Station, Florida in 2011, and reached Jupiter in 2016. The spacecraft made slight adjustments to its course and passed the Great Red Spot twice in 2019.
Bolton and his team used microwave sensor to cut into the storm's depths, resulting in the first 3D model for the Great Red Spot. It's a pancake because it's so large at the top. However, the pancake's thickness is thicker than we expected.
These storms are called vortices by microwave observations. They extend below Jupiter's cloud deck. The Great Red Spot extends 200 miles beyond the cloud deck of Jupiter. It is further than the depths where water condenses and clouds form.
Bolton says that this is very different from the way Earth's atmosphere functions. This is largely due to water, clouds and condensation. "This will require new models and new ideas to explain how it works."
Measuring Great Red Spot's Gravity
The Juno spacecraft soared at an astonishing 130,000 miles per hour during its 2019 orbit of the Great Red Spot. It is so large that the storm's gravity field actually jostled Juno spacecraft during its flyby.
Marzia Parisi, Juno scientist at NASA's Jet Propulsion Laboratory (South California) and lead author on a Science paper about gravity overflights from the Great Red Spot, says that "the local gravity tends pull and push away spacecraft as they fly over the vortex and this creates kind of like bumps in Juno's road."
Scientists on Earth could observe the effects of these gravitational "bumps". Because Juno was moved closer or further away from Earth every time they jostled it. This change in distance caused radio waves that were sent back to Earth 400 million miles away from Earth to become subtly compressed and stretched. It is known as Doppler shift.
This technique allows the spacecraft to pick up very small jostles at a rate of 0.01 millimeters per sec.
Parisi says, "The precision required for the Great Red Spot to obtain its gravity during the July 2019 flyby was staggering." Parisi said that gravity observations were in agreement with Bolton's microwave measurements, concluding that the storm penetrates Jupiter's atmosphere approximately 300 miles.
The Shrinking Spot
The Great Red Spot is shrinking according to observations. The iconic spot has been shrinking for nearly a century and half. It's not clear how long it will last.
Juno is looking closer at this phenomenon. Bolton says, "What we are doing is seeing up-close what's happening while this shrinking has occurred."
The spacecraft has been observing the storm's flecks getting caught in nearby clouds. Strong conveyer belts on the planet are also stabilizing the storm, and it appears that the storm itself is being trapped.
Bolton stated that "I don’t believe the theory is very advanced enough to connect all of this to the changes in size."
Scientists will be able to use data from Juno to predict what might happen to the Great Red Spot.
Paul Byrne, a planetary scientist, says that understanding the storm's current behavior allows scientists to create more advanced models to simulate it and make predictions about what will happen in future.
Understanding other Jupiter-like Planets
Juno's Juno spacecraft has revealed some interesting facts about the formation of giant planets such as Saturn, Uranus, and Neptune in the early stages of their existence.
Bolton says, "When you get up close to a planet, and this planet is the first we've been able open up and view inside, it is going to reveal a lot about the way giant planets function throughout the galaxy."
Enlarge this image toggle caption NASA/JPL-Caltech/SwRI/MSSS. Image processing: Gerald Eichstadt CC BY NASA/JPL-Caltech/SwRI/MSSS. Image processing: Gerald Eichstadt CC BY
Astronomers have discovered thousands of exoplanets, planets orbiting stars other than our sun. These planets are far away. The closest one is around 10.5 lightyears from Earth. This makes it difficult to observe what is happening on the surface.
These exoplanet candidates include around 1,400 gas giants similar to Jupiter. Scientists can gain a better understanding of the events on Jupiter by studying what is happening in other parts of our solar system.
Byrne says that by understanding the physics behind Jupiter's formation, we can gain a better understanding not only of Jupiter but also of other worlds.