Io is asteroid #85 and of the type C. Io is an interloper in the asteroid-family Eunomia. Io’s orbit is characterized by a semi-major axis of 2.65 Astronomical Units, an eccentricity of 0.19, a period of revolution of 1 578 days, and an inclination of twelve degrees. Io was discovered by the German-American astronomer Christian Heinrich Friedrich Peters. Io has the shortest designations among all asteroids because Io only is referred to by a two-digit number and a two-letter name.

Io also is the name of Jupiter I, the third-largest natural satellite of Jupiter and the fourth-largest moon of the whole Solar System. Jupiter I is the innermost of the four Galilean moons. This Io is almost free of water and has an average temperature of -143°C. This Io nevertheless is the celestial body with the most active volcanism in the whole Solar System and this volcanism reveals that Io, at least Io’s crust and Io’s thin atmosphere, mainly consists of sulfur.

Both celestial bodies are named after Iṓ (Ἰώ) from Greek mythology. She is a mortal lover of Zeus. Iṓ (Ἰώ) is the daughter of the Okeanid Melía (Μελία) and the river god Ínachos (Ἴναχος), who shall have been the first king of the city of Argos. Iṓ (Ἰώ) has at least two brothers. Their names are Aigialeús (Αἰγιαλεύς) and Phorōneús (Φορωνεύς). Iṓ (Ἰώ) was a priestess of Hera, due to a personal wish of Hera. Iṓ (Ἰώ) someday had a dream, that told her that Zeus lusted for her. So Ínachos (Ἴναχος) asked an oracle for advice, but the oracle knew only that Ínachos (Ἴναχος) should cut ties to Iṓ (Ἰώ). He did this and so Zeus got his chance. He turned Iṓ (Ἰώ) into a white cow in order to hide her from Hera. But she discovered the ruse, perhaps because she keeps an eye on her priestesses. Hera demanded from Zeus to get the white cow as a gift and Zeus agreed to this, probably because he didn’t want to seem suspicious. Hera gave the white cow to the hundred-eyed giant Árgos (Ἄργος), who should guard the white cow. Zeus then sent out his messenger Hermes to kill Árgos (Ἄργος) and Hermes fulfilled this mission. Hera sent a gadfly after Iṓ (Ἰώ). Gadflies are dangerous for cattle, so Iṓ (Ἰώ) fled. She crossed a sea, that later was named the Ionian Sea after her. Iṓ (Ἰώ) also crossed a ford and this ford later was called the Bosporus Strait, from Ancient Greek bosporos (Βόσπορος), which means cattle ford. Iṓ (Ἰώ) fled until she reached the river Nile and there she somehow got her human shape back and then gave birth to Épaphos (Ἔπαφος), who became king of Egypt and is described as black in skin color. Ovid twists the tale and makes Iṓ (Ἰώ) raped by Zeus. Herodotus explains that Iṓ (Ἰώ) was abducted by the Phoenicians and this led to a series of mutual abductions of women, which peaked in the Trojan War. Herodotus probably tries to find a historical core of the tale of Iṓ (Ἰώ) this way. But the tale of Ínachos (Ἴναχος) continues. He mourned the loss of his daughter. Eris then visited Ínachos (Ἴναχος) and told him that he can get his daughter back if he cursed his own descendants. Ínachos (Ἴναχος) agreed to curse his five generations later descendants after Eris put clear that he doesn’t know anything about them anyway. The curse angered Zeus, so he sent Tisiphone (Τισιφόνη) after the river god and Ínachos (Ἴναχος) dried up.

Iṓ (Ἰώ) seems to exist only in order to connect tales of mythology with some historical persons and places and to explain some place names. So Io should represent giving names. Not calling names, but things like naming ceremonies or folk etymology.

The asteroid Echo had to be renamed because Uranus III already was named Titania. Any astronomer not knowing the name of Jupiter I is completely impossible. The asteroid Io nevertheless has been treated differently from Echo and could keep her name. So Io also represents mistakes, which don’t get corrected albeit noticed.