Colloquium: Kevin Baines

Kevin Baines

Principal Scientist, NASA JPL

Abstract:  Over the past two decades, major storms on Jupiter and Saturn have been studied intensely by a number of well-instrumented orbiting and fly-by spacecraft, revealing their composition, morphology, evolution and power. In particular, high-resolution images, movies, and spectra acquired by near-infrared spectral mapping cameras on the Galileo and Cassini orbiters, and onboard the New Horizons spacecraft enroute to Pluto, have revealed the spectral identity of the primary ices that comprise the storms. These include ammonium hydrosulfide, mixtures of ammonium hydrosulfide and ammonia, and relatively pure ammonia ices found. most strongly in localized regions of powerful upwelling, including the turbulent wake of the Great Red Spot on Jupiter and in the Great Northern Storm of 2010-2011,  the largest storm yet observed on Saturn. Recent analysis of this Saturn storm finds a significant component of water ice in the cores of ammonia ice particles at the cloudtops, indicating that deeply sequestered materials such as water can be convectively lofted more than 120 km within the most colossal storms on this typically placid planet. In contrast, such tell-tale water ice has yet be found in the tops of Jupiter’s storms. On Jupiter, laboratory simulations of the ~350-year-old  Great Red Spot (GRS) indicate that the reddish color of this huge (15,000-km wide) long-lived storm can be attributed to photolytic products of ammonia and hydrocarbons  produced in the ~300-mbar cloudtops where solar UV light is relatively strong. This talk will detail such results pertaining to ice condensates and their byproducts, as well as discuss evidence for refractory materials – specifically carbon soot - generated by lightning near the 10-20-bar level of Saturn some 120 km below the visible clouds, which, in the “storm alleys” near 35 degrees latitude in both hemispheres, results in a near-constant drizzle of diamond rain some 6000-km below.