9. Jupiter: a giant primitive planet

    • All we can see on Jupiter is clouds, swept into parallel bands of bright zones and dark belts by the planetís rapid rotation and counter-flowing, east-west winds.

    • Jupiter turns to liquid under high pressures within its interior, so the cloudy atmosphere has no distinct bottom and Jupiterís weather pattern is free to flow in response to the giant planetís rapid spin.

    • Jupiterís Great Red Spot and white ovals are huge shallow anti-cyclonic storms, which can have diameters larger than the Earthís and last for centuries.

    • Large whirling storms on Jupiter gain energy by merging with, and engulfing, smaller eddies. The little storms pull their energy from hotter, lower depths.

    • White clouds of ammonia ice form in the coldest, outermost layers of Jupiterís atmosphere. Water clouds are expected to form at greater depths, and ammonium hydrosulfide clouds should condense between the water and ammonia clouds.

    • All of the clouds on Jupiter ought to be white; their colors are attributed to an active chemistry that produces complex compounds in small amounts.

    • Bolts of lightning illuminate deep, wet storm clouds on Jupiter.

    • When the Galileo spacecraft parachuted a probe into Jupiter, the entry site, a region of downdraft, was missing the expected three layers of clouds and it was far drier and windier than anticipated.

    • The fierce winds that give rise to Jupiterís banded appearance run deep, indicating that Jupiterís ever-changing weather patterns are driven mainly from within, by internal energy rather than by external sunlight.

    • When compared to the outer layers of the Sun, the outermost atmosphere of Jupiter is slightly depleted in helium, and enriched in carbon, nitrogen and sulfur by a factor of about three.

    • Jupiter is a primitive incandescent globe that radiates 1.67 times as much energy as it receives from the Sun, probably as heat leftover from when the giant planet formed.

    • Jupiter originated together with the Sun, and both the giant planet and the star are mainly composed of the lightest elements, hydrogen and helium.

    • If Jupiter was about 80 times more massive, it could have become a star.

    • Jupiter has a non-spherical shape with a perceptible bulge around its equatorial middle.

    • The visible cloud tops and outer atmosphere of Jupiter form a very thin veneer that covers a vast global sea of liquid hydrogen.

    • Most of Jupiterís interior consists of fluid metallic hydrogen formed under the extreme pressures that exist inside the planet.

    • Jupiter probably has a dense, molten core with a mass that is less than or equal to 12 times that of the Earth.

    • By re-creating extreme conditions like those inside Jupiter, modern laboratory experiments have compressed liquid hydrogen so that it becomes highly conductive like a metal.

    • Jupiterís powerful magnetic field is generated by rotationally driven electrical currents inside its vast internal shell of liquid metallic hydrogen.

    • The volcanoes on Jupiterís innermost large moon Io have turned the satellite inside out. It is the most volcanically active body in the solar system.

    • Ioís volcanoes emit plumes of sulfur dioxide gas that freeze onto the surface as a white frost.

    • Volcanic vents on Io are filled with melted silicate rocks that are hotter than any place on any planetís surface, even Venus.

    • Changing tidal forces squeeze Ioís rocky interior in and out, making it molten inside and producing volcanoes.

    • A vast current of 5 million amperes flows between the satellite Io and the poles of Jupiter, generating 2.5 trillion watts of power and producing aurora lights on both the satellite and the giant planet.

    • Jupiterís magnetic field sweeps past Io, picking up a ton of sulfur and oxygen ions every second and directing them into a doughnut shaped ring known as the plasma torus.

    • There are no mountains or valleys on the bright, smooth, ice-covered surface of Jupiterís moon Europa; it has few impact craters indicating a relatively young age.

    • Long, deep fractures run like veins through Europaís icy covering, apparently filled by the upwelling of dirty liquid water or soft ice. Warmer, slushy material just beneath the crust also lubricates large blocks of ice that float like rafts across Europaís surface.

    • An electrically conducting, subsurface sea within Europa may be responding to Jupiterís magnetic field, generating a time-varying magnetism in the satellite.

    • Scientists speculate that subsurface liquid water in Europa may harbor alien life that thrives in the dark.

    • Jupiterís moon Ganymede is bigger than the planet Mercury. The satelliteís icy surface has been fractured and pulled apart, producing a grooved terrain, and surface depressions have been filled by eruptions from volcanoes of ice.

    • Ganymede has an intrinsic magnetic field, and it is the only satellite that now generates its own magnetism.

    • Jupiterís moon Callisto has one of the oldest, most heavily cratered surfaces in the solar system. Yet, the satellite is covered by fine dark, mobile material and it has a lack of small craters when compared to the surfaces of the Moon and Mercury.

    • Like Europa, the outermost large moon Callisto has a borrowed magnetic field, apparently generated by electrical currents in a subsurface ocean as Jupiterís powerful field sweeps by. But Callisto has a largely homogeneous interior without any apparent dense iron core, and the buried sea has to lie deep enough to not affect its unaltered, cratered surface.

    • Jupiterís faint, insubstantial ring system is made of dust. The ring particles might last for only a few thousand years, and they must be replenished if the ring system is a permanent feature.

    • When interplanetary meteoroids, attracted by Jupiterís powerful gravity, pound into the small inner moons of Jupiter, they chip off dust fragments that go into orbit around the planet, forming its ring system.

    Copyright 2010, Professor Kenneth R. Lang, Tufts University