A liquid-giant planet whose atmosphere is composed of hydrogen and helium, with methane, ammonia, H₂S, and water as condensable aerosols. These gases interact in complex ways to produce rotating horizontal bands and spinning cyclones (such as the Great Red Spot). The Red Spot is discussed in the Oct. 1990 Sky & Telescope, pp. 359-364. It has a rotational period of days. In order of decreasing condensation height (as well as saturation vapor pressure), the condensable gases are CH₄, NH₃, NH₄SH (NH₃H₂S), and H₂O. Below Jupiter's 150 km thick gaseous atmosphere, layers of liquid hydrogen and liquid metallic hydrogen are thought to be present, followed by a rocky core. The central pressure of Jupiter is Mbar. Jupiter has a magnetic field 10 times as strong as Earths and a small ringlet discovered by Voyager 1. Jupiter also emits 1.7 as much radiation as it receives from the sun. In addition, it emits sporadic bursts of non-thermal radio noise at 22.2 MHz (decametric), in addition to a constant non-thermal emission at 300-3000 MHz (decimetric).

The Great Red Spot is an anticyclonic storm which rotates with a period of 10 hours. The red coloration could be caused by photochemical products of sulfur of phosphorus compounds. However, no enrichment of phosphine is seen in the GRS, making phosphorus compounds unlikely chromophores. Jupiter's South Equatorial Belt vanished in early 1989, but reappeared when Jupiter emerged from behind the Sun in 1990. Jupiter is at its brightest as seen from earth every 23 years (last peak in 1987).

The rings of Jupiter are designated halo, main, and gossamer. Jupiter's four largest (Galilean) satellites, Callisto, Ganymede, Europa, and Io can be seen easily through a telescope. From innermost to outermost, Jupiter's moons are (1) Metis, (2) Adrastea, (3) Amalthea, (4) Thebe, (5) Io, (6) Europa, (7) Ganymede, (8) Callisto, (9) Leda, (10) Himalia, (11) Lysithea, (12) Elara, (13) Ananke, (14) Carme, (15) Pasiphae, and (16) Sinope.