Jupiter's smallest moon barely 2km wide: Scientists

The moon, known as S/2010 J 2, was discovered along with a fellow shrimpy satellite called S/2010 J 1 in 2010. After almost two years of observation, scientists have found that S/2010 J 2 has a diameter of about 1.2 miles (2km), while S/2010 J 1 is about 1.8 miles (3km) wide.

Their discovery brought the number of documented Jovian moons to 67, the researchers said.

"It was exciting to realise that this [S/2010 J 2] is the smallest moon in the solar system that was discovered and tracked from Earth," study co-author Mark Alexandersen of the University of British Columbia was quoted as saying by SPACE.Com.

According to the newly found details, S/2010 J 1 circles Jupiter at an average distance of 14.57 million miles (23.45 million km), taking 2.02 years to complete a lap around the solar system's largest planet. But, S/2010 J 2 takes 1.69 years to zip around Jupiter, and its average distance is 13.06 million miles (21.01 million km).

The new observations also confirmed that the diminutive dimensions of the two satellites, which researchers determined based on their brightness. S/2010 J 1 appears to belong to the Carme family, while S/2010 J 2 is likely a member of the Ananke group, researchers said.

Jupiter is surrounded by a veritable cloud of moons, with about 50 primary moons that have official names and at least 14 smaller provisional moons that are known only by their number, according to a NASA description.

Scientists group the smaller, irregular satellites of giant planets such as Jupiter and Saturn in families with similar orbits and colours. These various families are believed to have formed when comets or asteroids smashed into larger moons long ago.

Jupiter's moons are a very diverse group, ranging from the tiny, irregularly shaped S/2010 J 1 and S/2010 J 2 to the huge Galilean satellites Io, Europa, Callisto and Ganymede. With a diameter of 3,273 miles (5,268 km), Ganymede is the biggest moon in the solar system.

The new findings will appear in The Astronomical Journal.