Thebe (moon)
Stephen P. Synnott found Thebe in images from the Voyager 1 space probe taken on the 5th of March 1979. This discovery happened while the spacecraft was making its flyby of Jupiter. Before this moment, no human had ever seen the moon. It received a provisional designation after being spotted by the camera system. In 1983, officials officially named it after the mythological nymph Thebe who was a lover of Zeus. The name honored the Greek equivalent of Jupiter for the first time in official records.
Thebe orbits Jupiter at a distance of about 222,000 km relative to the planet center. Its path has an eccentricity of 0.018 and an inclination of 1.08 degrees compared to Jupiter's equator. These values are unusually high for any inner satellite orbiting the gas giant. Past gravitational interactions with Io shaped the current trajectory over millions of years. Several mean-motion resonances with Io passed through Thebe's orbit as Io gradually receded from Jupiter. These events excited Thebe's orbit into its present state near the outer edge of the gossamer ring.
Spacecraft data reveals Thebe is irregularly shaped with dimensions approximating 100 kilometers across. Its bulk density measures greater than that of Amalthea with a lower bound of 1.0 grams per cubic centimeter. More likely estimates place the density closer to 1.4 grams per cubic centimeter. The moon consists of porous water ice mixed with unknown amounts of other materials. It rotates synchronously with its orbital motion so one face always looks toward the planet. The long axis points directly at Jupiter while surface gravity remains weak enough to allow dust escape after impacts.
Zethus crater spans about 40 km in diameter and stands as the largest named feature on the moon. This massive impact basin sits on the far side facing away from Jupiter itself. Bright spots appear along the rim of this crater discovered by the Galileo spacecraft in January 2000. The surface appears dark and reddish in color under sunlight. A substantial asymmetry exists between the leading and trailing hemispheres where the front side is 1.3 times brighter than the back. At least three or four large craters exist each being roughly comparable in size to Thebe itself.
Dust ejected from Thebe's surface creates the surrounding gossamer ring through constant meteorite impacts. After ejection, particles drift inward toward the planet under Poynting, Robertson drag forces. The orbit lies near the outer edge of this dusty ring structure formed over time. Escape velocity at specific surface points allows dust to leave easily into space. High velocity impacts excavate bright material like ice from the interior of the moon. This process feeds the ring continuously while planetary gravity pulls debris closer to Jupiter.
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Common questions
Who discovered the moon Thebe and when was it found?
Stephen P. Synnott discovered the moon Thebe in images from the Voyager 1 space probe taken on the 5th of March 1979. This discovery occurred while the spacecraft was making its flyby of Jupiter before any human had ever seen the moon.
When did officials officially name the moon Thebe after a mythological figure?
Officials officially named the moon Thebe in 1983 after the mythological nymph who was a lover of Zeus. The name honored the Greek equivalent of Jupiter for the first time in official records.
What are the orbital characteristics of the moon Thebe around Jupiter?
Thebe orbits Jupiter at a distance of about 222,000 km relative to the planet center with an eccentricity of 0.018 and an inclination of 1.08 degrees compared to Jupiter's equator. Past gravitational interactions with Io shaped the current trajectory over millions of years.
How large is the Zethus crater located on the surface of the moon Thebe?
Zethus crater spans about 40 km in diameter and stands as the largest named feature on the moon Thebe. Bright spots appear along the rim of this crater discovered by the Galileo spacecraft in January 2000.
Why does dust ejected from the moon Thebe create the surrounding gossamer ring?
Dust ejected from Thebe's surface creates the surrounding gossamer ring through constant meteorite impacts that allow particles to drift inward toward the planet under Poynting Robertson drag forces. Escape velocity at specific surface points allows dust to leave easily into space while planetary gravity pulls debris closer to Jupiter.