Carpo was discovered on Feb. 26, 2003 by Scott S. Sheppard and others from the University of Hawaii's Institute for Astronomy using the 12-ft. (3.6-m) Canada-France-Hawaii telescope at the Mauna Kea Observatory in Hawaii.
Carpo, some 1.9 miles (3 km) across (assuming an albedo of 0.04), orbits Jupiter at a distance of about 10.5 million miles (17 million km). It takes a little over 456 Earth days to complete one orbit.
The orbit is somewhat inclined with respect to Jupiter's equatorial plane, and the direction of travel is the same as that of Jupiter's rotation (a "prograde" orbit). It is Jupiter's most distant known moon with a prograde orbit. There are many moons known to be further out, but they all travel around Jupiter in the opposite direction.
Originally designated S/2003 J20, Carpo was named for one of the three Athenian goddesses of the flowers of spring and the fruits of summer and autumn. An annual festival in their honor was called the Horaea. According to Hesoid, a group of goddesses collectively called the Horae (with different names, which did not include Carpo) were daughters of Zeus, the Greek equivalent of the Roman god Jupiter.