Hello Josh, thankyou for talking with us! Before we take off, could you tell us a little about yourself and your research?
Hi Simon, thanks for inviting me!
Joshua Dreyer ft. Aurora
I’m a PhD student at the Swedish Institute of Space Physics (IRF) and Uppsala University, just started my third year. My research is focused on Saturn’s ionosphere (the region of the upper atmosphere with a significant amount of charged particles) and the interaction of the rings with it. So far I’ve been working with data from Cassini’s final orbits into the deeper parts of the ionosphere, mainly looking at the chemical composition.
Before I started working on this, I did my B.Sc. in physics at the University of Hamburg in Germany and then moved to Uppsala for my master’s studies. To be fair, I was only here for one semester and then had the awesome opportunity to spend the other three semesters studying the polar atmosphere at UNIS on Svalbard. For my master’s thesis (and the subsequent paper that resulted from it) we looked at small-scale auroral features, which was really interesting!
It’s been four years since NASA’s Cassini spacecraft took its terminal plunge into Saturn’s atmosphere. The photographs Cassini took of Saturn and its rings enthralled many of us non-planetary scientists, but how have these observations helped researchers such as yourself?
That was quite the event, I actually attended a livestream of Cassini’s final moments (RIP) here in Uppsala with my current (then future) colleagues. Of course I had no idea at the time that I would be working on data from the last few orbits a few years down the line, funny how things sometimes work out.
Well, for a start those photographs are just inspiring. I’ve had multiple of them as desktop wallpapers over the past two years, and I think that likely benefitted my productivity 😉
From a scientific perspective, the cameras onboard Cassini (technically called the Imaging Science Subsystem, ISS) helped to reveal many of the finer details of the Kronian system. As an example, some of the photographs showed the change in colour of the polar hexagons. They were able to capture changes in Saturn’s bands, incredible details within the rings, and of course they also took fascinating views of Saturn’s moons. And since the ISS cameras were sensitive to more wavelengths than our eyes can see, we were for example able to peer beneath Titan’s opaque atmosphere with infrared wavelengths.
I can’t really comment on how exactly the photographs are used in all the diverse research my colleagues do on these various aspects. Personally, I mostly work with electron data from Cassini’s Langmuir Probe (built in-house at IRF) and ion data from the Ion and Neutral Mass Spectrometer (INMS), as it’s hard to “see” what’s going on in the plasma. Nonetheless, for scientists that study something that is more easily visible on images, it certainly is a huge plus to actually have high-quality photographs of that particular feature!
For me, one of the most important aspects of including a high-quality camera system on such a mission (and this is not always a given, considering the very limited real estate on a spacecraft) is the fact that photographs are very accessible to the public. These missions are funded by tax payers after all, and I think it’s important to keep people fascinated and intrigued with space and our neighbours in the solar system by showing them how things actually look out there. A lot of scientific data is basically just dots or lines, and while we scientists can certainly get excited if the dots line up well, that might be somewhat less engaging than a view of Saturn backlit by the Sun for most people. Well, let’s be honest – those photographs are hard to beat and probably more engaging for most scientists as well.
Some of the phenomena Cassini captured during its finale were first-time observations, including how Saturn’s rings interact with the planet through a process called “ring rain”. As an Earthling the idea of ring rain sounds utterly alien; could you tell us more about the relationship between Saturn and its rings?
Good question! Of course we are still in the process of figuring out the answer to that rather complex question – but ring rain is one of the more senior (discussed already in the 1980s, I believe) and well-known hypotheses. The basic idea is that charged water ice particles from the rings can stream along the magnetic field into Saturn’s ionosphere at mid-latitudes in both hemispheres, which majorly affects the local plasma chemistry. So the name actually isn’t too misleading, although maybe “ring snow” would be more fitting.
Similarly, Cassini results have shown quite a significant influx of neutral ring particles into the equatorial ionosphere (which is more the region that I’m studying). Electrically neutral particles can move more freely, as they don’t “need” to follow the magnetic field. They basically fall from the innermost D ring into the upper atmosphere, due to collisions knocking them off their orbit and gravity pulling them inwards. This also seems to have a large effect on the local plasma, which otherwise would be mostly dominated by hydrogen and helium ions. It looks quite a bit more complex than that, with many heavier species such as hydrocarbons being present. This is very much an ongoing area of research and how exactly this infalling dust (as we call it) affects to ionosphere will be the focus of my next two papers as well.
Then there is also the simple fact that the rings shadow Saturn itself, which decreases the incoming solar radiation. This affects the photoionisation rates, and the paper I’m currently working on looks into the fact that we can see even the smaller ring substructures as variations in the ionospheric data.
Alongside investigating Saturn’s ionosphere, you’re also the Early Career Scientist (ECS) Representative for the Planetary and Solar System Sciences (PS) Division. Could you tell us a bit about what that involves?
Sure! As ECS reps we represent all the ECS within our respective divisions, which make up quite a large chunk of all members (~40-50%). That means partaking in regular meetings with the ECS reps of all divisions and advocating for our interests within the broader structure of EGU, organising events (such as the networking events at the GAs), and working on the division outreach (e.g. social media or blog).
Admittedly, I’m not particularly good at or well-suited for the last part, since I’ve stopped using social media a while ago. For obvious reasons I have not actually physically been to an EGU GA in Vienna, and I’m really looking forward to actually meeting the people that make up our division next year. Should be a bit more engaging than staring at a computer screen (although I liked the networking events of the past two GAs, let’s be honest – it’s just not the same). I’m hoping to persuade some fellow PS ECS over a beer or two to get involved in some capacity, such as working on a PS blog, or taking responsibility for the outreach via Twitter. There are lots of possibilities to build the PS community further and I would really like to launch (please excuse the pun) some ideas, such as a monthly planet blog.
Finally, what’s next on the horizon for yourself?
Well, in the near future it’s writing the licentiate thesis (sort of a half-time PhD thesis that one can do here in Sweden) over the next weeks and then finishing my PhD studies, of course. For next year’s EGU General Assembly I’m really looking forward to finally meeting and listening to my fellow space scientists’ presentations in person after 1.5 years of working from home. I might get to convene my first scientific session and will organise the PS ECS networking event again, so should be lots of fun!
