Carme is one of the largest irregular satellites of Jupiter.
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Discovery and naming
It was discovered by Seth Barnes Nicholson at Mount Wilson Observatory in California in July 1938.
It is named after the mythological Carme, mother by Zeus of Britomartis, a Cretan goddess. Carme did not receive its present name until 1975; before then, it was simply known as Jupiter XI. It was sometimes called "Pan" between 1955 and 1975 (Pan is now the name of a satellite of Saturn).
Orbit
Carme orbits Jupiter at an average distance of 22,579,859 km in 693.17 days, at an inclination of 165° to the ecliptic, in a retrograde direction and with an eccentricity of 0.23. They are continuously changing due to solar and planetary perturbations.
It gives its name to the Carme group, made up of retrograde irregular moons orbiting Jupiter at distances ranging between 22.7–23.5 million km, at an inclination of about 165°, and eccentricities between 0.24 and 0.28.
Physical characteristics
With a diameter of 46.7±0.9 km (albedo 3.5%), it is the largest member of the Carme group and the fourth-largest irregular moon of Jupiter.
Like the other members of the Carme group (except for Kalyke) it is light red in color (B−V=0.76, V−R=0.47), similar to D-type asteroids.
Carme's spectral shape and absorption features are special and make it unique compared to other satellites. It has a strong upturn in the ultraviolet range with a CN emission at 0.388 μm, possibly indicative of low-level cometary activity. One study found that modelling its surface composition as 4% low-Fe serpentine and 96% kerogen provided a good match. Another study suggested it was composed mainly of amorphous carbon, minnesotaite, and ilmenite.
The rotation period was found to be approximately 10 hours and 24 min. This was regarded by a later paper as uncertain due to the short observation periods. Another group found a different possible rotation period of 6.48 hours.
Origin
Carme probably did not form near Jupiter but was captured by Jupiter later. Like the other members of the Carme group, which have similar orbits, Carme is probably the remnant of a broken, captured heliocentric asteroid.