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The biggest storm in the solar system, Jupiter's iconic Great Red Point, has been crossing the gas giant for at least 180 years. In 1979, at the time of Jupiter's overflights of Voyager transport aircraft, the storm had a width of three Lands and spread over 40,000 km. Now its size is 16,000 km, a little wider than the Earth.
NASA reported in 2018 that the large red spot had further decreased. And now, amateur astronomers around the world have seen a long flow of gas – more than 10,000 km long – coming out of the storm. Is this a sign that the storm is dying?
The big red spot of Jupiter compared to the Earth. Image of Jupiter captured by the Cassini spacecraft in 2006. Photo: Brain0918 / NASA
The big red spot is an anticyclone: it moves in the opposite direction to that of the rotation of the planet. Two jet stream strips pass above and below the point. The darkest, called South-Equatorial Belt (SEB), passes over the storm opposite to the rotation of the planet. The lighter jet stream passes under the storm in the direction of rotation of the planet. Together, these two opposite streams contained the large red spot in a fixed latitude for centuries.
Throughout 2019, high-speed vortices in Jupiter's SEB were seen interacting with the large red spot, resulting in a dark matter flow. Amateur astronomers recorded one of these interactions in May, which lasted a whole week. The resulting current is formed more than 10,000 km from the west end of the storm. That's more than half the size of the storm itself. The flecked stream seemed to join the SEB and dissipate inside.
An amateur astronomer captured this view of the snowflake coming off the big red spot on May 20, 2019. Photo: ALPO, Japan
It's the biggest activity of its kind ever, but it's not the first. As we speak, NASA's Juno spacecraft is orbiting Jupiter and has photographed the large red patch several times over from a height of 8,000 kilometers. In two of his closest passages, Juno observed similar but smaller flakes emerging from the west of the storm. The infrared observations of 2017 with the help of the Gemini Observatory also revealed a hook-shaped structure in the same place.
Small flash of the big red spot observed by Juno on February 12, 2019. Credit: NASA
In 2019, observers found that these watercourses were interacting with the storm and cutting some of them repeatedly. However, as Jupiter turns on itself every 10 hours, the storm is not always visible. The retrograde storm takes about six Earth days to circle the planet.
Many amateur astronomers are currently working around the world to continue to get clear pictures of the activity in and around the storm. Around June 10, Jupiter will be closer to Earth and shine much more than Sirius, the brightest star in the night sky on Earth. Even small telescopes will be able to clearly see the giant storm.
Jupiter's next approach to Juno is July 21st. Juno operators will give priority to instruments that can investigate the storm in more detail: the microwave radiometer (MWR) and JIRAM, the infrared imager, and of course the powered JunoCam.
The orbit of Juno is very close to Jupiter, which gives it a more refined look. Credit: NASA
While May's giant flakes have dissipated in the SEB, the data from MWR and JIRAM will allow scientists to infer changes in the internal activity of the Great Red Spot. MWR and JIRAM can see through the highest cloud layer, deep in the storm.
In fact, the MWR is the instrument that found that the roots of the Great Red Spot had penetrated deeper than 320 km; they could dive lower, because 320 km is only the observation limit of MWR. The winds on the periphery of the giant storm blow the fastest, at about 400 km / h on average. Thus, when interacting with high velocity streams, particularly during the peeling process, a substantial amount of heat is produced. That's exactly what JIRAM is taking over. If bursting intensifies, Juno's instruments will also be able to record it.
At this point, no one really knows what's going on. The big red blotch should disappear after 20 years, but it was before the scientists noticed the flaking. Storms on gas giants last much longer because, unlike rocky planets, including the Earth, there is no solid surface to absorb the momentum of the storm. But it seems like the biggest storm in the solar system will die after all. Until then, as the community of amateur astronomers and the Juno team work together to understand what's going on, all we have to do is wait.
Jatan Mehta is a science writer with a background in physics and astrophysics research experience. He is passionate about spatial, technological and scientific communication. His wallet is at jatan.space.
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