Pioneer measured ultraviolet glow throughout the Saturnian system. This ultraviolet glow is due to the scattering of the light from the sun by atomic hydrogen. The observations of ultraviolet emission from an extensive cloud of hydrogen gas surrounding Saturn’s visible rings are especially interesting. The rings themselves are presumably the source of this hydrogen. On the planet’s disk, the ultraviolet observations show significant latitude variations, suggesting the possibility of aurora near Saturn’s polar regions. A similar extensive cloud of hydrogen was also seen partially surrounding Titan’s orbit. These very preliminary findings by Pioneer Saturn represent only a small fraction of what will ultimately be learned about Saturn and its environment as the spacecraft data are analyzed in greater detail over the weeks and months ahead. [Illustration: Schematic of the solar wind interaction with Saturn’s magnetosphere. The solar wind arrives from the direction of the sun, is deflected at Saturn’s bow shock, and flows around Saturn in the magnetosheath (orange region), as indicated by the arrows. The sizes of the magnetosheath and radiation belts change in response to the external solar-wind pressure, becoming smaller when the external pressure is larger and vice versa.] [Illustration: Diagram of Saturn’s inner trapped radiation belts. The energetic particle fluxes generally become more intense closer to Saturn. Decreases in particle flux at the locations of Saturn’s moons are due to the sweeping up of the energetic particles caused by particles striking the moons and being absorbed by them. Also, there are decreases in particle flux at the outer edge of the rings, where the energetic particles are also absorbed, so that a region free of trapped radiation is created from the outer edge of the rings to Saturn.] [Illustration: Infrared radiometer image of Saturn and its rings. Brightness in the image is related to temperature, with the brightest areas at about 100 K (about -280°F). The left version shows contrast in the colder regions (the rings). The right version shows contrast in the warmer regions (the planet). The image contains many separate scans from top to bottom. Each scan is displaced to the right from the one before by the motion of the spacecraft. The spacecraft was below the ring plane during most of the 3-hour observation period and was much closer to the planet at the end of the period (right of image) than at the start (left of image). Thus, the images are quite distorted. The small-scale pattern is instrument noise. In the left image, the warm infrared radiation from the planet is seen through Cassini’s Division between the A- and B-rings. The brightness level in the right image implies that Saturn emits heat at a rate that is 2.5 times the rate that it absorbs energy from the sun.]