An Interview with Jovian Vortex Hunters

This is a guest post by summer intern Anastasia Unitt.

Talking about the weather is a national pastime in England. When I meet Dr. Ramana Sankar on a sunny day in Oxford, we find ourselves discussing dramatic clouds and ferocious storms – in stark contrast to the empty blue skies above us. Ramana is telling me about the turbulent meteorology of our solar system’s fifth planet: Jupiter.

Jupiter is a gas giant. Its atmosphere is made of very different stuff to ours, predominantly hydrogen and helium, but it does have clouds of water vapour like we do, as well a variety of storms and hurricanes. These vortices are governed by the same physics as Earth’s own, just on a much larger scale; Jupiter’s most famous storm, the Great Red Spot, is twice the width of Earth and has raged for over 300 years. Wind speeds on the planet can approach 900 miles per hour at its poles, encouraged by jet streams formed by the planet’s 10 hour long rotations – the fastest in our solar system. For those interested in meteorology, it’s a fascinating place to study.

Ramana tells me that to research Jupiter’s weather he works with a very important colleague: Juno, a space probe launched in 2011. Five years later in 2016 it reached Jupiter. Ever since, it has been sending back data, including images which show a diverse array of weather formations, varied in form, swirling, morphing, spinning. I’m surprised by how many different colours appear in these clouds, not only orange as I expected, but also shades of blue and grey. The enormous variety of features in the images provide an opportunity to learn more about how storms work on Jupiter, and Ramana explains that to do this they need to collect observations of the weather captured in Juno’s images. There are thousands of these pictures, so he has enlisted citizen scientists on Zooniverse to look through them and annotate features. They mark storms, clouds, and anything else they notice, building a catalogue of formations. With their help Ramana can spot repeating patterns, as well as explore unusual or rare vortices.

Swirling Jovian storms, in images captured by NASA’s Juno space probe.

I find myself wondering what causes this dramatic Jovian weather, and according to Ramana astronomers are curious about this too. To answer this question, he says we need to go back to how the planet was made: “long ago, the sun formed and around it was this disc of gas and dust, which contracted to form different planets.” This compression generated enormous amounts of heat; even now, the temperature at Jupiter’s core is thought to be about 24,000°C, maintained by high internal pressure due to its immense size. As Ramana puts it: “Imagine a boiling kettle. Bubbles are coming up due to the stove heating the bottom of the pan. The storms on Jupiter are these bubbles, but rather than forming over two minutes, they form over 5-10 years.” This is in contrast to Earth, where storms form due to heat from the sun. I ask Ramana what this internally-originating heat means for his study of Jupiter’s weather, and he explains that this is something he is exploring. “The question comes down to: why are these storms distributed at specific locations, why is the heat preferentially pointed one way versus the other? Getting the catalogue of vortices and seeing where they’re forming can help us.”

With this aim in mind, citizen scientists have classified over 35,000 photographs of Jupiter’s stormy surface. When I ask Ramana what their best finding has been so far, he pauses for a moment before he responds, clearly spoilt for choice amongst the many complex vortices they have observed. He eventually lands on one particular feature: “One of my favorite types of vortex is called a brown barge, and that’s because you’d imagine vortices are generally circular, but a brown barge is very elongated. Imagine a brown cucumber, that’s essentially what it is.” Ramana explains that precisely what causes this brown colouration is a mystery. It could be chemicals present in the clouds themselves, or haze particles in the upper layers of the atmosphere reacting with sunlight. However, the citizen scientists have made an interesting discovery about these formations: “Volunteers are finding barges which are not brown. So for all this time I thought that brown barges are brown, but it turns out there are more complications. Investigating these not-so-brown barges is a new avenue for research.”

Not-so-brown barges. On the left is an image of a typical brown barge. On the right are examples of barge-like vortices without the typical brown colouration.

When not enthusing about Jupiter’s (mostly) brown cucumber-shaped storms, Ramana is quick to point to his citizen scientists as one of his favourite parts of the project. They’ve gone above and beyond their role as storm counters; some have even been digging into additional data, outside of what Ramana has provided. “A lot of volunteers kind of go into the depths. They’re pulling in all of this data from everywhere else, like news websites, even mission reports, things like that. [The] volunteers go out of their way to explore the data by themselves.”

It sounds to me like the citizen scientists have been understandably bewitched by Jupiter’s diverse and spiraling cloud formations. On the Zooniverse talk boards I can see them excitedly discussing all kinds of interesting storms and features that they have discovered. Now they have built Ramana’s catalogue of storms, I enquire what his plans are for the next steps. “The idea is to create a subset of interesting features (like the not-so-brown barges), and then either use some sort of numerical weather modelling code to study how these features formed, or we could get context images to all of these features: look one rotation before, one rotation after. How did the feature morph between those 15 hours?” He’s excited about the findings – the volume of data the citizen scientists have analysed means there’s plenty to explore going forward.

It’s fascinating to hear how much these volunteers have contributed to our understanding of the weather on a planet 365 million miles away from our own. For a while Ramana and I discuss the motivations of citizen scientists. Is it a desire to learn, an attraction to science, or simply a way to pass the time? Ramana says from his experience it’s a mixture of the three. “The bottom line that I personally have heard about from people who have done Zooniverse projects is that they just want to spend five minutes of their time doing something else that’s not for their daily lives. Log in, classify a few things, get back to work.” Unfortunately it’s also time for Ramana and I to get back to work, so we part ways. However, as I’m walking under England’s blue and (currently) cloudless sky, I find I’m carrying thoughts of Jupiter’s distant swirling storms along with me.

Would you like to be a Jovian vortex hunter? Follow the link to take part in Ramana’s project:

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