Oak Ridge National Laboratory

Physics Division

Physics Division Seminars

Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,

Alfredo Galindo-Uribarri
Tel (Office): (865) 574-6124  (FAX): (865) 574-1268


Thu., April 25, 2019, at 3:00-4:00

Saturnian ring-atmosphere connection and the Cassini final plunge

Oliver Hamil
Georgia Institute of Technology, Atlanta

Saturn’s rings are mainly composed of water ice clusters ranging in size from roughly 0.01 cm up to 10 m across. When smaller ice particles become charged through various methods, they can escape the ring plane, travel along magnetic field lines and fall into the upper atmosphere. This so called “ring rain” is thought to explain low electron density observations due to charge exchange between the in-falling water molecules and the upper ionosphere. For the first time, in-situ measurements of ring material impacting the upper atmosphere have been taken by NASA’s Cassini spacecraft during the final days of its 19-year mission, when its orbit plunged between Saturn’s innermost ring and upper atmosphere. The resulting data have led to exciting new discoveries regarding the ring-atmosphere connection and have opened new questions regarding the composition and lifetime of Saturn’s ring system. Instruments aboard Cassini not only recorded a large flux of in-falling ring material, but also observed, in the mass spectrum, ion and neutral species (such as methane) in unexpectedly large abundance. I will give a brief overview of the interaction between Saturn’s rings and its upper atmosphere in the context of in-falling ice-grains and the exciting new data provided by Cassini during its final plunge.