Using data from the Cassini spacecraft, a researcher has ingeniously determined the optical depth of Saturn’s rings, offering fresh perspectives on their clarity and composition. (Depiction of NASA’s Cassini spacecraft orbiting Saturn.) Courtesy: NASA/JPL-Caltech
At Lancaster University, a doctoral candidate has utilized a novel approach to measure the optical depth of Saturn’s rings, based on the amount of sunlight reaching the Cassini spacecraft during its eclipse by the rings.
Optical depth relates to an object’s clarity, indicating the distance light can penetrate it before being absorbed or scattered.
Cassini Mission and Collaborative Research
This study, spearheaded by Lancaster University in partnership with the Swedish Institute of Space Physics, was published in the Monthly Notices of the Royal Astronomical Society.
Launched in 1997 and arriving at Saturn in 2004, the NASA-ESA Cassini spacecraft conducted the most comprehensive exploration of Saturn and its moons ever undertaken. The mission concluded in 2017, with Cassini descending into Saturn’s atmosphere after 22 orbits between the planet and its rings.
A video by George Xystouris using NASA Eyes, showing the Cassini spacecraft navigating Saturn’s ring plane. Credit: NASA/JPL
Research Methodology and Discoveries
George Xystouris, a PhD student at Lancaster University under Dr. Chris Arridge’s guidance, scrutinized historical data from Cassini’s Langmuir Probe. This instrument measured Saturn’s magnetosphere’s cold plasma, consisting of low-energy ions and electrons.
Their research focused on solar eclipses experienced by the spacecraft, when Cassini was obscured by Saturn or its primary rings. The Langmuir Probe recorded significant data fluctuations during these eclipses.
George explained: “The probe, being metallic, releases electrons due to sunlight’s energy – a phenomenon known as the photoelectric effect. These released electrons, or ‘photoelectrons,’ pose challenges as they share properties with Saturn’s surrounding cold plasma electrons, making differentiation difficult.”
“By analyzing data variations, we deduced their link to the sunlight penetration through each ring. Ultimately, by understanding the Langmuir Probe’s material properties and the Sun’s brightness near Saturn, we were able to assess the photoelectron count change for each ring and determine Saturn’s rings’ optical depth.
“This innovative finding is significant. We repurposed a plasma-measuring instrument to assess a planetary characteristic, an unprecedented use of the Langmuir Probe, aligning with studies using high-resolution imagers to assess the rings’ transparency.”
Future Observability of Saturn’s Rings
Saturn’s main rings, spanning up to 140,000 km (90,000 miles) from the planet yet only 1 km (0.6 miles) thick, will become invisible from Earth by 2025. At that time, the rings’ edge-on alignment to Earth will render them nearly unobservable. They will reorient towards Earth during Saturn’s subsequent 29-year orbital phase, progressively becoming more visible and luminous until 2032.
Professor Mike Edmunds, President of the Royal Astronomical Society, remarked: “It’s gratifying to see a postgraduate student creatively and uniquely utilize space probe instruments. Such innovative methods are crucial in astronomical research and are being applied by many former students across various fields to address global challenges.”
Citation: “Estimating the optical depth of Saturn’s main rings using the Cassini Langmuir Probe” by Georgios Xystouris, Christopher S Arridge, Michiko M Morooka, and Jan-Erik Wahlund, 18 September 2023, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stad2793
Table of Contents
Frequently Asked Questions (FAQs) about Cassini Saturn research
What is the main focus of this research?
The main focus of this research is to measure the optical depth of Saturn’s rings using data from the Cassini spacecraft and gain insights into their transparency and structure.
How was the optical depth of Saturn’s rings measured?
The optical depth was determined by analyzing how much sunlight reached the Cassini spacecraft during solar eclipses when it was in the shadow of Saturn or its main rings. This data was collected using the Langmuir Probe onboard Cassini.
What is optical depth, and why is it important?
Optical depth is a measure of how transparent an object is and indicates how far light can travel through it before being absorbed or scattered. It’s important because it provides valuable information about the composition and clarity of Saturn’s rings.
Who conducted this research, and where was it published?
The research was led by a Lancaster University PhD student named George Xystouris, in collaboration with the Swedish Institute of Space Physics. The findings were published in the Monthly Notices of the Royal Astronomical Society.
What is the significance of repurposing the Langmuir Probe for this study?
Repurposing the Langmuir Probe for this study is significant because it allowed researchers to use an instrument primarily designed for plasma measurements to assess a planetary feature. This innovative approach provided unique insights into Saturn’s rings.
What does the future hold for the visibility of Saturn’s rings from Earth?
Saturn’s main rings, currently visible, will become almost invisible from Earth by 2025 when they align edge-on to our planet. However, they will gradually become more visible and brighter as they reorient towards Earth in the following years, with the best visibility expected around 2032.
How does this research contribute to our understanding of Saturn’s rings?
This research contributes to our understanding of Saturn’s rings by providing a novel method for measuring their optical depth and, consequently, their transparency. It adds valuable data to our knowledge of the composition and behavior of these iconic planetary rings.
More about Cassini Saturn research
- Monthly Notices of the Royal Astronomical Society
- Cassini-Huygens Mission Overview
- Lancaster University
- Swedish Institute of Space Physics
- NASA’s Cassini-Huygens Mission to Saturn and Titan
3 comments
cool stuff abt Saturn’s rings. dude measured it w/ Cassini!
Cassini did so much, diving into Saturn ‘n all. Nice info!
Langmuir Probe, that’s a word. Impressive they reused it for rings!