How did you get into planetary science?
I’d been interested in space exploration since childhood, watching with awe as the space shuttle completed its missions and Hubble delivered stunning views of the universe. But when I went off to university in 2000, solar system studies weren’t really on my radar: I was set on studying physics and maths, and all my physicist friends were getting excited about cosmology and particle physics. But the more I looked into those fields, I realised I wanted to study something more tangible - something closer to home, something we could see with our own eyes, something that we might one day be able to reach out and touch. After a course in geophysics at Cambridge, I started to look into planetary science opportunities at PhD in 2003.
20 yrs apart: the @AstronomyNow I bought as a school kid excited about @CassiniSaturn, and the @AstronGeo I helped write on its discoveries pic.twitter.com/UBmrZ8QAEC— Leigh Fletcher (@LeighFletcher) August 25, 2017
How did you get involved in Cassini research? When was that?
It turned out to be the perfect moment to start looking at PhD opportunities in planetary science in the UK. Cassini was just months away from Saturn Orbit Insertion, and the UK teams involved in the mission were advertising a number of opportunities. I was interviewed for positions to study magnetic fields and plasma science, but I ultimately settled on a PhD in planetary atmospheres at the University of Oxford. Oxford had provided hardware (focal plane assemblies and a cooler) to the Composite Infrared Spectrometer (CIRS) instrument, led by Goddard Spaceflight Center. CIRS measures thermal radiation from planetary atmospheres, rings and satellite surfaces, and the Oxford team were looking for PhD candidates to analyse Saturn and Titan observations from those preliminary Cassini orbits. I was offered the place in 2004, completed my degree in the summer and waited with baited breath to see if Cassini would survive that first ring-plane crossing. I then arrived in Oxford in October 2004, ready to roll up my sleeves and start analysing CIRS data - that formed the basis of my doctoral thesis in 2007, Saturn’s Atmosphere: Structure and Composition from Cassini/CIRS. It’s safe to say that I wouldn’t be where I am today if not for that opportunity to work with the Cassini team from the start of the Saturn mission.
Are you still working with Cassini data, and if so, what mysteries still exist about Saturn, its moons, etc?
Absolutely! CIRS has now been observing Saturn for 13 years, almost spanning from solstice to solstice, providing us with the best chance of characterising a seasonal giant planet. I’m still tracking the evolution of temperature, cloud and compositional changes arising from both slow seasonal variations and short-term outbreaks of storm activity on the gas giant. Cassini has revealed Saturn’s atmosphere to be deeply interconnected, with activity in vastly separated regions having substantial consequences elsewhere - for example, the deep roiling tropospheric storm of 2011 had substantial side-effects in the stratosphere and possibly even the ionosphere. We’re still trying to understand what connects different regions of Saturn’s atmosphere, and what deep processes, hidden well below the clouds, are responsible for the timescales and violence of the massive outbreaks that we see.
Will you be able to continue using Cassini data after the mission ends?
We’ll be trying to provide a complete 13-year temperature, composition and aerosol dataset that spans the entire mission, as a resource for future researchers studying atmospheric processes on giant planets. So I’m sure I’ll be delving into the CIRS dataset for many years to come.
How has Cassini changed the way that scientists understand your particular research/field?
I think I answered this one above, when I spoke about Saturn’s atmosphere being deeply interconnected. But beyond that, I think we’ve started to show that ideas inherited from the study of terrestrial meteorology and climatology (jet streams, Hadley circulations, moist convective storms and lightning, polar vortices, equatorial oscillations) can be applied to gas giant atmospheres, despite the vastly different environmental conditions. It’s showing that a number of atmospheric processes are commonplace across vastly different worlds.
What kinds of feelings do you have now that Cassini is ending?
T-minus 2 weeks until @CassiniSaturn's demise. Are you crying? We're crying. https://t.co/BvSxYfgZmo— AGU's Eos (@AGU_Eos) September 1, 2017
Pride in what we’ve accomplished; gratitude that I was offered a chance to become involved; and sadness that a team I’ve worked with for 13 years will now be moving on to pastures new. Whenever I watch the CGI movie of Cassini’s final demise, it’s hard not to feel moved. If you forget all the exciting science, Cassini is an incredible testament to spacecraft engineering and operations, having worked so well for so long. Cassini is the best example of US-European collaboration that i know of, and it’s hard to imagine that we’ll ever have another spacecraft like it. That said, just think what we might accomplish with Cassini-style exploration of the next two great outposts in our solar system: Uranus and Neptune? I hope that I’ll be able to offer new PhD candidates the opportunity to study data from robotic explorers of the ice giants, some day!
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