6 mins read 24 Mar 2021

Tracking storms on Jupiter from backyards in Australia

The Great Red Spot is a storm that has been raging on Jupiter for over 400 years and was thought to be finally shrinking. However, new data, collected by professional and  amateur astronomers might now prove otherwise. Dr. Helen Maynard-Casey, a Planetary scientist from ANSTO who specialises in off-Earth mineralogy, writes about partner Andy helping catch Jupiter’s storm in action from their backyard.

Disturbances and turbulence surrounding the Great Red Spot on Jupiter. Credit: Andy Casely.

The most famous storm in the Solar system, Jupiter’s Great Red Spot, has changed rather dramatically over the years.  When it was first observed in the 17th Century astronomers at the time estimated it to be 40,000 km wide, but this has shrunk to only 15,000 km today (though still big enough to swallow the Earth and have room to spare).  

When the Juno spacecraft arrived in orbit about the giant planet, scientists hoped it would help answer what was happening to the Great Red Spot.  But the spacecraft found itself confined to a 53-day orbit, meaning that another group of people had to step in to help out with the observations - only this time, it was from Earth. 

This includes catching the planets and all the things that might be happening on them, from our own backyard. And although you might be thinking that this is your regular, run-of-the-mill kind of observation of the wanderers as they cross the sky - there’s some really exciting community science that happens here.

“I think there is something flaking off the red spot on Jupiter”

Andy Casely and his trusty C14 in our backyard in Sydney. Credit: Andy Casely.

Yeah, conversations are a little different in our house.  I suppose that’s the sort of thing you can expect when your partner is one of a small band of amateur astronomers in Australia who can track planetary storms, not from major observatories that are owned by big institutions, but rather from the backyard.  

There’s quite a few people able to take some astonishing images from their backyards in Australia, with this type of imaging not necessarily needing the darkest of skies.  The plunging price of high-speed video cameras has helped too (Andy actually takes videos of the planets, then stacks the best frames together).   

Those located in Queensland can take advantage of better seeing more often, less affected by the jet stream. But even from our backyard in suburban Sydney, Andy has been able to extend his terrestrial storm watching hobby to other planets.

Juno and the Changing Red Spot

After first noticing a flake coming off the red spot, Andy took to a forum of fellow amateurs who keep a regular watch on Jupiter.  Many of them were seeing these flakes too - through May-July 2019 hundreds of amateur images were collected. And, of course, the professional scientists were now very interested too - what was going on?

The professionals pulled together data from JunoCam, Hubble Space Telescope and even managed to get time in late May on the Calar Alto 2.2 m scope.  But to understand what was going on they needed some long spells of data, not feasible with the in-demand professional observatories.  Why didn’t the JunoCam data have all the answers?   

Juno never planned to have eyes on Jupiter all the time.   An elliptical orbit was planned from the very beginning of the mission.  This was in order to shield the sensitive instruments on board from too much exposure to the harsh radiation around Jupiter.   NASA had learned its lessons from the Galileo mission, which saw a number of systems failures after radiation exposure on its eight-year tour of Jupiter and its moons.  

A good run of weather meant that Andy could get a series of images that showed something flaking off the Great Red Spot. During this time the whole storm appeared to get smaller for a while. Credit: Andy Casely.

The original plan was for the elliptical orbit to be 14 days long - which would let the scientists use the instruments to chart the dynamics and features of Jupiter's atmosphere.  However, soon after Juno arrived at Jupiter, engineers discovered serious issues with the craft.  

Examination of this led the team into deciding Juno was going to stay at the initial orbit it had inserted into, only having a close approach with the giant planet every 53 days.  Great for the longevity of the mission, but tougher for those scientists wanting to track storms on Jupiter.

This is why collaborating with the amateur astronomers became even more important.  As Juno was struggling with imaging from its orbit, Jupiter was placed in our skies such that the astronomers in the Southern Hemisphere would have a great view.  

Professional-Amateur (Pro-Am) collaborations have been making discoveries in our Solar system for decades, and there is now a dedicated band of both scientists and amateurs that work together on a number of big questions on the Solar system.

This artist's rendering shows NASA's Juno spacecraft making one of its close passes over Jupiter. Credit: NASA/JPL-Caltech.

So what was going on with the Great Red Spot on Jupiter? Piecing together the data and running some dynamic models of the atmosphere has given a glimpse into the outlook for the biggest storm in the Solar system.  The effects that Andy and others had seen, while they looked very dramatic, seem now to only be only skin deep.  

While it looked that bits of the red clouds were being flaked off by smaller storms running into it,  the true picture wasn’t that simple. In fact, at a deeper level of the clouds, the Great Red Spot had actually been pulling in energy from these smaller storms - which may help answer why this storm has persisted for so many years.

With the Juno mission now hoping to last until 2025, there is doubtless more information to come about the dynamics of its atmosphere.  And, when the clouds allow, Andy and many other amateur planetary observers will be ready to help fill in data between Juno’s orbits. 

A flake of red peels away from Jupiter’s Great Red Spot during an encounter with a smaller anticyclone, as seen by the Juno spacecraft’s high-resolution JunoCam on 12 February 2019. Credit: AGU/Journal of Geophysical Research: Planets.

Dr. Helen Maynard-Casely

Dr. Helen Maynard-Casely is a planetary scientist, her own research focuses on the icy materials that make up the dwarf planets of our solar system. She loves to share stories about science to all.

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