User:Nicjordan009/Great Red Spot

Structure[edit] Copied from Great Red Spot - Wikipedia
Approximate size comparison of Earth and the Great Red Spot. Jupiter's Great Red Spot rotates counterclockwise, with a period of about six Earth days or fourteen Jovian days. Measuring 16,350 km (10,160 mi) in width as of 3 April 2017, Jupiter's Great Red Spot is 1.3 times the diameter of Earth. The cloud-tops of this storm are about 8 km (5.0 mi) above the surrounding cloud-tops.

Infrared data have long indicated that the Great Red Spot is colder (and thus higher in altitude) than most of the other clouds on the planet. The upper atmosphere above the storm, however, has substantially higher temperatures than the rest of the planet. Acoustic (sound) waves rising from the turbulence of the storm below have been proposed as an explanation for the heating of this region.

Careful tracking of atmospheric features revealed the Great Red Spot's counter-clockwise circulation as far back as 1966, observations dramatically confirmed by the first time-lapse movies from the Voyager fly-bys. The spot is confined by a modest eastward jet stream to its south and a very strong westward one to its north. Though winds around the edge of the spot 3 at about 432 km/h (268 mph), currents inside it seem stagnant, with little inflow or outflow. The rotation period of the spot has decreased with time, perhaps as a direct result of its steady reduction in size.

The Great Red Spot's latitude has been stable for the duration of good observational records, typically varying by about a degree. Its longitude, however, is subject to constant variation, including a 90-day longitudinal oscillation with an amplitude of ~1°. Because Jupiter does not rotate uniformly at all latitudes, astronomers have defined three different systems for defining the longitude. System II is used for latitudes of more than 10 degrees and was originally based on the average rotational period of the Great Red Spot of 9h 55m 42s. Despite this, however, the spot has "lapped" the planet in System II at least 10 times since the early nineteenth century. Its drift rate has changed dramatically over the years and has been linked to the brightness of the South Equatorial Belt and the presence or absence of a South Tropical Disturbance.

Internal Depth and Structure
Jupiter's Great Red Spot is an elliptical shaped anticyclone, occurring at 22 degrees below the equator, in Jupiter's southern hemisphere. As the largest anticyclonic storm (~16,000 Km) in our solar system, little is known about the internal depth and structure of Jupiter's Great Red Spot (GRS). Visible imaging and cloud-tracking from in-situ observation determined the velocity and vorticity of the GRS which is located in a thin anticyclonic ring at 70–85% of the radius and is located along Jupitar's fastest westward moving jet stream. During NASA's, 2016 Juno mission, gravity signature and thermal infrared data was obtained that offered insight into the structural dynamics and depth of the GRS. During July of 2017, the Juno spacecraft conducted a second pass of the GRS to collect Microwave Radiometer (MWR) scans of the GRS to determine how far the GRS extended toward the surface of the condensed H2O layer. These MRW scans suggested that the GRS vertical depth extended to about ~240 Km below the cloud level, with an estimated drop in atmospheric pressure to 100-bar. Two methods of analysis that constrain the data collected were the Mascon approach which found an depth of ~290 Km., and the Slepian approach showing wind extending to ~310 Km. These methods, along with gravity signature MWR data suggest that the GRS zonal winds still increase at a rate of 50% the velocity of the viable cloud level, before the wind decay starts at lower levels, this rate of wind decay and Gravity data suggest the depth of the GRS is between 200 and 500 Km.

Galileo and Cassini's thermal infrared imaging and spectroscopy were conducted of the GRS during 1995 - 2008, in order to find evidence of thermal inhomogeneities with in the internal structure vortex of the GRS. Previous thermal infrared temperature maps from the Voyager, Galileo, and Cassini missions; suggested the GRS is a cold-core within a upwelling warmer annulus structure of an anticyclonic vortex, this data shows a gradient in the temperature of the GRS. To gain better understanding of Jupiter’s atmospheric temperature, aerosol particle opacity, and ammonia gas composition from thermal-IR imaging, a direct correlation of the visible-cloud layers reactions, thermal gradient and compositional mapping to observational data collected over decades. During December 2000, high spatial resolution images from Galileo, of an atmospheric turbulent area to the northwest of the GSR, shows a thermal contrast between the warmest region of the anticyclone with regions to the east and west of the GRS. The vertical temperature of the structure of the GRS is constrained between the 100–600 mbar range, with the vertical temperature of the GSR core is approximately 400 mbar of pressure, being 1.0–1.5 K much warmer than regions of the GRS to the east–west, and 3.0–3.5 K warmer than regions to the north–south of the structures edge. This structure is consistent with the data collected by the VISIR (VLT Mid-Infrared Imager Spectrometer on the ESO Very Large Telescope) imaging obtain in 2006, this data revealed that the GSR was physically present in a wide range of altitudes that occur within the 80 - 600 mbar pressure of the atmosphere and confirmers the thermal infrared mapping result. To develop a model of the internal structure of the GRS the Cassini mission Composite Infrared Spectrometer (CIRS) and ground based spatial imaging mapped the composition of the Phosphine and ammonia aerosols (PH3, NH3 and para-H2) within the anticyclonic circulation of the GRS. The imaging that was collected form the CIRS and ground-based imaging trace the vertical motion in the Jovian atmosphere by PH3 and NH3 spectra. The highest concentrations of PH3 and NH3 are found to the north of the GRS peripheral rotation and aided in determine the southward jet movement and shows data of an increase in altitude of the column of aerosols with ranging pressures of 200–500 mbar. However, the NH3 composition data shows that there is a major depletion of NH3 below the visible cloud layer at the southern peripheral ring of the GRS, this lower opacity is relative to a narrow band of atmospheric subsidence. The low mid-IR aerosol opacity along with; the temperature gradients, the altitude difference, and the vertical movement of the zonal winds are involved with the development and sustainability of the vorticity. The stronger atmospheric subsidence and compositional asymmetries of the GRS suggest that the structure exhibits a degree of tilt form the northern edge to the southern edge of the structure. The GSR depth and internal structure has been constant with changes over decades however there is still no logical reason why it is ~200 - 500 km in depth, but the jet streams that supply the force that powers the GRS vortex are well below the structure base.