NASA, ESA, Amy Simon (NASA-GSFC), Michael H. Wong (UC Berkeley); Image Processing: Joseph DePasquale (STScI)

Hubble's sharp images track clouds and measure the winds, storms, and vortices, in addition to monitoring the size, shape, and behavior of the GRS. Hubble follows as the GRS continues shrinking in size and its winds are speeding up. OPAL data recently measured how often mysterious dark ovals -- visible only at ultraviolet wavelengths -- appeared in the "polar hoods" of stratospheric haze. Unlike Earth, Jupiter is only inclined three degrees on its axis (Earth is 23.5 degrees). Seasonal changes might not be expected, except that Jupiter's distance from the Sun varies by about 5% over its 12-year-long orbit, and so OPAL closely monitors the atmosphere for seasonal effects. Another Hubble advantage is that ground-based observatories can't continuously view Jupiter for two Jupiter rotations, because that adds up to 20 hours. During that time, an observatory on the ground would have gone into daytime and Jupiter would no longer be visible until the next evening.