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Themisto Transparent.png
Name of satellite Themisto
Date of discovery September 30, 1975 (first)

November 21, 2000 (rediscovered)
Mass 6.9 x 10^14 kg

Themisto, also known as Jupiter XVIII, is a prograde irregular-shaped satellite belonging to the outer planet of Jupiter. First discovered in 1975 by Charles Thomas Kowal and Elizabeth Roemer, Themisto was lost in space, because there was little to no evidence that it was in fact orbiting the planet of Jupiter as a satellite, and not as a stray asteroid floating lost in deep space. This satellite was then rediscovered in the year 2000 by astronomers David C. Jewett, Yanga Roland Fernandez, and Eugene A. Magnier and was confirmed to be the same celestial body that was discovered in 1975. Themisto was not given its name, however, until October of 2002, two years after its rediscovery date. Themisto is about five miles in diameter.

Themisto is part of the Themisto group, being its own known satellite to its own group.


By the color of the satellite, it is possible Themisto is a carbanaceous, or C-type, asteroid pulled in by Jupiter's gravitational pull. This is highly possible because of its bright color spectrum it outputs to telescopes.


Themisto has a bright gray spectrum that matches those of C-type asteroids, the most populous of the asteroids in the Asteroid belt. This type of asteroid makes up three-fourths of the Asteroid belt. The surface shows numerous mountainous areas and rocky hills. There are very few craters and valleys on the surface.