Southwest Research Institute scientists have compiled 41 solar occultation observations of Saturn’s rings from the Cassini mission. The compilation, published recently in the scientific journal Icarus, will inform future investigations of the particle size distribution and composition of Saturn’s rings, key elements to understanding their formation and evolution.
“For nearly two decades, NASA’s Cassini
spacecraft shared the wonders of Saturn and its family of icy moons and
signature rings, but we still don’t definitively know the origins of the ring
system,” said Dr. Stephanie Jarmak, a researcher in the SwRI Space Science
Division. “Evidence indicates that the rings are relatively young and could
have formed from the destruction of an icy satellite or a comet. However, to
support any one origin theory, we need to have a good idea of the size of
particles making up the rings.”
Cassini’s Ultraviolet Imaging
Spectrograph (UVIS) was uniquely sensitive to some of the smallest ring
particles, particularly with the observations it made in the extreme
ultraviolet wavelength.
To determine the size of the ring
particles, UVIS observed them when the instrument was pointed at the Sun,
looking through the rings in what is known as a solar occultation. Ring
particles partially blocked the path of the light, providing a direct
measurement of the optical depth, a key parameter for determining the size and
composition of the ring particles.
“Given the wavelength of the light
coming from the Sun, these observations gave us insight into the smallest
particle sizes with Saturn’s rings,” Jarmak said. “UVIS can detect dust
particles at the micron level, helping us understand the origin, collisional
activity and destruction of the ring particles within the system.”
The compilation also delves into the
variations in the optical depth of occultation observations, which can help
determine particle size and composition. During an occultation, light emitted
by a background source, such as the Sun, is absorbed and scattered by the
particles in the light’s path. The amount of light blocked by ring particles
provides a direct measurement of the ring optical depth.
Including optical depth is vital to
understanding the structure of the rings. The research measured the optical
depth as a function of the viewing geometry, which refers to the observation
angles of the ring system with respect to the Cassini spacecraft. As light
passing through the rings changes at various angles, scientists can form a
picture of the rings’ structures.
“Ring systems around giant planets also provide test beds for investigating fundamental physical properties and processes in our solar system in general,” Jarmak said. “These particles are thought to result from objects colliding and forming in a disk and building up larger particles. Understanding how they form these ring systems could help us understand how planets form as well.”
Journal article: https://www.sciencedirect.com/science/article/abs/pii/S001910352200330X?via%3Dihub
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