Compositional Measurements of Saturn's Upper Atmosphere and Rings from Cassini INMS.

The Cassini spacecraft's last orbits directly sampled Saturn's thermosphere and revealed a much more chemically complex environment than previously believed. Observations from the Ion and Neutral Mass Spectrometer (INMS) aboard Cassini provided compositional measurements of this region and found an influx of material raining into Saturn's upper atmosphere from the rings. We present here an in‐depth analysis of the CH4, H2O, and NH3 signal from INMS and provide further evidence of external material entering Saturn's atmosphere from the rings. We use a new mass spectral deconvolution algorithm to determine the amount of each species observed in the spectrum and use these values to determine the influx and mass deposition rate for these species. Plain Language Summary: The Cassini spacecraft's last orbits around Saturn provided measurements to help us understand how the rings of Saturn interact with its upper atmosphere. Using measurements from the mass spectrometer aboard the spacecraft, we find that a lot of material from the rings is entering Saturn's atmosphere. We use a new method to determine the amount of water, methane, and ammonia that are entering the atmosphere from the rings and find that this large influx could deplete the ring system in a relatively short amount of time. Key Points: We measure the density profiles of H2, He, CH4, H2O, and NH3 in Saturn's thermosphere from Cassini INMSWe use a new mass spectral deconvolution algorithm to determine the relative abundances of different species found in the mass spectraWe report further evidence of CH4, H2O, and NH3 entering Saturn's atmosphere from the rings at a rate of at least 103 kg/s [ABSTRACT FROM AUTHOR]