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

Prior to entering Saturn’s atmosphere, the Cassini spacecraft executed a series of 22 highly inclined orbits, the Grand Finale orbits, through the previously unexplored region between Saturn and its extensive ring system. The Ion and Neutral Mass Spectrometer (INMS) aboard Cassini returned the first direct measurements of the planet’s upper atmosphere, revealing a much more chemically complex environment than previously believed. We present here an in-depth analysis of the mass spectra returned from INMS and provide further evidence of external material entering Saturn’s atmosphere from the rings. Density profiles of major and minor constituents suggest that multiple species exhibit behavior indicative of an external source, and that this external material heavily influences Saturn’s upper atmospheric composition. 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. These analyses are vital to improve our understanding of the interactions between Saturn and its rings, and the results are critical to advance photochemical modeling efforts of Saturn’s upper atmosphere.