On the structure and motions of Jupiter's red spot

Abstract

Abstract A new hypothesis-called the Cartesian diver hypothesis-is proposed to explain the physical nature and observed variations in longitude, size and intensity of Jupiter's Great Red Spot. In the light of recent laboratory studies of phase behavior in light gas mixtures, it is suggested that the Red Spot is a region of contrast in the cloud structure of Jupiter's outer layers, caused by the presence of a mass of hydrogen-rich solid floating within a fluid layer of hydrogen and helium at some depth below the visible surface. It is shown that this floating solid would exhibit many of the characteristics of a Cartesian diver. Equations of motion for a Cartesian diver in a rotating system are derived, which suggest that the longitudinal motion of the Red Spot consists of several oscillatory components of different amplitudes and frequencies. These predictions are in agreement with motions determined from recent precise measurements of Red Spot longitude. Mechanisms for the source of the observed oscillations are discussed, and estimates are made of the extent of the underlying vertical motions. Effects of the rapid rotation of the planet upon the dynamic behavior of the fluid in the vicinity of the Cartesian diver are qualitatively included, and the resulting physical model is used to explain not only the observed variations of size and intensity of the Red Spot, but also the manner in which these variations correlate with changes in longitude. Laboratory studies and further observations designed to assist in verifying the Cartesian diver hypothesis are suggested.